Solder bump forming member, method for manufacturing solder bump forming member, and method for manufacturing electrode substrate with solder bump

Abstract

To provide a solder bump forming member useful for manufacturing a connection structure with both excellent insulation reliability and conduction reliability, even if the connection points of circuit members to be electrically connected to each other are minute.SOLUTION: A solder bump forming member has a base substance with a plurality of recesses, and solder particles and fluidizing agent in the recess, the average size of solder particles is from 1 to 35 μm, and the C.V. value is equal to or less than 20%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a member for forming solder bumps, a method for manufacturing a member for forming solder bumps, and a method for manufacturing an electrode substrate with solder bumps.

Background Art

[0002] A solder ball arrangement sheet is known, which is composed of a mask provided with a plurality of solder ball insertion holes provided in a predetermined pattern, solder balls accommodated in the insertion holes, and an adhesive for holding the solder balls in the insertion holes (see, for example, Patent Document 1).

[0003] A method for manufacturing a sheet for forming solder bumps, which holds solder balls or solder powder at a predetermined position and includes the following steps, is known (see, for example, Patent Document 2). A. Prepare a sheet having a large number of depressions on one side, the bottom surface of which is composed of an adhesive, at predetermined positions; B. Fill each depression of the sheet with solder powder and adhere and hold the solder powder by the adhesive on the bottom surface of the depression; C. Remove the solder powder not held by the adhesive from the sheet, and D. Coat the solder powder in the depressions of the sheet.

[0004] A method is known in which solder balls arranged in a concave groove are transferred to the surface of an adhesive roll, and then the solder balls are transferred to an adhesive on an electrode to form solder bumps on the electrode (see, for example, Patent Document 3).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the transfer sheet and manufacturing method shown in Patent Documents 1 and 2, an adhesive layer for holding solder particles is required. Therefore, when heated above the solder melting point to melt and unite the solder and further heated during transfer onto the electrode, the adhesive layer components may soften, melt, and decompose to become contaminants. If contaminants intervene between the solder and the electrode, there is a risk of preventing the stable formation of solder bumps. When removing these contaminants after transferring the solder bumps onto the electrode, the substrate and semiconductor package on which the electrodes are formed are exposed to a cleaning liquid, which may cause an increase in the number of processes, defects in the substrate and semiconductor package, and defects due to poor cleaning.

[0007] In Patent Document 3, since solder balls (particles) are placed on the electrode via an adhesive, there is a risk that the adhesive components remain on the surface of the solder balls and cause problems in bonding. Also, controlling the thickness of the adhesive and the unevenness of the adhesive surface is possible to some extent when the size of the solder balls is about 100 μm, but it becomes difficult as the size decreases to 50 μm and 30 μm. Therefore, when transferring and moving solder balls (particles) smaller than 30 μm via an adhesive, it becomes difficult to increase the transfer rate.

[0008] In addition, there is known a transfer sheet in which solder balls (particles) are uniformly arranged on the surface of a base material via an adhesive while being in contact with each other. By pressing the solder ball surface of this transfer sheet against a substrate on which electrodes are formed and heating it, it is said that solder balls can be transferred onto the electrodes, and bumps can be formed by subsequent reflow. However, as a result of investigations by the inventors, when the electrode pitch becomes narrow, solder bridges between the electrodes, resulting in a short-circuit failure. Since adjacent solder balls are in contact with each other, it is presumed that due to the heat during transfer to the electrodes, the solder melts and coalesces, creating a portion that spans between adjacent electrodes. In such a solder transfer sheet in which solder particles are uniformly arranged while being in contact with each other, it is currently difficult to form solder bumps without short-circuiting when the electrode pitch is at the micron level.

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide a member for forming solder bumps and a method for manufacturing the same, which are useful for manufacturing a connection structure excellent in both insulation reliability and conduction reliability even when the connection portions of circuit members to be electrically connected to each other are minute. Another object of the present invention is to provide a method for manufacturing an electrode substrate with solder bumps using the member.

Means for Solving the Problems

[0010] One aspect of the present invention relates to a member for forming solder bumps, comprising a substrate having a plurality of recesses, and solder particles and a fluidizing agent in the recesses, wherein the average particle diameter of the solder particles is 1 to 35 μm and the C.V. value is 20% or less.

[0011] The above member for forming solder bumps is useful for manufacturing a connection structure excellent in both insulation reliability and conduction reliability even when the connection portions of circuit members to be electrically connected to each other are minute.

[0012] In one aspect of the solder bump forming member, the fluidizing agent may contain at least one selected from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, benzoic acid, and malic acid.

[0013] In one aspect of the solder bump forming member, a flat portion may be formed on a part of the surface of the solder particles.

[0014] In one aspect of the solder bump forming member, the distance between adjacent recesses may be 0.1 times or more the average particle diameter of the solder particles.

[0015] One aspect of the present invention relates to a method for manufacturing a solder bump forming member, which includes a pre-step of preparing a substrate having a plurality of recesses, solder particles, and a fluidizing agent, and an arranging step of arranging the solder particles and the fluidizing agent in the recesses.

[0016] One aspect of the present invention relates to a method for manufacturing a solder bump forming member, which includes a preparation step of preparing a substrate having a plurality of recesses and fine solder particles, a housing step of housing at least a part of the fine solder particles in the recesses, a fusing step of fusing the fine solder particles housed in the recesses to form solder particles in the recesses, and an injection step of arranging a fluidizing agent in the recesses in which the solder particles are formed.

[0017] In one aspect of the method for manufacturing a solder bump forming member, the average particle diameter of the solder particles may be 1 to 35 μm and the C.V. value may be 20% or less.

[0018] In one aspect of the method for manufacturing a solder bump forming member, the C.V. value of the fine solder particles may exceed 20%.

[0019] One aspect of the method for manufacturing a solder bump forming member may further include a reducing step of exposing the fine solder particles housed in the recesses to a reducing atmosphere before the fusing step.

[0020] In one aspect of the method for manufacturing a solder bump forming member, in the fusion step, the solder fine particles may be fused in a reducing atmosphere.

[0021] One aspect of the present invention relates to a method for manufacturing an electrode substrate with solder bumps, including a preparation step of preparing the solder bump forming member and a substrate having a plurality of electrodes, an arrangement step of opposing and contacting a surface having a recess of the solder bump forming member and a surface having the electrodes of the substrate, and a heating step of heating the solder particles to a temperature equal to or higher than the melting point of the solder particles.

[0022] In one aspect of the heating step in the method for manufacturing an electrode substrate with solder bumps, the solder particles may be heated to a temperature equal to or higher than the melting point of the solder particles while the solder bump forming member and the substrate are brought into contact with each other under a pressurized state.

[0023] One aspect of the method for manufacturing an electrode substrate with solder bumps may further include a reduction step of exposing the solder particles to a reducing atmosphere before the arrangement step.

[0024] One aspect of the method for manufacturing an electrode substrate with solder bumps may further include a reduction step of exposing the solder particles to a reducing atmosphere after the arrangement step and before the heating step.

[0025] In one aspect of the heating step in the method for manufacturing an electrode substrate with solder bumps, the solder particles may be heated to a temperature equal to or higher than the melting point of the solder particles in a reducing atmosphere.

[0026] One aspect of the method for manufacturing an electrode substrate with solder bumps may further include a removal step of removing the solder bump forming member from the substrate after the heating step.

[0027] One aspect of the method for manufacturing an electrode substrate with solder bumps may further include a cleaning step of removing the solder particles not bonded to the electrodes after the removal step.

Advantages of the Invention

[0028] According to the present invention, even if the connection locations of circuit members to be electrically connected to each other are minute, it is possible to provide a solder bump forming member and a method for manufacturing the same, which are useful for manufacturing a connection structure excellent in both insulation reliability and conduction reliability. Further, according to the present invention, it is possible to provide a method for manufacturing an electrode substrate with solder bumps using the member.

Brief Description of the Drawings

[0029]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0030] Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments. Note that the materials exemplified below may be used alone or in combination of two or more, unless otherwise specified. The content of each component in the composition means the total amount of the plurality of substances corresponding to each component in the composition, unless otherwise specified, when there are a plurality of substances corresponding to each component in the composition. The numerical range indicated using "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value of a certain numerical range may be replaced with the upper limit value or the lower limit value of another numerical range. In the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.

[0031] <Component for forming solder bumps> In one aspect, the component for forming solder bumps includes a substrate having a plurality of recesses, and solder particles and a fluidizing agent in the recesses. The average particle diameter of the solder particles is 1 to 35 μm, and the C.V. value is 20% or less.

[0032] FIG. 1 is a cross-sectional view schematically showing a component for forming solder bumps according to an embodiment. The component 10 for forming solder bumps includes a substrate 60 having a plurality of recesses 62, and solder particles 1 and a fluidizing agent F in the recesses 62. In a predetermined longitudinal section of the component 10 for forming solder bumps, one solder particle 1 is arranged to be aligned in the lateral direction (the left-right direction in FIG. 1) in a state of being separated from an adjacent solder particle 1. The solder particles 1 may be in contact with the side surface and / or the bottom surface thereof in the recesses 62. The fluidizing agent F may be present between the solder particles 1 and the bottom surface of the recesses 62. The component for forming solder bumps may be in the form of a film (film for forming solder bumps), a sheet (sheet for forming solder bumps), or the like.

[0033] (Solder particles) The average particle diameter of the solder particles 1 is, for example, 35 μm or less, preferably 30 μm or less, 25 μm or less, 20 μm or less, or 15 μm or less. Further, the average particle diameter of the solder particles 1 is, for example, 1 μm or more, preferably 2 μm or more, more preferably 3 μm or more, and still more preferably 5 μm or more.

[0034] The average particle diameter of the solder particles 1 can be measured using various methods according to the size. For example, methods such as dynamic light scattering method, laser diffraction method, centrifugal sedimentation method, electrical sensing zone method, and resonant mass measurement method can be used. Further, a method of measuring the particle size from an image obtained by an optical microscope, an electron microscope, etc. can be used. Specific devices include flow-type particle image analyzers, Microtrac, Coulter counters, etc. The average particle diameter of the solder particles 1 can be the equivalent diameter of the projected area circle (the diameter of a circle having an area equal to the projected area of the particle) when observing the solder particles 1 from a direction perpendicular to the main surface of the solder bump forming member 10.

[0035] From the viewpoint of realizing more excellent conductive reliability and insulation reliability, the C.V. value of the solder particles 1 is preferably 20% or less, more preferably 10% or less, and still more preferably 7% or less. Further, the lower limit of the C.V. value of the solder particles 1 is not particularly limited. For example, the C.V. value of the solder particles 1 may be 1% or more, or may be 2% or more.

[0036] The C.V. value of the solder particles 1 is calculated by multiplying the value obtained by dividing the standard deviation of the particle diameter measured by the above-described method by the average particle diameter by 100.

[0037] A flat portion may be formed on a part of the surface of the solder particles. FIG. 2(a) is a view of the solder particles 1 seen from the side opposite to the opening of the concave portion 62 in FIG. 1. The solder particles 1 have a shape in which a flat portion 11 having a diameter A is formed on a part of the surface of a sphere having a diameter B. Note that the solder particles 1 shown in FIGS. 1 and 2(a) have the flat portion 11 because the bottom of the concave portion 62 is flat. However, when the bottom of the concave portion 62 has a shape other than flat, the solder particles 1 have a different-shaped surface corresponding to the shape of the bottom.

[0038] As shown in Fig. 2(a), the solder particle 1 may have a flat portion 11 formed on a part of its surface. At this time, it is preferable that the surface other than the flat portion 11 is spherical crown-shaped. That is, the solder particle 1 may have the flat portion 11 and the spherical crown-shaped curved surface portion. The ratio (A / B) of the diameter A of the flat portion 11 to the diameter B of the solder particle 1 may be, for example, more than 0.01 and less than 1.0 (0.01 < A / B < 1.0), and may be 0.1 to 0.9. The flat portion 11 and the bottom surface of the concave portion 62 may be in contact. As shown in Fig. 1, since the solder particle 1 has the flat portion 11 and the flat portion is in contact with the bottom surface of the concave portion, it is difficult for the solder particle 1 to detach from the solder bump forming member 10. In addition, the flat portion may also occur at the portion where the inner wall portion of the concave portion 62 and the solder particle 1 are in contact. However, when manufacturing the solder bump forming member, when the solder particle 1 is once taken out from the substrate 60 and the solder particle 1 and the fluidizing agent F are rearranged in the concave portion of the substrate again as described later, the flat portion 11 and the bottom surface of the concave portion 62 do not necessarily have to be in contact.

[0039] When a quadrilateral circumscribing the projection image of the solder particle 1 is created by two pairs of parallel lines, when the distances between the opposing sides are X and Y (where Y < X), the ratio (Y / X) of Y to X may be more than 0.8 and less than 1.0 (0.8 < Y / X < 1.0), and may be 0.9 or more and less than 1.0. Such a solder particle 1 can be said to be a particle closer to a true sphere. Since the solder particle 1 is closer to a true sphere, unevenness in contact between the solder particle 1 and the electrode is less likely to occur, and a stable connection tends to be obtained.

[0040] Fig. 2(b) is a diagram showing the distances X and Y (where Y < X) between opposite sides when a quadrilateral circumscribing the projection image of a solder particle is created by two pairs of parallel lines. For example, an arbitrary particle is observed with a scanning electron microscope to obtain a projection image. Two pairs of parallel lines are drawn for the obtained projection image. One pair of parallel lines is arranged at the position where the distance between the parallel lines is minimized, and the other pair of parallel lines is arranged at the position where the distance between the parallel lines is maximized, and Y / X of the particle is obtained. This operation is performed on 300 solder particles to calculate the average value, which is taken as Y / X of the solder particle.

[0041] The solder particle 1 may contain tin or a tin alloy. As the tin alloy, for example, In - Sn alloy, In - Sn - Ag alloy, Sn - Au alloy, Sn - Bi alloy, Sn - Bi - Ag alloy, Sn - Ag - Cu alloy, Sn - Cu alloy, etc. can be used. Specific examples of these tin alloys are as follows. · In - Sn (In 52 mass%, Bi 48 mass%, melting point 118°C) · In - Sn - Ag (In 20 mass%, Sn 77.2 mass%, Ag 2.8 mass%, melting point 175°C) · Sn - Bi (Sn 43 mass%, Bi 57 mass%, melting point 138°C) · Sn - Bi - Ag (Sn 42 mass%, Bi 57 mass%, Ag 1 mass%, melting point 139°C) · Sn - Ag - Cu (Sn 96.5 mass%, Ag 3 mass%, Cu 0.5 mass%, melting point 217°C) · Sn - Cu (Sn 99.3 mass%, Cu 0.7 mass%, melting point 227°C) · Sn - Au (Sn 21.0 mass%, Au 79.0 mass%, melting point 278°C)

[0042] The solder particle may contain indium or an indium alloy. As the indium alloy, for example, In - Bi alloy, In - Ag alloy, etc. can be used. Specific examples of these indium alloys are as follows. · In - Bi (In 66.3 mass%, Bi 33.7 mass%, melting point 72°C) · In - Bi (In 33.0 mass%, Bi 67.0 mass%, melting point 109°C) ·In-Ag (In 97.0 mass%, Ag 3.0 mass%, melting point 145°C)

[0043] Depending on the use (temperature during connection) of solder particle 1, etc., the above tin alloy or indium alloy can be selected. For example, when using solder particle 1 for fusion bonding at low temperature, an In-Sn alloy or Sn-Bi alloy can be adopted, and in this case, fusion bonding can be performed at 150°C or lower. When using materials with a high melting point such as Sn-Ag-Cu alloy and Sn-Cu alloy, high reliability can be maintained even after high-temperature storage.

[0044] Solder particle 1 may contain one or more selected from Ag, Cu, Ni, Bi, Zn, Pd, Pb, Au, P, and B. Among these elements, Ag or Cu may be included from the following viewpoints. That is, when solder particle 1 contains Ag or Cu, the melting point of solder particle 1 can be lowered to about 220°C, and the bonding strength with the electrode is further improved, so that better electrical communication reliability is easily obtained.

[0045] The Cu content of solder particle 1 is, for example, 0.05 to 10 mass%, and may be 0.1 to 5 mass% or 0.2 to 3 mass%. When the Cu content is 0.05 mass% or more, it is easier to achieve better solder connection reliability. Also, when the Cu content is 10 mass% or less, it is likely to become solder particle 1 with a low melting point and excellent wettability, and as a result, the connection reliability of the joint by solder particle 1 is likely to be good.

[0046] The Ag content of solder particle 1 is, for example, 0.05 to 10 mass%, and may be 0.1 to 5 mass% or 0.2 to 3 mass%. When the Ag content is 0.05 mass% or more, it is easier to achieve better solder connection reliability. Also, when the Ag content is 10 mass% or less, it is likely to become solder particle 1 with a low melting point and excellent wettability, and as a result, the connection reliability of the joint by solder particle 1 is likely to be good.

[0047] (Fluidizing agent) The fluidizing agent F has the function of flowing as a fluid phase during reflow to extrude the solder particles 1 from the recess 62 toward the electrode side. The fluidizing agent F may be a flux, an organic solvent, or the like. The flux has the function of dissolving the oxides on the surface of the solder particles and the electrode surface to improve the wettability of the solder to the electrode.

[0048] As the fluidizing agent F, various organic solvents can be used. The boiling point of the fluidizing agent F may be higher than the melting point of the solder. When the electrode and the recess are opposed to each other and heated, since the boiling point of the fluidizing agent F is higher than the melting point of the solder, the fluidizing agent F flows in the recess, and the solder particles also flow along with the flow of the fluidizing agent F. By the fluidizing agent F and the solder particles flowing, the electrode surface and the solder particles are more likely to come into contact, and as a result, the formation of solder bumps is promoted. Therefore, when forming solder bumps, if the heating temperature is at least higher than the melting point of the solder particles, higher than the softening point or melting point of the fluidizing agent F, and lower than the boiling point of the fluidizing agent F, solder bumps are more likely to be formed on the electrodes. After the solder bump formation is sufficiently performed, if the heating temperature is raised above the boiling point of the fluidizing agent F, the residue derived from the fluidizing agent F on the substrate surface and the electrode surface can be reduced.

[0049] As various organic solvents that can be used for the fluidizing agent F, aliphatic hydrocarbons such as cyclohexane (boiling point: 80 °C), cycloheptane (boiling point: 118 °C), cyclooctane (boiling point: 149 °C), heptane (boiling point: 98 °C), octane (boiling point: 126 °C), nonane (boiling point: 150 °C), decane (boiling point 174 °C), undecane (boiling point: 196 °C), dodecane (boiling point: 215 °C), tridecane (boiling point: 234 °C), tetradecane (boiling point: 254 °C), pentadecane (boiling point: 269 °C), hexadecane (boiling point: 287 °C), heptadecane (boiling point: 302 °C), octadecane (boiling point: 317 °C), nonadecane (boiling point: 330 °C) can be used. These aliphatic hydrocarbons are nonpolar and have no reducing function for metals used in solders and electrodes such as Au and Cu, but can be appropriately selected as solvents having a boiling point above the melting point of the solder, and have the function of flowing the solder particles by heating and bringing the solder particles into contact with the electrode surface.

[0050] Examples of various organic solvents that can be used as fluidizing agent F include monohydric and polyhydric alcohols such as pentanol, hexanol, heptanol, octanol, decanol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, α-terpineol, isobornyl cyclohexanol (MTPH), etc.; ethers such as ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, diethylene glycol isobutyl ether, diethylene glycol hexyl ether, triethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, diethylene glycol isopropyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, propylene glycol propyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, dipropylene glycol dimethyl ether, tripropylene glycol methyl ether, tripropylene glycol dimethyl ether, etc.; esters such as ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, dipropylene glycol methyl ether acetate (DPMA), ethyl lactate, butyl lactate, γ-butyrolactone, propylene carbonate, etc.; acid amides such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, etc.; aliphatic hydrocarbons such as cyclohexane, octane, nonane, decane, undecane, etc.; aromatic hydrocarbons such as benzene, toluene, xylene, etc.; mercaptans having an alkyl group with 1 to 18 carbon atoms; and mercaptans having a cycloalkyl group with 5 to 7 carbon atoms.Examples of mercaptans having an alkyl group with 1 to 18 carbon atoms include ethyl mercaptan, n-propyl mercaptan, i-propyl mercaptan, n-butyl mercaptan, i-butyl mercaptan, t-butyl mercaptan, pentyl mercaptan, hexyl mercaptan, and dodecyl mercaptan. Examples of mercaptans having a cycloalkyl group with 5 to 7 carbon atoms include cyclopentyl mercaptan, cyclohexyl mercaptan, and cycloheptyl mercaptan. In addition, examples of organic solvents include alicyclic amines such as monoalkylamine, dialkylamine, trialkylamine, alkanolamine, cyclohexylamine, and dicyclohexylamine, and aromatic amines such as diphenylamine and triphenylamine. For example, examples of organic solvents include ethylenediethanolamine, n-butyldiethanolamine, diethanolamine, N,N-bis(2-hydroxyethyl)isopropanolamine, and the like.

[0051] As the organic solvent that can be used as the fluidizing agent F, glycol ether solvents can also be used. For example, as solvents having a boiling point of 200 °C or lower, dipropylene glycol monomethyl ether, propylene glycol monobutyl ether, diethylene glycol dimethyl ether, ethylene glycol monoallyl ether, and ethylene glycol monoisopropyl ether can be mentioned. As solvents having a boiling point exceeding 200 °C, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, triethylene glycol monomethyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol mono-2-ethylhexyl ether, diethylene glycol dibutyl ether, triethylene glycol butyl methyl ether, tetraethylene glycol dimethyl ether, and the like can be mentioned.

[0052] As the flux that can be used as the fluidizing agent F, those generally used for solder bonding or the like can be used. The flux can be appropriately selected according to the composition, melting point, surface state of the solder particles, conditions of heating and atmosphere during transfer, and the like. For example, zinc chloride, a mixture of zinc chloride and an inorganic halide, a mixture of zinc chloride and an inorganic acid, a molten salt, phosphoric acid, a derivative of phosphoric acid, an organic halide, hydrazine, an organic acid, rosin, and the like can be mentioned. These may be used alone or in combination of two or more kinds.

[0053] Examples of the molten salt include ammonium chloride. Examples of the organic acid include lactic acid, citric acid, stearic acid, glutamic acid, glutaric acid, etc. Further, examples of the organic acid that can be used as a flux include organic acids having 8 to 16 carbon atoms. Examples of the organic acid having 8 to 16 carbon atoms include saturated fatty acids such as caprylic acid, methylheptanoic acid, ethylhexanoic acid, propylpentanoic acid, pelargonic acid, methyloctanoic acid, ethylheptanoic acid, propylhexanoic acid, capric acid, methylnonanoic acid, ethyloctanoic acid, propylheptanoic acid, butylhexanoic acid, undecanoic acid, methyldecanoic acid, ethyldecanoic acid, propyloctanoic acid, butylheptanoic acid, lauric acid, methylundecanoic acid, ethyldecanoic acid, propylnonanoic acid, butyloctanoic acid, pentylheptanoic acid, tridecanoic acid, methyldodecanoic acid, ethylundecanoic acid, propyldecanoic acid, butylnonanoic acid, pentyloctanoic acid, myristic acid, methyltridecanoic acid, ethyldodecanoic acid, propylundecanoic acid, butyldecanoic acid, pentylnonanoic acid, hexyl octanoic acid, pentadecanoic acid, methyltetradecanoic acid, ethyltridecanoic acid, propyldodecanoic acid, butylundecanoic acid, pentyl decanoic acid, hexylnonanoic acid, palmitic acid, methylpentadecanoic acid, ethyltetradecanoic acid, propyltridecanoic acid, butyldodecanoic acid, pentylundecanoic acid, hexyl decanoic acid, heptylnonanoic acid, methylcyclohexanecarboxylic acid, ethylcyclohexanecarboxylic acid, propylcyclohexanecarboxylic acid, butylcyclohexanecarboxylic acid, pentylcyclohexanecarboxylic acid, hexylcyclohexanecarboxylic acid, heptylcyclohexanecarboxylic acid, octylcyclohexanecarboxylic acid, nonylcyclohexanecarboxylic acid; unsaturated fatty acids such as octenoic acid, nonenoic acid, methylnonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, myristoleic acid, pentadecenoic acid, hexadecenoic acid, palmitoleic acid, sapienic acid; aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, o-phenoxybenzoic acid, methylbenzoic acid, ethylbenzoic acid, propylbenzoic acid, butylbenzoic acid, pentylbenzoic acid, hexylbenzoic acid, heptylbenzoic acid, octylbenzoic acid, nonylbenzoic acid.The organic acid may be used alone or in combination of two or more. Examples of the rosin include activated rosin and inactivated rosin. Rosin is a resin mainly composed of abietic acid. By using an organic acid or rosin having two or more carboxyl groups as the flux, the effect of further improving the conduction reliability between electrodes is achieved.

[0054] The melting point of the flux may be 50°C or higher, 70°C or higher, or 80°C or higher. The melting point of the flux may be 200°C or lower, 160°C or lower, 150°C or lower, or 140°C or lower. When the melting point of the flux is within the above lower limit and the above upper limit, the flux effect is more effectively exerted, and the solder particles are more efficiently arranged on the electrode. The range of the melting point of the flux may be 80 to 190°C or 80 to 140°C or lower.

[0055] Examples of the flux having a melting point in the range of 80 to 190°C include dicarboxylic acids such as succinic acid (melting point 186°C), glutaric acid (melting point 96°C), adipic acid (melting point 152°C), pimelic acid (melting point 104°C), and suberic acid (melting point 142°C), benzoic acid (melting point 122°C), malic acid (melting point 130°C), and the like. The fluidizing agent may contain at least one selected from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, benzoic acid, and malic acid.

[0056] The amount of the fluidizing agent F present in the recess 62 is not particularly limited, but from the viewpoint of easily obtaining an appropriate fluidizing action, flux effect, etc., it may be 1 to 50 parts by mass, may be 1 to 20 parts by mass, or may be 20 to 50 parts by mass with respect to 100 parts by mass of the solder particles 1. The fluidizing agent F may be a mixture with a solvent or a resin material. As the solvent, the various organic solvents described above can be used. If it is a mixture, the concentration of the fluidizing agent F can be appropriately adjusted according to the solder particles 1. In order for the mixture to extrude the solder particles 1 onto the electrode during reflow, it is advisable to adjust the softening point or melting point so that the fluidity of the mixture increases by heating. If the softening point or melting point is higher than room temperature, it is difficult for the solder particles 1 to fall off from the recess 62 at room temperature, and the handling before the solder bump forming process becomes easy. Examples of the solvent constituting the mixture include high-boiling solvents. Since the high-boiling solvent volatilizes by reheating after flowing the solder particles 1 onto the electrode, it is difficult to remain on the electrode. As the solvent, an alcohol-based solvent or the like can be used. If it is an alcohol-based solvent, it can exhibit reducibility.

[0057] (Substrate) As the material constituting the substrate 60, for example, inorganic materials such as silicon, various ceramics, glass, metals such as stainless steel, and organic materials such as various resins can be used. Among these, the substrate 60 may be a material having heat resistance that does not deteriorate at the melting temperature of the solder fine particles. Further, the substrate 60 may be a material having heat resistance that does not deform even at the temperature at which the solder fine particles are melted. Further, the substrate 60 may be a material that does not alloy or react with the material constituting the solder fine particles and does not change. Further, the recess 62 of the substrate 60 can be formed by a known method such as a cutting method, a photolithography method, or an imprint method. In particular, when the imprint method is used, a recess 62 with an accurate size can be formed in a short process.

[0058] The surface of the substrate 60 may have a coating layer. From the perspective of expanding the selectivity of materials that can be used for the substrate 60, the coating layer may be a material that is difficult or impossible to alloy with the material constituting the solder particles. As the coating layer, an inorganic substance or an organic substance can be used. As the coating layer, an inorganic substance having a strong oxide layer on the surface such as aluminum or chromium, an oxide such as titanium oxide, a nitride such as boron nitride, a diamond-like carbon, a diamond, a carbon-based material such as graphite, a fluororesin, a high heat-resistant resin such as polyimide, etc. can be used. Furthermore, the coating layer may have a role of adjusting the wettability with the solder. By providing a coating layer on the surface of the substrate 60, the wettability with the solder can be appropriately adjusted according to the purpose of use.

[0059] As methods for forming the coating layer, lamination, solution dipping, coating, painting, impregnation, sputtering, plating, etc. can be used.

[0060] From the perspective of facilitating the setting of the conditions for the transfer process, the material of the substrate 60 may be a material having physical properties similar to or the same as the electrode for transferring the solder particles and the substrate on which the electrode is formed. For example, if the coefficient of thermal expansion (CTE) is similar or the same, misalignment is less likely to occur during the transfer of the solder particles.

[0061] The substrate 60 may be provided with an alignment mark. This alignment mark is preferably readable by a camera. There may also be an alignment mark on the substrate side having the electrode. By providing the alignment marks on the substrate 60 and the substrate having the electrode, when transferring the solder particles onto the electrode, the camera mounted on the alignment device can read the alignment mark on the substrate 60 and the alignment mark of the substrate having the electrode, and accurately grasp the position of the recess 62 having the solder particles and the position of the electrode for transferring the solder particles. Also, by providing the alignment marks on the substrate 60 and the substrate having the electrode, the solder particles can be transferred onto the electrode with high positional accuracy.

[0062] The alignment mark may be located at one or more positions on the substrate 60. If there are two or more alignment marks, the positioning accuracy will be higher.

[0063] The specific configuration of the substrate 60 will be described below.

[0064] (Organic material single layer) The substrate 60 may be made of an organic material. The organic material may be a polymer material, and thermoplastic, thermosetting, photocurable materials, etc. can be used. By using an organic material, the range of selection of physical properties is widened, so it is easy to form the substrate 60 according to the purpose. For example, if it is an organic material, the substrate 60 (including the recess 62) is easy to bend or stretch. If it is an organic material, various methods can also be used to form the recess 62. As a method for forming the recess 62, imprinting, photolithography, cutting, laser processing, etc. can be used. In particular, according to the imprint method, a mold having a desired shape can be pressed against the substrate 60 made of an organic material to form an arbitrary shape on the surface. By forming a convex pattern on the mold and pressing it against the substrate 60 made of an organic material, a recess 62 having a desired pattern can be formed. Also, a photocurable resin can be used to form the recess 62. After applying the photocurable resin to the mold and exposing it, when the mold is peeled off, a substrate 60 having the recess 62 can be formed. In the case of cutting, the recess 62 can be formed with a drill or the like.

[0065] (Organic material multi-layer) The substrate may be composed of a plurality of organic materials. Further, the substrate may have a plurality of layers, and the plurality of layers may each be composed of a different organic material. The organic material may be a polymer material, and thermoplastic, thermosetting, photocurable materials, etc. can be used. The substrate may have two layers composed of an organic material, and a recess may be formed in the organic material layer on one side. By forming multiple layers, it is possible to select materials with appropriate wettability with solder for the material of the recess that comes into contact with the solder, etc., and select each material with different functions. For example, FIG. 8 is a cross-sectional view schematically showing an example of the substrate. The substrate 600 includes a base layer 601 and a recess layer 602. The base layer 601 is a layer that supports the recess layer 602, and the recess layer 602 is a layer in which the recess 62 is formed by processing. A resin material excellent in heat resistance and dimensional stability can be used for the base layer 601, and a material excellent in the processability of the recess 62 can be selected for the recess layer 602. For example, a thermoplastic resin such as polyethylene terephthalate or polyimide can be used for the base layer 601, and a thermosetting resin capable of forming the recess 62 by an imprint mold can be used for the recess layer 602. For example, by sandwiching a thermosetting resin between polyethylene terephthalate and an imprint mold and heating and pressurizing, a substrate 600 (including the recess 62) with excellent flatness can be obtained. Also, when the recess 62 is formed using a photocurable material, a material with high light transmissivity may be used for the base layer 601. Examples of the material with high light transmissivity may be polyethylene terephthalate, transparent (colorless type) polyimide, polyamide, etc. When the recess 62 is formed using a photocurable material, for example, an appropriate amount of the photocurable material is applied to the surface of the imprint mold, a polyethylene terephthalate film is placed thereon, and ultraviolet light is irradiated while pressing with a roller from the polyethylene terephthalate side. Then, after curing the photocurable material, the imprint mold is peeled off to obtain a substrate 600 having a layer of polyethylene terephthalate and a layer of the photocurable material, and the recess 62 is formed of the photocurable material. The material composition of the inner wall and bottom of the recess 62 can be changed. For example, the inner wall and bottom of the recess 62 can have the same resin material composition.In addition, the inner wall and the bottom of the concave portion 62 can be made of different resin materials (for example, a thermosetting material and a thermoplastic material).

[0066] Also, a photosensitive material may be used as the organic material. The photosensitive material may be a positive-type photosensitive material or a negative-type photosensitive material. For example, by forming a photosensitive material with a uniform thickness on the surface of a thermoplastic polyethylene terephthalate film and performing exposure and development, the concave portion 62 can be easily formed. The method using exposure and development (photolithography method) is widely used in the manufacture of semiconductors, wiring boards, etc., and is a highly versatile method. In addition to exposure using a mask, a direct drawing method such as direct laser exposure can also be used as the exposure method.

[0067] By making the material of the base layer 601 thicker than the thickness of the material forming the concave portion layer 602, the physical properties of the entire substrate 600 can be predominantly determined by the properties of the material of the base layer 601. Thereby, even if there are weaknesses in the properties of the material forming the concave portion layer 602, for example, it can be compensated for by the material of the base layer 601. For example, even if the material forming the concave portion layer 602 is a material that easily thermally contracts, by selecting a material with low thermal shrinkage for the material of the base layer 601 and making the thickness of the base layer 601 thicker than the thickness of the material forming the concave portion layer 602, deformation during heating can be suppressed.

[0068] In addition, an organic material can be appropriately selected according to the purpose, such as a combination of a resin material excellent in heat resistance or dimensional stability and a material with little component elution at the melting temperature of solder fine particles, or a combination of a resin material excellent in heat resistance or dimensional stability and a material with appropriate wettability with solder.

[0069] As described above, the substrate may be a substrate 600 composed of a base layer 601 and a recess layer 602. For example, by using the recess layer 602 as a photosensitive material, the recess 62 can be formed by photolithography. By using a light or thermosetting material, a thermoplastic material, etc. for the recess layer 602, the recess 62 can be easily formed by an imprint method. In addition, since it is also possible to adjust the characteristics of the entire substrate by changing the thickness of the base layer 601, there is an advantage that a substrate having desired characteristics can be manufactured.

[0070] (Inorganic material single layer (opaque)) The substrate 60 may be composed of an inorganic material. From the viewpoint of easily controlling the elution of components and the generation of foreign matters, for example, as the inorganic material, silicon (silicon wafer), stainless steel, aluminum, etc. can be used. When these materials are used in a semiconductor mounting process, etc., it is easy to take countermeasures against contamination and can contribute to high yield and stable production. Also, for example, when transferring the solder particles formed in the recess 62 to the electrodes on a silicon wafer, if the substrate 60 is made from a silicon wafer, materials with close or the same CTE will be used. As a result, misalignment, warping, etc. are less likely to occur, and accurate transfer to the correct position becomes possible. As a method for forming the recess 62, processing by laser, cutting, etc., dry etching or wet etching method, electron beam lithography (e.g., FIB processing), etc. can be used. Dry etching is widely used in the production of semiconductors, MEMS, etc. and can process inorganic materials with high precision from the micron order to the nano order.

[0071] (Inorganic material single layer (transparent)) As the substrate 60, glass, quartz, sapphire, etc. can be used. Since these materials are transparent, it is easy to align when transferring the solder particles in the recess 62 to another substrate on which electrodes are formed. As a method for forming the recess 62, processing by laser, cutting, etc., dry etching or wet etching method, electron beam lithography (e.g., FIB processing), etc. can be used.

[0072] The advantage of using an inorganic material is that it has excellent dimensional stability compared to an organic material. When transferring solder particles in the recess 62 onto the electrodes, it can be transferred with high positional accuracy. For example, when transferring solder particles to a plurality of electrodes with a size and pitch on the order of micrometers, by using an inorganic material with excellent dimensional stability, the solder particles can be transferred to the same position on any electrode.

[0073] (Organic-inorganic composite material) The substrate may be composed of a plurality of materials. Further, the substrate may have a plurality of layers, and the plurality of layers may be made of different materials respectively. As the organic-inorganic composite material, for example, a combination of inorganic materials and a combination of inorganic materials and organic materials can be used. The combination of inorganic materials and organic materials can achieve both dimensional stability and workability of the recess 62. Examples of the substrate having a combination of inorganic materials and organic materials include a substrate including a base layer 601 made of a metal such as silicon, various ceramics, glass, stainless steel, etc., which are inorganic materials, and a recess layer 602 made of an organic material. Such a substrate can be obtained, for example, by forming a photosensitive material film on the surface of a silicon wafer and forming a recess by exposure and development. The inner wall and bottom of the recess 62 may be composed of a photosensitive material, or the inner wall of the recess 62 may be composed of a photosensitive material and the bottom may be composed of a silicon wafer. The configuration of the recess 62 can be appropriately selected according to the purpose such as wettability with solder particles in the recess 62 and ease of transfer to the electrode. When the inner wall and bottom of the recess 62 are composed of a photosensitive material, a method can be used in which a photosensitive material layer is provided on the surface of the silicon wafer by forming and curing a photosensitive material film on the surface of the silicon wafer, a photosensitive material is again formed on the surface of the layer, and the recess 62 is provided by exposure and development. In this case, the photosensitive material on the surface side of the silicon wafer and the photosensitive material provided on the outermost layer may have different compositions. The photosensitive material can be appropriately selected in consideration of the wettability and contaminability of solder particles. In particular, when transferring the solder particles formed in the recess 62 onto the electrode, the surface of the outermost photosensitive material layer may come into contact with the surface of the electrode or the substrate having the electrode. Therefore, a photosensitive material that does not damage the electrode and the substrate or does not contaminate the electrode and the substrate can be appropriately selected. The photosensitive material may be a material that prevents elution of uncured components, contamination by halogen-based materials, silicone-based materials, etc. Further, the photosensitive material may be a material having high resistance to a reducing atmosphere, flux, etc. when transferring solder particles to the electrode. For example, the photosensitive material may be a material having resistance to a reducing atmosphere such as formic acid, hydrogen, hydrogen radicals, etc. Furthermore, the photosensitive material may be a material having high resistance to the temperature when transferring solder particles to the electrode.Specifically, the photosensitive material may be a material that is resistant to temperatures between 100°C and 300°C. Since the melting point of solder particles varies depending on their constituent materials, the heat-resistant temperature of the photosensitive material can also be selected according to the solder material to be used. When using a lead-free solder widely used in electronic devices, such as a tin-silver-copper solder (e.g., SAC305 with a melting point of 219°C), a material with heat resistance of 220°C or higher, particularly 260°C or higher when used in the reflow process, can be used. When using a tin-bismuth solder (e.g., SnBi58 with a melting point of 139°C), a material with heat resistance of 140°C or higher can be used, and if the material has heat resistance of 160°C or higher, the industrial applicability becomes wider. When using indium solder (melting point 159°C), a material with heat resistance of 170°C or higher can be used. When using indium-tin solder (e.g., melting point 120°C), a material with heat resistance of 130°C or higher can be used.

[0074] Examples of other substrates include a substrate having a recess 62 formed of a thermosetting or thermoplastic resin on a stainless steel plate. The substrate can be obtained by sandwiching a thermosetting material (resin) between the stainless steel plate and an imprint mold, heating under pressure, and then peeling off the imprint mold. Examples of other substrates include a substrate having a recess 62 formed of a photocurable material on a glass plate. The substrate can be obtained by applying a photocurable material on the glass plate, exposing it while pressing an imprint mold to cure the photocurable material, and then peeling off the imprint mold. When forming the recess 62 using an imprint mold, the material composition of the inner wall and bottom of the recess 62 can be changed according to the pressure conditions. For example, when the pressure conditions are relaxed, the inner wall and bottom of the recess 62 can have the same resin material composition. On the other hand, when the pressure conditions are strengthened, the inner wall of the recess 62 can be made of a resin material and the bottom can be made of an inorganic material.

[0075] As the material of the base layer 601, a composite material containing glass fibers, fillers, etc. and a resin component can also be used. Examples of the composite material include copper-clad laminates for wiring boards. A photosensitive material, a thermosetting resin, a photocurable resin, etc. can be applied to the surface of the copper-clad laminate to form the concave portion 62 as described above. Although the copper-clad laminate mainly contains a large amount of resin material, it can be made to have a low CTE by combining it with glass fibers, various fillers, etc., so that the above-mentioned dimensional stability can be ensured. Further, when an electrode is formed on the copper-clad laminate, by forming the concave portion 62 on the same copper-clad laminate, the CTEs of both become the same or close values, and there is an advantage that alignment is easy during the transfer of the solder particles in the concave portion 62 and displacement is less likely to occur.

[0076] As the material of the concave portion layer 602, a sealing material for packages can also be used. As the sealing material, any of solid, liquid, and film-like materials can be used. The concave portion 62 can be formed by laminating the sealing material in a thin layer on glass, a silicon wafer, etc. and pressurizing and heating it with an imprint mold.

[0077] <Manufacturing method of member for forming solder bumps> The manufacturing method of the member 10 for forming solder bumps includes a preparation step of preparing a substrate having a plurality of concave portions and solder fine particles, a housing step of housing at least a part of the solder fine particles in the concave portions, a fusion step of fusing the solder fine particles housed in the concave portions to form solder particles in the concave portions, and an injection step of disposing (injecting) a fluidizing agent (fluid phase) into the concave portions in which the solder particles are formed.

[0078] With reference to FIGS. 3 to 5, the manufacturing method of the member 10 for forming solder bumps according to the first embodiment will be described.

[0079] First, prepare solder fine particles and a substrate 60 for accommodating the solder fine particles. FIG. 3(a) is a plan view schematically showing an example of the substrate 60, and FIG. 3(b) is a cross-sectional view taken along line Ib-Ib of FIG. 3(a). The substrate 60 shown in FIG. 3(a) has a plurality of recesses 62. The plurality of recesses 62 may be regularly arranged in a predetermined pattern. The positions and number of the plurality of recesses 62 may be set according to the shape, size, pattern, etc. of the electrodes to be connected.

[0080] There is no particular limitation on the distance L between adjacent recesses, but it can be 0.1 times or more of the average particle diameter of the solder particles to be accommodated, and may be 1 time or more. The distance L can be appropriately adjusted according to the arrangement of the electrodes forming the solder bumps. The distance between the recesses is the distance from the edge to the edge of the recess opening, not the center-to-center distance of the recesses.

[0081] The recess 62 of the substrate 60 is preferably formed in a tapered shape in which the opening area expands from the bottom 62a side of the recess 62 toward the surface 60a side of the substrate 60. That is, as shown in FIGS. 3(a) and 3(b), the width of the bottom 62a of the recess 62 (width a in FIGS. 3(a) and 3(b)) is preferably narrower than the width of the opening on the surface 60a of the recess 62 (width b in FIGS. 3(a) and 3(b)). And the size (width a, width b, volume, taper angle, depth, etc.) of the recess 62 may be set according to the size of the target solder particles.

[0082] Note that the shape of the recess 62 may be a shape other than the shapes shown in FIGS. 3(a) and 3(b). For example, the shape of the opening on the surface 60a of the recess 62 may be an ellipse, a triangle, a quadrilateral, a polygon, etc., in addition to a circle as shown in FIG. 3(a).

[0083] Also, the shape of the recess 62 in a cross-section perpendicular to the surface 60a may be, for example, the shape shown in FIG. 4. FIGS. 4(a) to (h) are cross-sectional views schematically showing examples of the cross-sectional shape of the recess provided in the substrate. In any of the cross-sectional shapes shown in FIGS. 4(a) to (h), the width of the opening (width b) on the surface 60a of the recess 62 is the maximum width in the cross-sectional shape. Thereby, the solder particles formed in the recess 62 are easily taken out, and the workability is improved. Further, since the width of the opening (width b) is the maximum width in the cross-sectional shape, when transferring the solder particles 1 onto the electrode, the solder particles 1 can easily escape from the recess 62, and an improvement in the transfer rate can be expected. Also, by appropriately adjusting the width of the opening (width b), displacement during the transfer of the solder particles 1 onto the electrode is less likely to occur, and it becomes easier to form solder bumps at accurate positions.

[0084] The solder fine particles prepared in the preparation step may contain fine particles having a particle diameter smaller than the width of the opening (width b) on the surface 60a of the recess 62, and it is preferable to contain more fine particles having a particle diameter smaller than the width b. For example, it is preferable that the D10 particle diameter of the particle size distribution of the solder fine particles is smaller than the width b, more preferably the D30 particle diameter of the particle size distribution is smaller than the width b, and even more preferably the D50 particle diameter of the particle size distribution is smaller than the width b.

[0085] The particle size distribution of the solder fine particles can be measured using various methods according to the size. For example, methods such as dynamic light scattering method, laser diffraction method, centrifugal sedimentation method, electrical sensing zone method, resonance mass measurement method, etc. can be used. Further, a method of measuring the particle size from an image obtained by an optical microscope, an electron microscope, etc. can be used. Specific devices include flow type particle image analyzers, Microtrac, Coulter counters, etc.

[0086] The C.V. value of the solder fine particles prepared in the preparation step is not particularly limited, but from the viewpoint of improving the filling property of the recess 62 by the combination of large and small fine particles, it is preferable that the C.V. value is high. For example, the C.V. value of the solder fine particles may exceed 20%, preferably 25% or more, and more preferably 30% or more.

[0087] The C.V. value of the solder fine particles is calculated by multiplying the value obtained by dividing the standard deviation of the particle diameter measured by the above-described method by the average particle diameter (D50 particle diameter) by 100.

[0088] The solder fine particles may contain tin or a tin alloy. As the tin alloy, for example, an In-Sn alloy, an In-Sn-Ag alloy, a Sn-Au alloy, a Sn-Bi alloy, a Sn-Bi-Ag alloy, a Sn-Ag-Cu alloy, a Sn-Cu alloy, etc. can be used. Specific examples of these tin alloys include the following examples. · In-Sn (In 52 mass%, Bi 48 mass%, melting point 118°C) · In-Sn-Ag (In 20 mass%, Sn 77.2 mass%, Ag 2.8 mass%, melting point 175°C) · Sn-Bi (Sn 43 mass%, Bi 57 mass%, melting point 138°C) · Sn-Bi-Ag (Sn 42 mass%, Bi 57 mass%, Ag 1 mass%, melting point 139°C) · Sn-Ag-Cu (Sn 96.5 mass%, Ag 3 mass%, Cu 0.5 mass%, melting point 217°C) · Sn-Cu (Sn 99.3 mass%, Cu 0.7 mass%, melting point 227°C) · Sn-Au (Sn 21.0 mass%, Au 79.0 mass%, melting point 278°C)

[0089] The solder fine particles may contain indium or an indium alloy. As the indium alloy, for example, an In-Bi alloy, an In-Ag alloy, etc. can be used. Specific examples of these indium alloys include the following examples. · In-Bi (In 66.3 mass%, Bi 33.7 mass%, melting point 72°C) · In-Bi (In 33.0 mass%, Bi 67.0 mass%, melting point 109°C) · In-Ag (In 97.0 mass%, Ag 3.0 mass%, melting point 145°C)

[0090] The above-mentioned tin alloy or indium alloy can be selected according to the use of the solder particles (temperature during use), etc. For example, when it is desired to obtain solder particles for use in fusion bonding at low temperatures, an In-Sn alloy or a Sn-Bi alloy may be employed. In this case, solder particles that can be fusion-bonded at 150°C or lower can be obtained. When materials with high melting points such as Sn-Ag-Cu alloys and Sn-Cu alloys are employed, solder particles that can maintain high reliability even after being left at high temperatures can be obtained.

[0091] The solder fine particles may contain one or more selected from Ag, Cu, Ni, Bi, Zn, Pd, Pb, Au, P, and B. Among these elements, Ag or Cu may be contained from the following viewpoints. That is, when the solder fine particles contain Ag or Cu, the melting point of the obtained solder particles can be lowered to about 220°C, and solder particles with excellent bonding strength to the electrode can be obtained, resulting in better conduction reliability.

[0092] The Cu content of the solder fine particles is, for example, 0.05 to 10% by mass, and may be 0.1 to 5% by mass or 0.2 to 3% by mass. When the Cu content is 0.05% by mass or more, it is easy to obtain solder particles capable of achieving good solder connection reliability. Also, when the Cu content is 10% by mass or less, solder particles with a low melting point and excellent wettability are easily obtained, and as a result, the connection reliability of the electrode with solder bumps tends to be better.

[0093] The Ag content of the solder fine particles is, for example, 0.05 to 10% by mass, and may be 0.1 to 5% by mass or 0.2 to 3% by mass. If the Ag content is 0.05% by mass or more, it is easy to obtain solder particles capable of achieving good solder connection reliability. Also, when the Ag content is 10% by mass or less, solder particles with a low melting point and excellent wettability are easily obtained, and as a result, the connection reliability of the electrode with solder bumps tends to be better.

[0094] In the accommodation step, solder fine particles prepared in the preparation step are accommodated in each of the recesses 62 of the substrate 60. The accommodation step may be a step of accommodating all of the solder fine particles prepared in the preparation step in the recesses 62, or may be a step of accommodating a part of the solder fine particles prepared in the preparation step (for example, those smaller than the width b of the opening of the recess 62 among the solder fine particles) in the recesses 62.

[0095] FIG. 5 is a cross-sectional view schematically showing a state in which solder fine particles 111 are accommodated in the recess 62 of the substrate 60. As shown in FIG. 5, a plurality of solder fine particles 111 are accommodated in each of the plurality of recesses 62.

[0096] The amount of the solder fine particles accommodated in the recess 62 is preferably, for example, 20% or more, more preferably 30% or more, still more preferably 50% or more, and most preferably 60% or more with respect to the volume of the recess 62. Thereby, variations in the accommodation amount are suppressed, and it becomes easier to obtain solder particles with a smaller particle size distribution.

[0097] The method of accommodating the solder fine particles in the recess 62 is not particularly limited. The accommodation method may be either dry or wet. For example, the solder fine particles prepared in the preparation step are placed on the substrate 60, and by rubbing the surface 60a of the substrate 60 using a squeegee, sufficient solder fine particles can be accommodated in the recess 62 while removing excess solder fine particles. When the width b of the opening of the recess 62 is larger than the depth of the recess 62, the solder fine particles may jump out from the opening of the recess 62. When using a squeegee, the solder fine particles jumping out from the opening of the recess 62 are removed. Examples of the method of removing excess solder fine particles also include blowing compressed air, rubbing the surface 60a of the substrate 60 with a non-woven fabric or a bundle of fibers, etc. These methods are preferable for handling solder fine particles that are easily deformed because the physical force is weaker than that of a squeegee. Also, with these methods, the solder fine particles jumping out from the opening of the recess 62 can be left in the recess.

[0098] The fusion process is a process of fusing solder fine particles 111 accommodated in the recess 62 (by heating to, for example, 130 to 260 °C) to form solder particles 1 inside the recess 62. The solder fine particles 111 accommodated in the recess 62 melt and merge together, and become spherical due to surface tension. At this time, at the contact portion with the bottom 62a of the recess 62, the molten solder follows the bottom 62a to form a flat portion 11. As a result, the formed solder particles 1 have a shape having a flat portion 11 on a part of the surface. In this way, the solder bump forming member 10 shown in FIG. 1 is obtained.

[0099] As a method of melting the solder fine particles 111 accommodated in the recess 62, a method of heating the solder fine particles 111 to a temperature equal to or higher than the melting point of the solder can be mentioned. The solder fine particles 111 may not melt, may not wet and spread, and may not merge even when heated at a temperature equal to or higher than the melting point due to the influence of the oxide film. Therefore, after exposing the solder fine particles 111 to a reducing atmosphere to remove the surface oxide film of the solder fine particles 111, by heating to a temperature equal to or higher than the melting point of the solder fine particles 111, the solder fine particles 111 can be melted, wet and spread, and merged. Further, the melting of the solder fine particles 111 is preferably performed in a reducing atmosphere. By heating the solder fine particles 111 to a temperature equal to or higher than the melting point of the solder fine particles 111 and providing a reducing atmosphere, the oxide film on the surface of the solder fine particles 111 is reduced, and the melting, wetting and spreading, and merging of the solder fine particles 111 easily proceed efficiently. That is, the manufacturing method of the solder bump forming member may further include a reducing step of exposing the solder fine particles accommodated in the recess to a reducing atmosphere before the fusion step. Further, in the fusion step of the manufacturing method of the solder bump forming member, the solder fine particles may be fused in a reducing atmosphere.

[0100] The method for creating a reducing atmosphere is not particularly limited as long as the above-described effects can be obtained. For example, there are methods using hydrogen gas, hydrogen radicals, formic acid gas, etc. For example, by using a hydrogen reduction furnace, a hydrogen radical reduction furnace, a formic acid reduction furnace, or a conveyor furnace or continuous furnace thereof, the solder fine particles 111 can be melted under a reducing atmosphere. These apparatuses may be equipped with a heating device, a chamber filled with an inert gas (nitrogen, argon, etc.), a mechanism for evacuating the inside of the chamber, etc. in the furnace, which makes it easier to control the reducing gas. Also, if the inside of the chamber can be evacuated, after melting and coalescing the solder fine particles 111, voids can be removed by reducing the pressure, and solder particles 1 with even better connection stability can be obtained.

[0101] Profiles such as the reduction, dissolution conditions, temperature, and adjustment of the furnace atmosphere of the solder fine particles 111 may be appropriately set in consideration of the melting point, particle size, recess size, material of the substrate 60, etc. of the solder fine particles 111. For example, the substrate 60 filled with the solder fine particles 111 in the recess is inserted into the furnace, evacuated, then a reducing gas is introduced to fill the furnace with the reducing gas, the surface oxide film of the solder fine particles 111 is removed, then the reducing gas is removed by evacuation, and then heated to a temperature above the melting point of the solder fine particles 111 to melt and coalesce the solder fine particles to form solder particles in the recess 62. After that, nitrogen gas is filled and then the furnace temperature is returned to room temperature to obtain the solder particles 1. Also, for example, the substrate 60 filled with the solder fine particles 111 in the recess is inserted into the furnace, evacuated, then a reducing gas is introduced to fill the furnace with the reducing gas, the solder fine particles 111 are heated by a furnace heating heater to remove the surface oxide film of the solder fine particles 111, then the reducing gas is removed by evacuation, and then heated to a temperature above the melting point of the solder fine particles 111 to melt and coalesce the solder fine particles to form solder particles in the recess 62. After that, nitrogen gas is filled and then the furnace temperature is returned to room temperature to obtain the solder particles 1. By heating the solder fine particles under a reducing atmosphere, there is an advantage that the reducing power increases and it becomes easier to remove the surface oxide film of the solder fine particles.

[0102] Furthermore, for example, a substrate 60 filled with solder fine particles 111 is inserted into a furnace. After evacuation, a reducing gas is introduced to fill the furnace with the reducing gas, and the furnace is heated by a furnace internal heater to a temperature equal to or higher than the melting point of the solder fine particles 111, so as to remove the surface oxide film of the solder fine particles 111 by reduction and at the same time dissolve and coalesce the solder fine particles to form solder particles in the recess 62. After removing the reducing gas by evacuation and further reducing the voids in the solder particles, nitrogen gas is filled and then the furnace temperature is returned to room temperature, whereby solder particles 1 can be obtained. In this case, since the adjustment of the increase and decrease of the furnace temperature can be performed only once respectively, there is an advantage that the processing can be performed in a short time.

[0103] After forming the solder particles in the recess 62 as described above, a step of once again making the inside of the furnace into a reducing atmosphere to remove the surface oxide film that could not be completely removed may be added. Thereby, residues such as solder fine particles that remained unfused and a part of the oxide film that remained unfused can be reduced.

[0104] When using an atmospheric pressure conveyor furnace, the substrate 60 filled with solder fine particles 111 is placed on a conveyor for transportation, and the solder particles 1 can be obtained by continuously passing through a plurality of zones. For example, the substrate 60 filled with solder fine particles 111 is placed on a conveyor set at a constant speed, passed through a zone filled with an inert gas such as nitrogen or argon at a temperature lower than the melting point of the solder fine particles 111, and then passed through a zone where a reducing gas such as formic acid gas at a temperature lower than the melting point of the solder fine particles 111 exists to remove the surface oxide film of the solder fine particles 111. Subsequently, the solder fine particles 111 are melted and unified by passing through a zone filled with an inert gas such as nitrogen or argon at a temperature equal to or higher than the melting point of the solder fine particles 111, and then passed through a cooling zone filled with an inert gas such as nitrogen or argon to obtain the solder particles 1. For example, the substrate 60 filled with solder fine particles 111 is placed on a conveyor set at a constant speed, passed through a zone filled with an inert gas such as nitrogen or argon at a temperature equal to or higher than the melting point of the solder fine particles 111, and then passed through a zone where a reducing gas such as formic acid gas at a temperature equal to or higher than the melting point of the solder fine particles 111 exists to remove the surface oxide film of the solder fine particles 111, melt and unify them, and then passed through a cooling zone filled with an inert gas such as nitrogen or argon to obtain the solder particles 1. Since the above-mentioned conveyor furnace can be processed at atmospheric pressure, a film-like material can also be continuously processed by roll-to-roll. For example, a continuous roll product of the substrate 60 filled with solder fine particles 111 is produced, a roll unwind machine is installed on the inlet side of the conveyor furnace, and a roll winder is installed on the outlet side of the conveyor furnace. The substrate 60 is transported at a constant speed and passed through each zone in the conveyor furnace, so that the solder fine particles 111 filled in the recesses can be fused.

[0105] According to the preparation process to the fusion process, solder particles 1 with a uniform size can be formed regardless of the material and shape of the solder fine particles 111. For example, indium-based solder can be deposited by plating, but it is difficult to deposit it in particle form and it is soft and difficult to handle. However, by using indium-based solder fine particles as raw materials in the above method, indium-based solder particles having a uniform particle diameter can be easily manufactured. Further, since the formed solder particles 1 can be handled in a state of being accommodated in the recess 62 of the substrate 60, they can be transported, stored, etc. without deforming the solder particles 1. Furthermore, since the formed solder particles 1 are in a state of being accommodated in the recess 62 of the substrate 60, they can be brought into contact with the electrode without deforming the solder particles. The average particle diameter of the obtained solder particles may be 1 to 35 μm, and the C.V. value may be 20% or less.

[0106] Further, the solder fine particles 111 may have a large variation in particle size distribution or may have an irregular shape, and can be suitably used as a raw material as long as they can be accommodated in the recess 62.

[0107] Also, in the above method, the shape of the recess 62 of the substrate 60 can be freely designed by lithography, machining, imprinting, etc. Since the size of the solder particles 1 depends on the amount of the solder fine particles 111 accommodated in the recess 62, the size of the solder particles 1 can be freely designed by designing the recess 62.

[0108] Next, in the step of disposing the fluidizing agent, the fluidizing agent is disposed in the recess 62 in which the solder particles 1 are formed. The method of disposing the fluidizing agent is not particularly limited. For example, methods such as dipping the substrate 60 in a liquid fluidizing agent solution and pulling it out, applying or dropping the liquid fluidizing agent onto the substrate 60 (particularly onto the recess 62) can be mentioned. Further, in the case of a solid fluidizing agent, methods such as disposing a fluidizing agent having a diameter smaller than the diameter of the recess 62 on the surface of the substrate 60 and filling the recess 62 with a squeegee can be mentioned. Alternatively, methods of disposing the fluidizing agent by CVD, vapor deposition, sputtering method, etc. can be mentioned. Excess fluidizing agent that has overflowed from the recess 62 may be removed. Examples of the removal method include methods such as volatilization under reduced pressure, squeegee, wiping, scraping, laser etching, and blasting.

[0109] For example, an appropriate amount of the liquid fluidizing agent can be dropped onto the substrate 60 (on the recess 62), and while spreading the liquid fluidizing agent with a squeegee, the recess 62 can be filled. Then, the excess liquid fluidizing agent that has not been filled in the recess 62 can be removed again with a squeegee. The fluidizing agent that cannot be completely removed with a squeegee can be wiped off with, for example, a dust-free clean cloth.

[0110] The manufacturing method of the solder bump forming member 10 may include a pre-process of preparing a substrate having a plurality of recesses, solder particles, and a fluidizing agent, and an arranging process of arranging the solder particles and the fluidizing agent in the recesses. In this way, the solder particles 1 can be once taken out from the substrate 60 and then the solder particles 1 and the fluidizing agent F can be rearranged in the recesses of the substrate again to produce a solder bump forming member. According to this method, in the melting process, the fine solder particles 111 that did not become solder particles, the fine solder particles 111 existing outside the recess 62, other residues, foreign matters, etc., and the solder particles 1 can be separated. Specifically, after passing through the melting process, the substrate 60 having the solder particles 1 in the recess 62 is immersed in a solvent to take out the solder particles 1 from the recess 62. After the substrate 60 from which the solder particles 1 have been taken out is lifted from the solvent, the solvent is passed through a filter, a mesh, etc. to remove foreign matters from the solvent. Then, the solder particles 1 are once dispersed in the solvent and left standing for sedimentation separation. By performing sedimentation separation, the solder particles 1 and the residues (for example, fine solder particles 111 and foreign matters) are separated to obtain a mixture of the solder particles 1 and the solvent. After performing sedimentation separation a plurality of times and further removing the residues, the mixture of the solder particles 1 and the solvent is vacuum dried to obtain highly pure solder particles 1. In the arranging process, the solder particles 1 are rearranged again in the recesses 62 on the surface of the substrate 60. Then, the fluidizing agent can be arranged in the recesses 62. Or, after the fluidizing agent is arranged in the recesses 62 in advance, the solder particles 1 may be arranged in the recesses 62. Or, the fluidizing agent and the solder particles 1 may be mixed in advance and the mixture may be arranged in the recesses 62. The substrate for rearranging the solder particles may be the substrate used when manufacturing the solder particles or may be a different substrate.

[0111] In addition, as the solder particles 1, in addition to those obtained by the above method, those manufactured by known methods such as the atomization method, the water atomization method, the method of cutting a thin wire and melting it, and the method of producing minute solder droplets using a precision discharge head can be used.

[0112] <Manufacturing Method of Electrode Substrate with Solder Bumps> The method for manufacturing an electrode substrate with solder bumps includes a preparation step of preparing the solder bump forming member and a substrate having a plurality of electrodes, an arrangement step of bringing the surface having the concave portion of the solder bump forming member and the surface having the electrodes of the substrate into contact with each other in an opposed manner, and a heating step of heating the solder particles to a temperature equal to or higher than the melting point of the solder particles.

[0113] Specific examples of the substrate (circuit member) having a plurality of electrodes on its surface include chip components such as IC chips (semiconductor chips), resistor chips, capacitor chips, driver ICs; and rigid package substrates. These circuit members are provided with circuit electrodes, and those having a large number of circuit electrodes are common. Other examples of the substrate having a plurality of electrodes on its surface include wiring substrates such as flexible tape substrates having metal wirings, flexible printed wiring boards, and glass substrates vapor-deposited with indium tin oxide (ITO).

[0114] Specific examples of the electrodes include electrodes such as copper, copper / nickel, copper / nickel / gold, copper / nickel / palladium, copper / nickel / palladium / gold, copper / nickel / gold, copper / palladium, copper / palladium / gold, copper / tin, copper / silver, indium tin oxide. The electrodes can be formed by electroless plating, electrolytic plating, sputtering, or etching of a metal foil.

[0115] Figs. 6(a) and 6(b) are cross-sectional views schematically showing an example of the manufacturing process of an electrode substrate with solder bumps. The substrate 60 shown in Fig. 6(a) is in a state where one solder particle 1 and a fluidizing agent F are accommodated in each of the recesses 62. On the other hand, the substrate 2 has a plurality of electrodes 3 on its surface. The surface of the substrate 2 on the side of the electrodes 3 is brought into contact with the opening-side surface of the recess 62 of the substrate 60 so as to face each other. The number of solder particles 1 contacting each electrode 3 is not particularly limited, and it may be one particle per electrode, or may be a plurality of particles per electrode. Since the force acting between the solder particle 1 and the recess 62 (for example, an intermolecular force such as van der Waals force) is greater than the gravitational force applied to the solder particle 1, even when the main surface of the substrate 60 is directed downward, the solder particle 1 remains in the recess 62 without falling off. Further, at least a part of the solder particle 1 is in contact with the bottom and / or inner wall portion of the recess 62, and when it has a flat portion, the solder particle 1 is in close contact with the recess 62 and is difficult to fall off.

[0116] With the solder particles and the electrodes in contact, by heating the entire electrode substrate and the substrate 60 to a temperature higher than the melting point of the solder particles 1 (for example, 130 to 260 °C) at least, the solder particles 1, which have become more fluid due to the heated fluidizing agent F, come into contact with the electrodes 3 and melt, and solder bumps are formed on the electrodes 3. From the viewpoint of more preferably performing the bonding between the solder particle 1 and the electrode 3, in the heating step, the solder particles 1 may be heated to a temperature equal to or higher than the melting point of the solder particles while bringing the solder bump forming member 10 and the substrate 2 into contact with each other in a pressurized state. The pressurized state means a state in which the solder bump forming member 10 and the substrate 2 are pressed against each other in the directions of arrows A and B in Fig. 6(a) with a force of about 30 to 600 Pa. The solder particles 1 are accommodated in the recesses 62 and are still pressed against the electrodes. Therefore, even if they flow due to the action of the fluidizing agent F, it is difficult for the solder particles 1 in adjacent recesses 62 to mix with each other, and solder bumps of the same size can be formed only on the desired electrodes. Further, it is difficult for solder to bridge adjacent electrodes, and short-circuit defects can be suppressed.

[0117] The solder particles 1 rapidly oxidize upon heating in the atmosphere, making it difficult for wetting to spread on the electrode 3. Therefore, a deoxidized atmosphere is preferable for the atmosphere during heating. For example, it may be an inert gas atmosphere such as nitrogen or argon, a vacuum atmosphere, etc. As the furnace, a reflow furnace (under a nitrogen atmosphere) or a vacuum reflow furnace commonly used in the solder bonding process can be used, such as a conveyor-type reflow furnace or a batch-type (chamber-type) reflow furnace under a nitrogen atmosphere. When using these reflow furnaces, if a process of evacuating after the solder melts is added, the bubbles (voids) in the solder can be removed. Furthermore, from the perspective of productivity improvement, a laminator can also be used. In the case of a roller-type laminator, pressure and heating can be applied simultaneously. Additionally, a vacuum pressure laminator can also be used. The vacuum pressure laminator can evacuate the inside of the chamber and can apply pressure and heat simultaneously, making it preferable for easily transferring solder bumps onto the electrode 3. Also, since continuous conveyance by a carrier film is possible, there is an advantage of being able to achieve high productivity.

[0118] The solder particles 1 may not melt or wet and spread even when heated at a temperature above the melting point due to the influence of the oxide film. Therefore, after exposing the solder particles 1 to a reducing atmosphere to remove the surface oxide film of the solder particles 1, the solder particles 1 can be melted by heating them to a temperature above the melting point of the solder particles 1. Also, the melting of the solder particles 1 is preferably carried out in a reducing atmosphere. By heating the solder particles 1 to a temperature above the melting point of the solder particles 1 and providing a reducing atmosphere, the oxide film on the surface of the solder particles 1 is reduced, and further the oxide film on the electrode surface is reduced, making it easier for the melting and wetting spread of the solder particles 1 to proceed efficiently. That is, the method for manufacturing an electrode substrate with solder bumps may further include a reduction step of exposing the solder particles (and / or electrodes) to a reducing atmosphere before the placement step or after the placement step and before the heating step. Further, in the heating step of the method for manufacturing an electrode substrate with solder bumps, the solder particles may be heated to a temperature above the melting point of the solder particles in a reducing atmosphere. In the heating step of forming the solder bumps on the electrodes, by bringing the electrode into close contact with the opening surface of the member for forming the solder bumps (in a pressurized state if necessary), the solder bumps are formed only on the electrodes, and it is easy to suppress the bridge formed by the solder between adjacent electrodes.

[0119] For details of the reducing atmosphere, the description of the method for manufacturing the member for forming the solder bumps can be appropriately referred to.

[0120] After the heating step, by cooling the whole, the electrode 3 and the solder bumps 1A formed by melting the solder particles 1 are fixed to each other, and the two are electrically connected. The method for manufacturing an electrode substrate with solder bumps may further include a removal step of removing the member for forming the solder bumps from the substrate after the heating step. After the solder bumps 1A are formed on the electrode 3, the electrode substrate 20 with solder bumps can be obtained by removing the member 10 for forming the solder bumps from the substrate 2 (removal step). Fig. 6(b) is a schematic diagram of the electrode substrate 20 with solder bumps thus obtained.

[0121] On the obtained electrode substrate 20 with solder bumps, there may be solder particles 1 that have detached from the concave portion 62 and are not used for bonding to the electrode 3. Therefore, the method for manufacturing an electrode substrate with solder bumps may further include a cleaning step of removing the solder particles 1 not bonded to the electrode after the removal step. Examples of the cleaning method include blowing compressed air, rubbing the surface of the substrate with a non-woven fabric or a bundle of fibers, and the like. In addition, when the fluidizing agent F exists as a residue on the electrode substrate 20 with solder bumps, the fluidizing agent can also be removed by the cleaning step. In the cleaning step, a solution in which the fluidizing agent F is easily dissolved can be used.

[0122] According to the method for manufacturing an electrode substrate with solder bumps, an electrode substrate 20 including a substrate 2, an electrode 3, and a solder bump 1A in this order can be obtained.

[0123] <Method for manufacturing a connection structure> FIGS. 7(a) and 7(b) are cross-sectional views schematically showing an example of the manufacturing process of the connection structure. The method for manufacturing the connection structure will be described with reference to FIGS. 7(a) and 7(b). First, the electrode substrate 20 with solder bumps shown in FIG. 6(b) is prepared in advance. In addition, another substrate 4 having a plurality of other electrodes 5 on its surface is prepared. Then, both are arranged so that the solder bump 1A and the other electrode 5 face each other. Thereafter, pressure is applied in the thickness direction of the laminate of these members (the directions of arrows A and B shown in FIG. 7(a)). When applying pressure, the whole is heated to at least a temperature higher than the melting point of the solder bump 1A (for example, 130 to 260°C), so that the solder bump 1A melts between the electrode 3 and the other electrode 5. Thereafter, by cooling the whole, a solder layer 1B is formed between the electrode 3 and the other electrode 5, and the electrodes are electrically connected. In order to suppress oxidation of the solder bump 1A and the electrode 5, it is preferable to heat in an atmosphere where oxygen is blocked. For example, heating in an inert gas atmosphere such as nitrogen is preferable. Specifically, a vacuum reflow furnace, a nitrogen reflow furnace, or the like can be used.

[0124] Furthermore, in order to melt the solder bump 1A by heating and more preferably bond the opposing electrodes 3 and 5, it is preferable to heat in a reducing atmosphere. To create a reducing atmosphere, hydrogen gas, hydrogen radicals, formic acid, etc. can be used. Specifically, a hydrogen reduction furnace, a hydrogen reflow furnace, a hydrogen radical furnace, a formic acid furnace, these vacuum furnaces, continuous furnaces, conveyor furnaces can be used. By creating a reducing atmosphere, the oxide films on the surface of the solder bump 1A and the surface of the electrode 5 can be reduced and removed, so that the solder bump 1A easily spreads and wets on the electrode 5, and a more stable bond is achieved between the electrodes 3 and 5 via the solder layer 1B.

[0125] Furthermore, in order to achieve a stable connection, pressure may be applied. Prepare in advance the electrode substrate 20 with solder bumps shown in Fig. 6(b). Also, prepare another substrate 4 having a plurality of other electrodes 5 on its surface. Then, arrange the two so that the solder bump 1A and the other electrode 5 face each other. Thereafter, apply pressure in the thickness direction of the laminate of these members (the directions of arrow A and arrow B shown in Fig. 7(a)). When applying pressure, at least heat the whole to a temperature higher than the melting point of the solder bump 1A (for example, 130 to 260 °C), so that the solder bump 1A melts between the electrode 3 and the other electrode 5. Thereafter, by cooling the whole, a solder layer 1B is formed between the electrode 3 and the other electrode 5, and the electrodes are electrically connected. Also in this case, in order to suppress oxidation of the surfaces of the solder bump 1A, the electrode 5, and the electrode 3, it is preferable to perform the above steps under vacuum, in an inert gas atmosphere such as nitrogen, or in a reducing atmosphere. Examples of methods for creating a reducing atmosphere include the aforementioned hydrogen gas, hydrogen radicals, formic acid, etc. Specifically, a hydrogen reduction furnace, a hydrogen reflow furnace, a hydrogen radical furnace, a formic acid furnace, these vacuum furnaces, continuous furnaces, conveyor furnaces, etc. can be used.

[0126] As a method of creating a reducing atmosphere, materials with a reducing effect can be utilized. For example, a flux material or a material containing a flux component can be disposed in the vicinity of solder bump 1A, electrode 5, and electrode 3. Pastes, films, etc. containing a flux material and a material containing a flux component can be used. First, prepare in advance an electrode substrate 20 with solder bumps as shown in Fig. 6(b). A paste containing a flux material or a flux component is disposed on the entire surface of the electrode substrate 20 where the solder bumps 1A are formed, or in the vicinity of electrode 3 including solder bumps 1A and solder bumps 1A. Also, prepare another substrate 4 having a plurality of other electrodes 5 on its surface. Then, arrange the two such that solder bump 1A and the other electrode 5 face each other. After that, while keeping solder bump 1A and the other electrode 5 in contact via, for example, a paste containing a flux material or a flux component, heat to at least a temperature higher than the melting point of solder bump 1A (e.g., 130°C to 260°C), whereby solder bump 1A melts between electrode 3 and the other electrode 5. Then, by cooling the whole, a solder layer 1B is formed between electrode 3 and the other electrode 5, and the electrodes are electrically connected. After that, when the flux component is washed away, corrosion of solder layer 1B, electrode 3, and electrode 5 due to flux residues can be suppressed.

[0127] As another method, prepare in advance an electrode substrate 20 with solder bumps as shown in Fig. 6(b). Also, prepare another substrate 4 having a plurality of other electrodes 5 on its surface, and dispose a paste containing a flux material or a flux component on the entire surface of the substrate 4 having the electrodes 5, or in the vicinity of the surface of the electrodes 5. Then, arrange the two such that solder bump 1A and the other electrode 5 face each other. After that, while keeping solder bump 1A and the other electrode 5 in contact via, for example, a paste containing a flux material and a flux component, heat to at least a temperature higher than the melting point of solder bump 1A (e.g., 130°C to 260°C), whereby solder bump 1A melts between electrode 3 and the other electrode 5. Then, by cooling the whole, a solder layer 1B is formed between electrode 3 and the other electrode 5, and the electrodes are electrically connected.

[0128] Also, a film containing a flux component can also be used. Prepare in advance an electrode substrate 20 with solder bumps as shown in Fig. 6(b). Place a film containing a flux component on the surface side of the electrode substrate 20 where the solder bumps 1A are formed. Also, prepare another substrate 4 having a plurality of other electrodes 5 on its surface. Then, arrange the two so that the solder bumps 1A and the other electrodes 5 face each other. After that, with the solder bumps 1A and the other electrodes 5 in contact via the film containing a flux component, or while applying pressure between the opposing electrodes 3 and 5 to push out the film containing a flux component from between them, heat at least to a temperature higher than the melting point of the solder bumps 1A (for example, 130°C to 260°C) with the solder bumps 1A and the electrodes 5 in contact, so that the solder bumps 1A melt between the electrode 3 and the other electrode 5. Then, by cooling the whole, a solder layer 1B is formed between the electrode 3 and the other electrode 5, and the electrodes are electrically connected.

[0129] The paste and film containing a flux component may contain a thermosetting material. Thereby, simultaneously with the melting of the solder bumps 1A, the thermosetting component can be cured to fix the electrode substrate 20 and the substrate 4. The curing of the thermosetting material may be carried out by reheating in a subsequent process separately from the heating for melting the solder bumps 1A. Also, the film containing a flux component may be placed in advance on the surface side of the substrate 4 where the electrodes 5 are formed. The choice of the placement position of whether to place the film containing a flux component on the solder bump 1A side or on the substrate 4 side having the electrodes 5 can be appropriately selected according to the shape of the electrodes, the shape and size of the solder bumps 1A, the convenience in the bonding process, etc.

[0130] As a heating method for melting the solder bump 1A, under vacuum, for example, the heating plate in the reflow furnace is heated, and heat is transmitted to the solder bump 1A through the substrate 2 and the substrate 4 in contact with the heating plate. There is also a method using radiation such as infrared rays. In addition to, or in combination with, the above-described heating methods using the heating plate and infrared rays, a method of heating the solder bump 1A through the heated gas and gas can be used. Specifically, the solder bump 1A can be heated by heating an inert gas, nitrogen, hydrogen, hydrogen radicals, or formic acid. The flux material and the flux component may include at least one selected from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, benzoic acid, and malic acid.

[0131] As another method, a method using electromagnetic waves such as microwaves can be mentioned. For example, specific electromagnetic waves that heat the components of the electrode 3, the electrode 5, and the solder bump 1A can be applied from the outside. For example, when the substrates 4 and 2 are resin substrates, when specific electromagnetic waves are irradiated from the outside of the substrates 4 and 2, the electromagnetic waves penetrate the substrates 4 and 2, and the electrode 3, the solder bump 1A, or the electrode 5 is heated by the electromagnetic waves. In the case of this method, since the portion to be joined can be selectively heated, there is an advantage that no unnecessary heat history remains. For example, even if the substrates 2 and 4 are made of a material with low heat resistance, the solder bump 1A can be melted to surely join the electrode 3 and the electrode 5. In addition, since it is difficult for a heat history to remain in the entire joining system, there is an advantage that warping and decomposition after joining are easily suppressed. Also, when using microwaves, compared to using a heating plate, infrared rays, a heating gas, etc. as described above, the solder bump 1A can be melted in a short time, so there is an advantage that the heat history to the entire system to be joined can be reduced, and the above-described effects are easily obtained. Furthermore, when using microwaves, only the portions of the electrode 3, the solder bump 1A, and the electrode 5 to be joined or melted can be locally heated. Therefore, there is no need to heat the entire system, and even if there are materials with low heat resistance or other electronic components that do not want to be heated in the vicinity of the electrode 3 and the electrode 5, the solder bump 1A can be melted and joined.

[0132] As another method, there is a method that utilizes ultrasonic waves. For example, when an ultrasonic vibrator is disposed on the side opposite to the electrode 3 of the substrate 2 and ultrasonic waves are applied, the solder bump 1A is melted by the vibration energy of the ultrasonic waves. As a result, the electrode 3 and the electrode 5 that has been disposed in advance at the position facing the electrode 3 are joined via the solder layer 1B. Since the joining by ultrasonic waves can melt the solder bump 1A in a short time, it is not necessary to apply heat to the entire substrate 2 and substrate 4, and even if the substrate 2 and substrate 4 are made of a material with low heat resistance, the electrode 3 and the electrode 5 can be surely joined.

[0133] FIG. 7(b) is a schematic diagram of the connection structure 30 obtained in this way. That is, FIG. 7(b) schematically shows a state in which the electrode 3 of the substrate 2 and the other electrode 5 of the other substrate 4 are connected via the solder layer 1B formed by fusion. In this specification, "fusion" means a state in which at least a part of the electrode is joined by solder (solder bump 1A) melted by heat and then solidifies, and solder is joined to the surface of the electrode. The connection structure 30 can be said to include a first circuit member including a substrate and a plurality of electrodes on its surface, a second circuit member including another substrate and a plurality of other electrodes on its surface, and a solder layer between the plurality of electrodes and the plurality of other electrodes. Note that the space between the first circuit member and the second circuit member can be filled with an underfill material mainly composed of, for example, an epoxy resin.

[0134] The connection structure can be applied to connection parts such as semiconductor memories and semiconductor logic chips, connection parts for primary and secondary mounting of semiconductor packages, bonded bodies such as CMOS image sensor elements, laser elements, and LED light-emitting elements, and devices such as cameras, sensors, liquid crystal displays, personal computers, mobile phones, smartphones, and tablets using these.

[0135] As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited to the above embodiments.

Example

[0136] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[0137] <Production of solder bump forming film> (Production Example 1) Step a1: Classification of solder fine particles 100 g of Sn-Bi solder fine particles (manufactured by 5N Plus, melting point 139 °C, Type 8) were immersed in distilled water, ultrasonically dispersed, allowed to stand, and the solder fine particles floating in the supernatant were collected. This operation was repeated to collect 10 g of solder fine particles. The average particle diameter of the obtained solder fine particles was 1.0 μm, and the C.V. value was 42%. Step b1: Placement on the substrate A substrate (polyimide film, thickness 100 μm) having a plurality of recesses shown in Table 1, with an opening diameter of 2.3 μmφ, a bottom diameter of 2.0 μmφ, and a depth of 2.0 μm (the bottom diameter of 2.0 μmφ is located at the center of the opening diameter of 2.3 μmφ when viewed from above the opening) was prepared. The plurality of recesses were regularly arranged at intervals of 1.0 μm. The solder fine particles (average particle diameter 1.0 μm, C.V. value 42%) obtained in Step a were placed in the recesses of the substrate. In addition, by rubbing the surface side where the recesses of the substrate were formed with a slightly adhesive roller, excess solder fine particles were removed, and a substrate having solder fine particles arranged only in the recesses was obtained. Step c1: Formation of solder particles The substrate with solder fine particles placed in the recesses in Step b1 was placed in a hydrogen reduction furnace (manufactured by Shinko Seiki Co., Ltd., vacuum soldering apparatus), evacuated, and then hydrogen gas was introduced into the furnace to fill the furnace with hydrogen. Then, after maintaining the furnace at 280 °C for 20 minutes, it was evacuated again, nitrogen was introduced to return to atmospheric pressure, and then the temperature in the furnace was lowered to room temperature, thereby forming solder particles inside the recesses.

[0138] <Evaluation of solder particles> A part of the substrate obtained through Process c1 was fixed to the surface of the pedestal for SEM observation, and platinum sputtering was performed on the surface. Using SEM, the diameters of 300 solder particles were measured, and the average particle diameter and C.V. value were calculated. The results are shown in Table 2. Also, the surface shape of a part of the substrate obtained through Process c1 was measured using a laser microscope (LEXT OLS5000 - SAF manufactured by Olympus Corporation), the height of the solder particles from the substrate surface was measured, and the average value of 300 was calculated. The results are shown in Table 2.

[0139] Process d1: Flux Placement 90 parts by mass of dihydroterpineol and 20 parts by mass of adipic acid as a flux component were put in and mixed to obtain a mobile phase. This mobile phase was placed in the recess where the solder particles obtained in Process c1 were placed. Then, the surface side of the substrate where the recess was formed was rubbed with a rubber squeegee to remove the excess mobile phase (flux component) that did not fill the recess. After that, the surface of the base material was further wiped with a dust-free clean cloth to produce a film for forming solder bumps.

[0140] (Production Examples 2 - 6) A film for forming solder bumps was produced and evaluated in the same manner as in Production Example 1 except that the recess size etc. was changed as described in Table 1. The results are shown in Table 2.

[0141] (Production Example 7) A film for forming solder bumps was produced and evaluated in the same manner as in Production Example 1 except that Process c2 below was performed instead of Process c1. The results are shown in Table 2. Process c2: Formation of Solder Particles The substrate with solder fine particles placed in the recess in Process b1 was put into a hydrogen radical reduction furnace (Plasma Flow Apparatus manufactured by Shinko Seiki Co., Ltd.). After evacuation, hydrogen gas was introduced into the furnace to fill the furnace with hydrogen gas. Then, the temperature inside the furnace was adjusted to 120°C, and hydrogen radicals were irradiated for 5 minutes. Then, the hydrogen gas inside the furnace was removed by evacuation, heated to 170°C, nitrogen was introduced into the furnace to return to atmospheric pressure, and then the temperature inside the furnace was lowered to room temperature to form solder particles.

[0142] (Production Examples 8 to 12) A solder bump forming film was produced and evaluated in the same manner as in Production Example 7, except that the size of the concave portion and the like were changed as described in Table 1. The results are shown in Table 2.

[0143] (Production Example 13) A solder bump forming film was produced and evaluated in the same manner as in Production Example 1, except that the following step c3 was performed instead of step c1. The results are shown in Table 2. Step c3: Formation of solder particles The substrate with solder fine particles disposed in the concave portion in step b1 was put into a formic acid reduction furnace. After evacuation, formic acid gas was introduced into the furnace to fill the furnace with formic acid gas. Then, the temperature in the furnace was adjusted to 130 °C and maintained for 5 minutes. Thereafter, the formic acid gas in the furnace was removed by evacuation, heated to 180 °C, and then nitrogen was introduced into the furnace to return to atmospheric pressure, and then the temperature in the furnace was lowered to room temperature to form solder particles.

[0144] (Production Examples 14 to 18) A solder bump forming film was produced and evaluated in the same manner as in Production Example 13, except that the size of the concave portion and the like were changed as described in Table 1. The results are shown in Table 2.

[0145] (Production Example 19) A solder bump forming film was produced and evaluated in the same manner as in Production Example 1, except that the following step c4 was performed instead of step c1. The results are shown in Table 2. Step c4: Formation of solder particles The substrate with solder fine particles disposed in the concave portion in step b1 was put into a formic acid conveyor reflow furnace (manufactured by Heller Industries, Inc., 1913MK), and while being conveyed by the conveyor, it was continuously passed through a nitrogen zone adjusted to 190 °C, a nitrogen and formic acid gas mixed zone, and a nitrogen zone. The nitrogen and formic acid gas mixed zone was passed through in 20 minutes to form solder particles in the concave portion.

[0146] (Production Examples 20 to 24) A solder bump forming film was produced and evaluated in the same manner as in Production Example 19, except that the size of the concave portion and the like were changed as shown in Table 1. The results are shown in Table 2.

[0147]

Table 1

[0148]

Table 2

[0149] <Fabrication of Evaluation Chip with Solder Bumps> Process e1: Preparation of Evaluation Chip Seven types of chips with gold bumps (3.0 × 3.0 mm, thickness: 0.5 mm) shown below were prepared. Chip C1… Area 100 μm × 100 μm, Space 40 μm, Height: 10 μm, Number of Bumps 362 Chip C2… Area 75 μm × 75 μm, Space 20 μm, Height: 10 μm, Number of Bumps 362 Chip C3… Area 40 μm × 40 μm, Space 16 μm, Height: 7 μm, Number of Bumps 362 Chip C4… Area 20 μm × 20 μm, Space 7 μm, Height: 5 μm, Number of Bumps 362 Chip C5… Area 10 μm × 10 μm, Space 6 μm, Height: 3 μm, Number of Bumps 362 Chip C6… Area 10 μm × 10 μm, Space 4 μm, Height: 3 μm, Number of Bumps 362 Chip C7… Area 5 μm × 10 μm, Space 3 μm, Height: 2 μm, Number of Bumps 362

[0150] Process f1: Solder Bump Formation (Without Using Formic Acid Gas) Following the procedures of i) to iii) shown below, solder bumps were formed on the chips with gold bumps (3.0 × 3.0 mm, thickness: 0.5 mm) using the solder bump forming film (Production Example 7) produced in Process c2. i) A glass plate with a thickness of 0.3 mm was placed on a hot plate, and an evaluation chip was placed on the glass plate with the gold bumps facing up. ii) The opening surface side of the recess of the solder bump forming film was turned downward, and the solder bump forming film was arranged so as to be in contact with the gold bump surface of the evaluation chip. Further, a glass plate with a thickness of 0.3 mm was placed on the solder bump forming film, and a stainless steel weight was placed on the glass plate to bring the solder bump forming film into close contact with the gold bumps. iii) A bell-shaped glass cover into which nitrogen gas can be blown was prepared. The sample with the solder bump forming film laminated on the evaluation chip prepared in ii) was covered with this glass cover. Next, nitrogen gas was introduced into the glass cover, and the entire sample was placed in a nitrogen atmosphere. The hot plate of the hot plate was heated to 160 °C and heated for 5 minutes. After that, after returning the hot plate to room temperature, the nitrogen gas was stopped and the atmosphere was released. The top weight, glass plate, and solder bump forming film were removed in this order. Subsequently, the evaluation chip was immersed in a methanol solution, the mobile phase was washed away, and vacuum dried (at 40 °C for 60 minutes) to obtain an evaluation chip with solder bumps.

[0151] <Evaluation of Solder Bumps: Without Using Formic Acid Gas> The evaluation chip obtained through step f1 was fixed on the surface of the SEM observation pedestal, and platinum sputtering was performed on the surface. With an SEM, for 30 gold bumps, the number of solder bumps placed on the gold bumps was counted, and the average number of solder bumps placed on one gold bump was calculated. The results are shown in Table 3. Also, using a laser microscope (manufactured by Olympus Corporation, LEXT OLS5000 - SAF), the height of the solder bumps from the gold bumps was measured, and the average value of 100 was calculated. The results are shown in Table 3.

[0152] Except for using the solder bump forming films of Preparation Examples 8 to 12 instead of the solder bump forming film of Preparation Example 7, solder bump formation and its evaluation were performed in the same manner as above. The evaluation results are shown in Table 3.

[0153] (Comparative Preparation Example 1) A comparative solder bump-forming film having solder particles in the recess was produced in the same manner as in Production Example 8, except that Process d1 (flux placement) was not performed. Solder bump formation and its evaluation were carried out in the same manner as in Process f1, except that this comparative solder bump-forming film was used. The results are shown in Table 3.

[0154]

Table 3

[0155] In Production Examples 7 to 12, solder bumps could be formed on the gold bumps of the evaluation chips, but in Comparative Production Example 1, no solder bumps were observed on the gold bumps of any of the evaluation chips.

[0156] In the recess of Comparative Production Example 1, since there was no fluid phase containing flux, the surface oxide film of the solder particles was not reduced, and wet spreading of the solder particles onto the gold bumps did not occur.

[0157] Since the mobile phase containing the flux component is accommodated in the recess together with the solder particles, heating removes the oxide film on the surface of the solder particles with the flux component and also cleans the surface of the gold bump (electrode). Then, while the solder particles are melting, they are carried to the surface of the gold bump by the mobile phase, and a solder bump can be formed on the gold bump. As shown in FIG. 1, since the mobile phase exists in the recess, the oxide film near the surface of the solder particles facing the gold bump (electrode) is removed by the mobile phase, and the contact between the solder particles and the gold bump is activated. Since heating is performed in a state where the opening surface of the recess is in contact with the gold bump surface, the solder particles can contact the gold bump surface. At this time, due to the presence of the wall surface of the recess, the flow of the solder particles and the flux in the surface direction of the member for forming the solder bump is suppressed, and a solder bump can be formed on the gold bump. Also, for the same reason, it is difficult for the solder particles in adjacent recesses to join together, and a good solder bump can be formed. Although it is necessary to control the wetting spread amount with the gold bump surface according to the heating temperature and time during bump formation, since the solder particles and the flux are housed in the recess and pressed against the gold bump surface, for the above reasons, it is difficult for the solder particles between adjacent ones to bond together, and the likelihood in terms of heating temperature and time is high. Therefore, stable solder bump formation for industrial use is achieved. Although a small amount of the flux component and solder particles were observed in the portion without the gold bump, they could be removed by cleaning the evaluation chip in methanol. The opening surface of the recess also faces the surface of the evaluation chip other than the gold bump, but since the gold bump is higher than the other surfaces, it is difficult for the opening surface of the recess to touch, and it is difficult for the solder particles to move to the evaluation chip side. Also, even if the opening surface of the recess is partially in contact with the evaluation chip side, since there is no metal (electrode) on which the solder spreads, it can be easily removed by subsequent cleaning. Also, as described above, since there are solder particles and flux in the recess, the flow of the solder particles in the surface direction of the member for forming the solder bump is suppressed, and it is difficult to cause short-circuit defects in the gold bump etc.

[0158] When there is no mobile phase as in Comparative Preparation Example 1, even if heated, the surface oxide film of the solder particles cannot be sufficiently reduced, and furthermore, it is difficult to flow the solder particles to the gold bumps (electrodes), making it difficult to stably form solder bumps.

[0159] Step f2: Solder bump formation (using formic acid gas) Following the procedures of i) to iii) shown below, solder bumps were formed on a chip with gold bumps (3.0 × 3.0 mm, thickness: 0.5 mm) using the solder bump formation film (Preparation Example 7) prepared in Step c2. i) A glass plate with a thickness of 0.3 mm was placed on a stainless steel plate with a thickness of 5 mm, and the evaluation chip was placed on the glass plate with the gold bumps facing up. ii) The opening surface side of the recess of the solder bump formation film was turned downward, and it was arranged so that the gold bump surface of the evaluation chip was in contact with the solder bump formation film. Furthermore, a glass plate with a thickness of 0.3 mm was placed on the solder bump formation film, and a stainless steel weight was placed on the glass plate to closely adhere the solder bump formation film to the gold bumps. iii) The stainless steel plate prepared in ii) was placed on the belt conveyor of a formic acid reflow conveyor furnace (Heller Industries Inc. 1936MKV) and flowed at a speed of 40 mm / s. Inside the conveyor furnace, the sample first passed through a nitrogen gas zone. At this time, the oxygen around the sample was removed. Subsequently, it passed through a zone of nitrogen gas heated to 150°C, and further passed through a zone of formic acid gas (4%) at 180°C, and then was introduced into a vacuum chamber set at 160°C. After the vacuum chamber was closed, the inside of the chamber was evacuated for 1 minute, nitrogen gas was introduced to return to atmospheric pressure, and then the sample exited the vacuum chamber and passed through a cooling zone in a nitrogen gas atmosphere to return to room temperature. The top weight, glass plate, and solder bump formation film were removed in that order. Subsequently, the evaluation chip was immersed in a methanol solution, the mobile phase was washed away, and it was vacuum dried (at 40°C for 60 minutes) to obtain an evaluation chip with solder bumps.

[0160] <Evaluation of solder bumps: Using formic acid gas> The evaluation chip obtained through process f2 was fixed on the surface of the pedestal for SEM observation, and platinum sputtering was performed on the surface. Using SEM, for 30 gold bumps, the number of solder bumps placed on the gold bumps was counted, and the average number of solder bumps placed on one gold bump was calculated. The results are shown in Table 3. Also, using a laser microscope (manufactured by Olympus Corporation, LEXT OLS5000 - SAF), the height of the solder bumps from the gold bumps was measured, and the average value of 100 was calculated. The results are shown in Table 4.

[0161] Except for using the solder bump forming films of Preparation Examples 8 to 12 instead of the solder bump forming film of Preparation Example 7, solder bump formation and its evaluation were performed in the same manner as in process f2. The evaluation results are shown in Table 4.

[0162] Except for using the comparative solder bump forming film obtained in Comparative Preparation Example 1, solder bump formation and its evaluation were performed in the same manner as in process f2. The results are shown in Table 4.

[0163]

Table 4

[0164] In Preparation Examples 7 to 12, solder bumps could be formed on the gold bumps. In particular, compared with the case where a formic acid gas atmosphere was not used (Table 3), the number of solder bumps tended to increase. This is presumably because the surface oxide film of the solder particles in the recesses was sufficiently reduced by the flux components contained in the mobile phase and formic acid gas, and the organic substances on the surface of the gold pads were also removed by formic acid gas, making it easier to form solder bumps on the gold bumps. When observing the solder bumps obtained using a formic acid gas atmosphere with a microscope and an electron microscope, there was less spherical distortion than the solder bumps obtained without using a formic acid gas atmosphere. This is presumably because the bubbles in the solder bumps were removed and the low-molecular components of the mobile phase also sufficiently evaporated due to the vacuum state in the vacuum chamber after heating, resulting in the solder bumps becoming spherical with less distortion.

[0165] In Comparative Production Example 1, the formation of solder bumps was confirmed on the gold bumps. However, compared with Production Examples 7 to 12, the number of bumps tended to be small. Even when the same Comparative Production Example 1 was used, when the formic acid gas atmosphere was not provided, the formation of solder bumps was not observed. However, when the formic acid gas atmosphere was provided, the surface oxide films of the solder particles in some of the recesses were removed by the formic acid gas and a certain amount of them was placed on the gold bumps. However, since the side of the recess was pressed against the gold bumps, it is considered that the formic acid gas did not sufficiently remove the surface oxide films of the solder particles in the recesses.

[0166] <Fabrication of Connection Structure> Step g1: Preparation of Evaluation Substrate Seven types of substrates with gold bumps (70×25 mm, thickness: 0.5 mm) shown below were prepared. In addition, lead-out wirings for resistance measurement were also formed on these gold bumps. Substrate D1… Area 100 μm×100 μm, Space 40 μm, Height: 4 μm, Number of Bumps 362 Substrate D2… Area 75 μm×75 μm, Space 20 μm, Height: 4 μm, Number of Bumps 362 Substrate D3… Area 40 μm×40 μm, Space 16 μm, Height: 4 μm, Number of Bumps 362 Substrate D4… Area 20 μm×20 μm, Space 7 μm, Height: 4 μm, Number of Bumps 362 Substrate D5… Area 10 μm×10 μm, Space 6 μm, Height: 3 μm, Number of Bumps 362 Substrate D6… Area 10 μm×10 μm, Space 4 μm, Height: 3 μm, Number of Bumps 362 Substrate D7… Area 5 μm×10 μm, Space 3 μm, Height: 3 μm, Number of Bumps 362

[0167] Step h1: Bonding of Electrodes According to the following procedures i) to iii), using the evaluation chip with solder bumps fabricated in Step f1, it was connected to the evaluation substrate with gold bumps via the solder bumps. i) The evaluation substrate was placed on the lower hot plate of a formic acid reflow furnace (manufactured by Shinko Seiki Co., Ltd., batch-type vacuum soldering apparatus) with the gold bumps facing up. (ii) The solder bump surface of the evaluation chip with solder bumps formed thereon was turned downward, and it was placed so that the solder bumps contacted the gold bump surface of the evaluation substrate and fixed so as not to move. (iii) The formic acid vacuum reflow furnace was operated. After evacuation, the furnace was filled with formic acid gas, the lower hot plate was heated to 180 °C and heated for 5 minutes. Then, after discharging the formic acid gas by evacuation, nitrogen substitution was performed, the lower hot plate was returned to room temperature, and the inside of the furnace was opened to the atmosphere. An appropriate amount of underfill material (CEL series, manufactured by Hitachi Chemical Co., Ltd.) with adjusted viscosity was placed between the evaluation chip and the evaluation substrate. After filling by evacuation, it was cured at 165 °C for 2 hours to fabricate a connection structure of the evaluation chip and the evaluation substrate. The combinations of the respective materials in the connection structure are as follows. (1) Chip C1 / Film for solder bump formation / Substrate D1 (2) Chip C2 / Film for solder bump formation / Substrate D2 (3) Chip C3 / Film for solder bump formation / Substrate D3 (4) Chip C4 / Film for solder bump formation / Substrate D4 (5) Chip C5 / Film for solder bump formation / Substrate D5 (6) Chip C6 / Film for solder bump formation / Substrate D6 (7) Chip C7 / Film for solder bump formation / Substrate D7

[0168] <Evaluation of the connection structure> Regarding a part of the obtained connection structure, a conduction resistance test and an insulation resistance test were performed as follows.

[0169] (Conduction resistance test - Damp heat, steady state, cyclic) Regarding the conduction resistance between the chip with gold bumps (bump) and the substrate with gold bumps (bump), the initial value of the conduction resistance and the values after the damp heat, steady state, cyclic test (left for 100, 500, and 1000 hours under the conditions of temperature 85 °C and humidity 85%) were measured for 20 samples, and their average values were calculated. The conduction resistance was evaluated according to the following criteria from the obtained average values. The results are shown in Table 5. In addition, when the following criteria A or B are satisfied after 1000 hours of the damp heat, steady state, cyclic test, it can be said that the conduction resistance is good. A: The average value of the conduction resistance is less than 2 Ω B: The average value of the conduction resistance is 2 Ω or more and less than 5 Ω C: The average value of the conduction resistance is 5 Ω or more and less than 10 Ω D: The average value of the conduction resistance is 10 Ω or more and less than 20 Ω E: The average value of the conduction resistance is 20 Ω or more

[0170] (Conduction Resistance Test - High Temperature Storage Test) Regarding the conduction resistance between the chip with gold bumps (bumps) and the substrate with gold bumps (bumps), the initial value of the conduction resistance and the values after the high temperature storage test (stored for 100, 500, and 1000 hours under the condition of a temperature of 100 °C) were measured for 20 samples. After the high temperature storage, a drop impact was applied, and the conduction resistance of the samples after the drop impact was measured. The drop impact was generated by screwing the connection structure to a metal plate and dropping it from a height of 50 cm. After the drop, the DC resistance values were measured at the solder joints (4 locations) of the chip corner with the most impact. When the measured value increased by 5 times or more from the initial resistance, it was regarded that breakage occurred, and the evaluation was carried out. In addition, for each sample, 4 measurements were made at 4 locations, for a total of 80 measurements. The results are shown in Table 6. When the following criteria A or B were satisfied after 20 drop times, the solder connection reliability was evaluated as good. A: The number of solder joints with an increase of 5 times or more from the initial resistance was 0. B: The number of solder joints with an increase of 5 times or more from the initial resistance was 1 or more and 5 or less. C: The number of solder joints with an increase of 5 times or more from the initial resistance was 6 or more and 20 or less. D: The number of solder joints with an increase of 5 times or more from the initial resistance was 21 or more.

[0171] (Insulation Resistance Test) Regarding the insulation resistance between the chip electrodes, the initial value of the insulation resistance and the values after the migration test (stored for 100, 500, and 1000 hours under the conditions of a temperature of 60 °C, a humidity of 90%, and an applied voltage of 20 V) were measured for 20 samples. Among all 20 samples, the insulation resistance value was 10 9The ratio of samples with a value of Ω or more was calculated. The insulation resistance was evaluated according to the following criteria from the obtained ratio. The results are shown in Table 7. Note that when the following criteria A or B are satisfied after 1000 hours of the migration test, it can be said that the insulation resistance is good. A: Insulation resistance value 10 9 The ratio of 100% with a value of Ω or more B: Insulation resistance value 10 9 The ratio is 90% or more and less than 100% with a value of Ω or more C: Insulation resistance value 10 9 The ratio is 80% or more and less than 90% with a value of Ω or more D: Insulation resistance value 10 9 The ratio is 50% or more and less than 80% with a value of Ω or more E: Insulation resistance value 10 9 The ratio is less than 50% with a value of Ω or more

[0172]

Table 5

[0173]

Table 6

[0174]

Table 7

[0175] <Fabrication of solder bump forming film> Process i1: Fabrication of evaluation substrate A liquid photosensitive resist (AH series, manufactured by Hitachi Chemical Co., Ltd.) was spin-coated onto a 6-inch silicon wafer to a thickness of 2.3 μm. The photosensitive resist on this silicon wafer was exposed and developed to form an evaluation pattern having recesses with an opening diameter of 3.1 μmφ, a bottom diameter of 2.0 μmφ, and a depth of 2.3 μm (the bottom diameter of 2.0 μmφ is located at the center of the opening diameter of 3.1 μmφ when viewed from the top surface). Note that one of these evaluation patterns has a size of 20 mm × 20 mm, and the aforementioned recesses are arranged in a 10 mm × 10 mm area at the center thereof. The positions of the recesses are arranged at positions (X-direction pitch, Y-direction pitch) relative to the electrode arrangement pattern of the evaluation chip C8 described later, and three alignment marks are also arranged. This was cut into a size of 20 mm × 20 mm using a dicing saw to obtain the evaluation substrate 1. The outline of the evaluation substrate is shown in Table 8.

[0176]

Table 8

[0177] Using the thickness, opening diameter, and pitch of the photosensitive resist as the values shown in Table 8, evaluation substrates 2 to 6 were fabricated.

[0178] <Preparation of Solder Particles> Step j1: Preparation of Solder Particles Through steps a1, b1, and c1, solder bump formation films having solder particles as shown in Preparation Examples 7 to 12 of Table 2 were obtained. An isopropyl alcohol was filled in a stainless steel bath, and the obtained solder bump formation film was immersed therein, and ultrasonic waves of 28 kHz and 600 W were applied for 5 minutes. The solder particles detached from the recesses and were dispersed in the isopropyl alcohol solvent. The solvent in which these solder particles were dispersed was allowed to stand, and the supernatant was discarded. Thereafter, it was filled again with isopropyl alcohol, and after the solder particles were well dispersed, it was allowed to stand. This sedimentation separation operation was performed three times to obtain solder particles 1 to 6 with uniform particle diameters. The outlines of solder particles 1 to 6 are shown in Table 9.

[0179]

Table 9

[0180] (Production Example 25) Step k1: Arrangement of fluidizing agent and solder particles Dodecane and solder particles 1 were placed in a glass bottle with a lid and dispersed by ultrasonic waves. The dispersion liquid was dripped onto the surface of the evaluation substrate 1 of 20 mm × 20 mm fixed on a glass plate, and the surface of the evaluation substrate 1 was rubbed with a urethane squeegee to fill the recesses with the solder particles 1 and dodecane. The excess solder particles 1 and dodecane on the surface of the evaluation substrate 1 were wiped off with a clean cloth, and a solder bump forming film in which the solder particles 1 and dodecane were arranged in the recesses of the evaluation substrate 1 was obtained.

[0181]

Table 10

[0182] (Production Examples 26 to 42) Except that the type of fluidizing agent, solder particles, and the evaluation substrate were set to the combinations shown in Table 10, in the same manner as in Step k1, evaluation solder bump forming films 26 to 42 in which the solder particles and the fluidizing agent were arranged in the recesses were obtained. Note that adipic acid was prepared by putting 20 parts by mass of adipic acid into 90 parts by mass of dihydroterpineol and mixing well to obtain a mobile phase.

[0183] ><Fabrication of Evaluation Chip with Solder Bumps> Step e2: Preparation of evaluation chip Six types of chips with gold bumps (10 mm × 10 mm, thickness: 0.5 mm) shown below were prepared. Chip C8... Size 8 × 4 μm, X-direction pitch 16 μm, Y-direction pitch 8 μm, height: 3 μm, number of bumps 382000 Chip C9... Size 16 μm × 8 μm, X-direction pitch 32 μm, Y-direction pitch 16 μm, height: 5 μm, number of bumps 95700 Chip C10... Size 24 μm × 12 μm, X-direction pitch 48 μm, Y-direction pitch 24 μm, height: 8 μm, number of bumps 42500 Chip C11… Size: 72μm × 36μm, X-direction pitch: 144μm, Y-direction pitch: 72μm, height: 10μm, number of bumps: 4700 Chip C12… Size: 96μm × 48μm, X-direction pitch: 192μm, Y-direction pitch: 96μm, height: 13μm, number of bumps: 2600 Chip C13… Size: 140μm × 70μm, X-direction pitch: 280μm, Y-direction pitch: 140μm, height: 18μm, number of bumps: 1200 Note that three alignment marks are arranged for each of them.

[0184] <Solder bump formation> Process f3: Solder bump formation: Nitrogen atmosphere Following the procedures of i) to iii) shown below, solder bumps were formed on the chip with gold bumps (10 mm × 10 mm, thickness: 0.5 mm) using the evaluation film for solder bump formation 25 fabricated in process k1. i) Chip C8 was fixed on a 30 mm × 30 mm (thickness 0.5 mm) glass plate with the gold bumps facing up. This was suction-fixed to the stage of a flip chip bonder (FC3000: manufactured by Toray). ii) The evaluation substrate 1 of 20 mm × 20 mm was picked up with a heating and pressing head, the alignment marks were read by a camera, the electrode position of chip C8 was opposed to the recess of the evaluation substrate 1, and it was temporarily placed. iii) A bell-shaped glass cover into which nitrogen gas can be blown was prepared. The entire hot plate was covered with this glass cover, and the hot plate was heated to 150°C. The sample prepared in ii) was placed on the hot plate, a stainless steel weight was placed on the uppermost evaluation substrate 1, and it was heated for 3 minutes in a nitrogen atmosphere. Then, the uppermost weight and the evaluation substrate 1 were removed in order. Subsequently, chip C8 was immersed in a methanol solution, the mobile phase was washed away, and it was vacuum dried (at 40°C for 60 minutes) to obtain the evaluation chip 25 with solder bumps.

[0185] <Evaluation of solder bumps: Without using formic acid gas> The evaluation chip 25 obtained through process f1 was fixed on the surface of the pedestal for SEM observation, and platinum sputtering was performed on the surface. Using SEM, for 300 gold bumps, the number of solder bumps formed on the gold bumps was counted, the solder bump formation rate was calculated, and the evaluation was performed according to the following evaluation criteria. The results are shown in Table 11. Note that when the evaluation of the solder bump formation rate meets the criteria of A or B, it can be said to be good. A: The solder bump formation rate is 90% or more B: The solder bump formation rate is more than 80% and less than 90% C: The solder bump formation rate is more than 70% and less than 80% D: The solder bump formation rate is more than 60% and less than 70% E: The solder bump formation rate is less than 60%

[0186] Furthermore, using a laser microscope (manufactured by Olympus Corporation, LEXT OLS5000 - SAF), the height of the solder bumps from the gold bumps was measured, and the average value of 100 was calculated. The results are shown in Table 11.

[0187] Next, except for using the evaluation solder bump formation films 26 - 42 of Production Examples 26 - 42 instead of the evaluation solder bump formation film 25 of Production Example 25, and using chips C8 - 13 corresponding to the positions of the respective gold bumps (electrodes) and recesses, solder bump formation and its evaluation were performed in the same manner as above. The evaluation results are shown in Table 11.

Table 11

[0188] For all of the evaluation chips 25 - 42, solder bumps were sufficiently formed on the gold bumps. The solder bumps were formed only on the electrodes, and there were no solder particles between the electrodes. Since the opening surface of the recess of the solder bump formation film is pressed against the electrode surface, even if there is a flowing phase, the possibility of the melted solder leaking from the electrode surface is low, and solder bumps can be stably formed.

[0189] <Solder Bump Formation> Process f4: Solder bump formation: Formic acid atmosphere Except for replacing step iii) of step f3 with the following method, solder bumps were formed and evaluated using the same method as step f3. The evaluation results are shown in Table 12. iii) A glass plate with the evaluation substrate 1 placed on chip C8 was placed and fixed on the hot plate of a formic acid furnace (manufactured by Shinkou Seiki Co., Ltd.). A stainless steel weight was placed on the evaluation substrate 1. After degassing the furnace under vacuum, it was treated at 150 °C for 3 minutes in a formic acid atmosphere and then returned to atmospheric pressure. Subsequently, the top weight and the evaluation substrate 1 were removed in sequence. Subsequently, chip C8 was immersed in a methanol solution, the mobile phase was washed away, and it was vacuum dried (at 40 °C for 60 minutes) to obtain an evaluation chip 43 with solder bumps.

[0190]

Table 12

[0191] Using the method of step f4, solder bumps were formed in the combinations shown in Table 12 to obtain evaluation chips 44 to 60. The evaluation results conducted in the same manner as above are shown in Table 12.

[0192] For evaluation chips 43 to 60, good solder bumps could be formed in all cases. Since a reducing atmosphere was created by formic acid, good results were obtained.

[0193] <Solder Bump Formation> Step f5: Solder Bump Formation: Vacuum Pressurization Except for replacing step iii) of step f3 with the following method, solder bumps were formed and evaluated using the same method as step f3. The evaluation results are shown in Table 13. iii) A glass plate with the evaluation substrate 1 placed on chip C8 was placed on the carrier film of a vacuum pressurization laminator (MVL - 500: manufactured by Nippon Steel Corporation). The upper and lower hot plate temperatures were set to 145 °C, and it was treated at a pressure of 0.5 MPa for a pressurization time of 3 s. Subsequently, the evaluation substrate 1 was removed. Subsequently, chip C8 was immersed in a methanol solution, the mobile phase was washed away, and it was vacuum dried (at 40 °C for 60 minutes) to obtain an evaluation chip 61 with solder bumps. The results are shown in Table 13.

[0194]

Table 13

[0195] Using the method of process f5, solder bumps were formed in the combinations shown in Table 13, and evaluation chips 62 to 78 were obtained. The evaluation results conducted in the same manner as above are shown in Table 13.

[0196] For the evaluation chips 61 to 78, good solder bumps could be formed. Due to the vacuum pressurization, the pressure was uniformly applied in the plane, resulting in good results.

[0197] <Fabrication of Evaluation Chip with Solder Bump> Process e3: Preparation of Evaluation Chip Six types of chips with copper bumps (10 mm × 10 mm, thickness: 0.5 mm) shown below were prepared. Chip C14… Size 8 × 4 μm, X-direction pitch 16 μm, Y-direction pitch 8 μm, height: 3 μm, number of bumps 382000 Chip C15… Size 16 μm × 8 μm, X-direction pitch 32 μm, Y-direction pitch 16 μm, height: 5 μm, number of bumps 95700 Chip C16… Size 24 μm × 12 μm, X-direction pitch 48 μm, Y-direction pitch 24 μm, height: 8 μm, number of bumps 42500 Chip C17… Size 72 μm × 36 μm, X-direction pitch 144 μm, Y-direction pitch 72 μm, height: 10 μm, number of bumps 4700 Chip C18… Size 96 μm × 48 μm, X-direction pitch 192 μm, Y-direction pitch 96 μm, height: 13 μm, number of bumps 2600 Chip C19… Size 140 μm × 70 μm, X-direction pitch 280 μm, Y-direction pitch 140 μm, height: 18 μm, number of bumps 1200 Note that three alignment marks are arranged in each.

[0198] <Solder Bump Formation> Process f6: Solder Bump Formation: Vacuum Pressurization Except for replacing step iii) of step f3 with the following method, solder bumps were formed and evaluated in the same manner as in step f3. The evaluation results are shown in Table 14. iii) A glass plate with the evaluation substrate 1 placed on chip C14 was placed on the carrier film of a vacuum pressure laminator (MVL-500, manufactured by Nippon Steel Corporation). The upper and lower heating plate temperatures were set to 150 °C, and the treatment was carried out at a pressure of 0.5 MPa and a pressurization time of 10 s. Subsequently, the evaluation substrate 1 was removed. Then, chip C14 was immersed in a methanol solution, the mobile phase was washed away, and it was vacuum dried (at 40 °C for 60 minutes) to obtain an evaluation chip 79 with solder bumps.

[0199]

Table 14

[0200] Using the method of step f6, solder bumps were formed in the combinations shown in Table 14 to obtain evaluation chips 80 to 96. The evaluation results obtained in the same manner as above are shown in Table 14.

[0201] Good solder bump formation was also achieved for the evaluation chips 79 to 96 having Cu bumps (electrodes).

[0202] <Fabrication of Connection Structure> Step g2: Preparation of Evaluation Substrate Six types of substrates with Au bumps (40 × 40 mm, thickness: 0.5 mm) shown below were prepared. The arrangement of these Au bumps is such that each is in a position relative to the Au bumps of chips C8 to C13, and there are three alignment marks for alignment. Note that lead-out wirings for resistance measurement are also formed on these Au bumps. Substrate D8… Corresponding chip: Chip C8 / Size 8 × 4 μm, X-direction pitch 16 μm, Y-direction pitch 8 μm, Height: 3 μm, Number of bumps 382000 Substrate D9… Corresponding chip: Chip C9 / Size 16 μm × 8 μm, X-direction pitch 32 μm, Y-direction pitch 16 μm, Height: 5 μm, Number of bumps 95700 Substrate D10... Corresponding chip: Chip C10 / Size 24μm × 12μm, X-direction pitch 48μm, Y-direction pitch 24μm, Height: 8μm, Number of bumps 42500 Substrate D11... Corresponding chip: Chip C11 / Size 72μm × 36μm, X-direction pitch 144μm, Y-direction pitch 72μm, Height: 10μm, Number of bumps 4700 Substrate D12... Corresponding chip: Chip C12 / Size 96μm × 48μm, X-direction pitch 192μm, Y-direction pitch 96μm, Height: 13μm, Number of bumps 2600 Substrate D13... Corresponding chip: Chip C13 / Size 140μm × 70μm, X-direction pitch 280μm, Y-direction pitch 140μm, Height: 18μm, Number of bumps 1200

[0203] Process h2: Bonding of electrodes Following the procedures of i) to iii) shown below, the evaluation chip with solder bumps fabricated in process f5 was used to connect to the evaluation substrate with gold bumps via the solder bumps. i) The substrate with gold bumps formed was fixed to the stage of a flip chip bonder (FC3000: manufactured by Toray Industries, Inc.). The evaluation chip with solder bumps formed was picked up by the heating and pressing head and placed at a position where the gold bumps faced each other from the alignment marks. ii) The substrate with the evaluation chip placed on it was placed on the lower hot plate of a formic acid reflow furnace (manufactured by Shinko Seiki Co., Ltd., batch type vacuum soldering device), and a stainless steel weight was placed on top of the evaluation chip. iii) The formic acid vacuum reflow furnace was operated. After evacuation, formic acid gas was filled. The lower hot plate was heated to 150°C and heated for 5 minutes. Then, after evacuating to discharge the formic acid gas, nitrogen substitution was performed. The lower hot plate was returned to room temperature, and the furnace was opened to the atmosphere. An appropriate amount of underfill material (CEL series, manufactured by Hitachi Chemical Co., Ltd.) with adjusted viscosity was placed between the evaluation chip and the evaluation substrate. After filling by evacuation, it was cured at 125°C for 4 hours to fabricate the connection structure of the evaluation chip and the evaluation substrate.

[0204] <Evaluation of the connection structure> For a part of the obtained connection structure, a conduction resistance test and an insulation resistance test were conducted in the same manner as in step h1. The results are shown in Tables 15, 16, and 17.

[0205]

Table 15

[0206]

Table 16

[0207]

Table 17

[0208] <Fabrication of Connection Structure> Step g3: Preparation of Evaluation Substrate Six types of substrates with copper bumps (40×40 mm, thickness: 0.5 mm) shown below were prepared. The arrangement of these Cu bumps is such that each is in a position relative to the Cu bumps of chips C14 to C19, and there are three alignment marks for alignment. In addition, lead-out wirings for resistance measurement are also formed on these Cu bumps. Substrate D14… Corresponding chip: Chip C14 / Size 8×4μm, X-direction pitch 16μm, Y-direction pitch 8μm, Height: 3μm, Number of bumps 382000 Substrate D15… Corresponding chip: Chip C15 / Size 16μm×8μm, X-direction pitch 32μm, Y-direction pitch 16μm, Height: 5μm, Number of bumps 95700 Substrate D16… Corresponding chip: Chip C16 / Size 24μm×12μm, X-direction pitch 48μm, Y-direction pitch 24μm, Height: 8μm, Number of bumps 42500 Substrate D17… Corresponding chip: Chip C17 / Size 72μm×36μm, X-direction pitch 144μm, Y-direction pitch 72μm, Height: 10μm, Number of bumps 4700 Substrate D18... corresponding chip: Chip C18 / size 96μm × 48μm, X-direction pitch 192μm, Y-direction pitch 96μm, height: 13μm, number of bumps 2600 Substrate D19... corresponding chip: Chip C19 / size 140μm × 70μm, X-direction pitch 280μm, Y-direction pitch 140μm, height: 18μm, number of bumps 1200

[0209] Process h3: Bonding of electrodes Following the procedures of i) to iii) shown below, using the evaluation chip with solder bumps fabricated in process f6, it was connected to the evaluation substrate with copper bumps via the solder bumps. i) The evaluation substrate was set on a spin coater (SC-308S manufactured by Oshikane Co., Ltd.), and 0.5 ml of flux (WHS-003C: manufactured by Arakawa Chemical Industries, Ltd.) was dropped onto the surface where the Cu bumps were formed. It was processed at a rotation speed of 500 rpm for 10 s and then at 1000 rpm for 3 s to form a thin-film flux layer. ii) The evaluation substrate was fixed to the stage of a flip chip bonder (FC3000: manufactured by Toray Industries, Inc.). The evaluation chip with solder bumps formed was picked up by the heating and pressurizing head and placed at a position where the bumps faced each other from the alignment marks. The substrate with the evaluation chip placed on it was placed on the lower hot plate of a formic acid reflow furnace (manufactured by Shinko Seiki Co., Ltd., batch-type vacuum soldering device), and a stainless steel weight was placed on top of the evaluation chip. iii) The formic acid vacuum reflow furnace was operated. After evacuation, it was filled with formic acid gas, the temperature of the lower hot plate was raised to 160 °C, and it was heated for 3 minutes. Then, after evacuating to discharge the formic acid gas, nitrogen substitution was performed, the temperature of the lower hot plate was returned to room temperature, and the furnace interior was opened to the atmosphere. An appropriate amount of underfill material (CEL series, manufactured by Hitachi Chemical Co., Ltd.) with adjusted viscosity was placed between the evaluation chip and the evaluation substrate. After filling by evacuation, it was cured at 125 °C for 4 hours to fabricate a connection structure of the evaluation chip and the evaluation substrate.

[0210] <Evaluation of the connection structure> For a part of the obtained connection structure, a conduction resistance test and an insulation resistance test were conducted in the same manner as in process h1. The results are shown in Tables 18, 19, and 20.

[0211]

Table 18

[0212]

Table 19

[0213]

Table 20

[0214] Even when Cu electrodes were joined through solder bumps formed on the Cu electrodes, stable connection characteristics were shown.

Explanation of Signs

[0215] 1… solder particle, 1A… solder bump, 1B… solder layer, 2… substrate, 3… electrode, 4… other substrate, 5… other electrode, 10… member for forming solder bump, 20… electrode substrate with solder bump, 30… connection structure, 60… base body, 62… recess, 111… fine solder particle, F… fluidizing agent, 600… base body, 601… base layer, 602… recess layer.

Claims

1. A method for manufacturing a solder paste comprising: a substrate having a plurality of recesses; and solder particles and a flow agent in the recesses; The solder bump forming member has an average particle size of 1 to 35 μm and a CV value of 20% or less.

2. 2. The member for forming a solder bump according to claim 1, wherein the fluidizing agent comprises at least one selected from the group consisting of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, benzoic acid, and malic acid.

3. 3. The member for forming a solder bump according to claim 1, wherein a flat portion is formed on a part of the surface of the solder particle.

4. 4. The member for forming a solder bump according to claim 1, wherein the distance between adjacent recesses is 0.1 times or more the average particle diameter of the solder particles.

5. A front end process of preparing a substrate having a plurality of recesses, as well as solder particles and a flow agent; a disposing step of disposing the solder particles and the fluidizing agent in the recess; The method for manufacturing a solder bump forming member includes the steps of:

6. 6. The method according to claim 5, wherein the solder particles have an average particle size of 1 to 35 μm and a CV value of 20% or less.

7. A preparation step of preparing a substrate having a plurality of recesses and solder particles; a receiving step of receiving at least a portion of the solder particles in the recess; a fusing step of fusing the solder particles contained in the recesses to form solder particles in the recesses; an injection step of disposing a fluidizing agent in the recesses in which the solder particles are formed; The method for manufacturing a solder bump forming member includes the steps of:

8. The manufacturing method according to claim 7, wherein the solder particles have an average particle size of 1 to 35 μm and a CV value of 20% or less.

9. The manufacturing method according to claim 7 or 8, wherein the C.V. value of the solder fine particles exceeds 20%.

10. 10. The manufacturing method according to claim 7, further comprising a reduction step of exposing the solder particles contained in the recess to a reducing atmosphere before the fusing step.

11. The manufacturing method according to claim 7, wherein in the fusing step, the solder fine particles are fused in a reducing atmosphere.

12. A preparation step of preparing the solder bump forming member according to any one of claims 1 to 4 and a substrate having a plurality of electrodes; a positioning step of placing the surface of the solder bump forming member having the recessed portion and the surface of the substrate having the electrode in contact with each other; a heating step of heating the solder particles to a temperature equal to or higher than the melting point of the solder particles; A method for manufacturing an electrode substrate with solder bumps, comprising:

13. 13. The method according to claim 12, wherein in the heating step, the solder particles are heated to a temperature equal to or higher than a melting point of the solder particles while the solder bump forming member and the substrate are in contact with each other under pressure.

14. The manufacturing method according to claim 12 or 13, further comprising a reduction step of exposing the solder particles to a reducing atmosphere before the placing step.

15. The manufacturing method according to claim 12, further comprising a reduction step of exposing the solder particles to a reducing atmosphere after the placing step and before the heating step.

16. The manufacturing method according to any one of claims 12 to 15, wherein in the heating step, the solder particles are heated to a temperature equal to or higher than the melting point of the solder particles in a reducing atmosphere.

17. The manufacturing method according to any one of claims 12 to 16, further comprising a removing step of removing the solder bump forming member from the substrate after the heating step.

18. The method of claim 17 , further comprising, after the removing step, a cleaning step of removing the solder particles not bonded to the electrodes.

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