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

Abstract

A solder bump forming member comprising a base having a plurality of recesses, and solder particles and a fluidizer that are located inside the recesses, the solder bump forming member being such that the average particle diameter of the solder particles is 1-35 µm, and the C.V. value is 20% or less.

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 technology]

[0002] A solder ball arrangement sheet is known that is characterized by being composed of a mask having a plurality of solder ball insertion holes arranged in a predetermined pattern, solder balls accommodated in the insertion holes, and an adhesive that holds the solder balls in the insertion holes (see, for example, Patent Document 1).

[0003] A method for producing a sheet for forming solder bumps, which holds solder balls or solder powder in predetermined positions, is known (see, for example, Patent Document 2), which includes the following steps. A. preparing a sheet on one side having a number of depressions in place with the bottom surface composed of an adhesive; B. filling each depression in the sheet with solder powder so that the solder powder is adhered and held by the adhesive on the bottom surface of the depression; C. removing any solder powder from the sheet that is not held by the adhesive; and D. coating the solder powder in the depressions of the sheet.

[0004] A method is known in which solder balls placed in grooves are transferred to the surface of an adhesive roll, and then the solder balls are transferred to an adhesive on an electrode, thereby forming solder bumps on the electrode (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-080024 A [Patent Document 2] International Publication No. 2006 / 043377 [Patent Document 3] JP 2017-157626 A Summary of the Invention [Problem to be solved by the invention]

[0006] The transfer sheet and manufacturing method shown in Patent Documents 1 and 2 require an adhesive layer to hold the solder particles. Therefore, the solder is melted and unified by heating above the solder melting point, and when the solder is transferred to the electrode, the adhesive layer components may soften, melt, or decompose and become impurities. The presence of impurities between the solder and the electrode may hinder stable formation of the solder bumps. When removing these impurities after transferring the solder bumps to the electrodes, the substrate and semiconductor package on which the electrodes are formed are exposed to a cleaning solution, which may result in 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, the solder balls (particles) are placed on the electrodes via an adhesive, so there is a risk that adhesive components will remain on the surface of the solder balls, causing problems with bonding. In addition, while it is possible to control the thickness of the adhesive and the unevenness of the adhesive surface when the size of the solder balls is about 100 μm, it becomes more difficult as the size decreases to 50 μm, 30 μm, etc. Therefore, if solder balls (particles) smaller than 30 μm are transferred or moved via an adhesive, it becomes difficult to increase the transfer rate.

[0008] In addition, a transfer sheet is known in which solder balls (particles) are arranged uniformly on the surface of a substrate with an adhesive interposed therebetween while in contact with each other. It is said that the solder ball surface of this transfer sheet is pressed against a substrate on which electrodes are formed and heated to transfer the solder balls onto the electrodes, and then bumps can be formed by reflow. However, the inventors' investigations revealed that when the electrode spacing becomes narrow, the solder bridges between the electrodes, causing short-circuiting defects. Since adjacent solder balls are in contact with each other, it is believed that the solder melts and coalesces due to the heat applied when transferring to the electrodes, resulting in the formation of portions that span the adjacent electrodes. With a solder transfer sheet in which solder particles are arranged uniformly while in contact with each other in this way, it is currently difficult to form solder bumps without short circuits when the electrode spacing is on the order of several microns.

[0009] The present invention has been made in view of the above circumstances, and aims to provide a solder bump forming member and a manufacturing method thereof that are useful for manufacturing a connection structure that is excellent in both insulation reliability and conduction reliability even if the connection points of circuit members to be electrically connected to each other are very small. Another aim of the present invention is to provide a manufacturing method of an electrode substrate with solder bumps using the member. [Means for solving the problem]

[0010] One aspect of the present invention relates to a member for forming a solder bump, comprising a base having a plurality of recesses, and solder particles and a fluidizing agent in the recesses, the solder particles having an average particle size of 1 to 35 μm and a CV value of 20% or less.

[0011] The above-mentioned solder bump forming member is useful for producing a connection structure having excellent insulation reliability and conduction reliability even if the connection points of circuit members to be electrically connected to each other are very small.

[0012] In one embodiment of the solder bump forming member, the fluidizing agent 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.

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

[0014] In one embodiment 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 member for forming a solder bump, comprising: a pre-processing step of preparing a base having a plurality of recesses, as well as solder particles and a fluidizing agent; and an arrangement 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 member for forming a solder bump, comprising: a preparation step of preparing a base having a plurality of recesses and solder particles; a storage step of accommodating at least some of the solder particles in the recesses; a fusion step of fusing the solder particles contained in the recesses to form solder particles in the recesses; and an injection step of placing a fluidizing agent in the recesses in which the solder particles have been formed.

[0017] In one embodiment of the method for producing a solder bump forming member, the solder particles may have an average particle size of 1 to 35 μm and a CV value of 20% or less.

[0018] In one embodiment of the method for producing a solder bump forming member, the CV value of the solder fine particles may exceed 20%.

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

[0020] In one embodiment of the method for producing a solder bump-forming member, in the fusing 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, comprising: a preparation step of preparing the above-mentioned solder bump forming member and a substrate having a plurality of electrodes; an arrangement step of bringing a surface of the solder bump forming member having a recess and a surface of the substrate having electrodes into contact with each other; 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 the heating step in one embodiment of the method for producing 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 in contact with each other under pressure.

[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 prior to the placement 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 placing step and before the heating step.

[0025] In the heating step in one embodiment of the method for producing 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 producing an electrode substrate with solder bumps may further include, after the heating step, a removing step of removing the solder bump formation member from the substrate.

[0027] One embodiment of the method for manufacturing an electrode substrate with solder bumps may further include, after the removing step, a cleaning step for removing solder particles that are not bonded to the electrodes. Effect of the Invention

[0028] According to the present invention, even if the connection portions of circuit members to be electrically connected to each other are minute, it is possible 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. 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] FIG. 1 is a cross-sectional view schematically showing a member for forming solder bumps according to an embodiment. [Diagram 2] FIG. 2(a) is a view of solder particles seen from the side opposite to the opening of the recess in FIG. 1, and FIG. 2(b) is a view showing distances X and Y (where Y < X) between opposite sides when a rectangle circumscribing the projection image of the solder particles is created by two pairs of parallel lines. [Diagram 3] FIG. 3(a) is a plan view schematically showing an example of a substrate, and FIG. 3(b) is a cross-sectional view taken along line Ib-Ib in FIG. 3(a). [Figure 4] FIGS. 4(a) to 4(h) are cross-sectional views schematically showing examples of the cross-sectional shape of the recesses of the substrate. [Diagram 5] FIG. 5 is a cross-sectional view schematically showing a state in which solder fine particles are accommodated in the recesses of the substrate. [Figure 6] 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. [Figure 7] FIGS. 7(a) and 7(b) are cross-sectional views schematically showing an example of the manufacturing process of a connection structure. [Figure 8] FIG. 8 is a cross-sectional view schematically showing an example of a substrate.

Embodiments for Carrying Out the Invention

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

[0031] <Solder bump forming materials> In one embodiment, a solder bump forming member comprises a base having a plurality of recesses, solder particles and a fluidizing agent in the recesses, the solder particles having an average particle size of 1 to 35 μm and a CV value of 20% or less.

[0032] FIG. 1 is a cross-sectional view showing a schematic diagram of a solder bump forming member according to an embodiment. The solder bump forming member 10 includes a base 60 having a plurality of recesses 62, and solder particles 1 and a fluidizing agent F in the recesses 62. In a given longitudinal section of the solder bump forming member 10, each solder particle 1 is arranged so as to be aligned in the lateral direction (left-right direction in FIG. 1) while being spaced apart from an adjacent solder particle 1. The solder particles 1 may be in contact with the side and / or bottom surface of the recess 62. The fluidizing agent F may be present between the solder particles 1 and the bottom surface of the recess 62. The solder bump forming member may be in the form of a film (solder bump forming film), a sheet (solder bump forming sheet), 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. 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 even more preferably 5 μm or more.

[0034] The average particle diameter of the solder particles 1 can be measured using various methods suited to the size. For example, methods such as dynamic light scattering, laser diffraction, centrifugal sedimentation, electrical sensing zone method, and resonance mass measurement method can be used. Furthermore, a method of measuring the particle size from an image obtained by an optical microscope, an electron microscope, or the like can be used. Specific devices include a flow type particle image analyzer, a microtrack, and a Coulter counter. The average particle diameter of the solder particles 1 can be the diameter of a circle equivalent to the projected area (the diameter of a circle having an area equal to the projected area of ​​the particle) when the solder particles 1 are observed from a direction perpendicular to the main surface of the solder bump forming member 10.

[0035] From the viewpoint of realizing better conductive reliability and insulating reliability, the CV value of the solder particles 1 is preferably 20% or less, more preferably 10% or less, and even more preferably 7% or less. The lower limit of the CV value of the solder particles 1 is not particularly limited. For example, the CV value of the solder particles 1 may be 1% or more, or 2% or more.

[0036] The CV value of solder particle 1 is calculated by dividing the standard deviation of the particle diameters measured by the above-mentioned method by the average particle diameter, and multiplying the result by 100.

[0037] A flat portion may be formed on part of the surface of the solder particle. Fig. 2(a) is a view of the solder particle 1 viewed from the side opposite the opening of the recess 62 in Fig. 1. The solder particle 1 has a shape in which a flat portion 11 of diameter A is formed on part of the surface of a sphere having a diameter B. Note that the solder particle 1 shown in Figs. 1 and 2(a) has the flat portion 11 because the bottom of the recess 62 is flat, but if the bottom of the recess 62 has a shape other than flat, it will have a surface of a different shape 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, the surface other than the flat portion 11 is preferably spherical crown-shaped. That is, the solder particle 1 may have a flat portion 11 and a 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, greater than 0.01 and less than 1.0 (0.01 < A / B < 1.0), and may also 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 opposite sides are X and Y (where Y < X), the ratio (Y / X) of Y to X may be greater than 0.8 and less than 1.0 (0.8 < Y / X < 1.0), and may also be 0.9 or more and less than 1.0. Such solder particles 1 can be said to be particles 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] Figure 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 solder particles 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 particles.

[0041] 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 listed below. · 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 particles 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 listed below. · 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% by mass, Ag 3.0% by mass, melting point 145°C)

[0043] The above tin alloy or indium alloy can be selected depending on the application (temperature at the time of connection) of the solder particles 1. For example, when the solder particles 1 are used for low-temperature fusion, an In-Sn alloy or an Sn-Bi alloy may be used, and in this case, fusion can be performed at 150° C. or less. When a material with a high melting point, such as an Sn-Ag-Cu alloy or an Sn-Cu alloy, is used, high reliability can be maintained even after exposure to high temperatures.

[0044] The solder particles 1 may contain one or more elements selected from Ag, Cu, Ni, Bi, Zn, Pd, Pb, Au, P, and B. Of these elements, the solder particles 1 may contain Ag or Cu for the following reasons: When the solder particles 1 contain Ag or Cu, the melting point of the solder particles 1 can be lowered to about 220° C., and the bonding strength with the electrodes is further improved, making it easier to obtain better electrical connection reliability.

[0045] The Cu content of the solder particles 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, better solder connection reliability is easily achieved. When the Cu content is 10 mass% or less, the solder particles 1 tend to have a low melting point and excellent wettability, and as a result, the connection reliability of the joints formed by the solder particles 1 tends to be good.

[0046] The Ag content of the solder particles 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, better solder connection reliability is easily achieved. When the Ag content is 10 mass% or less, the solder particles 1 tend to have a low melting point and excellent wettability, and as a result, the connection reliability of the joints formed by the solder particles 1 tends to be good.

[0047] (Superplasticizer) The fluidizer F has the effect of flowing as a fluid phase during reflow and pushing the solder particles 1 from the recesses 62 toward the electrode side. The fluidizer F may be a flux, an organic solvent, etc. The flux dissolves oxides on the solder particle surfaces and the electrode surfaces and improves the wettability of the solder to the electrode.

[0048] As the fluidizer F, various organic solvents can be used. The boiling point of the fluidizer F may be higher than the melting point of the solder. When the electrode and the recess are placed facing each other and heated, the fluidizer F flows in the recess, and the solder particles also flow with the flow of the fluidizer F. The flow of the fluidizer F and the solder particles makes it easier for the electrode surface and the solder particles to come into contact with each other, and as a result, the formation of the solder bump is promoted. Therefore, when the solder bump is formed, at least a heating temperature higher than the melting point of the solder particles, higher than the softening point or melting point of the fluidizer F, and lower than the boiling point of the fluidizer F is passed through, the solder bump is easily formed on the electrode. After the solder bump is sufficiently formed, the heating temperature is raised to the boiling point of the fluidizer F or higher, and the residue derived from the fluidizer F on the substrate surface and the electrode surface can be reduced.

[0049] Examples of organic solvents that can be used for the fluidizing agent F include 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), and nonadecane (boiling point: 330°C). These aliphatic hydrocarbons are non-polar and do not have the ability to reduce the metals used in the solder and electrodes such as Au and Cu. However, they can be appropriately selected as a solvent having a boiling point higher than the melting point of the solder, and have the function of causing the solder particles to flow when heated, bringing the solder particles into contact with the electrode surface.

[0050] Examples of various organic solvents that can be used for the 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, and isobornylcyclohexanol (MTPH); 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, diethylene glycol butyl ether, propylene glycol propyl ether, and dipropylene glycol. ethers such as glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, dipropylene glycol dimethyl ether, tripropylene glycol methyl ether, and tripropylene glycol dimethyl ether; 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, and propylene carbonate; acid amides such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide; aliphatic hydrocarbons such as cyclohexane, octane, nonane, decane, and undecane; aromatic hydrocarbons such as benzene, toluene, and xylene; mercaptans having an alkyl group having 1 to 18 carbon atoms; and mercaptans having a cycloalkyl group having 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. Other examples of organic solvents include alicyclic amines such as monoalkylamines, dialkylamines, trialkylamines, alkanolamines, cyclohexylamines, and dicyclohexylamines, and aromatic amines such as diphenylamines and triphenylamines. Examples of organic solvents include ethylenediethanolamine, n-butyldiethanolamine, diethanolamine, and N,N-bis(2-hydroxyethyl)isopropanolamine.

[0051] As an organic solvent that can be used as the fluidizing agent F, a glycol ether-based solvent can also be used. For example, solvents having a boiling point of 200°C or less include dipropylene glycol monomethyl ether, propylene glycol monobutyl ether, diethylene glycol dimethyl ether, ethylene glycol monoallyl ether, and ethylene glycol monoisopropyl ether. Solvents having a boiling point of more than 200°C include 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, and tetraethylene glycol dimethyl ether.

[0052] Fluxes that can be used as the fluidizing agent F include those generally used for solder joints. The flux can be appropriately selected according to the composition of the solder particles, the melting point, the surface state, the heating and atmospheric conditions during transfer, etc. Examples include 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, and rosin. These may be used alone or in combination of two or more.

[0053] The molten salt may be ammonium chloride, etc. The organic acid may be lactic acid, citric acid, stearic acid, glutamic acid, glutaric acid, etc. The organic acid that may be used in the flux may be, for example, an organic acid having 8 to 16 carbon atoms. Examples of the organic acid having 8 to 16 carbon atoms include 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, ethylnonanoic acid, propyloctanoic acid, butylheptanoic acid, lauric acid, methylundecanoic acid, ethyldecanoic acid, propylnonanoic acid, butyloctanoic acid, Saturated fatty acids such as 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, hexyloctanoic acid, pentadecanoic acid, methyltetradecanoic acid, ethyltridecanoic acid, propyldodecanoic acid, butylundecanoic acid, pentyldecanoic acid, hexylnonanoic acid, palmitic acid, methylpentadecanoic acid, ethyltetradecanoic acid, propyltridecanoic acid, butyldodecanoic acid, pentylundecanoic acid, hexyldecanoic acid, heptylnonanoic acid, methylcyclohexanecarboxylic acid, ethylcyclohexanecarboxylic acid, propylcyclohexanecarboxylic acid, butylcyclohexanecarboxylic acid, pentylcyclohexanecarboxylic acid, hexylcyclohexanecarboxylic acid, heptylcyclohexanecarboxylic acid, octylcyclohexanecarboxylic acid, and nonylcyclohexanecarboxylic acid; octene unsaturated fatty acids such as benzoic acid, nonenoic acid, methylnonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, myristoleic acid, pentadecenoic acid, hexadecenoic acid, palmitoleic acid, and sapienic acid; and 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, and nonylbenzoic acid.The organic acid may be used alone or in combination of two or more. Examples of rosin include activated rosin and non-activated rosin. Rosin is a rosin containing abietic acid as the main component. By using an organic acid or rosin having two or more carboxyl groups as the flux, the effect of further increasing the reliability of conduction between electrodes is achieved.

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

[0055] Examples of fluxes 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.), and malic acid (melting point 130° C.), etc. 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 fluidizer F present in the recess 62 is not particularly limited, but may be 1 to 50 parts by mass, 1 to 20 parts by mass, or 20 to 50 parts by mass with respect to 100 parts by mass of the solder particles 1 from the viewpoint of easily obtaining an appropriate flow action, flux effect, etc. The fluidizer F may be a mixture with a solvent or a resin material. As the solvent, the above-mentioned various organic solvents can be used. If it is a mixture, the concentration of the fluidizer F can be appropriately adjusted according to the solder particles 1. In order for the mixture to push the solder particles 1 onto the electrode during reflow, it is preferable to adjust the softening point or melting point so that the fluidity of the mixture is increased by heating. If the softening point or melting point is higher than room temperature, the solder particles 1 are less likely to fall off the recess 62 at room temperature, and handling before the solder bump formation process is easier. Examples of the solvent constituting the mixture include high boiling point solvents. After the solder particles 1 are flowed onto the electrode, the high boiling point solvent volatilizes by reheating, so it is less likely to remain on the electrode. The solvent may be an alcohol-based solvent, etc. If the solvent is an alcohol-based solvent, it is possible to exhibit reducing properties.

[0057] (Base) Materials constituting the base 60 include inorganic materials such as silicon, various ceramics, glass, metals such as stainless steel, and organic materials such as various resins. Among these, the base 60 may be a material having heat resistance that does not change at the melting temperature of the solder particles. The base 60 may also be a material having heat resistance that does not change even at the temperature at which the solder particles are melted. The base 60 may also be a material that does not change by alloying or reacting with the material constituting the solder particles. The recesses 62 of the base 60 can be formed by known methods such as cutting, photolithography, and imprinting. In particular, the imprinting method allows the recesses 62 to be formed in an accurate size in a short process.

[0058] The surface of the substrate 60 may have a coating layer. In order to expand the selection of materials that can be used for the substrate 60, the coating layer may be made of a material that is difficult or does not alloy with the material that constitutes the solder fine particles. The coating layer may be made of an inorganic or organic material. The coating layer may be made of an inorganic material having a strong oxide layer on the surface of aluminum, chromium, etc., an oxide such as titanium oxide, a nitride such as boron nitride, a carbon-based material such as diamond-like carbon, diamond, graphite, etc., a fluororesin, a highly heat-resistant resin such as polyimide, etc. 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] The coating layer can be formed by laminating, dipping in a solution, coating, painting, impregnation, sputtering, plating, or the like.

[0060] From the viewpoint of making it easier to set the conditions for the transfer process, the material of the base 60 may be a material whose physical properties are similar to or the same as those of the electrodes to which the solder particles are transferred and the substrate on which the electrodes are formed. For example, if the material has a similar or the same coefficient of thermal expansion (CTE), misalignment is less likely to occur when the solder particles are transferred.

[0061] The substrate 60 may be provided with an alignment mark. The alignment mark may be read by a camera. The substrate having the electrodes may also have an alignment mark. By providing the alignment marks of the substrate 60 and the substrate having the electrodes, when transferring the solder particles onto the electrodes, a camera mounted on an alignment device can read the alignment marks on the substrate 60 and the alignment marks on the substrate having the electrodes, and it becomes possible to accurately grasp the position of the recess 62 having the solder particles and the position of the electrode to which the solder particles are transferred. In addition, by providing the alignment marks of the substrate 60 and the substrate having the electrodes, the solder particles can be transferred onto the electrodes with good positional accuracy.

[0062] It is sufficient that there is one or more alignment marks on the substrate 60. If there are two or more alignment marks, the positional accuracy will be increased.

[0063] A specific configuration of the base 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 polymeric material, and a thermoplastic, thermosetting, or photosetting material may be used. By using an organic material, the range of physical properties can be expanded, and the substrate 60 can be easily formed according to the purpose. For example, if the material is an organic material, the substrate 60 (including the recess 62) can be easily bent or stretched. If the material is an organic material, various methods can be used to form the recess 62. Methods for forming the recess 62 include imprinting, photolithography, cutting, and laser processing. In particular, the imprinting method can be used to press a mold having a desired shape against the substrate 60 made of an organic material to form an arbitrary shape on the surface. A convex pattern is formed in the mold, and the mold is pressed against the substrate 60 made of an organic material to form the recess 62 having the desired pattern. A photosetting resin can also be used to form the recess 62. The substrate 60 having the recess 62 can be formed by applying the photosetting resin to the mold, exposing it to light, and then peeling off the mold. In the case of cutting, the recesses 62 can be formed using a drill or the like.

[0065] (Organic material, multi-layer) The substrate may be made of a plurality of organic materials. The substrate may have a plurality of layers, and each of the layers may be made of a different organic material. The organic material may be a polymeric material, and may be a thermoplastic, thermosetting, or photosetting material. The substrate may have two layers made of organic materials, and a recess may be formed in the organic material layer on one side. By forming the layers in layers, it is possible to select materials for different functions, such as selecting a material with appropriate wettability with solder for the material of the recess that comes into contact with the solder. For example, FIG. 8 is a cross-sectional view that shows a schematic example of 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 with excellent heat resistance and dimensional stability is used for the base layer 601, and a material with excellent processability for the recess 62 can be selected for the recess layer 602. For example, a thermoplastic resin such as polyethylene terephthalate or polyimide may be used for the base layer 601, and a thermosetting resin capable of forming the recesses 62 with an imprint mold may be used for the recess layer 602. For example, a thermosetting resin is sandwiched between polyethylene terephthalate and an imprint mold, and heated and pressurized to obtain a base body 600 (including the recesses 62) having excellent flatness. In addition, when the recesses 62 are formed using a photocurable material, a material having high optical transparency may be used for the base layer 601. Examples of the material having high optical transparency include polyethylene terephthalate, transparent (colorless) polyimide, polyamide, and the like. In the case where the recesses 62 are 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 applying pressure with a roller from the polyethylene terephthalate side. Then, after the photocurable material is cured, the imprint mold is peeled off to obtain a base 600 having a layer of polyethylene terephthalate and a layer of photocurable material, with the recesses 62 formed of the photocurable material. The material configuration of the inner wall and the bottom of the recesses 62 can be changed. For example, the inner wall and the bottom of the recesses 62 can be configured of the same resin material.Furthermore, the inner wall and the bottom of the recess 62 may be made of different resin materials (for example, a thermosetting material and a thermoplastic material).

[0066] A photosensitive material may also be used as the organic material. The photosensitive material may be a positive-type photosensitive material or a negative-type photosensitive material. For example, the recesses 62 can be easily formed by forming a photosensitive material with a uniform thickness on the surface of a thermoplastic polyethylene terephthalate film, and then exposing and developing the material. 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. As an exposure method, in addition to exposure using a mask, a direct drawing method such as direct laser exposure can also be used.

[0067] By making the material of the base layer 601 thicker than the material forming the recessed layer 602, the physical properties of the entire substrate 600 can be dominated by the characteristics of the material of the base layer 601. As a result, even if the material forming the recessed layer 602 has a weakness, the material of the base layer 601 can compensate for it. For example, even if the material forming the recessed layer 602 is prone to thermal shrinkage, by selecting a material that is less prone to thermal shrinkage as 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 recessed layer 602, deformation during heating can be suppressed.

[0068] In addition, organic materials can be appropriately selected according to the purpose, such as combining a resin material with excellent heat resistance or dimensional stability with a material that has little component leaching at the melting temperature of the solder microparticles, or combining a resin material with excellent heat resistance or dimensional stability with a material that has suitable wettability with solder.

[0069] As described above, the substrate may be a substrate 600 composed of a base layer 601 and a recessed portion layer 602. For example, by using a photosensitive material for the recessed portion layer 602, the recessed portion 62 can be formed by photolithography. By using a photo- or thermosetting material, a thermoplastic material, or the like for the recessed portion layer 602, the recessed portion 62 can be easily formed by an imprint method. In addition, since it is 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 both desired characteristics can be formed.

[0070] (Inorganic material, single layer (opaque)) The substrate 60 may be made of an inorganic material. From the viewpoint of easy control of low component elution and foreign matter generation, for example, silicon (silicon wafer), stainless steel, aluminum, etc. can be used as the inorganic material. When these materials are used in semiconductor mounting processes, etc., it is easy to take measures against contamination, and they can contribute to high yield and stable production. In addition, for example, when solder particles formed in the recesses 62 are transferred to electrodes on a silicon wafer, if the substrate 60 is made of a silicon wafer, a material with a similar or the same CTE is used. This makes it difficult for misalignment and warping to occur, and transfer to an accurate position is possible. The recesses 62 can be formed by processing using a laser or cutting, dry etching or wet etching, electron beam drawing (for example, FIB processing), etc. 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)) Glass, quartz, sapphire, etc. can be used as the substrate 60. Since these materials are transparent, they can be easily aligned when transferring the solder particles in the recesses 62 to another substrate on which electrodes are formed. Methods for forming the recesses 62 include processing using a laser or cutting, dry or wet etching, electron beam drawing (e.g., FIB processing), etc.

[0072] The advantage of using inorganic materials is that they have superior dimensional stability compared to organic materials. When transferring the solder particles in the recesses 62 onto the electrodes, they can be transferred with high positional accuracy. For example, when transferring solder particles to multiple electrodes with a size and pitch on the order of micrometers, if an inorganic material with superior dimensional stability is used, the solder particles can be transferred to the same position on each electrode.

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

[0074] Another example of the substrate is 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 a stainless steel plate and an imprint mold, applying pressure and heat, and then peeling off the imprint mold. Another example of the substrate is 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 onto a glass plate, exposing the glass plate to light while pressing the imprint mold against the glass plate to cure the photocurable material, and peeling off the imprint mold. When the imprint mold is used to form the recess 62, the material composition of the inner wall and the bottom of the recess 62 can be changed depending on the pressure conditions. For example, when the pressure conditions are relaxed, the inner wall and the bottom of the recess 62 can be made of the same resin material. 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] The base layer 601 may be made of a composite material containing glass fiber, filler, and resin components. An example of the composite material is a copper-clad laminate for wiring boards. A photosensitive material, a thermosetting resin, a photosetting resin, or the like may be applied to the surface of the copper-clad laminate to form the recess 62 as described above. The copper-clad laminate mainly contains a large amount of resin material, but the CTE can be made low by combining it with glass fiber, various fillers, and the like, so that the dimensional stability described above can be ensured. In addition, when an electrode is formed on a copper-clad laminate, the recess 62 is also formed on the same copper-clad laminate, so that the CTE of both is the same or close to that of the recess 62, which is advantageous in that the solder particles in the recess 62 can be easily aligned when transferred and are less likely to be misaligned.

[0076] A package sealant can also be used as the material for the recessed layer 602. The sealant can be in any form, such as a solid, liquid, or film. The recessed portion 62 can be formed by laminating a thin layer of the sealant on glass, a silicon wafer, or the like, and applying pressure and heat with an imprint mold.

[0077] <Method of manufacturing solder bump forming member> The manufacturing method of the solder bump forming member 10 includes a preparation step of preparing a base having a plurality of recesses and solder particles, a storage step of storing at least some of the solder particles in the recesses, a fusion step of fusing the solder particles stored in the recesses to form solder particles in the recesses, and an injection step of placing (injecting) a fluidizing agent (fluid phase) into the recesses in which the solder particles have been formed.

[0078] A method for manufacturing the solder bump forming member 10 according to the first embodiment will be described with reference to FIGS.

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

[0080] There is no particular restriction on the distance L between adjacent recesses, but it can be 0.1 times or more the average particle diameter of the solder particles contained therein, and may be 1 time or more. The distance L can be appropriately adjusted by the arrangement of the electrodes that form the solder bump. The distance between the recesses is not the center-to-center distance between the recesses, but the distance from edge to edge of the recess opening.

[0081] The recess 62 of the base 60 is preferably formed in a tapered shape with an opening area expanding from the bottom 62a of the recess 62 toward the surface 60a of the base 60. That is, as shown in Figures 3(a) and 3(b), the width of the bottom 62a of the recess 62 (width a in Figures 3(a) and 3(b)) is preferably narrower than the width of the opening of the recess 62 on the surface 60a (width b in Figures 3(a) and 3(b)). The size of the recess 62 (width a, width b, volume, taper angle, depth, etc.) may be set according to the size of the desired solder particles.

[0082] The shape of the recess 62 may be a shape other than the shapes shown in Figures 3(a) and 3(b). For example, the shape of the opening in the surface 60a of the recess 62 may be an ellipse, a triangle, a rectangle, a polygon, etc., other than the circle shown in Figure 3(a).

[0083] The shape of the recess 62 in a cross section perpendicular to the surface 60a may be, for example, a shape as shown in FIG. 4. FIGS. 4(a) to 4(h) are cross-sectional views that typically show examples of the cross-sectional shapes of the recesses of the base. In all of the cross-sectional shapes shown in FIGS. 4(a) to 4(h), the width (width b) of the opening in the surface 60a of the recess 62 is the maximum width in the cross-sectional shape. This makes it easier to remove the solder particles formed in the recess 62, improving workability. In addition, since the width (width b) of the opening is the maximum width in the cross-sectional shape, when the solder particles 1 are transferred onto the electrode, the solder particles 1 are easily removed from the recess 62, and an improvement in the transfer rate can be expected. In addition, by appropriately adjusting the width (width b) of the opening, positional deviation is less likely to occur when the solder particles 1 are transferred onto the electrode, making it easier to form the solder bumps at accurate positions.

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

[0085] The particle size distribution of the solder particles can be measured using various methods suited to the size. For example, dynamic light scattering, laser diffraction, centrifugal sedimentation, electrical sensing zone method, resonance mass measurement method, etc. can be used. Furthermore, a method can be used to measure the particle size from images obtained by an optical microscope, an electron microscope, etc. Specific devices include a flow type particle image analyzer, a Microtrac, a Coulter counter, etc.

[0086] Although the CV value of the solder particles prepared in the preparation step is not particularly limited, a high CV value is preferable from the viewpoint of improving the filling property of the combination of large and small particles into the recesses 62. For example, the CV value of the solder particles may exceed 20%, is preferably 25% or more, and is more preferably 30% or more.

[0087] The CV value of the solder fine particles is calculated by dividing the standard deviation of the particle diameter measured by the above-mentioned method by the average particle diameter (D50 particle diameter) and multiplying the result by 100.

[0088] The solder particles may contain tin or a tin alloy. Examples of the tin alloy include an In-Sn alloy, an In-Sn-Ag alloy, an Sn-Au alloy, an Sn-Bi alloy, an Sn-Bi-Ag alloy, an Sn-Ag-Cu alloy, and an Sn-Cu alloy. Specific examples of these tin alloys include the following: In-Sn (In 52% by mass, Bi 48% by mass, melting point 118°C) ·In-Sn-Ag (In20% by mass, Sn77.2% by mass, Ag2.8% by mass, melting point 175℃) Sn-Bi (Sn 43% by mass, Bi 57% by mass, melting point 138°C) Sn-Bi-Ag (Sn 42% by mass, Bi 57% by mass, Ag 1% by mass, melting point 139°C) ·Sn-Ag-Cu (Sn96.5% by mass, Ag3% by mass, Cu0.5% by mass, melting point 217℃) Sn-Cu (Sn 99.3% by mass, Cu 0.7% by mass, melting point 227°C) ·Sn-Au (Sn21.0% by mass, Au79.0% by mass, melting point 278℃)

[0089] The solder particles may contain indium or an indium alloy. Examples of the indium alloy include an In-Bi alloy and an In-Ag alloy. Specific examples of these indium alloys include the following. 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% by mass, Ag 3.0% by mass, melting point 145°C)

[0090] The above tin alloy or indium alloy can be selected depending on the application of the solder particles (temperature during use), etc. For example, when it is desired to obtain solder particles for use in low-temperature fusion, an In-Sn alloy or an Sn-Bi alloy can be used, and in this case, solder particles that can be fused at 150° C. or less can be obtained. When a material with a high melting point, such as an Sn-Ag-Cu alloy or an Sn-Cu alloy, is used, 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 elements selected from Ag, Cu, Ni, Bi, Zn, Pd, Pb, Au, P, and B. Of these elements, Ag or Cu may be contained for the following reasons: When the solder fine particles contain Ag or Cu, the melting point of the resulting solder particles can be lowered to about 220°C, and solder particles having excellent bonding strength with the electrodes can be obtained, thereby achieving better electrical reliability.

[0092] The Cu content of the solder fine particles 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, solder particles that can achieve good solder connection reliability are easily obtained. When the Cu content is 10 mass% or less, solder particles that have a low melting point and excellent wettability are easily obtained, and as a result, the connection reliability of the electrodes with solder bumps is easily improved.

[0093] The Ag content of the solder fine particles is, for example, 0.05 to 10 mass%, and may be 0.1 to 5 mass% or 0.2 to 3 mass%. If the Ag content is 0.05 mass% or more, solder particles that can achieve good solder connection reliability are easily obtained. Also, if the Ag oil content is 10 mass% or less, solder particles that have a low melting point and excellent wettability are easily obtained, and as a result, the connection reliability of the electrodes with solder bumps is easily improved.

[0094] In the accommodation step, the solder particles prepared in the preparation step are accommodated in each of the recesses 62 of the base 60. The accommodation step may be a step in which all of the solder particles prepared in the preparation step are accommodated in the recesses 62, or a step in which only a portion of the solder particles prepared in the preparation step (for example, solder particles smaller than the opening width b of the recesses 62) are accommodated in the recesses 62.

[0095] Fig. 5 is a cross-sectional view that shows a schematic state in which solder particles 111 are accommodated in recesses 62 of base 60. As shown in Fig. 5, a plurality of solder particles 111 are accommodated in each of a plurality of recesses 62.

[0096] The amount of solder particles 111 accommodated in recess 62 is, for example, preferably 20% or more, more preferably 30% or more, even more preferably 50% or more, and most preferably 60% or more, relative to the volume of recess 62. This reduces variation in the amount accommodated, making it easier to obtain solder particles with a smaller particle size distribution.

[0097] The method of storing the solder particles in the recess 62 is not particularly limited. The storing method may be either a dry method or a wet method. For example, the solder particles prepared in the preparation step are placed on the base 60, and the surface 60a of the base 60 is rubbed with a squeegee, so that a sufficient amount of solder particles can be stored in the recess 62 while removing excess solder particles. If the width b of the opening of the recess 62 is greater than the depth of the recess 62, the solder particles may fly out of the opening of the recess 62. If a squeegee is used, the solder particles protruding from the opening of the recess 62 are removed. Methods of removing excess solder particles include blowing compressed air, rubbing the surface 60a of the base 60 with a nonwoven fabric or a bundle of fibers, and the like. These methods are preferable for handling solder particles that are easily deformed because the physical force is weaker than that of a squeegee. In addition, these methods can also leave the solder particles protruding from the opening of the recess 62 in the recess.

[0098] The fusion process is a process in which the solder particles 111 accommodated in the recesses 62 are fused (for example, by heating to 130 to 260° C.) to form solder particles 1 inside the recesses 62. The solder particles 111 accommodated in the recesses 62 are unified by melting, and become spherical due to surface tension. At this time, at the contact portion with the bottom 62a of the recesses 62, the molten solder follows the bottom 62a to form a flat portion 11. As a result, the formed solder particle 1 has a shape having a flat portion 11 on part of its surface. In this manner, the solder bump forming member 10 shown in FIG. 1 is obtained.

[0099] As a method for melting the solder particles 111 accommodated in the recess 62, there is a method of heating the solder particles 111 to a temperature equal to or higher than the melting point of the solder. The solder particles 111 may not melt or spread wet even when heated to a temperature equal to or higher than the melting point due to the influence of an oxide film, and may not be unified. For this reason, the solder particles 111 can be melted, wet, spread, and unified by exposing the solder particles 111 to a reducing atmosphere, removing the surface oxide film of the solder particles 111, and then heating the solder particles 111 to a temperature equal to or higher than the melting point of the solder particles 111. In addition, it is preferable to melt the solder particles 111 in a reducing atmosphere. By heating the solder particles 111 to a temperature equal to or higher than the melting point of the solder particles 111 and creating a reducing atmosphere, the oxide film on the surface of the solder particles 111 is reduced, and the melting, wet, spread, and unification of the solder particles 111 can be efficiently promoted. That is, the method for manufacturing a solder bump member may further include a reduction step of exposing the solder particles accommodated in the recesses to a reducing atmosphere before the fusing step. Also, in the fusing step of the method for manufacturing a solder bump member, the solder particles may be fused under a reducing atmosphere.

[0100] The method for creating a reducing atmosphere is not particularly limited as long as the above-mentioned effects can be obtained, and examples of the method include a method using hydrogen gas, hydrogen radicals, formic acid gas, etc. For example, the solder particles 111 can be melted in a reducing atmosphere by using a hydrogen reduction furnace, a hydrogen radical reduction furnace, a formic acid reduction furnace, or a conveyor furnace or continuous furnace thereof. These devices may be equipped with a heating device, a chamber for filling an inert gas (nitrogen, argon, etc.), a mechanism for evacuating the chamber, etc., in the furnace, which makes it easier to control the reducing gas. In addition, if the chamber can be evacuated, voids can be removed by reducing the pressure after the solder particles 111 are melted and unified, and solder particles 1 with even more excellent connection stability can be obtained.

[0101] The profile of the reduction of the solder particles 111, the melting conditions, the temperature, the adjustment of the atmosphere in the furnace, etc. may be appropriately set in consideration of the melting point, particle size, recess size, and material of the base 60 of the solder particles 111 of the solder particles 111. For example, the base 60 having the recesses filled with the solder particles 111 is inserted into a furnace, and after evacuation, a reducing gas is introduced to fill the furnace with the reducing gas, the surface oxide film of the solder particles 111 is removed, and the reducing gas is removed by evacuation, and then the furnace is heated to a temperature equal to or higher than the melting point of the solder particles 111 to melt and coalesce the solder particles to form solder particles in the recesses 62. After that, nitrogen gas is filled and the temperature in the furnace is returned to room temperature to obtain the solder particles 1. Also, for example, the base 60 with the solder particles 111 filled in the recesses is inserted into a furnace, and after evacuation, reducing gas is introduced to fill the furnace with the reducing gas, the solder particles 111 are heated by an in-furnace heater to remove the surface oxide film of the solder particles 111, and then the reducing gas is removed by evacuation, and then the solder particles 111 are heated to a temperature equal to or higher than the melting point thereof to melt and coalesce the solder particles to form solder particles in the recesses 62, and then nitrogen gas is filled in and the temperature inside the furnace is returned to room temperature to obtain the solder particles 1. Heating the solder particles in a reducing atmosphere has the advantage of increasing the reducing power and making it easier to remove the surface oxide film of the solder particles.

[0102] Furthermore, for example, the base 60 with the solder particles 111 filled in the recesses is inserted into a furnace, and after evacuation, reducing gas is introduced to fill the furnace with the reducing gas, and the furnace is heated to above the melting point of the solder particles 111 by an in-furnace heater, the surface oxide film of the solder particles 111 is removed by reduction while at the same time the solder particles are melted and unified to form solder particles in the recesses 62, the reducing gas is removed by evacuation, and the voids in the solder particles are further reduced, after which nitrogen gas is filled and the temperature inside the furnace is returned to room temperature to obtain the solder particles 1. In this case, the temperature inside the furnace only needs to be adjusted up and down once each, which has the advantage of allowing processing in a short time.

[0103] After forming the solder particles in the recesses 62, a process may be added in which the inside of the furnace is once again made into a reducing atmosphere to remove any remaining surface oxide film. This makes it possible to reduce residues such as solder particles that remain unfused and parts of the oxide film that remain unfused.

[0104] When an atmospheric pressure conveyor furnace is used, the base 60 with the recesses filled with the solder particles 111 can be placed on a conveyor and passed through multiple zones in succession to obtain the solder particles 1. For example, the base 60 with the recesses filled with the solder particles 111 can be placed on a conveyor set to 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 particles 111, then passed through a zone containing a reducing gas such as formic acid gas at a temperature lower than the melting point of the solder particles 111 to remove the surface oxide film of the solder particles 111, then passed through a zone filled with an inert gas such as nitrogen or argon at a temperature higher than the melting point of the solder particles 111 to melt and coalesce the solder 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 base 60 with the solder particles 111 filled in the recesses is placed on a conveyer 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 particles 111, and then passed through a zone in which a reducing gas such as formic acid gas at a temperature equal to or higher than the melting point of the solder particles 111 is present, to remove the surface oxide film of the solder 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 solder particles 1. Since the conveyer furnace can perform processing at atmospheric pressure, it is also possible to continuously process a film-like material by roll-to-roll. For example, a continuous roll product of the base 60 with the solder particles 111 filled in the recesses is produced, and a roll unwinder is installed at the entrance side of the conveyer furnace and a roll winder is installed at the exit side of the conveyer furnace, and the base 60 is transported at a constant speed and passed through each zone in the conveyer furnace, thereby fusing the solder particles 111 filled in the recesses.

[0105] According to the preparation process to the fusion process, solder particles 1 of uniform size can be formed regardless of the material and shape of the solder particles 111. For example, indium-based solder can be deposited by plating, but it is difficult to deposit in a particulate form, and it is soft and difficult to handle. However, in the above method, by using indium-based solder particles as a raw material, indium-based solder particles having a uniform particle size can be easily manufactured. In addition, since the formed solder particles 1 can be handled in a state in which they are accommodated in the recesses 62 of the base 60, they can be transported, stored, etc. without being deformed. Furthermore, since the formed solder particles 1 are accommodated in the recesses 62 of the base 60, they can be contacted with an electrode without being deformed. The average particle size of the obtained solder particles may be 1 to 35 μm, and the CV value may be 20% or less.

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

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

[0108] Next, in the step of disposing the fluidizer, the fluidizer is disposed in the recesses 62 in which the solder particles 1 have been formed. The method of disposing the fluidizer is not particularly limited, but examples thereof include a method of immersing the base 60 in a liquid fluidizer solution and pulling it up, and a method of applying or dropping the liquid fluidizer onto the base 60 (particularly onto the recesses 62). Furthermore, in the case of a solid fluidizer, a method of disposing a fluidizer having a diameter smaller than the diameter of the recesses 62 on the surface of the base 60 and filling the recesses 62 with a squeegee is exemplified. Alternatively, a method of disposing the fluidizer by CVD, vapor deposition, sputtering, etc. is exemplified. Excess fluidizer overflowing from the recesses 62 may be removed. Examples of the removal method include volatilization by reduced pressure, squeegeeing, wiping, scraping, laser etching, blasting, etc.

[0109] For example, an appropriate amount of liquid fluidizing agent can be dropped onto the base 60 (onto the recesses 62), the liquid fluidizing agent can be spread with a squeegee while filling the recesses 62, and then the squeegee can be used again to remove excess liquid fluidizing agent that has not filled the recesses 62. Any fluidizing agent that cannot be removed with the squeegee can be wiped off with, for example, a dust-free clean cloth.

[0110] The method for manufacturing the solder bump forming member 10 may include a pre-step of preparing a base having a plurality of recesses, solder particles, and a fluidizing agent, and a placement step of placing the solder particles and the fluidizing agent in the recesses. In this way, the solder particles 1 are temporarily removed from the base 60, and the solder particles 1 and the fluidizing agent F are again placed in the recesses of the base to prepare the solder bump forming member. With this method, the solder particles 1 can be separated from the solder particles 1, the solder particles 111 that did not become the solder particles 1 in the melting step, the solder particles 111 present outside the recesses 62, and other residues, foreign matter, etc., from the solder particles 1. Specifically, the base 60 having the solder particles 1 in the recesses 62 after the melting step is immersed in a solvent, and the solder particles 1 are taken out of the recesses 62. After the base 60 from which the solder particles 1 have been taken out is pulled out of the solvent, the foreign matter is removed from the solvent by passing the solvent through a filter, mesh, etc. Thereafter, the solder particles 1 are temporarily dispersed in the solvent and left to stand, and then sedimentation and separation are performed. By carrying out the sedimentation separation, the solder particles 1 are separated from the residue (for example, the solder fine particles 111 and foreign matter) to obtain a mixture of the solder particles 1 and the solvent. After carrying out the sedimentation separation multiple times and further removing the residue, the mixture of the solder particles 1 and the solvent is vacuum-dried to obtain the solder particles 1 with high purity. In the arrangement step, the solder particles 1 are again rearranged in the recesses 62 on the surface of the base 60. Thereafter, a fluidizing agent can be arranged in the recesses 62. Alternatively, the fluidizing agent may be arranged in the recesses 62 in advance, and then the solder particles 1 may be arranged in the recesses 62. Alternatively, the fluidizing agent and the solder particles 1 may be mixed in advance, and the mixture may be arranged in the recesses 62. The base on which the solder particles are rearranged may be the base used when the solder particles are produced, or may be a different base.

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

[0112] <Manufacturing method for electrode substrate with solder bumps> A method for manufacturing an electrode substrate with solder bumps includes a preparation step of preparing the above-mentioned solder bump forming member and a substrate having a plurality of electrodes, an arrangement step of bringing the surface of the solder bump forming member having a recess and the surface of the substrate having the electrodes into contact with each other, 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 substrates (circuit components) having multiple electrodes on their surface include chip components such as IC chips (semiconductor chips), resistor chips, capacitor chips, and driver ICs; and rigid package substrates. These circuit components have circuit electrodes, and generally have many circuit electrodes. Other examples of substrates having multiple electrodes on their surface include wiring substrates such as flexible tape substrates having metal wiring, flexible printed wiring boards, and glass substrates on which indium tin oxide (ITO) is vapor-deposited.

[0114] Specific examples of the electrodes include electrodes of 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, etc. The electrodes can be formed by electroless plating, electrolytic plating, sputtering, or etching of a metal foil.

[0115] 6(a) and 6(b) are cross-sectional views showing an example of a manufacturing process of an electrode substrate with solder bumps. The base 60 shown in FIG. 6(a) is in a state in which one solder particle 1 and fluidizer F are accommodated in each recess 62. Meanwhile, the substrate 2 has a plurality of electrodes 3 on its surface. The electrode 3 side surface of the substrate 2 is opposed to and contacted with the opening side surface of the recess 62 of the base 60. There is no particular limit to the number of solder particles 1 contacting each electrode 3, and one particle may be contacted with one electrode, or multiple particles may be contacted with one electrode. Note that the force acting between the solder particles 1 and the recess 62 (for example, an intermolecular force such as van der Waals force) is greater than the gravity acting on the solder particles 1, so that the solder particles 1 do not fall off and remain in the recess 62 even if the main surface of the base 60 is turned down. Furthermore, when at least a portion of the solder particle 1 is in contact with the bottom and / or inner wall of the recess 62 and has a flat portion, the solder particle 1 is in close contact with the recess 62 and is unlikely to fall off.

[0116] With the solder particles and the electrodes in contact with each other, the entire electrode substrate and base 60 are heated at least to a temperature (e.g., 130 to 260°C) higher than the melting point of the solder particles 1, so that 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, forming solder bumps on the electrodes 3. From the viewpoint of more suitably joining the solder particles 1 and the electrodes 3, the solder particles 1 may be heated to a temperature equal to or higher than the melting point of the solder particles while the solder bump forming member 10 and the substrate 2 are in contact with each other under pressure in the heating step. The pressurized state refers to a state in which the solder bump forming member 10 and the substrate 2 are pressed against each other with a force of about 30 to 600 Pa in the directions of the arrows A and B in FIG. 6(a). The solder particles 1 are accommodated in the recesses 62 and pressed against the electrodes. Therefore, even if the solder particles 1 in adjacent recesses 62 flow due to the action of fluidizer F, they are unlikely to mix together, and solder bumps of the same size can be formed only on desired electrodes. In addition, the solder is unlikely to bridge adjacent electrodes, which can suppress short-circuit defects.

[0117] The solder particles 1 are oxidized rapidly by heating in the air, and it is difficult for the solder particles 1 to spread wetly onto the electrodes 3. Therefore, it is preferable that the atmosphere during heating is deoxidized. For example, it may be an inert gas atmosphere such as nitrogen or argon, or a vacuum atmosphere. As the furnace, a reflow furnace (under a nitrogen atmosphere) or a vacuum reflow furnace that is generally used in the solder joining process can be used, and a conveyor-type reflow furnace under a nitrogen atmosphere, a batch-type (chamber-type) reflow furnace, etc. can be used. When using these reflow furnaces, if a process of creating a vacuum after the solder melts is added, air bubbles (voids) in the solder can be removed. Furthermore, a laminator can be used from the viewpoint of improving productivity. If a roller-type laminator is used, pressure and heat can be applied simultaneously. Furthermore, a vacuum-pressure laminator can be used. A vacuum-pressure laminator is preferable because it can create a vacuum in the chamber and can apply pressure and heat simultaneously, making it easy to transfer the solder bumps onto the electrodes 3. In addition, it has the advantage of being able to increase productivity because continuous transportation is possible using a carrier film.

[0118] The solder particles 1 may not melt or wet spread even when heated at a temperature equal to or higher than the melting point due to the influence of the oxide film. For this reason, the solder particles 1 can be melted by exposing the solder particles 1 to a reducing atmosphere, removing the surface oxide film of the solder particles 1, and then heating the solder particles 1 to a temperature equal to or higher than the melting point of the solder particles 1. The solder particles 1 are preferably melted in a reducing atmosphere. By heating the solder particles 1 to a temperature equal to or higher than the melting point of the solder particles 1 and creating a reducing atmosphere, the oxide film on the surface of the solder particles 1 is reduced, and the oxide film on the electrode surface is further reduced, so that the melting and wet spreading of the solder particles 1 can proceed efficiently. That is, the manufacturing method of the 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 arrangement step, or after the arrangement step and before the heating step. In addition, in the heating step of the manufacturing method of the 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. In the heating process for forming solder bumps on the electrodes, the electrodes and the opening surfaces of the solder bump forming member are brought into close contact (under pressure if necessary), so that the solder bumps are formed only on the electrodes, which makes it easier to suppress solder bridging between adjacent electrodes.

[0119] For details about the reducing atmosphere, the description of the method for producing a solder bump member can be referred to as appropriate.

[0120] After the heating step, the whole is cooled, whereby the electrodes 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 manufacturing method for 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. After the solder bumps 1A are formed on the electrodes 3, the solder bump forming member 10 is removed from the substrate 2 (removal step) to obtain an electrode substrate with solder bumps 20. FIG. 6(b) is a schematic diagram of the electrode substrate with solder bumps 20 obtained in this manner.

[0121] On the obtained electrode substrate 20 with solder bumps, there may be solder particles 1 that have detached from the recesses 62 but are not used for bonding to the electrodes 3. Therefore, the manufacturing method of the electrode substrate with solder bumps may further include a cleaning step for removing the solder particles 1 that are not bonded to the electrodes after the removing step. Examples of the cleaning method include blowing compressed air and rubbing the substrate surface with a nonwoven fabric or a bundle of fibers. Note that, if fluidizer F is present as a residue on the electrode substrate 20 with solder bumps, the fluidizer can also be removed by the cleaning step. In the cleaning step, a solution in which the fluidizer F is easily dissolved can be used.

[0122] According to the manufacturing method of the electrode substrate with solder bumps, it is possible to obtain the electrode substrate with solder bumps 20 comprising the substrate 2, the electrodes 3 and the solder bumps 1A in this order.

[0123] <Method of Manufacturing Connection Structure> 7(a) and 7(b) are cross-sectional views showing an example of a manufacturing process of a connection structure. A manufacturing method of a connection structure will be described with reference to FIG. 7(a) and FIG. 7(b). First, an 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 bumps 1A and the other electrodes 5 face each other. Then, pressure is applied in the thickness direction of the laminate of these members (the direction of arrows A and B shown in FIG. 7(a)). When applying pressure, the entire structure is heated at least to a temperature (for example, 130 to 260° C.) higher than the melting point of the solder bumps 1A, so that the solder bumps 1A melt between the electrodes 3 and the other electrodes 5. Then, the entire structure is cooled to form a solder layer 1B between the electrodes 3 and the other electrodes 5, and the electrodes are electrically connected. In order to suppress oxidation of the solder bumps 1A and the electrodes 5, it is preferable to heat the electrodes in an atmosphere that blocks oxygen. For example, it is preferable to heat the electrodes in an inert gas atmosphere such as nitrogen. Specifically, a vacuum reflow oven, a nitrogen reflow oven, or the like can be used.

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

[0125] Furthermore, pressure may be applied to achieve stable connection. An electrode substrate 20 with solder bumps as shown in FIG. 6(b) is prepared in advance. Another substrate 4 having a plurality of other electrodes 5 on its surface is also prepared. Then, both are arranged so that the solder bumps 1A and the other electrodes 5 face each other. Then, pressure is applied in the thickness direction of the laminate of these members (the direction of arrows A and B shown in FIG. 7(a)). When applying pressure, the entire structure is heated at least to a temperature (for example, 130 to 260° C.) higher than the melting point of the solder bumps 1A, so that the solder bumps 1A melt between the electrodes 3 and the other electrodes 5. Then, the entire structure is cooled to form a solder layer 1B between the electrodes 3 and the other electrodes 5, and the electrodes are electrically connected. In this case, too, in order to suppress oxidation of the surfaces of the solder bumps 1A, the electrodes 5, and the electrodes 3, it is preferable to carry out the above steps under vacuum, in an inert gas atmosphere such as nitrogen, or in a reducing atmosphere. Examples of a method for creating a reducing atmosphere include the above-mentioned hydrogen gas, hydrogen radicals, and formic acid. Specifically, a hydrogen reduction furnace, a hydrogen reflow furnace, a hydrogen radical furnace, a formic acid furnace, a vacuum furnace, a continuous furnace, a conveyor furnace, or the like can be used.

[0126] A material having a reducing effect can be used as a method for creating a reducing atmosphere. For example, a flux material or a material containing a flux component can be placed near the solder bump 1A, the electrode 5, and the electrode 3. A paste, film, or the like containing a flux material or a material containing a flux component can be used. First, an electrode substrate 20 with solder bumps as shown in FIG. 6(b) is prepared in advance. A paste containing a flux material or a flux component is placed on the entire surface of the electrode substrate 20 on which the solder bump 1A is formed, or on the solder bump 1A and the electrode 3 including the solder bump 1A. In addition, another substrate 4 having a plurality of other electrodes 5 on its surface is prepared. Then, both are placed so that the solder bump 1A and the other electrode 5 face each other. Thereafter, the solder bump 1A and the other electrode 5 are kept in contact with each other through, for example, a paste containing a flux material or a flux component, and heated at least to a temperature higher than the melting point of the solder bump 1A (for example, 130°C to 260°C), whereby 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. Thereafter, by washing and removing the flux components, corrosion of the solder layer 1B, the electrode 3, and the electrode 5 due to flux residue can be suppressed.

[0127] As another method, an electrode substrate 20 with solder bumps as 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, and a paste containing a flux material or a flux component is placed on the entire surface of the substrate 4 having the electrodes 5 or in the vicinity of the surface of the electrodes 5. Then, both are placed so that the solder bumps 1A and the other electrodes 5 face each other. Thereafter, the solder bumps 1A and the other electrodes 5 are heated at least to a temperature higher than the melting point of the solder bumps 1A (for example, 130°C to 260°C) while being in contact with each other through, for example, a paste containing a flux material and a flux component, so that the solder bumps 1A melt between the electrodes 3 and the other electrodes 5. Thereafter, the entire structure is cooled to form a solder layer 1B between the electrodes 3 and the other electrodes 5, and the electrodes are electrically connected to each other.

[0128] Also, a film containing a flux component can be used. An electrode substrate 20 with solder bumps as shown in FIG. 6(b) is prepared in advance. A film containing a flux component is arranged on the surface of the electrode substrate 20 on which the solder bumps 1A are formed. 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 bumps 1A and the other electrodes 5 face each other. Thereafter, the solder bumps 1A and the other electrodes 5 are kept in contact with each other through the film containing the flux component, or pressure is applied between the opposing electrodes 3 and 5 to push the film containing the flux component out of the gap between the electrodes 3 and 5, and the solder bumps 1A and the other electrodes 5 are kept in contact with each other by heating at least to a temperature (for example, 130°C to 260°C) higher than the melting point of the solder bumps 1A, so that the solder bumps 1A melt between the electrodes 3 and 5. Thereafter, the entire structure is cooled to form a solder layer 1B between the electrodes 3 and 5, and the electrodes are electrically connected to each other.

[0129] The paste and film containing the flux component may contain a thermosetting material. This allows the thermosetting component to harden at the same time as the solder bumps 1A melt, thereby fixing the electrode substrate 20 and the substrate 4. The thermosetting material may be hardened by heating again in a later process, separate from the melting and heating of the solder bumps 1A. The film containing the flux component may be placed in advance on the surface of the substrate 4 on which the electrodes 5 are formed. The position of the film containing the flux component, whether it is placed 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 of the joining process, and the like.

[0130] Heating methods for melting the solder bumps 1A include, in a vacuum, a method of heating a heating plate in a reflow furnace and transmitting the heat to the solder bumps 1A through the substrates 2 and 4 in contact with the heating plate, and a method of using radiation such as infrared rays. In addition to or in combination with the above-mentioned heating method using a heating plate and infrared rays, a method of heating the solder bumps 1A through a heated gas can be used. Specifically, the solder bumps 1A can be heated by heating an inert gas, nitrogen, hydrogen, hydrogen radicals, or formic acid. The flux material and flux components 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] Other methods include a method using electromagnetic waves such as microwaves. For example, a specific electromagnetic wave that heats the components of the electrodes 3, 5, and solder bumps 1A can be applied from the outside. For example, when the substrate 4 and substrate 2 are resin substrates, when a specific electromagnetic wave is irradiated from the outside of the substrate 4 and substrate 2, the electromagnetic wave penetrates the substrate 4 and substrate 2, and the electrodes 3 and solder bumps 1A or electrodes 5 are heated by the electromagnetic wave. In this method, the part to be joined can be selectively heated, so there is an advantage that no extra thermal history remains. For example, even if the substrate 2 and substrate 4 are made of a material with low heat resistance, the solder bump 1A can be melted to reliably join the electrodes 3 and 5. In addition, there is an advantage that the thermal history is unlikely to remain in the entire system to be joined, so warping and decomposition after joining can be easily suppressed. In addition, when microwaves are used, the solder bumps 1A can be melted in a short time compared to using a heating plate, infrared rays, heated gas, etc. as described above, so there is an advantage that the thermal history of the entire system to be joined can be reduced, and the above-mentioned effect can be easily obtained. Furthermore, by using microwaves, it is possible to locally heat only the portions of the electrodes 3, solder bumps 1A, and electrodes 5 that are to be joined or melted. Therefore, it is not necessary to heat the entire system, and even if there are low heat-resistant materials or other electronic components near the electrodes 3 and 5 that should not be heated, the solder bumps 1A can be melted and joined.

[0132] Another method is to use ultrasonic waves. For example, when an ultrasonic vibrator is placed on the opposite side of the substrate 2 to the electrode 3 and ultrasonic waves are applied, the ultrasonic vibration energy melts the solder bump 1A. This bonds the electrode 3 and the electrode 5, which has been placed in front of the electrode 3, via the solder layer 1B. Since ultrasonic bonding can melt the solder bump 1A in a short time, it is not necessary to apply heat to the entire substrates 2 and 4, and the electrodes 3 and 5 can be reliably bonded even if the substrates 2 and 4 are made of materials with low heat resistance.

[0133] FIG. 7(b) is a schematic diagram of the connection structure 30 thus obtained. That is, FIG. 7(b) is a schematic diagram showing a state in which an electrode 3 of a substrate 2 and another electrode 5 of another substrate 4 are connected via a solder layer 1B formed by fusion. In this specification, "fusion" means a state in which at least a part of an electrode is joined by a solder (solder bump 1A) melted by heat, and then the solder is joined to the surface of the electrode through a process of solidifying the solder. It can be said that the connection structure 30 comprises a first circuit member having a substrate and a plurality of electrodes on its surface, a second circuit member having 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. 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] Applications of the connection structures include connections of semiconductor memories, semiconductor logic chips, etc., connections of primary and secondary mounting of semiconductor packages, junctions of CMOS image elements, laser elements, LED light-emitting elements, etc., and devices using them such as cameras, sensors, liquid crystal displays, personal computers, mobile phones, smartphones, tablets, etc.

[0135] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. EXAMPLES

[0136] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0137] <Preparation of film for solder bump formation> (Example 1) Step a1: Classification of solder particles 100g of Sn-Bi solder particles (5N Plus, melting point 139℃, Type 8) were immersed in distilled water, ultrasonically dispersed, and then left to stand, and the solder particles floating in the supernatant were collected. This process was repeated to collect 10g of solder particles. The average particle size of the obtained solder particles was 1.0μm, and the CV value was 42%. Step b1: Arrangement on a substrate A substrate (polyimide film, thickness 100 μm) was prepared having multiple recesses 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 in the center of the opening diameter of 2.3 μmφ when the opening is viewed from above), as shown in Table 1. The multiple recesses were regularly arranged at intervals of 1.0 μm. The solder particles (average particle diameter 1.0 μm, CV value 42%) obtained in step a were placed in the recesses of the substrate. The surface of the substrate on which the recesses were formed was rubbed with a slightly adhesive roller to remove excess solder particles, and a substrate was obtained in which the solder particles were placed only in the recesses. Step c1: Formation of solder particles The substrate with the solder particles placed in the recesses in step b1 was placed in a hydrogen reduction furnace (vacuum soldering device manufactured by Shinko Seiki Co., Ltd.), and after evacuation, hydrogen gas was introduced into the furnace to fill it with hydrogen. The furnace was then kept at 280°C for 20 minutes, after which it was evacuated again, nitrogen was introduced to return the pressure to atmospheric pressure, and the temperature inside the furnace was then lowered to room temperature, forming solder particles inside the recesses.

[0138] <Evaluation of solder particles> A portion of the substrate obtained through step c1 was fixed to the surface of a SEM observation stand, and platinum was sputtered onto the surface. The diameters of 300 solder particles were measured using the SEM, and the average particle size and CV value were calculated. The results are shown in Table 2. In addition, the surface shape of a portion of the substrate obtained through step c1 was measured using a laser microscope (Olympus Corporation, LEXT OLS5000-SAF), the height of the solder particles from the substrate surface was measured, and the average value for 300 particles was calculated. The results are shown in Table 2.

[0139] Step d1: Placing flux 90 parts by mass of dihydroterpineol was mixed with 20 parts by mass of adipic acid as a flux component to form a fluid phase. This fluid phase was placed in the recesses in which the solder particles obtained in step c1 were placed. The surface of the substrate on which the recesses were formed was then rubbed with a rubber squeegee to remove excess fluid phase (flux component) that was not filled in the recesses. The substrate surface was then wiped with a dust-free clean cloth to produce a film for forming solder bumps.

[0140] (Examples 2 to 6) Films for forming solder bumps were produced and evaluated in the same manner as in Production Example 1, except that the recess size, etc. were changed as shown in Table 1. The results are shown in Table 2.

[0141] (Preparation Example 7) A film for forming solder bumps was produced and evaluated in the same manner as in Preparation Example 1, except that the following step c2 was carried out instead of step c1. The results are shown in Table 2. Step c2: Formation of solder particles The substrate with the solder particles placed in the recesses in step b1 was placed in a hydrogen radical reduction furnace (plasma reflow device manufactured by Shinko Seiki Co., Ltd.), and after evacuation, hydrogen gas was introduced into the furnace to fill it with hydrogen gas. The temperature inside the furnace was then adjusted to 120°C, and hydrogen radicals were irradiated for 5 minutes. The hydrogen gas in the furnace was then removed by evacuation, and the furnace was heated to 170°C. After that, nitrogen was introduced into the furnace to return it to atmospheric pressure, and the temperature inside the furnace was then lowered to room temperature to form solder particles.

[0142] (Examples 8 to 12) A film for forming solder bumps was produced and evaluated in the same manner as in Production Example 7, except that the recess size, etc. were changed as shown in Table 1. The results are shown in Table 2.

[0143] (Example 13) A film for forming solder bumps was produced and evaluated in the same manner as in Preparation Example 1, except that the following step c3 was carried out instead of step c1. The results are shown in Table 2. Step c3: Formation of solder particles The substrate with the solder particles placed in the recesses in step b1 was placed in a formic acid reduction furnace, and after evacuation, formic acid gas was introduced into the furnace to fill the furnace with formic acid gas. The temperature inside the furnace was then adjusted to 130°C and the temperature was maintained for 5 minutes. After that, the formic acid gas in the furnace was removed by evacuation, and the furnace was heated to 180°C, after which nitrogen was introduced into the furnace to return it to atmospheric pressure, and the temperature inside the furnace was then lowered to room temperature to form the solder particles.

[0144] (Examples 14-18) A film for forming solder bumps was produced and evaluated in the same manner as in Production Example 13, except that the recess size, etc. were changed as shown in Table 1. The results are shown in Table 2.

[0145] (Example 19) A film for forming solder bumps was produced and evaluated in the same manner as in Preparation Example 1, except that the following step c4 was carried out instead of step c1. The results are shown in Table 2. Step c4: Formation of solder particles The substrate with the solder particles placed in the recesses in step b1 was placed in a formic acid conveyor reflow furnace (1913MK, manufactured by Heller Industries, Inc.) and, while being transported on a conveyor, was passed successively through a nitrogen zone, a nitrogen and formic acid gas mixed zone, and a nitrogen zone, all adjusted to 190° C. The substrate was passed through the nitrogen and formic acid gas mixed zone for 20 minutes, forming solder particles in the recesses.

[0146] (Examples 20-24) A film for forming solder bumps was produced and evaluated in the same manner as in Preparation Example 19, except that the recess size, etc. were changed as shown in Table 1. The results are shown in Table 2.

[0147] [Table 1]

[0148] [Table 2]

[0149] <Preparation of evaluation chip with solder bumps> Step e1: Preparation of evaluation chip Seven types of chips with gold bumps (3.0 x 3.0 mm, thickness: 0.5 mm) were prepared as shown below. Chip C1: Area 100 μm x 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 40μm×40μm, space 16μm, height: 7μm, number of bumps 362 Chip C4: Area 20μm×20μm, space 7μm, height: 5μm, number of bumps 362 Chip C5: Area 10μm×10μm, space 6μm, height: 3μm, number of bumps 362 Chip C6: Area 10 μm x 10 μm, space 4 μm, height: 3 μm, number of bumps 362 Chip C7: Area 5 μm x 10 μm, space 3 μm, height: 2 μm, number of bumps 362

[0150] Process f1: Solder bump formation (without using formic acid gas) According to the following steps i) to iii), solder bumps were formed on a chip with gold bumps (3.0×3.0 mm, thickness: 0.5 mm) using the film for solder bump formation produced in step c2 (Production Example 7). i) A glass plate with a thickness of 0.3 mm was placed on a hot plate, and the evaluation chip was placed on the glass plate with the gold bumps facing up. ii) The opening side of the concave portion of the film for solder bump formation was faced downwards, and the film for solder bump formation was placed so that the gold bump surface of the evaluation chip and the film for solder bump formation were in contact. Furthermore, a 0.3 mm thick glass plate was placed on the film for solder bump formation, and a stainless steel weight was placed on the glass plate to adhere the film for solder bump formation to the gold bumps. iii) A bell-shaped glass cover into which nitrogen gas can be blown was prepared. The sample prepared in ii) with the film for forming solder bumps laminated on the evaluation chip was covered with this glass cover. Nitrogen gas was then introduced into the glass cover, and the entire sample was placed under a nitrogen atmosphere. The hot plate was heated to 160°C and heated for 5 minutes. After that, the hot plate was returned to room temperature, the nitrogen gas was stopped, and the sample was opened to the atmosphere. The weight at the top, the glass plate, and the film for forming solder bumps were removed in that order. Next, the evaluation chip was immersed in a methanol solution, the fluid phase was washed away, and the evaluation chip with solder bumps was obtained by vacuum drying (40°C for 60 minutes).

[0151] <Solder bump evaluation: No formic acid gas used> The evaluation chip obtained through step f1 was fixed to the surface of a pedestal for SEM observation, and platinum was sputtered on the surface. Using the SEM, the number of solder bumps on 30 gold bumps was counted, and the average number of solder bumps on one gold bump was calculated. The results are shown in Table 3. In addition, the height of the solder bumps from the gold bump was measured using a laser microscope (Olympus Corporation, LEXT OLS5000-SAF), and the average value for 100 bumps was calculated. The results are shown in Table 3.

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

[0153] (Comparative Preparation Example 1) A comparative film for forming solder bumps having solder particles in the recesses was produced in the same manner as in Production Example 8, except that step d1 (arrangement of flux) was not performed. Solder bumps were formed and evaluated in the same manner as in step f1, except that this comparative film for forming solder bumps 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] Since there was no flux-containing fluid phase in the recesses of Comparative Example 1, the surface oxide film of the solder particles was not reduced, and the solder particles did not wet and spread onto the gold bumps.

[0157] Since the fluid phase containing the flux component is accommodated in the recess together with the solder particles, the flux component removes the oxide film on the solder particle surface by heating and also cleans the gold bump (electrode) surface. Then, the solder particles are melted and carried to the gold bump surface by the fluid phase, and a solder bump can be formed on the gold bump. As shown in FIG. 1, since the fluid phase is present in the recess, the fluid phase removes the oxide film near the solder particle surface facing the gold bump (electrode), and the contact between the solder particles and the gold bump is activated. Since the heating is performed with the opening surface of the recess in contact with the gold bump surface, the solder particles can contact the gold bump surface. At this time, the wall surface of the recess suppresses the flow of the solder particles and flux in the direction of the surface of the solder bump forming member, and the solder bump can be formed on the gold bump. Also, for the same reason, the solder particles in adjacent recesses are less likely to bond to each other, and good solder bumps can be formed. The amount of wetting and spreading with the gold bump surface needs to be controlled by the heating temperature and time during bump formation. However, since the solder particles and flux are stored in the recesses and pressed against the gold bump surface, it is difficult for adjacent solder particles to bond with each other for the above reasons, and the likelihood of heating temperature and time is large. Therefore, a solder bump formation that is stable for industrial use is achieved. A small amount of flux components and solder particles were found in the parts without gold bumps, but they could be removed by washing the evaluation chip in methanol. The recess opening faces the evaluation chip surface other than the gold bumps, but since the gold bumps are higher than the other surfaces, the recess opening faces are difficult to touch, and the solder particles are difficult to move to the evaluation chip side. Even if the recess opening faces are partially in contact with the evaluation chip side, there is no metal (electrode) for the solder to spread, so it can be easily removed by subsequent washing. Also, as described above, since there are solder particles and flux in the recesses, the flow of solder particles in the surface direction of the solder bump forming member is suppressed, making it difficult for short-circuit defects of the gold bumps to occur.

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

[0159] Process f2: Solder bump formation (using formic acid gas) According to the following steps i) to iii), solder bumps were formed on a chip with gold bumps (3.0×3.0 mm, thickness: 0.5 mm) using the film for solder bump formation produced in step c2 (Production Example 7). 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 side of the concave portion of the film for solder bump formation was faced downwards, and the film for solder bump formation was placed so that the gold bump surface of the evaluation chip and the film for solder bump formation were in contact. Furthermore, a 0.3 mm thick glass plate was placed on the film for solder bump formation, and a stainless steel weight was placed on the glass plate to adhere the film for solder bump formation 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. In the conveyor furnace, the sample first passed through a nitrogen gas zone. At this time, oxygen around the sample was removed. It then passed through a nitrogen gas zone heated to 150°C, then through a formic acid gas (4%) zone at 180°C, and then was introduced into a vacuum chamber set at 160°C. After the vacuum chamber was closed, the chamber was kept at a vacuum for 1 minute, and nitrogen gas was introduced to return it to atmospheric pressure. The sample then left the vacuum chamber and passed through a cooling zone in a nitrogen gas atmosphere to return it to room temperature. The top weight, glass plate, and film for forming solder bumps were removed in that order. Next, the evaluation chip was immersed in a methanol solution, the flow phase was washed off, and it was vacuum dried (40°C for 60 minutes) to obtain an evaluation chip with solder bumps.

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

[0161] Solder bumps were formed and evaluated in the same manner as in step f2, except that the films for forming solder bumps of Preparation Examples 8 to 12 were used instead of the film for forming solder bumps of Preparation Example 7. The evaluation results are shown in Table 4.

[0162] Solder bumps were formed and evaluated in the same manner as in step f2, except for using the comparative film for solder bump formation obtained in Comparative Preparation Example 1. The results are shown in Table 4.

[0163] [Table 4]

[0164] In the preparation examples 7 to 12, solder bumps could be formed on the gold bumps. In particular, the number of solder bumps tends to increase compared to the case where the formic acid gas atmosphere was not used (Table 3). This is considered to be because the surface oxide film of the solder particles in the recesses was sufficiently reduced by the flux components contained in the fluid phase and the formic acid gas, and the organic matter on the gold pad surface was also removed by the formic acid gas, so that the solder bumps were easily formed on the gold bumps. When the solder bumps obtained using the formic acid gas atmosphere were observed with a microscope and an electron microscope, they were less distorted in spherical shape than the solder bumps obtained without using the formic acid gas atmosphere. This is considered to be because the air bubbles in the solder bumps were removed by creating a vacuum in the vacuum chamber after heating, and the low molecular components in the fluid phase were also sufficiently evaporated, so that the solder bumps became spherical with less distortion.

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

[0166] <Preparation of connection structure> Step g1: Preparation of evaluation board We prepared seven types of gold bumped substrates (70 x 25 mm, thickness: 0.5 mm) as shown below. These gold bumps also had lead wires formed on them for resistance measurement. 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 x 40 μm, space 16 μm, height: 4 μm, number of bumps 362 Substrate D4: Area 20 μm x 20 μm, space 7 μm, height: 4 μm, number of bumps 362 Board D5: Area 10μm×10μm, space 6μm, height: 3μm, number of bumps 362 Board D6: Area 10μm×10μm, space 4μm, height: 3μm, number of bumps 362 Board D7: Area 5μm×10μm, space 3μm, height: 3μm, number of bumps 362

[0167] Step h1: Bonding of electrodes According to the following steps i) to iii), the evaluation chip with solder bumps produced in step f1 was connected to an evaluation board with gold bumps via the solder bumps. i) The evaluation board was placed on the lower heating plate of a formic acid reflow furnace (batch-type vacuum soldering device manufactured by Shinko Seiki Co., Ltd.) with the gold bumps facing up. ii) The evaluation chip on which the solder bumps were formed was placed with the solder bump surface facing downwards so that the gold bump surface of the evaluation substrate and the solder bumps were in contact with each other, and the evaluation chip was fixed so as not to move. iii) The formic acid vacuum reflow furnace was operated, and after evacuation, formic acid gas was filled, and the lower hot plate was heated to 180°C and heated for 5 minutes. After that, the formic acid gas was discharged by evacuation, and nitrogen replacement 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 viscosity-adjusted underfill material (Hitachi Chemical Co., Ltd., CEL series) was placed between the evaluation chip and evaluation board, and after filling by evacuation, it was cured at 165°C for 2 hours to produce a connection structure of the evaluation chip and evaluation board. The combination of each material in the connection structure is as follows. (1) Chip C1 / film for forming solder bumps / substrate D1 (2) Chip C2 / Solder bump forming film / Substrate D2 (3) Chip C3 / Solder bump forming film / Substrate D3 (4) Chip C4 / Solder bump forming film / Substrate D4 (5) Chip C5 / Solder bump forming film / Substrate D5 (6) Chip C6 / Solder bump forming film / Substrate D6 (7) Chip C7 / Solder bump forming film / Substrate D7

[0168] <Evaluation of connection structures> A conductive resistance test and an insulation resistance test were performed on some of the obtained connection structures as follows.

[0169] (Conductivity resistance test - Moisture absorption and heat resistance test) Regarding the conduction resistance between a chip (bump) with gold bumps and a substrate (bump) with gold bumps, the initial conduction resistance value and the value after a moisture absorption and heat resistance test (left for 100, 500, and 1000 hours under conditions of a temperature of 85°C and a humidity of 85%) were measured for 20 samples, and the average value was calculated. The conduction resistance was evaluated from the obtained average value according to the following criteria. The results are shown in Table 5. If the following criteria A or B were satisfied after 1000 hours of moisture absorption and heat resistance testing, the conduction resistance was deemed good. A: The average resistance is less than 2Ω B: The average resistance is between 2Ω and 5Ω C: The average resistance is between 5 Ω and 10 Ω D: The average resistance is 10 Ω or more and less than 20 Ω E: The average resistance is 20Ω or more

[0170] (Conductivity resistance test - high temperature storage test) Regarding the conduction resistance between the gold bumped chip (bump) and the gold bumped substrate (bump), the initial value of the conduction resistance and the value after the high temperature storage test (100, 500, 1000 hours at 100°C) were measured for 20 samples. After high temperature storage, a drop impact was applied, and the conduction resistance of the sample after the drop impact was measured. The drop impact was caused by fixing the connection structure to a metal plate with screws and dropping it from a height of 50 cm. After the drop, the DC resistance was measured at the solder joints (4 places) at the chip corners where the impact was the greatest, and when the measured value increased by 5 times or more from the initial resistance, it was considered that a break had occurred, and evaluation was performed. Measurements were performed at 4 places for each sample, for a total of 80 places. The results are shown in Table 6. The solder connection reliability was evaluated as good when the following criteria A or B were met after 20 drops. A: There were zero solder joints where the resistance increased five times or more from the initial resistance. B: There were 1 to 5 solder joints whose resistance increased 5 times or more from the initial resistance. C: There were 6 to 20 solder joints whose resistance increased 5 times or more from the initial resistance. D: There were 21 or more solder joints where the resistance increased by 5 times or more from the initial resistance.

[0171] (Insulation resistance test) Regarding the insulation resistance between the chip electrodes, the initial insulation resistance value and the value after migration testing (exposed for 100, 500, and 1000 hours under conditions of temperature 60°C, humidity 90%, and 20V application) were measured for 20 samples. 9The percentage of samples with a resistance of 0.1Ω or more was calculated. The insulation resistance was evaluated based on the obtained percentage according to the following criteria. The results are shown in Table 7. If the following criteria A or B were met after 1000 hours of migration testing, the insulation resistance was deemed good. A: Insulation resistance value 10 9 The percentage of Ω or higher is 100%. B: Insulation resistance value 10 9 The percentage of Ω or higher is between 90% and 100% C: Insulation resistance value 10 9 The percentage of Ω or higher is between 80% and 90% D: Insulation resistance value 10 9 The ratio of Ω or more is between 50% and 80% E: Insulation resistance value 10 9 The ratio of Ω or more is less than 50%

[0172] [Table 5]

[0173] [Table 6]

[0174] [Table 7]

[0175] <Preparation of film for solder bump formation> Step i1: Preparation of evaluation substrate A liquid photosensitive resist (Hitachi Chemical Co., Ltd., AH series) was applied to a thickness of 2.3 μm on a 6-inch silicon wafer by spin coating. The photosensitive resist on this silicon wafer was exposed and developed to form an evaluation pattern having a recess 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 above). Each evaluation pattern was 20 mm x 20 mm in size, and the aforementioned recess was arranged in an area of ​​10 mm x 10 mm at the center. The position of the recess was arranged at a position (X-direction pitch, Y-direction pitch) relative to the electrode arrangement pattern of the evaluation chip C8 described later, and three alignment marks were also arranged. This was cut into a size of 20 mm x 20 mm by a dicer to obtain an evaluation substrate 1. The evaluation substrate is outlined in Table 8.

[0176] [Table 8]

[0177] The thickness, opening diameter and pitch of the photosensitive resist were set to the values ​​shown in Table 8, and evaluation substrates 2 to 6 were produced.

[0178] <Preparation of solder particles> Step j1: Preparation of solder particles Through steps a1, b1, and c1, a film for forming a solder bump having solder particles in the recesses was obtained, as shown in Preparation Example 7 to Preparation Example 12 in Table 2. A stainless steel tray was filled with isopropyl alcohol, the obtained film for forming a solder bump was immersed, and ultrasonic waves of 28 kHz and 600 W were applied for 5 minutes. The solder particles were detached from the recesses and dispersed in the isopropyl alcohol solvent. The solvent in which the solder particles were dispersed was left to stand, and the supernatant was discarded. Thereafter, the tray was filled again with isopropyl alcohol, and the solder particles were well dispersed and then left to stand. This sedimentation and separation operation was performed three times, and solder particles 1 to 6 with uniform particle diameters were obtained. An overview of solder particles 1 to 6 is shown in Table 9.

[0179] [Table 9]

[0180] (Example 25) Step k1: Arrangement of flow 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 dropped onto the surface of evaluation substrate 1, measuring 20 mm x 20 mm, fixed on a glass plate, and the surface of evaluation substrate 1 was rubbed with a urethane squeegee to fill the recesses with solder particles 1 and dodecane. Excess solder particles 1 and dodecane on the surface of evaluation substrate 1 were wiped off with a clean cloth, and a film for forming solder bumps in which solder particles 1 and dodecane were placed in the recesses of evaluation substrate 1 was obtained.

[0181] [Table 10]

[0182] (Examples 26-42) Evaluation films for forming solder bumps 26 to 42, in which solder particles and a fluidizer were placed in the recesses, were obtained in the same manner as in step k1, except that the type of fluidizer, solder particles, and evaluation substrate were combined as shown in Table 10. Note that adipic acid was prepared by adding 20 parts by mass of adipic acid to 90 parts by mass of dihydroterpineol and mixing well to obtain a fluid phase.

[0183] <Preparation of evaluation chip with solder bumps> Step e2: Preparation of evaluation chip Six types of chips with gold bumps (10 mm x 10 mm, thickness: 0.5 mm) were prepared as shown below. Chip C8: Size 8 x 4 μm, X-direction pitch 16 μm, Y-direction pitch 8 μm, height: 3 μm, number of bumps 382,000 Chip C9: Size 16μm x 8μm, X-direction pitch 32μm, Y-direction pitch 16μm, height: 5μm, number of bumps 95700 Chip C10: Size 24μm×12μm, X-direction pitch 48μm, Y-direction pitch 24μm, height: 8μm, number of bumps 42500 Chip C11: Size 72μm x 36μm, X-direction pitch 144μm, Y-direction pitch 72μm, height: 10μm, number of bumps 4700 Chip C12: Size 96μm x 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 In addition, three alignment marks are arranged on each.

[0184] <Solder bump formation> Step f3: Solder bump formation: Nitrogen atmosphere According to the following steps i) to iii), solder bumps were formed on a chip with gold bumps (10 mm×10 mm, thickness: 0.5 mm) using the film for solder bump formation for evaluation 25 produced in step k1. i) Chip C8 was fixed on a 30 mm × 30 mm (0.5 mm thick) glass plate with the gold bumps facing up, and then fixed by suction to the stage of a flip chip bonder (FC3000: manufactured by Toray). ii) A 20 mm×20 mm evaluation substrate 1 was picked up by a heating and pressing head, the alignment marks were read by a camera, and the electrode positions of chip C8 were aligned with the recesses of evaluation substrate 1 and 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 of 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 top evaluation substrate 1, and heated for 3 minutes under a nitrogen atmosphere. Then, the top weight and evaluation substrate 1 were removed in that order. Next, the chip C8 was immersed in a methanol solution, the fluid phase was washed off, and the chip was vacuum dried (40°C for 60 minutes) to obtain an evaluation chip 25 with solder bumps.

[0185] <Solder bump evaluation: No formic acid gas used> The evaluation chip 25 obtained through step f1 was fixed to the surface of a SEM observation stand, and platinum was sputtered on the surface. Using the SEM, the number of solder bumps formed on 300 gold bumps was counted, the solder bump formation rate was calculated, and evaluated according to the following evaluation criteria. The results are shown in Table 11. The solder bump formation rate was considered to be good when it satisfied the evaluation criteria of A or B. A: Solder bump formation rate is 90% or more B: Solder bump formation rate is 80% or more but less than 90% C: Solder bump formation rate is between 70% and 80% D: Solder bump formation rate is between 60% and 70% E: Solder bump formation rate is less than 60%

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

[0187] Next, solder bumps were formed and evaluated in the same manner as above, except that evaluation films 26 to 42 for forming solder bumps for preparation examples 26 to 42 were used instead of evaluation film 25 for forming solder bumps for preparation example 25, and chips C8 to C13 corresponding to the positions of the gold bumps (electrodes) and recesses were used. The evaluation results are shown in Table 11. [Table 11]

[0188] In all of the evaluation chips 25 to 42, solder bumps were sufficiently formed on the gold bumps. The solder bumps were formed only on the electrodes, and no solder particles were present between the electrodes. Since the opening surface of the recess in the solder bump formation film was pressed against the electrode surface, even if there was a fluid phase, there was little possibility that the molten solder would leak from the electrode surface, and the solder bumps could be formed stably.

[0189] <Solder bump formation> Step f4: Solder bump formation: formic acid atmosphere Solder bumps were formed and evaluated using the same method as in step f3, except that iii) in step f3 was changed to the following method. The evaluation results are shown in Table 12. iii) The glass plate with the evaluation substrate 1 placed on the chip C8 was placed and fixed on the hot plate of a formic acid furnace (manufactured by Shinko Seiki Co., Ltd.), and a stainless steel weight was placed on the evaluation substrate 1. After evacuating the furnace, it was treated in a formic acid atmosphere at 150°C for 3 minutes and returned to atmospheric pressure. Then, the uppermost weight and the evaluation substrate 1 were removed in that order. Next, the chip C8 was immersed in a methanol solution, the fluid phase was washed off, and it was vacuum dried (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 results of evaluations performed in the same manner as above are shown in Table 12.

[0192] Good solder bumps were formed on all of the evaluation chips 43 to 60. The good results were achieved because a reducing atmosphere was created by using formic acid.

[0193] <Solder bump formation> Process f5: Solder bump formation: vacuum pressure Solder bumps were formed and evaluated in the same manner as in step f3, except that iii) of step f3 was changed to the following method. The evaluation results are shown in Table 13. iii) The glass plate with the evaluation substrate 1 placed on the chip C8 was placed on the carrier film of a vacuum pressure laminator (MVL-500: manufactured by Japan Steel Works, Ltd.). The upper and lower heating plate temperatures were set to 145°C, and the processing was performed at a pressure of 0.5 MPa and a pressure time of 3 s. After that, the evaluation substrate 1 was removed. Next, the chip C8 was immersed in a methanol solution, the fluid phase was washed off, and the chip was vacuum dried (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 step f5, solder bumps were formed in the combinations shown in Table 13 to obtain evaluation chips 62 to 78. The results of evaluations performed in the same manner as above are shown in Table 13.

[0196] Good solder bumps were formed on all of the evaluation chips 61 to 78. The good results were achieved because the vacuum pressure allowed pressure to be applied uniformly across the surface.

[0197] <Preparation of evaluation chip with solder bumps> Step e3: Preparation of evaluation chip Six types of chips with copper bumps (10 mm x 10 mm, thickness: 0.5 mm) were prepared as shown below. Chip C14: Size 8 x 4 μm, X-direction pitch 16 μm, Y-direction pitch 8 μm, height: 3 μm, number of bumps 382,000 Chip C15: Size 16μm x 8μm, X-direction pitch 32μm, Y-direction pitch 16μm, height: 5μm, number of bumps 95700 Chip C16: Size 24μm×12μm, X-direction pitch 48μm, Y-direction pitch 24μm, height: 8μm, number of bumps 42500 Chip C17: Size 72μm x 36μm, X-direction pitch 144μm, Y-direction pitch 72μm, height: 10μm, number of bumps 4700 Chip C18: Size 96μm x 48μm, X-direction pitch 192μm, Y-direction pitch 96μm, height: 13μm, number of bumps 2600 Chip C19: Size 140μm×70μm, X-direction pitch 280μm, Y-direction pitch 140μm, height: 18μm, number of bumps 1200 In addition, three alignment marks are arranged on each.

[0198] <Solder bump formation> Process f6: Solder bump formation: vacuum pressure Solder bumps were formed and evaluated in the same manner as in step f3, except that iii) of step f3 was changed to the following method. The evaluation results are shown in Table 14. iii) The glass plate with the evaluation substrate 1 placed on the chip C14 was placed on the carrier film of a vacuum pressure laminator (MVL-500: manufactured by Japan Steel Works, Ltd.). The upper and lower heating plate temperatures were set to 150°C, and the processing was performed at a pressure of 0.5 MPa and a pressure time of 10 s. After that, the evaluation substrate 1 was removed. Next, the chip C14 was immersed in a methanol solution, the fluid phase was washed off, and the chip was vacuum dried (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 results of evaluations performed in the same manner as above are shown in Table 14.

[0201] Even in the evaluation chips 79 to 96 having Cu bumps (electrodes), good solder bump formation was achieved.

[0202] <Preparation of connection structure> Step g2: Preparation of evaluation board Six types of gold bumped substrates (40 x 40 mm, thickness: 0.5 mm) were prepared as shown below. The arrangement of these gold bumps is such that each is positioned relative to the gold bumps of chips C8 to C13, and there are three alignment marks to enable alignment. These gold bumps also have lead wires formed for resistance measurement. Substrate D8...Corresponding chip: Chip C8 / Size 8 x 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 16μm x 8μm, X-direction pitch 32μm, Y-direction pitch 16μm, Height: 5μm, 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] Step h2: Bonding of electrodes According to the following steps i) to iii), the evaluation chip with solder bumps produced in step f5 was connected to the evaluation board with gold bumps via the solder bumps. i) The substrate on which the gold bumps were formed was fixed to the stage of a flip chip bonder (FC3000: manufactured by Toray Industries, Inc.). The evaluation chip on which the solder bumps were formed was picked up by the heating and pressurizing head and placed in a position where the gold bumps faced each other from the alignment mark. ii) The substrate with the evaluation chip mounted thereon was placed on the lower heating plate of a formic acid reflow furnace (batch-type vacuum soldering device manufactured by Shinko Seiki Co., Ltd.), and a stainless steel weight was placed on the top of the evaluation chip. iii) The formic acid vacuum reflow furnace was operated, and after evacuation, formic acid gas was filled, and the lower hot plate was heated to 150°C and heated for 5 minutes. After that, the formic acid gas was discharged by evacuation, and nitrogen replacement 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 viscosity-adjusted underfill material (Hitachi Chemical Co., Ltd., CEL series) was placed between the evaluation chip and evaluation board, and after filling by evacuation, it was cured at 125°C for 4 hours to produce a connection structure between the evaluation chip and evaluation board.

[0204] <Evaluation of connection structures> A conductive resistance test and an insulation resistance test were performed on some of the obtained connection structures 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] <Preparation of connection structure> Step g3: Preparation of evaluation board Six types of copper bumped substrates (40 x 40 mm, thickness: 0.5 mm) were prepared as shown below. The Cu bumps are arranged in positions corresponding to the Cu bumps of chips C14 to C19, and there are three alignment marks to allow for alignment. These Cu bumps also have lead wires formed for resistance measurement. Substrate D14...Corresponding chip: Chip C14 / Size 8 x 4 μm, X-direction pitch 16 μm, Y-direction pitch 8 μm, height: 3 μm, 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] Step h3: Bonding of electrodes According to the following steps i) to iii), the evaluation chip with solder bumps produced in step f6 was connected to an evaluation board 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 Co., Ltd.) was dropped onto the surface on which the Cu bumps were formed. The substrate was rotated at 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 on which the solder bumps were formed was picked up by the heating and pressurizing head, and was positioned so that the bumps faced each other from the alignment mark. The substrate with the evaluation chip was placed on the lower heating 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 the top of the evaluation chip. iii) The formic acid vacuum reflow furnace was operated, and after evacuation, formic acid gas was filled, and the lower hot plate was heated to 160°C and heated for 3 minutes. After that, the formic acid gas was discharged by evacuation, and nitrogen replacement 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 viscosity-adjusted underfill material (Hitachi Chemical Co., Ltd., CEL series) was placed between the evaluation chip and evaluation board, and after filling by evacuation, it was cured at 125°C for 4 hours to produce a connection structure between the evaluation chip and evaluation board.

[0210] <Evaluation of connection structures> A conductive resistance test and an insulation resistance test were performed on some of the obtained connection structures in the same manner as in step h1. The results are shown in Tables 18, 19, and 20.

[0211] [Table 18]

[0212] [Table 19]

[0213] [Table 20]

[0214] Stable connection characteristics were also observed when Cu electrodes were joined together via solder bumps formed on the Cu electrodes. [Explanation of symbols]

[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, 62...recess, 111...solder fine particle, F...fluidizer, 600...base, 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; Equipped with The method for producing a member for forming a solder bump, wherein the average particle size of the solder particles is 1 to 35 μm and the CV value is 20% or less.

6. The manufacturing method described in claim 5, 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.

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 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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