Member for forming solder bumps and method for manufacturing electrode substrate with solder bumps

Abstract

A solder bump forming member comprising a base having a plurality of recesses, and solder particles within the recesses, the solder bump forming member being such that: the average particle diameter of the solder particles is 1-35 µm; the C.V. value is 20% or less; and some of the solder particles project from the recesses, or, in a cross-sectional view, H1<H2, where H1 is the depth of the recesses, and H2 is the height of the solder particles.

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

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

Means for Solving the Problems

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

[0011] One aspect of the present invention relates to a member for forming solder bumps, which includes a substrate having a plurality of recesses and solder particles in the recesses, wherein the average particle diameter of the solder particles is 1 to 35 μm, the C.V. value is 20% or less, and in a cross-sectional view, when the depth of the recess is H1 and the height of the solder particles is H2, H1 < H2.

[0012] 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.

[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 preparation step of preparing a base having a plurality of recesses and solder particles; a accommodating step of accommodating at least some of the solder particles in the recesses; and a fusion step of fusing the solder particles accommodated in the recesses to form solder particles within the recesses, with some of the solder particles protruding from the recesses.

[0016] 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.

[0017] In one embodiment of the method for producing a solder bump forming member, the CV value of the solder fine particles may exceed 20%.

[0018] 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.

[0019] In the fusing step in one embodiment of the method for producing a solder bump-forming member, the solder fine particles may be fused in a reducing atmosphere.

[0020] 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 opposing a surface of the solder bump forming member having a recess to a surface of the substrate having electrodes, thereby bringing the solder particles and the electrodes into contact; and a heating step of heating the solder particles to a temperature equal to or higher than the melting point of the solder particles.

[0021] In the heating step in one aspect 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 particles and the electrodes are in contact with each other under pressure.

[0022] 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.

[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 after the placing step and before the heating step.

[0024] 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 in the heating step.

[0025] 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.

[0026] 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

[0027] 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

[0028] [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 shapes 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 recess 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(a) is an SEM image of a part of the gold bumps of chip C4, and FIG. 8(b) is an SEM image after forming solder bumps on the gold bumps of chip C4 using the member for forming solder bumps of Production Example 8. [Figure 9] FIG. 9 is a cross-sectional view schematically showing an example of a substrate.

Embodiments for Carrying Out the Invention

[0029] 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.

[0030] <Solder bump forming materials> In one embodiment, a solder bump forming member includes a base having a plurality of recesses and solder particles in the recesses, the solder particles having an average particle size of 1 to 35 μm and a CV value of 20% or less, and some of the solder particles protruding from the recesses. Also, in one embodiment, a solder bump forming member includes a base having a plurality of recesses and solder particles in the recesses, the solder particles having an average particle size of 1 to 35 μm and a CV value of 20% or less, and when the depth of the recesses is H1 and the height of the solder particles is H2, in a cross-sectional view, H1 <H2である。

[0031] FIG. 1 is a cross-sectional view schematically showing a solder bump forming member according to an embodiment. The solder bump forming member 10 includes a substrate 60 having a plurality of recesses 62 and solder particles 1 in the recesses 62. In a predetermined longitudinal section of the solder bump forming member 10, one solder particle 1 is arranged to be aligned in the lateral direction (left-right direction in FIG. 1) in a state separated from an adjacent solder particle 1. The solder particle 1 may be in contact with its side surface and / or bottom surface within 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.

[0032] In the solder bump forming member 10, a part of the solder particles 1 protrudes from the recesses. It can be said that at least the top of the solder particle 1 protrudes from the recess 62 of the solder bump forming member 10 (protrudes from the main surface of the substrate 60). Specifically, in a cross-sectional view perpendicular to the main surface of the solder bump forming member 10, when the depth of the recess 62 is H1 and the height of the solder particle 1 is H2, H1 < H2. The height H2 of the solder particle 1 refers to the length from the bottom surface of the recess 62 to the top of the solder particle 1 in the cross-sectional view. The degree of protrusion of the solder particle 1 is not particularly limited, but from the viewpoint of more suitable bonding with the electrode, the ratio of H2 to H1 (H2 / H1) can be 1.02 or more, and may be 1.07 or more. The upper limit of the ratio may be 3.00 from the viewpoint of suppressing the dropout of the solder particles 1.

[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. Also, 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 the flat portion 11 and the spherical crown-shaped curved surface portion. The ratio (A / B) of the diameter A of the flat portion 11 to the diameter B of the solder particle 1 may be, for example, more than 0.01 and less than 1.0 (0.01 < A / B < 1.0), and may 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 62, the detachment of the solder particle 1 from the solder bump forming member 10 is less likely to occur. As will be described later, 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.

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

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

[0041] The solder particles 1 may contain tin or a tin alloy. Examples of the tin alloy that can be used 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℃)

[0042] 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)

[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] (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.

[0048] 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.

[0049] The coating layer can be formed by laminating, dipping in a solution, coating, painting, impregnation, sputtering, plating, or the like.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] A specific configuration of the base 60 will be described below.

[0054] (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.

[0055] (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 a thermoplastic, thermosetting, or photosetting material may be used. 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 according to their functions, such as selecting a material with suitable wettability with solder for the material of the recess that comes into contact with the solder. For example, FIG. 9 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).

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] (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.

[0061] (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.

[0062] 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.

[0063] (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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] <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 containing step of containing at least some of the solder particles in the recesses, and a fusion step of fusing the solder particles contained in the recesses to form solder particles within the recesses, with some of the solder particles protruding from the recesses.

[0068] A method for manufacturing the solder bump forming member 10 according to the first embodiment will be described with reference to FIGS.

[0069] 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.

[0070] The distance L between adjacent recesses is not particularly limited, but may be 0.1 times or more the average particle diameter of the solder particles contained therein, and may be 0.2 times or more. The upper limit of this value may be, for example, 0.3 times. The distance between recesses is not the center-to-center distance between the recesses, but the distance from edge to edge of the recess opening.

[0071] 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.

[0072] 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).

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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℃)

[0079] 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)

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] By adjusting the amount of solder particles 111 accommodated in recesses 62, the degree of protrusion of solder particles 1 can be adjusted. The amount of solder particles 111 accommodated in recesses 62 is, for example, preferably 20% or more of the volume of recesses 62, more preferably 30% or more, even more preferably 50% or more, and most preferably 60% or more. This allows some of the solder particles to protrude from recesses 62. Also, variation in the amount accommodated is suppressed, making it easier to obtain solder particles with a smaller particle size distribution.

[0087] Generally, solder materials have the property of forming spherical shapes due to their own surface tension when they are in a molten state in an environment above their melting point.

[0088] The solder particles 111 contained in the recesses 62 are united by a fusion process described below to become solder particles 1. The height of the obtained solder particles 1 is greater than the depth of the recesses 62, and the solder particles 1 protrude from the recesses 62. Therefore, if the diameter of the solder particles 1 is greater than the depth of the recesses 62, the solder particles 1 protrude from the recesses 62. The diameter of the solder particles 1 can be adjusted by the shape of the recesses 62 and the amount of solder particles 111 contained in the recesses 62, and therefore the degree of protrusion from the recesses 62 can be adjusted.

[0089] In addition, when the solder particles 111 melt in the fusion process described later, depending on the material of the bottom and inner wall of the recess 62, the bottom and inner wall are wetted and spread, and at least a part of the solder particle 1 is in contact with the bottom and / or inner wall of the recess 62. As a result, a flat part may be formed at least in a part of the solder particle 1. The size of this flat part varies depending on the combination of the surface material of the bottom and inner wall of the recess 62 and the solder composition constituting the solder particles 111. Therefore, the shape of the solder particle 1 may be a perfect sphere, an ellipsoid, a flattened sphere, a part having a flat part, or the like. The base 60 may be an inorganic material such as glass or silicon, or an organic material such as plastic or resin, and the bottom and inner wall of such a material generally tend to have low wettability with solder, and the solder particle 1 tends to be roughly spherical. Therefore, it is also possible to assume that the solder particle 1 is a sphere close to a perfect sphere, and approximate the height of the solder particle 1 to the diameter of the solder particle 1. Since the diameter of the solder particles 1 can be calculated from the total volume of the solder particles 111 filled in the recesses 62, the amount of solder particles 111 required for the solder particles 1 to protrude from the recesses 62 can be calculated.

[0090] Assuming that all of the solder particles 111 filled in the recess 62 melt and coalesce to become solder particles 1, and that the solder particles 1 are spherical, the amount of solder particles 111 required for the solder particles 1 to protrude from the recess 62 can be shown.

[0091] When the upper diameter (opening width b) of recess 62 is L and the depth of recess 62 is D, the aspect ratio of the recess is represented by L / D. In this case, the filling rate of solder particles 111 in recess 62 is preferably 66 volume % or more when the aspect ratio is 1, 38 volume % or more when the aspect ratio is 0.75, 17 volume % or more when the aspect ratio is 0.5, and 5 volume % or more when the aspect ratio is 0.25.

[0092] In order to suppress the variation in the amount of filling, it is advisable to select the average particle diameter, grain size, etc. of the solder particles 111 according to the size of the recess 62 and the ratio of the diameter to the depth (aspect ratio). For example, when the diameter of the recess 62 is 4 μm and the depth is 4 μm (aspect ratio is 1), by using solder particles 111 with an average particle diameter of 1 to 2 μm or less, the variation in the amount of filling the recess 62 can be suppressed, the variation in the diameter of the obtained solder particles 1 is also suppressed, and the variation in the amount of protrusion (height) from the recess 62 can also be easily suppressed. If the variation in the amount of protrusion (height) from the recess 62 is suppressed, the contact between the solder particles 1 and the electrode is stable when the solder particles 1 are pressed against the electrode, and the variation in the formation of the solder bump is easily suppressed.

[0093] In order to facilitate the solder particles 111 contained in the recess 62 to gather together when they melt and coalesce, it is advisable to adjust the bottom shape of the recess 62. For example, it is preferable to select a bottom shape that has a gradient toward the center, as shown in Figures 4(b), (e), (g), and (h). In particular, when the aspect ratio of the recess 62 is large, in other words, when the recess 62 has a wide opening width and a shallow shape, when the solder particles 111 melt, some of the solder particles 111 tend to remain without being coalesced, so it is preferable to adjust the bottom shape of the recess 62 as shown in Figures 4(b), (e), (g), and (h).

[0094] 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.

[0095] 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 in the recesses 62, with parts of the solder particles 1 protruding from 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] In the above method, the shape of the recesses 62 of the base 60 can be freely designed by lithography, machining, imprinting technology, 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.

[0105] <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 arranging the surface of the solder bump forming member having a recess and the surface of the substrate having the electrodes so as to bring the solder particles and 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.

[0106] 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.

[0107] 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.

[0108] 6(a) and 6(b) are cross-sectional views that show a schematic example of a manufacturing process of an electrode substrate with solder bumps. The base 60 shown in FIG. 6(a) has one solder particle 1 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 the opening side surface of the recess 62 of the base 60, and the base 60 and the substrate 2 are brought close to each other until the solder particles 1 accommodated in the recess 62 of the base 60 come into contact with the electrodes 3 (arrows A and B in FIG. 6(a)). There is no particular limit to the number of solder particles 1 that come into contact with each electrode 3, and there may be one particle for one electrode, or there may be multiple particles for one electrode. In addition, since the force acting between the solder particles 1 and the recesses 62 (for example, intermolecular forces such as van der Waals forces) is greater than the gravity acting on the solder particles 1, even if the main surface of the base 60 is faced downward, the solder particles 1 do not fall off but remain in the recesses 62. Furthermore, when at least a portion of the solder particles 1 is in contact with the bottom and / or inner wall of the recesses 62 and has a flat portion, the solder particles 1 are in close contact with the recesses 62 and are less likely to fall off.

[0109] In this state, the entire member is heated to at least a temperature (e.g., 130 to 260°C) higher than the melting point of the solder particles 1, whereby the solder particles 1 melt and a solder bump is formed on the electrode 3. From the viewpoint of more suitably joining the solder particles 1 to the electrode 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 particles 1 and the electrode 3 are in contact 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 20 to 600 MPa in the directions of arrows A and B in FIG. 6(a).

[0110] 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.

[0111] For details about the reducing atmosphere, the description of the method for producing a solder bump member can be referred to as appropriate.

[0112] After the heating step, the whole is cooled, so that the electrode 3 and the solder bump 1A formed by melting the solder particles 1 are fixed to each other, and the two are electrically connected. The manufacturing method of the 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 bump 1A is formed on the electrode 3, the solder bump forming member 10 is removed from the substrate 2 (removal step) to obtain the 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. It is preferable to have alignment marks on the surface of the solder bump forming member and the substrate, since this makes it easier to align them. For example, the recess of the solder bump forming member and the electrode surface side of the substrate surface are arranged in advance at a position where the recess of the solder bump forming member and the electrode position on the substrate surface face each other. Solder particles are placed in the recesses of the solder bump forming member, the opening side of the recesses of the solder bump forming member is opposed to the electrode surface side of the substrate, and the alignment mark is used to adjust the position of the electrode on which the solder bump is to be formed and the recesses of the solder bump forming member, and then the solder bump can be formed on the electrode by the above-mentioned various methods. By this method, the solder bump can be formed only on a specific electrode. For example, by providing a recess of the solder bump forming member in advance at a position opposite to the position of a specific electrode for multiple electrodes on the surface of the substrate, the solder bump can be formed only on a specific electrode on the surface of the substrate. Furthermore, one solder bump can be formed on one electrode.

[0113] 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 of 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 or rubbing the substrate surface with a nonwoven fabric or a bundle of fibers.

[0114] 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.

[0115] <Method of Manufacturing Connection Structure> 7(a) and 7(b) are cross-sectional views showing an example of a manufacturing process of the connection structure. A manufacturing method of the 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. Also, another substrate 4 having a plurality of other electrodes 5 is prepared. Then, both are arranged so that the solder bumps 1A and the other electrodes 5 face each other. Thereafter, while the solder bumps 1A and the other electrodes 5 are in contact with each other, the solder bumps 1A are heated 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 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. 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 is blocked from 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.

[0116] 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 for these, 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 on the electrode 5, and a more stable bond can be achieved between the electrode 3 and the electrode 5 via the solder layer 1B.

[0117] 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 for these, a continuous furnace, a conveyor furnace, etc. can be used.

[0118] 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 or 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 near 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 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, the flux components are washed away, and the flux residue can suppress corrosion of the solder layer 1B and the electrodes 3 and 5.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] A method of manufacturing the connection structure may also be a method of simultaneously performing solder bonding and sealing between electrodes with resin. A connection structure can be obtained in the same manner as in the case of using a film containing a flux component, except that an insulating resin layer (resin film) is used instead of the film containing a flux component. As a result, the electrode 3 and the other electrode 5 are connected via the solder bump 1A, and the space between the substrate 2 and the substrate 4 is filled with the insulating resin layer. At this time, if the insulating resin layer is a material having thermosetting properties, the substrate 2 and the substrate 4 are firmly fixed, the electrode 3, the solder layer 1B, and the other electrode 5 are sealed, and corrosion and oxidation of the electrodes and solder due to moisture, oxygen, etc. are suppressed, which is preferable.

[0123] Heating methods for melting the solder bumps 1A include, for example, 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 under vacuum, and a method of using radiation such as infrared rays. In addition to or in combination with the heating method using the heating plate or infrared rays described above, a method of heating the solder bumps 1A through heated gas and 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.

[0124] 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 and other electronic components, which should not be heated, in the vicinity of the electrodes 3 and 5, the solder bumps 1A can be melted and joined.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. EXAMPLES

[0129] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0130] <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, 100 μm thick) was prepared having multiple recesses with an opening diameter of 2.3 μmφ, a bottom diameter of 2.0 μmφ, and a depth of 1.5 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 to form the solder particles. A film for forming solder bumps with solder particles in the recesses was obtained.

[0131] <Evaluation of films for solder bump formation> A portion of the film for forming solder bumps obtained through step c1 was fixed to the surface of a SEM observation pedestal, and platinum sputtering was applied to the surface. The diameters of 300 solder particles were measured using an SEM, and the average particle diameter and CV value were calculated. The results are shown in Table 2. In addition, the surface shape of a portion of the film for forming solder bumps 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.

[0132] (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.

[0133] (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. A film for forming solder bumps having solder particles in the recesses was obtained.

[0134] (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.

[0135] (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 in the furnace was then adjusted to 130°C and held 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 in the furnace was then lowered to room temperature to form solder particles. A film for forming solder bumps having solder particles in the recesses was obtained.

[0136] (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.

[0137] (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 to form a film for forming solder bumps.

[0138] (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.

[0139] [Table 1]

[0140] [Table 2]

[0141] <Preparation of evaluation chip with solder bumps> Step d1: 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 x 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

[0142] Step e1: Solder bump formation 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 0.3 mm thick glass plate was placed on the lower hot plate of a formic acid reflow furnace (a batch-type vacuum soldering device manufactured by Shinko Seiki Co., Ltd.), and the evaluation chip was placed on the glass plate with the gold bumps facing up. ii) The solder bump film was placed with the exposed solder particle surface facing downwards so that the gold bump surface of the evaluation chip was in contact with the solder particles. A 0.3 mm thick glass plate was then placed on top of the solder bump film to bring the solder particles into contact with the gold bumps. 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, and the lower hot plate was returned to room temperature, and the inside of the furnace was opened to the atmosphere. The top glass plate and the film for forming solder bumps were removed in that order to obtain an evaluation chip with solder bumps.

[0143] <Solder bump evaluation> The evaluation chip obtained through step e1 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, a laser microscope (Olympus Corporation, LEXT OLS5000-SAF) was used to measure the height of the solder bumps from the gold bump, and the average value for 100 bumps was calculated. The results are shown in Table 3.

[0144] Solder bumps were formed in the same manner as above, 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 3.

[0145] Figure 8(a) is an SEM image of a portion of the gold bumps of chip C4. Figure 8(b) is an SEM image of the state after solder bumps were formed on the gold bumps of chip C4 using the film for forming solder bumps of Preparation Example 8. The solder bumps are formed only on the gold bumps, and no solder particles or solder material originating from the solder bumps are found between the gold bumps.

[0146] [Table 3]

[0147] <Preparation of connection structure> Step f1: 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

[0148] Step g1: Bonding of electrodes According to the following steps i) to iii), the evaluation chip with solder bumps produced in step e1 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 125°C for 3 hours to produce a connection structure between 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

[0149] <Evaluation of connection structures> A conductive resistance test and an insulation resistance test were performed on some of the obtained connection structures as follows.

[0150] (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 4. 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

[0151] (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 a temperature of 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 value was measured at the solder joints (4 places) of the chip corners that received the greatest impact, and when the measured value increased by 5 times or more from the initial resistance, it was deemed 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 5. 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.

[0152] (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. 9 The 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 6. 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%

[0153] [Table 4]

[0154] [Table 5]

[0155] [Table 6]

[0156] <Preparation of film for solder bump formation> (Example 25) Step h1: Preparation of substrate A liquid photosensitive resist (Hitachi Chemical Co., Ltd., AH series) was applied to a thickness of 1.5 μm on a 6-inch silicon wafer by spin coating. The photosensitive resist on this silicon wafer was exposed and developed to obtain a base 25 having a recess with an opening diameter of 3.1 μmφ, a bottom diameter of 2.0 μmφ, and a depth of 1.5 μm (the bottom diameter of 2.0 μmφ is located at the center of the opening diameter of 2.3 μmφ when viewed from above). These recesses were arranged at positions (X-direction pitch, Y-direction pitch) relative to the electrode arrangement pattern of the evaluation substrate. In addition, three alignment marks were arranged on the surface of the base 25 at the same time as the recesses were formed. An overview of the base 25 is shown in Table 7.

[0157] [Table 7]

[0158] Solder particles were obtained in the same manner as in step a1, and the solder particles were placed in the recesses in the same manner as in step b1, except that a base 25 was used, and a film for forming solder bumps 25 having solder particles in the recesses was obtained by step c3.

[0159] <Evaluation of films for solder bump formation> A portion of the film 25 for forming solder bumps was fixed to the surface of a SEM observation pedestal, and platinum was sputtered on the surface. The diameters of 300 solder particles were measured using the SEM, and the average particle diameter and CV value were calculated. The results are shown in Table 8. In addition, the surface shape of a portion of the film 25 for forming solder bumps 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 of 300 particles was calculated. The results are shown in Table 8.

[0160] [Table 8]

[0161] (Examples 26-30) A film for forming solder bumps was produced and evaluated in the same manner as in Preparation Example 25, except that the thickness of the photosensitive resist was changed to the depth value shown in Table 7, the size of the recesses was also changed as shown in Table 7, and the positions of the recesses were set to positions relative to the electrode arrangement pattern of the evaluation substrate shown in Table 7. The results are shown in Table 8.

[0162] <Preparation of evaluation chip with solder bumps> Step d2: Preparation of evaluation chip Six types of chips with gold bumps (5 x 5 mm, thickness: 0.5 mm) were prepared as shown below. Chip C8: Electrode size: 8 μm x 4 μm, pitch: 16 μm in X direction, 8 μm in Y direction, number of bumps: 180,000 Chip C9...Electrode size: 16μm x 8μm, pitch: X direction 32μm, Y direction 16μm, number of bumps: 46,000 Chip C10: Electrode size: 24 μm x 12 μm, pitch: X direction 48 μm, Y direction 24 μm, number of bumps: 15,000 Chip C11: Electrode size: 72 μm x 36 μm, pitch: 144 μm in the X direction, 72 μm in the Y direction, number of bumps: 3,400 Chip C12: Electrode size: 96 μm x 48 μm, pitch: X direction 192 μm, Y direction 96 μm, number of bumps: 850 Chip C13: Electrode size: 140 μm x 70 μm, pitch: X direction 280 μm, Y direction 140 μm, number of bumps: 420

[0163] Step e2: Solder bump formation The film 25 for forming solder bumps was placed on the stage of FC3000W (manufactured by Toray Engineering Co., Ltd.), and the evaluation chip C8 was attached to the head and picked up. Using the alignment marks of both, the solder particles arranged in the recesses of the film 25 for forming solder bumps and the electrodes of the evaluation chip C8 were aligned, and the evaluation chip C8 was temporarily placed on the film 25 for forming solder bumps. Thereafter, it was placed on the lower hot plate of a formic acid reflow furnace (manufactured by Shinko Seiki Co., Ltd., batch type vacuum soldering device), and after evacuation, formic acid gas was filled, the lower hot plate was heated to 145°C, and heated for 1 minute. Thereafter, the formic acid gas was discharged by evacuation, nitrogen replacement was performed, the lower hot plate was returned to room temperature, the inside of the furnace was opened to the atmosphere, the solder particles were transferred onto the electrodes of the evaluation chip C8, and solder bumps were formed.

[0164] <Solder bump evaluation> For the evaluation chip obtained through step e2, the number of solder particles transferred to 300 electrodes (number of solder bumps) was counted and the transfer rate was calculated. In addition, the height of the solder bumps was measured using a laser microscope (Olympus Corporation, LEXT OLS5000-SAF) and the average value for 300 bumps was calculated. The results are shown in Table 9.

[0165] [Table 9]

[0166] Except for using the films 26 to 30 for forming solder bumps and the evaluation chips C9 to C13, solder bumps were formed in the same manner as in step e2. Furthermore, the transfer rate and average height were calculated for each evaluation chip in the same manner as above. The results are shown in Table 9.

[0167] <Preparation of connection structure> Six types of evaluation substrates with gold bumps (70 x 25 mm, thickness: 0.5 mm) were prepared as shown below. The gold bumps were positioned opposite the gold electrodes of the evaluation chips C8 to C13 described above, and alignment marks were placed on the substrate. In addition, some of the gold bumps also had lead wiring for resistance measurement. Substrate D8: Area 8 μm x 4 μm, pitch: X direction 16 μm, Y direction 8 μm, height: 2 μm, number of bumps: 180,000 Board D9: Area 16μm x 8μm, pitch: X direction 32μm, Y direction 16μm, height: 3μm, number of bumps: 46,000 Substrate D10: Area 24μm x 12μm, pitch: X direction 48μm, Y direction 24μm, height: 3μm, number of bumps: 15,000 Substrate D11: Area 72 μm × 36 μm, pitch: X direction 144 μm, Y direction 72 μm, height: 3 μm, number of bumps: 3,400 Substrate D12: Area 96 μm × 48 μm, pitch: X direction 192 μm, Y direction 96 μm, height: 3 μm, number of bumps: 850 Substrate D13: Area 140 μm × 70 μm, pitch: X direction 280 μm, Y direction 140 μm, height: 3 μm, number of bumps: 420

[0168] Step g2: Bonding of electrodes According to the following steps i) to iii), the evaluation chip with solder bumps produced in step e2 was connected to an evaluation board with gold bumps via solder bumps. i) Evaluation substrate D8 with gold bumps was placed on the stage of an FC3000W (manufactured by Toray Engineering Co., Ltd.), evaluation chip C8 with solder bumps was picked up with the head, and the gold electrodes were faced to each other using the alignment marks on both sides. Evaluation chip C8 with solder bumps was then placed on evaluation substrate D8 with gold bumps, and pre-bonding sample 8 was obtained. ii) The pre-bonding sample 8 obtained in i) was placed on the lower hot plate of a formic acid reflow furnace (batch-type vacuum soldering device manufactured by Shinko Seiki Co., Ltd.). 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 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 3 hours to produce a connection structure between the evaluation chip and evaluation board. The combination of each material in the connection structure is as follows. (8) Chip C8 / Solder bump forming film 25 / Substrate D8 (9) Chip C9 / Solder bump forming film 26 / Substrate D9 (10) Chip C10 / Solder bump forming film 27 / Substrate D10 (11) Chip C11 / Solder bump forming film 28 / Substrate D11 (12) Chip C12 / Solder bump forming film 29 / Substrate D12 (13) Chip C13 / Solder bump forming film 30 / Substrate D13

[0169] <Evaluation of connection structures> A conductive resistance test and an insulation resistance test were carried out on some of the obtained connection structures in the same manner as above. The results are shown in Tables 10 to 12.

[0170] [Table 10]

[0171] [Table 11]

[0172] [Table 12]

[0173] (Examples 31 to 36) By fabricating a substrate in step h1, preparing an evaluation chip in step d2, and further forming solder bumps in step e2, evaluation chips C8 to C13 with solder bumps formed as shown in Table 9 were obtained.

[0174] <Preparation of connection structure> Six types of evaluation substrates with gold bumps (70 x 25 mm, thickness: 0.5 mm) were prepared as shown below. The gold bumps were positioned opposite the gold electrodes of the evaluation chips C8 to C13 described above, and alignment marks were placed on the substrate. In addition, some of the gold bumps also had lead wiring for resistance measurement. Substrate D8: Area 8 μm x 4 μm, pitch: X direction 16 μm, Y direction 8 μm, height: 2 μm, number of bumps: 180,000 Board D9: Area 16μm x 8μm, pitch: X direction 32μm, Y direction 16μm, height: 3μm, number of bumps: 46,000 Substrate D10: Area 24μm x 12μm, pitch: X direction 48μm, Y direction 24μm, height: 3μm, number of bumps: 15,000 Substrate D11: Area 72 μm × 36 μm, pitch: X direction 144 μm, Y direction 72 μm, height: 3 μm, number of bumps: 3,400 Substrate D12: Area 96 μm × 48 μm, pitch: X direction 192 μm, Y direction 96 μm, height: 3 μm, number of bumps: 850 Substrate D13: Area 140 μm × 70 μm, pitch: X direction 280 μm, Y direction 140 μm, height: 3 μm, number of bumps: 420

[0175] Step g3: Bonding of electrodes According to the following steps i) to vi), the evaluation chip with solder bumps produced in step e2 was connected to an evaluation board with gold bumps via solder bumps. i) The evaluation substrate with gold bumps was set on a spin coater, and the gold bump surface was coated with liquid flux (NS-334, manufactured by Arakawa Chemical Industry Co., Ltd.). ii) The evaluation substrate with gold bumps obtained in i) was placed on the stage of an FC3000W (manufactured by Toray Engineering Co., Ltd.), the evaluation chip with solder bumps was picked up by the head, and the gold electrodes were faced to each other using the alignment marks on both sides. The evaluation chip with solder bumps was then placed on the evaluation substrate with gold bumps, and pre-bonding samples 14 to 19 were obtained. iii) The pre-bonded sample was placed on the lower heating plate of a formic acid reflow furnace (batch-type vacuum soldering device manufactured by Shinko Seiki Co., Ltd.). iv) The formic acid vacuum reflow furnace was operated, and after evacuation, nitrogen gas was filled in, and the lower heating plate was heated to 160°C and heated for 3 minutes. After that, the furnace was evacuated, and nitrogen replacement was performed, the lower heating plate was returned to room temperature, and the inside of the furnace was opened to the atmosphere. v) The bonded samples were immersed in isopropyl alcohol to wash off any flux residue. vi) An appropriate amount of viscosity-adjusted underfill material (Hitachi Chemical Co., Ltd., CEL series) was placed between the evaluation chip and the evaluation board, filled by vacuuming, and then cured at 125°C for 3 hours to create a connection structure between the evaluation chip and the evaluation board. The combination of each material in the connection structure is as follows. (14) Chip C8 / Solder bump forming film 25 / Substrate D8 (15) Chip C9 / Solder bump forming film 26 / Substrate D9 (16) Chip C10 / Solder bump forming film 27 / Substrate D10 (17) Chip C11 / Solder bump forming film 28 / Substrate D11 (18) Chip C12 / Solder bump forming film 29 / Substrate D12 (19) Chip C13 / Solder bump forming film 30 / Substrate D13

[0176] <Evaluation of connection structures> A conductive resistance test and an insulation resistance test were carried out on some of the obtained connection structures in the same manner as above. The results are shown in Tables 13 to 15.

[0177] [Table 13]

[0178] [Table 14]

[0179] [Table 15] [Explanation of symbols]

[0180] 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 particle, 600...base, 601...base layer, 602...recess layer.

Claims

1. A substrate having a plurality of recesses and solder particles in the recesses, The solder particles have an average particle size of 1 to 35 μm and a CV value of 20% or less; a portion of the solder particle protruding from the recess; A solder bump forming member, wherein a flat portion is formed on a part of the surface of the solder particle.

2. A substrate having a plurality of recesses and solder particles in the recesses, The solder particles have an average particle size of 1 to 35 μm and a CV value of 20% or less; In a cross-sectional view, the depth of the recess is H １ The height of the solder particles is H ２ Then, H １ <H ２ and A solder bump forming member, wherein a flat portion is formed on a part of the surface of the solder particle.

3. 3. 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.

4. A preparation step of preparing the solder bump forming member according to any one of claims 1 to 3 and a substrate having a plurality of electrodes; a placement step of placing the surface of the solder bump forming member having the recesses and the surface of the substrate having the electrodes opposite each other to bring the solder particles and the electrodes into 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:

5. The method according to claim 4 , 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 particles and the electrodes are in contact with each other under pressure.

6. The manufacturing method according to claim 4 , further comprising a reduction step of exposing the solder particles to a reducing atmosphere before the placing step.

7. The manufacturing method according to claim 4, further comprising a reduction step of exposing the solder particles to a reducing atmosphere after the placing step and before the heating step.

8. 8. The manufacturing method according to claim 4, 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.

9. 9. The manufacturing method according to claim 4, further comprising a removing step of removing the solder bump forming member from the substrate after the heating step.

10. The manufacturing method according to claim 9 , further comprising, after the removing step, a cleaning step of removing the solder particles not bonded to the electrodes.

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