Method for manufacturing solder particles, solder particles, and conductive composition

Abstract

To provide a solder particle manufacturing method that can prevent adhesion of solder particles on a screening surface at the time of classification with use of a swirling airflow type sieving machine and can achieve high productivity by improvement of yield, and solder particles which can avoid short circuit risk and a conductive composition containing the solder particles.SOLUTION: A solder particle manufacturing method includes: a hardening process in which solder particles are hardened so that hardness K value at the time of 70% compression deformation becomes 850 N / mm2 or more and 1,500 N / mm2 or less; and a classification process in which air flow is compulsorily generated by a classifier, and the solder particles after hardening are classified.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for producing solder particles, solder particles, and a conductive composition. [Background technology]

[0002] Currently available solder particles have a less uniform particle size distribution (wider particle size distribution) compared to metal-coated resin particles, which are generally used as conductive particles, and contain a certain amount of coarse solder particles. Therefore, when connecting wiring patterns using a conductive composition containing currently available solder particles, there is a risk of short circuits occurring during heat crimping due to coarse solder particles 11 present in the unpressurized areas between the wiring patterns 10, as shown in Figure 1. In Figure 1, 12 represents solder particles.

[0003] Therefore, in order to avoid the risk of short circuits, one method for removing coarse solder particles is a classification method using a sieve, and among these, classification using a swirling airflow sieve classifier that uses a sieve and airflow for classification is effective. As an example of a classification method using such a swirling airflow sieve, different types of polyamidine A (manufactured by Mitsubishi Chemical Corporation, trade name "DiaCatch (registered trademark) CHP800") and polyamidine B (manufactured by Mitsubishi Chemical Corporation, trade name "DiaFloc (registered trademark) KP7000") were crushed using a jet mill (manufactured by Nippon Pneumatic Co., Ltd., trade name "PJM-80SP") and classified by sieving. It has been disclosed that particles smaller than 16 μm were classified using a swirling airflow sieving device (manufactured by Seishin Corporation, trade name "Spin Air Sieve SAR-200") (see paragraph

[0114] of Patent Document 1). Furthermore, in Example 6 of paragraph

[0091] of Patent Document 2, it is disclosed that glass particles were processed using a sieving classifier (spin air sieve, manufactured by Seishin Corporation) equipped with a sieve with a mesh size of 10 μm, and the glass particles remaining on the 10 μm sieve were used as glass particles-5. [Prior art documents]

Patent Document

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the above prior art documents only describe classifying polyamide particles or glass particles using a spin air sieve, which is a swirling air flow type sieving machine (manufactured by Seishin Enterprise Co., Ltd.), and there is no description or suggestion that removing coarse solder particles from solder particles by using a spin air sieve, which is a swirling air flow type sieving machine, can avoid the risk of shorts. In addition, when applying a swirling air flow type sieving machine to the classification of soft solder particles, as shown in FIG. 2, the solder particles 12 are deformed into solder particles 15 by the impact of colliding with the sieve 13 (see FIGS. 3A and 3B), adhere to the mesh opening 14 of the sieve 13, resulting in clogging (see FIG. 4), and there is a problem that the productivity decreases due to the reduction in yield.

[0006] The present invention aims to solve the above-mentioned various problems and achieve the following objects. That is, the present invention aims to provide a method for manufacturing solder particles that can prevent the adhesion of solder particles on the sieve surface during classification using a swirling air flow type sieving machine, can achieve high productivity by improving the yield, and can avoid the risk of shorts, as well as a conductive composition containing the solder particles and the solder particles.

Means for Solving the Problems

[0007] The means for solving the above problems are as follows. That is, <1> The hardness K value of the solder particles at 70% compression deformation is 850 N / mm 2 or more and 1,500 N / mm 2The curing process is as follows: A classification process in which an airflow is forcibly generated by a classification device to classify the hardened solder particles, This is a method for producing solder particles, characterized by containing [a specific ingredient / material]. <2> In the aforementioned hardening process, the hardness K value at 70% compression deformation is 850 N / mm². 2 The solder particles that are less than the above <1> This is a method for manufacturing solder particles as described above. <3> In the curing process, the solder is heated in an oxygen-containing atmosphere at a temperature below (the melting point of the solder particles - 15°C), <1> from <2> This is a method for manufacturing solder particles as described in one of the following. <4> The classification is carried out in an oxygen-containing atmosphere. <1> from <3> This is a method for manufacturing solder particles as described in one of the following. <5> The classification apparatus is a device that generates an airflow by blower suction to cause solder particles to swirl and collide with the sieve surface for classification. <1> from <4> This is a method for manufacturing solder particles as described in one of the following. <6> The hardness K value at 70% compression deformation is 850 N / mm². 2 More than 1,500N / mm 2 The solder particles are characterized by the following: <7> The number average particle size is 1 μm or more, <6> These are the solder particles described. <8> The proportion of coarse solder particles with a number particle size 1.25 times or more larger than the number-average particle size of the aforementioned solder particles is 0.5% or less. <7> These are the solder particles described. <9> The following comprises Sn and at least one selected from Bi, Ag, Cu, and In. <7> from <8> These are solder particles as described in one of the following. <10> The aforementioned <6> from <9> This conductive composition is characterized by containing solder particles as described in any of the above. [Effects of the Invention]

[0008] According to the present invention, it is possible to solve the aforementioned problems in the conventional method, achieve the aforementioned objectives, prevent solder particles from adhering to the sieve surface during classification using a swirling airflow type sieve classifier, and improve the yield of classification to enable high productivity. Furthermore, it is possible to provide solder particles that can avoid the risk of short circuits and a conductive composition containing said solder particles. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram illustrating that when commercially available solder particles are used as conductive particles, a short circuit occurs due to coarse solder particles. [Figure 2] Figure 2 shows how, in classification using a swirling airflow sieve classifier, soft solder particles deform upon impact with the sieve, causing them to adhere to the sieve mesh and resulting in clogging. [Figure 3A] Figure 3A shows an example of solder particles that have been deformed by colliding with a sieve during classification. [Figure 3B] Figure 3B shows another example of solder particles that have been deformed by colliding with the sieve during classification. [Figure 4] Figure 4 shows a sieve in a state where deformed solder particles have adhered to the mesh of the sieve, causing clogging. [Figure 5] Figure 5 shows how hardened solder particles collide with the sieve and bounce back when classified using a swirling airflow sieve classifier. [Figure 6] Figure 6 shows an example of solder particles that remain undeformed even after colliding with a sieve during classification. [Figure 7] Figure 7 shows a sieve after classification, in which the solder particles are not adhered to the mesh of the sieve. [Modes for carrying out the invention]

[0010] (Method for manufacturing solder particles) The method for manufacturing solder particles of the present invention is such that the solder particles have a hardness K value of 850 N / mm when compressed by 70% 2 or more and 1,500 N / mm 2 or less in a curing step of curing, and a classification step of classifying the cured solder particles by forcibly generating an air flow using a classification device, and further includes other steps as necessary.

[0011] In the present invention, since the solder particles are cured in the curing step so that the hardness K value when compressed by 70% is 850 N / mm 2 or more and 1,500 N / mm 2 or less, even when classification is performed using a swirling air current type sieving machine, as shown in FIG. 5, the hard solder particles 12 that have collided with the sieve 13 do not deform (see FIG. 6), bounce back, and do not adhere to the mesh opening 14 of the sieve 13, so that clogging of the sieve does not occur (see FIG. 7). As a result, high productivity can be achieved by improving the yield of classification

[0012] <Curing Step> The curing step is a step of curing the solder particles so that the hardness K value when compressed by 70% is 850 N / mm 2 or more and 1,500 N / mm 2 or less.

[0013] By the curing step, the solder particles cured so that the hardness K value when compressed by 70% is 850 N / mm 2 or more and 1,500 N / mm 2 or less can reduce the deformation of the solder particles due to the impact when the solder particles collide with the sieve surface during classification by a swirling air current type sieving machine, so that it is possible to prevent clogging of the sieve caused by the deformed solder particles adhering to the sieve surface and increase the yield. If the hardness K value when compressed by 70% is less than 850 N / mm 2 , the yield will decrease and the yield will be low due to the adhesion of the solder particles deformed on the sieve surface. On the other hand, if the hardness K value when compressed by 70% exceeds 1,500 N / mm 2 , the yield will increase, but an increase in the initial conduction resistance due to an increase in the oxide film will occur. In the aforementioned hardening process, the hardness K value at 70% compression deformation is 850 N / mm². 2 It is preferable to cure solder particles that are less than . That is, before curing, the hardness K value at 70% compression deformation is 850 N / mm 2 Soft solder particles, which are less than 100%, reach a hardness K value of 850 N / mm² when compressed by 70% due to hardening. 2 More than 1,500N / mm 2 As described below, this prevents solder particles from adhering to the sieve surface during classification using a swirling airflow type sieve classifier.

[0014] The hardness K value at 70% compression deformation can be determined by performing a micro-compression test as follows.

[0015] [Microcompression test] The degree of hardening of solder particles is measured using a micro-compression tester (MCT-211, manufactured by Shimadzu Corporation). The 70% K value, which is the hardness of solder particles at 70% compression deformation, can be calculated using the following formula (1).

[0016]

number

[0017] In the curing process, it is preferable to heat the material in an oxygen-containing atmosphere at a temperature below (the melting point of the solder particles - 15°C). Specifically, this involves using an air-circulating oven and heating and oxidizing the material in air at a temperature of 80°C to 130°C for 1 to 10 days. The curing is carried out under an oxygen-containing atmosphere. The oxygen concentration in the oxygen-containing atmosphere is preferably 15 vol% or higher, and more preferably 20 vol% or higher. When the oxygen concentration is 15 vol% or higher, a strong oxide film can be formed on the surface of the solder particles. Air can be used as the oxygen-containing atmosphere with an oxygen concentration of 21 vol%. In addition to the heat oxidation described above, solder particles can also be hardened by pressurized oxidation, humidified oxidation, or chemical treatment.

[0018] <Classification process> The classification process involves forcibly generating an airflow using a classification device to classify the hardened solder particles.

[0019] As the classification device, a device that forcibly generates an airflow to disperse particles and classify them while roughening the particle surface can be used, and a swirling airflow type sieve classifier that generates an airflow by blower suction to swirl solder particles and cause them to collide with the sieve surface for classification is preferable. According to this classification device, the solder particles are classified while their surface is roughened by collisions with the sieve surface. Examples of such classification devices include the spin air sieve (manufactured by Seishin Corporation), which is a swirling airflow type sieve classifier. The blower suction pressure is preferably 0.1 MPa or more and 1.5 MPa or less, and more preferably 0.5 MPa or more and 1.0 MPa or less.

[0020] The classification is preferably carried out in an oxygen-containing atmosphere. The oxygen concentration in the oxygen-containing atmosphere is preferably 15 vol% or higher, and more preferably 20 vol% or higher. When the oxygen concentration is 15 vol% or higher, a strong oxide film can be formed on the surface of the solder particles even during classification. Air can be used as the oxygen-containing atmosphere with an oxygen concentration of 21 vol%.

[0021] <Other processes> The aforementioned other processes are not particularly limited and can be appropriately selected depending on the purpose, and examples include washing and drying processes.

[0022] (Solder particles) The solder particles of this invention have a hardness K value of 850 N / mm² at 70% compression deformation. 2 More than 1,500N / mm 2 The following applies: 900 N / mm 2 More than 1,500N / mm2 The following is preferred: 950 N / mm 2 More than 1,300N / mm 2 The following are preferable. The hardness K value at 70% compression deformation can be determined by performing a micro-compression test, as described above.

[0023] In this invention, the hardness K value of the solder particles at 70% compression deformation is 850 N / mm². 2 More than 1,500N / mm 2 As described below, when classifying solder particles using a swirling airflow type sieving machine, deformation caused by the impact of the solder particles colliding with the sieve surface can be reduced, clogging caused by deformed solder particles adhering to the sieve surface can be prevented, and by classifying solder particles using a swirling airflow type sieving machine, coarse solder particles contained in commercially available solder particles can be removed, thus avoiding the risk of short circuits between wiring patterns caused by coarse solder particles.

[0024] Examples of the aforementioned solder particles include Sn-Pb solder particles, Pb-Sn-Sb solder particles, Sn-Sb solder particles, Sn-Pb-Bi solder particles, Sn-Bi solder particles, Sn-Bi-Ag solder particles, Sn-Bi-Cu solder particles, Sn-Cu solder particles, Sn-Pb-Cu solder particles, Sn-In solder particles, Sn-Ag solder particles, Sn-Pb-Ag solder particles, Pb-Ag solder particles, and Sn-Ag-Cu solder particles, as specified in JIS Z3282-1999. These may be used individually or in combination of two or more types. Among these, solder particles containing Sn and at least one selected from Bi, Ag, Cu, and In are preferred, and Sn-Bi-based solder particles, Sn-Bi-Ag-based solder particles, Sn-Bi-Cu-based solder particles, and Sn-In-based solder particles are more preferred. The melting point of the solder particles is preferably 110°C to 240°C, and more preferably 120°C to 200°C.

[0025] The number-average particle size of the solder particles is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, and particularly preferably 15 μm or more. The upper limit of the number-average particle size of the solder particles is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less. The number-average particle size of the aforementioned solder particles can be determined, for example, by measuring approximately 10,000 particles using a dry imaging particle size analyzer (Morphologi G3, manufactured by Malvern), and the particle size distribution can be expressed as number frequency. The proportion of coarse solder particles having a number particle size 1.25 times or larger than the number average particle size in the aforementioned solder particles is preferably 0.5% or less, more preferably 0.1% or less, even more preferably 0.05% or less, particularly preferably 0.01% or less, and most preferably 0%. If the proportion of coarse solder particles having a number-average particle size 1.25 times or larger than the number-average particle size of the solder particles is 0.5% or less, it is possible to avoid short circuits between wiring patterns caused by coarse solder particles.

[0026] (Conductive composition) The conductive composition of the present invention preferably contains the solder particles of the present invention, a binder, a monofunctional polymerizable monomer, an elastomer, a curing agent, and a silane coupling agent, and may further contain other components as needed.

[0027] The conductive composition may be either a conductive film or a conductive paste. A conductive film is preferred in terms of ease of handling, while a conductive paste is preferred in terms of cost. If the conductive composition is a conductive film, a film that does not contain solder particles may be laminated onto the conductive film containing solder particles.

[0028] -Solder particles- As the solder particles, the solder particles of the present invention described above are used. There are no particular restrictions on the content of the solder particles in the conductive composition, and it can be appropriately adjusted depending on the wiring pitch and connection area of ​​the connection structure.

[0029] -binder- The binder is not particularly limited and can be appropriately selected depending on the purpose. Examples include phenoxy resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, urethane resin, butadiene resin, polyimide resin, polyamide resin, and polyolefin resin. These may be used individually or in combination of two or more. Among these, phenoxy resin is particularly preferred in terms of film-forming properties, processability, and connection reliability. The phenoxy resin mentioned above is a resin synthesized from bisphenol A and epichlorohydrin, and may be synthesized as appropriate or a commercially available product may be used. Examples of such commercially available products include the trade names: YP-50 (manufactured by Toto Kasei Co., Ltd.), YP-70 (manufactured by Toto Kasei Co., Ltd.), and EP1256 (manufactured by Japan Epoxy Resin Co., Ltd.). There are no particular restrictions on the content of the binder in the conductive composition, and it can be appropriately selected depending on the purpose, but for example, 20% to 70% by mass is preferred, and 35% to 55% by mass is more preferred.

[0030] -Monofunctional polymerizable monomers- The monofunctional polymerizable monomer is not particularly limited as long as it has one polymerizable group in its molecule, and can be appropriately selected depending on the purpose. Examples include monofunctional (meth)acrylic monomers, styrene monomers, butadiene monomers, and other olefin monomers having double bonds. These may be used individually or in combination of two or more. Among these, monofunctional (meth)acrylic monomers are particularly preferred in terms of adhesive strength and connection reliability. The monofunctional (meth)acrylic monomer is not particularly limited and can be appropriately selected depending on the purpose. Examples include acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, n-dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, and other acrylic acids or their esters; methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, n-dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and other methacrylic acids or their esters. These may be used individually or in combination of two or more.

[0031] The content of the monofunctional polymerizable monomer in the conductive composition is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 2% to 30% by mass, and more preferably 5% to 20% by mass.

[0032] -Hardening agent- The curing agent is not particularly limited as long as it can cure the binder, and can be appropriately selected depending on the purpose, but organic peroxides are preferred, for example. Examples of the aforementioned organic peroxides include lauroyl peroxide, butyl peroxide, benzyl peroxide, dilauroyl peroxide, dibutyl peroxide, benzyl peroxide, peroxydicarbonate, and benzoyl peroxide. These may be used individually or in combination of two or more. The content of the curing agent in the conductive composition is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 1% by mass or more and 15% by mass or less, and more preferably 3% by mass or more and 10% by mass or less.

[0033] -Elastomer- There are no particular restrictions on the elastomer used; it can be appropriately selected depending on the purpose. Examples include polyurethane elastomers, acrylic rubber, silicone rubber, and butadiene rubber. These may be used individually or in combination of two or more types.

[0034] -Silane coupling agent- There are no particular restrictions on the silane coupling agent, and it can be appropriately selected depending on the purpose. Examples include epoxy-based silane coupling agents, acrylic-based silane coupling agents, thiol-based silane coupling agents, and amine-based silane coupling agents. The content of the silane coupling agent in the conductive composition is not particularly limited and can be appropriately selected depending on the purpose, but it is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 5% by mass or less.

[0035] -Other ingredients- The aforementioned other components are not particularly limited and can be appropriately selected depending on the purpose. Examples include organic solvents, fillers, softeners, accelerators, antioxidants, colorants (pigments, dyes), and ion catchers. The amount of these other components added is not particularly limited and can be appropriately selected depending on the purpose.

[0036] <Application> The solder particles and conductive composition of the present invention can avoid the risk of short circuits and can therefore be used to electrically connect electrodes of various connection targets, such as connecting a flexible printed circuit board to a glass substrate (FOG (Film on Glass)), connecting a semiconductor chip to a flexible printed circuit board (COF (Chip on Film)), connecting a semiconductor chip to a glass substrate (COG (Chip on Glass)), and connecting a flexible printed circuit board to a glass epoxy substrate (FOB (Film on Board)). [Examples]

[0037] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments at all. In the following examples and comparative examples, the "hardness K value at 70% compression deformation (70% K value)", "particle size distribution", "SEM observation of the surface of solder particles", "measurement of the endothermic peak of solder particles by DSC", "ratio of sieve clogging after classification", and "yield" were measured and evaluated as follows.

[0038] <Measurement of hardness K value at 70% compression deformation (70% K value)> Using a micro compression tester (MCT-211, manufactured by Shimadzu Corporation), the degree of curing of the solder particles was measured. The hardness K value (70% K value) of the solder particles at 70% compression deformation was calculated by the following formula (1).

[0039]

Equation

[0040] <Measurement of particle size distribution> Using a dry imaging type particle size distribution analyzer (Morphologi G3, manufactured by Malvern), about 10,000 particles were measured, and the particle size distribution was expressed as the number frequency.

[0041] <Measurement of the endothermic peak of solder particles by DSC> The endothermic peak of the solder particles by DSC was measured using a differential scanning calorimeter (DSC) (EXSTAR DSC6200, manufactured by Seiko Instruments Inc.).

[0042] <SEM observation of the surface of solder particles> The SEM observation of the surface of the solder particles was performed using a scanning electron microscope (SEM) (JSM-6510A, manufactured by JEOL Ltd.).

[0043] <Ratio of sieve clogging after classification> The sieves after classification were observed under a microscope (SZX16, manufactured by Olympus Corporation, magnification ×11.5), and the number of clogged sieve openings X out of 500 sieve openings was measured. The percentage of clogged sieve openings (%) was calculated from X / 500 and evaluated according to the following criteria. [Evaluation Criteria] ○: Sieve clogging rate is less than 60% △: Sieve clogging rate is 60% or more but less than 80% ×: Sieve clogging rate is 80% or higher

[0044] <Yield> The yield (%) was calculated using the following formula: Yield (%) = (B / A) × 100, based on the amount of solder particles A (g) fed into the classification apparatus and the amount of classified solder particles B (g) recovered after classification. The yield was then evaluated according to the following criteria. [Evaluation Criteria] ○: Yield of 30% or more △: Yield is between 20% and 30% ×: Yield is 20% or less

[0045] (Example 1) <Solder particles> As solder particles Sn 59.9 Bi 40 Cu 0.1 -Type5 (Manufactured by Mitsui Mining & Smelting Co., Ltd.) was prepared. Sn 59.9 Bi 40 Cu 0.1 -Type5 The results of measuring the particle size distribution using a dry imaging particle size analyzer (Morphologi G3, Malvern) showed a particle size distribution of 15 μm to 25 μm, with a cumulative 50% particle size (D 50 The proportion of coarse solder particles with a diameter of 20 μm or more and a particle size of 25 μm or more was 7%.

[0046] <Hardening of solder particles> Solder particles scattered on an aluminum tray were placed in an air-circulating oven set to 100°C and left to stand for 4 days to heat-cur. The hardened solder particles were subjected to a micro-compression test, and the hardness K value (70%K value) at 70% compression deformation was determined to be 950 N / mm². 2 That was the case.

[0047] <Classification of solder particles> A twill weave wire mesh sieve (manufactured by Tokyo Screen Co., Ltd.) with a diameter of φ200 mm and a mesh opening of 20 μm was set in a spin air sieve (manufactured by Seishin Corporation), a type of swirling airflow sieving machine, and a suction pressure of 0.75 MPa was applied using a blower. Next, 50 g of solder particles were fed in through the raw material supply port. The machine was operated in air for 5 minutes from raw material input until the classification was complete, and 15 g of classified solder particles were obtained by collecting the fine powder particles that passed through the sieve (yield: 30%). The sieves after classification were observed under a microscope, and the percentage of sieve clogging was determined to be 40%. The hardness K value (70%K value) at 70% compression deformation after classification was measured and found to be 960 N / mm². 2 That was the case. The obtained classified solder particles were measured using a dry imaging particle size analyzer (Morphologi G3, Malvern), and the proportion of coarse solder particles with a particle size of 25 μm or larger was found to be 0.02%. The surface of the obtained classified solder particles was observed to be uneven from scanning electron microscopy (SEM) observation. The endothermic peak of the classified solder particles measured by differential scanning calorimeter (DSC) was 141°C, and SEM observation of the classified solder particles after DSC measurement showed that there was almost no aggregation of particles due to particle melting compared to the unclassified solder particles.

[0048] <Fabrication of conductive films> Five parts by mass of the solder particles prepared in Example 1 and 95 parts by mass of the insulating binder described below were placed in a planetary stirring device and stirred for 1 minute to prepare a conductive composition. Next, the conductive composition was applied to a 50 μm thick PET film and dried in an 80°C oven for 5 minutes to form a 25 μm thick adhesive layer made of the conductive composition on the PET film, thereby producing a conductive film with a width of 2.0 mm.

[0049] -Insulating Binder- The insulating binder was a mixed solution of ethyl acetate and toluene containing 47 parts by mass of phenoxy resin (product name: YP-50, manufactured by Shin-Nippon Chemical Epoxy Manufacturing Co., Ltd.), 3 parts by mass of monofunctional monomer (product name: M-5300, manufactured by Toagosei Co., Ltd.), 25 parts by mass of urethane resin (product name: UR-1400, manufactured by Toyobo Industries Ltd.), 15 parts by mass of rubber component (product name: SG80H, manufactured by Nagase ChemteX Corporation), 2 parts by mass of silane coupling agent (product name: A-187, manufactured by Momentive Performance Materials Japan Inc.), and 3 parts by mass of organic peroxide (product name: Niper BW, manufactured by NOF Corporation), with a solid content of 50% by mass.

[0050] <Fabrication of connecting structures> A connecting structure was fabricated by thermocompression bonding an evaluation substrate (glass epoxy substrate (FR4), 200 μm pitch, line:space = 1:1, terminal thickness 10 μm, Cu (undercoat) / Ni / Au plating) and an FPC (polyimide film, 200 μm pitch, line:space = 1:1, terminal thickness 12 μm, Cu (undercoat) / Ni / Au plating) via the above conductive film. The thermocompression bonding was performed by pressing a tool down through a 200 μm thick silicone rubber on the FPC under the following conditions: temperature: 150°C, pressure: 2 MPa, time: 20 sec.

[0051] <Evaluation of conductivity characteristics> The fabricated connection structure was measured using a digital multimeter (manufactured by Yokogawa Electric Corporation) with a 4-terminal method to determine its initial conduction resistance when a current of 1 mA was applied. It was then evaluated according to the following criteria. Furthermore, a voltage was applied between the patterns of the connection structure, and the initial insulation resistance was measured to check for short circuits. Note that the initial insulation resistance was 1 × 10⁻⁶. 5 Values ​​below Ω were evaluated as unacceptable due to the occurrence of a short circuit. [Evaluation Criteria] ○: When the conductivity resistance is 1Ω or less △: When the conductivity resistance exceeds 1Ω ×: The conductive resistor is open.

[0052] (Example 2) <Hardening of solder particles> In Example 1, the solder particles were cured in the same manner as in Example 1, except that the solder particles scattered on an aluminum tray were placed in an air-circulating oven set to 100°C and left to stand for two days. The hardened solder particles were subjected to a micro-compression test, and the hardness value at 70% compression deformation (70%K value) was determined to be 850 N / mm². 2 That was the case.

[0053] <Classification of solder particles> The hardened solder particles were subjected to forced-air classification in the same manner as in Example 1, and 12.5 g of the classified solder particles for Example 2 were obtained (yield: 25%). The sieves after classification were observed under a microscope, and the percentage of clogged sieves was found to be 65%. The hardness K value (70%K value) at 70% compression deformation after classification was measured and found to be 860 N / mm². 2 That was the case. The obtained classified solder particles were measured using a dry imaging particle size analyzer (Morphologi G3, Malvern), and the proportion of coarse solder particles with a particle size of 25 μm or larger was found to be 0.01%. The surface of the obtained classified solder particles was observed to be uneven from scanning electron microscopy (SEM) observation. The endothermic peak of the classified solder particles measured by differential scanning calorimeter (DSC) was 141°C, and SEM observation of the classified solder particles after DSC measurement showed that there was almost no aggregation of particles due to particle melting compared to the unclassified solder particles.

[0054] <Fabrication of conductive films, fabrication of connecting structures, and evaluation> Using the solder particles produced in Example 2, a conductive film and a connecting structure were fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0055] (Example 3) <Hardening of solder particles> In Example 1, the solder particles were cured in the same manner as in Example 1, except that the solder particles scattered on an aluminum tray were placed in an air-circulating oven set to 100°C and left to stand for 10 days. The hardened solder particles were subjected to a micro-compression test, and the hardness K value (70%K value) at 70% compression deformation was determined to be 1,500 N / mm². 2 That was the case.

[0056] <Classification of solder particles> The hardened solder particles were subjected to forced-air classification in the same manner as in Example 1, and 20 g of the classified solder particles for Example 3 were obtained (yield: 40%). The sieves after classification were observed under a microscope, and the percentage of clogged sieves was found to be 30%. The hardness K value (70%K value) at 70% compressive deformation after classification was measured and found to be 1,500 N / mm². 2 That was the case. The obtained classified solder particles were measured using a dry imaging particle size analyzer (Morphologi G3, Malvern), and the proportion of coarse solder particles with a particle size of 25 μm or larger was found to be 0.01%. The surface of the obtained classified solder particles was observed to be uneven from scanning electron microscopy (SEM) observation. The endothermic peak of the classified solder particles measured by differential scanning calorimeter (DSC) was 141°C, and SEM observation of the classified solder particles after DSC measurement showed that there was almost no aggregation of particles due to particle melting compared to the unclassified solder particles.

[0057] <Fabrication of conductive films, fabrication of connecting structures, and evaluation> Using the solder particles produced in Example 3, a conductive film and a connecting structure were fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0058] (Example 4) <Classification of solder particles> Using solder particles that had undergone the same curing treatment as in Example 1, and with the suction pressure in the classification conditions changed to 0.5 MPa, forced airflow classification was performed in the same manner as in Example 1, and 12.5 g of solder particles for Example 4 were obtained (yield: 25%). The sieves after classification were observed under a microscope, and the percentage of clogged sieves was found to be 30%. The hardness K value (70%K value) at 70% compression deformation after classification was measured to be 955 N / mm². 2 That was the case. The obtained classified solder particles were measured using a dry imaging particle size analyzer (Morphologi G3, Malvern), and the percentage of coarse solder particles with a particle size of 25 μm or larger was found to be 0%. The surface of the obtained classified solder particles was observed to be uneven from scanning electron microscopy (SEM) observation. The endothermic peak of the classified solder particles measured by differential scanning calorimeter (DSC) was 141°C, and SEM observation of the classified solder particles after DSC measurement showed that there was almost no aggregation of particles due to particle melting compared to the unclassified solder particles.

[0059] <Fabrication of conductive films, fabrication of connecting structures, and evaluation> Using the solder particles produced in Example 4, a conductive film and a connecting structure were fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0060] (Example 5) <Classification of solder particles> Using solder particles that had undergone the same curing treatment as in Example 1, and with the suction pressure in the classification conditions changed to 1 MPa, forced airflow classification was performed in the same manner as in Example 1, and 12.5 g of solder particles for Example 5 was obtained (yield: 25%). The sieves after classification were observed under a microscope, and the percentage of clogged sieves was found to be 70%. The hardness K value (70%K value) at 70% compression deformation after classification was measured and found to be 970 N / mm². 2 That was the case. The obtained classified solder particles were measured using a dry imaging particle size analyzer (Morphologi G3, Malvern), and the proportion of coarse solder particles with a particle size of 25 μm or larger was found to be 0.05%. The surface of the obtained classified solder particles was observed to be uneven from scanning electron microscopy (SEM) observation. The endothermic peak of the classified solder particles measured by differential scanning calorimeter (DSC) was 141°C, and SEM observation of the classified solder particles after DSC measurement showed that there was almost no aggregation of particles due to particle melting compared to the unclassified solder particles.

[0061] <Fabrication of conductive films, fabrication of connecting structures, and evaluation> Using the solder particles produced in Example 5, a conductive film and a connecting structure were fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0062] (Example 6) <Solder particles> Sn as solder particles 42 Bi 58 -Type 5 (manufactured by Mitsui Mining & Smelting Co., Ltd.) was prepared. Sn 42 Bi 58 -Type 5 was measured using a dry imaging particle size analyzer (Morphologi G3, Malvern), and the results showed a particle size distribution of 15 μm to 25 μm, with a cumulative 50% particle size (D 50 The proportion of coarse solder particles with a diameter of 20 μm or more and a particle size of 25 μm or more was 5%.

[0063] <Hardening of solder particles> Solder particles scattered on an aluminum tray were placed in an air-circulating oven set to 100°C and left to stand for one day to heat-cur. The hardened solder particles were subjected to a micro-compression test, and the hardness K value (70%K value) at 70% compression deformation was determined to be 930 N / mm². 2 That was the case.

[0064] <Classification of solder particles> The hardened solder particles were subjected to forced-air classification in the same manner as in Example 1, and 17.5 g of the classified solder particles of Example 6 were obtained (yield: 35%). The sieves after classification were observed under a microscope, and the percentage of sieve clogging was determined to be 40%. The hardness K value (70%K value) at 70% compression deformation after classification was measured and found to be 940 N / mm². 2 That was the case. The obtained classified solder particles were measured using a dry imaging particle size analyzer (Morphologi G3, Malvern), and the proportion of coarse solder particles with a particle size of 25 μm or larger was found to be 0.01%. The surface of the obtained classified solder particles was observed to be uneven from scanning electron microscopy (SEM) observation. The endothermic peak of the classified solder particles measured by differential scanning calorimeter (DSC) was 141°C, and SEM observation of the classified solder particles after DSC measurement showed that there was almost no aggregation of particles due to particle melting compared to the unclassified solder particles.

[0065] <Fabrication of conductive films, fabrication of connecting structures, and evaluation> Using the solder particles produced in Example 6, a conductive film and a connecting structure were fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0066] (Comparative Example 1) <Hardening of solder particles> In Example 1, the solder particles were not cured. A micro-compression test was performed on these solder particles, and the hardness K value (70%K value) at 70% compression deformation was determined to be 800 N / mm². 2 That was the case.

[0067] <Classification of solder particles> The solder particles were subjected to forced-air classification in the same manner as in Example 1, and 10 g of classified solder particles for Comparative Example 1 were obtained (yield: 20%). The sieves after classification were observed under a microscope, and the percentage of clogged sieves was found to be 90%. The hardness K value (70%K value) at 70% compression deformation after classification was measured and found to be 810 N / mm². 2 That was the case. The obtained classified solder particles were measured using a dry imaging particle size analyzer (Morphologi G3, Malvern), and the proportion of coarse solder particles with a particle size of 25 μm or larger was found to be 0.01%. The surface of the obtained classified solder particles was observed to be uneven from scanning electron microscopy (SEM) observation. The endothermic peak of the classified solder particles measured by differential scanning calorimeter (DSC) was 141°C, and SEM observation of the classified solder particles after DSC measurement showed that there was almost no aggregation of particles due to particle melting compared to the unclassified solder particles.

[0068] <Fabrication of conductive films, fabrication of connecting structures, and evaluation> Using the solder particles from Comparative Example 1, a conductive film and a connecting structure were fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0069] (Comparative Example 2) <Hardening of solder particles> Comparative Example 2 solder particles were obtained in the same manner as in Example 1, except that solder particles that had undergone the same curing treatment as in Example 1 were used, and classification treatment was omitted.

[0070] <Fabrication of conductive films, fabrication of connecting structures, and evaluation> Using the solder particles from Comparative Example 2, a conductive film and a connecting structure were fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0071] (Comparative Example 3) <Hardening of solder particles> In Example 1, the solder particles were cured in the same manner as in Example 1, except that the solder particles scattered on an aluminum tray were placed in an air-circulating oven set to 100°C and left to stand for 15 days. The hardened solder particles were subjected to a micro-compression test, and the hardness K value (70%K value) at 70% compression deformation was determined to be 1,550 N / mm². 2 That was the case.

[0072] <Classification of solder particles> The hardened solder particles were subjected to forced-air classification in the same manner as in Example 1, and 20 g of classified solder particles for Comparative Example 3 were obtained (yield: 40%). The sieves after classification were observed under a microscope, and the percentage of clogged sieves was found to be 30%. The hardness K value (70%K value) at 70% compressive deformation after classification was measured to be 1,550 N / mm². 2 That was the case. The obtained classified solder particles were measured using a dry imaging particle size analyzer (Morphologi G3, Malvern), and the percentage of coarse solder particles with a particle size of 25 μm or larger was found to be 0%. The surface of the obtained classified solder particles was observed to be uneven from scanning electron microscopy (SEM) observation. The endothermic peak of the classified solder particles measured by differential scanning calorimeter (DSC) was 141°C, and SEM observation of the classified solder particles after DSC measurement showed that there was almost no aggregation of particles due to particle melting compared to the unclassified solder particles.

[0073] <Fabrication of conductive films, fabrication of connecting structures, and evaluation> Using the solder particles from Comparative Example 3, a conductive film and a connecting structure were fabricated and evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0074] [Table 1]

[0075] [Table 2]

[0076] [Table 3]

[0077] From the results in Tables 1 to 3, all of Examples 1 to 6 had a hardness K value (70%K value) of 850 N / mm² at 70% compression deformation. 2 More than 1,500N / mm 2 The following results were obtained, indicating that both initial conduction resistance and initial insulation resistance were of good quality. Furthermore, in Comparative Example 1, the yield was 20%, the sieve clogging rate was 90%, and it was confirmed that most of the sieves after classification were clogged with solder particles. In addition, while Comparative Example 2 showed good initial conductivity resistance, a short circuit occurred during the initial insulation resistance measurement. Upon observation of the channels where the short circuit occurred, areas were observed where deformed solder particles had melted and grown coarsely were present. Furthermore, Comparative Example 3 had a hardness K value (70%K value) of 1,500 N / mm² at 70% compression deformation. 2 Because it was larger than the given value, the yield increased, but the initial conductivity resistance increased due to the increase in the oxide film. [Industrial applicability]

[0078] The solder particles and conductive compositions obtained by the solder particle manufacturing method of the present invention can avoid the risk of short circuits and are therefore suitably used, for example, in flexible printed circuit boards (FPCs), connections between terminals of IC chips and ITO (Indium Tin Oxide) electrodes formed on the glass substrate of an LCD panel, connections between COF and PWB, connections between TCP and PWB, connections between COF and glass substrates, connections between COF and COF, connections between IC substrates and glass substrates, and connections between IC substrates and PWBs. [Explanation of Symbols]

[0079] 10 Wiring Patterns 11 Coarse solder particles 12 Solder particles 13 Sieve 14 sieve opening 15. Deformed solder particles 16 Solder particles repelled by the sieve

Claims

1. Solder particles comprising Sn and at least one selected from Bi, Ag, Cu, and In, having a hardness K value of 850 N / mm² when compressed by 70%. ２ 1,500N / mm or more ２ The curing process is as follows: This includes a classification step in which an airflow is forcibly generated by a classification device to classify the hardened solder particles, A method for manufacturing solder particles, characterized in that the classification apparatus is a device that generates an airflow by blower suction to cause solder particles to swirl and collide with the surface of a sieve for classification.

2. In the aforementioned hardening process, the hardness K value at 70% compression deformation is 850 N / mm². ２ A method for producing solder particles according to claim 1, wherein solder particles that are less than [a certain value] are cured.

3. A method for producing solder particles according to any one of claims 1 to 2, wherein in the curing step, the solder particles are heated in an oxygen-containing atmosphere at a temperature of (the melting point of the solder particles - 15°C) or lower.

4. A method for producing solder particles according to any one of claims 1 to 3, wherein the classification is carried out in an oxygen-containing atmosphere.

5. The hardness K value at 70% compression deformation is 850 N / mm². ２ 1,500N / mm or more ２ Solder particles that are as follows: It comprises Sn and at least one selected from Bi, Ag, Cu, and In, Solder particles characterized in that the proportion of coarse solder particles having a number particle size 1.25 times or more larger than the number-average particle size of the aforementioned solder particles is 0.5% or less.

6. Solder particles according to claim 5, wherein the number-average particle size is 1 μm or more.

7. A conductive composition characterized by containing solder particles according to any one of claims 5 to 6.

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