Conductive composition

Abstract

This conductive composition contains 2-8 parts by mass of flux relative to 100 parts by mass of metal particles. The metal particles (100 parts by mass) contain 42-50 parts by mass of metal particles (A) that are composed of SnBi alloy particles and Sn particles, and 25-58 parts by mass of metal particle (B) that are at least one kind of particles selected from the group consisting of copper particles, silver particles, and silver-coated copper particles, and contain at least copper and silver. The 10% cumulative value of the particle diameters of the SnBi alloy particles is 4-15 μm, and the 90% cumulative value of the particle diameters of the SnBi alloy particles is 8-25 μm. The 10% cumulative value of the particle diameters of the Sn particles is 7-30 μm, and the 90% cumulative value of the particle diameters of the Sn particles is 15-50 μm.

Description

conductive composition

[0001] The present invention relates to an electrically conductive composition.

[0002] As automobiles become more electronically equipped in preparation for the shift to EV / HEV and autonomous driving, the number of engine control units (ECUs) installed is increasing. This has led to increased demand for high-density packaging, and ECUs are becoming increasingly smaller.

[0003] In addition, with the increasing use of power devices that use high-voltage insulated gate bipolar transistors (IGBTs) in EVs and HEVs, there is a growing demand for high heat resistance and heat dissipation in mounting-related products. Furthermore, with the increasing performance and miniaturization of power devices in 5G base stations, there is also a growing demand for high heat dissipation.

[0004] In particular, for semiconductors with junction temperatures exceeding 175°C, there is a demand to switch to sintering paste as the adhesive used to connect the lead frame and die. However, because sintering paste does not contain resin, stress relaxation is difficult, and maintaining long-term bonding strength (long-term reliability) has been an issue.

[0005] Patent Document 1 discloses a functional material capable of forming high-quality, highly reliable wiring, etc., which contains at least two of first metal composite particles containing Cu, second metal composite particles containing Sn and Cu, and third metal composite particles containing Sn and Bi.

[0006] Patent Document 2 discloses a conductive composition including first metal particles containing Cu as a high-melting-point metal, second metal particles containing Sn as a low-melting-point metal and Bi as a carrier metal, third metal particles containing Sn, and an organic binder.

[0007] Patent Document 3 discloses an electromagnetic wave shielding composition containing Cu particles, Sn particles, SnBi particles, and a resin.

[0008] As described above, Patent Documents 1 to 3 describe the combination of multiple types of metal particles, but Patent Document 1 does not describe the particle diameters of those metal particles. Patent Document 2 describes that the particle diameters of the first to third metal particles preferably have diameters of approximately 1 to 20 μm. Patent Document 3 describes that the average particle diameter of Sn particles is 3 μm and the average particle diameter of SnBi particles is 3 μm. However, Patent Documents 2 and 3 do not describe the use of SnBi alloy particles and Sn particles having specific values ​​for the 10% cumulative value and 90% cumulative value of particle diameter.

[0009] Japanese Patent Application Laid-Open No. 2014-063725 Japanese Patent Application Laid-Open No. 2012-523091 Japanese Patent Application Laid-Open No. 2021-141119

[0010] The present invention has been made in view of the above, and an object of the present invention is to provide a conductive composition that has excellent conductivity, adhesion, and long-term reliability after curing.

[0011] The present invention includes the following embodiments. [1] A conductive composition containing 2 to 8 parts by mass of flux per 100 parts by mass of metal particles, wherein the 100 parts by mass of the metal particles include 42 to 50 parts by mass of metal particles (A) consisting of SnBi alloy particles and Sn particles, and 25 to 58 parts by mass of metal particles (B) that are at least one type selected from the group consisting of copper particles, silver particles, and silver-coated copper particles and contain at least copper and silver, wherein the SnBi alloy particles have a 10% cumulative particle diameter of 4 to 15 μm and a 90% cumulative particle diameter of 8 to 25 μm, and the Sn particles have a 10% cumulative particle diameter of 7 to 30 μm and a 90% cumulative particle diameter of 15 to 50 μm. [2] The conductive composition according to [1], wherein the metal particles (B) have an average particle diameter of 1 to 35 μm.

[0012] The conductive composition according to the present invention provides excellent conductivity, adhesion, and long-term reliability after curing.

[0013] Hereinafter, the embodiments of the present invention will be described in more detail.

[0014] The conductive composition according to this embodiment contains metal particles and a flux. The metal particles include metal particles (A) consisting of SnBi alloy particles and Sn particles, and metal particles (B) consisting of at least one type selected from the group consisting of copper particles, silver particles, and silver-coated copper particles, and containing at least copper and silver.

[0015] The metal particles (A) are a combination of SnBi alloy particles and Sn particles. These particles have a lower melting point than the metal particles (B), so the metal particles (A) can be said to be low-melting-point metal particles. According to this embodiment, by using Sn particles in combination with the SnBi alloy particles as the low-melting-point metal particles (A), rather than using SnBi alloy particles alone, the long-term reliability can be significantly improved.

[0016] Here, the melting point of Sn is 232°C. SnBi contains Bi, so its melting point is lower than that of Sn. Therefore, the melting point of the SnBi alloy particles is preferably less than 232°C, for example, 138°C to 200°C. The melting point is the temperature at which a solid phase and a liquid phase coexist under 1 atmosphere, and can be determined from a phase diagram.

[0017] The SnBi alloy particles may be particles made of a lead-free solder alloy having a basic composition of tin (Sn) and bismuth (Bi). The SnBi alloy particles may further contain other metals such as zinc (Zn) and silver (Ag), as long as they have a basic composition of Sn and Bi.

[0018] The tin (Sn) content in the SnBi alloy particles is not particularly limited, but is preferably 20 to 90 mass%, more preferably 40 to 80 mass%, and even more preferably 60 to 80 mass%. The bismuth (Bi) content in the SnBi alloy particles is not particularly limited, but is preferably 10 to 80 mass%, more preferably 20 to 60 mass%, and even more preferably 20 to 40 mass%. The total content of Sn and Bi in the SnBi alloy particles is preferably 80 mass% or more, and more preferably 99 mass% or more.

[0019] The Sn particles are particles made of tin (Sn) and are basically composed of only Sn, but may contain other components as impurities. The Sn content in the Sn particles is preferably 98% by mass or more, and more preferably 99% by mass or more.

[0020] The content of metal particles (A) per 100 parts by mass of metal particles is 42 to 50 parts by mass, more preferably 45 to 50 parts by mass. Here, the content of metal particles (A) is the sum of the content of SnBi alloy particles and the content of Sn particles. When the content of metal particles (A) is 42 parts by mass or more, excellent electrical conductivity and long-term reliability are likely to be obtained, and when it is 50 parts by mass or less, excellent high-temperature adhesion and long-term reliability are likely to be obtained.

[0021] The compounding ratio of the SnBi alloy particles to the Sn particles is not particularly limited, but from the viewpoint of enhancing the effects of this embodiment, it is preferably set as follows: In 100% by mass of the metal particles (A), the content of the SnBi alloy particles is preferably 50 to 90% by mass, more preferably 60 to 85% by mass, and even more preferably 70 to 80% by mass. The content of the Sn particles is preferably 10 to 50% by mass, more preferably 15 to 40% by mass, and even more preferably 20 to 30% by mass.

[0022] In one embodiment, the content of the SnBi alloy particles per 100 parts by mass of the metal particles is preferably 20 to 45 parts by mass, more preferably 25 to 42 parts by mass, and even more preferably 30 to 40 parts by mass. The content of the Sn particles per 100 parts by mass of the metal particles is preferably 2 to 25 parts by mass, more preferably 5 to 20 parts by mass, and even more preferably 8 to 15 parts by mass.

[0023] The particle diameter of the SnBi alloy particles is such that the 10% cumulative value (D10) is 4 to 15 μm and the 90% cumulative value (D90) of the particle diameter is 8 to 25 μm. When the D10 and D90 of the SnBi alloy particles are equal to or greater than the lower limit values, excellent conductivity, adhesion, and long-term reliability are likely to be obtained. Furthermore, when the D10 and D90 are equal to or less than the upper limit values, excellent adhesion and excellent long-term reliability under more severe conditions are likely to be obtained. The particle diameter of the SnBi alloy particles is more preferably such that the D10 is 5 to 12 μm and the D90 is 10 to 20 μm, and even more preferably such that the D10 is 5 to 10 μm and the D90 is 10 to 15 μm.

[0024] The particle diameter of the Sn particles is such that the 10% cumulative value (D10) is 7 to 30 μm and the 90% cumulative value (D90) of the particle diameter is 15 to 50 μm. By setting the D10 and D90 of the Sn particles within these ranges, excellent conductivity is easily obtained, and by setting the D10 and D90 to the lower limit or above, excellent adhesion is easily obtained. By setting the D90 of the Sn particles to the upper limit or below, it is easy to suppress an increase in the thickness of the joint and an increase in thermal resistance (i.e., a decrease in the heat dissipation effect). The particle diameter of the Sn particles is more preferably D10 to 25 μm and D90 to 20 to 45 μm, and even more preferably D10 to 22 μm and D90 to 25 to 42 μm.

[0025] In one embodiment, the particle size of the Sn particles is preferably larger than that of the SnBi alloy particles, i.e., the 10% cumulative value of the particle size of the Sn particles is preferably larger than that of the SnBi alloy particles, and the 90% cumulative value of the particle size of the Sn particles is preferably larger than that of the SnBi alloy particles.

[0026] In this specification, the 10% cumulative value (D10) and the 90% cumulative value (D90) are values ​​corresponding to 10% and 90% cumulative, respectively, of particle diameters measured by a laser diffraction / scattering method, where the volume-based cumulative frequency is set to 100%.

[0027] The metal particles (B) are at least one selected from the group consisting of copper particles, silver particles, and silver-coated copper particles, and contain at least copper and silver. That is, the metal particles (B) may be silver-coated copper particles alone, or may be a combination of copper particles and silver particles, or a combination of copper particles and silver-coated copper particles, or a combination of silver particles and silver-coated copper particles, or a combination of copper particles, silver particles, and silver-coated copper particles. These particles have a higher melting point than the metal particles (A), so the metal particles (B) can be said to be high-melting-point metal particles.

[0028] The silver-coated copper particles are not particularly limited as long as they have copper particles and a silver coating layer that coats at least a portion of the copper particles. The silver content of the silver-coated copper particles is not particularly limited, but is preferably 5 to 25% by mass, and more preferably 5 to 20% by mass.

[0029] The content of the metal particles (B) per 100 parts by mass of the metal particles is 25 to 58 parts by mass, more preferably 30 to 57 parts by mass, even more preferably 40 to 56 parts by mass, and even more preferably 45 to 55 parts by mass. When the content of the metal particles (B) is 25 parts by mass or more, excellent long-term reliability is likely to be obtained, and when it is 58 parts by mass or less, excellent conductivity and long-term reliability are likely to be obtained.

[0030] The copper content in 100% by mass of metal particles (B) is preferably 1 to 99% by mass, more preferably 10 to 80% by mass, even more preferably 20 to 60% by mass, and even more preferably 30 to 50% by mass. The silver content in 100% by mass of metal particles (B) is preferably 1 to 99% by mass, more preferably 20 to 90% by mass, even more preferably 40 to 80% by mass, and even more preferably 50 to 70% by mass. When the copper and silver contents are within the above ranges, excellent conductivity and long-term reliability are likely to be obtained. The total copper and silver content in 100% by mass of metal particles (B) is preferably 90% by mass or more, more preferably 99% by mass or more.

[0031] The shape of the metal particles (B) is not particularly limited, and spherical, flake-like (scale-like), dendritic, or fibrous particles can be used. The term "spherical" metal particles includes not only nearly spherical particles (atomized powder) but also nearly spherical particles such as nearly polyhedral spheres (reduced powder) and irregularly shaped particles (electrolytic powder). The term "dendritic" refers to a shape having one or more dendrites protruding from the particle surface. The dendrites may be unbranched main branches, or may have a shape in which branch portions branch off from the main branches and grow planarly or three-dimensionally.

[0032] The average particle size of the metal particles (B) is preferably 1 to 35 μm. When the average particle size of the metal particles (B) is 1 μm or more, oxidation is resistant and alloying easily proceeds. Furthermore, the dispersibility of the metal particles (B) is improved, making it easy to prevent aggregation. When the average particle size of the metal particles (B) is 35 μm or less, it is easy to prevent an increase in the thickness of the joint and an increase in thermal resistance (i.e., a decrease in the heat dissipation effect). The average particle size of the metal particles (B) is more preferably 1 to 30 μm, and even more preferably 2 to 20 μm. Here, when the metal particles (B) are a mixture of two or more types of particles, the average particle size of the metal particles (B) means the average particle size of each metal particle.

[0033] The average particle size of the copper particles is preferably 3 to 35 μm, more preferably 5 to 30 μm. The average particle size of the silver particles is preferably 1 to 15 μm, more preferably 1 to 10 μm. The average particle size of the silver-coated copper particles is preferably 2 to 35 μm, more preferably 5 to 30 μm.

[0034] In this specification, the “average particle size” of the metal particles (B) refers to a value corresponding to 50% cumulative volume-based cumulative frequency of 100% in particle diameters measured by a laser diffraction / scattering method, and refers to D50 (median diameter).

[0035] The metal particles may contain metal particles other than the metal particles (A) and the metal particles (B) within a range that does not impair the effects of the present invention. Examples of such metal particles include indium (In) particles and zinc (Zn) particles.

[0036] The flux is not particularly limited, but examples thereof include amines, alcohols, rosin, organic acids, etc., and any one of these may be used alone or in combination of two or more.

[0037] Examples of amines that can be used include aliphatic amines, aromatic amines, and alkanolamines. Examples of aliphatic amines that can be used include dimethylamine, ethylamine, 1-aminopropane, isopropylamine, trimethylamine, allylamine, n-butylamine, diethylamine, sec-butylamine, tert-butylamine, N,N-dimethylethylamine, isobutylamine, and cyclohexylamine. Examples of aromatic amines that can be used include aniline, N-methylaniline, diphenylamine, N-isopropylaniline, and p-isopropylaniline. Examples of alkanolamines that can be used include 2-aminoethanol, 2-(ethylamino)ethanol, diethanolamine, diisopropanolamine, triethanolamine, N-butyldiethanolamine, triisopropanolamine, N,N-bis(2-hydroxyethyl)-N-cyclohexylamine, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, and N,N,N',N'',N''-pentakis(2-hydroxypropyl)diethylenetriamine. These amines can be used alone or in combination of two or more.

[0038] Examples of alcohols that can be used include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, sec-butanol, tert-butanol, 1-pentanol, 2-pentanol, sec-pentanol, tert-pentanol, 3-pentanol, 1-hexanol, 1-heptanol, and 1-octanol. These alcohols can be used alone or in combination of two or more. As the alcohol, it is preferable to use a linear alcohol having four or less carbon atoms.

[0039] Examples of rosins include acid-modified rosin, purified rosin, hydrogenated rosin, disproportionated rosin, rosin ester, and polymerized rosin, and these can be used alone or in combination of two or more. Rosin is a non-volatile component contained in pine resin and the like of pine plants. Examples of rosins include tall rosin, gum rosin, and wood rosin. Acid-modified rosin is rosin that has been treated with acid. Acid-modified rosin may be hydrogenated. Examples of acid-modified rosins include acrylic acid-modified rosin, acrylic acid-modified hydrogenated rosin, maleic acid-modified rosin, and maleic acid-modified hydrogenated rosin.

[0040] As the organic acid, a compound having two or more carboxy groups in the molecule can be used. Examples of such compounds include dicarboxylic acids such as aliphatic dicarboxylic acids such as oxalic acid, glutaric acid, adipic acid, succinic acid, sebacic acid, malonic acid, maleic acid, fumaric acid, pimelic acid, suberic acid, azelaic acid, citraconic acid, and dodecanedioic acid; aromatic dicarboxylic acids such as phthalic acid and terephthalic acid; α-ketoglutaric acid, diglycolic acid, thiodiglycolic acid, dithiodiglycolic acid, 4-cyclohexene-1,2-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, tetrahydrophthalic acid, and hexahydrophthalic acid. Examples of tricarboxylic acids include trimellitic acid, citric acid, isocitric acid, butane-1,2,4-tricarboxylic acid, cyclohexane-1,2,4-tricarboxylic acid, benzene-1,2,4-tricarboxylic acid, and 1,2,3-propanetricarboxylic acid. Examples of tetracarboxylic acids include ethylenetetracarboxylic acid, 1,2,3,4-butanetetracarboxylic acid, cyclobutane-1,2,3,4-tetracarboxylic acid, benzene-1,2,4,5-tetracarboxylic acid, etc. These organic acids can be used alone or in combination of two or more.

[0041] Among these, it is preferable to use at least one selected from the group consisting of alkanolamine, rosin, and dicarboxylic acid as the flux, as this blending method tends to provide excellent adhesion and long-term reliability.

[0042] The content of the flux is 2 to 8 parts by mass, and preferably 2.5 to 7 parts by mass, relative to 100 parts by mass of the metal particles. When the content of the flux is 2 parts by mass or more, excellent conductivity and adhesion are likely to be obtained, and when it is 8 parts by mass or less, excellent adhesion is likely to be obtained.

[0043] In the conductive composition according to this embodiment, the total content of the metal particles (A), the metal particles (B), and the flux is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0044] The conductive composition according to this embodiment may further contain a solvent. Examples of the solvent include glycol ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol dimethyl ether; alcohols such as terpineol, 2,2,4-trimethylpentane-1,3-diol monoisobutyrate, dihydroterpineol, terpineol, and benzyl alcohol; and γ-butyrolactone. These may be used alone or in combination of two or more.

[0045] The content of the solvent is not particularly limited, but is preferably 1 to 10 parts by mass, and more preferably 2 to 8 parts by mass, per 100 parts by mass of the metal particles.

[0046] The conductive composition according to this embodiment can be obtained by blending and thoroughly mixing the above-described components in predetermined amounts.

[0047] The conductive composition according to the present embodiment may contain additives that have been conventionally added to conductive compositions of the same type, provided that the additives do not depart from the object of the present invention. Examples of such additives include thickeners, tackifiers, anti-settling agents, colorants, and flame retardants.

[0048] The viscosity of the conductive composition according to this embodiment may be adjusted appropriately depending on the application device used. For example, the viscosity at a liquid temperature of 25°C is preferably 500 to 3000 dPa·s, more preferably 700 to 2500 dPa·s, and even more preferably 900 to 2000 dPa·s.

[0049] In this specification, the "viscosity of the conductive composition" is a value measured using a VISCOMETER TVB-10 (manufactured by Toki Sangyo Co., Ltd.) with a spindle No. 7 at a rotation speed of 10 rpm.

[0050] The conductive composition of the present invention can be used, for example, in adhesive and fixing applications requiring high heat resistance, specifically die bonding, bonding to heat sinks and insulating heat dissipation substrates, bonding to high-brightness LEDs, and the like.

[0051] Examples of the present invention will be described below, but the present invention is not limited to these examples. In the following, the blending ratios and the like are based on mass unless otherwise specified.

[0052] Conductive compositions were prepared by mixing the components according to the formulations (parts by mass) shown in Tables 1 and 2. Details of each component in the tables are as follows.

[0053] SnBi alloy particle 1: Sn ratio 72 mass%, Bi ratio 28 mass%, 10% cumulative value (D10) 3 μm, 90% cumulative value (D90) 6 μm SnBi alloy particle 2: Sn ratio 72 mass%, Bi ratio 28 mass%, 10% cumulative value (D10) 6 μm, 90% cumulative value (D90) 13 μm SnBi alloy particle 3: Sn ratio 72 mass%, Bi ratio 28 mass%, 10% cumulative value (D10) 16 μm, 90% cumulative value (D90) 29 μm SnBi alloy particle 4: Sn ratio 72 mass%, Bi ratio 28 mass%, 10% cumulative value (D10) 21 μm, 90% cumulative value (D90) 40 μm

[0054] Sn particle 1: spherical powder, 10% cumulative value (D10) 9.5 μm, average particle diameter (D50) 13 μm, 90% cumulative value (D90) 18 μm. Sn particle 2: spherical powder, 10% cumulative value (D10) 15.5 μm, average particle diameter (D50) 20.1 μm, 90% cumulative value (D90) 27.9 μm. Sn particle 3: spherical powder, 10% cumulative value (D10) 20 μm, average particle diameter (D50) 30 μm, 90% cumulative value (D90) 40 μm. Sn particle 4: spherical powder, 10% cumulative value (D10) 25.9 μm, average particle diameter (D50) 36.7 μm, 90% cumulative value (D90) 49.8 μm. Sn particle 5: spherical powder, 10% cumulative value (D10) 5.7 μm, average particle diameter (D50) 8.6 μm, 90% cumulative value (D90) 13.1 μm Sn particle 6: spherical powder, 10% cumulative value (D10) 32 μm, average particle diameter (D50) 43 μm, 90% cumulative value (D90) 60 μm

[0055] ・Silver coated copper particles 1: average particle size 5 μm, silver content 10% by mass, spherical ・Silver particles: average particle size 2 μm, spherical

[0056] Flux 1: A mixture of 2-propanol (35% by mass) and a mixture of aliphatic dicarboxylic acid having 6 to 8 carbon atoms and rosin-based resin (65% by mass) Flux 2: Triethanolamine Solvent: Terpineol

[0057] The particle diameter of the metal particles was determined using a laser diffraction / scattering measurement device (Aerotrac II manufactured by Microtrac-Bell) as D10 and D90, which were the particle diameters corresponding to 10% and 90% of the cumulative volume distribution (volume distribution). The average particle diameter was determined by similar measurement and was determined as D50, which was the particle diameter corresponding to 50% of the cumulative volume distribution (volume distribution).

[0058] The obtained conductive compositions were evaluated for volume resistivity, die shear strength, shear strength, the presence or absence of voids, and the thickness of the joint, and the results are shown in Tables 1 and 2. The methods for preparing and evaluating the evaluation samples are as follows.

[0059] <Volume Resistivity> The conductive compositions of each Example and Comparative Example were printed on a glass epoxy substrate by metal printing. The printed conductive compositions were then heated at 80°C for 15 minutes, then at 170°C for 30 minutes, and then at 200°C for 30 minutes to harden them, thereby forming five circuit patterns with a length of 60 mm, a width of 1 mm, and a thickness of 50 μm. The resistance between both ends of each pattern was measured using a precision tester. The cross-sectional area (S, cm ２ The volume resistivity (Ω cm) was calculated from the length (L, cm) and the volume resistivity (Ω cm) of the five strips using the following formula (1), and the average value of the five strips was calculated. －５ If the electrical conductivity is Ω·cm or less, it is evaluated as being excellent in electrical conductivity.

[0060] <Die Shear Strength 1> The conductive compositions of each Example and Comparative Example were printed onto a double-sided copper-clad substrate (product name: CS-3305A, manufactured by Risho Kogyo Co., Ltd.) using a 100 μm thick metal printing plate with a 5 mm x 5 mm hole and a metal squeegee. A silver-plated die was mounted on the applied conductive composition, and the composition was heated in an air oven at 80°C for 15 minutes, then at 170°C for 30 minutes, and then at 200°C for 30 minutes to cure. The die shear strength was then measured using a Nordson "4000Plus" measuring device and a Nordson Advanced Technology "S200KG" load cell, and determined to be adhesion 1 (die shear strength 1). The die shear strength was also measured after 1000 cycles of a heat cycle test, and determined to be long-term reliability 1 (die shear strength 1). The die specifications, die shear strength measurement conditions, and heat cycle test were as follows.

[0061] If Adhesion 1 (Die Shear Strength 1) was 13 MPa or more, it was evaluated as excellent adhesion. If Long-Term Reliability 1 (Die Shear Strength 1) was 13 MPa or more, it was evaluated as excellent long-term reliability. Note that some evaluation items were not measured if excellent results were not obtained in other evaluation items. In such cases, they are indicated with "-" in Tables 1 and 2.

[0062] <Die specifications> Silver-plated die: A 20 nm titanium (Ti) plating film, a 200 nm nickel (Ni) plating film, and a 500 nm silver (Ag) plating film are formed in this order on the surface of the die. Dimensions: 5 mm length x 5 mm width x 625 μm thickness

[0063] <Conditions for measuring die shear strength> Measurement height: 0.1 mm Measurement speed: 0.3 mm / s Minimum load: 0.1 kg Maximum load: 100 kg

[0064] <Heat Cycle Test> One cycle is defined as a cycle in which the sample is exposed to a temperature of −65° C. for 30 minutes and then to a temperature of 125° C. for 30 minutes.

[0065] <Die Shear Strength 2> After exposure to an environment at 200°C for 1000 hours, the die shear strength was measured in the same manner as for Adhesion 1 (Die Shear Strength 1), and was designated as Long-Term Reliability 2 (Die Shear Strength 2). If Long-Term Reliability 2 (Die Shear Strength 2) was 13 MPa or higher, it was evaluated as having excellent long-term reliability. Note that some samples were not measured if excellent results were not obtained in other evaluation items. In such cases, this is indicated by "-" in Tables 1 and 2.

[0066] <Shear Strength> The conductive compositions of each Example and Comparative Example were applied to a tough-pitch copper plate. A tough-pitch copper plate was placed on top of the applied conductive composition, clamped with clips, and heated to 170°C for 60 minutes for curing. Shear strength was measured at 25°C and 200°C in accordance with JIS K6850:1999, "Test Method for Tensile Shear Strength of Adhesives." The shear strength measured at 25°C was designated Adhesion 2 (shear strength), and the shear strength measured at 200°C was designated High-Temperature Adhesion 1 (shear strength). Adhesion 2 (shear strength) of 3.5 MPa or higher was evaluated as excellent adhesion. High-Temperature Adhesion 1 (shear strength) of 3.5 MPa or higher was evaluated as excellent high-temperature adhesion. Note that some evaluation items were not measured if excellent results were not obtained in other evaluation items. In such cases, a "-" is indicated in Tables 1 and 2.

[0067] <Presence or absence of cavities> A sample for measuring die shear strength was hardened with a molding resin and subjected to cross-sectional observation. The presence or absence of cavities in the joint between the die and the double-sided copper-clad substrate was confirmed. From the results of cross-sectional observation, the presence or absence of cavities was evaluated according to the following evaluation criteria. A: No cavities with a diameter of 30 μm or more were formed. B: Cavities with a diameter of 30 μm or more were formed.

[0068] <Bond Thickness> The die shear strength measurement sample was hardened with a molding resin and subjected to cross-sectional SEM observation. The thickness of the joint joining the die and the copper-clad substrate was measured. From the results of the cross-sectional SEM observation, the heat dissipation was evaluated according to the following evaluation criteria: A: Excellent heat dissipation (the joint thickness was 60 μm or less). B: Poor heat dissipation (the joint thickness was more than 60 μm).

[0069]

[0070]

[0071] As shown in Table 1, each example was excellent in volume resistivity, adhesion, long-term reliability, and heat dissipation.

[0072] As shown in Table 2, Comparative Example 1 is an example in which the particle size of the SnBi alloy particles exceeds the upper limit and does not contain Sn particles. In Comparative Example 1, cavities with a diameter of 30 μm or more were observed in the joint between the die and the double-sided copper-clad substrate. From this result, it is presumed that when the particle size of the SnBi alloy particles is large, the SnBi alloy particles melt during hardening and flow out through the gaps between the metal particles (B) due to capillary action, forming cavities.

[0073] Comparative Example 2 is an example in which the particle size of the Sn particles was less than the lower limit, and the volume resistivity was poor, and the adhesion 1 was also poor. Note that, since the adhesion 1 was poor, the long-term reliability 1 and 2 were not evaluated. On the other hand, Comparative Example 3 is an example in which the particle size of the Sn particles exceeded the upper limit, and the volume resistivity was poor, and the heat dissipation property was also poor.

[0074] Comparative Example 4 is an example in which the particle size of the SnBi alloy particles exceeds the upper limit, and was inferior in adhesion 1. Therefore, long-term reliability 1 and 2 were not evaluated.

[0075] Comparative Example 5 is an example in which the content of metal particles (A) exceeded the upper limit, and was poor in high-temperature adhesion 1. In Comparative Example 5, long-term reliability 1 and 2 were not evaluated.

[0076] Comparative Example 6 is an example in which the particle size of the SnBi alloy particles is less than the lower limit, and the volume resistivity was poor. Therefore, the long-term reliability 1, 2 and high-temperature adhesion 1 were not evaluated.

[0077] Comparative Example 7 is an example in which only SnBi alloy particles were used as the metal particles (A) and no Sn particles were blended, and the content of the metal particles (A) exceeded the upper limit. Comparative Example 7 was inferior in long-term reliability 2 and high-temperature adhesion 1.

[0078] Comparative Example 8 is an example in which the content of metal particles (A) is less than the lower limit, and the long-term reliability 2 was poor.

[0079] Comparative Example 9 is an example in which the flux content was below the lower limit, and the volume resistivity was poor. Therefore, adhesion 1 and 2, long-term reliability 1 and 2, and high-temperature adhesion 1 were not evaluated. On the other hand, Comparative Example 10 is an example in which the flux content exceeded the upper limit, and the adhesion 1 was poor. Therefore, long-term reliability 1 and 2 were not evaluated.

[0080] The various numerical ranges described in this specification can be arbitrarily combined with their respective upper and lower limit values, and all such combinations are considered to be preferred numerical ranges described in this specification. Furthermore, a numerical range described as "X to Y" means from X to Y.

Claims

1. A conductive composition comprising 2 to 8 parts by mass of flux per 100 parts by mass of metal particles, wherein the 100 parts by mass of the metal particles comprise: 42 to 50 parts by mass of metal particles (A) consisting of SnBi alloy particles and Sn particles; and 25 to 58 parts by mass of metal particles (B) consisting of at least one type of metal particles selected from the group consisting of copper particles, silver particles, and silver-coated copper particles, the metal particles containing at least copper and silver; the SnBi alloy particles have a 10% cumulative value of particle diameter of 4 to 15 μm and a 90% cumulative value of particle diameter of 8 to 25 μm; and the Sn particles have a 10% cumulative value of particle diameter of 7 to 30 μm and a 90% cumulative value of particle diameter of 15 to 50 μm.

2. The conductive composition according to claim 1, wherein the average particle size of the metal particles (B) is 1 to 35 μm.

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