Bonding material

Abstract

Provided is a bonding material which is capable of forming a silver bonding layer that has good bondability with a material to be bonded, wherein the density (denseness) of the silver is good. The bonding material comprises an organic acid silver salt, an organic solvent, and silver particles. The organic acid silver salt has a weight loss rate (Mr1) of 5% or less when the temperature thereof is raised from 25°C to 200°C and a weight loss rate (Mr2) of 40% or more when the temperature thereof is raised from 200°C to 280°C as determined by simultaneous thermogravimetry-differential thermal analysis (TG-DTA) (in a nitrogen atmosphere at a nitrogen flow rate of 200 ml / min and a heating rate of 10° C / min). The organic solvent contains a compound represented by general formula (1) (in the formula, R1 represents a linear or branched alkyl group having 2 to 6 carbon atoms).　The silver particles include: first silver particles that have an average particle diameter (D50 diameter) of 0.15 μm or more and 0.4 μm or less; and at least one of second silver particles that have an average particle diameter (D50 diameter) of 0.6 μm or more and 1.0 μm or less and third silver particles that have an average particle diameter (D50 diameter) of 1.9 μm or more and 2.4 μm or less.

Description

Bonding material

[0001] The present invention relates to a bonding material.

[0002] Compositions containing silver particles exist as bonding materials for bonding a substrate to a semiconductor element, etc. Furthermore, the following bonding materials, for example, have been provided as bonding materials for improving the bonding strength between a substrate and a semiconductor element, etc.

[0003] A thermosetting resin composition (Patent Document 1) comprises (A) plate-shaped silver fine particles, (B) silver powder other than the component (A) having an average particle size of 0.5 to 30 μm, and (C) an epoxy resin, wherein the component (C) is blended in an amount of 1 to 20 parts by mass when the total amount of the silver fine particles of the component (A) and the silver powder of the component (B) is taken as 100 parts by mass.

[0004] A thermosetting resin composition comprising: (A) plate-shaped silver fine particles having an alkylamine or alkoxyamine capping agent attached to the surface; (B) silver powder other than component (A) having an average particle size of 0.5 to 30 μm; and (C) a thermosetting resin, wherein 1 to 20 parts by mass of component (C) is blended when the total amount of the silver fine particles of component (A) and the silver powder of component (B) is taken as 100 parts by mass (Patent Document 2).

[0005] A thermosetting resin composition comprising (A) plate-shaped silver fine particles having a uniform thickness, (B) silver powder other than the component (A) having an average particle size of 0.5 to 30 μm, and (C) a thermosetting resin, wherein the plate-shaped silver fine particles (A) are formed by growing one metal crystal face, and the long side perpendicular to the thickness direction is in the range of 8 to 150 times the thickness, and 1 to 20 parts by mass of the component (C) is blended when the total amount of the silver fine particles of the component (A) and the silver powder of the component (B) is taken as 100 parts by mass (Patent Document 3).

[0006] A thermosetting resin composition comprising (A) silver fine particles having a thickness or minor axis of 1 to 200 nm, (B) silver powder other than the component (A) having an average particle diameter of more than 0.2 μm and not more than 30 μm, (C) resin particles, and (D) a thermosetting resin, wherein, when the total amount of the silver fine particles of the component (A) and the silver powder of the component (B) is taken as 100 parts by mass, the component (C) is blended in an amount of 0.01 to 1 part by mass and the component (D) is 1 to 20 parts by mass (Patent Document 4).

[0007] A paste composition comprising: (A) silver fine particles having a thickness or minor axis of 1 to 200 nm; (B) silver powder other than the (A) silver fine particles having an average particle diameter of more than 0.2 μm and 30 μm or less; (C) a sintering aid containing an acid anhydride structure; and (D) a thermosetting resin other than an epoxy resin, wherein the (C) sintering aid is blended in an amount of 0.01 to 1 part by mass when the total amount of the (A) silver fine particles and the (B) silver powder is taken as 100 parts by mass (Patent Document 5).

[0008] Japanese Patent Publication No. 2016-065146 Japanese Patent No. 6310799 Japanese Patent No. 6333576 Japanese Patent No. 6360157 Japanese Patent No. 7100651

[0009] The above-mentioned composition contains a thermosetting resin or resin particles, which can improve the adhesion between the formed cured product and a substrate, etc. However, the thermosetting resin or resin particles may inhibit the sintering of silver particles during heating, which may reduce the density of the silver component in the cured product.

[0010] The main object of the present invention is to provide a bonding material that can form a bonding layer that has good bonding properties with the materials to be bonded, and in which the density (compactness) of the silver sintered body that constitutes the bonding layer is also good.

[0011] (1) A bonding material according to one aspect of the present invention includes an organic acid silver salt, an organic solvent, and silver particles, and A: the organic acid silver salt has a weight loss rate (Mr １ ) is 5% or less, and the weight loss rate (Mr ２) is 40% or more, and a ring-shaped solder (made of Sn-3.0 wt% Ag-0.5 wt% Cu, wire diameter: 1.6 mm, inner diameter: 3.2 mmφ, height: 1.6 mm) is placed on a phosphorus-deoxidized copper plate of 30 mm × 30 mm × 0.3 mmt, 10 mg of the organic acid silver salt is placed in a hole of the solder, and after reflow treatment under atmospheric conditions with the following temperature profile, the area of ​​the region where the solder and the copper plate are in contact is 32 mm ２ (Temperature profile) 1: Heat from 25°C to 250°C at a temperature increase rate of 1°C / sec. 2: Hold at 250°C for 2 minutes. 3: Cool to 25°C at 3°C / sec. B: The organic solvent contains a compound represented by the following general formula (1), (In the formula, R １ represents a linear or branched alkyl group having 2 to 6 carbon atoms. C: The silver particles have an average particle diameter (D ５０ first silver particles having an average particle diameter (D ５０ second silver particles having an average particle diameter (D ５０ and third silver particles having a diameter of 1.9 μm or more and 2.4 μm or less, and the blending amount of the organic acid silver salt is 2.0 mass % or more and 8.0 mass % or less with respect to the total amount of the bonding material.

[0012] (2) In the bonding material described in (1) above, the organic acid silver salt may be one in which the hydrogen radical of a monobasic acid having 4 to 7 carbon atoms, including an alkoxy group, is substituted with a silver ion.

[0013] (3) In the bonding material described in (2) above, the organic acid silver salt can be represented by the following general formula (2). (In the formula, R ２ represents a linear or branched alkyl or alkoxy group having 2 to 5 carbon atoms.

[0014] (4) In the bonding material according to any one of (1) to (3) above, the blending amount of the organic solvent can be set to 5.0 mass % or more and 20.0 mass % or less with respect to the total amount of the bonding material.

[0015] (5) In the bonding material according to any one of (1) to (4) above, the blending amount of the silver particles can be 80.0 mass % or more with respect to the total amount of the bonding material.

[0016] (6) In the bonding material according to any one of (1) to (5) above, the ratio of the amount of the organic silver salt to the amount of the silver particles can be set to a mass ratio of 1:10 to 1:50.

[0017] (7) In the bonding material according to any one of (1) to (6) above, the organic acid silver salt can be at least one selected from the group consisting of silver ethoxyacetate, 2-(2-methoxyethoxy)silver acetate, and [2-(2-methoxyethoxy)ethoxy]silver acetate.

[0018] (8) In the bonding material according to any one of (1) to (7) above, the ratio of the amounts of the first silver particles, the second silver particles, and the third silver particles can be set to a mass ratio of 10:90 to 90:10, where the mass ratio is the amount of the first silver particles:the total amount of the second silver particles and the third silver particles.

[0019] (9) In the bonding material according to any one of (1) to (8) above, the ratio of the amounts of the first silver particles, the second silver particles, and the third silver particles can be set to a mass ratio of the amount of the first silver particles:the amount of the second silver particles:the amount of the third silver particles=10:50:40 to 80:10:10.

[0020] (10) A bonding layer according to one aspect of the present invention includes a sintered body obtained by heating the bonding material according to any one of (1) to (9) above.

[0021] (11) A method for manufacturing a bonded structure having a bonding layer, which is one aspect of the present invention, includes a coating step of coating a substrate with the bonding material described in any one of (1) to (9) above, a placing step of placing a semiconductor element on the applied bonding material, and a heating step of heating the substrate, bonding material, and semiconductor element to form a bonding layer.

[0022] (12) In the method for manufacturing a bonded structure described in (11) above, the maximum heating temperature in the heating step can be 250°C.

[0023] (1) A schematic top view showing a state in which an organic acid silver salt is placed in a hole in a ring-shaped solder placed on a phosphorus-deoxidized copper plate in a wetting and spreading evaluation. (2) A schematic front view showing the position of the interface at which a test bonded body is photographed using an ultrasonic microscope in a bondability evaluation. (2) Images of a test bonded body photographed using an ultrasonic microscope in a bondability evaluation, where (a) is an image (Image A) photographed from the Si chip side with no unbonded regions, and (b) is an image (Image B) photographed from the oxygen-free copper plate side with no unbonded regions. (2) Images of a test bonded body photographed using an ultrasonic microscope in a bondability evaluation, where (a) is an image (Image A) photographed from the Si chip side with unbonded regions, and (b) is an image (Image B) photographed from the oxygen-free copper plate side with unbonded regions. (3) A longitudinal cross-sectional SEM image of a test bonded body used in measuring porosity in a compactness evaluation. (3) A longitudinal cross-sectional SEM image of the bonding layer used to measure the porosity in the compactness evaluation.

[0024] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0025] 1. Bonding Material The bonding material of the present embodiment contains an organic acid silver salt, an organic solvent, and silver particles.

[0026] A: Organic Acid Silver Salt The organic silver acetate is a silver salt in which an organic acid is coordinately bonded to a silver atom as a ligand.

[0027] The weight loss rate (Mr １ ) is 5% or less, and the weight loss rate (Mr ２ ) is 40% or more.

[0028] The detailed measurement conditions for the TG-DTA measurement are as follows: (Sample) 10 mg of organic acid silver salt (powder form) (Apparatus) Differential thermal-thermogravimetric simultaneous analysis measuring apparatus: STA7200RV (manufactured by Hitachi High-Tech Science Corporation) (Other conditions) Sample container: made of aluminum, reference material: aluminum oxide, heating rate: 10°C / min, measurement temperature range: 35°C to 350°C, atmosphere: nitrogen gas 200 ml / min

[0029] Weight reduction rate (Mr １ ) and (Mr ２ ) can be calculated using the following formulas (1) and (2): １ )(%)=100×((M ０ )-(M １ )) / (M ０ )…Equation (1) Weight reduction rate (Mr ２ )(%)=100×((M １ )-(M ２ )) / (M １ )…Formula (2) *(M ０ ): weight of sample before TG-DTA measurement (M １ ): Weight of sample at 200 ° C. in TG-DTA measurement (M ２ ): Weight of sample at 280°C in TG-DTA measurement

[0030] The organic silver salt is resistant to thermal decomposition in the temperature range of from room temperature to 200° C., but is easily decomposed in the temperature range of from above 200° C. to 280° C. Therefore, in the TG-DTA measurement, the weight loss occurring between above 200° C. and 280° C. is thought to be due to thermal decomposition of the organic silver salt, and the weight loss occurring between room temperature and 200° C. is thought to be due to impurities introduced during the synthesis of the organic silver salt.

[0031] Silver particles with nano- or submicron-order particle sizes begin sintering in the temperature range of 140°C to 220°C. If the organic silver salt were to thermally decompose in this temperature range, the generated gas could inhibit the sintering of the silver particles. Because the organic silver salt used in this embodiment has a higher thermal decomposition temperature than this, sintering proceeds without inhibiting the bonding of the silver particles. Furthermore, the thermal decomposition of the organic silver salt after the start of sintering of the silver particles allows the gaps between the silver particles to be filled, thereby improving the density of the sintered body. Hereinafter, silver particles and precipitated silver may be collectively referred to as the "silver component."

[0032] Furthermore, the organic acid contained in the organic acid silver salt is completely thermally decomposed (vaporized) under heating conditions in which a temperature of 250°C is maintained for 5 minutes or more under atmospheric conditions. Therefore, a bonding material containing the organic acid silver salt is unlikely to generate voids even when the maximum heating temperature is 250°C (under heating conditions in which the same temperature is maintained for 5 minutes or more), and can provide a bonding layer in which no organic components derived from the organic acid silver salt remain. Note that the maximum heating temperature can, of course, be 250°C or higher.

[0033] The organic acid silver salt was prepared by placing a ring-shaped solder (made of Sn-3.0 wt % Ag-0.5 wt % Cu, wire diameter: 1.6 mm, inner diameter: 3.2 mmφ, height: 1.6 mm) on a phosphorus-deoxidized copper plate of 30 mm × 30 mm × 0.3 mmt, placing 10 mg of the organic acid silver salt in a hole in the solder, and performing a reflow treatment under atmospheric conditions with the following temperature profile. After that, the area of ​​the region where the solder and the copper plate were in contact was 32 mm ２ This is the result. Such organic acid silver salt has good reducing properties and can sufficiently remove the oxides on the bonding surfaces of the silver particles and the materials to be bonded. (Temperature profile) 1: Heat from 25°C to 250°C at a rate of 1°C / sec 2: Hold at 250°C for 2 minutes 3: Cool to 25°C at a rate of 3°C / sec (Reflow equipment used) SMT Scope SK-5000 (manufactured by Sanyo Seiko)

[0034] Examples of the organic acid silver salt include those in which the hydrogen radical of a monobasic acid having 4 to 7 carbon atoms, more preferably 4 to 5 carbon atoms, containing an alkoxy group is substituted with a silver ion. Furthermore, as such an organic acid silver salt, those represented by the following general formula (2) can be used, and in particular, at least one selected from the group consisting of silver ethoxyacetate, silver 2-(2-methoxyethoxy)acetate, and silver [2-(2-methoxyethoxy)ethoxy]acetate can be used. The organic acid silver salt blended in the bonding material of this embodiment may be one type or multiple types. (In the formula, R ２ represents a linear or branched alkyl or alkoxy group having 2 to 5 carbon atoms.

[0035] The organic acid silver salt can be obtained, for example, by mixing a silver nitrate solution prepared by mixing silver nitrate with water or an organic solvent (such as an alcohol, alkane, alkene, alkyne, ketone, ether, ester, nitrile, acetone, formic acid, acetic acid, glycolic acid, propionic acid, lactic acid, pyruvic acid, acrylic acid, butyric acid, pivalic acid, aminobutyric acid, or valeric acid) with an organic acid solution prepared by mixing a monobasic acid having 4 to 7 carbon atoms and an alkoxy group with water or an organic solvent (such as an alcohol, alkane, alkene, alkyne, ketone, ether, ester, nitrile, acetone, formic acid, acetic acid, glycolic acid, propionic acid, lactic acid, pyruvic acid, acrylic acid, butyric acid, pivalic acid, aminobutyric acid, or valeric acid) to form a precipitate, and then filtering and washing the precipitate with an organic solvent.

[0036] The blending amount of the organic acid silver salt is 2.0% by mass or more and 8.0% by mass or less with respect to the total amount of the bonding material. The blending amount of the organic acid silver salt may be 3.0% by mass or more and 7.0% by mass or less, 4.0% by mass or more and 6.0% by mass or less, or 4.0% by mass or more and 5.0% by mass or less with respect to the total amount of the bonding material.

[0037] B: Organic Solvent The organic solvent contains a compound represented by the following general formula (1). (In the formula, R １represents a linear or branched alkyl group having 2 to 6 carbon atoms.) Examples of the organic solvent include diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and diethylene glycol monohexyl ether. The organic solvent blended in the bonding material of this embodiment may be one type or multiple types.

[0038] In the bonding material of this embodiment, the organic silver salt, which has excellent reduction properties, is dispersed among the silver particles by the organic solvent. Therefore, during thermal decomposition of the organic silver salt, the oxide film present on the silver particles is efficiently reduced, further accelerating the sintering of the silver component. Furthermore, the silver particles are more likely to be uniformly sintered. Furthermore, the silver precipitated by thermal decomposition of the organic silver salt easily penetrates into the gaps (cavities) between the sintered silver particles, further improving the density of the sintered silver body that constitutes the bonding layer. Furthermore, since the organic silver salt is more likely to be uniformly dispersed on the bonding surfaces of the bonded materials, the oxide film present on the bonding surfaces is efficiently reduced during thermal decomposition of the organic silver salt, accelerating the diffusion of the silver component to the bonding surfaces. This improves the bonding strength of the bonding layer.

[0039] The blending amount of the organic solvent may be 3.0 mass % or more and 20.0 mass % or less with respect to the total amount of the bonding material. Note that the blending amount of the organic solvent may be 4.0 mass % or more and 18.0 mass % or less, 5.0 mass % or more and 16.0 mass % or less, 6.0 mass % or more and 14.0 mass % or less, 7.0 mass % or more and 12.0 mass % or less, or 8.0 mass % or more and 10.0 mass % or less with respect to the total amount of the bonding material.

[0040] C: Silver particles The silver particles have an average particle diameter (D ５０ first silver particles having an average particle diameter (D ５０ second silver particles having an average particle diameter (D ５０ and third silver particles having a diameter of 1.9 μm or more and 2.4 μm or less. In this specification, silver particles refer to metal particles composed of silver atoms.

[0041] The first silver particles, the second silver particles, and the third silver particles all have an average particle diameter (D ５０ The average particle diameter (D ) refers to the 50% integrated value (50% particle diameter) in a volume-based particle size distribution curve obtained by measurement using a laser diffraction particle size distribution analyzer (wet). The shapes of the first silver particles, the second silver particles, and the third silver particles may be, for example, spherical, approximately spherical, flake-like, scale-like, plate-like, rod-like, etc. The first silver particles, the second silver particles, and the third silver particles may each contain one type of silver particle or multiple types of silver particles. That is, for example, the first silver particles may have an average particle diameter (D ５０ diameter) of 0.15 μm and silver particles with an average particle diameter (D ５０ The first silver particles, the second silver particles, and the third silver particles may be either silver particles coated with an organic substance or silver particles not coated with an organic substance.

[0042] The bonding material of this embodiment contains the first silver particles and at least one of the second silver particles and the third silver particles. During heating, the first silver particles penetrate into the gaps between the second silver particles, the third silver particles, or the gaps between the second and third silver particles. This increases the number of contact points between the silver particles, making them more susceptible to sintering. This contributes to improving the density of the silver sintered body that constitutes the bonding layer.

[0043] The bonding material of the present embodiment may contain silver particles (other silver particles) other than the first silver particles, the second silver particles, and the third silver particles.

[0044] The blending amount of the silver particles (total amount) can be 80.0 mass % or more with respect to the total amount of the bonding material. The blending amount of the silver particles (total amount) can be 85.0 mass % or more with respect to the total amount of the bonding material. The combined blending amount of the first silver particles and at least one of the second silver particles and the third silver particles can be 80.0 mass % or more with respect to the total amount of the bonding material. The combined blending amount can be 85.0 mass % or more with respect to the total amount of the bonding material.

[0045] The ratio of the amount of the first silver particles to the amount of at least one of the second silver particles and the third silver particles (first silver particles: total amount of the second silver particles and the third silver particles) by mass can be 10:90 to 90:10, 20:80 to 80:20, or 25:75 to 75:25. The ratio of the amount of the first silver particles to the amount of the second silver particles to the amount of the third silver particles (first silver particles: second silver particles: third silver particles) by mass can be 10:50:40 to 80:10:10, 30:40:30 to 80:10:10, or 33:34:33 to 75:15:10.

[0046] Furthermore, in the bonding material of this embodiment, the ratio of the amount of the organic silver salt to the amount of the silver particles, in mass ratio, can be 1:10 to 1:50, 1:15 to 1:30, or 1:15 to 1:25. The bonding material in which the ratio of the amount of the organic silver salt to the amount of the silver particles is within the above range can further improve the bonding property of the bonding layer and can also further improve the density of the silver sintered body that constitutes the bonding layer.

[0047] The bonding material of this embodiment may contain other components as long as the effects of the bonding material are not impaired.

[0048] The bonding material of this embodiment can be produced using a known method. For example, the bonding material is produced by the following procedure: (i) Stirring and dispersing each component other than silver particles; (ii) Adding silver particles to the stirred and dispersed mixture, and pre-stirring using a stirrer; (iii) Stirring the pre-stirred mixture using a three-roll mill. Note that in the above step (iii), ultrasonic dispersion, a disperser, a ball mill, a bead mill, or the like may be used instead of the three-roll mill.

[0049] As described above, the bonding material of this embodiment promotes sintering of the silver component over a wide range without impeding the contact of the silver particles at temperatures from above 200°C to 280°C. Furthermore, the silver precipitated during this process fills the gaps (voids) between the sintered silver particles, improving the density of the silver sintered body that constitutes the bonding layer. Therefore, the bonding material can form a bonding layer having a silver sintered body with good density. Furthermore, the organic acid silver salt can sufficiently remove the silver component and the oxide film present on the bonding surface of the bonded material over a wide range during thermal decomposition, promoting the diffusion of the silver component to the bonding surface. Therefore, the bonding material can form a bonding layer with good bonding strength.

[0050] Furthermore, as described above, the organic acid contained in the organic acid silver salt is completely thermally decomposed under heating conditions in which a temperature of 250°C is maintained for 5 minutes or more under atmospheric conditions. Therefore, the bonding material of this embodiment is unlikely to generate voids even when the maximum heating temperature is 250°C (under heating conditions in which the same temperature is maintained for 5 minutes or more), and can provide a bonding layer in which no organic components derived from the organic acid silver salt remain. Note that the maximum heating temperature can, of course, be 250°C or higher.

[0051] Furthermore, the silver precipitated during the thermal decomposition of the organic acid silver salt fills the gaps between the silver particles, further promoting sintering of the silver particles without the application of physical pressure. Therefore, a highly dense bonding layer can be formed without the need for pressure. Furthermore, even when the bonding surface is composed of a component other than silver (e.g., a dissimilar metal such as copper), the bonding material allows the silver component to be sufficiently diffused into the bonding surface, thereby forming a bonding layer with good bonding strength even for such materials to be bonded.

[0052] 2. Sintered Body / Bonding Layer The sintered body of this embodiment is obtained by heating the bonding material. The sintered body constitutes the bonding layer of this embodiment. The bonding layer bonds the bonded materials together. Examples of the bonded materials include silicon wafers, substrates (including printed wiring boards, Cu substrates, DBC (Direct Bonded Copper) substrates, DBA (Direct Bonded Aluminum) substrates, etc.), heat sinks, cooling fins, electronic components, semiconductor elements, and semiconductor packages. Different types of bonded materials may be used, or the same type of bonded material may be used. The bonding layer is particularly suitable for bonding substrates and semiconductor elements. As described above, the bonding layer of this embodiment also has good bonding strength for substrates and / or semiconductor elements whose bonded surfaces are composed of components other than silver.

[0053] 3. Bonded Structure The bonded structure of this embodiment has, for example, a first bonded material, a bonding layer, and a second bonded material. The bonding layer is obtained by heating the bonding material. The first bonded material and the second bonded material are bonded via the bonding layer. The first bonded material and the second bonded material can be the same as those described above.

[0054] The bonded structure of this embodiment is fabricated, for example, by the following method. That is, when a Cu substrate is used as the first bonded material and a semiconductor element is used as the second bonded material, the bonding material is first applied to a predetermined position on the Cu substrate, and the semiconductor element is placed on the applied bonding material. Then, these are reflowed under predetermined temperature conditions, for example, the following temperature profile, to form a bonding layer bonding the Cu substrate and the semiconductor element. (Temperature Profile) 1: Heat from 25°C to 250°C at a heating rate of 5°C / min. 2: Hold at 250°C for 10 minutes. 3: Cool to 50°C or below at a rate of 10°C / min. As described above, the organic acid contained in the organic acid silver salt is completely thermally decomposed under atmospheric conditions, maintaining a temperature of 250°C for 5 minutes or more. Therefore, even if the maximum heating temperature in the above temperature profile is 250° C., the heating condition is to maintain the same temperature for 5 minutes or more, so that voids are unlikely to occur and a bonded structure having a bonding layer in which no organic components derived from the organic acid silver salt remain can be produced. Note that the maximum heating temperature can, of course, be 250° C. or higher.

[0055] The bonding material can be applied to the Cu substrate by any known method, such as a dispenser application method, a screen printing method, or an inkjet printing method. The thickness of the applied film of the bonding material and the reflow conditions (such as the temperature profile conditions) can be changed as needed.

[0056] When manufacturing a semiconductor package having the above-described bonded structure, the semiconductor element and the lead frame are bonded using wires. Next, the Cu substrate on which the semiconductor element is mounted and the heat dissipation substrate are soldered together, and these are then covered with a housing. After that, the housing is filled with a molding resin and cured.

[0057] The bonding layer is formed using the bonding material. Therefore, the bonded structure (and semiconductor package) of this embodiment can be produced without pressure. Furthermore, even if the bonded surfaces of the Cu substrate and the semiconductor element are made of a component other than silver (i.e., there is no silver coating), the bonding layer has good bonding strength to these bonded materials.

[0058] The joint structure (and semiconductor package) of this embodiment can be modified in various ways as long as the effects thereof are not impaired.

[0059] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0060] (Preparation of Organic Acid Silver Salt) Silver Ethoxy Acetate: 10 g of silver nitrate (59 mmol) was dissolved in 8 ml of acetonitrile in a container, and 200 ml of ethanol was added to prepare a silver nitrate solution. Separately, a mixture of 7.81 g of ethoxyacetic acid (11.5 ml, 75 mmol), 6.57 g of triethylamine (9.0 ml, 65 mmol), and 100 ml of ethanol was prepared to prepare an organic acid solution. The silver nitrate solution was added to this organic acid solution at a constant rate, stirred for 15 minutes, and then allowed to stand for 2 hours. The precipitate formed in the container was filtered and washed with ethanol to obtain silver ethoxy acetate. All of the above operations were performed at room temperature. The weight loss rate (Mr) of the prepared silver ethoxy acetate when heated from 35°C to 200°C was measured by simultaneous differential thermal analysis (TG-DTA) (conditions: nitrogen atmosphere, nitrogen flow rate 200 ml / min, heating rate 10°C / min). １ ) and the weight loss rate when the temperature is increased from 200°C to 280°C (Mr ２ ) and the weight loss rate (Mr １ ) is 1.43%, weight reduction rate (Mr ２ ) was 56.69%.

[0061] Silver 2-(2-methoxyethoxy)acetate was obtained by the same method as for the silver ethoxyacetate described above, except that 10.06 g (11.5 ml, 75 mmol) of 2-(2-methoxyethoxy)acetic acid was used instead of ethoxyacetic acid. The weight loss rate (Mr １ ) and weight loss rate (Mr ２ ) and the weight loss rate (Mr １ ) is 1.10%, weight reduction rate (Mr ２) was 54.56%.

[0062] [2-(2-Methoxyethoxy)ethoxy]silver acetate [2-(2-Methoxyethoxy)ethoxy]silver acetate was obtained in the same manner as the above-mentioned silver ethoxyacetate, except that 13.36 g (11.5 ml, 75 mmol) of [2-(2-Methoxyethoxy)ethoxy]acetic acid was used instead of ethoxyacetic acid. The weight loss rate (Mr １ ) and weight loss rate (Mr ２ ) and the weight loss rate (Mr １ ) is 0.64%, weight reduction rate (Mr ２ ) was 56.73%.

[0063] Silver neodecanoate 10 g of silver nitrate was added to 100 ml of ion-exchanged water to prepare a silver nitrate aqueous solution. Meanwhile, 3 g of sodium hydroxide and 3.84 g of neodecanoic acid were added to 100 ml of ion-exchanged water to prepare a neodecanoic acid aqueous solution. Silver nitrate aqueous solution was added dropwise to the above neodecanoic acid aqueous solution, and the mixture was stirred at room temperature for 15 minutes to prepare a precipitate. The precipitate was filtered using a suction filter, washed with 200 ml of ion-exchanged water, and then filtered again to obtain silver neodecanoate. The weight loss rate (Mr １ ) and weight loss rate (Mr ２ ) and the weight loss rate (Mr １ ) is 6.62%, and the weight loss rate when the temperature is increased from 200 ° C to 280 ° C (Mr ２ ) was 49.87%.

[0064] Then, each bonding material was prepared by mixing the compositions in Tables 1 and 2. The bonding materials were prepared by the following procedure: (i) Each component other than silver particles was stirred and dispersed. (ii) Silver particles were added to the stirred and dispersed mixture, and pre-mixing was performed using a mixer (product name: Awatori Rentaro, manufactured by Thinky Corporation). (iii) The pre-mixed mixture was stirred using a three-roll mill (product name: BR-150V, manufactured by Imex Co., Ltd.). Unless otherwise noted, the units of values ​​shown in Tables 1 and 2 are % by mass.

[0065]

[0066] *1 Isostearyl alcohol (Kyushu Alcohol Kogyo Co., Ltd.) *2 Average particle size (D ５０ ) 0.22 μm: Developed by Toyo Chemical Industry Co., Ltd. *3 Average particle diameter (D ５０ ) 0.8 μm: DOWA Electronics Co., Ltd. *4 Average particle diameter (D ５０ ) 2.1 μm: manufactured by DOWA Electronics Co., Ltd.

[0067] (1) Wetting and Spreading Evaluation A ring-shaped solder 200 (made of Sn-3.0 wt% Ag-0.5 wt% Cu, wire diameter WD: 1.6 mm, inner diameter ID: 3.2 mmφ, height: 1.6 mm) was placed on a phosphorus-deoxidized copper plate 100 measuring 30 mm x 30 mm x 0.3 mmt. Then, as shown in Figure 1, 10 mg of each organic acid silver salt (210) was placed in the hole of the solder. After reflow treatment under atmospheric conditions using the following temperature profile, the area of ​​contact between the solder and the copper plate was calculated. (Temperature Profile) 1: Heat from 25°C to 250°C at a heating rate of 1°C / sec. 2: Hold at 250°C for 2 minutes. 3: Cool to 25°C at a rate of 3°C / sec. The calculated area was then evaluated according to the following criteria. The results are shown in Table 3. ◯: Calculated area is 32 mm ２ ×: The calculated area is 32 mm or more ２ is less than

[0068]

[0069] (2) Bondability Evaluation The following tools were prepared for each bonding material: - Oxygen-free copper plate (cleaned with 5% hydrochloric acid; size: 20 mm × 20 mm × 1 mm thick) - Metal mask (size: 5 mm × 5 mm × 0.08 mm thick, with a predetermined pattern) - Si chip (size: 5 mm × 5 mm × 0.1 mm thick, with back metal (Ti / Ag (Ti thickness: 150 nm, Ag thickness: 300 nm)))) Then, the test was performed according to the following procedure. The bonding material was printed on the oxygen-free copper plate using the metal mask. Then, the Si chip was placed at a predetermined position on the printed bonding material using a manual die bonder (manufactured by Dr. TRESKY). The printed film thickness of the bonding material was adjusted using the metal mask. Next, the oxygen-free copper plate on which the Si chip was placed was reflowed using a reflow machine (product name: SMT Scope SK-5000, manufactured by Sanyo Seiko Co., Ltd.) under the following temperature profile conditions (peak temperature: 250°C) in an atmosphere with an oxygen concentration of 200 ppm to produce a test bonded body having a bonding layer bonding the oxygen-free copper plate and the Si chip. (Temperature Profile) 1: Heat from 25°C to 250°C at a temperature increase rate of 5°C / min 2: Hold at 250°C for 10 minutes 3: Cool to 50°C or below at a rate of 10°C / min

[0070] Then, the following images were obtained for the test bonded body using an ultrasonic microscope (product name: C-SAM Gen6, manufactured by Nordson Advanced Technologies). Image A: An image of the bonding interface (X) between the Si chip and the bonding layer (bonding layer 500) taken from the Si chip (Si chip 400) side (see FIGS. 2, 3(a), and 4(a)). Image B: An image of the bonding interface (Y) between the oxygen-free copper plate and the bonding layer (bonding layer 500) taken from the oxygen-free copper plate (oxygen-free copper plate 600) side (see FIGS. 2, 3(b), and 4(b)).

[0071] The entire area in image A where the Si chip and the bonding layer overlap was designated as area A, and the entire area in image B where the oxygen-free copper plate and the bonding layer overlap was designated as area B. The following areas were then calculated. Area X: The sum of the areas of area A and area B. Area Y: The sum of the area of ​​the white area in area A (unbonded area, see the area surrounded by the dotted line in FIG. 4( a)) and the area of ​​the white area in area B (unbonded area, see the area surrounded by the dotted line in FIG. 4( b)). Area Z: The value calculated by subtracting the area Y from the area X (the area of ​​the bonded area). Note that FIG. 3( a) is an image of the bonded interface (X) without the unbonded area, FIG. 3( b) is an image of the bonded interface (Y) without the unbonded area, FIG. 4( a) is an image of the bonded interface (X) with the unbonded area, and FIG. 4( b) is an image of the bonded interface (Y) with the unbonded area.

[0072] The bonding rate (%) of the test bonded body was calculated using the following formula and evaluated based on the following criteria. The results are shown in Tables 4 and 5. Bonding rate (%) = Area Z / Area X × 100 ◎: Bonding rate is 99% or more ○: Bonding rate is 95% or more but less than 99% △: Bonding rate is 90% or more but less than 95% ×: Bonding rate is less than 90%

[0073] (3) Density Evaluation Tests were conducted for each bonding material according to the following procedure. The test bonded bodies prepared in the above (2) Bondability Evaluation were sealed with resin (product name: Epomount Main Agent, manufactured by Refine Tech Co., Ltd., Epomount Hardener II, manufactured by Refine Tech Co., Ltd.), and the surfaces of these were polished using a polishing machine (product name: Tegramin-25, manufactured by Struers). The polished surfaces of the test bonded bodies were further polished using an ion milling machine (product name: IM4000, manufactured by Hitachi High-Tech Corporation). Next, a scanning electron microscope (product name: JSM-7001F, manufactured by JEOL Ltd.) was used to photograph a longitudinal cross-sectional image (backscattered electron image, see FIG. 5) of the test bonded body after polishing. Then, an image was obtained by trimming the bonding layer portion from the longitudinal cross-sectional image (see FIG. 6). The porosity (%) of this trimmed image was measured using image analysis software ImageJ. The porosity (%) was calculated using the following procedure. The area of ​​the entire trimmed image was calculated. Next, a black area in the trimmed image was designated as a selected range, and its area was calculated. The porosity (%) was calculated by dividing the area of ​​the black area by the area of ​​the entire trimmed image x 100. The value calculated by 100% - porosity (%) was taken as the density (%), and evaluated based on the following criteria. The results are shown in Tables 4 and 5. ◎: Density is 85% or more ○: Density is 80% or more but less than 85% △: Density is 70% or more but less than 80% ×: Density is less than 70%

[0074]

[0075]

[0076] As described above, the bonding material of this example can promote sintering of the silver component over a wide range when heated. Furthermore, during this process, the silver precipitated by thermal decomposition of the specified organic acid silver salt is easily dispersed within the bonding layer. Furthermore, the organic acid constituting the organic acid silver salt is completely vaporized by leaving the material at a temperature of 250°C for 5 minutes or more. Therefore, the bonding material of this example can form a bonding layer that has good density even under heating conditions with a peak temperature of 250°C and is less likely to develop voids derived from the organic component derived from the organic acid silver. Furthermore, the organic acid silver salt thermally decomposed within the above temperature range can sufficiently remove the silver component and the oxide film present on the bonding surfaces of the bonding materials (the oxygen-free copper plate substrate and the Si chip) over a wide range, promoting the diffusion of the silver component to the bonding surfaces. Therefore, the bonding material of this example can form a bonding layer with good bonding strength to the bonding materials.

[0077] Furthermore, the promotion of sintering of the silver component, the dispersion of silver, and the diffusion of the silver component to the bonding surfaces do not necessarily require the application of pressure. Therefore, the bonding material of the present embodiment can achieve the above-described effects even when bonding is performed without applying pressure.

[0078] Furthermore, according to the bonding material of this embodiment, even when bonding the oxygen-free copper plate or the Si chip whose bonding surface is composed of a component other than silver, the silver component is sufficiently diffused onto the bonding surface, so that a bonding layer having good bonding strength can be formed even for such materials to be bonded.

[0079] 100: Copper plate 200: Ring-shaped solder 210: Hole 300: Organic acid silver salt 400: Si chip 500: Bonding layer 600: Oxygen-free copper plate

Claims

1. A silver salt of an organic acid, an organic solvent, and silver particles, wherein A: the silver salt of an organic acid is measured by simultaneous differential thermal analysis (TG-DTA) (conditions: under nitrogen atmosphere, nitrogen flow rate 200 ml / min, heating rate 10°C / min) to determine the weight loss rate (Mr １ ) is 5% or less, and the weight loss rate (Mr ２ ) is 40% or more, and a ring-shaped solder (made of Sn-3.0 wt% Ag-0.5 wt% Cu, wire diameter: 1.6 mm, inner diameter: 3.2 mmφ, height: 1.6 mm) is placed on a phosphorus-deoxidized copper plate of 30 mm × 30 mm × 0.3 mmt, 10 mg of the organic acid silver salt is placed in a hole of the solder, and after reflow treatment under atmospheric conditions with the following temperature profile, the area of ​​the region where the solder and the copper plate are in contact is 32 mm ２ (Temperature profile) 1: Heat from 25°C to 250°C at a temperature increase rate of 1°C / sec. 2: Hold at 250°C for 2 minutes. 3: Cool to 25°C at 3°C / sec. B: The organic solvent contains a compound represented by the following general formula (1), (In the formula, R １ represents a linear or branched alkyl group having 2 to 6 carbon atoms. C: The silver particles have an average particle diameter (D ５０ first silver particles having an average particle diameter (D ５０ second silver particles having an average particle diameter (D ５０ and at least one third silver particle having a diameter of 1.9 μm or more and 2.4 μm or less, wherein the blending amount of the organic acid silver salt is 2.0 mass % or more and 8.0 mass % or less with respect to the total amount of the bonding material.

2. The bonding material according to claim 1, wherein the organic acid silver salt is a monobasic acid containing an alkoxy group and having 4 to 7 carbon atoms, in which the hydrogen radical is substituted with a silver ion.

3. The bonding material according to claim 2, wherein the organic acid silver salt is represented by the following general formula (2): (In the formula, R ２ represents a linear or branched alkyl or alkoxy group having 2 to 5 carbon atoms.

4. The bonding material according to any one of claims 1 to 3, wherein the blending amount of the organic solvent is 3.0 mass % or more and 20.0 mass % or less with respect to the total amount of the bonding material.

5. The bonding material according to any one of claims 1 to 4, wherein the blending amount of the silver particles is 80.0 mass % or more with respect to the total amount of the bonding material.

6. The bonding material according to any one of claims 1 to 5, wherein the ratio of the organic acid silver salt to the silver particles is, in mass ratio, 1:10 to 1:50.

Images