Paste-like silver particle composition, method for manufacturing the paste-like silver particle composition, method for manufacturing a metal member assembly, and metal member assembly

Abstract

The present invention provides a paste-like silver particle composition that suppresses the deterioration of adhesive performance due to changes over time after the preparation of the silver particle composition, while also enabling short-time bonding treatment. [Solution] The paste-like silver particle composition is a paste-like silver particle composition that melts upon heating at 200-260°C and adheres to a substrate, comprising: first silver particles with an average particle size of 2-5 μm and coated with an organic substance having polar groups; second silver particles with an average particle size of 0.5-1 μm and coated with an organic substance having polar groups; third silver particles with an average particle size of 50 nm-300 nm and coated with an organic substance having polar groups; a volatile dispersion medium; a diamine compound; and a fatty acid having 6-10 carbon atoms, wherein the diamine compound is present in an amount of 0.5-5% by weight of the total weight, and the fatty acid is present in an amount of 0.5-2% by weight of the total weight, and the combined weight of the diamine compound and the fatty acid is 2-5% by weight of the total weight.

Description

Technical Field

[0001] The present invention relates to a paste-like silver particle composition, a method for producing the paste-like silver particle composition, a method for producing a metal member joined body, and a metal member joined body, and particularly to a paste-like silver particle composition having enhanced bonding strength and storage stability and a method for producing the same, and further to a metal member joined body using the paste-like silver particle composition and a method for producing the same.

Background Art

[0002] A conductive paste in which silver powder is dispersed in an organic resin composition forms a conductive film, a conductive layer, etc. by curing upon heating. Therefore, the conductive paste is used for forming a conductive circuit on a printed circuit board, forming electrodes of various electronic components such as resistors and capacitors, forming electrodes of various display elements, forming a conductive film for electromagnetic wave shielding, and further for adhering chip components such as capacitors, resistors, diodes, memories, and arithmetic elements (CPUs) to a substrate, forming electrodes of a solar cell, particularly electrodes of a solar cell that cannot be subjected to high-temperature treatment using an amorphous silicon semiconductor, and forming external electrodes of chip-type ceramic electronic components such as multilayer ceramic capacitors, multilayer ceramic inductors, and multilayer ceramic actuators.

[0003] The use in the above-mentioned wide range of applications, and further, the improvement of wiring and electrode formation technologies such as the inkjet printing method and the screen printing method are being promoted. Therefore, silver particles as a conductive filler have been practically applied in advance in terms of electrical resistance and ease of micronization.

[0004] Here, further improvement in the adhesiveness of the silver particle composition to a substrate is required. Specifically, it is from the viewpoints of the fixing property of the particles and the melting property by heating during joining by an additive added to the silver particles (see Patent Documents 1, 2, and 3). Currently, fatty acids are frequently used as additives, and the addition of aliphatic amines has also been proposed.

[0005] The use of silver particles and additives disclosed in the aforementioned patent document has improved adhesion to the substrate. However, a new issue has emerged: a decline in adhesive performance (adhesion strength) over time when the prepared silver particle composition is stored and then used for actual substrate bonding. Furthermore, there is a growing demand for reduced melting time in order to improve production efficiency in manufacturing sites. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 4470193 [Patent Document 2] Patent No. 6624620 [Patent Document 3] Japanese Patent Publication No. 2016-33259 [Overview of the project] [Problems that the invention aims to solve]

[0007] After extensive research, the inventors discovered a silver particle composition and a manufacturing method that can address the deterioration of adhesive performance over time. Specifically, by revising the compound composition and preparation method, they were able to suppress performance degradation and enable bonding treatment in a shorter time.

[0008] The present invention has been made in view of the above points, and provides a paste-like silver particle composition that suppresses the deterioration of adhesive performance due to changes over time after the preparation of the silver particle composition and enables bonding treatment in a short time, and also provides a method for producing a paste-like silver particle composition that suppresses the deterioration of adhesive performance due to changes over time after the preparation of the silver particle composition and enables bonding treatment in a short time. In addition, the present invention provides a metal member joint using the paste-like silver particle composition and a method for producing the same. [Means for solving the problem]

[0009] In other words, the paste-like silver particle composition of the embodiment is a paste-like silver particle composition that melts upon heating at 200-260°C and adheres to a substrate, and has an average particle size of 2-5 μm. ru First, silver particles, and with an average particle size of 0.5~1μm ru Secondary silver particles, with an average particle size of 50nm to 300nm ru The material comprises third-order silver particles, a volatile dispersion medium, a diamine compound, and a fatty acid having 6 to 10 carbon atoms, wherein the diamine compound is present in an amount of 0.5 to 5% by weight of the total weight, the fatty acid is present in an amount of 0.5 to 2% by weight of the total weight, and the combined weight of the diamine compound and fatty acid is 2 to 5% by weight of the total weight.

[0010] Furthermore, the method for producing the paste-like silver particle composition of the embodiment has an average particle size of 2 to 5 μm. ru First, silver particles, and with an average particle size of 0.5~1μm ru Secondary silver particles, with an average particle size of 50nm to 300nm ru A method for producing a paste-like silver particle composition comprising third silver particles, a volatile dispersion medium, a diamine compound, and a fatty acid having 6 to 10 carbon atoms, wherein the composition melts upon heating at 200 to 260°C and is bonded to a substrate, wherein the diamine compound and The invention is characterized by comprising an additive preparation step of preparing an additive by mixing it with a fatty acid; a standing step of letting the additive stand at room temperature for 1 to 2 weeks; and a paste formation step of adding first silver particles, second silver particles, third silver particles, and a volatile dispersion medium to the standing additive and processing it into a paste.

[0011] In addition, the method for producing the paste-like silver particle composition of the embodiment has an average particle size of 2 to 5 μm. ru First, silver particles, and with an average particle size of 0.5~1μm ru Secondary silver particles, with an average particle size of 50nm to 300nm ruA method for producing a paste-like silver particle composition comprising third-order silver particles, a volatile dispersion medium, a diamine compound, and a fatty acid having 6 to 10 carbon atoms, which melts upon heating at 200 to 260°C and is bonded to a substrate, characterized by comprising: a primary preparation step of mixing the diamine compound, fatty acid, first-order silver particles, and second-order silver particles to prepare a primary mixture; a standing step of letting the primary mixture stand at room temperature for 1 to 2 weeks; and a secondary preparation step of adding third-order silver particles and a volatile dispersion medium to the standing primary mixture and processing it into a paste to prepare a secondary mixture. [Effects of the Invention]

[0012] The present invention provides a paste-like silver particle composition that melts upon heating at 200-260°C and adheres to a substrate, with an average particle size of 2-5 μm. ru First, silver particles, and with an average particle size of 0.5~1μm ru Secondary silver particles, with an average particle size of 50nm to 300nm ru A paste-like silver particle composition can be obtained that contains third-order silver particles, a volatile dispersion medium, a diamine compound, and a fatty acid having 6 to 10 carbon atoms, wherein the diamine compound is present in an amount of 0.5 to 5% by weight of the total weight, and the fatty acid is present in an amount of 0.5 to 2% by weight of the total weight, and the combined weight of the diamine compound and fatty acid is 2 to 5% by weight of the total weight. This allows for the suppression of deterioration in adhesive performance due to changes over time after the preparation of the silver particle composition, and enables short-time bonding treatment.

[0013] Furthermore, by employing a method for producing a paste-like silver particle composition, it becomes possible to suppress the deterioration of adhesive performance due to changes over time after the preparation of the silver particle composition, and to enable bonding treatment in a short time. In addition, it is useful as a metal component joint and a method for producing a metal component joint. [Brief explanation of the drawing]

[0014] [Figure 1] This is a spectral diagram of a gas chromatographic analysis of a single amine compound. [Figure 2] This is a spectral diagram of gas chromatography analysis of a mixture of amine compounds and fatty acids. [Figure 3] It is a graph of the heating conditions during the use of the paste-like silver particle composition.

Embodiments for Carrying Out the Invention

[0015] The paste-like silver particle composition of the embodiment contains silver particles with different average particle sizes and a filler, and is prepared into a paste form. The silver particles have an average particle size of 2 to 5 μm ru First silver particles, with an average particle size of 0.5 to 1 μm ru Second silver particles, with an average particle size of 50 nm to 300 nm ru They are roughly classified into three types of third silver particles. With only the first silver particles and the second silver particles, due to the coarseness of the particles, it takes time for sintering, and there are many voids after sintering. Also, with only the third silver particles, due to the fineness of the particles, it is easy to cause problems in coating performance due to a decrease in fluidity. Therefore, the third silver particles are blended for the purpose of filling the gaps between the first silver particles and the second silver particles. The blending ratio of the first silver particles, the second silver particles, and the third silver particles is approximately 2:1:1 in terms of weight ratio for the first silver particles, the second silver particles, and the third silver particles.

[0016] The average particle sizes of the first silver particles, the second silver particles, and the third silver particles are the volume-based integrated fraction 50% value of the particle size distribution measured using the laser diffraction scattering method for particle size distribution, specifically, using a laser diffraction scattering particle size distribution measuring device, that is, the median diameter (D50 value). When the laser diffraction scattering method for particle size distribution cannot be used, the simple average particle size or the median diameter D50 by electron microscope observation is adopted.

[0017] As components for binding the first silver particles, the second silver particles, and the third silver particles into a paste, a diamine compound and a fatty acid having 6 to 10 carbon atoms are blended. The fatty acid coats the surfaces of each of the first silver particles, the second silver particles, and the third silver particles. And the diamine compound causes a reaction such as an ester bond with heat between it and the fatty acid on the surface of each silver particle. It is considered that so-called cross-linking is formed. Then, with the diamine compound intervening, the first silver particles and the second silver particles attract each other, and the whole becomes a cohesive paste form.

[0018] The diamine compound is selected from compounds such as N,N-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-propanediamine, and N,N-dibutyl-1,3-propanediamine, as well as other diamine compounds. Furthermore, the diamine compound is selected from compounds with a boiling point of 150°C or higher, preferably 200°C or higher and 230°C or lower. From the viewpoint of storage resistance (minimal change over time) as a paste-like silver particle composition, a high boiling point is desirable. However, if the boiling point is extremely high, the molecular weight increases, reducing fluidity, and there is a risk of oxidative decomposition. In that case, N,N-diethyl-1,3-propanediamine and N,N-dibutyl-1,3-propanediamine are preferred as diamine compounds.

[0019] Although a wide variety of fatty acids are used, the number of carbon atoms is selected from those with 6 to 10 carbon atoms. Specifically, this includes straight-chain saturated fatty acids such as hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, and decanoic acid, as well as 2-ethylhexanoic acid, 2-methylhexanoic acid, and 3-methylhexanoic acid. The constraint on the number of carbon atoms is to balance liquidity at room temperature with suppressing an increase in the boiling point. In fatty acids, increasing the number of carbon atoms increases the melting point and boiling point. The paste-like silver particle composition becomes a bonding material when melted. Therefore, in the case of high-boiling-point fatty acids, the heating temperature for melting the paste-like silver particle composition needs to be high. This leads to problems such as thermal damage to electronic components and increased heating time. From the standpoint of controlling the boiling point, a constraint is placed on the number of carbon atoms.

[0020] In the embodiment of the paste-like silver particle composition, the diamine compound is present in an amount of 0.5 to 5% by weight of the total weight of the paste-like silver particle composition, and the fatty acid is present in an amount of 0.5 to 2% by weight of the total weight of the paste-like silver particle composition. If the amount of fatty acid is too low, the coating of the silver particles will not be sufficient, and if the amount of fatty acid is too high, it will take a long time for the fatty acid to evaporate during heating. If the amount of diamine compound is too low, crosslinking with the fatty acid will be insufficient, and the desired crosslinking effect will not be achieved. Furthermore, if the amount of diamine compound is too high, there is a risk of unreacted residue and deterioration over time. In addition, the total weight of the diamine compound and fatty acid is specified to be 2 to 5% by weight of the total weight. It is desirable that the amounts of both the diamine compound and fatty acid be equal. If it is less than 2% by weight of the total weight, the amount relative to the silver particles is insufficient. Also, if it is more than 5% by weight of the total weight, it is in excess and is likely to cause deformation.

[0021] In the embodiment of the paste-like silver particle composition, first silver particles, second silver particles, third silver particles, a diamine compound, and a fatty acid having 6 to 10 carbon atoms are essential. In addition to these, appropriate fillers are added as needed. In the embodiment, 3 to 5% by weight of texanol is added to the total weight of the paste-like silver particle composition. The fillers are added considering the adjustment of the viscosity and ease of coating of the paste-like silver particle composition.

[0022] As a volatile dispersion medium, water; volatile monohydric alcohols such as ethyl alcohol, propyl alcohol, butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, benzyl alcohol, cyclohexanol, terpineol; volatile polyhydric alcohols such as ethylene glycol, propylene glycol, hexanediol, octanediol; volatile aliphatic hydrocarbons such as lower n-paraffins and lower isoparaffins; volatile aromatic hydrocarbons such as toluene and xylene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, diacetone alcohol (4-Hydro) Examples include volatile ketones such as roxy-4-methyl-2-pentanone, 2-octanone, isophorone (3,5,5-trimethyl-2-cyclohexen-1-one), and dibutylketone (2,6-dimethyl-4-heptanone); volatile acetate esters such as ethyl acetate and butyl acetate; volatile aliphatic carboxylic acid esters such as methyl butyrate, methyl hexanoate, methyl octanoate, and methyl decanoate; volatile ethers such as tetrahydrofuran, methyl cellosolve, propylene brichol monomethyl ether, methyl methoxybutanol, and butyl carbitol; and low molecular weight volatile silicone oils and volatile organic modified silicone oils.

[0023] More than two types of volatile dispersion media may be used in combination, and the compatibility between the volatile dispersion media is not a concern. Furthermore, the paste-like silver particle composition of the embodiment only needs to be in paste form when used, and the volatile dispersion media may be solid at room temperature and may contain, for example, alcohols such as pyrogallol, p-methylbenzyl alcohol, o-methylbenzyl alcohol, sil-3,3,5-trimethylcyclohexanol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediol, and pinacol; hydrocarbons such as biphenyl, naphthalene, and durene; ketones such as dibenzoylmethane, chalcone, and acetylcyclohexane; and fatty acids such as lauric acid and capric acid. In this case, multiple volatile dispersion media with different melting points, boiling points, vapor pressure, viscosity, dielectric constant, refractive index, etc., may be used in combination. If the coating agent having polar groups that covers the surfaces of the first silver particles, second silver particles, and third silver particles is water-repellent, water can be avoided.

[0024] By preparing the paste-like silver particle composition according to the embodiment, as disclosed in the examples described later, the paste-like silver particle composition melts easily when joining metal members and becomes dense with few voids. Moreover, the type and blend of diamine compounds and fatty acids suppresses decomposition and modification over time. As a result, storage resistance is increased, and the performance and ease of use of the paste-like silver particle composition are improved.

[0025] Two methods for manufacturing the paste-like silver particle composition of the embodiment are presented. In the first manufacturing method, a diamine compound and a fatty acid are first mixed to prepare an additive ("additive preparation step"). The additive is left to stand at room temperature for 1 to 2 weeks ("standing step"). After standing, the additive is mixed with first silver particles, second silver particles, third silver particles, and a volatile dispersion medium to form a paste ("pasting step").

[0026] In the second manufacturing method, a primary mixture is first prepared by mixing a diamine compound, fatty acid, silver-1 particles, and silver-2 particles ("primary preparation step"). The primary mixture is left to stand at room temperature for 1 to 2 weeks ("standing step"). After standing, silver-3 particles and a volatile dispersion medium are added to the primary mixture and processed into a paste to prepare a secondary mixture ("secondary preparation step").

[0027] A key characteristic of each manufacturing method is that the reaction is moderately promoted by pre-mixing and standing of the diamine compound and fatty acid, thereby stabilizing the properties after the reaction. When comparing the first and second manufacturing methods, both exhibit roughly equivalent bonding strength (die shear strength (MPa)). The strength of the second manufacturing method is slightly higher.

[0028] In the first manufacturing method, the additive produced by mixing the diamine compound and fatty acid can be prepared in advance, and since silver particles are added at the end, the production quantity can be easily adjusted. In the second manufacturing method, the silver-1 particles, silver-2 particles, diamine compound, and fatty acid are mixed from the initial stage, making them easier to combine. In particular, the fatty acid coats the silver-1 and silver-2 particles and reacts with the diamine compound, thus increasing the adhesion of the silver-1 and silver-2 particles. The choice of each manufacturing method depends on the scale of production and demand. In any case, the key is not to mix all the raw materials at the same time, but to stabilize the properties by mixing the diamine compound and fatty acid and allowing them to stand. The necessary solvent is Texanol, etc., for viscosity adjustment.

[0029] The metal member joint of the embodiment is a member to be joined by a sintered product formed when the aforementioned paste-like silver particle composition is applied to a metal member, and then heated, causing the volatile components contained in the composition to volatilize, resulting in the fusion of the first silver particles, second silver particles, and third silver particles.

[0030] Examples of materials for the metal components include gold, silver, copper, platinum, palladium, nickel, tin, aluminum, and alloys of these metals. Of these, copper, silver, gold, platinum, palladium, or alloys of these metals are preferred in terms of conductivity and bonding reliability. The metal components may be plated with metal, and their base material is not limited. Examples of metal components include electronic components such as lead frames, printed circuit boards, semiconductor chips, and heat sinks, which are formed entirely or partially from metal. Therefore, the paste-like silver particle composition can be used for bonding electronic components to each other and to substrates, and its strong adhesive force makes it useful in the manufacture of electronic devices.

[0031] In the manufacturing method for a metal component joint, a paste-like silver particle composition is applied between the metal components. Then, it is heated in an atmospheric environment, in air, or in a low-oxygen concentration inert gas with an oxygen gas concentration of 2% by volume or less, at a temperature of 70°C to 300°C, and particularly at a temperature of 200°C to 260°C, taking into consideration the reduction of processing time and thermal damage.

[0032] If the metal component is made of a material that is easily oxidized when heated in an atmospheric environment, such as copper or a copper alloy, the oxygen gas concentration should be a low-oxygen inert gas with an oxygen gas concentration of 2 volume% or less, preferably 1 volume% or less, more preferably 0.5 volume% or less, and particularly preferably 0.1 volume% or less. The lower limit of the oxygen gas concentration is not limited, and it may not contain oxygen gas at all. Examples of inert gases include nitrogen gas and argon gas. A reducing gas that substantially does not contain oxygen gas and contains hydrogen gas may also be used. If the metal component is made of oxidation-resistant silver, gold, platinum, palladium, or an alloy of these metals, the atmosphere or air is preferred. The air may be ordinary air or dry air with reduced moisture content.

[0033] The paste-like silver particle composition used in the manufacturing method of metal component joints, after being coated onto the metal component, is heated to a temperature of 70°C to 300°C, particularly 200°C to 260°C, causing the volatile components contained therein to volatilize, the first and second silver particles to fuse together, and providing excellent conductivity and thermal conductivity, resulting in a strong bond between the metal components. Pressure and ultrasonic vibration may be applied during the heating of the paste-like silver particle composition. [Examples]

[0034] [Investigation of amine compounds and fatty acids] The current paste-like silver particle composition (reference composition) was prepared using the following formulation, and the die shear strength (MPa) was measured. The particle size is the average particle size. The values ​​are in weight percent. Particle size 2μm silver particles 46.6...1st silver particles Particle size 1μm silver particles 20.0…Second silver particles Particle size 200nm silver particles 28.5...Tertiary silver particles Texanol 5.0

[0035] [Shear bond strength (die shear strength)] A paste-like silver particle composition was printed onto a copper or silver substrate (both 99.99% pure) measuring 25 mm wide x 70 mm long and 1.0 mm thick using a 100 μm thick metal mask with four openings (2.5 mm x 2.5 mm) spaced 10 mm apart. A gold-plated silicon chip (gold purity 99.9% or higher) measuring 2.5 mm x 2.5 mm x 0.5 mm was placed on top of the silver, and the substrate and the gold-plated silicon chip were bonded together by heating in a forced-circulation oven for 1 hour to obtain a test specimen for measuring bonding strength.

[0036] The obtained test specimens for measuring joint strength were set in the test specimen holder of the adhesive strength tester, and the side of the gold-plated silicon tip was pressed with the pressing rod of the adhesive strength tester at a pressing speed of 23 mm / min. The load at which the joint broke under shear was used as the adhesive strength (in MPa). The average value of four test specimens was used as the shear adhesive strength (die shear strength). Subsequent measurements were performed in the same manner.

[0037] For the paste-like silver particle composition with the above reference composition, bonding was attempted by heating and melting under the following substrate and heating conditions, and the shear bond strength (die shear strength) (MPa) was measured.

[0038] Air atmosphere, 200°C heating, silver substrate, 75.3 Nitrogen atmosphere, heated at 250°C, silver substrate, 43.4 Nitrogen atmosphere, heated to 200°C, silver substrate, 26.5 Nitrogen atmosphere, heated to 200°C, copper substrate, 3.7

[0039] These results clearly showed a significant decrease in adhesion, particularly to copper substrates. Therefore, using a reference composition of paste-like silver particles as a baseline, amine compounds and fatty acids were added, and the shear adhesion strength (die shear strength) was measured. The results are shown in Table 1. In the table, Ag and Cu represent the metal species of the substrate, and the figures are in weight percent. Table 1 shows that paste-like silver particle compositions were prepared by adding one of the raw materials listed below according to the formulations shown in the table. (Raw materials used) C8: Octanoic acid (boiling point 237°C) C18: Oleic acid (boiling point 360°C) N8: Octylamine (boiling point 175°C) A5: N,N-dimethyl-1,3-propanediamine (boiling point 133°C) A7: N,N-diethyl-1,3-propanediamine (boiling point 169°C) A8: N,N-dibutyl-1,3-propanediamine (boiling point 205℃)

[0040] [Table 1]

[0041] From the results in Table 1, octanoic acid is preferred as the fatty acid, and diamine is preferred as the amine compound. Furthermore, N,N-diethyl-1,3-propanediamine and N,N-dibutyl-1,3-propanediamine are preferred based on their shear adhesion strength to the copper substrate. It was also found that the amount added is in the range of 1 to 5% by weight of the total weight of the paste-like silver particle composition. Based on these results, octanoic acid, which has 6 to 10 carbon atoms, was selected as the fatty acid, and N,N-dibutyl-1,3-propanediamine was selected as the amine compound, and these will be used for further verification. Table 2 shows the results of more detailed measurements of the added amounts. The firing conditions were 200°C for 1 hour under a nitrogen atmosphere.

[0042] [Table 2]

[0043] [Changes in components over time] As is clear from previous disclosures, diamine compounds are incorporated into the paste-like silver particle composition. However, it was found that the shear adhesion strength of the paste-like silver particle composition decreased to approximately 1 / 4 after 15 weeks compared to immediately after preparation. This is suspected to be due to changes in components during storage. Therefore, the changes in components of each paste-like silver particle composition at the time of preparation, after 17 weeks of refrigeration at 4°C, and after 12 weeks of freezing at -20°C were analyzed by gas chromatography (see Figure 1). In the gas chromatography analysis, 1 g of the paste-like silver particle composition was separated, dispersed in 1 g of acetone, and the components were extracted by centrifugation and loaded into the column.

[0044] As a result, peaks that were not initially present were observed in both refrigerated and frozen conditions (see Figure 1). This suggested the time-dependent degradation of the diamine compound. Therefore, in order to suppress the time-dependent changes and degradation of the diamine compound, the effect of adding a fatty acid to the diamine compound was evaluated. Octanoic acid was selected as the fatty acid based on the results of the shear adhesion strength mentioned above.

[0045] [Amine compounds and fatty acid cross-combinations] Five types of pastes were prepared by varying the proportion of amine compounds and fatty acids in the total weight of the paste-like silver particle composition, as shown in evaluation samples 1 to 5 below, and their shear bond strength (die shear strength) (MPa) was measured. Evaluation item 1 {A8-2.0% by weight}: Average 1.3 MPa Evaluation item 2 {A8-1.5 weight, C8-0.5 weight}: Average 27.4 MPa Evaluation item 3 {A8-1.0 weight, C8-1.0 weight}: Average 29.8 MPa Evaluation item 4 {A8-0.5 weight, C8-1.5 weight}: Average 21.2 MPa Evaluation item 5 {C8-2.0 weight}: Average 9.3 MPa

[0046] It was found that the combination of both amine compounds and fatty acids was extremely good. Based on the formulations of the evaluated products described above, a paste of evaluation product 6 {A8-1.3 wt%, C8-1.0 wt} was prepared, and the changes in its components over time were analyzed by gas chromatography (see Figure 2). The analysis was performed immediately after preparation and after 8 weeks at room temperature. In the gas chromatography analysis, 1 g of the paste-like silver particle composition was taken, dispersed in 1 g of acetone, and the components were extracted by centrifugation and loaded into the column. From Figure 2, it was found that with the combination of both amine compounds and fatty acids, no separate peaks appeared immediately after preparation and after 8 weeks, indicating that there was almost no change in the components.

[0047] [Assessment of Joint Reliability] Furthermore, in the process of selecting fatty acids, we found that substituting octanoic acid, which has the same number of carbon atoms, with 2-ethylhexanoic acid improved bonding reliability. Specifically, we newly prepared evaluation product 3{A8-1.0 wt%, C8-1.0 wt} and evaluation product 7{A8-1.0 wt%, 2-ethylhexanoic acid-}-1.0 wt% and subjected them to temperature cycling tests.

[0048] For the temperature cycling test, the chips were bonded to the copper substrate by preheating at 80°C for 10 minutes, followed by firing at 200°C for 1 hour under a nitrogen atmosphere. Subsequently, cooling and heating were repeated at -55°C for 15 minutes and 150°C for 15 minutes. This combination of cooling and heating constituted one cycle. As a result, evaluation sample 3 delaminated at 200 cycles. Evaluation sample 7 did not delaminate even after 600 cycles.

[0049] Based on these results, a new paste-like silver particle composition, evaluation sample 8, was prepared with the following formulation. The formulations are in weight percent. Particle size 2μm silver particles 46.6 Particle size 1μm silver particles 20.0 Particle size 200nm silver particles 28.5 Texanol 3.0 N,N-dibutyl-1,3-propanediamine 1.0 2-ethylhexanoic acid 1.0

[0050] For the paste-like silver particle composition of evaluation sample 8 prepared as described above, the shear bond strength (die shear strength) (MPa) was measured immediately after preparation and after 3 months at room temperature. In addition, the same temperature cycling test as described above was performed. As a result, the shear bond strength immediately after preparation was an average of 52.4 MPa, and ultrasonic testing at 0 cycles and 400 cycles was equivalent. The average shear bond strength after 3 months was 55.2 MPa, and ultrasonic testing results were comparable at 0 cycles and 400 cycles. Therefore, by combining diamine compounds with fatty acids, we were able to overcome the problem of changes over time (degradation of components).

[0051] [Consideration of the order of ingredients] Based on the series of events, the inventor considered revising the procedure for preparing the paste-like silver particle composition. In the aforementioned evaluation sample 8, the blending composition was weighed and then mixed all at once to form a paste. Therefore, while maintaining the same composition as evaluation sample 8, the blending procedure was modified as appropriate to prepare new evaluation samples. Subsequently, the shear bond strength (die shear strength) was measured for each evaluation sample. The shear bond strength was measured using the paste immediately after preparation.

[0052] The new evaluation items are items 9 through 12 listed below. Test sample 9: An amine compound, fatty acid, and silver-1 particles were mixed and left to stand at room temperature for one week. Then, silver-2 particles were added and kneaded. The average shear adhesive strength of test sample 9 was 71.3 MPa. Evaluation sample 10: An amine compound and a fatty acid were mixed and left to stand at room temperature for one week. Then, both first-order silver particles and second-order silver particles were added and kneaded. The average shear adhesive strength of evaluation sample 10 was 50.7 MPa. Test sample 11: An amine compound and a fatty acid were mixed and left to stand at room temperature for two weeks. Then, both silver-1 and silver-2 particles were added and kneaded. The average shear bond strength of test sample 11 was 49.8 MPa. Evaluation sample 12: An amine compound, fatty acid, and silver-1 particles were mixed and left to stand at room temperature for two weeks. Subsequently, silver-2 particles were added and kneaded. The average shear adhesive strength of evaluation sample 12 was 65.1 MPa.

[0053] From the results above, it was observed that evaluation samples 9 through 12 all showed improved shear adhesive strength (die shear strength) compared to evaluation sample 8, which was a simultaneous mixture of all components. In particular, the pastes of evaluation samples 9 and 12, in which the amine compound, fatty acid, and first silver particles were mixed beforehand, allowed to stand, and then the second silver particles were added, showed even greater shear adhesive strength.

[0054] Regarding the improvement in shear bond strength (die shear strength), it is presumed that the reaction between the amine compound and fatty acid is promoted in advance, the components are stabilized by allowing time to pass, and the addition of silver particles maintains a stable state.

[0055] [Consideration of processing time] Regarding the aforementioned Evaluator 8 paste-like silver particle composition, the bonding conditions with the substrate were changed, and the feasibility of bonding in a short time was evaluated. In this trial, the Evaluator 8 paste-like silver particle composition and a reference composition paste-like silver particle composition were printed onto a copper substrate (99.99% purity) measuring 25 mm wide x 70 mm long and 1.0 mm thick using a 100 μm thick metal mask with four openings (8.0 mm x 8.0 mm) spaced 10 mm apart. A gold-plated silicon chip (gold purity 99.9% or higher) measuring 8.0 mm x 8.0 mm x 0.5 mm was placed on top, and the substrate and the gold-plated silicon chip were bonded by heating in a forced-circulation oven.

[0056] The heating conditions were as shown in the graph in Figure 3. For evaluation sample 8 (heated at 250°C), the maximum temperature was 250°C, and heating was completed after approximately 50 minutes. For comparison, evaluation sample 8 (heated at 200°C) was set to a maximum temperature of 200°C, and heating was completed after approximately 70 minutes. The dashed line represents the heating state of the previous reference composition. The effect of increasing the size of the chip itself was particularly evaluated.

[0057] In the case of evaluation sample 8, even at the same temperature of 200°C as the reference composition, the time required to melt the silver particles is shortened. Furthermore, if the heating temperature is increased to 250°C, the overall heating time is further reduced. In particular, even if the maximum temperature increases, the duration at the maximum temperature is shortened, thus suppressing the effect of thermal damage to the substrate, chip, etc. Also, observation after bonding showed that even at higher temperatures, no bubbles were generated from the paste, and the finish was good. The amine compound, fatty acid, and solvent volatilize rapidly, making it possible to shorten the time. The same evaluation was also performed by preparing paste-like silver particle compositions using only the diamine compound or fatty acid. However, when either was used alone, the volatilization of the component was insufficient, resulting in a longer heating time compared to the combination of both the diamine compound and fatty acid in Comparative Example 8.

[0058] Considering the above points, when applying a paste-like silver particle composition to a substrate and heating it to melt it, the inclusion of both a diamine compound and a fatty acid is essential to shorten the heating time. Furthermore, the total weight of the diamine compound and fatty acid should be 2-5% by weight of the total weight of the paste to facilitate volatilization during heating. [Industrial applicability]

[0059] The paste-like silver particle composition of the present invention is useful for manufacturing metal component joints that can firmly bond multiple metal components and have excellent thermal shock resistance. The manufacturing method of metal component joints of the present invention is useful for manufacturing joints of chip components such as capacitors, resistors, diodes, memory, and computing elements (CPU, GPU) to substrates, as well as joints of heat dissipation components. Furthermore, the metal component joints of the present invention are useful for electronic components, electronic devices, electrical components, and electrical devices.

Claims

1. A paste-like silver particle composition that melts and adheres to a substrate when heated to 200-260°C, First silver particles with an average particle size of 2 to 5 μm, Secondary silver particles with an average particle size of 0.5 to 1 μm, Third-order silver particles with an average particle size of 50 nm to 300 nm, A volatile dispersion medium, Diamine compounds and, It has a fatty acid with 6 to 10 carbon atoms, The diamine compound is present in an amount of 0.5 to 5% by weight of the total weight. The aforementioned fatty acids are present in an amount of 0.5 to 2% by weight of the total weight. The total weight of the diamine compound and the fatty acid is 2 to 5% by weight of the total weight. A paste-like silver particle composition characterized by the following features.

2. The paste-like silver particle composition according to claim 1, wherein the diamine compound is selected from compounds having a boiling point of 200°C or higher.

3. The paste-like silver particle composition according to claim 2, wherein the diamine compound is selected from 2,2-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-propanediamine, 1,5-diamino-2-methylpentane, and N,N-dibutyl-1,3-propanediamine.

4. First silver particles with an average particle size of 2 to 5 μm, Secondary silver particles with an average particle size of 0.5 to 1 μm, Third-order silver particles with an average particle size of 50 nm to 300 nm, A volatile dispersion medium, Diamine compounds and, A method for producing a paste-like silver particle composition having a fatty acid with 6 to 10 carbon atoms, which melts upon heating at 200 to 260°C and is bonded to a substrate, An additive preparation step involves mixing the diamine compound and the fatty acid to prepare an additive, A standing step in which the aforementioned additive is left to stand at room temperature for 1 to 2 weeks, The process includes a paste-forming step in which the first silver particles, second silver particles, third silver particles, and the volatile dispersion medium are added to the additive after it has been allowed to stand, and processed into a paste. A method for producing a paste-like silver particle composition characterized by the following:

5. First silver particles with an average particle size of 2 to 5 μm, Secondary silver particles with an average particle size of 0.5 to 1 μm, Third-order silver particles with an average particle size of 50 nm to 300 nm, A volatile dispersion medium, Diamine compounds and, A method for producing a paste-like silver particle composition having a fatty acid with 6 to 10 carbon atoms, which melts upon heating at 200 to 260°C and is bonded to a substrate, A primary preparation step involves mixing the diamine compound, the fatty acid, the first silver particles, and the second silver particles to prepare a primary mixture. A standing step is to leave the primary mixture standing at room temperature for 1 to 2 weeks. The system includes a secondary preparation step of adding the third silver particles and the volatile dispersion medium to the primary mixture after it has been allowed to stand, and processing it into a paste to prepare a secondary mixture. A method for producing a paste-like silver particle composition characterized by the following:

6. The method for producing a paste-like silver particle composition according to claim 4 or 5, wherein the diamine compound is selected from compounds having a boiling point of 200°C or higher.

7. The method for producing a paste-like silver particle composition according to claim 6, wherein the diamine compound is selected from 2,2-dimethyl-1,3-propanediamine, N,N-diethyl-1,3-propanediamine, 1,5-diamino-2-methylpentane, and N,N-dibutyl-1,3-propanediamine.

8. A metal member assembly characterized by comprising the paste-like silver particle composition described in claim 1 and a metal member.

9. The metal member assembly according to claim 8, wherein the metal member is an electronic component having a metal substrate and a metal portion.

10. The paste-like silver particle composition described in claim 1 is applied between the metal members, A method for manufacturing a metal component assembly, characterized by heating at 200 to 260°C in an atmospheric environment, air, or a low-oxygen concentration inert gas with an oxygen gas concentration of 2% by volume or less.

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