Metal-resin bonded body and its manufacturing method

Abstract

To provide a highly reliable joint having a metal fine particle sintered body layer, a resin layer and a base material; and to provide a production method of the joint.SOLUTION: In a joint, which is a joint having a base material, a resin layer comprising a resin, formed on the base material, and a metal layer comprising a metal fine particle sintered body, formed on the resin layer, metal particles are inherent in the resin later, and at least a part of the inherent metal particles is sintered with the metal fine particle sintered body.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a bonded body including a sintered layer made of metal fine particles formed of gold, silver, palladium, etc., a resin layer made of resin, and a substrate. The present invention also relates to a method for producing such a bonded body. [Background technology]

[0002] In recent years, a bonded body consisting of a metal fine particle sintered body layer made of metal fine particles and a resin layer made of resin has been developed for various applications. For example, Patent Document 1 below describes that a bonded body consisting of a copper fine particle sintered body layer and a polyimide film is used as a substrate for printed wiring boards for small electrical devices, etc. Such a bonded body is produced by alkali-treating one surface of a polyimide film, applying a conductive ink containing copper fine particles to that surface to form a coating film, drying the coating film, and then firing it. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-114680 Summary of the Invention [Problem to be solved by the invention]

[0004] As mentioned above, the technology described in Patent Document 1 uses copper microparticles. However, currently, there is a demand for bonded bodies having a metal microparticle sintered body layer made of not only copper but also precious metals such as gold and silver. However, with the technology described in Patent Document 1, bonding with the resin is maintained by metal oxides and metal oxide-derived groups, so it seems difficult to obtain bonded bodies with high bonding strength having sintered body layers made of various metals, including precious metals. In addition, low-temperature sintered metal microparticles that can be sintered below the heat-resistant temperature of the resin have high sinterability, and sintering between the microparticles progresses early in the sintering process, resulting in a loss of reactivity and bonding with the resin layer, making it difficult to achieve highly reliable bonded bodies.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a highly reliable joined body including a metal microparticle sintered body layer, a resin layer, and a substrate. Another object of the present invention is to provide a method for manufacturing the joined body disclosed herein. [Means for solving the problem]

[0006] According to the present invention, there is provided a bonded body comprising a substrate, a resin layer made of resin formed on the substrate, and a metal layer made of metal microparticle sintered body (i.e., a metal microparticle sintered body layer) formed on the resin layer. The resin layer contains metal particles, and at least some of the contained metal particles are sintered with the metal microparticles. In a bonded body having such a configuration, high bonding strength can be achieved by sintering the contained metal particles with the metal microparticles. In this specification and claims, the term "metal microparticles" refers to a group of many microparticles (i.e., particles), unless it specifically refers to a single particle. For example, the metal microparticles in the "metal microparticle dispersion" described below refer to metal microparticles as particles, not individual particles. In Japanese, it is unclear whether to use the singular or plural term, so the above definition is used to clarify the meaning of "metal microparticles."

[0007] In a preferred embodiment of the bonded body disclosed herein, micropores are present at the interface between the metal layer and the resin layer, facing the inside of the resin layer. The metal microparticle sintered body penetrates at least some of the micropores, and when the opening diameter of the micropore in an FE-SEM cross-sectional image of the interface is a and the penetration distance of the metal microparticle sintered body into the micropore is b', there are some micropores where the opening diameter a is 1 μm or more and 10 μm or less, and the distance b' is 2 μm or more. In a bonded body having such a configuration, the metal microparticle sintered body in the micropores fulfills the so-called anchor effect, thereby achieving high bonding strength.

[0008] More preferably, in an FE-SEM cross-sectional image of the boundary surface, when 100 or more micropores having an opening diameter a of 1 μm or more and a distance b of 2 μm or more are detected (randomly detected), where b is the distance from the center of the opening diameter a to the deepest part of the micropore, 60% or more of the micropores have a distance b' of 2 μm or more. In a bonded body having such a configuration, the anchor effect is more suitably exerted, thereby achieving higher bonding strength.

[0009] More preferably, when the b' / a ratio, which is the ratio of the opening diameter a to the distance b', is calculated for each of the micropores that account for 60% or more of the micropores, the average value of the b' / a ratio is 1.3 or more. The micropores of this configuration are long and thin, and the metal microparticle sintered body can easily penetrate deeper, thereby more suitably realizing the anchoring effect. The b / a ratio is more preferably 1.5 or more, even more preferably 2.0 or more, and particularly preferably 2.5 or more.

[0010] In a preferred embodiment, ten FE-SEM cross-sectional images (10 μm x 10 μm) of the boundary surface between the metal layer and the resin layer are prepared (randomly), and the boundary line between the metal layer and the resin layer is measured (randomly) over 5 μm in each cross-sectional image. The total distance of the gap between the metal layer and the resin layer at the boundary line is 1 μm or more. With this structure, bonding is achieved mainly by sintering the metal fine particles and the embedded metal particles, resulting in high bonding strength. Furthermore, the presence of gaps favorably relieves thermal stress.

[0011] In a preferred embodiment of the bonded body disclosed herein, the main constituent metal element of the metal fine particles that make up the metal fine particle sintered body is a noble metal element. Noble metal fine particles are suitable for application of the technology disclosed herein because the fine particles tend to sinter together.

[0012] In a preferred embodiment, the main constituent metal element of the metal fine particles that make up the metal fine particle sintered body is gold (Au). Among noble metal fine particles, gold fine particles in particular are suitable for application of the technology disclosed herein because the fine particles tend to sinter together.

[0013] In a preferred embodiment of the bonded body disclosed herein, the resin is a thermosetting resin. The thermosetting resin allows the technology disclosed herein to be suitably implemented.

[0014] In a preferred embodiment, the resin is a thermosetting epoxy resin. Among thermosetting resins, epoxy resins in particular have high heat resistance, and therefore can provide highly reliable bonded bodies.

[0015] In a preferred embodiment of the bonded body disclosed herein, the metal layer has a density of 80% or more. When the metal layer has a high density as described above, a bonded body having a low volume resistivity and good electrical conductivity can be obtained. Details of the "density" in this specification and claims will be described in detail in <Density of Metal Layer>.

[0016] The present invention also provides a method for producing the bonded structure disclosed herein. Specifically, the method includes a substrate, a resin layer formed on the substrate, and a metal layer formed on the resin layer, the metal layer being made of metal fine particles and having an imine compound supported on its surface. The method includes preparing a dispersion containing the metal fine particles, applying the dispersion to the surface of the resin layer formed on the substrate (wherein the resin layer contains metal particles), and heating the resin substrate to which the dispersion has been applied within a temperature range in which the metal fine particles can be sintered, thereby forming the metal layer. This bonded structure production method allows for the production of a highly reliable bonded structure having the desired strength. In this specification and claims, the term "dispersion" refers to a dispersion of metal fine particles, embedded metal particles, resin, etc. in a solvent, and may also include paste-like compositions, slurry-like compositions, ink-like compositions, paints, etc.

[0017] In a preferred embodiment of the method for producing a conjugate disclosed herein, the imine compound has the following structural formula: R 0 R 1 C=N-(CH2)-R 2 where R 0 is hydrogen and R 1 and R 2 are hydrocarbon groups having 3 to 7 carbon atoms. Such imine compounds (e.g., alkylimines) having a relatively low molecular weight and a short hydrocarbon group can be easily removed by low-temperature firing at 300°C or less, and therefore, a bonded body having a highly dense metal layer can be easily produced. [Brief explanation of the drawings]

[0018] [Figure 1] 1 shows a pyrolysis GCMS spectrum obtained for a gold fine particle powder material produced in an example described later. [Figure 2] This is the MS spectrum of the peak (■) of the imine compound in FIG. [Figure 3] 1 is an FE-SEM observation image (50,000 magnifications) of a gold fine particle powder material produced in an example described later. [Figure 4] 10 is an FE-SEM observation image (5,000 magnifications) of the interface between a gold fine particle sintered body layer and a gold particle-containing thermosetting epoxy resin layer according to Example 2. [Figure 5] 10 is an FE-SEM observation image (20,000 magnifications) of the interface between a gold fine particle sintered body layer and a gold particle-containing thermosetting epoxy resin layer according to Example 2. [Figure 6] 1 is an FE-SEM observation image (magnification: 5,000) of the interface between a gold fine particle sintered body layer and a gold particle-containing thermosetting epoxy resin layer according to Comparative Example 1. [Figure 7] 1 is an FE-SEM observation image (20,000 magnifications) of the interface between a gold fine particle sintered body layer and a gold particle-containing thermosetting epoxy resin layer according to Comparative Example 1. [Figure 8] 10 is an FE-SEM observation image (5,000 magnifications) of the interface between a gold fine particle sintered body layer and a gold particle-containing thermosetting epoxy resin layer according to Comparative Example 2. [Figure 9] 10 is an FE-SEM observation image (20,000 magnifications) of the interface between a gold fine particle sintered body layer and a gold particle-containing thermosetting epoxy resin layer according to Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0019] Preferred embodiments of the present invention will be described below. It should be noted that matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood as design matters for a person skilled in the art based on the prior art in the relevant field. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. In this specification and claims, when a predetermined numerical range is described as A to B (A and B are arbitrary numerical values), it means A or more and B or less. Therefore, it includes the case where the range is above A and below B.

[0020] <Metal fine particles> The metal fine particles used in the bonded structure and the method for manufacturing the bonded structure disclosed herein are not particularly limited as long as the effects of the present invention can be obtained. Typical examples include gold (Au), silver (Ag), palladium (Pd), platinum (Pt), rhodium (Rh), and alloys thereof. Furthermore, from the viewpoint of being suitable as a target for applying the technology disclosed herein, it is preferable that the main constituent metal element is gold (Au). Here, the term "main constituent metal element" refers to the metal element that constitutes the main constituent of the metal microparticles. The metal microparticles disclosed herein are ideally composed only of metal elements, but may also contain various metal elements and non-metal elements as impurities. The organic matter content of the total weight (100 wt%) of the metal microparticles (referring to the aggregate before calcination) measured based on TG-DTA is preferably approximately 2 wt% or less, more preferably 1.5 wt% or less, and particularly preferably 1 wt% or less.

[0021] The method for producing a bonded body disclosed herein is characterized in that an imine compound is held on the surfaces of the metal fine particles. By holding the imine compound on the surfaces of the metal fine particles, high dispersion stability can be obtained. Methods for producing such metal microparticles include, as in the reaction system described in the Examples below, a method in which a mixture of a metal salt or metal complex (e.g., chloroauric acid (HAuCl4) when the metal is gold) that is soluble in a specific alcohol-based solvent and serves as the raw material for the metal microparticles is prepared, a sufficient amount of alkylamine (e.g., 3 molar equivalents or more) relative to the metal, and an alcohol-based solvent that can dissolve the raw material, such as an alkyl alcohol, is prepared, and the mixture is heated to, for example, 80°C or higher. This reduces metal ions from the metal salt or complex, producing metal microparticles. The reduction treatment time for the metal ions can be set appropriately and is not particularly limited, but is preferably, for example, about 0.5 to 5 hours. The metal microparticles produced by the reduction treatment described above can be recovered in the same manner as conventional metal particle recovery, and there are no particular limitations. Preferably, the metal microparticles produced in the liquid are allowed to settle, and the supernatant is removed by centrifugation. Preferably, washing and centrifugation are repeated multiple times with an appropriate dispersion medium, and the metal microparticles are dispersed in the appropriate dispersion medium, thereby obtaining a desired dispersion of metal microparticles. Furthermore, by adding components such as a binder, a paste (slurry) composition (e.g., a conductor paste for forming an electrode film, etc.) can be prepared.

[0022] Preferably, the imine compound produced in the reaction system and held on the surface of the metal fine particles has a relatively small molecular weight, specifically, an alkylimine having a hydrocarbon group with about 10 or less carbon atoms, for example, 4 to 10 carbon atoms, such as an alkylimine represented by the structural formula: R 0 R 1 C=N-(CH2)-R 2 It is a compound represented by R 0 , R 1 and R 2 are each independently a partially substituted or unsubstituted alkyl group or hydrogen. 0 is hydrogen and R 1 and R 2 and each are a hydrocarbon group having 3 to 9 carbon atoms (more preferably 3 to 7). Such imine compounds (e.g., alkylimines) having a relatively low molecular weight and short hydrocarbon group can be easily eliminated by low-temperature firing at 300°C or less, making it possible to easily produce a bonded body having a dense metal layer. For example, an imine compound of the above structural formula, R 0 is hydrogen and R 1 and R 2 are preferably CH3(CH2)6, CH3(CH2)4 or CH3(CH2)2, respectively.

[0023] This type of imine compound having a relatively small molecular weight and a short chain length can be selectively (preferentially) produced by selecting the alcohol solvent and primary amine used in the reaction system. For example, when octanol (CH3(CH2)7OH) is used as the alcohol solvent and octylamine (CH3(CH2)7NH2) is used as the primary amine, the imine compound produced has the structure shown above. 0 is hydrogen and R 1 and R 2 Alternatively, if the primary amine in this reaction system is replaced with butylamine (CH(CH)NH), the resulting imine compound will have the structure shown above, where R 0 is hydrogen and R 1 and R 2 Alternatively, in this reaction system, when the primary amine is replaced with hexylamine (CH(CH)NH), the resulting imine compound has the structure shown above. 0 is hydrogen and R 1 and R 2 At least one of the groups may be CH3(CH2)4. Thus, in the above reaction system, the molecular weight of the imine compound to be produced (in other words, R 0 , R 1 , R 2 The composition of the material can be varied as appropriate. As will be apparent from the examples described later, the structure of the imine compound produced can be identified by measuring the pyrolysis GCMS spectrum.

[0024] Regarding the particle size distribution of the metal microparticles, the ratio of the Z-average particle size (DDLS) based on dynamic light scattering (DLS) to the average particle size (DSEM) based on field emission scanning electron microscope (FE-SEM) images, DDLS / DSEM, is preferably 2 or less. Metal microparticles with such characteristics have particularly excellent dispersibility, and can contribute to the miniaturization of electronic components and the thinning of electrodes in the electronic materials field. Furthermore, metal microparticles with a relatively small average particle size, such as a Z-average particle size (DDLS) of 200 nm or less, can further promote the thinning of electrodes and the improvement of their reliability. The DDLS is more preferably 150 nm or less, and is particularly preferably, for example, 50 nm to 150 nm.

[0025] <Metal fine particle dispersion> The metal fine particle dispersion in the bonded body manufacturing method disclosed herein can be obtained by dispersing the above metal fine particles in a dispersion medium made of an appropriate aqueous solvent or organic solvent. For example, a paste-like composition (conductor paste) can be prepared by dispersing metal fine particles in a predetermined organic solvent and then adding components such as a binder, a conductive material, a viscosity modifier, etc. As described above, such a conductor paste contains metal fine particles whose Z-average particle size is controlled to the submicron range, and therefore can be used to suitably form a sufficiently thin electrode. The dispersion medium for the conductor paste may be any one that can disperse the conductive powder material well, as in the past, and any one that has been used in the preparation of conventional conductor pastes can be used without any particular limitation. For example, as the organic solvent, one or a combination of petroleum hydrocarbons (especially aliphatic hydrocarbons) such as mineral spirits, cellulose polymers such as ethyl cellulose, ethylene glycol and diethylene glycol derivatives, high-boiling organic solvents such as toluene, xylene, butyl carbitol (BC), and terpineol can be used.

[0026] A suitable dispersion medium for preparing the metal fine particle dispersion is a cyclic alcohol having a hydroxyl group on the cyclic chain. High dispersion stability can be achieved by including a cyclic alcohol as the dispersion medium. Suitable examples include cyclic alcohols having a 5- to 8-membered ring. Examples include terpineol, menthanol (dihydroterpineol), menthol (2-isopropyl-5-methylcyclohexanol), cyclopentanol, cyclohexanol, and cycloheptanol. These cyclic alcohols may be used alone or in combination of two or more. There are no particular limitations on the content of the cyclic alcohol, but it is appropriate for it to be 10 to 100% by mass, and preferably 70 to 100% by mass, of the entire dispersion medium.

[0027] <Resin> The resins used in the bonded structure and the method for producing the bonded structure disclosed herein are not particularly limited as long as the effects of the present invention can be obtained. However, from the viewpoint of obtaining a highly reliable bonded structure, resins with a high glass transition temperature (Tg) are preferably used. Specific examples include thermosetting polyimide resins and thermosetting epoxy resins. The Tg of the thermosetting epoxy resins that can be used in the present invention is typically 100 to 150°C.

[0028] <Internal metal particles> The resin is characterized by containing metal particles (hereinafter, such metal particles are also referred to as "internal metal particles"). The internal metal particles are sintered with the metal microparticle sintered body that constitutes the metal layer, thereby suitably improving the strength of the resulting bonded body. The internal metal particles are not particularly limited as long as the effects of the present invention can be obtained, but those listed in the description of the metal fine particles above can be suitably used. In addition, gold particles can be preferably used from the viewpoint of high sinterability and ease of sintering with the metal fine particle sintered body that constitutes the metal layer.

[0029] <Base material> The substrate in the bonded body and the method for manufacturing the bonded body disclosed herein is not particularly limited as long as the effects of the present invention can be obtained. For example, substrates made of tungsten, silicon, glass, various metal materials, resin materials, etc. are preferably used.

[0030] <Density of metal layer> In this specification and claims, "density" refers to the value obtained by determining the area of ​​black voids (i.e., hollow areas) in a 10,000x FE-SEM cross-sectional image of an object (e.g., a metal layer) using image analysis software "Image Pro" manufactured by Media Cybernetics, and calculating density (%) = 1 - (void area / total area)%. A metal layer with high density can have low volume resistivity and good conductivity. The density is preferably 80% or more, more preferably 85% or more, even more preferably 90% or more, and particularly preferably 95% or more (the upper limit of the density is 100%).

[0031] <Micropore> In this specification and claims, a, b, and b' are used as parameters representing the shape of the micropores. a can also refer to the opening diameter of the micropore in an FE-SEM cross-sectional image of the interface between the metal layer and the resin layer, or the distance between the metal particles present in the opening of the resin at the interface (i.e., between the embedded metal particles) (see Figure 4, etc.). b can also refer to the distance from the center of the opening diameter a to the deepest part of the micropore, or the length of a line segment connecting the center of the opening of the micropore, passing through the metal microparticle sintered body in the opening, to the deepest part of the opening. If the shape inside the opening is complex and a single line segment cannot represent the length to the deepest part, an additional line segment is added, and the sum of these line segments is taken as b. b' is the distance from the center of the opening diameter a to the deepest part of the micropore into which the metal microparticle sintered body has penetrated (see Figure 4, etc.). As with b, if the shape inside the opening is complex and a single line segment cannot represent the length up to the portion where the metal sintered body has entered, another line segment is added, and the sum of these line segments is b'. Preferably, the value of a is 1 μm to 10 μm, and the value of b' is 2 μm to 10 μm. Alternatively, a may be 1 μm to 3 μm, and b' may be 2 μm or more, or a may be 1 μm to 3 μm, and b' may be 3 μm or more, or a may be 1 μm to 2 μm, and b' may be 4 μm or more.

[0032] As an example of the bonded structure disclosed herein, an example of a bonded structure of a gold fine particle sintered body layer, a gold particle-containing thermosetting epoxy resin layer, and a substrate will be described below, but such an example is not intended to limit the present invention.

[0033] <1. Example of manufacturing gold nanoparticles> 50 mL of octanol (Fujifilm Wako Pure Chemical Industries, Ltd.) was added to 20.5 g of chloroauric acid tetrahydrate (Inuisho Precious Metals Chemical Co., Ltd.), and the resulting solution was cooled and stirred in an ice bath. Next, n-octylamine (a product of Fujifilm Wako Pure Chemical Industries, Ltd.) was added little by little to the above solution while suppressing heat generation, in an amount equivalent to 10 molar equivalents of the gold content, to prepare a chloroauric acid-octylamine complex-forming solution. This complex-forming solution was subjected to a reduction treatment by heating it in an oil bath at 140°C in an air atmosphere for 3 hours while stirring, reducing the gold ions and synthesizing gold microparticles. The reaction mixture was then allowed to cool naturally, industrial alcohol (a product of Amakasu Chemical Industry Co., Ltd.) was added, the gold particles were allowed to settle, and the supernatant was removed by decantation. This procedure was repeated three times, after which industrial alcohol was added and the mixture was centrifuged at 3000 rpm for three minutes two or more times (three times in this case) and the supernatant was removed. The mixture was then dried at room temperature for 12 hours to obtain a dry powder material consisting of gold particles.

[0034] <2. Evaluation test of gold nanoparticles> (1) Characteristics of gold nanoparticles The gold microparticles in the powder material were observed using a field emission scanning electron microscope (FE-SEM: Hitachi High-Technologies Corporation, S-4700) (see Figure 3). Specifically, five images were randomly selected from either a 100,000x or 50,000x field of view, and the particle sizes of 40 individual particles were measured. The average particle size (DSEM) was calculated from the particle sizes of a total of 200 particles. The results are shown in the relevant columns in Table 1.

[0035] Furthermore, for the above powder materials, samples of appropriate concentration were prepared by ultrasonic dispersion using a Zetasizer Nano ZS (product of Malvern Panalytical) with N,N-dimethylformamide (DMF) as the dispersion medium, and DLS measurements were performed at 20°C. The Z-average particle size (DDLS) was calculated based on the general cumulant method. The results are shown in the corresponding columns in Table 1.

[0036] Furthermore, a thermal analysis of the gold microparticles (dry powder material) was performed on the powder material using a thermogravimetric analyzer (Rigaku Corporation, TG-DTA / H). Specifically, approximately 20 mg of the powder material was heated from room temperature to 400°C at a rate of 10°C / min, and the thermal behavior was observed after holding at 400°C for 50 minutes. The weight loss rate at this time was taken as the organic matter content relative to the total weight (100 wt%) of the gold microparticles (dry powder). The results are shown in the relevant columns in Table 1.

[0037] (2) Detection of imine compounds The powder material was analyzed using a pyrolysis GCMS device (GCMS-QP2010 Ultra, manufactured by Shimadzu Corporation). Specifically, approximately 20 mg of dry gold particle powder was heated to 300°C for 18 seconds to cause pyrolysis, and the gas components evolved from the sample were measured using GCMS. The column used was a Frontier Labs Ultra ALLOY±5 (UA5-30M-0.25F), and the column oven temperature was raised from 40°C to 320°C at a rate of 10°C / min and held at 320°C for 32 minutes. The ionization method used for the mass spectrometer was electron impact (EI). The obtained pyrolysis GCMS spectrum is shown in Figure 1. Furthermore, the MS spectrum of the detected peak of the imine compound (peak ■ in the corresponding pyrolysis GCMS spectrum) is shown in Figure 2.

[0038] The imine compounds identified were as follows: [Imine compounds] Structural formula: R 0 R 1 C=N-(CH2)-R 2 An imine compound represented by the formula: 0 is hydrogen and R 1 and R 2 are CH3(CH2)6, respectively. Hereinafter, this will be referred to as imine compound A. Identification method Since the MS spectrum data of the above imine compound was not present in the GCMS library, the imine compound (R 0is hydrogen, and the above R 1 and R 2 The compounds were identified by referring to the MS spectrum data of the imine compounds (where each is CH3(CH2)2).

[0039] [Table 1]

[0040] As shown in Table 1, the gold microparticles in the powder material had a DDLS / DSEM of 2 or less, confirming their good dispersibility. Furthermore, the Z-average particle size (DDLS) was 150 nm or less, confirming that this is a good powder material that contributes to the miniaturization of electronic components and the thinning of electrodes. Furthermore, when the total weight of the gold microparticles (dry powder) was taken as 100 wt%, the organic matter content (here, the content of imine compounds present on the surface of the gold microparticles) was 0.61 wt%. Therefore, since the amount of imine compounds adsorbed to the surface of the gold microparticles was small, it is thought that the volume change due to burn-through during sintering was small, resulting in a highly dense sintered body. Furthermore, as shown in the relevant column in Table 1, the large exothermic peak (due to oxidation) above 200°C observed in gold microparticles carrying alkylamines was not detected in the TG-DTA of the powder material (TG-DTA curve not shown). Furthermore, pyrolysis GCMS at 300°C confirmed that the main component was an imine compound (alkylimine compound: see the structural formula above). This indicates that the organic molecules present on the surface of the gold microparticles were converted from alkylamines to the alkylimine compounds in the reaction system in which the gold microparticles were synthesized, and that almost no amine added to the reaction system remained.

[0041] <3. Example of manufacturing gold particle dispersion> Menthol, a cyclic alcohol, was added to the powder material as a dispersion medium, and the mixture was left to stand for at least 3 hours. After that, the mixture was centrifuged to replace the solvent. Menthol was added to the obtained wet powder so that the weight of the gold particles was 80 to 90 wt % of the total amount, and the mixture was mixed and dispersed using a planetary mixer to prepare a gold particle dispersion.

[0042] <4. Example of manufacturing gold particle-containing thermosetting epoxy resin paint> A thermosetting epoxy resin containing gold particles was prepared by dissolving the thermosetting epoxy resin in terpineol C and kneading it with gold particles and a novolac phenolic resin curing agent (in the following description, this type of paint will also be referred to simply as "epoxy resin paint").

[0043] <5. Production Example of Bonded Body Comprising a Gold Fine Particle Sintered Body Layer, a Gold Particle-Containing Thermosetting Epoxy Resin Layer, and a Substrate> Example 1: The epoxy resin coating was applied to a tungsten substrate, dried at 130°C for 15 minutes, and then treated at 180°C for 1 hour to harden the epoxy resin. At this time, the gold particle-containing thermosetting epoxy resin layer (hereinafter simply referred to as the "epoxy resin layer") formed was in a state bonded to the tungsten substrate. The gold particle dispersion was applied to the surface of the epoxy resin layer, dried at 60°C for 1 hour, and then heated at a rate of 10°C / min and heat-treated at 250°C for 30 minutes to perform sintering. As a result, a bonded body consisting of a tungsten-epoxy resin layer-gold particle sintered body layer (the "bonded body" in the following description refers to such a bonded body) was obtained. Example 2: The same procedure as in Example 1 was carried out, except that the gold particle dispersion was applied to the surface of the epoxy resin layer, dried, and then heat-treated at 280°C for 50 minutes with a temperature increase rate of 10°C / min. As a result, a bonded body was obtained. Example 3: The same procedure as in Example 1 was carried out, except that the gold particle dispersion was applied to the surface of the epoxy resin layer, dried, and then heat-treated at 300°C for 30 minutes at a temperature increase rate of 10°C / min. As a result, a bonded body was obtained.

[0044] Comparative Example 1: The same procedure as in Example 2 was carried out, except that the epoxy resin coating was dried at 130°C for 15 minutes and then not subjected to a heat curing treatment. Here, the epoxy resin was cured in the heat treatment step of the gold microparticle dispersion. As a result, a bonded body was obtained, but in the tape peeling test described below, part of the epoxy resin layer peeled off from the tungsten substrate. Figure 6 is an FE-SEM cross-sectional image of a part of the bonded body where peeling did not occur. Comparative Example 2: The same procedure as in Example 2 was carried out, except that the epoxy resin coating was dried at 60°C for 1 hour and then not subjected to a heat curing treatment. The epoxy resin was cured during the heat treatment of the gold particle dispersion. As a result, some of the gold particle dispersion peeled off from the tungsten substrate during the drying process, and the peeling continued during the subsequent heat treatment process. Figure 8 shows an FE-SEM cross-sectional image of a portion of the bonded assembly where no peeling occurred. Here, as is clear from Figures 6 and 8, the peeling in Comparative Examples 1 and 2 is thought to have occurred because the sintering between the gold microparticle sintered body and the gold particles in the epoxy resin did not progress as much as in the other examples.

[0045] <6. Example of manufacturing a thermoplastic polyimide resin paint containing gold particles> A thermoplastic polyimide resin coating material containing gold particles was prepared by dissolving the thermoplastic polyimide resin in γ-butyrolactone and kneading the material with gold particles (in the following description, this coating material will also be referred to simply as “polyimide resin coating material”).

[0046] Comparative Example 3: The polyimide resin coating was applied to a tungsten substrate, dried at 130°C for 15 minutes, then at 180°C for 30 minutes, and then heated at a rate of 10°C / min to 280°C for 50 minutes to solidify (to completely remove the solvent). The gold microparticle dispersion was applied to the surface of the solidified polyimide resin molded body, dried at 60°C for 1 hour, heated at a rate of 10°C / min, and then heat-treated at 250°C for 30 minutes to sinter. As a result, the gold microparticle sintered body layer was not bonded to the gold particle-containing thermoplastic polyimide resin layer, and formed a separate film.

[0047] <7. Direct formation of a sintered gold particle layer on a substrate> Comparative Example 4: The gold particle dispersion was applied to a glass substrate using a 1cm x 1cm x 100µm metal mask and squeezed with a rubber squeegee. After drying at 60°C for 1 hour, the coating was heat-treated at 300°C for 30 minutes. The resulting gold particle sintered layer was a separate film, not adhering to the glass substrate. Comparative Example 5: Except for applying the gold fine particle dispersion onto a tungsten substrate, the same operation as in Comparative Example 4 was carried out. As a result, the obtained gold fine particle sintered body layer did not adhere to the tungsten substrate and was a single film. Comparative Example 6: The same procedure as in Comparative Example 4 was carried out, except that the gold fine particle dispersion was applied onto a gold substrate. As a result, the obtained gold fine particle sintered body layer did not adhere to the gold substrate and was a single film.

[0048] <8. Evaluation test of the conjugate> [Tape peeling test] A peel test was carried out by attaching and peeling off cellophane tape to the bonded structures obtained in Examples 1 to 3. The test results are shown in the corresponding columns in Table 2.

[0049] [Evaluation of the density of sintered gold particle layers] The cross sections of the bonded bodies obtained in Examples 1 to 3 were subjected to ion milling. Then, from the FE-SEM cross-sectional images of each of the obtained ion-milled polished surfaces at 10,000 magnifications, the area of ​​the black voids (i.e., hollow portions) was determined using image analysis software "Image Pro" manufactured by Media Cybernetics, and the compactness (%) was calculated as 1 - (void area / total area)%. The results are shown in the corresponding columns in Table 2.

[0050] [Table 2]

[0051] [Observation of micropores] The micropores present at the interface between the gold fine particle sintered body layer and the gold particle-containing thermosetting epoxy resin layer of the bonded bodies according to Examples 1 to 3 were evaluated. First, in FE-SEM cross-sectional images of each interface at 5,000 magnification, it was confirmed that there were micropores present at the interface where the opening diameter of the micropore was 1 μm to 10 μm and the distance b' was 2 μm or more, where a is the opening diameter of the micropore present at the interface and b' is the distance the thermosetting epoxy resin penetrated into the micropore. Then, when the distance from the center of the opening diameter a to the deepest part of the micropore was b, it was confirmed that when 100 or more micropores were detected where the opening diameter a was 1 μm to 10 μm and the distance b was 2 μm or more, it was confirmed that 60% or more of the micropores had the distance b' of 2 μm or more. Furthermore, when the ratio b' / a, which is the ratio of the opening diameter a to the distance b', was calculated for each of the micropores present in an amount of 60% or more, it was confirmed that the average value of the b' / a ratio was 1.3 or more. The values ​​of a and b for several examples (three examples in total: micropores 1 to 3) of the 100 or more micropores present at the boundary surface between the gold particle-containing thermosetting epoxy resin layer and the gold fine particle sintered body layer of the bonded body according to Example 2 are shown in Table 3. The morphology of these micropores is also shown in Figure 4.

[0052] [Table 3]

[0053] [Observing the boundary line] Ten FE-SEM cross-sectional images (10 μm × 10 μm) of the interface between the gold fine particle sintered body layer and the gold particle-containing thermosetting epoxy resin layer were prepared (randomly) for the bonded bodies of Examples 1 to 3. In each cross-sectional image, the boundary between the gold fine particle sintered body layer and the gold particle-containing thermosetting epoxy resin layer was measured (randomly) over a distance of 5 μm. It was confirmed that the total distance of the gap between the gold fine particle sintered body layer and the gold particle-containing thermosetting epoxy resin layer at the boundary was 1 μm or more. Furthermore, as can be seen by comparing Figure 5 (an enlarged view of Figure 4), Figure 7 (an enlarged view of Figure 6), and Figure 9 (an enlarged view of Figure 8), in Figure 5, both sintering of the gold microparticle sintered body and gold particles (which is heavily involved in bonding the composite) and bonding of the gold microparticle sintered body layer and the gold particle-containing thermosetting epoxy resin layer (which is somewhat involved in bonding the composite) are performed, whereas in Figures 7 and 9, bonding is mainly performed between the metal gold microparticle sintered body layer and the gold particle-containing thermosetting epoxy resin layer.

[0054] As shown in Tables 2 and 3, in the bonded bodies of Examples 1 to 3 obtained by applying a dispersion containing gold microparticles with an imine compound held on the surface to the surface of a gold particle-containing thermosetting epoxy resin layer formed on a tungsten substrate and then performing a heat treatment at a temperature of 300°C or less, it was confirmed that bonded bodies with high bonding strength that did not peel even in a tape peeling test were obtained. Furthermore, as shown in Table 2, it was confirmed that the density of the gold microparticle sintered body layer of the bonded bodies of Examples 1 to 3 was high, at 80% or more. Therefore, it was confirmed that bonded bodies with low volume resistivity and good conductivity were obtained. As described above, the bonded body disclosed herein can provide a highly reliable bonded body including a metal fine particle sintered body layer, a resin layer, and a substrate.

Claims

1. A bonded body comprising a substrate, a resin layer made of resin and formed on the substrate, and a metal layer made of a metal fine particle sintered body and formed on the resin layer, the resin layer contains metal particles, and at least some of the contained metal particles are sintered with the metal microparticle sintered body; micropores are present at the boundary surface between the metal layer and the resin layer toward the inside of the resin layer, and the metal microparticle sintered body is inserted into at least a part of the micropores; Here, the opening diameter of the micropore in the FE-SEM cross-sectional image reflecting the boundary surface is a, and the distance from the center of the opening diameter a to the deepest part of the micropore into which the metal microparticle sintered body has penetrated is b', and there are bonded bodies in which the opening diameter a is 1 μm or more and 10 μm or less and the distance b' is 2 μm or more.

2. The bonded body according to claim 1 , wherein the opening diameter a is 1 μm or more and 3 μm or less, and the distance b′ is 2 μm or more.

3. 2. The bonded body according to claim 1, wherein the opening diameter a is 1 μm or more and 3 μm or less, and the distance b' is 3 μm or more.

4. 2. The bonded structure according to claim 1, wherein the opening diameter a is 1 μm or more and 2 μm or less, and the distance b′ is 4 μm or more.

5. 2. The bonded body according to claim 1, wherein, in an FE-SEM cross-sectional image of the boundary surface, 100 or more micropores are detected in which the opening diameter a is 1 μm or more and 10 μm or less and the distance b is 2 μm or more, where b is the distance from the center of the opening diameter a to the deepest part of the micropore, and 60% or more of the micropores have the distance b of 2 μm or more.

6. 6. The bonded structure according to claim 5, wherein, when a ratio b' / a, which is a ratio of the opening diameter a to the distance b', is calculated for each of the micropores that account for 60% or more of the micropores, the average value of the b' / a ratio is 1.3 or more.

7. 7. The joined body according to claim 1, wherein when ten FE-SEM cross-sectional images (10 μm×10 μm) of the boundary surface between the metal layer and the resin layer are prepared and a boundary line between the metal layer and the resin layer is measured over a distance of 5 μm in each cross-sectional image, the total distance of a portion of the boundary line where a gap occurs between the metal layer and the resin layer is 1 μm or more.

8. The joined body according to claim 1 , wherein the main constituent metal element of the metal fine particles constituting the metal fine particle sintered body is a noble metal element.

9. The bonded body according to claim 1 , wherein the resin is a thermosetting resin.

10. The bonded structure according to claim 1 , wherein the resin is a thermosetting epoxy resin.

11. The bonded body according to claim 1 , wherein the metal layer has a density of 80% or more.

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