Metal-resin bonded body and its manufacturing method

Abstract

To provide a high-reliability composite having a sintered metal particulate layer and a resin layer, and a method for producing the composite.SOLUTION: A composite disclosed herein is a composite of a metal layer composed of sintered metal particulates and a resin layer composed of a resin. A boundary surface of the metal layer with the resin layer includes micropores extending toward the inside of the metal layer, and at least some of the micropores receive the resin thereinto.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., and a resin layer made of resin. 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 and a resin layer. Another object of the present invention is to provide a method for manufacturing such a joined body. [Means for solving the problem]

[0006] According to the present invention, there is provided a bonded body comprising a metal layer (i.e., a metal microparticle sintered body layer) made of a metal microparticle sintered body and a resin layer made of a resin. In the bonded body disclosed herein, the boundary between the metal layer and the resin layer has micropores facing inward of the metal layer, and the resin penetrates at least some of the micropores. Furthermore, when the opening diameter of the micropore in an FE-SEM cross-sectional image of 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 resin has penetrated is b', the bonded body is characterized in that there are some micropores in which the opening diameter a is 100 nm or more and 300 nm or less, and the distance b' is 30 nm or more. In a bonded body of this configuration, the resin in the micropores fulfills the so-called anchor effect, thereby achieving high bonding strength. 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 structure disclosed herein, when 100 or more micropores are detected (randomly detected) in an FE-SEM cross-sectional image of the boundary surface, where b is the distance from the center of the opening diameter a to the deepest part of the micropore, and the opening diameter a is 100 nm or more but 300 nm or less and the distance b' is 30 nm or more, 60% or more of the micropores have the distance b' of 30 nm or more. In a bonded structure having such a configuration, the anchor effect is more effectively exerted, thereby achieving higher bonding strength.

[0008] In a preferred embodiment of the bonded body disclosed herein, metal particles are present within the resin layer, and at least a portion of the present metal particles are sintered with the metal microparticle sintered body. The internal metal particles are sintered with the metal microparticle sintered body, and the bonding strength of the bonded body is suitably improved.

[0009] 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.

[0010] 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.

[0011] In a preferred embodiment of the bonded body disclosed herein, the resin contains a thermoplastic resin as a constituent element. The thermoplastic resin allows the technology disclosed herein to be suitably implemented.

[0012] In a preferred embodiment, the resin contains a thermoplastic polyimide resin as a constituent element. Among thermoplastic resins, polyimide resins in particular have high heat resistance, and therefore can provide highly reliable bonded bodies.

[0013] 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>.

[0014] The present invention also provides a method for producing the bonded structure disclosed herein. Specifically, the method comprises preparing a dispersion containing the metal fine particles, applying the dispersion to the surface of a molded body made of the unsolidified resin, heating the molded body to a temperature range where the metal fine particles can be sintered to form the metal layer, and solidifying the molded body to form the resin layer. This method for producing a bonded structure allows for reliable bonded structures with desired strength to be obtained. 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.

[0015] In a preferred embodiment of the method for producing a conjugate disclosed herein, the imine compound has the following structural formula: R 0 R1 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]

[0016] [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 example of an FE-SEM observation image (100,000 magnifications) of the interface between a gold fine particle sintered body layer and a gold particle-containing thermoplastic polyimide resin layer according to Example 2. [Figure 5] 10 is another example of an FE-SEM observation image (100,000 magnifications) of the interface between the gold fine particle sintered body layer and the gold particle-containing thermoplastic polyimide resin layer according to Example 2. [Figure 6] 10 is another example of an FE-SEM observation image (100,000 magnifications) of the interface between the gold fine particle sintered body layer and the gold particle-containing thermoplastic polyimide resin layer according to Example 2. [Figure 7] 10 is an example of an FE-SEM observation image (100,000 magnifications) of the interface between a gold fine particle sintered body layer and a gold particle-containing thermoplastic polyimide resin layer according to Example 5. [Figure 8] 10 is another example of an FE-SEM observation image (100,000 magnifications) of the interface between the gold fine particle sintered body layer and the gold particle-containing thermoplastic polyimide resin layer according to Example 5. [Figure 9]10 is another example of an FE-SEM observation image (100,000 magnifications) of the interface between the gold fine particle sintered body layer and the gold particle-containing thermoplastic polyimide resin layer according to Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0017] 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.

[0018] <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.

[0019] 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.

[0020] 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 2are 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.

[0021] 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.

[0022] 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.

[0023] <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.

[0024] 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.

[0025] <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 achieved. 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 polyamide-imide resins and thermoplastic polyimide resins. Furthermore, the Tg of the thermoplastic polyimide resins that can be used in the present invention is typically 200 to 300°C. Among these, those that are soluble in NMP, THF, PhFG, γ-butyrolactone, triglyme, butyl acetate, MMA, benzyl alcohol, dioxane, anone, DMAc, MIBK, and other solvents (such as phenolic solvents and polar solvents) are preferably used.

[0026] <Internal metal particles> The resin may contain metal particles (hereinafter, such metal particles may also be 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.

[0027] <Density of the 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%).

[0028] <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 vertices of the protruding portions of the metal microparticle sintered body at the interface (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 through 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 defined as b. b' is the distance from the center of the opening diameter a to the deepest part of the micropore where the resin 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 to the part where the resin has penetrated, an additional line segment is added, and the sum of these line segments is defined as b'. Preferably, the value of a is 100 nm to 300 nm, and the value of b' is 30 nm to 500 nm. Alternatively, a may be 100 nm to 300 nm, and b' may be 200 nm or greater. Alternatively, a may be 100 nm to 300 nm, and b' may be 400 nm or greater. Alternatively, a may be 100 nm to 150 nm, and b' may be 400 nm or greater. From the viewpoint of the anchoring effect, preferably b' > a, more preferably b' > 1.5a, even more preferably b' > 2a, and particularly preferably b' > 3a. Furthermore, when 100 or more micropores having a value of a between 100 nm and 300 nm and b equal to or greater than 30 nm are detected, preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more satisfy the relationship b' > a, thereby more suitably realizing the anchoring effect.

[0029] As an example of the bonded structure disclosed herein, an example of a bonded structure of a gold fine particle sintered body layer and a gold particle-containing thermoplastic polyimide resin layer will be described below, but such an example is not intended to limit the present invention.

[0030] <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.

[0031] <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.

[0032] 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.

[0033] 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.

[0034] (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 pyrolysis GCMS spectrum obtained is shown in Figure 1. The MS spectrum of the detected peak of the imine compound (peak ■ in the corresponding pyrolysis GCMS spectrum) is shown in Figure 2.

[0035] 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).

[0036] [Table 1]

[0037] 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.

[0038] <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.

[0039] <4. 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”).

[0040] <5. Example of Production of Bonded Body of Gold Fine Particle Sintered Body Layer and Gold Particle-Containing Thermoplastic Polyimide Resin Layer> Example 1: The polyimide resin coating was applied to a tungsten substrate and dried at 60°C for 1 hour. This resulted in the formation of a molded body (hereinafter simply referred to as "polyimide resin molding") made of a gold particle-containing thermoplastic polyimide resin on the tungsten substrate. A small amount of solvent from the polyimide resin coating remained on the polyimide resin molding, giving it some flexibility. The gold particle dispersion was then applied to the surface of the polyimide resin molding, and the resulting mixture was dried at 60°C for 1 hour. The temperature was then increased at a rate of 10°C / min, and the mixture was then heat-treated at 250°C for 30 minutes to sinter the gold particles and solidify the polyimide resin molding (to completely remove the solvent). As a result, a tungsten-gold particle-containing thermoplastic polyimide resin layer-gold particle sintered layer composite (hereinafter simply referred to as "composite") 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 polyimide resin molded body, 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 polyimide resin molded body, dried, and then heat-treated at 300°C for 30 minutes with a temperature increase rate of 10°C / min. As a result, a bonded body was obtained. Example 4: The same operation as in Example 1 was carried out, except that the drying conditions for the polyimide resin coating were changed to 15 minutes at 130° C. and then 30 minutes at 180° C. As a result, a bonded body was obtained. Example 5: The same operation as in Example 2 was carried out, except that the drying conditions for the polyimide resin coating were 130° C. for 15 minutes and then 180° C. for 30 minutes. As a result, a bonded body was obtained. Example 6: The same operation as in Example 3 was carried out, except that the drying conditions for the polyimide resin coating were changed to 15 minutes at 130° C. and then 30 minutes at 180° C. As a result, a bonded body was obtained.

[0041] Comparative Example 1: The polyimide resin coating was applied to a tungsten substrate, dried at 130°C for 15 minutes and then at 180°C for 30 minutes, and then heated at a rate of 10°C / min and heat-treated at 280°C for 50 minutes to solidify the polyimide resin molding (to completely remove the solvent). The gold microparticle dispersion was applied to the surface of the solidified polyimide resin molding, dried at 60°C for 1 hour, heated at a rate of 10°C / min and heat-treated at 250°C for 30 minutes to sinter it. As a result, the gold microparticle sintered layer was not bonded to the gold particle-containing thermoplastic polyimide resin layer, and formed a separate film.

[0042] <6. 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] Comparative Example 2: The epoxy resin coating was applied to a tungsten substrate and dried at 60°C for 1 hour. This resulted in the formation of a molded body made of gold particle-containing thermosetting epoxy resin (hereinafter simply referred to as "epoxy resin molded body"). The epoxy resin molded body had lost its fluidity. The gold particle dispersion was then applied to the surface of the epoxy resin molded body, which was then dried at 60°C for 1 hour. The temperature was then increased at a rate of 10°C / min, and the body was heat-treated at 250°C for 30 minutes to sinter and harden the epoxy resin molded body. As a result, peeling occurred between the gold particle sintered body layer and the gold particle-containing thermosetting epoxy resin layer.

[0044] <7. Direct formation of a sintered gold particle layer on a substrate> Comparative Example 3: 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 4: The gold particle dispersion was applied to a tungsten 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 tungsten substrate. Comparative Example 5: The gold particle dispersion was applied to the non-adhesive side of a polyimide tape (Kapton (registered trademark) tape). After drying at 60°C for 1 hour, it was heat-treated at 300°C for 30 minutes. As a result, the resulting gold particle sintered body layer did not adhere to the polyimide tape and became a single film.

[0045] <8. Evaluation test of the conjugate> [Tape peeling test] A peel test was carried out by attaching cellophane tape to the bonded structures obtained in Examples 1 to 6 and then peeling it off. The test results are shown in the corresponding columns in Table 2.

[0046] [Evaluation of the density of sintered gold particle layers] The cross sections of the bonded bodies obtained in Examples 1 to 6 were subjected to ion milling. Then, from the FE-SEM cross-sectional images of each ion-milled polished surface obtained at 10,000 magnification, the area of ​​the black voids (i.e., hollows) 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.

[0047] [Table 2]

[0048] [Observation of micropores] The micropores present at the interface between the gold particle-sintered body layer and the gold particle-containing thermoplastic polyimide resin layer of the bonded bodies according to Examples 1 to 6 were evaluated. First, in a 100,000-magnification FE-SEM cross-sectional image of each interface, it was confirmed that the micropores had an opening diameter of 100 nm or more and a distance b' of 30 nm or more, where a is the opening diameter of the micropore and b' is the distance from the center of the opening diameter a to the deepest part of the micropore into which the thermoplastic polyimide resin has penetrated. Furthermore, in a 100,000-magnification FE-SEM cross-sectional image of the interface, it was confirmed that the micropores had an opening diameter a of 100 nm or more and a distance b' of 30 nm or more, where b is the distance from the center of the opening diameter a to the deepest part of the micropore. When 100 or more micropores were randomly detected, where the opening diameter a was 100 nm or more and a distance b was 30 nm or more, it was confirmed that 60% or more had a distance b' of 30 nm or more. Table 3 shows the values ​​of a and b' for several examples (here, a total of nine examples) of the 100 or more micropores present at the boundary surface between the gold particle-containing thermoplastic polyimide resin layer and the gold fine particle sintered body layer of the bonded bodies according to Examples 2 and 5. The morphology of the micropores is also shown in Figures 4 to 9.

[0049] [Table 3]

[0050] As shown in Tables 2 and 3, the bonded bodies of Examples 1 to 6 were obtained by applying a dispersion containing gold microparticles with an imine compound held on the surface to the surface of a molded body made of unsolidified thermoplastic polyimide resin and then performing a heat treatment in a temperature range where the gold microparticles can be sintered (here, 250°C to 300°C). It was confirmed that bonded bodies with high bonding strength that did not peel even in a tape peeling test were obtained. It was also confirmed that the density of the gold microparticle sintered body layer of the bonded bodies of Examples 1 to 6 was high, at 80% or more. This confirmed that bonded bodies with low volume resistivity and good conductivity were obtained. Thus, according to the bonded body disclosed herein, it is possible to provide a highly reliable bonded body including a metal fine particle sintered body layer and a resin layer.

Claims

1. A bonded body comprising a metal layer made of a metal fine particle sintered body and a resin layer made of a thermoplastic polyimide resin or a thermoplastic resin having a glass transition temperature (Tg) in the range of 200°C to 300°C, micropores are present in the metal layer at the interface with the resin layer, the micropores being directed toward the inside of the metal layer; The resin is filled into at least some of the micropores, metal particles are present in the resin layer, and at least a part of the present metal particles is sintered with the metal microparticle sintered body; Here, the opening diameter of the micropore in the FE-SEM cross-sectional image that reflects 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 resin has penetrated is b', and there is a bonded body in which the opening diameter a is 100 nm or more and 300 nm or less and the distance b' is 30 nm or more.

2. The bonded structure according to claim 1 , wherein the opening diameter a is 100 nm or more and 300 nm or less, and the distance b′ is 200 nm or more.

3. 2. The bonded structure according to claim 1, wherein the opening diameter a is 100 nm or more and 300 nm or less, and the distance b' is 400 nm or more.

4. 2. The bonded structure according to claim 1, wherein the opening diameter a is 100 nm or more and 150 nm or less, and the distance b' is 400 nm 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 100 nm or more and 300 nm or less and the distance b is 30 nm 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 30 nm or more.

6. 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.

7. The bonded body according to claim 1 , wherein the main constituent metal element of the metal fine particles that constitute the metal fine particle sintered body is gold (Au).

8. A bonded body comprising a metal layer made of a metal fine particle sintered body and a resin layer made of a thermoplastic polyimide resin or a thermoplastic resin having a glass transition temperature (Tg) in the range of 200°C to 300°C, The main constituent metal element of the metal fine particles constituting the metal fine particle sintered body is gold (Au), micropores are present in the metal layer at the interface with the resin layer, the micropores being directed toward the inside of the metal layer; The resin is filled into at least some of the micropores, Here, the opening diameter of the micropore in the FE-SEM cross-sectional image that reflects 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 resin has penetrated is b', and there is a bonded body in which the opening diameter a is 100 nm or more and 300 nm or less and the distance b' is 30 nm or more.

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