Temporary adhesive body of ceramic resin composite and metal plate, method for manufacturing the same, transport body including the same, and transport method thereof

Abstract

To make a ceramic resin composite having low strength less likely to break and deteriorate. A ceramic metal temporary adhesive body includes: a ceramic resin composite in which a thermosetting resin composition having a cyanate ester group is impregnated in a non-oxide ceramic sintered body in such a manner that a solidification rate calculated by a differential scanning calorimeter is 5.0% or more and 70% or less; and a metal plate in a state of being temporarily adhered to at least one face of the ceramic resin composite, a shear adhesive strength of the ceramic resin composite and the metal plate being 0.1 MPa or more and 1.0 MPa or less.

Description

Technical Field

[0001] The present invention relates to a temporary adhesive for a ceramic resin composite and a metal plate using a thermosetting resin composition and a method thereof, and further to a transport body comprising the temporary adhesive and a method thereof. Background Technology

[0002] In recent years, with the increasing performance and miniaturization of electronic devices such as mobile phones, LED lighting devices, and automotive power modules, mounting technologies at all levels—semiconductor devices, printed circuit board mounting, and device mounting—are rapidly advancing. Consequently, the heat density inside electronic devices is increasing year by year, making efficient heat dissipation and ensuring the reliability of these devices crucial issues. Therefore, ceramic-resin composite sheets used to fix electronic components require high thermal conductivity and reliability.

[0003] Previously, the above-mentioned ceramic resin composite sheets used a thermosetting resin composition obtained as follows: ceramic powders with high thermal conductivity, such as alumina, silicon nitride, boron nitride, and aluminum nitride, were dispersed in an uncured thermosetting resin, and then formed into a sheet using coating or other methods based on various coating machines, and the thermosetting resin was heated to a semi-cured state.

[0004] In Patent Document 1, for a metal-based circuit board, a thermally conductive insulating adhesive sheet is obtained by placing a metal foil on a thermosetting resin in which ceramic powder is dispersed in a semi-cured state (stage B), and then curing the thermosetting resin contained in the thermally conductive insulating adhesive sheet to form stage C. This allows for the simple acquisition of a metal-based circuit board with excellent heat dissipation.

[0005] However, in the invention of the aforementioned Patent Document 1, since there is a thermosetting resin layer with low thermal conductivity between the particles of ceramic powder, the thermal conductivity is only 15 W / (m·K) at most, which is a limit in obtaining high thermal conductivity.

[0006] Therefore, Patent Document 2 proposes a structure in which a ceramic resin composite, whose pores are filled with thermosetting resin (obtained by sintering primary ceramic particles with high thermal conductivity to form a three-dimensional continuous integral structure), is processed into a plate shape. This structure achieves a ceramic resin composite with high thermal conductivity and adhesion.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2009-49062

[0010] Patent Document 2: Japanese Patent Application Publication No. 2016-111171 Summary of the Invention

[0011] The problem the invention aims to solve

[0012] However, in the invention of Patent Document 2 mentioned above, the method for bonding the ceramic resin composite sheet to the metal plate employs the following approach: after heating and curing the ceramic resin composite sheet, a thermosetting resin is applied again to the surface of the ceramic resin composite sheet, followed by pressure and heating. In this method, strong adhesive force is exhibited due to the complete curing of the resin; however, once bonding is performed, the thermosetting resin undergoes irreversible curing and modification, making further bonding impossible. In other words, to bond metal plates to both sides of the ceramic resin composite sheet, a single heating process is required.

[0013] Ceramic-resin composite sheets bonded to both sides by heating and applying pressure cannot be further processed. Therefore, there is a problem that the requirements of customers wanting to process ceramic-resin composite sheets cannot be adequately met. On the other hand, if the ceramic-resin composite sheets are transported without the bonded metal sheets, their weak strength makes them prone to cracking and other deterioration during transport.

[0014] Solution for solving the problem

[0015] In view of the background technology described above, the object of the present invention is to provide a temporary adhesive that can be safely and easily transported even when containing ceramic resin composites with low strength, and which can be reprocessed. The inventors of this applicant discovered that by bonding a metal plate to one side of the ceramic resin composite without modifying the thermosetting resin before transporting it to the customer, the metal plate can be bonded to the remaining side after transport, and the impact applied to the ceramic resin composite during transport can be mitigated to prevent deterioration, thus completing the present invention. That is, in embodiments of the present invention, the following solutions can be provided to solve the above-mentioned problems. [1]

[0017] Ceramic-metal temporary adhesive, comprising:

[0018] A ceramic-resin composite is formed by impregnating a thermosetting resin composition having cyanate groups into a non-oxide ceramic sintered body in such a manner that the curing rate, calculated by differential scanning calorimetry, is 5.0% or more and 70% or less; and

[0019] A metal plate, which is temporarily bonded to at least one side of the ceramic resin composite.

[0020] The shear bond strength between the aforementioned ceramic resin composite and the aforementioned metal plate is above 0.1 MPa and below 1.0 MPa. [2]

[0022] As described in [1], the ceramic-metal temporary adhesive is in a state where the metal plate is only temporarily bonded to one side of the ceramic-resin composite. [3]

[0024] The transport body is formed by wrapping the ceramic-metal temporary adhesive described in [1] or [2] with packaging material. [4]

[0026] A method for manufacturing a ceramic-metal temporary adhesive, comprising the following steps:

[0027] The step of impregnating a thermosetting resin composition having cyanate groups into a non-oxide ceramic sintered body in such a way that the curing rate calculated by differential scanning calorimetry is 5.0% or more and 70% or less, thereby obtaining a ceramic resin composite.

[0028] The step of coating a liquid compound containing active hydrogen onto at least one side of the aforementioned ceramic resin composite or a metal plate with a ten-point average roughness of less than 20 μm; and

[0029] The steps involve bonding the aforementioned ceramic resin composite to the aforementioned metal plate, and then applying a compressive load of 250 MPa or less at a temperature ranging from 0°C to 40°C to temporarily bond the aforementioned ceramic resin composite to the aforementioned metal plate, such that the shear bond strength between the aforementioned ceramic resin composite and the aforementioned metal plate is 0.1 MPa or more and 1.0 MPa or less. [5]

[0031] A method for transporting a ceramic-metal temporary adhesive, comprising:

[0032] The step of storing the transport body described in [3] in a transport container; and

[0033] The steps for transporting the aforementioned transport containers. [6]

[0035] The transportation method described in [5] is configured such that the aforementioned transport body and the cushioning material are housed together in a transport box, thereby making the aforementioned ceramic-metal temporary adhesive substantially stationary within the transport box.

[0036] The effects of the invention

[0037] The ceramic-metal temporary adhesive provided by the embodiments of the present invention can achieve the following effects: the ceramic resin composite part can be processed after being transported to the customer, and it has strong resistance to impact during transportation and high reliability. Detailed Implementation

[0038] Unless otherwise specified, the numerical ranges in this specification include both the upper and lower limits. The following describes the various materials, evaluation methods, and evaluation results used in the embodiments of this invention.

[0039] Temporary adhesive

[0040] The ceramic-metal temporary bond according to embodiments of the present invention refers to a product obtained by temporarily bonding a metal plate to at least one side, preferably only one side, of a "ceramic resin composite" or "ceramic resin composite sheet" described later. In this specification, "temporary bonding" of the metal plate means bonding the metal plate to the ceramic resin composite without heating the thermosetting resin impregnated in it, i.e., without modifying the thermosetting resin. It should be noted that "heating" in the above definition of "temporary bonding" refers to applying heat to the ceramic resin composite and the metal plate, which are the objects of temporary bonding, at a temperature exceeding the ambient temperature in an environment where they are placed. The ambient temperature is typically 0–40°C or room temperature. Such "heating" includes, for example, applying heat at a temperature exceeding 40°C or room temperature; for example, applying heat of approximately 200°C using a heater, but does not include slight temperature rises caused by pressing. That is, the "temporary bond" in this specification refers to a product in a state where the ceramic resin composite portion can be further processed without substantially undergoing such "heating," rather than a final product. Furthermore, the "modification" in the above definition of "temporary bond" refers to the modification of the thermosetting resin due to heat, resulting in a substantial increase in the curing rate due to the curing reaction. In this specification, the curing rate did not substantially increase before and after the temporary bond, except for measurement errors; therefore, it can be considered that the thermosetting resin was not modified. For the shear bond strength between the ceramic resin composite and the metal plate based on this temporary bond, practically, it is preferable to achieve a degree to which detachment does not occur even when the temporary bond is moved or its orientation is changed. In a preferred embodiment, this shear bond strength is 0.1 MPa or more, more preferably 0.2 MPa or more, and even more preferably 0.3 MPa or more. When the shear bond strength is less than 0.1 MPa, the metal plate and the ceramic resin composite may easily detach, which is not preferred. Furthermore, the upper limit of the shear bond strength is 1.0 MPa. When bonding is performed in a state where the thermosetting resin impregnated in the ceramic resin composite does not change due to heating, this upper limit is usually not exceeded. In some embodiments, the temporarily bonded parts can also be peeled off by mechanical means. In another embodiment, the temporarily bonded parts can be kept in a state where they are not peeled off until the final product is obtained. In addition, in this specification, the bonding with heat and pressure used to obtain the final product is sometimes referred to as "formal bonding" to distinguish it from the "temporary bonding" mentioned above. It should be noted that the shear bond strength between the ceramic resin composite and the metal plate when formal bonding is performed by heat and pressure is generally considered to be at least 2 MPa or more, which can be clearly distinguished from the shear bond strength based on the "temporary bonding" mentioned above.

[0041] <Non-oxide ceramic sintered bodies, ceramic-resin composites, ceramic-resin composite sheets, insulating layers>

[0042] In this specification, a state in which two or more non-oxide ceramic primary particles are aggregated together through sintering is defined as a "non-oxide ceramic sintered body" with a three-dimensional continuous integral structure. Furthermore, in this specification, a composite comprising a non-oxide ceramic sintered body and a thermosetting resin composition is defined as a "ceramic resin composite". Additionally, a product obtained by processing a ceramic resin composite into a plate shape is defined as a "ceramic resin composite sheet". In a "ceramic resin composite" or "ceramic resin composite sheet", at least two sides are capable of bonding a metal plate.

[0043] For the bonding between primary particles of non-oxide ceramics caused by sintering, an evaluation can be performed by observing the bonding portion between primary particles in the cross-section of the primary particles using a scanning electron microscope (e.g., "JSM-6010LA" (manufactured by Nippon Electron)). As a pretreatment for observation, the non-oxide ceramic particles can be embedded in resin, processed using a CP (section polishing) method, fixed on a sample stage, and then coated with osmium. The magnification can be set to, for example, 1500x. Alternatively, the non-oxide ceramic sintered body for evaluation can be obtained by ashing a thermosetting resin composition of a ceramic-resin composite at 500–900°C in an atmospheric atmosphere. Without bonding caused by the sintering of the primary particles of the non-oxide ceramic, the shape cannot be maintained during ashing.

[0044] <Average Major Diameter>

[0045] The average major diameter of the non-oxide ceramic primary particles in the non-oxide ceramic sintered body is preferably in the range of 3.0–60 μm. When the average major diameter is less than 3.0 μm, the elastic modulus of the non-oxide ceramic sintered body becomes higher. Therefore, when bonding metal plates, metal circuits, or other adherends to the ceramic-resin composite sheet by heating and pressurizing, the ceramic sintered body becomes difficult to follow the surface irregularities of the adherends, potentially leading to a decrease in thermal conductivity and tensile shear bond strength. When the average major diameter exceeds 60 μm, the strength of the ceramic-resin composite decreases, potentially resulting in a decrease in the bond strength with the adherends.

[0046] <Definition and Evaluation Methods of Average Major Diameter>

[0047] Regarding the average major diameter of primary particles in non-oxide ceramics, as a pretreatment step for observation, the sintered non-oxide ceramic body can be embedded in resin, processed using a CP (section polishing) method, fixed on a sample stage, and then coated with osmium. Then, a scanning electron microscope (SEM) such as the "JSM-6010LA" (manufactured by Nippon Electron Corporation) can be used to capture SEM images. The resulting cross-sectional particle images are then imported into image analysis software such as "A-Image-kun" (manufactured by Asahi Kasei Engineering Corporation) for measurement. The image magnification can be set, for example, to 100x, and the image resolution can be set to 15.1 megapixels. In manual measurement, the major diameter of 100 randomly selected particles can be calculated, and their average value can be used as the average major diameter.

[0048] Aspect Ratio

[0049] The aspect ratio of the primary particles of the non-oxide ceramic is preferably in the range of 5.0 to 30. If the aspect ratio is less than 5.0, the elastic modulus of the non-oxide ceramic sintered body becomes higher. Therefore, when bonding the adherend (which is a metal plate (or may include metal circuits, etc.)) to the ceramic resin composite sheet by heating and pressurizing, the ceramic sintered body becomes difficult to follow the surface irregularities of the adherend, and the thermal conductivity and tensile shear bond strength may decrease. Conversely, when the aspect ratio is greater than 30, the strength of the ceramic resin composite decreases, and therefore, the bond strength with the adherend may decrease.

[0050] <Methods for evaluating aspect ratio>

[0051] For aspect ratio, as a pretreatment for observation, the non-oxide ceramic sintered body can be embedded in resin, processed using a CP (section polishing) method, fixed on a sample stage, and then coated with osmium. Then, a scanning electron microscope (SEM) such as the JSM-6010LA (manufactured by Nippon Electron Corporation) can be used to capture SEM images. The resulting particle images of the cross-section are then imported into image analysis software such as Asahi Kasei Engineering Corporation for measurement. The image magnification can be set to 100x, and the image resolution can be set to 15.1 megapixels. In manual measurement, 100 arbitrary particles can be observed, and the lengths of the major and minor axes of each particle can be measured. The aspect ratio of each particle is calculated using the formula: aspect ratio = major axis / minor axis, and their average value is defined as the aspect ratio.

[0052] <Proportion of non-oxide ceramic sintered body>

[0053] The preferred amount of non-oxide ceramic sintered body in the ceramic-resin composite is 35–70% by volume (i.e., the amount of thermosetting resin composition is 65–30% by volume). When the amount of non-oxide ceramic sintered body is less than 35% by volume, the proportion of thermosetting resin composition with low thermal conductivity increases, thus reducing the thermal conductivity. When the amount of non-oxide ceramic sintered body is greater than 70% by volume, when the adherend (which is a metal plate (or may include metal circuits, etc.)) is formally bonded to the ceramic-resin composite by heating and pressurizing, the thermosetting resin composition becomes difficult to penetrate the unevenness of the adherend surface, potentially reducing the tensile shear bond strength and thermal conductivity. The proportion (by volume) of non-oxide ceramic sintered body in the ceramic-resin composite can be determined based on the determination of the bulk density and porosity of the non-oxide ceramic sintered body as shown below.

[0054] Bulk density (D) of non-oxide ceramic sintered body = mass / volume…··(1)

[0055] Porosity of non-oxide ceramic sintered body = (1 - (D / true density of non-oxide ceramic)) × 100 = proportion of thermosetting resin ... (2)

[0056] The proportion of non-oxide ceramic sintered body = 100 - the proportion of thermosetting resin... (3)

[0057] Furthermore, while conventional sintered ceramic bodies typically exhibit both closed and open pores, non-oxide sintered ceramic bodies can eliminate the presence of closed pores (below 1%) by controlling the average length and aspect ratio of the non-oxide ceramic particles within specific ranges. Additionally, there are no particular restrictions on the average pore size, but considering the impregnation properties of thermosetting resins, 0.1–3.0 μm is practical.

[0058] <Main Components of Non-Oxide Ceramic Sintered Bodies>

[0059] Assuming that the ceramic resin composite containing the non-oxide ceramic sintered body is used in power modules and the like requiring high reliability, the main component of the non-oxide ceramic sintered body is preferably boron nitride. In a further preferred embodiment, the thermal conductivity of the boron nitride can be set to 40 W / (m·K) or higher. Furthermore, if the aim is to obtain a sheet-like final product, the shape of the non-oxide ceramic sintered body is preferably a flat plate.

[0060] <Manufacturing Method of Non-Oxide Ceramic Sintered Body>

[0061] Non-oxide ceramic sintered bodies can be manufactured, for example, by adding sintering aids such as calcium carbonate, sodium carbonate, and boric acid to boron nitride powder at a ratio of approximately 0.01 to 20% by weight, forming the body using known methods such as molding or cold isostatic pressing (CIP), and then sintering it at a temperature of 1500 to 2200°C for approximately 1 to 30 hours in a non-oxidizing atmosphere such as nitrogen or argon. This manufacturing method is known, and commercially available products are also available. Furthermore, when using aluminum nitride or silicon nitride powders, sintering aids such as yttrium oxide, alumina, magnesium oxide, and rare earth element oxides can be used, and the body can be manufactured using the same method. Examples of sintering furnaces include muffle furnaces, tubular furnaces, atmosphere furnaces (including batch furnaces), rotary furnaces, spiral conveyor furnaces, tunnel furnaces, belt furnaces, pusher furnaces, and vertical continuous furnaces. They can be used differently depending on the purpose. For example, when manufacturing many varieties of non-oxide ceramic sintered bodies in small quantities, a batch furnace is used, while when manufacturing fixed varieties in large quantities, a continuous furnace is used.

[0062] <Composite Formation of Non-Oxide Ceramic Sintered Bodies with Thermosetting Resin Compositions>

[0063] A non-oxide ceramic sintered body and a thermosetting resin composition can be composited, for example, by impregnating the non-oxide ceramic sintered body with the thermosetting resin composition. Impregnation of the thermosetting resin composition can be performed by vacuum impregnation, pressure impregnation at 1–300 MPa, or a combination thereof. The pressure during vacuum impregnation is preferably 1000 Pa or less, more preferably 100 Pa or less. In the case of pressure impregnation, if the pressure is less than 1 MPa, the thermosetting resin composition may not be sufficiently impregnated into the interior of the non-oxide ceramic sintered body; if the pressure exceeds 300 MPa, the equipment size increases, which is therefore costly. To facilitate the impregnation of the thermosetting resin composition into the interior of the non-oxide ceramic sintered body, it is further preferable to heat the mixture to 100–180°C during vacuum impregnation or pressure impregnation to reduce the viscosity of the thermosetting resin composition.

[0064] Semi-curing of thermosetting resin compositions

[0065] A ceramic-resin composite can be obtained by semi-curing (B-stage curing) a thermosetting resin composition compounded with a non-oxide ceramic sintered body. Heating methods can include infrared heating, hot air circulation, oil heating, hot plate heating, or combinations thereof. For semi-curing, it can be performed directly using the heating function of the impregnation apparatus after impregnation, or it can be performed separately using a known apparatus such as a hot air circulation conveyor furnace after removal from the impregnation apparatus. In embodiments of the present invention, the curing rate of such a semi-cured thermosetting resin composition, as described below, is calculated by a differential scanning calorimeter and controlled within a range of 5.0% to 70%.

[0066] <Heating start temperature of thermosetting resin compositions>

[0067] The heating start temperature of the thermosetting resin composition contained in the ceramic resin composite, as measured by differential scanning calorimetry, is preferably 180°C or higher. If the heating start temperature is lower than 180°C, a curing reaction will occur when the thermosetting resin composition is heated during vacuum impregnation and pressurized impregnation, leading to an increase in the viscosity of the thermosetting resin composition and the creation of voids in the ceramic resin composite, thus reducing the insulation breakdown voltage. There is no particular upper limit to the heating start temperature; considering the productivity of formally bonding the adherend (which may be a metal plate, including metal circuits, etc.) to the ceramic resin composite sheet through heating and pressurization, and the heat resistance of the device components, 300°C or lower is practical. The heating start temperature can be controlled by using curing accelerators, etc.

[0068] <Evaluation Method for the Heating Onset Temperature of Thermosetting Resin Compositions>

[0069] The heating start temperature refers to the temperature obtained from the intersection of the baseline and the extrapolation line drawn along the rise of the curve in the heating curve obtained by heating and curing a thermosetting resin composition using a differential scanning calorimeter.

[0070] <Types of Thermosetting Resin Compositions>

[0071] As a thermosetting resin composition, a substance containing a cyanate ester group is essential. Examples of substances containing a cyanate ester group include 2,2'-bis(4-cyanoacetylphenyl)propane, bis(4-cyanoacetyl-3,5-dimethylphenyl)methane, 2,2'-bis(4-cyanoacetylphenyl)hexafluoropropane, 1,1'-bis(4-cyanoacetylphenyl)ethane, and 1,3-bis(2-(4-cyanoacetylphenyl)isopropyl)benzene. The reason for using substances containing a cyanate ester group is that the cyanate ester group exhibits weak adhesiveness through reaction with liquid compounds containing active hydrogen, thus enabling temporary bonding.

[0072] Furthermore, the resin with cyanate groups can be used alone, but it is preferable to appropriately mix it with resins having epoxy, hydroxyl, and maleimide groups. Examples of epoxy-containing substances include bisphenol A type epoxy resin, bisphenol F type epoxy resin, multifunctional epoxy resins (cresol NOVOLAC epoxy resin, dicyclopentadiene type epoxy resin, etc.), cyclic aliphatic epoxy resins, glycidyl ester type epoxy resins, and glycidylamine type epoxy resins. Examples of hydroxyl-containing substances include phenol NOVOLAC resin and 4,4'-(dimethylmethylene)bis[2-(2-propenyl)phenol]. Examples of maleimide-containing substances include 4,4'-diphenylmethane bismaleimide, m-phenylene bismaleimide, and bisphenol A diphenyl ether bismaleimide. Examples of maleimides include: 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 1,6'-bismaleimide-(2,2,4-trimethyl)hexane, 4,4'-diphenyl ether bismaleimide, 4,4'-diphenyl sulfone bismaleimide, 1,3-bis(3-maleimide phenoxy)benzene, 1,3-bis(4-maleimide phenoxy)benzene, bis-(3-ethyl-5-methyl-4-maleimide phenyl)methane, and 2,2-bis[4-(4-maleimide phenoxy)phenyl]propane.

[0073] <Methods for improving the adhesion of thermosetting resin compositions>

[0074] The thermosetting resin composition may appropriately contain a silane coupling agent for improving the adhesion between the non-oxide ceramic sintered body and the thermosetting resin composition, an antifoaming agent for promoting improved wettability and leveling properties and reducing viscosity, thereby reducing defects during impregnation and curing, a surface conditioner, and a wetting and dispersing agent. Furthermore, the resin preferably contains one or more ceramic powders selected from the group consisting of alumina, silicon oxide, zinc oxide, silicon nitride, aluminum nitride, boron nitride, and aluminum hydroxide.

[0075] <Cure rate of thermosetting resin compositions>

[0076] It is essential that the curing rate of the thermosetting resin composition impregnated in the non-oxide ceramic sintered body is 5.0% or higher and 70% or lower. When the curing rate is less than 5.0%, the uncured thermosetting resin melts due to the heat generated when cutting the ceramic-resin composite into sheet-like ceramic-resin composite plates, resulting in thickness variations. Furthermore, the ceramic-resin composite cannot withstand the impact during cutting, leading to cracking and a decrease in the insulation breakdown voltage of the circuit board. Consequently, a low thermal conductivity adhesive (resin) layer forms on the uneven surface of the adherend, further reducing thermal conductivity. When the curing rate is greater than 70%, less thermosetting resin composition seeps out during bonding by applying heat, making it easier for voids to form at the ceramic-resin composite-metal plate interface when bonding to a metal plate, reducing adhesive strength. This can potentially reduce the insulation withstand voltage.

[0077] <Evaluation Methods for the Curing Rate of Thermosetting Resin Compositions>

[0078] The curing rate of the thermosetting resin composition can be calculated using the following formula. A differential scanning calorimeter, such as the DSC6200R (manufactured by Seiko Instruments Inc.), can be used. To ensure complete curing of the thermosetting resin composition, 5 mg of α-alumina was used as a reference, and a sample amount of 5 mg was heated from room temperature to 300°C at a heating rate of 10°C / min under a nitrogen flow.

[0079] Curing rate (%) = (XY) / X × 100

[0080] X: Total heat (J / g) generated when the thermosetting resin composition in its pre-curing state is fully cured using a differential scanning calorimeter.

[0081] Y: Total heat (J / g) generated when a thermosetting resin composition that has been heated to a semi-cured state (stage B) is fully cured using a differential scanning calorimeter.

[0082] It should be noted that, in X and Y above, the "cured" state can be determined based on the peak of the obtained heating curve. Additionally, when a ceramic resin composite is used instead of the thermosetting resin composition itself, Y can also be calculated using the following formula.

[0083] Y = Y' × 100 / Z

[0084] Y': Total heat (J / g) generated when the resin composition within the ceramic resin composite is fully cured using a differential scanning calorimeter in the case of a ceramic resin composite.

[0085] Z: Volume percentage (vol%) of the thermosetting resin composition contained in the ceramic resin composite.

[0086] <Melting Temperature and Evaluation Methods of Thermosetting Resin Compositions>

[0087] The melting temperature of the thermosetting resin composition contained in the ceramic resin composite of this invention is preferably 70°C or higher. If the melting temperature is below 70°C, the thermosetting resin may melt due to the heat generated when the ceramic resin composite is cut into sheet-like ceramic resin composite sheets, resulting in thickness variations. There is no particular upper limit to the melting temperature; however, considering the need to suppress viscosity increases caused by the curing reaction of the thermosetting resin composition when bonding metal plates, metal circuits, or other adherends to the ceramic resin composite sheets by heating and pressurizing, a melting temperature of 180°C or lower is practical. It should be noted that the melting temperature described in this specification is the temperature of the endothermic peak when the thermosetting resin composition is heated, determined by differential scanning calorimetry.

[0088] <Thickness of ceramic-resin composite>

[0089] The thickness of the ceramic-resin composite (ceramic-resin composite sheet) is typically 0.32 mm, but can vary depending on the required properties. For example, when insulation under high voltage is less important than thermal resistance, a thin substrate of 0.1–0.25 mm can be used; conversely, when insulation and partial discharge characteristics under high voltage are important, a thick substrate of 0.35–1.0 mm can be used. Thus, although thin ceramic-resin composites are less resistant to impact, especially during transportation, the embodiments of the present invention improve their reliability against impact.

[0090] <Metal Plate>

[0091] In this specification, "metal plate" refers not only to a clean metal plate but also to metal circuits that can be used as substrates. Any metal can be used as the material for the metal plate, as long as it can be temporarily bonded to a thermosetting resin composition containing cyanate ester groups at a temperature ranging from 0°C to 40°C or at room temperature in the presence of a liquid compound containing active hydrogen. In a preferred embodiment, copper or aluminum can be used from the perspective of thermal conductivity and price. Alternatively, silver or gold can be used if only performance characteristics are considered, but these are price-related issues. The thickness of the metal plate is preferably 0.070 to 5.0 mm. A thickness less than 0.070 mm reduces the strength of the circuit board, making it prone to cracking, defects, and warping during the assembly of electronic components, and is therefore not preferred. A thickness exceeding 5.0 mm increases the thermal resistance of the metal plate itself, reducing the heat dissipation characteristics of the circuit board, and is also not preferred.

[0092] Temporary bonding surface for metal sheets

[0093] To improve the adhesion between the ceramic-resin composite (also known as the insulating layer) and the metal plate, it is ideal to perform surface treatments on the temporary bonding surface of the metal plate, such as degreasing, sandblasting, etching, various plating processes, or plasma treatment with silane coupling agents. Furthermore, the surface roughness of the temporary bonding surface of the metal plate, measured in ten-point average roughness (Rzjis), is preferably 20 μm or less, more preferably 0.1 μm to 20 μm. When the roughness is less than 0.1 μm, it can sometimes become difficult to ensure sufficient adhesion to the ceramic-resin composite sheet. Conversely, when the roughness exceeds 20 μm, defects are easily generated at the bonding interface, becoming a major cause of reduced voltage resistance and adhesion.

[0094] <Temporary bonding method for metal sheets>

[0095] In embodiments of the present invention, temporary bonding of the metal plate and the ceramic resin composite can be performed at a temperature ranging from 0°C to 40°C, preferably at room temperature without substantial heating. It should be noted that, in this specification, "room temperature" refers to the temperature range specified in JIS Z 8703:1983, i.e., 5°C to 35°C. During temporary bonding, a liquid compound containing active hydrogen (hereinafter also referred to as "liquid compound") within the above-mentioned temperature range is applied to at least one side of either the ceramic resin composite or the metal plate. The two surfaces are then brought together, and pressure is applied while the liquid compound evaporates. That is, after temporary bonding, the liquid compound is substantially not present at the bonding interface. This method allows the liquid compound to have weak adhesion to cyanate esters, which is beneficial for temporary bonding. It should be noted that when the temperature during temporary bonding is below 0°C, a portion of the liquid compound is below its melting point and therefore solidifies, which is detrimental to temporary bonding and is therefore not preferred. Furthermore, at temperatures exceeding 40°C, a portion of the aforementioned liquid compound will immediately evaporate, losing its weak adhesive properties, which is therefore undesirable. Additionally, the pressure used for temporary bonding is preferably 0.1 MPa or higher and 250 MPa or lower, more preferably 30 MPa or lower. If the pressure is too high (e.g., exceeding 250 MPa), the ceramic sintered body may be damaged during pressing. If the pressure is too low (e.g., below 0.1 MPa), the aforementioned liquid compound will not penetrate to the bonding interface, and no adhesive properties will be generated. Furthermore, the time taken for temporary bonding is preferably the time taken for the aforementioned liquid compound to evaporate, for example, preferably 10 minutes or more.

[0096] <Types of liquid compounds containing active hydrogen>

[0097] The types of liquid compounds containing active hydrogen can be selected from a wide range, including compounds with hydroxyl, amino, or carboxyl groups within their molecules. Examples include alcohols, amines, and carboxylic acids. Within this range, silane-based and titanate-based coupling agents having these functional groups are also included. In a preferred embodiment, alcohols with 1 to 10 carbon atoms, such as methanol, ethanol, or phenol, can be used as the liquid compound, with methanol or ethanol being more preferably used. For temporary bonding, it is preferable that the liquid compound is volatile in the temperature range of 0°C to 40°C or at room temperature.

[0098] Example

[0099] The present invention will be described in more detail below with examples and comparative examples.

[0100] [Success or failure of temporary bonding: Examples 1-10, Comparative Examples 1-5]

[0101] <Fabrication of Ceramic-Resin Composite Sheets>

[0102] Thermosetting resins were impregnated into ceramic sintered bodies using the combinations shown in Table 1. Ceramic resin composite sheets were then fabricated using a multi-wire saw (SW1215, Yasunaga). It should be noted that cyanate A in Table 1 uses bismaleimide triazine resin (BT2160, Mitsubishi Gas Chemical), cyanate B uses NOVOLAC type cyanate resin (PT-30, Lonza), cyanate C uses bisphenol A type cyanate resin (CYTESTERTA, Mitsubishi Gas Chemical), cyanate D uses NOVOLAC type cyanate resin and difunctional naphthalene type epoxy resin (HP-4032D, DIC), and cyanate E uses NOVOLAC type cyanate resin and 4,4'-diphenylmethane type bismaleimide resin (BMI, K.I. Chemical Industry Co., LTD.). The epoxy resin shown in Table 1 is a difunctional naphthalene-type epoxy resin (HP-4032D, manufactured by DIC Corporation), and the silicone is KR311 (manufactured by Shin-Etsu Chemical Co., Ltd.). The ceramic sintered body described above was manufactured by pressing using a CIP (cold isostatic pressing) apparatus (“ADW800”, manufactured by Kobe Steel Co., Ltd.) and then sintering using an intermittent high-frequency furnace (“FTH-300-1H”, manufactured by Fuji Denpa Kogyo Co., Ltd.). Furthermore, the impregnation of the thermosetting resin was performed using a vacuum heating impregnation apparatus (“G-555AT-R”, manufactured by Kyosin Engineering Corporation) and a pressurized heating impregnation apparatus (“HP-4030AA-H45”, manufactured by Kyosin Engineering Corporation). Additionally, after the ceramic-resin composite was manufactured, further heating was applied to control the curing rate of the thermosetting resin to the values ​​shown in Table 1. The curing rate of the thermosetting resin composition was determined using a DSC6200R (manufactured by Seiko Instruments Inc.) as a differential scanning calorimeter.

[0103] <Preparation of Temporary Adhesives>

[0104] Using a copper plate with a ten-point average roughness of 10 μm as the metal plate, and employing the pressure and solvent shown in Table 1, a temporary bond was fabricated at room temperature using a press (equipment name: MHPC-VF-350-350-1-45, manufactured by Meiki Seisakusho). The ambient pressure was atmospheric. The pressurization time required for the temporary bond was set to 10 minutes. Additionally, a liquid compound containing active hydrogen, used as a solvent, was applied to the surface of the ceramic-resin composite at room temperature until no liquid accumulation occurred. Even with a large amount of the aforementioned solvent, except for the portion that seeps to the interface, all of it will leak out to the outside of the bonded surface through pressing, thus preventing any problems.

[0105] <Determining whether a temporary adhesive can be made>

[0106] To determine whether a temporary bond can be formed, the tensile shear bond strength is determined according to JIS K 6850:1999. Specifically, the metal plate of the temporary bond is held in a Tensilon testing machine (manufactured by Toyo Baldwin Co., Ltd.), and the tensile speed is set to 50 mm / s. Samples with a tensile shear bond strength of 0.1 MPa or higher after this test are considered suitable for temporary bonding. This is because if the tensile shear bond strength is less than 0.1 MPa, the following phenomena will occur: the ceramic-resin composite will peel off when the sample is turned over; the sample will peel off during the tensile shear bond strength test, making the test impossible; and the ceramic-resin composite will peel off during transportation. It should be noted that for the existing process involving the integration of the interface between the ceramic-resin composite and the metal plate to remove air before bonding (formal bonding), the shear bond strength at the interface is usually less than 0.1 MPa, therefore it does not meet the requirements for temporary bonding as described above. Furthermore, the shear bond strength of a temporary bonding interface is actually no higher than that of a formal bonding interface based on pressure and heat.

[0107] <Example 1>

[0108] In Example 1, cyanate ester A was used as the thermosetting resin, the resin curing rate was set to 15%, ethanol was used as the solvent, copper plate was used as the metal plate, and the applied pressure was set to 2 MPa. The tensile shear bond strength of the resulting temporary adhesive was 0.30 MPa.

[0109] <Example 2>

[0110] The difference from Example 1 is that the applied pressure was set to 0.1 MPa. The tensile shear bond strength of the resulting temporary adhesive was 0.27 MPa.

[0111] <Example 3>

[0112] The difference from Example 1 is that the applied pressure was set to 250 MPa. The tensile shear bond strength of the resulting temporary bond was 0.32 MPa.

[0113] <Example 4>

[0114] The difference from Example 1 is that methanol was used as the solvent. The tensile shear bond strength of the resulting temporary adhesive was 0.30 MPa.

[0115] <Example 5>

[0116] The difference from Example 1 is that methanol was used as the solvent and the applied pressure was set to 20 MPa. The tensile shear bond strength of the resulting temporary bond was 0.29 MPa.

[0117] <Example 6>

[0118] The difference from Example 1 is that the curing rate of the thermosetting resin was set to 50%. The tensile shear bond strength of the resulting temporary adhesive was 0.31 MPa.

[0119] <Example 7>

[0120] The difference from Example 1 is that the thermosetting resin was cyanate ester B, and the resin curing rate was set to 40%. The tensile shear bond strength of the resulting temporary adhesive was 0.32 MPa.

[0121] <Example 8>

[0122] The difference from Example 1 is that the thermosetting resin was cyanate ester C, and the resin curing rate was set to 45%. The tensile shear bond strength of the resulting temporary adhesive was 0.33 MPa.

[0123] <Example 9>

[0124] The difference from Example 1 is that the thermosetting resin was cyanate ester D, and the resin curing rate was set to 35%. The tensile shear bond strength of the resulting temporary adhesive was 0.29 MPa.

[0125] <Example 10>

[0126] The difference from Example 1 is that the thermosetting resin was cyanate ester E, and the resin curing rate was set to 40%. The tensile shear bond strength of the resulting temporary adhesive was 0.27 MPa.

[0127] <Comparative Example 1>

[0128] The difference from Example 1 is that the resin curing rate was set to 25%, and the solvent was acetone, which does not contain active hydrogen. The shear bond strength was 0 MPa (unbonded).

[0129] <Comparative Example 2>

[0130] The difference from Example 1 is that the resin curing rate was set to 80%. The shear bond strength was 0.02 MPa.

[0131] <Comparative Example 3>

[0132] The difference from Example 1 is that the thermosetting resin is an epoxy resin without cyanate groups, and the resin curing rate is set to 30%. The shear bond strength is 0 MPa (unbonded).

[0133] <Comparative Example 4>

[0134] The difference from Example 1 is that the thermosetting resin is a silicone without cyanate groups, and the resin curing rate is set to 20%. The shear bond strength is 0 MPa (unbonded).

[0135] <Comparative Example 5>

[0136] The difference from Example 1 is that no solvent was used, and the resin curing rate was set to 25%. The shear bond strength was 0 MPa (unbonded).

[0137] Furthermore, regarding all examples and comparative examples involving temporary bonding without heating, it was confirmed that the curing rate of the thermosetting resin differed from that before and after temporary bonding by only a measurement error considered to be less than 2%, and the thermosetting resin did not substantially change due to temporary bonding. Based on the above results, it can be understood that to achieve temporary bonding, a thermosetting resin with cyanate ester groups must be used with a curing rate of 5.0% to 70%, and a liquid compound with active hydrogen must be used as a solvent.

[0138] [Table 1]

[0139]

[0140] [Confirmation of transportation reliability: Examples A and B, Comparative Examples A and B]

[0141] The reliability of transport was confirmed using temporary adhesives prepared based on the above embodiments and conventional ceramic resin composite sheets. For transport, a 2500 km journey, classified as the most severe transport condition, was conducted based on the test classification of JIS Z 0232:2004. For the ceramic resin composite sheets used as transport samples, the ceramic resin composite sheets prepared in Example 1 of Table 1 above were used; in Examples A and B, they were used in the form of temporary adhesives, while in Comparative Examples A and B, they were used in the form of individual ceramic resin composite sheets.

[0142] In the first bundling method, the sample is completely wrapped with a first cushioning material (green sheet, mirror pad, etc.) to form a transport body. Then, a second cushioning material (bubble cushioning material, a product obtained by crumpling thick paper, resin sheet, etc.) is used to prevent the transport body from moving within the transport box (corrugated cardboard box, etc.). In the second bundling method, the sample is simply wrapped with the first cushioning material (green sheet, mirror pad, etc.) to form a transport body, which is then directly placed in the transport box. That is, in the second bundling method, only the first cushioning material and the transport box itself provide cushioning; the impact from transportation is greater than in the first bundling method, but transportation can be carried out using a simpler method.

[0143] The structure shown in Table 2 below was transported for 2500 km. After transport, a formal bonding based on heating and pressurization was performed, and the thermal resistance characteristics of the formal bond were measured and compared. The formal bond was manufactured as follows: using a vacuum heating press ("MHPC-VF-350-350-1-45", manufactured by Meiki Seisakusho Co., Ltd.), under conditions of 5 MPa pressure, 240°C heating temperature, and 5 hours heating time, a 1.0 mm thick copper plate with the same external dimensions as the sheet was pressed and bonded to both sides of the ceramic resin composite sheet (comparative example) or the exposed surface of the ceramic resin composite sheet of the temporary bond (example). The thermal resistance characteristics (including its interfacial thermal resistance) of the laminate containing insulating material, heat sink, and cooler (not just as a separate insulating material) were measured, and the transient thermal resistance value was measured. Specifically, the time change (time history) until the measured value of the chip temperature tends to a basically constant value when the chip is heated to a certain amount of heat is applied to the heater chip was measured. The device used to measure the time change of the measured chip temperature Ta is the "T3Ster" manufactured by Mentor Graphics Corporation.

[0144] <Example A>

[0145] In Example A, the transport body includes a temporary adhesive and is packaged using a first bundling method. The thermal resistance value of the final adhesive obtained by processing the temporary adhesive after transport is used as a reference.

[0146] <Example B>

[0147] The difference from Example A is that the second bundling method was used, and the relative value of the thermal resistance of the final adhesive was 110%, which, although slightly deteriorated, was within acceptable limits.

[0148] <Comparative Example A>

[0149] The difference from Example A is that the state during transportation is a separate ceramic resin composite sheet. The thermal resistance of the formal adhesive is 130% relative to that of Example A, indicating that deterioration occurred by transporting it as a separate ceramic resin composite sheet.

[0150] <Comparative Example B>

[0151] The difference from Example A is that the ceramic resin composite sheet is transported as a separate sheet and a second bundling method is used. The thermal resistance of the final adhesive is 150% relative to that of Example A, indicating a significant increase in thermal resistance and severe deterioration.

[0152] [Table 2]

[0153]

[0154] [Physical properties of objects that were temporarily bonded and then formally bonded: Examples 1-1 to 3-1, Comparative Examples 1-1 and 1-2]

[0155] The effect of temporary bonding on the final bond was evaluated. After temporary bonding under the conditions shown in Table 3 below, a copper plate with a width × length × thickness of 25 mm × 12.5 mm × 1.0 mm was pressed and bonded to the exposed surface of a ceramic resin composite sheet with a width × length × thickness of 25 mm × 12.5 mm × 320 μm using a vacuum heating press ("MHPC-VF-350-350-1-45", manufactured by Meiki Seisakusho Co., Ltd.). This process was used to produce the final bond. In the comparative example, the temporary bonding conditions were also set to heating and pressure for comparison.

[0156] <Determination of the thermal conductivity of formal adhesives>

[0157] The test specimens were tested using a standard adhesive, according to JIS H 8453:2010. The testing instrument used was an ADVANCERIKO, Inc. "TC-1200RH".

[0158] <Determination of Tensile Shear Strength of Formal Adhesives>

[0159] For the bonded joints, tensile shear bond strength was determined according to JIS K 6850:1999. The testing apparatus was an Autograph ("AG-100kN", manufactured by Shimadzu Corporation), and the test was conducted under the conditions of a test temperature of 25°C and a crosshead speed of 5.0 mm / min.

[0160] <Example 1-1>

[0161] In Examples 1-1, a temporary adhesive was prepared under the conditions of Example 1 in Table 1 above (ethanol coating, room temperature, pressing at 2 MPa, 10 minutes). The final adhesive was prepared by pressing and bonding under conditions of 5 MPa pressure, 240°C heating temperature, and 5 hours heating time. The thermal conductivity and tensile shear bond strength of this final adhesive were used as benchmark values ​​for comparison with other examples and comparative examples.

[0162] <Example 2-1>

[0163] The difference from Examples 1-1 is that the conditions for preparing the temporary adhesive were those of Example 3 in Table 1 (ethanol coating, room temperature, pressing at 250 MPa for 10 minutes). The thermal conductivity and tensile shear strength after formal bonding were not significantly different from those of Examples 1-1.

[0164] <Example 3-1>

[0165] The difference from Examples 1-1 is that the conditions for preparing the temporary adhesive were those of Example 4 in Table 1 (methanol coating, room temperature, pressing at 2 MPa for 10 minutes). The thermal conductivity and tensile shear strength after formal bonding were not significantly different from those of Examples 1-1.

[0166] <Comparative Example 1-1>

[0167] The difference from Example 1-1 is that, under conditions of 5 MPa pressure, 240°C heating temperature, and 5 hours heating time, a vacuum heating press was used for temporary bonding. The thermal conductivity and tensile shear strength of the bonded bond after formal bonding were significantly worse than those of Example 1-1. This demonstrates that once bonding is performed through heating and pressurization, it is impossible to re-bond without deteriorating the physical properties.

[0168] <Comparative Examples 1-2>

[0169] The difference from Example 1-1 is that, under conditions of 5 MPa pressure, 240°C heating temperature, and 5 hours heating time, a vacuum heating press was used for temporary bonding, followed by formal bonding under conditions of ethanol coating, room temperature, and 2 MPa for 10 minutes. After formal bonding, the metal plate and the ceramic resin composite sheet did not bond. This demonstrates that even changing the order of the temporary and formal bonding does not improve functionality.

[0170]

Claims

1. A ceramic-metal temporary adhesive, comprising: A ceramic-resin composite is formed by impregnating a thermosetting resin composition having cyanate ester groups into a non-oxide ceramic sintered body in such a manner that the semi-cured curing rate, calculated by differential scanning calorimetry, is 5.0% or more and 70% or less; and A metal plate, which is temporarily bonded to at least one side of the ceramic resin composite. The temporary bonding refers to bonding the ceramic resin composite to the metal plate under a compressive load of 250 MPa or less at a temperature in the range of 0 to 40°C and in the presence of a liquid compound containing active hydrogen, without heating the thermosetting resin composition impregnated in the ceramic resin composite to prevent modification of the thermosetting resin composition, wherein the shear bond strength between the ceramic resin composite and the metal plate is 0.1 MPa or more and 1.0 MPa or less.

2. The ceramic-metal temporary adhesive as described in claim 1, wherein, The metal plate is in the temporary bonded state only on one side of the ceramic resin composite.

3. A transport body, which is formed by wrapping the ceramic-metal temporary adhesive as described in claim 1 or 2 with packaging material.

4. A method for manufacturing the ceramic-metal temporary adhesive according to claim 1 or 2, comprising the following steps: The step of impregnating a thermosetting resin composition having cyanate groups into a non-oxide ceramic sintered body in such a way that the curing rate of the semi-cured material calculated by differential scanning calorimetry is 5.0% or more and 70% or less, thereby obtaining a ceramic resin composite. The steps of coating a liquid compound containing active hydrogen onto at least one side of the ceramic resin composite or a metal plate with a ten-point average roughness of less than 20 μm; and The steps involve bonding the ceramic resin composite to the metal plate, then applying a compressive load of 250 MPa or less at a temperature ranging from 0°C to 40°C to temporarily bond the ceramic resin composite to the metal plate without modifying the thermosetting resin composition impregnated in the ceramic resin composite, so that the shear bond strength between the ceramic resin composite and the metal plate is 0.1 MPa or more and 1.0 MPa or less.

5. A method for transporting a ceramic-metal temporary adhesive, comprising: The step of storing the transport body as described in claim 3 in a transport container; and The steps for transporting the transport container.

6. The transportation method as claimed in claim 5, wherein the transport body and the cushioning material are housed together in a transport box, thereby making the ceramic-metal temporary adhesive substantially immobile within the transport box.

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