TWI906686B - High thermal conductive metal substrate and preparation method thereof - Google Patents

Abstract

Provided is a high thermal conductive metal substrate, including: a thermal conductive adhesive layer with a thickness of 5 to 100 microns; an insulating layer formed on the thermal conductive adhesive layer and having a thickness of 1 to 150 microns; and a copper foil layer with a thickness of 9 to 210 microns formed on the insulating layer, so that the insulating layer is between the thermal conductive adhesive layer and the copper foil layer, wherein the insulating layer includes 50 to 95 wt% of a resin with imide structures in the polymer backbone, 0 to 25 wt% of an epoxy resin, 0 to 25 wt% of an inorganic filler and 0 to 10 wt% of a catalyst, based on the total weight of the solid content of the insulating layer.

Description

High thermal conductivity metal substrate and its preparation method

This invention relates to a high thermal conductivity metal substrate coated with thermoplastic resin, and more particularly to a high thermal conductivity metal substrate with high heat dissipation efficiency and its manufacturing method.

Traditional heat dissipation materials, due to the need to consider insulation properties, require a thermal conductivity of 3 W/(m*k) and a breaking voltage of 7 to 10 kV. This necessitates an adhesive thickness of 120 to 150 μm or even higher to meet insulation requirements, resulting in a large overall product thickness. Insufficient thickness leads to unsatisfactory heat dissipation and insulation performance. Furthermore, while heat dissipation models using TPI (thermoplastic polyimide) doped with heat dissipation powder can reduce product thickness to some extent and still meet insulation requirements, the high processing temperature (above 350°C) required for TPI processing results in high costs, hindering effective mass production. While stretching methods can produce polyimide films with satisfactory insulation properties, the resulting thickness and high thermal resistance necessitate a sufficiently thick thermally conductive adhesive layer to ensure adequate heat dissipation. To reduce film thickness and improve thermal resistance, polyimide film manufacturers employ thinner designs. However, when the thickness is designed to be 5 to 7.5 μm, the mechanical strength is poor and the film is too thin, making downstream processing difficult, resulting in low yields and increased costs, failing to meet industry standards. Therefore, developing products with good resistance to voltage penetration, excellent heat dissipation, and reduced overall thickness, and producing high thermal conductivity metal substrates through simplified processes, has become an urgent problem to solve.

To solve the above-mentioned technical problems, the present invention provides a high thermal conductivity metal substrate, comprising: a thermally conductive adhesive layer with a thickness of 5 to 150 micrometers, wherein the material forming the thermally conductive adhesive layer includes a resin material and a thermally conductive powder; an insulating layer with a thickness of 1 to 150 micrometers formed on the thermally conductive adhesive layer; and an insulating layer with a thickness of 9 to 210 micrometers formed on the insulating layer. A copper foil layer of micrometers is used to position the insulating layer between the thermally conductive adhesive layer and the copper foil layer. The insulating layer, by weight of its solid content, comprises: 50 to 95 wt% of a polymer backbone having a amide structure; 0 to 25 wt% of an epoxy resin; 0 to 25 wt% of an inorganic filler; and 0 to 10 wt% of a catalyst.

In one specific embodiment, the insulating layer of the high thermal conductivity metal substrate may include multiple insulator layers.

In one specific embodiment, the resin having a nimidyl structure in the polymer backbone of the high thermal conductivity metal substrate includes polynimidyl resin or polyamide-nimidyl resin.

In one specific embodiment, the polyimide resin of the high thermal conductivity metal substrate is obtained by polymerization of monomers containing diamine and acid anhydride, and the polyamide-imide resin is obtained by polymerization of monomers containing diamine, acid anhydride, and isocyanate compounds.

In a specific embodiment, the diamine is selected from 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB), 2,2-bis(4-aminophenoxy)hexafluoropropane, 4,4'-diaminodiphenyl ether, bis[4-(3-aminophenoxy)phenyl]sulfonamide, bis[4-(4-aminophenoxy)phenyl]sulfonamide, At least one of the group consisting of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(4-aminophenoxy)phenyl]methane, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ethyl ether, bis[4-(4-aminophenoxy)phenyl]one, 1,3-bis(4-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene.

In a specific embodiment, the anhydride is selected from at least one of the following groups: hexafluorodianhydride (6FDA), bicyclic [2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, 1,2-ethylenedi[1,3-dihydro-1,3-dioxoisobenzofuran-5-carboxylate], 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, phenyltetracarboxylic acid dianhydride, trimellitic anhydride (TMA), and cis-aconitine anhydride.

In a specific embodiment, the isocyanate compound is selected from at least one of the group consisting of 4,4'-diphenylmethane diisocyanate (MDI), 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, naphthalene-1,5-diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and lysine diisocyanate.

In a specific embodiment, the molar ratio of diamine to acid anhydride in the polyamide-imide resin is from 1:2.05 to 1:2.20.

In a specific embodiment, the molar ratio of diamine to acid anhydride in the polyimide resin is from 1:0.90 to 1:1.10.

In a specific embodiment, the molar ratio of diamine to isocyanate in the polyamide-imide resin is from 1:1.00 to 1:1.50.

In a specific embodiment, the epoxy resin serves as a crosslinking agent and is selected from at least one of the group consisting of glycidylamine type epoxy resins, glycidyl ester type epoxy resins, epoxide olefin compounds, alicyclic epoxy resins, polyphenolic glycidyl ether epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, aliphatic glycidyl ether epoxy resins, heterocyclic epoxy resins, and mixed epoxy resins.

In a specific embodiment, the catalyst is selected from at least one of the group consisting of 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazole.

In a specific embodiment, the inorganic filler is selected from at least one of the group consisting of calcium sulfate, carbon black, silicon dioxide, titanium dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, talc, aluminum nitride, glass powder, quartz powder, and clay.

In one specific embodiment, the inorganic filler is a powder with a particle size of 0.5 micrometers to 10 micrometers.

In a specific embodiment, the material forming the thermally conductive adhesive layer includes a resin material and a thermally conductive powder. The resin material is independently selected from at least one of the group consisting of epoxy resins, acrylic resins, carbamate resins, silicone rubber resins, parylene resins, bismaleimide resins, and polyimide resins. The thermally conductive powder is independently selected from at least one of the group consisting of zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, talc, aluminum nitride, glass powder, graphite, and graphene.

In a specific embodiment, the thermally conductive powder content of the high thermal conductivity metal substrate is 10 to 75 wt% based on the total solid content of the thermally conductive adhesive layer, and its particle size is 0.5 to 10 micrometers.

In one specific embodiment, the high thermal conductivity metal substrate further includes a metal plate formed on the thermally conductive adhesive layer, with the thermally conductive adhesive layer positioned between the insulating layer and the metal plate. In one specific embodiment, the metal plate is preferably made of aluminum.

The present invention also provides a method for preparing a high thermal conductivity metal substrate, comprising: coating a clear varnish layer on a copper foil layer, wherein, based on the total weight of the solid content of the clear varnish layer, the clear varnish layer comprises 50 to 95 wt% of a polymer backbone having a amide structure; 0 to 25 wt% of an epoxy resin; 0 to 25 wt% of an inorganic filler; and 0 to 10 wt% of a catalyst; The varnish layer is cured at a temperature range of 50 to 180°C to obtain an insulating layer. If necessary, after curing the varnish layer, the steps of applying and curing the varnish layer are repeated at least once to obtain an insulating layer comprising multiple insulator layers. The insulating layer and the metal plate are then pressed together by contacting the metal plate with a thermally conductive adhesive layer, such that the thermally conductive adhesive layer is positioned between the insulating layer and the metal plate.

In one specific embodiment, the step of laminating the metal plate includes bringing the metal plate with the thermally conductive adhesive layer formed on its surface into contact with the insulating layer and then laminating it, or first applying the thermally conductive adhesive layer onto the insulating layer and then laminating the metal plate.

In one specific embodiment, the method for preparing the high thermal conductivity metal substrate is carried out at 170 to 190°C and a pressure of 30 to 40 kgf/ ^cm² for 50 to 180 minutes.

The high thermal conductivity metal substrate prepared according to the present invention has at least the following advantages:

I. A coated polyimide varnish layer replaces the conventional stretching method for producing polyimide films. This polyimide varnish layer can be multi-layered and combined with variations in resin ratios or powder doping, as well as adjustments to powder content and particle size, to obtain an insulating layer with multiple advantages, including high insulation, high flame retardancy, high thermal conductivity, and high mechanical properties. Compared to films produced by the casting process, the varnish-type insulating layer exhibits better dimensional stability due to the absence of residual stress from the stretching process. Furthermore, the varnish-type insulating layer is directly formed on the carrier film in thin-film applications, making it easier to balance various properties and meet the requirements of downstream processing.

II. The process of this invention involves directly coating a polyimide varnish layer onto copper. This not only simplifies the process and results in a thinner overall thickness, but also allows for direct slitting and pressing. After coating and rapid pressing, large-width manufacturing is possible without the need for curing or slitting processes. Therefore, this process offers advantages such as improved yield, reduced waste, increased efficiency, and cost savings.

Thirdly, in terms of appearance, when using a black polyimide varnish layer, this invention can solve appearance problems such as fisheye caused by the thermally conductive adhesive layer, and further improve common appearance defects of conventional coatings by applying multiple coats of varnish.

IV. The polyimide varnish layer in this invention exhibits strong adhesion between itself, the copper foil layer, and the thermally conductive adhesive layer. Its thinness does not affect flatness, resulting in excellent insulation.

V. The high thermal conductivity metal substrate produced by the process of this invention is manufactured using a simple process, which reduces costs. The polyimide varnish layer used does not require high-temperature cyclization dehydration for curing and simultaneously possesses excellent insulation properties and heat dissipation effects, resulting in a thinner overall product, higher heat dissipation efficiency, and improved insulation resistance to high voltage breakdown.

100: High thermal conductivity metal substrate

101: Thermally conductive adhesive layer

102: The Insulation Layer

1020: Insulation layer

103: Copper Foil Layer

104: Metal Plate

The embodiments of the present invention are illustrated with illustrative reference figures:

Figure 1 is a schematic structural diagram of one embodiment of the high thermal conductivity metal substrate of the present invention.

The following specific examples illustrate the implementation of this invention. Those familiar with this art can easily understand the advantages and effects of this invention from the content disclosed in this specification.

It should be understood that the structures, proportions, and sizes shown in the accompanying drawings are solely for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein. They are not intended to limit the implementation of this invention and therefore have no substantive technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, provided they do not affect the effectiveness or purpose of this invention, should still fall within the scope of the technical content disclosed herein. Similarly, the use of terms such as "a," "above," and "below" in this specification is merely for clarity and not intended to limit the scope of implementation of this invention. Changes or adjustments to their relative relationships, without substantively altering the technical content, should also be considered within the scope of implementation of this invention. In addition, all ranges and values herein are inclusive and combinable. Any value or point that falls within the range described in this article, such as any integer, can be used as a minimum or maximum value to derive a lower range, etc.

As shown in Figure 1, the present invention provides a method for preparing a high thermal conductivity metal substrate 100, which includes: coating a clear varnish layer on a copper foil layer 103, wherein, based on the total weight of the solid content of the clear varnish layer, the clear varnish layer contains 50 to 95 wt% of a polymer backbone having a amide structure; 0 to 25 wt% of an epoxy resin; 0 to 25 wt% of an inorganic filler; and 0 to 10 wt% of a catalyst; and the coating is applied at a temperature range of 50 to 180°C. At 0°C, the varnish layer is cured to obtain an insulating layer 102. If necessary, after curing the varnish layer, the steps of applying the varnish layer and curing are repeated at least once to obtain an insulating layer 102 comprising a plurality of insulator layers 1020. Then, a thermally conductive adhesive layer 101 is applied to the insulating layer 102 and the metal plate 104 to press the metal plate 104 together, such that the thermally conductive adhesive layer 101 is positioned between the insulating layer 102 and the metal plate 104.

In a specific embodiment, as shown in FIG1, a metal plate 104 with a thermally conductive adhesive layer 101 formed on its surface is brought into contact with an insulating layer 102, or a thermally conductive adhesive layer 101 is coated on the insulating layer 102 and brought into contact with the metal plate 104, and ^{the two} are pressed together for 50 to 180 minutes at a temperature of, for example, 170 to 190°C and a pressure of 30 to 40 kgf/cm², with the thermally conductive adhesive layer 101 positioned between the insulating layer 102 and the metal plate 104. In a specific embodiment, the pressing temperature may be 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189 or 190℃; the pressing pressure may be 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 or 40 kgf/ ^cm² ; and the pressing time may be 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170 or 180 min.

In a specific embodiment, as shown in FIG1, the high thermal conductivity metal substrate of the present invention is obtained by the manufacturing method of the present invention. Accordingly, the high thermal conductivity metal substrate 100 includes: a thermally conductive adhesive layer 101 with a thickness of 5 to 150 micrometers; an insulating layer 102 formed on the thermally conductive adhesive layer 101 with a thickness of 1 to 150 micrometers; and a copper foil layer 103 formed on the insulating layer 102 with a thickness of 9 to 210 micrometers, such that the insulating layer 102 is located on the... Between the thermally conductive adhesive layer 101 and the copper foil layer 103, the insulating layer 102, by weight of its solid content, comprises: 50 to 95 wt% of a polymer backbone having a amide structure; 0 to 25 wt% of an epoxy resin; 0 to 25 wt% of an inorganic filler; and 0 to 10 wt% of a catalyst. In another specific embodiment, the high thermal conductivity metal substrate 100 of the present invention further includes a metal plate 104 formed on the thermally conductive adhesive layer 101, such that the thermally conductive adhesive layer 101 is located between the insulating layer 102 and the metal plate 104. In some specific embodiments, the metal plate 104 is preferably made of aluminum.

In another specific embodiment, the insulating layer of the high thermal conductivity metal substrate of the present invention may include a plurality of insulating sublayers, and the total thickness of the insulating layer is 1 to 150 micrometers.

In some specific embodiments, the thickness of the thermally conductive adhesive layer can be 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, or 150 micrometers.

In some specific embodiments, the thickness of the insulation layer can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150 micrometers.

In some specific embodiments, the thickness of the copper foil layer can be 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, 200, 205, or 210 micrometers.

In some specific embodiments, the content of resins with amide structures in the polymer backbone of the insulation layer can be 50, 55, 60, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 90, or 95 wt%.

In some specific embodiments, the epoxy resin content in the insulation layer can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, or 25 wt%.

In some specific embodiments, the content of inorganic filler in the insulation layer can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, or 25 wt%.

In some specific embodiments, the catalyst content in the insulating layer may be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 wt%.

In one specific embodiment, the resin having a nimidyl structure in the polymer backbone of the high thermal conductivity metal substrate includes polynimidyl resin or polyamide-nimidyl resin.

In one specific embodiment, the polyimide resin of the high thermal conductivity metal substrate is obtained by polymerization of monomers containing diamine and acid anhydride, and the polyamide-imide resin is obtained by polymerization of monomers containing diamine, acid anhydride, and isocyanate compounds.

In some specific embodiments, the polyimide resin or polyamide-imide resin composition may include 0 to 3 wt% of a catalyst, for example, 0, 1, 2, or 3 wt% of a catalyst. In some specific embodiments, the catalyst is a tertiary amine selected from at least one of the group consisting of triethylamine, isoquinoline, pyridine, N-ethylpiperidine, and benzimidazole.

In some specific embodiments, the polyimide resin or polyamide-imide resin is soluble in a solvent for coating a varnish layer. The solvent, for example, is soluble in at least one solvent selected from the group consisting of N-methylpyrrolidone, γ-butyrolactone, cyclohexanone, acetone, butanone, N,N-dimethylformamide, N,N-dimethylacetamide, pyridine, cyclohexane, dichloromethane, tetrahydrofuran, ethyl acetate, acetonitrile, 1,2-dichloroethane, trichloroethylene, triethylamine, 4-methyl-2-pentanone, toluene, or xylene.

In a specific embodiment, the diamine is selected from 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB), 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminodiphenyl ether, bis[4-(3-aminophenoxy)phenyl]sulfonamide, bis[4-(4-aminophenoxy)phenyl]sulfonamide, 2 At least one of the group consisting of 2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(4-aminophenoxy)phenyl]methane, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ethyl ether, bis[4-(4-aminophenoxy)phenyl]one, 1,3-bis(4-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene.

In a specific embodiment, the anhydride is selected from at least one of the following groups: hexafluorodianhydride (6FDA), bicyclic [2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, 1,2-ethylenedi[1,3-dihydro-1,3-dioxoisobenzofuran-5-carboxylate], 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, phenyltetracarboxylic acid dianhydride, trimellitic anhydride (TMA), and cis-aconitine anhydride.

In a specific embodiment, the isocyanate compound is selected from at least one of the group consisting of 4,4'-diphenylmethane diisocyanate (MDI), 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, naphthalene-1,5-diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and lysine diisocyanate.

In a specific embodiment, the molar ratio of the diamine to the acid anhydride in the polyamide-imide resin is from 1:2.05 to 1:2.20. For example, 1:2.05, 1:2.06, 1:2.07, 1:2.08, 1:2.09, 1:2.10, 1:2.11, 1:2.12, 1:2.13, 1:2.14, 1:2.15, 1:2.16, 1:2.17, 1:2.18, 1:2.19, or 1:2.20.

In a specific embodiment, the molar ratio of diamine to acid anhydride in the polyimide resin is from 1:0.90 to 1:1.10. For example, 1:0.90, 1:0.91, 1:0.92, 1:0.93, 1:0.94, 1:0.95, 1:0.96, 1:0.97, 1:0.98, 1:0.99, 1:1.00, 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07, 1:1.08, 1:1.09, or 1:1.10.

In a specific embodiment, the molar ratio of diamine to isocyanate in the polyamide-imide resin is from 1:1.05 to 1:1.50. For example, ratios of 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45, or 1:1.50.

In a specific embodiment, the epoxy resin is selected from at least one of the group consisting of glycidylamine type epoxy resins, glycidyl ester type epoxy resins, epoxide olefin compounds, alicyclic epoxy resins, polyphenolic glycidyl ether epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, aliphatic glycidyl ether epoxy resins, heterocyclic epoxy resins, and mixed epoxy resins.

In a specific embodiment, the catalyst is selected from at least one of the group consisting of 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazole.

In a specific embodiment, the inorganic filler is selected from at least one of the group consisting of calcium sulfate, carbon black, silicon dioxide, titanium dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, talc, aluminum nitride, glass powder, quartz powder, and clay.

In one specific embodiment, the inorganic filler is a powder with a particle size of 0.5 to 10 micrometers. For example, the powder has a particle size of 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 micrometers.

In a specific embodiment, the material forming the thermally conductive adhesive layer includes a resin material and a thermally conductive powder; wherein the resin material is at least one independently selected from the group consisting of epoxy resin, acrylic resin, carbamate resin, silicone rubber resin, parylene resin, bismaleimide resin, and polyimide resin; and the thermally conductive powder is at least one independently selected from the group consisting of zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, talc, aluminum nitride, glass powder, graphite, and graphene.

In a specific embodiment, the content of the thermally conductive powder is preferably 10 to 75 wt%, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, or 75 wt%. In a specific embodiment, the particle size of the thermally conductive powder is preferably 0.5 micrometers to 10 micrometers, for example, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 micrometers.

Test Methods

For testing methods of thermal conductivity and thermal resistance, please refer to ASTM D5470.

The testing methods for breaking voltage and dielectric strength are as per ASTM D149.

Dimensional stability testing is performed according to IPC-TM-650 2.2.4C.

Tensile strength, elastic modulus, and elongation were measured according to IPC-TM-650 2.4.19.

Release force testing was conducted according to ASTM D3330.

[Implementation Example]

Preparation Example 1: Synthesis of Polyamide Imide

First, 4.11 g of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) was added to 33 g of N-methylpyrrolidone (NMP), nitrogen gas was introduced, and the mixture was stirred and dissolved at 80 °C. Next, 4.03 g of trimellitic anhydride (TMA) was added, and the reaction was carried out at 80 °C for 1 hour. After adding toluene, the temperature was raised to 170 °C to evaporate the water, and finally, the temperature was raised to 190 °C to remove the toluene. After cooling back to room temperature, 3.00 g of 4,4'-diphenylmethane diisocyanate (MDI) and 0.13 g of triethylamine (Et _3N ) were added, and the reaction was carried out at 120 °C for 3 hours to complete the solution of soluble polyamide-imide.

Preparation Example 2: Synthesis of Polyimide

Under nitrogen purging, monomers were added sequentially to 349 g of NMP at 80 °C, first 32.02 g of 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB), then 21.99 g of hexafluorodianhydride (6FDA) and 12.41 g of bicyclic [2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride (B1317). 6FDA and B1317 were then added in equal proportions, at 5% of the total added amount. The temperature was raised to 150 °C, and 0.80 g of N-ethylpiperidine was added. The reaction was then raised to 190 °C for 4 hours to obtain a soluble polyimide solution.

Preparation Example 3: Preparation of a Coating-Type Varnish Layer

The polyimide and polyamide-imide prepared in Preparation Examples 1 and 2 were respectively mixed with epoxy resin, inorganic filler and catalyst in different proportions to prepare Examples 1 to 8 as shown in Table 1, which were used as coating-type varnish layers. The varnish layer was coated on a copper foil layer and cured at a low temperature of 50 to 180°C to form an insulating layer, resulting in a superimposed coating-type insulating film as shown in Figure 1. Subsequent tests and analyses were conducted on the examples and comparative examples. The epoxy resin used is a dicyclopentadiene phenolic epoxy resin (DCPD, Nan-Ya, EH272H) of the polyphenol type glycidyl ether epoxy resin, and the catalyst is 2-ethyl-4-methylimidazolium (Shikoku Chemical, 2E4MZ-CN). The inorganic filler in Examples 1 to 6 is _SiO2 (D50=0.93μm) (Aduma, P30-C1); the inorganic filler in Examples 7 and 8 is carbon black (D50=3.11μm).

Table 1

Test Example 1: Feature Analysis

As shown in Table 2, Examples 1 to 6, the coating-type insulating film of this invention has a reasonable formulation, resulting in a film with excellent thermal conductivity and insulation properties that is easy to release. Examples 7 and 8, while exhibiting relatively excellent thermal conductivity, show lower insulation properties.

Table 2

Test Example 2: Insulation Properties of Coated Varnish Layers

The polyimide varnish layer of Example 6 in Table 1 was coated onto a PET substrate (DuPont Teijin Films, YGO) and cured at low temperatures of 50 to 180°C to obtain a coated polyimide film. After removing the substrate, corresponding Examples A1 to A3 of different thicknesses were made and compared with commercially available black and yellow polyimide films in terms of breakdown voltage. Comparative Examples B1 to B6 are PIAM GF050 (yellow), PIAM GF030 (yellow), DuPont 20EN (yellow), DuPont 35KBC (black), Damai BK012 (black), and TL012 (yellow), respectively.

As shown in Table 3, the dielectric strength of the coated polyimide film of this invention reaches the level of commercially available yellow polyimide films, and is far superior to commercially available black polyimide films. Furthermore, compared to existing film thickness specifications, it can easily produce thinner films, such as 1 to 5 micrometers.

Table 3

Test Example 3: Characteristic Comparison of High Thermal Conductivity Metal Substrates

Using the coated polyimide films of Examples A1 and A2 in Table 3 as the 5-micron and 8-micron insulation layers in the examples, Examples C1 to C4 were obtained. Comparative Examples D1 and D2 were also made using commercially available polyimide films of Comparative Examples B6 and B4 in Table 3, respectively, to form thermally conductive metal substrates. Comparative Examples D3 and D4 are thermally conductive metal substrates using only a thermally conductive adhesive layer coated on a copper foil layer. The copper foil layer used in the examples and comparative examples is 35-micron (μm) Fukuda CF-TGFB-HTE, and the thermally conductive adhesive layer is 30% acrylic resin (BAP-01) containing 70% boron nitride (D50 = 2.78 μm). The characteristics of the above examples are compared in Table 4. Except for C1, which has a slightly lower breakdown voltage, structures C2 to C4 achieve technical performance indicators that allow the thermal conductivity to approach 3 W/(m*K) and the breakdown voltage to reach 7 to 10 kV. Comparative examples D1 and D2 show that polyimide films used in thermally conductive metal substrates still have shortcomings in terms of thermal conductivity or breakdown voltage. While comparative example D3 still has insufficient breakdown voltage, comparative example D4 shows that a total thickness of 185 micrometers is needed to achieve the technical indicators of a thermal conductivity of 3 W/(m*K) and a breakdown voltage of 7 kV. However, embodiments C3 and C4 can achieve higher breakdown voltages with comparable thermal conductivity.

Table 4

The above embodiments are merely illustrative and not intended to limit the invention. Any person skilled in the art can modify and alter the above embodiments without departing from the spirit and scope of the invention. Therefore, the scope of protection of this invention is defined by the claims attached to this invention, and should be covered by this disclosure as long as it does not affect the effect and purpose of the invention.

100: High thermal conductivity metal substrate

101: Thermally conductive adhesive layer

102: The Insulation Layer

1020: Insulation layer

103: Copper Foil Layer

104: Metal Plate

Claims (20)

A high thermal conductivity metal substrate includes: a thermally conductive adhesive layer with a thickness of 5 to 150 micrometers, wherein the material forming the thermally conductive adhesive layer is composed of a resin material and a thermally conductive powder, wherein the resin material is independently selected from at least one of the group consisting of epoxy resin, acrylic resin, carbamate resin, silicone rubber resin, parylene resin, bismaleimide resin, and polyimide resin, and the thermally conductive powder is independently selected from at least one of the group consisting of zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, talc, aluminum nitride, glass powder, graphite, and graphene, and The thermally conductive powder comprises, by weight of the total solid content of the thermally conductive adhesive layer, 10 to 75 wt%; an insulating layer with a thickness of 1 to 150 micrometers is formed on the thermally conductive adhesive layer; and a copper foil layer with a thickness of 9 to 210 micrometers is formed on the insulating layer, with the insulating layer positioned between the thermally conductive adhesive layer and the copper foil layer. The insulating layer, by weight of the total solid content of the insulating layer, comprises: 50 to 95 wt% of a polymer backbone having a amide structure; 1 to 25 wt% of an epoxy resin; 1 to 25 wt% of an inorganic filler; and 0.02 to 10 wt% of a catalyst. The high thermal conductivity metal substrate as described in claim 1, wherein the insulating layer comprises a plurality of insulator layers. The high thermal conductivity metal substrate as described in claim 1, wherein the resin having a propylene structure in the polymer backbone includes polypropylene resin or polyamide-propylene resin. The high thermal conductivity metal substrate as described in claim 3, wherein the polyimide resin is obtained by polymerization of a monomer comprising a diamine and an anhydride, and the polyamide-imide resin is obtained by polymerization of a monomer comprising a diamine, an anhydride, and an isocyanate compound. The high thermal conductivity metal substrate as described in claim 4, wherein the diamine is selected from 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB), 2,2-bis(4-aminophenoxy)hexafluoropropane, 4,4'-diaminodiphenyl ether, bis[4-(3-aminophenoxy)phenyl]sulfonamide, bis[4-(4-aminophenoxy)phenyl] At least one of the following groups: sulfonamides, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(4-aminophenoxy)phenyl]methane, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ethyl ether, bis[4-(4-aminophenoxy)phenyl]one, 1,3-bis(4-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene. The high thermal conductivity metal substrate as described in claim 4, wherein the anhydride is selected from at least one of the following groups: hexafluorodianhydride (6FDA), bicyclic [2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, 1,2-ethylenedi[1,3-dihydro-1,3-dioxoisobenzofuran-5-carboxylate], 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, phenyltetracarboxylic acid dianhydride, trimellitic anhydride (TMA), and cis-aconitine anhydride. The high thermal conductivity metal substrate as described in claim 4, wherein the isocyanate compound is selected from at least one of the group consisting of 4,4'-diphenylmethane diisocyanate (MDI), 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, naphthalene-1,5-diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and lysine diisocyanate. The high thermal conductivity metal substrate as described in claim 4, wherein in the polyamide-imide resin, the molar ratio of the diamine to the anhydride is from 1:2.05 to 1:2.20. The high thermal conductivity metal substrate as described in claim 4, wherein the molar ratio of the diamine to the anhydride in the polyimide resin is from 1:0.90 to 1:1.10. The high thermal conductivity metal substrate as described in claim 4, wherein in the polyamide-imide resin, the molar ratio of the diamine to the isocyanate is from 1:1.00 to 1:1.50. The high thermal conductivity metal substrate as described in claim 1, wherein the epoxy resin is selected from at least one of the group consisting of glycidylamine type epoxy resins, glycidyl ester type epoxy resins, epoxide olefin compounds, alicyclic epoxy resins, polyphenolic glycidyl ether epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, aliphatic glycidyl ether epoxy resins, and heterocyclic epoxy resins. The high thermal conductivity metal substrate as described in claim 1, wherein the catalyst is selected from at least one of the group consisting of 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazole. The high thermal conductivity metal substrate as described in claim 1, wherein the inorganic filler is selected from at least one of the group consisting of calcium sulfate, carbon black, silicon dioxide, titanium dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, talc, aluminum nitride, glass powder, quartz powder, and clay, and the inorganic filler is a powder with a particle size of 0.5 micrometers to 10 micrometers. The high thermal conductivity metal substrate as described in claim 1, wherein the particle size of the thermally conductive powder is from 0.5 micrometers to 10 micrometers. The high thermal conductivity metal substrate as described in claim 1 further includes a metal plate formed on the thermally conductive adhesive layer, such that the thermally conductive adhesive layer is located between the insulating layer and the metal plate. The high thermal conductivity metal substrate as described in claim 15, wherein the metal substrate is made of aluminum. A method for preparing a high thermal conductivity metal substrate includes: coating a clear varnish layer on a copper foil layer, wherein, based on the total weight of the solid content of the clear varnish layer, the clear varnish layer comprises 50 to 95 wt% of a polymer backbone having a amide structure; 1 to 25 wt% of an epoxy resin; 1 to 25 wt% of an inorganic filler; and 0.02 to 10 wt% of a catalyst; curing the clear varnish layer at a temperature range of 50 to 180°C to obtain an insulating layer; and pressing the metal plate together by contacting the insulating layer and the metal plate with a thermally conductive adhesive layer, such that the thermally conductive adhesive layer is located between the insulating layer and the metal plate. The method for preparing a high thermal conductivity metal substrate as described in claim 17 further includes, after curing the varnish layer, repeating the steps of applying the varnish layer and curing at least once more to obtain an insulating layer comprising a plurality of insulator layers. The method for manufacturing a high thermal conductivity metal substrate as described in claim 17, wherein the step of laminating the metal plate includes contacting and laminating the metal plate on which the thermally conductive adhesive layer is formed on its surface with the insulating layer, or first coating the insulating layer with the thermally conductive adhesive layer and then laminating the metal plate. The method for preparing a high thermal conductivity metal substrate as described in claim 17, wherein the pressing is performed at 170 to 190°C and a pressure of 30 to 40 kgf/ ^cm² for 50 to 180 minutes.