Metal foil laminated resin sheet and method for producing the same

Abstract

To provide a metallic foil laminated resin sheet which can exhibit high thermal conductivity and high peel strength in lamination of a metallic foil and a resin composite material.SOLUTION: A metallic foil laminated resin sheet includes a metallic foil layer, a resin layer, and a resin composite material layer containing a resin matrix and a thermally conductive filler in this order, wherein a thickness of the resin layer is 0.01 μm or more and 1.0 μm or less. The metallic foil laminated resin sheet can be manufactured by laminating a resin composite material layer containing a resin and a thermally conductive filler on the surface of a metallic foil through a resin layer whose thickness is adjusted to 0.01 μm to 1.0 μm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a novel metal foil laminated resin sheet. Specifically, it provides a metal foil laminated resin sheet having high thermal conductivity and high peel strength.

Background Art

[0002] As a substrate material for electronic devices, a metal foil laminated resin sheet in which a metal foil such as a copper foil and a resin composite material are laminated, such as a copper-clad laminate, is used. In particular, in recent years, with the progress of high integration and miniaturization of devices, the heat generation amount has increased. As a countermeasure for heat dissipation from devices, a metal foil laminated resin sheet having high thermal conductivity using a resin composite material containing a thermal conductive filler and a resin matrix is often required.

[0003] In such a metal foil laminated resin sheet, it is important to have a high adhesive force between the metal foil and the resin composite material, and various studies have been conducted to obtain a high peel strength. For example, Patent Document 1 discloses that by forming a primer resin layer on the surface of a copper foil, the peel strength between the copper foil and the resin composite material is improved. Specifically, a primer resin layer (resin precursor layer) with a thickness of 1.5 μm is formed on the surface of the copper foil, and an FR-4 prepreg (a sheet in which a curable epoxy resin has penetrated into a glass woven fabric woven in a cloth shape) is laminated thereon and hot-pressed to produce a copper-clad laminate. Note that the technique of Patent Document 1 is not intended to obtain a copper-clad laminate having high thermal conductivity.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to obtain a resin composite material with high thermal conductivity, it is necessary to use a resin composite material filled with a thermally conductive filler in the resin composite material. However, as a result of investigations by the present inventors, it has been found that when the resin composite material is directly laminated on a metal foil, a high peel strength cannot be obtained. Therefore, an attempt was made to improve the peel strength by forming a resin layer on the surface of the metal foil as in Patent Document 1, but there has been a problem that the thermal conductivity decreases due to this, and it has not been possible to achieve both high peel strength and high thermal conductivity. Accordingly, an object of the present invention is to provide a metal foil laminated resin sheet capable of exhibiting high thermal conductivity and high peel strength in the lamination of a metal foil and a resin composite material.

Means for Solving the Problems

[0006] As a result of intensive investigations by the present inventors to solve the above problems, by laminating a metal foil layer and a resin composite material layer filled with a thermally conductive filler with a resin layer having a specific thickness formed therebetween, it has been found that a metal foil laminated resin sheet that achieves the above object can be obtained, and the present invention has been completed.

[0007] That is, the present invention is a metal foil laminated resin sheet including a metal foil layer, a resin layer, and a resin composite material layer including a resin matrix and a thermally conductive filler, in this order, wherein the thickness of the resin layer is 0.01 μm or more and 1.0 μm or less.

[0008] It is preferable that the resin layer contains a thermosetting resin and the resin matrix contains a thermosetting resin. Further, in the metal foil layer, the surface roughness Rz of the surface in contact with the resin layer is preferably 3.0 μm or less, and the thickness is preferably 5 to 500 μm.

[0009] Furthermore, the present invention is a method for manufacturing a metal foil laminated resin sheet, including a resin layer forming step of forming a layer of a resin precursor on the surface of a metal foil so that the thickness of the resin layer after curing is 0.01 μm to 1.0 μm, and a lamination step of laminating a resin composite material precursor containing a resin matrix and a thermally conductive filler on the surface of the metal material on which the layer of the resin precursor is formed.

Advantages of the Invention

[0010] The metal foil laminated resin sheet of the present invention can provide copper-clad laminates, metal base substrates, etc. having high thermal conductivity and high peel strength. As a result, it becomes easy to manufacture electronic devices with excellent heat dissipation performance and high reliability.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0012] The metal foil laminated resin sheet of the present invention has a laminated structure in which the cross-sectional structure is shown in the schematic diagram of FIG. 1, and includes a metal foil layer 2, a resin layer 3, and a resin composite material layer 4 in this order. This cross-sectional structure can be confirmed by cutting the metal foil laminated resin sheet 1 and observing it with a scanning electron microscope or the like.

[0013] In the metal foil layer of the present invention, the type of metal is not particularly limited. For example, copper foil, aluminum foil, stainless steel foil, etc. can be used, and copper foil is preferably used. The copper foil is preferably an electrolytic copper foil or a rolled copper foil.

[0014] The thickness of the metal foil layer is not particularly limited. However, in a conventional metal foil laminated resin sheet without a resin layer, when the metal foil layer is thin, large stress is generated at the interface between the metal foil layer and the resin composite material layer due to the deformation of the metal foil layer, and the adhesiveness tends to decrease. In particular, adhesiveness has been a major problem. Therefore, when the metal foil layer is thin, since the effect of improving adhesiveness according to the present invention is remarkable, the metal foil layer is preferably 500 μm or less, and more preferably 150 μm or less. The lower limit of the thickness of the metal foil layer is not particularly limited, but generally a metal foil of 5 μm or more is used from the viewpoints of manufacturing cost and durability.

[0015] The surface structure of the metal foil is not particularly limited. However, the surface roughness Rz of the surface in contact with the resin layer is preferably 3.0 μm or less, and more preferably 2.0 μm or less. When the surface roughness of the metal foil surface is small, it is easy to form a thin and uniform resin layer, and it becomes easy to achieve both high thermal conductivity and high peel strength. Further, in a conventional metal foil laminated resin sheet without a resin layer, when the metal foil surface is smooth, it is difficult to obtain an anchor effect, so the adhesiveness between the metal foil layer and the resin composite material layer tends to be low. When the surface roughness of the metal foil layer is small, the effect of improving adhesiveness according to the present invention is remarkable and can be said to be preferable. The surface roughness Rz in the present invention is measured by the method of JIS B0610:1994.

[0016] The resin layer in the present invention is a layer formed on the surface of a metal foil, and its thickness is 0.01 μm to 1.0 μm. The presence of such a resin layer can improve the adhesiveness and enable the obtaining of high peel strength. Although the reason why high peel strength can be obtained by the resin layer is not clear, the inventors of the present invention consider it as follows. That is, when a resin composite material layer is directly laminated on a metal foil layer, usually the heat-conductive filler in the resin composite material layer and the metal foil do not interact with each other. Therefore, the adhesion between the metal foil layer and the resin composite material layer is mainly due to the interaction between the resin matrix of the resin composite material and the metal foil layer. Therefore, when the heat-conductive filler is highly filled in the resin composite material layer to obtain a high heat conductivity, the amount of the resin component contributing to the adhesion at the interface between the metal foil and the resin composite material decreases, resulting in a decrease in adhesiveness. On the other hand, when a resin layer is formed between the metal foil layer and the resin polymerization material layer, high adhesiveness can be obtained between the metal foil layer and the resin layer due to the interaction between the metal foil layer and the resin layer, and high adhesiveness can also be obtained between the resin layer and the resin composite material layer due to the interaction between the resin of the resin layer and the resin matrix of the resin composite material layer. As a result, it is presumed that peeling is less likely to occur than when the resin composite material layer is directly laminated on the metal foil layer, and high peel strength can be obtained.

[0017] Here, since the resin layer has lower thermal conductivity than the metal foil layer or the resin composite material layer, it may cause a decrease in the thermal conductivity of the metal foil laminated resin sheet. However, by controlling the thickness of the resin layer to 1.0 μm or less, the thermal resistance in such a resin layer can be significantly reduced, and it becomes possible to obtain high thermal conductivity. Since it is easier to obtain high thermal conductivity when the resin layer is thinner, the thickness of the resin layer is preferably 0.9 μm or less, and more preferably 0.6 μm or less. However, if the resin layer is excessively thin, it is difficult to form a uniform film during manufacturing, and furthermore, the effect of improving adhesiveness tends to decrease. Therefore, the thickness of the resin layer is 0.01 μm or more, and preferably 0.1 μm or more.

[0018] The resin for forming the resin layer is not particularly limited, and known resins can be used. For example, thermosetting resins such as epoxy resins, cyanate resins, phenol resins, and silicone resins, acrylic resins, liquid crystal polymers, polyimide resins, etc. can be used. Among these, from the viewpoint of formability for thinly forming a film on a copper foil, a thermosetting resin is preferably used, and particularly an epoxy resin is preferably used. Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol S type epoxy resin, bisphenol F type epoxy resin, hydrogenated epoxy resin of bisphenol A type, polypropylene glycol type epoxy resin, polytetramethylene glycol type epoxy resin, naphthalene type epoxy resin, phenylmethane type epoxy resin, tetrakisphenol methane type epoxy resin, biphenyl type epoxy resin, epoxy resin having a triazine nucleus as a skeleton, and bisphenol A alkylene oxide adduct type epoxy resin, etc. These epoxy resins may be used alone or in combination of two or more. Also, amine-based resins, acid anhydride-based resins, phenol-based resins, imidazoles, etc. may be used as curing agents. These curing agents may also be used alone or in combination of two or more. In this specification, these curing agents are also included in the resin.

[0019] In addition to the resin, the resin layer may contain other components as long as the effects of the present invention are not significantly inhibited. Examples of other components include fillers, dispersants, coupling agents, leveling agents, etc.

[0020] The resin composite layer is formed of a resin composite material including at least a resin matrix and a thermally conductive filler. The resin matrix includes a resin and, if necessary, a small amount of additives. The resin of the resin matrix is not particularly limited, and known resins can be used. For example, thermosetting resins such as epoxy resin, cyanate resin, phenolic resin, and silicone resin, acrylic resin, liquid crystal polymer, polyimide resin, etc. can be used. Among these, from the viewpoint of moldability for highly filling the thermally conductive filler and forming into a sheet, it is preferably a thermosetting resin, and particularly preferably an epoxy resin. Examples of the epoxy resin can be those described above. Also, from the viewpoint of improving the adhesiveness between the resin layer and the resin composite layer, it is preferable that the resin matrix contains the same kind of resin as that contained in the resin layer.

[0021] The additive components contained in the resin matrix are not particularly limited as long as they do not significantly inhibit the effects of the present invention. For example, a dispersant, a coupling agent, a leveling agent, an affinity agent, etc. can be used.

[0022] The thermally conductive filler is not particularly limited. For example, silica, alumina, zinc oxide, magnesium oxide, titanium oxide, silicon nitride, aluminum nitride, boron nitride, aluminum hydroxide, magnesium hydroxide, silicon carbide, calcium carbonate, barium sulfate, talc, diamond, etc. with high insulation, or graphite, carbon fiber, metal particles such as silver and aluminum with high conductivity, etc. can be used. Particularly when high insulation is required for the metal foil laminated resin sheet, it is preferably alumina, silicon nitride, aluminum nitride, boron nitride, zinc oxide, magnesium oxide, diamond with high insulation and high thermal conductivity. The thermally conductive filler may be used in combination of multiple types.

[0023] Further, the particle size of the thermal conductive filler is not particularly limited, but from the viewpoints of thermal conductivity and fillability, the average particle size is preferably 0.01 to 250 μm, more preferably 0.1 to 150 μm. Also, the average particle size is preferably 0.7 times or less, more preferably 0.5 times or less, of the thickness of the resin composite material layer. Note that the average particle size is the D50 value measured by the laser diffraction scattering method.

[0024] Furthermore, the shape of the thermal conductive filler is not particularly limited, and spherical, rounded, crushed, plate-like, fibrous, aggregated shapes, etc. can be used, and particles of different shapes may be mixed.

[0025] The blending amount of the thermal conductive filler is not particularly limited, but in order to impart high thermal conductivity to the resin composite material layer, it is preferably 100 to 1000 parts by volume, more preferably 200 to 900 parts by volume, per 100 parts by volume of the resin matrix. Also, in the present invention, the resin composite material layer may contain a base material such as a glass cloth in addition to the resin matrix and the thermal conductive filler.

[0026] The resin composite material layer preferably has high thermal conductivity, and the thermal conductivity is preferably 5.0 W / m·K or more, more preferably 6.0 W / m·K or more, and even more preferably 10.0 W / m·K or more. The thermal conductivity of the resin composite material layer can be measured by the temperature wave thermal analysis method.

[0027] Also, the resin composite material layer preferably has high dielectric strength, and the dielectric strength is preferably 20 kV / mm or more, more preferably 40 kV / mm or more, and even more preferably 55 kV / mm or more. The high dielectric strength of the resin composite material layer is advantageous when the metal foil laminated resin sheet of the present invention is used as a substrate material for electronic devices such as metal-clad laminated boards and metalized substrates.

[0028] The thickness of the resin composite material layer is not particularly limited and may be appropriately determined according to the use of the metal foil laminated resin sheet. For example, in the case of a metal-clad laminate, it is generally 10 μm to 2000 μm, and in the case of the resin composite material layer of a metal-based substrate, it is generally 30 μm to 300 μm.

[0029] As described above, the cross-sectional structure of the metal foil laminated resin sheet can be confirmed by cutting the metal foil laminated resin sheet and observing it with a scanning electron microscope or the like. Specifically, the metal foil laminated resin sheet may be cut perpendicular to the surface of the metal foil, and the obtained cross-section may be observed with a scanning electron microscope. Examples of the cutting method include the ion milling method and mechanical cutting. The cut cross-section may be polished as necessary, or an observation sample may be produced by embedding it with a transparent resin or the like. In particular, the ion milling method, which can obtain a smooth cut surface suitable for observation, is preferable as a method for producing an observation sample. In scanning electron microscope observation, the metal foil layer and the resin layer can be distinguished because they have different contrasts, and the resin composite material layer can be distinguished from the resin layer because it contains a heat conductive filler. Even when the resin layer contains a filler, the resin composite material layer and the resin layer can be distinguished by the difference in the particle size and blending ratio of the filler. In addition, in the observation with a scanning electron microscope, the observation conditions such as the magnification are appropriately adjusted according to the thickness of the resin layer and the like.

[0030] The thickness of the resin layer is measured using the image obtained by the observation with the above scanning electron microscope. Specifically, in the scanning electron microscope image, the distance from the interface between the metal foil layer and the resin layer to the interface between the resin layer and the resin composite material layer is measured to obtain the thickness of the resin layer.

[0031] As described above, the metal foil laminated resin sheet of the present invention can achieve both high peel strength and high thermal conductivity. The peel strength of the metal foil laminated resin sheet of the present invention is preferably 4.50 N / cm or more, more preferably 5.50 N / cm or more, and even more preferably 6.00 N / cm or more. The thermal conductivity of the metal foil laminated resin sheet of the present invention is preferably 6.0 W / m·K or more, and more preferably 10.0 W / m·K or more. In the present application, the thermal conductivity of the metal foil laminated resin sheet is a value obtained by measuring the thermal conductivity of a laminate of a resin layer and a resin composition layer obtained by peeling the metal foil from the metal foil laminated resin sheet.

[0032] Furthermore, the dielectric strength of the metal foil laminated resin sheet of the present invention is preferably 20 kV / mm or more, more preferably 40 kV / mm or more, and even more preferably 55 kV / mm or more. Due to the high dielectric strength, it can be particularly preferably used as a substrate material for electronic devices such as metal-clad laminates and metal base substrates. Since the resin layer does not particularly adversely affect the dielectric strength, according to the present invention, it is possible to easily obtain a metal foil laminated resin sheet having high peel strength, high thermal conductivity, and high dielectric strength. In the present application, the dielectric strength of the metal foil laminated resin sheet is a value obtained by measuring the dielectric strength of a laminate of a resin layer and a resin composition layer obtained by peeling the metal foil from the metal foil laminated resin sheet.

[0033] The use of the metal foil laminated resin sheet of the present invention is not particularly limited. For example, it can be used as a metal-clad laminate, particularly a copper-clad laminate using a copper foil as the metal foil. The metal-clad laminate may be a single-sided metal-clad laminate in which the metal foil is laminated only on one side of the resin composite material layer, or may be a double-sided metal-clad laminate in which the metal foil is laminated on both sides of the resin composite material layer. When used as a double-sided metal-clad laminate, it may be in a form having a resin layer only on one side of the resin composite material layer, that is, a form laminated in the order of a metal foil layer, a resin layer, a resin composite material layer, and a metal foil layer, or may be in a form having resin layers on both sides of the resin composite material layer, that is, a form laminated in the order of a metal foil layer, a resin layer, a resin composite material layer, a resin layer, and a metal foil layer. In the metal-clad laminate, particularly when the metal foil is a copper foil, it can be particularly preferably used for printed circuit boards and the like as a copper-clad laminate.

[0034] Further, the metal foil laminated resin sheet of the present invention can be particularly preferably used as a metal base substrate in which a metal plate (such as a copper plate, an aluminum plate, or a stainless steel plate) having a thickness of about 0.5 mm to 3.0 mm is disposed on the surface of the resin composite material layer opposite to the metal foil, for substrates for power modules, LED substrates, and the like.

[0035] The manufacturing method of the metal foil laminated resin sheet of the present invention is not particularly limited, and it can be manufactured by laminating a resin composite material layer containing a resin and a thermally conductive filler on the surface of the metal foil through a resin layer adjusted to have a thickness of 0.01 μm to 1.0 μm.

[0036] As a preferred manufacturing method of the metal foil laminated resin sheet of the present invention, there is a manufacturing method including a resin layer forming step of forming a resin precursor layer on the surface of the metal foil so that the thickness of the cured resin layer becomes 0.01 μm to 1.0 μm, a laminating step of laminating a resin composite material precursor containing a resin matrix and a thermally conductive filler on the surface of the metal material on which the resin precursor layer is formed, and a curing step of curing the resin precursor and the resin composite material precursor.

[0037] In the resin layer forming step, the resin precursor layer forms a resin layer by subsequent operations. Examples of the resin precursor layer include, for example, when the resin of the resin layer is a thermosetting resin, a composition containing a curable resin that cures by a curing reaction with a curing agent. Specifically, when the resin of the resin layer is an epoxy resin, a composition containing an epoxy group-containing curable resin (curable epoxy resin) and a curing agent can be exemplified. Further, the resin precursor composition may be a semi-cured thermosetting resin. As a specific example of the resin layer forming step, a method of applying a varnish containing a resin precursor (for example, a composition containing an epoxy group-containing curable resin, a curing agent, and a solvent) to the surface of a metal foil and then removing the solvent by drying or the like can be mentioned.

[0038] Note that prior to the resin layer forming step, the surface roughness of the surface of the metal foil on which the resin precursor layer is to be formed may be adjusted by polishing treatment, blasting treatment, or the like. Further, rust prevention treatment with a metal, chemical conversion treatment with a coupling agent, or the like may be performed.

[0039] In the lamination step, a resin composite material precursor containing a resin matrix and a thermally conductive filler is laminated on the surface of the metal foil on which the resin precursor layer is formed. The resin composite material precursor forms a resin composite material layer by operations such as curing and drying.

[0040] When the resin matrix contains a thermosetting resin, an example of the resin composite precursor includes a composition containing a curable resin that cures by a curing reaction with a curing agent and a thermally conductive filler. Specifically, when the resin of the resin matrix is an epoxy resin, a composition containing an epoxy group-containing curable resin, a curing agent, and a thermally conductive filler can be exemplified. After laminating such a composition on the metal foil, the metal foil laminated resin sheet of the present invention can be obtained by curing the curable resin. The resin composite precursor may be a slurry containing a solvent. In some cases, by containing a solvent, a resin composition precursor layer can be easily formed by coating. When the resin composition precursor is a slurry containing a solvent, the solvent is removed by heating and drying or vacuum drying after lamination, and then the curable resin is cured to obtain the metal foil laminated resin sheet of the present invention.

[0041] Further, the resin composite precursor may be a sheet of a semi-cured resin composite (so-called "B-stage sheet"). After laminating the B-stage sheet and the metal foil and then subjecting them to polymerization curing, the metal foil laminated resin sheet of the present invention can be obtained. In this case, lamination and polymerization curing may be performed by hot pressing. The fact that the resin composite precursor is a B-stage sheet is a preferred form in the present invention because it has excellent workability and it is easy to increase the adhesive strength between the resin layer and the resin composite layer to obtain a high peel strength. The B-stage sheet can be produced, for example, by coating a slurry containing a curable resin, a curing agent, a thermally conductive filler, and a solvent on a film such as a PET film, then heating and drying to remove the solvent to obtain an A-stage sheet, and then semi-curing the A-stage sheet.

[0042] When the metal foil laminated resin sheet is a double-sided metal-clad laminated board, the B-stage sheet can be manufactured by sandwiching the B-stage sheet between two metal foils with a resin precursor layer formed on the surface and curing the resin precursor layer and the B-stage sheet by hot pressing. When the metal foil laminated resin sheet is a metal base substrate, the B-stage sheet can be manufactured by sandwiching the B-stage sheet between a metal foil with a resin precursor layer formed on the surface and a metal plate and curing the resin precursor layer and the B-stage sheet by hot pressing.

[0043] Furthermore, as another form of the method for manufacturing the metal foil laminated resin sheet of the present invention, after forming a layer of a resin precursor on the surface of the B-stage sheet, it can be bonded to a metal foil, and then the B-stage sheet and the resin precursor layer can be cured.

[0044] Also, when the resin composite material layer contains a glass cloth, for example, the glass cloth can be immersed in a slurry containing a curable resin, a thermally conductive filler, and a solvent to adhere the slurry to the glass cloth, and then dried to remove the solvent to obtain a so-called prepreg and manufacture the metal foil laminated resin sheet. Specifically, after laminating the prepreg and a metal foil with a resin precursor layer formed thereon, or sandwiching the prepreg between two metal foils with a resin precursor layer formed thereon, the metal foil laminated resin sheet can be manufactured by performing hot pressing.

Examples

[0045] Hereinafter, examples will be described to specifically explain the present invention, but the present invention is not limited to these examples. Also, the measurements of each value in the examples and comparative examples were measured by the following methods. (1) Measurement of peel strength The peel strength (N / cm) was measured by using a universal testing machine (manufactured by Shimadzu Corporation: Autograph AG-Xplus) and a peel test jig (adhesive tape peeling kit) according to the method of JIS C6481. A cut was made in the copper foil on one side of the metal foil laminated resin sheet with a width of 10 mm, one end was peeled off, grasped by a chuck, and the pulling (peeling) speed was set to 50 mm / min.

[0046] (2) Measurement of Thermal Conductivity The copper foils on both sides of the metal foil laminated resin sheet were peeled off, and the thermal conductivity of the laminate of the resin layer and the resin composite material layer was measured. The thermal conductivity (W / m·K) was determined by thermal diffusivity (m 2 / s) × density (kg / m 3 ) × specific heat (J / kg·K). The thermal diffusivity was measured using the temperature wave thermal analysis method (manufactured by AI Phase: ai-Phase Mobile u, ISO22007-3), the density was measured using the Archimedes method (manufactured by METTLER TOLEDO: XS204V), and the specific heat was measured using the differential scanning calorimeter (DSC) method (manufactured by Rigaku: Thermo Plus Evo DSC8230).

[0047] (3) Measurement of Dielectric Strength The copper foils on both sides of the metal foil laminated resin sheet were peeled off, and the dielectric strength of the laminate of the resin layer and the resin composite material layer was measured. The dielectric strength (kV / mm) was measured using a voltage withstand tester YPAD-0225 manufactured by Kinnan Electric Co., Ltd. in accordance with the general test method for thermosetting plastics of JIS K6911.

[0048] (4) Observation of the Cross-Section of the Metal Foil Laminated Resin Sheet and Measurement of the Thickness of the Resin Layer For the observation of the cross-section of the metal foil laminated resin sheet, a cross-section sample was processed using an ion milling device ArBlade5000 manufactured by Hitachi High-Technologies Corporation, and observed using a scanning electron microscope (SEM) SU3500 manufactured by Hitachi High-Technologies Corporation. The thickness of the resin layer was measured from the observed SEM image.

[0049] (Example 1) A liquid curable epoxy resin (manufactured by Mitsubishi Chemical: jER828, bisphenol A type epoxy resin, epoxy equivalent 184 - 194 g / eq) and an epoxy resin curing agent (manufactured by Mitsubishi Chemical: jER cure WA, modified aromatic amine, amine value 623 - 639) were mixed at a mass ratio of 4:1, and cyclohexanone (manufactured by Wako Pure Chemical Industries, special grade) was added as a solvent and diluted. The resulting composition was applied to the unroughened surface of a copper foil (manufactured by Fukuda Metal Foil & Powder Industry: ultra-low roughness electrolytic copper foil T9DA-SV without roughening treatment, thickness 35 μm, surface roughness Rz: 0.4 μm) using an automatic coating device (manufactured by Tester Sangyo Co., Ltd.: PI-1210). After the coated copper foil was air-dried in a draft for 15 minutes, it was left standing in a vacuum dryer at 190 °C for 3 hours to remove cyclohexanone and perform polymerization curing, obtaining a copper foil with a resin layer laminated thereon.

[0050] As thermal conductive fillers, filler A (aluminum nitride filler, average particle size D50: 1.0 μm), filler B (aluminum nitride filler, average particle size D50: 4.5 μm), filler C (spherical aluminum nitride filler, average particle size D50: 37 μm), a liquid curable epoxy resin (manufactured by Mitsubishi Chemical, jER828, bisphenol A type epoxy resin, epoxy equivalent 184 - 194 g / eq), an epoxy resin curing agent (manufactured by Mitsubishi Chemical, jER cure WA, modified aromatic amine, amine value 623 - 639), an affinity agent (Toho Chemical Industry Co., Ltd.: phosphate ester type dispersant RS-710), and cyclohexanone (manufactured by Wako Pure Chemical Industries, special grade) as a solvent were weighed according to the compounding ratios shown in Table 1 and stirred and mixed using a planetary mixer (manufactured by Kurabo Industries Ltd.: Mazelstar KK-250S) to obtain a slurry. The compounding amounts of the epoxy resin and the epoxy resin curing agent were in a mass ratio of 4:1, and the compounding amount of the affinity agent was 0.3 parts by mass with respect to 100 parts by mass of the filler. Also, the solvent was used in an amount 1.71 times the total amount of the liquid curable epoxy resin and the epoxy resin curing agent by mass. The compounding amounts were calculated using the densities of aluminum nitride and epoxy resin as 3.26 g / cm 3 and 1.17 g / cm 3 respectively.

[0051] The above slurry was applied onto the release-treated surface side of a release-treated polyethylene terephthalate (PET) film (PET50X1-FSC6 manufactured by Nippa, thickness 50 μm) using the automatic coating device at a coating thickness setting of 150 μm and a speed of 50 mm / second. After coating, it was air-dried in a draft for 15 minutes and then vacuum-dried at 130°C for 50 minutes using a vacuum dryer to obtain a PET film with an A-stage sheet of the resin composition precursor layer as an A-stage sheet. Next, two PET films with the above A-stage sheets were stacked with the release PET film on the outside such that the A-stage sheets were in contact with each other, and were thermally pressed at 100°C under reduced pressure using a vacuum heating press device (manufactured by Imoto Seisakusho: manual hydraulic vacuum heating press) at a press pressure of 4 MPa for 3 minutes to be pressure-bonded, forming a B-stage sheet of the resin composition precursor layer.

[0052] The release PET film on one side of the B-stage sheet of the resin composition precursor layer obtained above was peeled off, and a copper foil with a resin layer formed thereon was stacked such that the resin layer side was in contact with the resin composition precursor layer. Using a vacuum heating press device, it was thermally pressed at a press pressure of 4 MPa for 3 minutes under reduced pressure to bond the copper foil. Similarly, a copper foil with a resin layer formed on the opposite side was also pressure-bonded. Subsequently, the temperature was raised to 170°C, and it was thermally pressed at a press pressure of 20 MPa for 60 minutes under reduced pressure to cure the B-stage sheet. Next, a metal foil laminated resin sheet was produced by performing a heat treatment at 165°C for 2 hours and then at 190°C for 2 hours using a box-type oven to completely cure the resin.

[0053] For the obtained metal foil laminated resin sheet, the resin layer thickness, peel strength, thermal conductivity, and insulation resistance were measured. The results are shown in Table 1. The thickness of the resin layer observed by SEM was 0.2 μm. The thickness of the resin composite material layer was 122 μm. The peel strength of the metal foil laminated resin sheet was 7.46 N / cm, and the thermal conductivity was 15.4 W / m·K, both of which were high values.

[0054] (Examples 2, 3, 4) A metal foil laminated resin sheet was produced in the same manner as in Example 1 except that the thickness of the resin layer formed on the copper foil was as shown in Table 1. The evaluation results are shown in Table 1.

[0055] (Comparative Examples 1 and 2) A metal foil laminated resin sheet was produced in the same manner as in Example 1, except that the thickness of the resin layer formed on the copper foil was as shown in Table 1. The thickness of the resin layer was adjusted by the dilution ratio of the resin and the solvent and the coating thickness. The evaluation results are shown in Table 1. Although the peel strength was high, since the resin layer was thick, a significant decrease in thermal conductivity was observed as compared with Examples 1 to 4.

[0056] (Comparative Example 3) A metal foil laminated resin sheet was produced in the same manner as in Example 1, except that no resin layer was formed on the copper foil. The evaluation results are shown in Table 1. Since there was no resin layer, the thermal conductivity was high, but the peel strength was significantly lower as compared with Examples 1 to 4.

[0057] (Examples 5 and 6) A metal foil laminated resin sheet was produced in the same manner as in Example 1, except that the blending ratio of the thermal conductive filler was as shown in Table 1. The evaluation results are shown in Table 1.

[0058] (Comparative Example 4) A metal foil laminated resin sheet was produced in the same manner as in Example 6, except that the thickness of the resin layer was as shown in Table 1. The evaluation results are shown in Table 1. Since the resin layer was thick, the peel strength was high as compared with Example 6, but a significant decrease in thermal conductivity was observed.

[0059] (Comparative Example 5) A metal foil laminated resin sheet was produced in the same manner as in Example 6, except that no resin layer was formed on the copper foil. The evaluation results are shown in Table 1. Since there was no resin layer, the thermal conductivity was high as compared with Example 6, but the peel strength was significantly lower.

[0060] (Example 7) In the same manner as in Example 1, after obtaining a slurry containing a copper foil having a resin layer formed thereon, a curable epoxy resin, an epoxy curing agent, a thermal conductive filler, and a solvent, the slurry was directly coated on the resin layer side of the copper foil without using a release PET film to produce a metal foil laminated resin sheet.

[0061] That is, using the automatic coating device, slurry was coated on the resin layer surface of the copper foil having a resin layer formed thereon at a coating thickness setting of 150 μm and a speed of 50 mm / second. After coating, it was air-dried in a draft for 15 minutes, and then vacuum-dried at 130 °C for 50 minutes using a vacuum dryer to form an A-stage sheet in which a resin composition precursor layer was laminated on one side of the copper foil. Next, two of the above A-stage sheets were overlapped with the copper foils on the outside so that the resin composition precursor layers faced each other, and heat-pressed at 100 °C under reduced pressure using the vacuum heating press device at a press pressure of 4 MPa for 3 minutes to be pressure-bonded, thereby obtaining a B-stage sheet of the resin composition precursor layer of the double-sided copper foil, and it was taken out from the vacuum heating press device.

[0062] Thereafter, after raising the temperature of the vacuum heating press device to 170 °C, the above B-stage sheet was inserted, and heat-pressed at a press pressure of 20 MPa for 60 minutes under reduced pressure to be cured. Next, heat treatment was performed at 165 °C for 2 hours and further at 190 °C for 2 hours using a box-type oven to completely cure the resin, thereby producing a metal foil laminated resin sheet.

[0063] Regarding the obtained metal foil laminated resin sheet, the resin layer thickness, peel strength, thermal conductivity, and insulation breakdown voltage were measured. The results are shown in Table 1. Similar to the results of Example 1, a metal foil laminated resin sheet having high peel strength and thermal conductivity was obtained.

[0064] (Comparative Example 6) A metal foil laminated resin sheet was produced in the same manner as in Example 7, except that slurry was directly coated on the copper foil without forming a resin layer on the copper foil. The evaluation results are shown in Table 1. Compared with Example 7, the thermal conductivity was high, but the peel strength was significantly low.

[0065] (Example 8) As a heat conductive filler, except that filler D (alumina filler, particle size D50: 0.7 μm), filler E (alumina filler, particle size D50: 3.0 μm), and filler F (spherical alumina filler, particle size D50: 38 μm) were used, a metal foil laminated resin sheet was produced in the same manner as in Example 7. The volume parts of the heat conductive filler and the resin were calculated based on the densities of alumina and epoxy resin being 3.98 g / cm 3 , 1.17 g / cm 3 respectively. The evaluation results are shown in Table 2.

[0066] Compared with Example 7, although the thermal conductivity slightly decreased due to changing the heat conductive filler from aluminum nitride to alumina, a metal foil laminated resin sheet with high thermal conductivity and high peel strength was obtained.

[0067] (Comparative Example 7) A metal foil laminated resin sheet was produced in the same manner as in Example 8, except that the thickness of the resin layer was as shown in Table 2. The evaluation results are shown in Table 1. Since the resin layer was thick, the peel strength was high compared with Example 8, but a significant decrease in thermal conductivity was observed.

[0068] (Comparative Example 8) A metal foil laminated resin sheet was produced in the same manner as in Example 8, except that no resin layer was formed on the copper foil. The evaluation results are shown in Table 1. Since there was no resin layer, the thermal conductivity was high compared with Example 8, but the peel strength was significantly low.

[0069] (Example 9) A metal foil laminated resin sheet was produced in the same manner as in Example 1, except that a commercially available electrolytic copper foil (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.: T8G-UN, thickness 35 μm, surface roughness Rz: 7.4 μm) was used for the copper foil. The evaluation results are shown in Table 1. The peel strength was higher compared with Comparative Example 3 where no resin layer was formed. On the other hand, compared with Example 1, the peel strength was slightly lower. This is considered to be because the surface roughness of the copper foil was larger than that of Example 1, resulting in the resin layer being partially non-uniform.

[0070] (Example 10) A metal foil laminated resin sheet was produced in the same manner as in Example 1, except that a rolled copper foil with ultra-low roughness (manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.: RCT-T4X, thickness 35 μm, surface roughness Rz: 0.3 μm) was used for the copper foil. The evaluation results are shown in Table 1.

[0071]

Table 1

[0072]

Table 2

Explanation of Symbols

[0073] 1 Metal foil laminated resin sheet 2 Metal foil layer 3 Resin layer 4 Resin composite material layer

Claims

1. A metal foil laminated resin sheet comprising, in this order, a metal foil layer, a resin layer, and a resin composite material layer containing a resin matrix and a thermally conductive filler, wherein the thickness of the resin layer is 0.01 μm or more and 1.0 μm or less, and in the metal foil layer, the surface roughness Rz of the surface in contact with the resin layer is 3.0 μm or less, and the thickness is 5 to 500 μm.

2. The metal foil laminated resin sheet according to claim 1, wherein the resin layer contains a thermosetting resin and the resin matrix contains a thermosetting resin.

3. A method for manufacturing a metal foil laminated resin sheet, comprising: a resin layer forming step of forming a layer of a resin precursor on the surface of the metal foil so that the thickness of the resin layer after curing is 0.01 μm to 1.0 μm; a laminating step of laminating a resin composite material precursor containing a resin matrix and a thermally conductive filler on the surface of the metal material on which the layer of the resin precursor is formed; and a curing step of curing the resin precursor and the resin composite material precursor.

4. The method for manufacturing a metal foil laminated resin sheet according to claim 3, wherein the resin precursor is a curable resin containing an epoxy group and the resin matrix contains a curable resin containing an epoxy group.

5. The method for manufacturing a metal foil laminated resin sheet according to claim 3 or 4, wherein in the metal foil layer, the surface roughness Rz of the surface in contact with the resin layer is 3.0 μm or less, and the thickness is 5 to 500 μm.

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