Metal-based substrate

Abstract

To provide a metal base substrate with excellent heat dissipation and reliability.SOLUTION: In a metal base substrate in which a metal substrate, an isolation layer of at least one layer, and a circuit layer are laminated in this order, a board thickness TM of the metal substrate is within a range of 0.5 mm or more and 1.1 mm or less, a cube of a product TM3×EM of the board thickness TM (unit: mm) of the metal substrate and an elasticity modulus EM (unit: GPa) under 25°C of the metal substrate is within a range of 10 or more and 1000 or less, a sum of a ratio TR / ER of a film thickness TR (unit: mm) to an elasticity modulus ER (unit: GPa) under 100°C in each layer constructing the isolation layer is within a range of 30 and 1000 or less, and a sum of a ratio TR / CR of a film thickness TR (unit: mm) to a heat conductivity CR (unit: W / mK) of each layer constructing the isolation layer is within a range of 2 or more and 40 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a metal-based substrate. [Background technology]

[0002] Metal base substrates are known as one type of substrate for mounting electronic components such as semiconductor elements and LEDs. A metal base substrate is a laminate in which a metal substrate, an insulating layer, and a circuit layer are stacked in this order. In a module in which electronic components are mounted on the circuit layer of a metal base substrate via solder, heat generated in the electronic components is transferred to the metal substrate via the insulating layer and dissipated from the metal substrate to the outside. For this reason, the insulating layer of a metal base substrate is generally formed from an insulating composition containing a resin with excellent insulating properties and voltage resistance and an inorganic filler with excellent thermal conductivity.

[0003] A known metal base substrate has, for example, a metal substrate having a thickness of 1 to 5 mm, a circuit layer having a thickness of 100 to 500 μm, and an insulating layer consisting of two or more insulating resin layers, each of which has at least one layer containing a thermoplastic insulating resin and one layer containing a non-thermoplastic insulating resin, and at least one of the two or more insulating resin layers contains a filler having a higher thermal conductivity than the insulating resin that constitutes the insulating resin layer (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-43417 Summary of the Invention [Problem to be solved by the invention]

[0005] In the development of metal-based substrates, heat dissipation has been a key priority, and increasing the thickness of the base metal has been a common approach to improving heat dissipation. However, the metal substrate of a metal-based substrate has a high thermal expansion coefficient, making it susceptible to volumetric changes due to expansion and contraction caused by heat. On the other hand, many electronic components are based on ceramic substrates, which have a low thermal expansion coefficient. Therefore, in modules in which electronic components are mounted via solder on the circuit layer of a metal-based substrate, the stress applied to the solder can fluctuate depending on the electronic components being turned on and off or changes in the external temperature, which can lead to cracks in the solder and other degradation in reliability. To mitigate the fluctuations in stress applied to the solder, it is effective to increase the thickness of the insulating layer to absorb volumetric changes in the metal substrate. However, increasing the thickness of the insulating layer can hinder the transfer of heat generated by electronic components to the metal substrate through the insulating layer, potentially reducing the heat dissipation capabilities of the metal-based substrate. In other words, it is difficult to achieve both heat dissipation and reliability in a metal-based substrate.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a metal base substrate that is excellent in heat dissipation and reliability. [Means for solving the problem]

[0007] In order to solve the above problems, the metal base substrate of the present invention is a metal base substrate in which a metal substrate, at least one insulating layer, and a circuit layer are laminated in this order, and the thickness T of the metal substrate is M is in the range of 0.5 mm or more and 1.1 mm or less, and the thickness T M (unit: mm) and the elastic modulus E of the metal substrate at 25 ° C. M (unit: GPa) and the product T M 3 ×E M is in the range of 10 or more and 1000 or less, and the elastic modulus E at 100 ° C of each layer constituting the insulating layer is R (unit: GPa) vs. film thickness T R (unit: μm ) ratio T R / E RThe sum of the above is in the range of 30 to 1000, and the thermal conductivity C of each layer constituting the insulating layer is R (unit: W / mK) vs. film thickness T R (unit: μm ) ratio T R / C R The sum of these is between 2 and 40.

[0008] According to the metal base substrate having the above-mentioned configuration, the thickness T M Since the thickness T is within the range of 0.5 mm to 1.1 mm, when an electronic component is joined to a metal base substrate by soldering, the thermal stress on the solder can be suppressed even if the temperature of the electronic component changes. M (unit: mm) cubed value and the elastic modulus E of the metal substrate at 25°C M (unit: GPa) and the product T M 3 ×E M Since the modulus of elasticity E at 100°C of each layer constituting the insulating layer is in the range of 10 to 1000, it is possible to suppress warping of the metal base substrate after mounting electronic components. R (unit: GPa) vs. film thickness T R (unit: μm ) ratio T R / E R Since the sum of these is in the range of 30 to 1000, the stress relaxation ability of the circuit layer is increased, and when electronic components are mounted on the circuit layer via solder, the stress applied to the solder can be reduced. Furthermore, the thermal conductivity C of each layer constituting the insulating layer R (unit: W / mK) R (unit: μm ) ratio T R / C R Since the sum of these is within the range of 2 to 40, when an electronic component is mounted on the circuit layer via solder, the heat generated by the electronic component can be efficiently transferred to the metal substrate. Therefore, the metal base substrate configured as described above has excellent heat dissipation properties and reliability.

[0009] Here, in the metal base substrate of the present invention, the metal substrate may be configured to contain at least one metal selected from the group consisting of aluminum, copper, and iron. In this case, since the metal substrate has high thermal conductivity and heat resistance, the heat dissipation capability and reliability of the metal base substrate are further improved.

[0010] In the metal base substrate of the present invention, the insulating layer may be a single layer, and the single layer may be made of a resin composition having a filler content of 30% by volume or more and 85% by volume or less. Alternatively, the insulating layer may be a two-layer laminate having a first insulating layer formed on a metal layer and a second insulating layer laminated on the first insulating layer, and one of the first insulating layer and the second insulating layer may be made of a resin composition having a filler content of 50% by volume or more and 85% by volume or less, and the other layer may be made of a resin composition having a resin or filler content of 1% by volume or less. In this case, the thermal conductivity and stress relaxation ability of the insulating layer are increased, further improving the heat dissipation ability and reliability of the metal base substrate.

[0011] Furthermore, in the metal base substrate of the present invention, the insulating layer may have a thickness of 100 μm or less. In this case, since the insulating layer is thin, when an electronic component is mounted on the circuit layer via solder, heat generated in the electronic component can be transferred more efficiently to the metal substrate.

[0012] In the metal base substrate of the present invention, the circuit layer may have a thickness of 80 μm or less. In this case, since the circuit layer is thin, when electronic components are mounted on the circuit layer via solder, the thermal stress applied to the solder from the circuit layer is reduced, further improving the reliability of the metal base substrate. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a metal base substrate that is excellent in heat dissipation and reliability. [Brief explanation of the drawings]

[0014]

Figure 1

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of a metal base substrate according to one embodiment of the present invention. 1, the metal base substrate 10 is a laminate in which a metal substrate 20, an insulating layer 30, and a circuit layer 40 are laminated in this order. Electrode terminals 61 of an electronic component 60 are connected to the circuit layer 40 of the metal base substrate 10 via solder 50, thereby forming a module.

[0016] The metal substrate 20 is a member that serves as the base of the metal base substrate 10 . The metal substrate 20 has a thickness T M is in the range of 0.5 mm to 1.1 mm. M By making the thickness T 0.5 mm or more, the strength of the metal substrate 20 is increased, and deformation such as warping due to heat can be suppressed. M By making the thickness T 1.1 mm or less, the amount of volume change of the metal substrate 20 due to heat is reduced. M From the viewpoint of reducing the amount of volume change of the metal substrate 20 due to heat, the thickness T M is preferably 1.0 mm or less.

[0017] Plate thickness T of metal substrate 20 M (unit: mm) and the elastic modulus E of the metal substrate 20 at 25°C M (unit: GPa) and the product T M 3 ×E M is in the range of 10 to 1000. M 3 ×EM By making T 10 or more, deformation such as warping due to heat of the metal substrate 20 can be suppressed. M 3 ×E M By keeping T at 1000 or less, the metal substrate 20 does not become too thick. M 3 ×E M is preferably 30 or more and 300 or less. The elastic modulus (tensile modulus) of the metal substrate 20 at 25° C. can be measured by a tensile test (JIS Z2241:2011, Tensile test method for metallic materials).

[0018] The metal substrate 20 is preferably a copper substrate, an aluminum substrate, or an iron substrate. The copper substrate is made of copper or a copper alloy. The copper alloy is an alloy in which copper is the largest component element. The aluminum substrate is made of aluminum or an aluminum alloy. The aluminum alloy is an alloy in which aluminum is the largest component element. The iron substrate is made of iron or an iron alloy. The iron alloy is an alloy in which iron is the largest component element. The iron alloy includes carbon steel.

[0019] The insulating layer 30 is a layer for insulating the metal substrate 20 from the circuit layer 40. The insulating layer 30 also has a heat transfer function for transferring heat generated in the electronic components 60 to the metal substrate 20, and a stress relaxation function for absorbing the volume change of the metal substrate 20 due to heat and easing the stress applied to the solder 50. The insulating layer 30 has an elastic modulus E R (unit: GPa) vs. film thickness T R (unit: μm ) ratio T R / E R is in the range of 30 to 1000. R / E R By making T 1000 or less, the stress relaxation function of the insulating layer 30 is improved, and the stress applied to the solder 50 can be reduced. R / E R is preferably 30 or more, and more preferably 100 or more. R / ER is preferably 300 or less, and particularly preferably 200 or less. The elastic modulus of the insulating layer 30 at 100°C can be measured, for example, as follows: The metal substrate 20 and circuit layer 40 of the metal base substrate 10 are removed by etching to isolate the insulating layer 30. The elastic modulus (tensile modulus) of the obtained insulating layer 30 is measured by dynamic viscoelasticity measurement (DMA).

[0020] The insulating layer 30 has a thermal conductivity of C R (unit: W / mK) R (unit: μm ) ratio T R / C R is in the range of 2 to 40. R / C R By making T equal to or greater than 2, the thickness of the insulating layer 30 does not become too thin, and the insulating properties are ensured. R / C R When the T is 40 or less, the heat transfer function of the insulating layer 30 is improved, and the heat generated in the electronic component 60 can be efficiently transferred to the metal substrate 20. R / C R is preferably 3 or more, more preferably 5 or more. R / C R is preferably 30 or less, and particularly preferably 20 or less. The thermal conductivity of the insulating layer 30 can be measured, for example, as follows: The metal substrate 20 and the circuit layer 40 of the metal base substrate 10 are removed by etching, and the insulating layer 30 is isolated. The thermal conductivity of the obtained insulating layer 30 is measured by the laser flash method.

[0021] The insulating layer 30 is a single layer made of an insulating resin composition containing an insulating resin 31 and an inorganic filler 32. By forming the insulating layer 30 from an insulating resin composition containing the insulating resin 31 with high insulating properties and the inorganic filler 32 with high thermal conductivity, it is possible to improve thermal conductivity while maintaining insulation properties.

[0022] For example, polyimide resin, polyamide-imide resin, or a mixture thereof can be used as the insulating resin 31. These resins have excellent properties such as insulation, voltage resistance, chemical resistance, and mechanical properties, and therefore improve these properties of the metal base substrate 10.

[0023] Examples of inorganic filler 32 that can be used include alumina (Al2O3) particles, alumina hydrate particles, aluminum nitride (AlN) particles, silica (SiO2) particles, silicon carbide (SiC) particles, titanium oxide (TiO2) particles, and boron nitride (BN) particles. The average particle diameter of inorganic filler 32 is preferably within a range of 0.1 μm to 20 μm.

[0024] The content of inorganic filler 32 in insulating layer 30 is preferably in the range of 30% by volume or more and 85% by volume or less. When the content of inorganic filler 32 is 30% by volume or more, the thermal conductivity of insulating layer 30 is improved. On the other hand, when the content of inorganic filler 32 is 85% by volume or less, the insulating properties of insulating layer 30 are improved. From the viewpoint of improving the thermal conductivity of insulating layer 30, the content of inorganic filler 32 is more preferably 50% by volume or more, and particularly preferably 80% by volume or less.

[0025] The thickness of the insulating layer 30 is preferably 100 μm or less. By making the thickness of the insulating layer 30 100 μm or less, the heat transfer function of the insulating layer 30 is improved, and heat generated in the electronic component 60 can be efficiently transferred to the metal substrate 20. The thickness of the insulating layer 30 is not particularly limited as long as the dielectric strength is within a practical range, but is preferably 30 μm or more. By making the thickness of the insulating layer 30 30 μm or more, the metal substrate 20 and the circuit layer 40 can be reliably insulated, the stress relaxation function of the insulating layer 30 is improved, and the stress applied to the solder 50 can be reduced. From the viewpoint of improving the heat transfer function, the thickness of the insulating layer 30 is preferably 70 μm or less, and particularly preferably 50 μm or less. Furthermore, from the viewpoint of improving the insulation properties, the thickness of the insulating layer 30 is particularly preferably 40 μm or more.

[0026] The circuit layer 40 is formed in a circuit pattern. Electrode terminals 61 of the electronic component 60 are bonded onto the circuit layer 40 formed in the circuit pattern via solder 50 or the like. Metals such as copper, aluminum, and gold can be used as the material for the circuit layer 40. The circuit layer 40 is preferably made of copper foil. The thickness of the circuit layer 40 is preferably within a range of 2 μm to 200 μm.

[0027] It is particularly preferable that the thickness of the circuit layer 40 is 80 μm or less. By making the thickness of the circuit layer 40 80 μm or less, thermal stress generated in the circuit layer 40 is reduced, and thermal stress applied to the solder 50 is reduced. Furthermore, from the viewpoint of reducing thermal stress, the thickness of the circuit layer 40 is preferably 75 μm or less, and particularly preferably 50 μm or less. There are no particular restrictions on the thickness of the circuit layer 40 as long as it has sufficiently low resistance to the current used, but it is preferably 2 μm or more. By making the thickness of the circuit layer 40 2 μm or more, the electrical resistance of the circuit layer 40 is reduced, and the internal resistance of the module can be reduced. From the viewpoint of reducing electrical resistance, the thickness of the circuit layer 40 is preferably 5 μm or more, and particularly preferably 20 μm or more.

[0028] Examples of the electronic component 60 mounted on the metal base substrate 10 of this embodiment are not particularly limited and include semiconductor elements, resistors, capacitors, crystal oscillators, etc. Examples of semiconductor elements include MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors), IGBTs (Insulated Gate Bipolar Transistors), LSIs (Large Scale Integration), LEDs (Light Emitting Diodes), LED chips, and LED-CSPs (LED-Chip Size Packages).

[0029] As the solder 50, for example, solder materials such as Sn--Ag, Sn--Cu, Sn--In, and Sn--Ag--Cu (so-called lead-free solder materials) can be used.

[0030] The metal base substrate 10 of this embodiment can be manufactured by, for example, a method including an insulating layer forming step and a circuit layer compression bonding step.

[0031] In the insulating layer forming step, an insulating layer 30 is formed on the metal substrate 20 to obtain a metal substrate with an insulating layer. The insulating layer 30 can be formed by coating or electrodeposition. The coating method involves applying a coating liquid containing a solvent, insulating resin, and inorganic filler onto metal substrate 20 to form a coating layer, and then heating the coating layer to obtain insulating layer 30. The coating liquid can be a resin material solution in which insulating resin is dissolved, and an inorganic filler-dispersed resin material solution containing inorganic filler dispersed in the resin material solution. Methods that can be used to apply the coating liquid to the surface of the substrate include spin coating, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, and dip coating.

[0032] The electrodeposition method involves immersing the metal substrate 20 in an electrodeposition solution containing insulating resin particles and an inorganic filler, electrodepositing the insulating resin particles and inorganic filler on the surface of the substrate to form an electrodeposited film, and then heating the resulting electrodeposited film to form the insulating layer 30. The electrodeposition solution may be prepared by adding a poor solvent for the insulating resin to an inorganic filler-dispersed insulating resin solution containing an insulating resin solution and inorganic filler dispersed in the insulating resin solution, thereby precipitating the insulating resin as particles.

[0033] In the circuit layer compression bonding step, a metal foil is laminated on the insulating layer 30 of the insulating layer-equipped metal substrate, and the resulting laminate is heated and pressurized to form the circuit layer 40, thereby obtaining the metal base substrate 10. The heating temperature of the laminate is, for example, 200°C or higher, and more preferably 250°C or higher. The upper limit of the heating temperature is below the thermal decomposition temperature of the insulating resin, and preferably a temperature 30°C lower than the thermal decomposition temperature. The pressure applied during compression bonding is, for example, in the range of 1 MPa to 30 MPa, and more preferably in the range of 3 MPa to 25 MPa. The compression bonding time varies depending on the heating temperature and pressure, but is generally 60 minutes to 180 minutes.

[0034] According to the metal base substrate 10 of this embodiment configured as described above, the thickness T M Since the thickness T is in the range of 0.5 mm or more and 1.1 mm or less, it is possible to suppress deformation of the metal substrate 20 due to heat and to reduce the amount of volume change. M (unit: mm) cubed value and the elastic modulus E of the metal substrate at 25°C M (unit: GPa) and the product T M 3 ×E M Since the modulus of elasticity E of the insulating layer 30 at 100° C. is in the range of 10 to 1000, it is possible to further suppress deformation of the metal substrate 20 due to heat. R (unit: GPa) vs. film thickness T R (unit: μm ) ratio T R / E R Since the thermal conductivity C of the insulating layer 30 is in the range of 30 or more and 1000 or less, the stress applied to the solder 50 can be reduced. R (unit: W / mK) R (unit: μm ) ratio T R / C R Since the sum of these is within the range of 2 or more and 40 or less, the heat generated in the electronic component 60 can be efficiently conducted to the metal substrate 20. Therefore, the metal base substrate 10 of this embodiment has excellent heat dissipation properties and reliability.

[0035] In the metal base substrate 10 of this embodiment, when the metal substrate 20 contains at least one metal selected from the group consisting of aluminum, copper, and iron, the thermal conductivity and heat resistance of the metal substrate 20 are increased, thereby further improving the heat dissipation ability and reliability of the metal base substrate 10.

[0036] In the metal base substrate 10 of this embodiment, when the insulating layer 30 is a resin composition having a filler content in the range of 30 volume % or more and 85 volume % or less, the thermal conductivity and stress relaxation ability of the insulating layer 30 are increased, thereby further improving the heat dissipation ability and reliability of the metal base substrate 10.

[0037] In the metal base substrate 10 of this embodiment, when the insulating layer 30 has a thin film thickness of 100 μm or less, the heat generated in the electronic component 60 can be transferred to the metal substrate 20 more efficiently. In the metal base substrate 10 of this embodiment, when the film thickness of the circuit layer 40 is as thin as 80 μm or less, the thermal stress applied to the solder 50 from the circuit layer 40 is reduced, further improving the reliability of the metal base substrate 10.

[0038] Although the embodiment of the present invention has been described above, the present invention is not limited to this and can be modified as appropriate within the scope of the technical idea of ​​the invention. For example, in this embodiment, the insulating layer 30 is a single layer, but the insulating layer 30 may be a laminate. R / E R is the modulus of elasticity E at 100°C of each layer constituting the insulating layer 30 R (unit: GPa) vs. film thickness T R (unit: μm ) ratio T R / E R For example, when the insulating layer 30 is a two-layer laminate having a first insulating layer formed on the metal substrate 20 and a second insulating layer laminated on the first insulating layer, the T R / E R is the elastic modulus E of the first insulating layer at 100°C R1 (unit: GPa) vs. film thickness T R1(unit: μm ) ratio T R1 / E R1 and the elastic modulus E of the second insulating layer at 100°C R2 (unit: GPa) vs. film thickness T R2 (unit: μm ) ratio T R2 / E R2 When the insulating layer 30 is a laminate, T R / C R is the thermal conductivity C of each layer constituting the insulating layer 30 R (unit: W / mK) R (unit: μm ) ratio T R / C R For example, when the insulating layer 30 is a two-layer laminate consisting of a first insulating layer on the metal substrate 20 side and a second insulating layer on the circuit layer 40 side, the T R / C R is the thermal conductivity of the first insulating layer, C R1 (unit: W / mK) R1 (unit: μm ) ratio T R1 / C R1 and the thermal conductivity of the second insulating layer, C R2 (unit: W / mK) R2 (unit: μm ) ratio T R2 / C R2 This is the sum of the above.

[0039] When the insulating layer 30 is a two-layer laminate having a first insulating layer formed on the metal substrate 20 side and a second insulating layer laminated on the first insulating layer, it is preferable that one of the first insulating layer and the second insulating layer is a layer of a resin composition having a filler content of 50% by volume or more and 85% by volume or less, and the other layer is a layer of a resin composition having a filler content of 0% by volume or more and 1% by volume or less. In this case, the thermal conductivity and stress relaxation ability of the insulating layer 30 are increased, further improving the heat dissipation ability and reliability of the metal base substrate 10. [Example]

[0040] The present invention will be described below with reference to examples. In these examples, the elastic modulus of metal means the elastic modulus at 25°C, and the elastic modulus of resin means the elastic modulus at 100°C.

[0041] [Example 1 of the present invention] (Preparation of alumina particle dispersed polyimide solution) A polyimide resin solution with a polyimide resin concentration of 10% by mass was prepared by mixing polyimide resin A with NMP (N-methyl-2-pyrrolidone) and dissolving the polyimide resin. Polyimide resin A was selected so that the modulus of elasticity of the mixture with alumina was 0.27 GPa at 100°C. An α-alumina particle dispersion with an α-alumina particle concentration of 10% by mass was prepared by mixing alumina powder (average particle diameter: 0.3 μm) with NMP and ultrasonicating the mixture for 30 minutes. The polyimide resin solution and the alumina particle dispersion were mixed in a ratio such that the alumina concentration was 60% by volume. The resulting mixture was dispersed using a Starburst (manufactured by Sugino Machine Co., Ltd.) by repeatedly spraying at a high pressure of 50 MPa 10 times to prepare an alumina particle-dispersed polyimide resin solution. The alumina concentration was the alumina particle content in the solid material produced when the alumina particle-dispersed polyimide resin solution was heated and dried.

[0042] (Fabrication of metal base substrate) As a metal substrate, the thickness is T M is 0.7 mm, and the elastic modulus E M An aluminum substrate (length: 30 mm, width: 20 mm) with a thermal expansion coefficient of 74 GPa was prepared. The alumina particle-dispersed polyimide resin solution prepared above was applied onto this aluminum substrate by bar coating to form a coating film. Next, the aluminum substrate on which the coating film was formed was placed on a hot plate, and the temperature was increased from room temperature to 60°C at a rate of 3°C / min, heated at 60°C for 100 minutes, and then further increased to 120°C at a rate of 1°C / min, and heated at 120°C for 100 minutes to dry the coating layer. Next, the aluminum substrate was heated at 250°C for 1 minute, and then heated at 400°C for 1 minute. In this way, a coating film of a thickness T consisting of polyimide resin with dispersed alumina particles was formed on the surface of the aluminum substrate. RAn insulating layer having a thickness of 30 μm was formed, thereby obtaining an aluminum substrate with an insulating layer.

[0043] Copper foil (thickness: 70 μm, elastic modulus: 118 GPa) was laminated as a circuit layer on the insulating layer of the obtained aluminum substrate with an insulating layer. Next, the obtained laminate was heated in a vacuum at a pressure of 300°C for 120 minutes while applying a pressure of 5 MPa using a carbon jig, thereby compressing the second insulating layer and the copper foil. In this way, a metal base substrate was produced in which an aluminum substrate, an insulating layer, and copper foil were laminated in this order.

[0044] [Examples 2 and 3 of the present invention] As a metal substrate, the thickness is T M A metal base substrate was produced in the same manner as in Inventive Example 1, except that an aluminum substrate having a thickness shown in Table 1 below was used.

[0045] [Examples 4 and 5 of the present invention] Insulation layer thickness T R A metal base substrate was produced in the same manner as in Example 3 of the present invention, except that the thickness of the film was set to the thickness shown in Table 1 below.

[0046] [Example 6] A metal base substrate was produced in the same manner as in Example 3 of the present invention, except that in the preparation of the alumina particle-dispersed polyimide solution, polyimide resin A was changed to polyimide resin B. Polyimide resin B was selected so that the modulus of elasticity of a mixture with alumina at 100°C was 0.32 GPa.

[0047] [Example 7] A metal base substrate was produced in the same manner as in Example 3 of the present invention, except that in the preparation of the alumina particle-dispersed polyimide solution, polyimide resin A was changed to polyimide resin C. Polyimide resin C was selected so that the modulus of elasticity of a mixture with alumina at 100°C was 1.01 GPa.

[0048] [Examples 8 to 10] As a metal substrate, the thickness is T M is the thickness shown in Table 1 below, and the modulus of elasticity EM A metal base substrate was produced in the same manner as in Example 1 of the present invention, except that a copper substrate having an elastic modulus shown in Table 1 below was used.

[0049] [Example 11] As a metal substrate, the thickness is T M is the thickness shown in Table 1 below, and the modulus of elasticity E M A metal base substrate was produced in the same manner as in Example 1 of the present invention, except that carbon steel having an elastic modulus shown in Table 1 below was used.

[0050] [Comparative Examples 1 to 8] As a metal substrate, material, thickness T M , elastic modulus E M The thickness of the insulating layer is shown in Table 1 below. R A metal base substrate was produced in the same manner as in Example 1 of the present invention, except that the thicknesses of the layers were as shown in Table 1 below.

[0051] [evaluation] (T of metal substrate M 3 ×E M ) Metal substrate thickness T M (unit: mm) and the elastic modulus E of the metal substrate M (unit: GPa) and the product T M 3 ×E M The results are shown in Table 1 below.

[0052] (T of the insulating layer R / E R and T R / C R ) Elastic modulus of the insulating layer E R was measured by the above-mentioned method, and the elastic modulus E R (unit: GPa) vs. film thickness T R (unit: μm ) ratio T R / E R The thermal conductivity of the insulating layer, C R is measured by the above-mentioned method, and the thermal conductivity C R (unit: W / mK) R(unit: μm ) ratio T R / C R The results are shown in Table 1 below.

[0053] (thermal resistance) A heating element (TO-3P) was placed on the copper foil of a metal base substrate with a heat dissipation sheet (BFG-30A: manufactured by Denka Co., Ltd.) interposed between the copper foil and the copper foil. The metal base substrate with the heating element placed on it was pressed in the stacking direction from above the heating element with a screw of 40 Ncm torque. The thermal resistance from the heating element to the copper substrate was then measured using a T3Ster (manufactured by Siemens). The heating conditions for the heating element were 10 A and 30 seconds, and the thermal resistance measurement conditions were 0.01 A and a measurement time of 60 seconds. A similar measurement was performed on a copper substrate alone without an insulating film, and the thermal resistance was subtracted from the measured value for the metal base substrate to obtain the thermal resistance.

[0054] (crack resistance rate) A metal base substrate was cut into a size of 50 mm long x 50 mm wide. Sn-Ag-Cu solder was applied to the copper foil of the cut metal base substrate to form a solder layer measuring 25 mm long x 25 mm wide x 100 μm thick. A 25 mm square Si chip was mounted on the solder layer to prepare a test specimen. The test specimen was subjected to 3,000 thermal cycles, each cycle consisting of -30°C for 30 minutes and 105°C for 30 minutes. After thermal cycling, the test specimen was embedded in resin, and the cross section was polished to observe the specimen. The length (mm) of any cracks that occurred in the solder layer was measured. The crack resistance rate was calculated using the following formula from the length of one side of the solder layer and the measured crack length. A high crack resistance rate indicates that cracks are less likely to occur, i.e., high reliability. Crack resistance rate (%) = {(length of one side of solder layer (25 mm) - 2 × crack length) / length of one side of bonding layer (25 mm)} × 100

[0055] (warp) After measuring the crack resistance rate, the warpage of the sample was measured using a gap gauge. The sample was placed on a flat plate, and the gap between the flat plate and the edge of the sample was measured as the warpage. The largest warpage of 50 μm or less was evaluated as ◯, the warpage of 50 μm or more but not more than 70 μm was evaluated as △, and the warpage of more than 70 μm was evaluated as ×.

[0056] [Table 1]

[0057] From the results in Table 1, T M , T M 3 ×E M , T R / E R and T R / C R The metal base substrates obtained in Examples 1 to 11 of the present invention, all of which were within the range of the present invention, were excellent in heat resistance, crack resistance, and warpage. M 3 ×E M The metal base substrates obtained in Examples 2 to 7 and 9 to 11 of the present invention, which had a T of 30 or more, showed further improvements in warpage. R / E R The metal base substrates obtained in Examples 1 to 5 and 8 to 11 of the present invention, which had a T of 100 or more, had a further improved crack resistance. R / C R The metal base substrates obtained in Examples 1 to 4 and 6 to 11 of the present invention, in which the thermal resistance was 30 or less, had lower thermal resistance.

[0058] In contrast, T M 3 ×T M The metal base substrate obtained in Comparative Example 1 and T M is thinner than the range of the present invention, and T M 3 ×E M The metal base substrate obtained in Comparative Example 8, which had a T lower than the range of the present invention, showed a large warpage. M The metal base substrates obtained in Comparative Examples 2 to 6, which had a T greater than the range of the present invention, had a reduced crack resistance.R / C R The metal base substrates obtained in Comparative Examples 5 to 7, in which the value was larger than the range of the present invention, had a large thermal resistance.

[0059] [Example 12] (Preparation of alumina particle dispersed polyimide solution) An alumina particle-dispersed polyimide solution was prepared in the same manner as in Example 1 of the present invention, except that polyimide resin A was changed to polyimide resin D. Polyimide resin D was selected so that the modulus of elasticity of a mixture with alumina at 100°C was 2.15 GPa.

[0060] (Preparation of polyimide resin solution) A polyimide resin having an elastic modulus of 0.01 GPa at 100° C. was mixed with NMP, and the polyimide resin was dissolved to prepare a polyimide resin solution having a polyimide resin concentration of 10 mass %.

[0061] (Fabrication of metal base substrate) As a metal substrate, the thickness is T M is 1.0 mm, and the elastic modulus E M An aluminum substrate (length: 30 mm, width: 20 mm) with a thermal expansion coefficient of 74 GPa was prepared. The alumina particle-dispersed polyimide resin solution prepared above was applied onto this aluminum substrate by bar coating to form a coating film. Next, the aluminum substrate on which the coating film was formed was placed on a hot plate, and the temperature was increased from room temperature to 60°C at a rate of 3°C / min, heated at 60°C for 100 minutes, and then further increased to 120°C at a rate of 1°C / min, and heated at 120°C for 100 minutes to dry the coating layer. Next, the aluminum substrate was heated at 250°C for 1 minute, and then heated at 400°C for 1 minute. In this way, a coating film of a thickness T consisting of polyimide resin with dispersed alumina particles was formed on the surface of the aluminum substrate. R1 A first insulating layer having a thickness of 10 μm was formed, thereby obtaining an aluminum substrate with a first insulating layer.

[0062] Next, the polyimide resin solution prepared above was applied onto the first insulating layer of the aluminum substrate with the first insulating layer by a bar coating method to form a coating film. The formed coating film was dried by heating at 300°C to form a film of polyimide resin with a thickness of T R2 A second insulating layer having a thickness of 1.0 μm was formed in this manner. In this way, an aluminum substrate with an insulating layer comprising the first insulating layer and the second insulating layer was obtained.

[0063] Copper foil was pressure-bonded as a circuit layer onto the insulating layer of the obtained aluminum substrate with an insulating layer, in the same manner as in Invention Example 1. In this way, a metal base substrate was produced in which an aluminum substrate, an insulating layer, and copper foil were laminated in this order.

[0064] Comparative Example 9 Thickness of the first insulating layer T R1 A metal base substrate was produced in the same manner as in Invention Example 12, except that the thickness of the insulating layer was set to 30 μm and the second insulating layer was not formed.

[0065] [evaluation] Metal substrate T M 3 ×E M , T of the insulating layer R / E R (=T R1 / E R1 +T R2 / E R2 ) and T R / C R (=T R1 / C R1 +T R2 / C R2 ) was calculated using the above method. Thermal resistance, crack resistance, and warpage were also measured using the above methods. The results are shown in Table 2 below.

[0066] [Table 2]

[0067] From the results in Table 1, T M , T M 3 ×E M , T R / ER and T R / C R The metal base substrate obtained in Example 12 of the present invention, which was within the range of the present invention, was excellent in all of the thermal resistance, crack resistance, and warpage. R / E R The metal base substrate obtained in Comparative Example 9, in which the value of the crack resistance was lower than the range of the present invention, had a reduced crack resistance. Furthermore, the results of Inventive Example 12 and Comparative Example 9 show that by using a laminated insulating layer that combines a first insulating layer and a second insulating layer, it is possible to obtain a metal base substrate that is excellent in thermal resistance, crack resistance, and warpage even when the insulating layer is thinner than in the case of a single layer. [Explanation of symbols]

[0068] 10 Metal base board 20 Metal substrate 30 insulating layer 31 Insulating resin 32 Inorganic filler 40 circuit layers 50 solder 60 Electronic Components 61 Electrode terminal

Claims

1. A metal base substrate in which a metal substrate, at least one insulating layer, and a circuit layer are laminated in this order, The thickness T of the metal substrate Ｍ is in the range of 0.5 mm or more and 1.1 mm or less, The thickness T of the metal substrate Ｍ (unit: mm) to the cube of the elastic modulus E of the metal substrate at 25 ° C. Ｍ (unit: GPa) and the product T Ｍ ３ ×E Ｍ is in the range of 10 to 1000, The elastic modulus E at 100°C of each layer constituting the insulating layer Ｒ (unit: GPa) vs. film thickness T Ｒ (unit: μm) ratio T Ｒ / E Ｒ The sum of the above is within the range of 30 to 1000, The thermal conductivity C of each layer constituting the insulating layer Ｒ (unit: W / mK) vs. film thickness T Ｒ (unit: μm) ratio T Ｒ / C Ｒ The metal base substrate is characterized in that the sum of the above is in the range of 2 or more and 40 or less.

2. 2. The metal base substrate according to claim 1, wherein said metal substrate contains at least one metal selected from the group consisting of aluminum, copper, and iron.

3. 3. The metal base substrate according to claim 1, wherein the insulating layer is a single layer or a laminate.

4. 4. The metal base substrate according to claim 3, wherein the insulating layer is a single layer, and the single layer is made of a resin composition having a filler content in the range of 30% by volume to 85% by volume.

5. A metal base substrate as described in claim 3, wherein the insulating layer is a laminate having a first insulating layer formed on a metal layer and a second insulating layer laminated on the first insulating layer, and one of the first insulating layer and the second insulating layer is a layer of a resin composition having a filler content in the range of 50 volume % or more and 85 volume % or less, and the other layer is a layer of a resin composition having a resin or filler content of 1 volume % or less.

6. 6. The metal base substrate according to claim 1, wherein the insulating layer has a thickness of 100 μm or less.

7. 7. The metal base substrate according to claim 1, wherein the circuit layer has a thickness of 80 μm or less.

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