JP2020136577A - Heat dissipation substrate - Google Patents

Abstract

To provide a heat dissipation substrate which is hardly subjected to cracking in solder even if going through cooling and heating cycles with an electronic component mounted thereon by the solder, and which is low in heat resistance.SOLUTION: A heat dissipation substrate comprises: a thermally conductive substrate; an insulator layer laminated on one face of the thermally conductive substrate; and a circuit layer laminated on a face of the insulator layer on a side opposite to a thermally conductive substrate side. The thermally conductive substrate contains at least one heat conductive material selected from a group consisting of graphite, a graphite-based aluminum composite material, and an aluminum-based silicon carbide composite material. The insulator layer contains a resin, and ceramic particles dispersed in the resin. The content of the ceramic particles falls within a range of 60-80 vol.%.SELECTED DRAWING: Figure 1

Description

The present invention relates to a heat dissipation substrate.

The substrate for mounting an electronic component such as a semiconductor element is preferably a heat radiating substrate that can efficiently dissipate heat generated by the electronic component to the outside. As the heat radiating substrate, a metal substrate is used as the base substrate, and a metal base substrate in which the metal substrate, the insulating layer, and the circuit layer are laminated in this order is known. Electronic components are joined on top of the circuit layer via solder. In the metal base substrate having such a configuration, the heat generated in the electronic component is transferred to the metal substrate via the insulating layer and dissipated from the metal substrate to the outside.

The insulating layer of the metal base substrate is generally formed of an insulating resin composition containing a resin having excellent insulating properties and ceramic particles having excellent thermal conductivity (thermally conductive filler, inorganic filler). As the resin for the insulating layer, a polyimide resin, a polyamide-imide resin, and a silicone resin are used. For example, Patent Document 1 discloses a metal-clad laminate using a polyimide resin layer containing a thermally conductive filler in the range of 40 to 80 vol% as an insulating layer. Further, in Patent Document 2, the resin forming the insulating layer is a silicone resin composed of a polydimethylsiloxane skeleton, the inorganic filler in the insulating layer is 45 to 60% by volume, and 25% by mass or more of the inorganic filler. A circuit board in which is crystalline silica is disclosed.

Japanese Patent No. 5665449 Japanese Unexamined Patent Publication No. 2017-152610

By the way, if the difference in thermal expansion coefficient between the metal base substrate and the electronic component bonded to the metal base substrate via solder is large, the electronic component and the metal are affected by the on / off of the electronic component and the cooling / heating cycle due to the external environment. The stress applied to the solder that joins the base substrate increases, and solder cracks are likely to occur. The metal substrate of the metal base substrate generally has a large coefficient of thermal expansion, and the electronic component usually made of ceramic generally has a low coefficient of thermal expansion. Therefore, it is preferable that the stress applied to the solder joining the electronic component and the metal base substrate by the cooling / heating cycle can be relaxed by the insulating layer.

The polyimide resin containing the heat conductive filler used as the insulating layer of the metal-clad laminate described in Patent Document 1 in the range of 40 to 80 vol% generally has a large content of the heat conductive filler. As a result, the thermal conductivity is improved and the thermal resistance is lowered. However, since the elastic modulus increases as the content of the thermally conductive filler increases, it may be difficult to relieve the stress applied to the solder by the thermal cycle in the insulating layer using this. It was.

On the other hand, the silicone resin described in Patent Document 2 has a lower elastic modulus than the polyimide resin or the polyamide-imide resin. However, even when a silicone resin is used, the elastic modulus increases as the content of the thermally conductive filler increases. Therefore, simply using the silicone resin as the resin for the insulating layer causes soldering by a cold heat cycle. It is difficult to sufficiently reduce the stress applied to the resin.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is that solder cracks are unlikely to occur even if a cold heat cycle is applied in a state where electronic components are joined via solder. An object of the present invention is to provide a heat radiating substrate having a low thermal resistance.

In order to solve the above problems, the heat radiating substrate of the present invention includes a thermally conductive substrate, an insulating layer laminated on one surface of the thermally conductive substrate, and the thermally conductive substrate side of the insulating layer. The thermally conductive substrate comprises a circuit layer laminated on the opposite surface, and the thermally conductive substrate is at least one thermally conductive material selected from the group consisting of graphite, a graphite-based aluminum composite material and an aluminum-based silicon carbide composite material. The insulating layer contains a resin and ceramic particles dispersed in the resin, and the content of the ceramic particles is in the range of 60% by volume or more and 80% by volume or less.

According to the heat radiating substrate of the present invention, the heat conductive substrate contains at least one heat conductive material selected from the group consisting of graphite, graphite-based aluminum composite material and aluminum-based silicon carbide composite material, and therefore the heat conductive substrate. The coefficient of thermal expansion of the aluminum is reduced, and the coefficient of thermal expansion of the entire heat dissipation substrate is lowered. Therefore, even if a cold cycle is applied in a state where the electronic components are joined via the solder, the stress applied to the solder is reduced due to the difference in the coefficient of thermal expansion between the electronic components and the heat dissipation substrate. Therefore, the occurrence of solder cracks is less likely to occur. Further, since the content of the ceramic particles in the insulating layer is within the range of 60% by volume or more and 80% by volume or less, and the content of the ceramic particles is large, the thermal conductivity of the insulating layer is improved and the thermal resistance of the entire heat radiation substrate is increased. It gets lower.

Here, in the heat radiating substrate of the present invention, an adhesion layer containing a cured product of a thermosetting resin may be provided between the heat conductive substrate and the insulating layer.
In this case, since it is difficult for the adhesive layer to form a gap between the heat conductive substrate and the insulating layer, the thermal resistance between the heat conductive substrate and the insulating layer is reduced, thereby reducing the thermal resistance of the entire heat radiating substrate. It can be lowered even more reliably.

According to the present invention, it is possible to provide a heat-dissipating substrate in which solder cracks are less likely to occur and thermal resistance is low even if a cold-heat cycle is applied in a state where electronic components are mounted via solder.

It is sectional drawing of the module using the heat dissipation substrate which concerns on one Embodiment of this invention.

The heat radiating substrate according to the embodiment of the present invention will be described below with reference to the attached drawings.
FIG. 1 is a cross-sectional view of a module using a heat radiating substrate according to an embodiment of the present invention.

As shown in FIG. 1, the module 1 includes a heat radiating board 10 and an electronic component 3 mounted on the heat radiating board 10 via solder 2. The heat radiating substrate 10 is a laminate in which an insulating layer 30 and a circuit layer 40 are laminated in this order on a heat conductive substrate 20. An adhesion layer 50 is provided between the heat conductive substrate 20 and the insulating layer 30. The adhesion layer 50, the insulation layer 30, and the circuit layer 40 are respectively laminated in the direction perpendicular to one surface of the heat conductive substrate 20 (Z direction in FIG. 1). The circuit layer 40 is formed in a circuit pattern.

The heat conductive substrate 20 is a member that is a base of the heat radiating substrate 10. The thermally conductive substrate 20 contains at least one thermally conductive material selected from the group consisting of graphite, a graphite-based aluminum composite material and an aluminum-based silicon carbide composite material. These heat conductive materials have a low coefficient of thermal expansion and have excellent heat conductivity.

The graphite-based aluminum composite is a composite composed of aluminum and graphite.

The aluminum-based silicon carbide composite material (Al-SiC) is a composite material composed of aluminum and silicon carbide.

The thermally conductive substrate 20 (graphite substrate) containing graphite contains flat graphite and a graphene aggregate formed by depositing single-layer or multi-layer graphene so that the flat graphite folds its basal surface. , It is preferable that the graphene aggregate has a laminated structure as a binder.

The flat graphite has a basal surface on which a carbon hexagonal network surface appears and an edge surface on which an end portion of the carbon hexagonal network surface appears. As the flat graphite, scaly graphite, scaly graphite, earthy graphite, flaky graphite, kiss graphite, pyrolytic graphite, highly oriented pyrolytic graphite and the like can be used. Here, the average particle size of graphite as seen from the basal surface is preferably in the range of 10 μm or more and 1000 μm or less, and more preferably in the range of 50 μm or more and 800 μm or less. By keeping the average particle size of graphite within the above range, thermal conductivity is improved. Further, the thickness of graphite is preferably in the range of 1 μm or more and 50 μm or less, and more preferably in the range of 1 μm or more and 20 μm or less. By setting the thickness of graphite within the above range, the orientation of graphite is appropriately adjusted. Further, by setting the thickness of graphite within the range of 1/1000 to 1/2 of the particle size seen from the basal surface, excellent thermal conductivity and the orientation of graphite are appropriately adjusted.

The graphene aggregate is a deposit of single-layer or multi-layer graphene, and the number of layers of the multi-layer graphene is, for example, 100 layers or less, preferably 50 layers or less. This graphene aggregate can be produced, for example, by dropping a graphene dispersion in which single-layer or multi-layer graphene is dispersed in a solvent containing a lower alcohol or water onto a filter paper and depositing the graphene while separating the solvent. It is possible. Here, the average particle size of the graphene aggregate is preferably in the range of 1 μm or more and 1000 μm or less. By keeping the average particle size of the graphene aggregate within the above range, the thermal conductivity is improved. Further, the thickness of the graphene aggregate is preferably in the range of 0.05 μm or more and less than 50 μm. By keeping the thickness of the graphene aggregate within the above range, the strength of the graphite substrate is ensured.

The insulating layer 30 is a layer for insulating the heat conductive substrate 20 and the circuit layer 40. The insulating layer 30 is formed of an insulating resin composition containing the insulating resin 31 and the ceramic particles 32. By forming the insulating layer 30 from an insulating resin composition containing an insulating resin 31 having high insulating properties and ceramic particles 32 having high thermal conductivity, heat conduction from the circuit layer 40 while maintaining insulating properties. The thermal resistance of the entire heat radiating substrate 10 up to the sex substrate 20 can be further reduced.

The insulating resin 31 is preferably a polyimide resin, a polyamide-imide resin, or a mixture thereof. Since the polyimide resin and the polyamide-imide resin have an imide bond, they have excellent heat resistance and mechanical properties.

As the ceramic particles 32, silica (silicon dioxide) particles, alumina (aluminum oxide) particles, boron nitride (BN) particles, titanium oxide particles, alumina-doped silica particles, alumina hydrate particles, aluminum nitride particles and the like can be used. it can. As the ceramic particles 32, one type may be used alone, or two or more types may be used in combination. Among these ceramic particles, alumina particles are preferable because they have high thermal conductivity. The form of the ceramic particles 32 is not particularly limited, but is preferably agglomerated particles of fine ceramic particles or single crystal ceramic particles.

The agglomerated particles of the fine ceramic particles may be agglomerates in which the primary particles are relatively weakly linked, or may be aggregates in which the primary particles are relatively strongly linked.
Further, the aggregated particles may form a particle aggregate in which the aggregated particles are further aggregated. Since the primary particles of the ceramic particles 32 form aggregated particles and are dispersed in the insulating layer 30, a network is formed by mutual contact between the ceramic particles 32, and heat is conducted between the primary particles of the ceramic particles 32. This facilitates the process and improves the thermal conductivity of the insulating layer 30.

Commercially available products of aggregated particles of fine ceramic particles include AE50, AE130, AE200, AE300, AE380, AE90E (all manufactured by Nippon Aerosil Co., Ltd.), T400 (manufactured by Wacker Co., Ltd.), SFP-20M (manufactured by Denka Co., Ltd.). ), Alu65 (manufactured by Nippon Aerosil Co., Ltd.), alumina particles such as AA-04 (manufactured by Sumitomo Chemical Co., Ltd.), boron nitride particles such as AP-170S (manufactured by Maruka), AEROXIDE (R) TiO2 P90 Titanium oxide particles such as (manufactured by Nippon Aerosil Co., Ltd.), alumina-doped silica particles such as MOX170 (manufactured by Nippon Aerosil Co., Ltd.), alumina hydrate particles manufactured by Sasol, and the like can be used.

The single crystal ceramic particles are preferably α-alumina single crystal particles having a crystal structure of α-alumina (αAl ₂ O ₃ ). Commercially available products of α-alumina single crystal particles include AA-03, AA-04, AA-05, AA-07, and AA-1.5 of the Advanced Alumina (AA) series sold by Sumitomo Chemical Co., Ltd. Can be used.

The content of the ceramic particles 32 in the insulating layer 30 is in the range of 60% by volume or more and 80% by volume or less. If the content of the ceramic particles 32 is too small, the thermal conductivity of the insulating layer 30 may not be sufficiently improved, and the thermal resistance of the entire heat radiating substrate 10 may increase. On the other hand, if the content of the ceramic particles 32 becomes too large, the content of the insulating resin 31 decreases relatively, the elastic modulus of the insulating layer 30 becomes too high, and the insulating layer 30 is imparted to the solder 2 by the thermal cycle. It becomes difficult for the insulating layer 30 to relieve the stress, and solder cracks may easily occur.
The film thickness of the insulating layer 30 is not particularly limited, but is preferably in the range of 1 μm or more and 200 μm or less, and particularly preferably in the range of 3 μm or more and 100 μm or less.

The content of the ceramic particles 32 in the insulating layer 30 can be determined, for example, as follows.
The insulating layer 30 is heated in the air at 400 ° C. for 12 hours to thermally decompose and remove the insulating resin 31, and recover the remaining ceramic particles 32. The weight of the recovered ceramic particles 32 is measured, and the content (weight base) (weight%) of the ceramic particles 32 is calculated from the weight of the insulating layer 30 before heating. The weight-based content is converted to a volume-based content (volume%) using the density of the insulating resin and the density of the ceramic.

Specifically, the weight of the ceramic particles recovered by heating is Wa (g), the weight of the insulating layer before heating is Wf (g), the density of the ceramic is Da (g / cm ³ ), and the density of the insulating resin. Is Dr (g / cm ³ ), and the content (% by weight) of the ceramic particles is calculated from the following formula.
Ceramic particle content (% by weight) = Wa / Wf x 100
= Wa / {Wa + (Wf-Wa)} x 100

Next, the content (volume%) of the ceramic particles is calculated from the following formula.
Ceramic particle content (volume%) = (Wa / Da) / {(Wa / Da) + (Wf-Wa) / Dr} × 100

The adhesion layer 50 is a layer for bringing the heat conductive substrate 20 and the insulating layer 30 into close contact with each other to prevent the formation of a gap between the heat conductive substrate 20 and the insulating layer 30. The adhesion layer 50 preferably contains a cured product of a thermosetting resin. As the thermosetting resin, a silicone resin, an epoxy resin, a polyamide-imide resin, a polyimide resin and the like can be used. The silicone resin includes a modified silicone resin into which various organic groups have been introduced. Examples of modified silicone resins include polyimide-modified silicone resins, polyester-modified silicone resins, urethane-modified silicone resins, acrylic-modified silicone resins, olefin-modified silicone resins, ether-modified silicone resins, alcohol-modified silicone resins, fluorine-modified silicone resins, and amino-modified. Examples thereof include silicone resins, mercapto-modified silicone resins, and carboxy-modified silicone resins. Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak type epoxy resin, aliphatic type epoxy resin, and glycidylamine type epoxy resin. One of these resins may be used alone, or two or more of these resins may be used in combination.

Inorganic particles may be dispersed in the adhesion layer 50 in order to improve thermal conductivity. Ceramic particles can be used as the inorganic particles. Examples of ceramic particles include silica particles, alumina particles, boron nitride particles, titanium oxide particles, alumina-doped silica particles, alumina hydrate particles, and aluminum nitride particles.

As the material of the circuit layer 40, aluminum, copper, silver, gold, tin, iron, nickel, chromium, molybdenum, tungsten, palladium, titanium, zinc and alloys of these metals can be used. Among these metals, aluminum and copper are preferable. The film thickness of the circuit layer 40 is in the range of 10 μm or more and 1000 μm or less, preferably in the range of 20 μm or more and 100 μm or less. If the film thickness of the circuit layer 40 becomes too thin, the thermal resistance may increase. On the other hand, if the film thickness of the circuit layer 40 becomes too thick, it may be difficult to form a circuit pattern by etching.

Examples of the electronic component 3 mounted on the circuit layer 40 are not particularly limited, and examples thereof include a semiconductor element, a resistor, a capacitor, and a crystal oscillator. Examples of semiconductor elements include MOSFETs (Metal-oxide-semiconductor field effect transistors), IGBTs (Insulated Gate Bipolar Transistor), LSIs (Large Scale Integration), LEDs (Light Emitting Diodes), LED Chips, and LED-CSPs (LED-Chips). Size Package).

Next, a method of manufacturing the heat radiating substrate 10 of the present embodiment will be described.
The heat radiating substrate 10 of the present embodiment can be manufactured, for example, as follows. First, the insulating layer 30 and the adhesive layer 50 are laminated in this order on a circuit layer forming base material (for example, aluminum foil, copper foil) forming the circuit layer 40 to prepare an insulating laminated body sheet. To do. Next, the adhesion layer 50 of the produced insulating laminate sheet and the heat conductive substrate 20 are joined.

As a method of forming the insulating layer 30 made of the insulating resin composition containing the insulating resin 31 and the ceramic particles 32 on the substrate for forming the circuit layer, a coating method or an electrodeposition method can be used.

In the coating method, an insulating layer forming coating liquid containing an insulating resin 31, ceramic particles 32, and a solvent is applied to the surface of a circuit layer forming base material to form a coating layer, and then the coating layer is heated. This is a method of forming the insulating layer 30 by drying. As a method of applying the coating liquid for forming an insulating layer to the surface of a substrate for forming a circuit layer, a spin coating method, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, etc. A dip coat method or the like can be used.

In the electrodeposition method, a circuit layer forming base material and an electrode are immersed in an electrodeposition solution in which charged insulating resin particles and ceramic particles are dispersed, and between the circuit layer forming base material and the electrode. By applying a DC voltage, insulating resin particles and ceramic particles are electrodeposited on the surface of the circuit layer forming base material to form an electrodeposition layer, and then the electrodeposition layer is heated and dried to form an insulating layer 30. Is a method of forming. The electrodeposition liquid can be prepared, for example, by adding a poor solvent for the insulating resin to an insulating resin solution containing ceramic particles to precipitate the insulating resin. For example, water can be used as the poor solvent for the insulating resin.

A coating method can be used as a method for forming the adhesion layer 50 on the insulating layer 30.
The adhesion layer 50 forms a coating layer by applying a coating liquid for forming an adhesion layer containing a resin for forming the adhesion layer, a solvent, and a heat conductive filler added as needed on the surface of the insulating layer 30. It can then be formed by heating and drying the coating layer. Examples of the method of applying the coating liquid for forming the adhesive layer to the surface of the insulating layer 30 include a spin coating method, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, and a dip coating method. Can be used.

As a method of joining the adhesive layer 50 of the insulating laminate sheet and the thermally conductive substrate 20, the adhesion layer 50 of the insulating laminate sheet and the thermally conductive substrate 20 are laminated, and then the insulating laminate sheet and the insulating laminate sheet are combined. A method of heating the thermally conductive substrate 20 while pressurizing it can be used. The heating is preferably performed in a non-oxidizing atmosphere (for example, in a nitrogen atmosphere or in a vacuum) so that the circuit layer forming base material and the heat conductive substrate 20 are not oxidized.

According to the heat dissipation substrate 10 according to the present embodiment having the above configuration, the heat conductive substrate 20 is selected from at least a group consisting of graphite, graphene, a graphite-based aluminum composite material and an aluminum-based silicon carbide composite material. Since it contains one kind of heat conductive material, the heat expansion rate of the heat conductive substrate 20 is reduced, and the heat expansion rate of the entire heat radiation substrate is lowered. Therefore, even if a cold cycle is applied in a state where the electronic component 3 is joined via the solder 2, the stress applied to the solder 2 is reduced due to the difference in the coefficient of thermal expansion between the electronic component 3 and the heat radiating substrate 10. Therefore, the occurrence of solder cracks is less likely to occur. Further, since the content of the ceramic particles 32 in the insulating layer 30 is within the range of 60% by volume or more and 80% by volume or less and the content of the ceramic particles 32 is large, the thermal conductivity of the insulating layer 30 is improved and the heat dissipation substrate 10 is used. The overall thermal resistance is low.

In the heat radiating substrate 10 of the present embodiment, when the adhesive layer 50 containing the cured product of the thermosetting resin is provided between the thermally conductive substrate 20 and the insulating layer 30, the adhesive layer 50 provides thermal conductivity. Since it is difficult to form a gap between the substrate 20 and the insulating layer 30, the thermal resistance between the thermally conductive substrate 20 and the insulating layer 30 is reduced, whereby the thermal resistance of the entire heat radiating substrate 10 is further lowered. can do.

Although the embodiments of the present invention have been described above, the present invention is not limited to this, and can be appropriately changed without departing from the technical idea of the invention.
For example, in the present embodiment, the configuration in which the adhesion layer 50 is provided between the heat conductive substrate 20 and the insulating layer 30 has been described, but the present invention is not limited to this. When the insulating layer 30 alone can sufficiently secure the adhesiveness with the heat conductive substrate 20, the adhesive layer 50 may not be provided. Further, in order to reduce the thermal resistance between the insulating layer 30 and the circuit layer 40, an adhesion layer may be provided between the insulating layer 30 and the circuit layer 40.

[Example 1 of the present invention]
(Preparation of polyamic acid solution)
A separable flask having a capacity of 300 mL was charged with 4,4'-diaminodiphenyl ether and NMP (N-methyl-2-pyrrolidone). The amount of NMP was adjusted so that the concentration of the obtained polyamic acid was 40% by mass. After stirring at room temperature to completely dissolve 4,4'-diaminodiphenyl ether, a predetermined amount of tetracarboxylic dianhydride was added little by little so that the internal temperature did not exceed 30 ° C. Then, stirring was continued for 16 hours under a nitrogen atmosphere to prepare a polyamic acid (polyimide resin precursor) solution.

(Preparation of ceramic particle-dispersed polyamic acid solution)
As ceramic particles, α-alumina single crystal particles (average particle diameter: 0.5 μm) were prepared. 1.0 g of the prepared α-alumina single crystal particles was added to 10 g of NMP and sonicated for 30 minutes to prepare an α-alumina single crystal particle dispersion.

Next, the above polyamic acid solution, the above ceramic particle dispersion, and NMP are mixed, and the polyamic acid content is 5% by mass, and the total amount of the polyimide resin component and α-alumina single crystal particles generated by heating. A mixture was prepared in which the content of α-alumina single crystal particles was 60% by volume. Subsequently, the obtained mixture was subjected to a dispersion treatment in which a high-pressure injection treatment at a pressure of 50 MPa was repeated 10 times using a starburst manufactured by Sugino Machine Limited to prepare a ceramic particle-dispersed polyamic acid solution.

(Preparation of insulating laminate sheet)
The above ceramic particle-dispersed polyamic acid solution was applied to a copper foil having a thickness of 40 μm by a dip coating method to form a coating film. Next, the copper foil on which the coating film was formed was placed on a hot plate, the temperature was raised from room temperature to 60 ° C. at a heating rate of 3 ° C./min, heated at 60 ° C. for 100 minutes, and then further 1 ° C./min. The temperature was raised to 120 ° C. at a heating rate, heated at 120 ° C. for 100 minutes, and dried to obtain a dry film. Then, the dry film was heated at 250 ° C. for 1 minute and then at 400 ° C. for 1 minute to form an insulating layer having a thickness of 20 μm.

Next, a thermosetting polyimide silicone solution (SMP-5008PGMEA, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the surface of the above insulating layer at a rotation speed of 4000 rpm by a spin coating method, dried at 150 ° C., and dried. An adhesion layer having a thickness of 2 μm was formed. In this way, an insulating laminate sheet composed of a copper foil, an insulating film, and an adhesive layer was produced.

(Making a heat dissipation board)
As a heat conductive substrate, a graphite substrate (manufactured by InALA) containing flat graphite and a graphene aggregate was prepared. The adhesion layer of the above-mentioned insulating laminate sheet and the graphite substrate were superposed. Next, the insulating laminate sheet and the graphite substrate were heated at 300 ° C. for 120 minutes while being pressurized at a pressure of 10 MPa, and the graphite substrate and the insulating laminate sheet were thermocompression-bonded to prepare a heat-dissipating substrate.

[Examples 2 to 5 of the present invention]
A heat radiating substrate was produced in the same manner as in Example 1 of the present invention, except that the content of the ceramic particles in the insulating layer was set to the amount shown in Table 1 below. The content of the ceramic particles in the insulating layer was adjusted by changing the content of the α-alumina single crystal particles in the ceramic particle-dispersed polyamic acid solution.

[Examples 6 to 8 of the present invention]
Except for the fact that a graphite-based aluminum composite substrate (ACM-a manufactured by Advance complex) was used as the heat conductive substrate and the content of ceramic particles in the insulating layer was set to the amount shown in Table 1 below. A heat dissipation substrate was produced in the same manner as in Example 1 of the present invention.

[Examples 9 to 11 of the present invention]
Example 1 of the present invention except that an AlSiC substrate (AC-AlSiC manufactured by Advance Company) was used as the heat conductive substrate and the content of ceramic particles in the insulating layer was set to the amount shown in Table 1 below. A heat dissipation substrate was produced in the same manner as in the above.

[Comparative Examples 1 to 5]
A heat-dissipating substrate was produced in the same manner as in Example 1 of the present invention, except that a copper substrate was used as the heat conductive substrate and the content of ceramic particles in the insulating layer was set to the amount shown in Table 1 below.

[Comparative Examples 6 to 9]
A heat radiating substrate was produced in the same manner as in Example 1 of the present invention, except that the content of the ceramic particles in the insulating layer was set to the amount shown in Table 1 below.

[Evaluation]
(Preparation of test piece)
A test body in which an LED element was mounted on a heat radiating substrate was produced as follows.
First, the copper foil (circuit layer) of the heat dissipation substrate was etched to form a circuit pattern. Sn-Ag-Cu solder (manufactured by Senju Metal Industry Co., Ltd .: M705) was applied to the circuit pattern to form a solder layer having a thickness of 100 μm. Then, an LED element (Oslon compact) was mounted on the solder layer and heated in a reflow furnace to prepare a test piece.

(Thermal resistance)
The thermal resistance of the prepared test piece was measured using T3Star. The test piece was attached to a cold plate at 25 ° C. with a torque of 5 N cm via a heat radiating sheet (TC-300, manufactured by Denki Kagaku Kogyo Co., Ltd.). Then, the thermal resistance was evaluated under the conditions of a heating current of 1 A, a heating time of 60 seconds, a measurement time of 300 seconds, and a measurement current of 10 mA. Table 1 shows the values obtained by reciprocal of the thermal resistance. The values in Table 1 are relative values with the value of the heat radiating substrate produced in Example 1 of the present invention as 1.00.

(Crack length of solder layer after cooling cycle)
The prepared test piece was subjected to 3000 cycles of cooling and heating in which one cycle was −40 ° C. × 30 minutes to 150 ° C. × 30 minutes. The test piece after the cold cycle was applied was embedded with resin, and the cross section was polished. The cross section of the solder layer of the test piece was observed, and the length (μm) of cracks generated in the solder layer was measured. Table 1 shows the values obtained by reciprocaling the length. The values in Table 1 are relative values with the value of the heat radiating substrate produced in Example 1 of the present invention as 1.00.

Comparing the heat-dissipating substrate produced in Examples 1 to 11 of the present invention with the heat-dissipating substrate produced in Comparative Examples 4 and 5, the heat conductive substrate includes a graphite substrate, a graphite-based aluminum composite substrate, and an AlSiC substrate (aluminum-based carbide). It can be seen that by using the silicon composite material substrate), it is possible to reduce the occurrence of solder cracks due to the thermal cycle while maintaining low thermal resistance, and the reliability is improved. It is considered that this is because the difference in the coefficient of thermal expansion between the LED element laminated on the circuit layer of the heat radiating substrate and the thermally conductive substrate is reduced, so that the stress applied to the solder by the thermal cycle is reduced.

Further, comparing the heat radiating substrate produced in Examples 1 to 5 of the present invention with the heat radiating substrate produced in Comparative Examples 1 to 3 and 6 to 8, it is heat that the content of the ceramic particles in the insulating layer is 60% by volume or more. It can be seen that the resistance is reduced. On the other hand, from the results of the heat radiating substrate produced in Comparative Example 9, it can be seen that when the content of the ceramic particles in the insulating layer exceeds 80% by volume, the occurrence of solder cracks due to the thermal cycle increases and the reliability decreases. It is considered that this is because the stress applied to the solder by the cooling / heating cycle becomes large because the insulating layer becomes too hard.

Further, when the heat radiating substrate produced in Examples 1 to 5 of the present invention is compared with the heat radiating substrate produced in Examples 6 to 11, solder cracks are more likely to occur when the graphite substrate is used as the thermally conductive substrate. It can be seen that there is a tendency for both reliability and heat dissipation to be compatible at a high level by reducing the heat resistance and lowering the thermal resistance.

1 Module 2 Solder 3 Electronic components 10 Heat dissipation board 20 Thermal conductive board 30 Insulation layer 31 Insulation resin 32 Ceramic particles 40 Circuit layer 50 Adhesion layer

Claims (2)

A thermally conductive substrate, an insulating layer laminated on one surface of the thermally conductive substrate, and a circuit layer laminated on a surface of the insulating layer opposite to the thermally conductive substrate side are provided.
The thermally conductive substrate contains at least one thermally conductive material selected from the group consisting of graphite, a graphite-based aluminum composite material and an aluminum-based silicon carbide composite material.
The heat-dissipating substrate comprises a resin and ceramic particles dispersed in the resin, and the content of the ceramic particles is in the range of 60% by volume or more and 80% by volume or less. The heat radiating substrate according to claim 1, further comprising an adhesion layer containing a cured product of a thermosetting resin between the thermally conductive substrate and the insulating layer.

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