JP5038007B2 - Composition, metal-based circuit board using the composition - Google Patents

Description

The present invention relates to a composition applied to a circuit board for hybrid integration. The present invention also relates to a circuit board, a metal base circuit board, and a metal base multilayer circuit board using the composition.

A metal base circuit board in which a circuit is formed via an insulating layer made of a resin filled with an inorganic filler on a metal plate is well known, and as the insulating layer, a spherical inorganic filler is highly filled in the resin and bonded. A composition that retains sufficient force and achieves high thermal conductivity after curing is known (Patent Document 1).
JP-A-2-286768

The spherical inorganic filler is known, for example, spherical silica, spherical alumina, etc., but since it is provided by a special manufacturing method such as flame melting, the characteristics of the obtained substrate, circuit board, etc. are good. However, it has the disadvantage of being expensive in price. For this reason, it is important in the industry to search for a composition that can provide a cured product with strong adhesive strength, high thermal conductivity after curing, and excellent electrical insulation, using easily crushed inorganic fillers. Is being viewed.

That is, an object of the present invention is to use a crushed inorganic filler, have excellent adhesion to a metal plate or a metal foil, exhibit high thermal conductivity after curing, and as a result, provide a highly reliable hybrid integrated circuit. It is to provide a substrate that can be provided.

The present invention is a composition comprising an epoxy resin, a curing agent for the epoxy resin, and an inorganic filler, wherein (a) the epoxy resin has a bisphenol A type epoxy resin having an epoxy equivalent of 300 or less, and (b) the curing agent has an average molecular weight. 1,500 or less phenol novolac resin, (c) the inorganic filler is α cristobalite, the maximum particle size is 100 μm or less, the average particle size is 5 to 50 μm, and the particle size is 2.0 μm or less. It is a composition comprising fine particles having a particle content of 70% by volume or more and an average particle diameter of 0.2 to 1.5 μm .

Further , the present invention is a circuit board characterized in that an insulating layer comprising the above composition is provided on a metal plate, and a metal foil is provided on the insulating layer. A metal base circuit board comprising an insulating layer made of the composition, a metal foil provided on the insulating layer, and a circuit formed by processing the metal foil.

In addition, the present invention provides a first insulating layer made of the above-described composition on a metal plate, a circuit board on the first insulating layer, and further on the first insulating layer. A metal-based multilayer circuit board, characterized in that a second insulating layer made of the above composition is provided, and a highly exothermic electronic component is provided on the second insulating layer, preferably the first insulating layer A metal base multilayer circuit board, wherein a metal layer is provided between the first insulating layer and the second insulating layer, and more preferably, the thickness of the second insulating layer is not less than 50 μm and not more than 200 μm. The metal-based multilayer circuit board as described above.

In the composition of the present invention, an epoxy resin and a specific epoxy resin curing agent are selected, and since an inorganic filler having a specific composition with a specific particle size distribution is selected, a metal plate made of aluminum, copper, or the above alloy or the like Good adhesion to metal foil and high thermal conductivity resin hardened body, electrical parts and parts with high heat dissipation, especially for hybrid integrated circuits and circuit boards In particular, it is suitable for use in metal base circuit boards and metal base multilayer circuit boards.

The cured resin of the present invention is rich in adhesion to metal, and is excellent in electrical insulation and thermal conductivity. In a preferred embodiment, it exhibits a thermal conductivity as high as 1.5 to 3.0 W / mK. Therefore, it is suitable as a material for heat radiation of various electric parts and electronic parts including hybrid integrated circuit boards, circuit boards, particularly metal base circuit boards and metal base multilayer circuit boards.

Since the substrate of the present invention, further the metal base circuit board and the metal base multilayer circuit board of the present invention uses the above composition, the characteristics of the resin cured body are shown, and the electrical insulation and thermal conductivity are excellent. By using this, a highly reliable hybrid integrated circuit can be easily obtained.

In the present invention, an epoxy resin is used. As the epoxy resin, known epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, etc. can be used. Among these, bisphenol A type epoxy resin is electrically insulating. These are preferably selected because a cured resin body having high thermal conductivity and high heat resistance can be obtained.

The epoxy resin containing the bisphenol A type epoxy resin is more preferably 300 or less in epoxy equivalent. This is because if the epoxy equivalent is 300 or less, it is possible to prevent a decrease in Tg due to a decrease in crosslink density, which is observed when the polymer type is obtained, and hence a decrease in heat resistance. Further, when the molecular weight is increased, the liquid state becomes a solid state, and it becomes difficult to blend the inorganic filler into the curable resin, and the problem that a uniform resin composition cannot be obtained can be avoided.

The epoxy resin containing the bisphenol A type epoxy resin preferably has a hydrolyzable chlorine concentration of 600 ppm or less. When the hydrolyzable chlorine concentration is 600 ppm or less, sufficient moisture resistance as a hybrid integrated circuit substrate can be exhibited.

In the present invention, a phenol novolac resin is preferably used as the curing agent for the epoxy resin. The phenol novolac resin preferably has an average molecular weight of 1500 or less. If the average molecular weight is 1500 or less, the problem that it becomes difficult to blend the inorganic filler into the curable resin because the softening point is high can be avoided.

The phenol novolac resin preferably has a hydrolyzable chlorine concentration of 10 ppm or less. When the hydrolyzable chlorine concentration is 10 ppm or less, sufficient moisture resistance as a hybrid integrated circuit board can be secured.

In the present invention, an inorganic filler having a specific particle size distribution and a specific composition is employed. That is, an inorganic filler having a maximum particle size of 100 μm or less, a particle size of 1 to 12 μm containing 50% by volume or more, and containing α-cristobalite is selected. Thereby, the effect of the present invention can be achieved.

Furthermore, in the present invention, (a) coarse powder having a maximum particle size of 100 μm or less and a particle size of 1 to 12 μm containing 50% by volume or more and an average particle size of 5 to 50 μm; and (b) a particle size of 2 It is preferable to use a mixed powder comprising 70% by volume or more of 0.0 μm or less and a fine powder having an average particle diameter of 0.2 to 1.5 μm. When the coarse powder and the fine powder having the specific particle size distribution are mixed and used, the object of the present invention can be achieved without using an inorganic filler in which the coarse powder and the fine powder are both spherical particles. In addition, about the mixture ratio of (a) and (b), both may be mix | blended suitably, as long as 50 volume% or more of particle | grains become the range of 1-12 micrometers, what kind of range may be sufficient, According to the results of studies by the present inventors, it is preferable that (a) is 70 to 80% by mass with respect to 100% by mass of the total amount of (a) and (b).

In the present invention, the inorganic filler only needs to contain α-cristobalite. Besides, it is an electrically insulating resin such as aluminum oxide (alumina), silicon oxide (silica), magnesium oxide, aluminum nitride, silicon nitride, boron nitride. Any material can be used as long as it has a higher thermal conductivity than that. In the present invention, it is preferable to select α cristobalite which is a single crystal system of silica as the coarse powder. α-Cristobalite has a dielectric constant (25 ° C., 1 MHz) of 4.0 or less, and electrical insulation is ensured when the composition of the present invention and its cured product are used as a heat radiation material for electric and electronic parts at high frequencies. Because it is easy to do.

In addition, α cristobalite has an electric conductivity of 50 μS / cm or less, and an ionic impurity amount of 20 ppm or less such as Cl ⁻ and Na ⁺ has sufficient moisture resistance as a substrate for a hybrid integrated circuit. Since it becomes easy to ensure, it is more preferable.

As the fine powder of the inorganic filler, if the coarse powder already contains α cristobalite, a crushed product of the inorganic filler can be used. However, if the fine powder of α cristobalite is used, a cured resin having a low dielectric constant, high electrical insulation and high thermal conductivity is obtained reflecting the characteristics of α cristobalite, so α cristobalite is added to the coarse powder. There is no need for inclusion. On the other hand, when the coarse powder contains α cristobalite, silica or alumina such as α quartz or fused quartz can be used for the fine powder. In the case of α-quartz or alumina, a highly heat-conductive cured body is obtained, which is preferable. Also, if spherical particles such as spherical silica and spherical alumina are used, the fluidity of the resin composition is increased, so that the filling amount of the inorganic filler can be increased, resulting in high electrical insulation and high heat. It is also preferable because a cured resin having conductivity can be obtained.

The blending ratio of the inorganic filler is preferably 25 to 50% by mass of the epoxy resin, 34 to 70% by mass of the coarse powder of the inorganic filler, and 3 to 24% by mass of the fine powder of the inorganic filler. If it is within the above blending range, it is homogeneous and can prevent pores from being mixed and highly filled with an inorganic filler, so that a cured resin body having both good thermal conductivity and electrical insulation can be stably obtained. A substrate, a circuit substrate, and a hybrid integrated circuit which are manufactured by using them have high reliability.

The composition of the present invention can be obtained by a known method, but the method shown below prevents bubbles from being entrained in the resin composition, is stable, has excellent adhesion to metal, and has a high It is preferable because a cured resin body that is electrically insulating and excellent in thermal conductivity can be obtained.

That is, an epoxy resin and an epoxy resin curing agent are mixed, and then an inorganic filler is blended and mixed before curing. About the mixer used here, it is sufficient to use a conventionally known mixer such as a universal mixing stirrer, a planetary stirring deaerator, a pressure kneader, and the mixing conditions may be appropriately selected. There is no reason to set it.

The cured resin body of the composition of the present invention has high electrical insulation and high thermal conductivity, and also has excellent adhesive properties with metals such as aluminum, copper, and alloys thereof. Although it can be used as an insulating material for components and electronic components, it is particularly suitable as a substrate for hybrid integrated circuits and an insulating layer for circuit substrates. In a preferred embodiment, it has a thermal conductivity as high as 1.5 to 3.0 W / mK.

The present invention is a circuit board characterized in that an insulating layer made of the above composition is provided on a metal plate, and a metal foil is provided on the insulating layer. Here, aluminum, copper, iron, an alloy of the metal, or a composite plate of the metal having a thickness of 0.1 to 4.0 mm can be usually used as the metal plate, and aluminum can be used as the metal foil. A metal foil made of copper, copper, or an alloy thereof is usually selected. The circuit board is used as a substrate such as the following metal base circuit board and metal base multilayer circuit board, and reflects the characteristics of the cured product of the composition, and has excellent electrical insulation and heat dissipation properties. A highly functional circuit board can be easily provided. In addition, about the thickness of an insulating layer, 50-200 micrometers is preferable.

Further, the metal base circuit board of the present invention can be obtained by forming a circuit by processing the metal foil of the board by a conventionally known method such as etching, and the insulating layer is made of the composition. It has high characteristics.

A metal-based multilayer circuit board according to the present invention is a highly heat-generating electronic component in which a circuit board is provided on a first insulating layer made of the composition provided on a metal plate, and a second insulating layer is formed. Since the heat dissipation from the highly heat-generating electronic component is promoted and the electronic component for controlling the heat-generating component can be mounted on the circuit board, the reliability is high. There is a feature that heat-generating electronic components can be operated. The circuit board may be another metal-based circuit board, a so-called glass epoxy board based on an epoxy resin containing glass fiber, or a resin board made of a resin such as polyimide resin. It does not matter.

In the present invention, a metal layer can be provided between the first insulating layer and the second insulating layer. When this structure is adopted, the shielding effect of the circuit board can be enhanced, and heat radiation from the highly exothermic electronic component can be promoted, which is preferable. In the present invention, the thickness of the first insulating layer is preferably 50 to 200 μm, and the thickness of the second insulating layer is preferably 50 μm or more and 200 μm or less.

Since the substrate, metal base circuit board, and metal base multilayer circuit board of the present invention have an insulating layer made of the composition on a metal plate, the characteristics of the composition or a cured product thereof are reflected. Since it has excellent voltage characteristics and heat dissipation characteristics, it is suitable for use in hybrid integrated circuits. Furthermore, in a preferred embodiment, since both inorganic filler coarse powder and fine powder are made of α-cristobalite, the dielectric capacitance is small, and it is suitable as a substrate for a hybrid integrated circuit using a high frequency.

Example 1
Α cristobalite (“XPF6” manufactured by Tokai Kogyo Co., Ltd .; maximum particle size of 96 μm, containing 60 % by volume of particles of 5 to 50 μm, average particle size of 6 μm) as inorganic filler coarse powder, 55 parts by mass, inorganic filler Α cristobalite (made by Tokai Kogyo Co., Ltd., “XPF6” classified by wet elutriation classification method using natural sedimentation phenomenon: 2.0 μm or less is 70 % by volume and average particle size is 1.0 μm) 14 parts by mass was mixed to obtain a raw material inorganic filler.

20 parts by mass of bisphenol A type epoxy resin (manufactured by Japan Epoxy Resin, “EP828”), 9 parts by mass of phenol novolac resin (manufactured by Dainippon Ink and Chemicals, “TD-2131”), silane coupling agent (Nihon Unicar) 1 part by mass of “A-187” manufactured by the company was blended, and the raw material inorganic filler was mixed while kneading with a kneader at a temperature of 90 ° C. to prepare a composition (a) for a circuit board.

0.05 parts by mass of an imidazole curing accelerator (manufactured by Shikoku Kasei Co., Ltd., “TBZ”) was added as a curing accelerator to 100 parts by mass of the composition (a) to obtain a composition (b).

The composition (b) was heated at 150 ° C. for 1 hour and further at 180 ° C. for 2 hours to obtain a cured product. The thermal conductivity of this cured product was measured by a laser flash method to find 1.7 W / mK. Met. The results are shown in Table 1.

The composition (b) was applied onto an aluminum plate having a thickness of 1.5 mm so that the thickness after curing was 80 μm and heated to 100 ° C. for 0.1 hour to be in a semi-cured state. b) A copper foil having a thickness of 210 μm was laminated thereon and further heated at 180 ° C. for 2 hours to complete the curing, thereby producing a substrate for a hybrid integrated circuit.

With respect to the obtained substrate for a hybrid integrated circuit, various characteristics were examined as described later, and the results are shown in Table 2.

<Adhesion>
For the hybrid integrated circuit board, the copper foil was removed by etching, then cut to 2 cm × 10 cm, and bent to the aluminum surface side at an angle of 90 degrees. In that case, the thing which did not peel in an aluminum and an insulating layer was made into the favorable thing, and the thing in which peeling occurred was made into a defect.

<Fluidity>
Regarding the composition (b), the viscosity was measured with a B-type viscometer, and those having a room temperature (25 ° C.) viscosity exceeding 200,000 cps were determined to be poor and those having a viscosity of 200,000 cps or less were determined to be good.

<Withstand voltage>
The periphery of the copper foil of the substrate for the hybrid integrated circuit was etched, and a circular portion having a diameter of 20 mm was left as a sample. For the withstand voltage before and after exposure under conditions of a temperature of 121 ° C., a humidity of 100% RH, 2 atm, and 96 hours, the test piece was immersed in insulating oil, and an AC voltage was applied between the copper foil and the aluminum plate at room temperature. , Measured based on JISC2110. “TOS-8700” manufactured by Kikusui Electronics Co., Ltd. was used as the measuring instrument.

<Stripping strength>
A sample was processed by leaving a copper foil having a width of 10 mm from the substrate for the hybrid integrated circuit. Copper foil and a board | substrate were made into the angle of 90 degree | times, and it peeled with the pulling speed of 50 mm / min. Other conditions were based on JISC6481. Tensilon (Toyo Baldwin, “U-1160”) was used as a measuring machine.

<Dielectric loss>
The periphery of the copper foil of the substrate for the hybrid integrated circuit was etched, and a circular portion having a diameter of 20 mm was left as a sample. The measurement was performed based on JISC6481 under conditions of a temperature of 25 ° C. and a frequency of 1 MHz. An LCR meter (manufactured by Yokogawa, Hewlett-Packard Company, “HP4284”) was used as the measuring instrument.

<Relative permittivity>
First, electrostatic capacity (X; unit, F) was measured based on JISC6481 under the same conditions as the dielectric loss. The relative dielectric constant (E) is the capacitance (X; unit, F), the thickness of the insulating layer (Y; unit, m), the area of the electrode plate (Z; unit, m ² ), and the dielectric constant (8 .85 × 10 ⁻¹² ; units, F / m)
E = X × Y / (8.85 × 10 ⁻¹² × Z)
This was calculated using the following formula.

<Heat resistance>
The sample was left in a thermostat set to 200 ° C. (“PHH-201”, manufactured by Espec Corp.) for 500 hours, then cooled on a piece of wood, and the treated test piece was immersed in insulating oil at room temperature. An alternating voltage was applied between the copper foil and the aluminum plate, and the voltage at which dielectric breakdown occurred was measured.

<Thick copper foil reliability>
The evaluation was carried out as an evaluation of a hybrid integrated circuit board in which the thickness of the copper foil exceeded 210 μm. After floating in a solder bath set at 260 ° C for 2 minutes, the piece is cooled on a piece of wood, the treated piece is immersed in insulating oil, and an AC voltage is applied between the copper foil and the aluminum plate at room temperature. And measure the breakdown voltage. Moreover, the cross-section observation (scanning electron microscope) of the test piece after a process was performed, and the presence or absence of the generation | occurrence | production of the insulating layer crack in a copper foil and an insulating layer interface part was evaluated.

<Thermal resistance value>
As a measurement sample, a substrate for a hybrid integrated circuit was cut into 3 × 4 cm, leaving a 10 × 15 mm copper foil. A TO-220 type transistor was soldered on the copper foil, and fixed to the water-cooled heat radiation fin via heat radiation grease. By energizing the transistor, causing the transistor to generate heat, measuring the temperature difference between the transistor surface and the back of the metal base, measuring the thermal resistance value, and correcting the thermal resistance value of the heat dissipating grease, A: Unit, K / W) was measured.

<Thermal conductivity>
The thermal conductivity (H; unit, W / mK) is the thermal resistance value (A; unit, K / W), the thickness of the insulating layer of the specimen (B; unit, m), and the transistor mounting area (C From the unit m ² )
X = B / (A × C)
This was calculated using the following formula.

<Processability>
The hybrid integrated circuit board was punched with a punch, and the amount of wear of the punch after 10,000 shots was measured.

<Creep discharge withstand voltage>
As a measurement sample, a straight copper circuit was formed at a distance of 2 mm from the creeping surface of the hybrid integrated circuit board. An AC voltage was applied between the copper foil circuit and the aluminum plate at room temperature, and the voltage generated by creeping discharge was measured.

<Power loss>
Capacitance (X; unit, F) was measured based on JISC6481 under the same conditions as the dielectric loss. Power loss (G) is calculated from capacitance (X; unit, F), device operating frequency (H; 400 kHz) and operating voltage (I; 220 V).
G = (X × I ² × H) / 2
This was calculated using the following formula.

(Examples 2 to 4, Reference Examples 1 to 3 )
The composition and the cured resin body, substrate, metal base circuit board, and hybrid integration were obtained in the same manner as in Example 1 except that the types and blending amounts of the inorganic filler coarse powder and fine powder were changed as shown in Table 1. A circuit was fabricated and evaluated. The results are shown in Tables 1 and 2.

(Comparative Examples 1-5)
A composition and a cured resin body, a substrate, a circuit board, and a hybrid integrated circuit were prepared and evaluated in the same manner as in Example 1 except that the types of curing agent, coarse powder, and fine powder and the blending amounts thereof were changed. . The results are shown in Tables 3 and 4.

(Example 5 )
On the aluminum plate having a thickness of 1.5 mm, the composition (b) of Example 1 was applied so that the thickness of the first insulating layer after curing was 150 μm, and heated at 100 ° C. for 0.1 hour to be semi-cured. After making it into a state, a copper foil having a thickness of 35 μm was laminated on the composition (b) and further heated at 180 ° C. for 2 hours to complete the curing. The composition (b) is further applied onto the obtained circuit board so that the insulating layer thickness after curing is 50 μm, heated to 100 ° C. for 0.1 hour to be in a semi-cured state, and then the composition (b ) A copper foil having a thickness of 210 μm is laminated thereon, and further cured by heating at 180 ° C. for 2 hours to produce a metal-based multilayer circuit board for a hybrid integrated circuit . The outer layer was evaluated. The results are shown in Table 5, Table 6, and Table 7.

(Example 6 )
A metal-based multilayer circuit board was produced in the same manner as in Example 5 except that the thickness of the second insulating layer was changed to 200 μm, and the multilayer circuit board body and the outer layers of the multilayer circuit board were evaluated. The results are shown in Table 5, Table 6, and Table 7.

(Comparative Examples 6-7)
A composition and a cured resin body, a substrate, a circuit board, and a hybrid integrated circuit were produced in the same manner as in Example 5 except that the types of hardener, coarse powder, fine powder and the blending amounts thereof were changed, and a multilayer circuit was produced. The board body and the outer layer of the multilayer circuit board were evaluated. The results are shown in Table 5, Table 6, and Table 7.

Claims (6)

“A composition comprising an epoxy resin, a curing agent for the epoxy resin, and an inorganic filler, wherein (a) the epoxy resin is a bisphenol A type epoxy resin having an epoxy equivalent of 300 or less, and (b) the average molecular weight is 1,500. The following phenol novolac resin, (c) the inorganic filler is α cristobalite, the maximum particle size is 100 μm or less, and the average particle size is 5 to 50 μm. A composition comprising a fine powder which is contained by volume% or more and has an average particle diameter of 0.2 to 1.5 μm . An insulating layer made of the composition according to claim 1 is provided on a metal plate, and a metal foil is provided on the insulating layer. A metal base comprising an insulating layer made of the composition according to claim 1 provided on a metal plate, a metal foil provided on the insulating layer, and a circuit formed by processing the metal foil. Circuit board. On a metal plate, a first insulating layer comprising the composition of claim 1 provided, provided with a circuit board on the first insulating layer, further according to claim 1, wherein said first insulating layer A metal-based multilayer circuit board comprising a second insulating layer made of the above composition and a high heat generating electronic component provided on the second insulating layer. The metal-based multilayer circuit board according to claim 4 , wherein a metal layer is provided between the first insulating layer and the second insulating layer. Metal base multilayer circuit board according to claim 4 or claim 5, wherein the thickness of the second insulating layer is equal to or is 50μm or more 200μm or less.