JP2017197648A - Resin composition for circuit board and metal base circuit board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal base circuit board which provides a cured body of a resin composition for circuit board having uniform voltage-resistance characteristics, and has low defective fraction which cannot be conventionally obtained.SOLUTION: A resin composition for circuit board contains a thermosetting resin, an inorganic filler and a smoothing agent, where the smoothing agent is polyether-modified silicone, and the resin composition for circuit board contains 0.05-2.0 mass% of the smoothing agent and 45-95 mass% of the inorganic filler having the maximum particle size of 30-120 μm, further contains one or two selected from polyisoprene and polybutadiene. A metal base circuit board is obtained by applying the resin composition for circuit board onto a substrate, where when the resin composition for circuit board is applied to the substrate with a thickness of 30-150 μm, there is no defect having a diameter of 10 μm or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a resin composition used for a circuit board on which various electronic / electrical components including a semiconductor element are mounted, and a metal base circuit board using the resin composition.

Various circuit boards have been put to practical use in order to form a hybrid integrated circuit by mounting electronic / electrical components such as semiconductor elements. These are classified into resin circuit boards, ceramic circuit boards, metal base circuit boards, and the like based on the board material of the circuit board.

Resin circuit boards are inexpensive but limited to relatively small power applications because of the poor thermal conductivity of the substrate. Ceramic circuit boards are suitable for relatively large power applications by taking advantage of the excellent electrical insulation characteristics and heat resistance characteristics of ceramics, but have the disadvantage of being expensive. On the other hand, the metal base circuit board has an intermediate character between them and is used for general purposes with relatively large electric power, such as a power source for refrigerators, a power source for air conditioning for homes, a power source for automobiles, a power source for high-speed railways, etc. Suitable for use.

The metal base circuit board has a structure in which an insulating layer of a resin such as epoxy filled with an inorganic filler such as alumina is provided on a metal plate such as aluminum, iron, or copper, and a circuit is provided thereon. Yes.
However, the thermal conductivity of the cured resin composition used as the insulating layer is low, and the heat dissipation characteristics as a circuit board are insufficient, resulting in malfunction of the semiconductor element. In some cases, long-term electrical reliability deteriorated.
Therefore, improvement of the thermal conductivity of the cured product of the resin composition for circuit boards is a very important examination item.

Generally, in order to improve the thermal conductivity of the cured body of the resin composition, the content of an inorganic filler having a high thermal conductivity is increased.
However, when the content of the inorganic filler is increased, the viscosity of the resin composition before curing increases, and the application work on the metal plate becomes difficult. In addition, an inorganic filler having a high thermal conductivity is not always good in filling properties.

Accordingly, there is provided a resin composition for a circuit board, which comprises an epoxy resin, an inorganic filler, a curing agent for curing the epoxy resin, and a dispersant for improving the dispersibility of the inorganic filler as essential components. (Patent Document 1).
However, this method has problems such as defects remaining in the cured product and a high screening failure rate.

Japanese Patent No. 3751271

As a result of various experimental studies in view of the above circumstances, the present inventor added an additive having a lower surface tension than the coating liquid in the coating liquid to be an insulating layer, and made the surface state uniform. As a result of reducing voids in the coating liquid and reducing defects while highly filling the inorganic filler, the withstand voltage characteristics of the cured product of the resin composition are uniform, and a metal having a low defect rate that has not been obtained in the past It has been found that a base circuit board can be obtained, and the present invention has been achieved.

That is, the present invention provides (1) a circuit board resin composition containing a thermosetting resin, an inorganic filler, and a smoothing agent, wherein the smoothing agent is a polyether-modified silicone. Resin composition for use, (2) containing 0.05 to 2.0% by mass of the smoothing agent and 45 to 95% by mass of the inorganic filler having a maximum particle size of 30 to 120 μm. Circuit board resin composition,
(3) The polyether-modified silicone has a molecular structure in which a phosphoric acid group, a dimethylpolysiloxane skeleton, and a polymer skeleton of polyethylene glycol and polypropylene glycol are all contained in one molecule, and the number average molecular weight is 27,000 or more and less than 33,000. (1) or (2) a circuit board resin composition, which is a polymer compound having a mass average molecular weight of 21,000 or more and less than 27000, (4) and one or two selected from polyisoprene and polybutadiene (1), (2) or (3) circuit board resin composition containing seeds, (5) (1), (2), (3) or (4) circuit board resin composition Metal base circuit board formed by applying an object to a substrate, (6) When a resin composition for a circuit board is applied to a substrate with a thickness of 30 to 150 μm, there is no defect having a diameter of 10 μm or more (5) A metal base circuit board.

  According to the present invention, there is an effect that a metal base circuit board having a low defect rate, which has not been obtained in the past, is obtained because the withstand voltage characteristics of the cured product of the resin composition for circuit boards is uniform.

FIG. 1 shows an example of a defect having a diameter of 10 μm or more in a cured body of a resin composition produced when a resin composition for a circuit board is applied to a substrate with a thickness of 30 to 150 μm.

Examples of the thermosetting resin used in the present invention include epoxy resins, unsaturated polyester resins, melamine resins, urea resins, diallyl phthalate resins, bismaleimide resins, triazine resins, polyurethane resins, phenol resins, cyanoacrylate resins, polyisocyanates. Examples include resins, furan resins, resorcinol resins, xylene resins, benzoguanamine resins, silicone resins, siloxane-modified epoxy resins, and siloxane-modified polyamideimide resins. These can be used alone or in admixture of two or more.
Moreover, it is preferable to contain an epoxy resin as (B) component from a viewpoint of improving heat resistance and adhesiveness.

The epoxy resin is not particularly limited as long as it is cured and has an adhesive action, and generally known epoxy resins can be used.
Specifically, for example, bifunctional epoxy resins such as bisphenol A type epoxy, novolac type epoxy resins such as phenol novolac type epoxy resin and cresol novolac type epoxy resin, and trisphenolmethane type epoxy resin can be used. Moreover, it is a polyfunctional epoxy resin, a glycidylamine type epoxy resin, a heterocyclic ring-containing epoxy resin, an alicyclic epoxy resin, or the like.

The epoxy resin can be cured by reacting with a curing agent or a catalytic curing agent. Examples of the catalyst-type curing agent include a tertiary amine, a simple substance or a mixture of imidazoles. As the curing agent, one or more selected from the group consisting of phenolic resins, acid anhydride resins, aromatic amine resins, and dicyandiamino can be used. Among these, aromatic amines are preferable in terms of peel strength and withstand voltage when the substrate is produced.
The addition amount of the curing agent to the epoxy resin is preferably blended so that the active hydrogen equivalent (or acid anhydride equivalent) of the curing agent is 0.01 to 1.25 with respect to the epoxy equivalent 1 of the epoxy resin. .

  By reacting the epoxy resin with a curing accelerator, an epoxy group self-polymerization reaction, an addition reaction between an epoxy group and an active hydrogen compound, and a copolycondensation reaction between an epoxy group and an acid anhydride can be promoted. Examples of the curing accelerator include tertiary amines, imidazoles, boron salts of onium compounds, organophosphate compounds, quaternary ammonium simple substances or mixtures.

The thermosetting resin used in the present invention is an inorganic surface modifier such as a silane coupling agent, a titanate coupling agent, and an aluminate coupling agent, if necessary, together with an inorganic filler. Further, a smoothing agent, an antifoaming agent, a wetting agent, a stabilizer, a curing accelerator and the like are added and used.

The polyether-modified silicone used as the leveling agent of the present invention has a molecular structure in which a phosphoric acid group, a dimethylpolysiloxane skeleton, and a polymer skeleton of polyethylene glycol and polyprene glycol are all contained in one molecule, and the number average molecular weight is It is a polymer compound having a molecular weight of 27,000 or more and less than 33,000 and a mass average molecular weight of 21,000 or more and less than 27,000.

As the polyether-modified silicone, for example, one having a structure represented by the following chemical formula 1 is known. However, in the formula, m is an integer of 100 to 350, n is an integer of 1000 to 3000, and o is an integer of 50 to 250.

In the present invention, the blending ratio of the polyether-modified silicone and the inorganic filler varies slightly depending on the amount of the thermosetting resin and the inorganic filler to be added, but the amount of the polyether-modified silicone is 100 parts by mass in total of both. The amount is preferably 0.05 to 2.0 parts by mass. If the amount is less than 0.05 parts by mass, the effect as a smoothing agent is small. If the amount exceeds 2.0 parts by mass, the peel strength tends to decrease when a metal base circuit board is produced.

By using polyether-modified silicone, the surface tension of the coating liquid consisting of inorganic filler and thermosetting resin is reduced, so that the surface condition is maintained even when the viscosity of the coating liquid increases in the coating liquid drying process. And film defects are reduced. In addition, you may dilute with a solvent etc. in order to reduce the viscosity of a coating liquid.

The inorganic filler used in the present invention preferably has a maximum particle size of the constituent particles in the range of 20 to 120 μm. It is known that when particles larger than 120 μm are present, the film thickness is close to that due to poor withstand voltage.
Examples of the inorganic filler include oxides such as silica and alumina, and non-oxides such as aluminum nitride, boron nitride, and silicon nitride. In the case of using a non-oxide, a material subjected to a surface treatment such as an oxidation treatment, a phosphoric acid treatment, and a surface coating with silica or the like may be used.

The inorganic filler in the circuit board resin composition of the present invention preferably contains 45 to 150 parts by mass with respect to 100 parts by mass of the thermosetting resin, and the metal base circuit board having high heat dissipation is insulated. It can be obtained without lowering the withstand voltage and peel strength. If it is less than 45 parts by mass, sufficient heat dissipation cannot be obtained, and if it exceeds 150 parts by mass, the filling property when filling the resin is poor, and the electrical reliability of the metal base circuit board becomes poor.

The metal base circuit board of the present invention has the characteristics that the insulating layer has high thermal conductivity, excellent adhesion between the metal plate and the circuit, and excellent withstand voltage characteristics.
Specifically, the metal base circuit board according to the present invention has a thermal conductivity of 7.0 W / mK or more, and in a preferred embodiment of the present invention, it reaches 8.0 W / mK or more. It is preferably used as a circuit board for various large current applications including circuit boards for mounting on automobiles.

As the metal plate used for the metal base circuit board of the present invention, aluminum, aluminum alloy, copper, copper alloy, iron, stainless steel and the like can be used.
Although there is no restriction | limiting in particular as thickness of a metal plate, 0.5-3.0 mm is generally used.

The material of the circuit of the present invention may be any material as long as it is conductive. Usually, a material made of copper, aluminum, nickel, or a composite layer thereof is used.

In the method for producing a metal base circuit board of the present invention, a resin composition is applied on a metal plate and cured or semi-cured to form an insulating layer. At this time, the insulating layer is a single layer or a plurality of layers. Thereafter, a method of joining a metal foil to be a circuit such as copper, aluminum or copper-aluminum composite foil using a roll laminating method or a lamination press method, or applying the resin composition to a metal foil that has been previously formed with a circuit, Although the method of hardening or semi-hardening and sticking on a metal plate etc. is mentioned, the former method is preferably employ | adopted when productivity is considered. In this method, a conventionally known method may be applied for etching the metal foil.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to this.

<Example 1>
Bisphenol A type liquid epoxy resin (manufactured by DIC, “EPICLON 850CRP”) 11 mass%, aromatic amine (manufactured by Nippon Synthetic Chemical Industry, “H-48B”) 4 mass%, aluminum nitride “1” (manufactured by Denka) , Average particle diameter 16 μm, maximum particle diameter 70 μm) 85 mass%, silane coupling agent (manufactured by Dow Corning Toray, “z-6040”) 1.0 mass part (mixture 100 of the epoxy resin, amine and aluminum nitride 100 To the parts by mass). Further, 0.3 parts by mass of polyether-modified polydimethylsiloxane (BYK, “BYK-302”) and 0.2 parts by mass of a dispersant (BYK, “DISPERBYK-110”) were added, and a planetary stirrer was added. (Sinky Co., Ltd. “Awatori Netaro AR-250”, rotation speed: 2000 rpm) to prepare a resin composition for a circuit board. (Table 1-1)

On a 2.0 mm thick aluminum plate (“A1050 2.0 mm thickness” manufactured by Amano Aluminum Co., Ltd.), the circuit board resin composition was applied so that the thickness of the insulating layer after curing was 100 μm. It dried at 15 degreeC for 15 minute (s), and was set as the B stage state.

Thereafter, a 35 μm thick copper foil (Mitsui Metals Co., Ltd., “electrolytic copper foil 35 μm thickness”) is placed on the insulating layer, and the resin composition for circuit boards is placed at 180 ° C. while being laminated by a hot press method A metal base substrate was obtained by curing by heat treatment for 2 hours.

About a metal base substrate, a desired position is masked with an etching resist, and a copper foil is etched using a sulfuric acid-hydrogen peroxide mixed solution as an etching solution. Then, the etching resist is removed and washed and dried to form a circuit. A metal-based circuit board was obtained.

The inorganic filler used in Example 1, the obtained resin composition for circuit boards, and the metal base substrate were evaluated by the following methods.
[Average particle size and maximum particle size of inorganic filler]
The measurement was performed using a “laser diffraction particle size distribution analyzer SALD-200” manufactured by Shimadzu Corporation. As a sample, 5 g of 50 cc pure water and an inorganic filler were added to a glass beaker, stirred using a spatula, and then subjected to dispersion treatment for 10 minutes using an ultrasonic cleaner. The dispersion product of the inorganic filler that had been subjected to the dispersion treatment was added dropwise to the sampler portion of the apparatus with a dropper and waited until the absorbance became measurable. Measurements were taken when the absorbance was stable. In the laser diffraction particle size distribution analyzer, the particle size distribution is calculated from the data of the light intensity distribution of the diffracted / scattered light by the particles detected by the sensor. The average particle size was d50 and the maximum particle size was d90.

[Thermal conductivity of cured resin composition for circuit board]
A cured product of the circuit board resin composition was prepared and calculated from the thermal diffusivity, specific gravity, and specific heat. The thermal diffusivity was determined by a laser flash method after processing the sample into a width of 10 mm × 10 mm × thickness of 1 mm. The measuring device used was a xenon flash analyzer (LFA447 NanoFlash manufactured by NETZSCH). Specific gravity was determined using the Archimedes method. The specific heat was obtained by using a differential scanning calorimeter (“Q Instruments”, “Q2000”) and raising the temperature from room temperature to 400 ° C. at a heating rate of 10 ° C./min in a nitrogen atmosphere. (Table 3-1)

[Defects in coating film after curing of resin composition for circuit board]
On a 2.0 mm thick aluminum plate, the resin composition for a circuit board was applied so that the thickness of the insulating layer after curing was 100 μm, and dried at 100 ° C. for 15 minutes to obtain a B stage state. 1 mm × 1 mm Was observed with an actual microscope (Nikon MM-800), and the number of defects of 10 μm or more as shown in FIG. 1 was measured. The measurement was repeated 20 times at different places, and the arithmetic average value was defined as the number of defects. (Table 3-1)

[Metal base circuit board withstand voltage failure rate]
Using a resin composition for circuit boards, a 35 μm thick copper foil and a 2.0 mm thick Al plate were bonded to obtain a metal base substrate. Furthermore, what produced the circular electrode of diameter 50mm by etching copper foil was made into the measurement sample. In 500 measurement samples, a voltage of DC 3.6 kV was applied between the copper plate and the copper foil for 1 second, and the defect rate was calculated from the number of dielectric breakdowns. (Table 3-1)

[Peel strength of metal base substrate]
Using a resin composition for circuit boards, a 35 μm thick copper foil and a 2.0 mm thick Al plate were bonded to obtain a metal base substrate. The bonded copper foil was cut into a size of 10 mm × 100 mm, and the peel strength between the copper foil and the circuit board resin composition was measured under the conditions of 23 ± 2 ° C. and 50% relative humidity in accordance with the method defined in JIS C 6481. The measurement was repeated 5 times, and the arithmetic average value was defined as the peel strength. (Table 3-1)

[Rate of defective withstand voltage after pressure cooker test of metal base substrate]
Using a resin composition for circuit boards, a 35 μm thick copper foil and a 2.0 mm thick Al plate were bonded to obtain a metal base substrate. Further, a copper electrode was etched to produce a circular electrode having a diameter of 50 mm, and after a pressure cooker test (continuous treatment for 96 hours under the conditions of 2 atm, 100% humidity and 121 ° C.), it was dried to obtain a measurement sample. In 500 measurement samples, a voltage of DC 3.6 kV was applied between the copper plate and the copper foil for 1 second, and the defect rate was calculated from the number of dielectric breakdowns. (Table 3-1)

<Example 2>
The same procedure as in Example 1 was performed except that the amount of polyether-modified polydimethylsiloxane added in Example 1 was changed to 0.04 parts by mass. (Table 1-1, Table 3-1)

<Example 3>
The same procedure as in Example 1 was performed except that the amount of the polyether-modified polydimethylsiloxane added in Example 1 was changed to 0.06 parts by mass. (Table 1-1, Table 3-1)

<Example 4>
The same procedure as in Example 1 was conducted except that the amount of the polyether-modified polydimethylsiloxane added in Example 1 was changed to 1.9 parts by mass. (Table 1-1, Table 3-1)

<Example 5>
The same operation as in Example 1 was performed except that the amount of the polyether-modified polydimethylsiloxane added in Example 1 was changed to 2.1 parts by mass. (Table 1-1, Table 3-1)

<Examples 6 to 11>
The same procedure as in Example 1 was performed except that the types and blending amounts of bisphenol A type liquid epoxy resin, aromatic amine and inorganic filler were changed as shown in Table 1.
The inorganic fillers are aluminum nitride “2” (Denka, average particle size 65 μm, maximum particle size 113 μm), aluminum nitride “3” (Denka, average particle size 70 μm, maximum particle size 125 μm), aluminum nitride “ 4 ”(manufactured by Denka, average particle diameter 11 μm, maximum particle diameter 27 μm), aluminum nitride“ 5 ”(manufactured by Denka, average particle diameter 4.5 μm, maximum particle diameter 12 μm), boron nitride (manufactured by Denka, average particle A silicon nitride (manufactured by Denka Corporation, average particle diameter of 18 μm, maximum particle diameter of 85 μm), and alumina (manufactured by Denka Corporation, average particle diameter of 2 μm, maximum particle diameter of 5 μm) were used. (Table 1-1, Table 1-2, Table 3-1, Table 3-2)

<Example 12>
The same procedure as in Example 1 was conducted except that 0.3 parts by mass of polyisoprene (manufactured by Kraton, Ziegler IR) was added in addition to the polyether-modified polydimethylsiloxane in Example 1. (Table 1-2, Table 3-2)

<Example 13>
In addition to the polyether-modified polydimethylsiloxane in Example 1, the same procedure as in Example 1 was performed except that 0.3 parts by mass of polybutadiene (UBEPOLBR-150, manufactured by Ube Industries) was added. (Table 1-2, Table 3-2)

<Example 14>
In addition to polyether-modified polydimethylsiloxane in Example 1, 0.2 parts by mass of polyisoprene (manufactured by Kraton, Ziegler IR) and 0.2 parts by mass of polybutadiene (manufactured by Ube Industries, UBEPOLBR-150) were added. Except for this, the same procedure as in Example 1 was performed. (Table 1-2, Table 3-2)

<Example 15>
The same procedure as in Example 1 was performed except that a mixture of bismaleimide resin and cyanate resin ("BT2160" manufactured by Mitsubishi Gas Chemical Company) was used in Example 1 instead of bisphenol A liquid epoxy resin and aromatic amine. It was. (Table 1-2, Table 3-2)

<Example 16>
The same procedure as in Example 14 was performed except that a mixture of bismaleimide resin and cyanate resin ("BT2160" manufactured by Mitsubishi Gas Chemical Company) was used instead of bisphenol A type liquid epoxy resin and aromatic amine in Example 14. . (Table 1-2, Table 3-2)

<Comparative Example 1>
The same procedure as in Example 1 was performed except that the polyether-modified polydimethylsiloxane was not added in Example 1. (Table 2, Table 4)

<Comparative example 2>
The same procedure as in Example 1 was performed except that an acrylic polymer (manufactured by Kyoeisha Chemical Co., “Polyflow No99C”) was used instead of the polyether-modified polydimethylsiloxane in Example 1. (Table 2, Table 4)

<Comparative Example 3>
Example 1 was performed in the same manner as in Example 1 except that a fluorine-based leveling agent (manufactured by DIC, “Megafac F-554”) was used instead of the polyether-modified polydimethylsiloxane. (Table 2, Table 4)

From the results of Tables 3-1, 3-2 and Table 4, it was found that the cured bodies using the circuit board resin compositions of the examples were excellent in thermal conductivity. Furthermore, it turned out that the metal base circuit board produced with the resin composition for circuit boards of an Example is excellent in a withstand voltage characteristic and peel strength.

The above results were the same for the hybrid integrated circuit in addition to the metal base circuit board used in the example.

The present invention provides a metal base circuit board having a low defect rate, which is uniform and has a withstand voltage characteristic of a cured product of a resin composition for a circuit board, which has not been obtained in the past. Used for circuit boards on which electrical components are mounted.

1 Defects with a diameter of 10 μm or more

Claims (6)

A resin composition for circuit boards, comprising a thermosetting resin, an inorganic filler, and a smoothing agent, wherein the smoothing agent is polyether-modified silicone. The resin composition for a circuit board according to claim 1, comprising from 0.05 to 2.0 mass% of the smoothing agent and from 45 to 95 mass% of the inorganic filler having a maximum particle size of 30 to 120 µm. The polyether-modified silicone has a molecular structure that includes all of a phosphate group, a dimethylpolysiloxane skeleton, a polymer skeleton of polyethylene glycol and polypropylene glycol in one molecule, and has a number average molecular weight of 27,000 or more and less than 33,000, The resin composition for circuit boards according to claim 1 or 2, wherein the polymer compound has an average molecular weight of 21,000 or more and less than 27000. Furthermore, the resin composition for circuit boards of Claim 1, Claim 2, or Claim 3 formed by containing 1 type or 2 types chosen from polyisoprene and polybutadiene. A metal base circuit board obtained by coating the circuit board resin composition according to claim 1, 2, 3, or 4 on a board. The metal base circuit board according to claim 5, wherein when the resin composition for a circuit board is applied to the substrate with a thickness of 30 to 150 μm, there is no defect having a diameter of 10 μm or more.