JP2002076549A - Metal base circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal base circuit board having excellent stress relaxedness, heat radiation properties, good heat resistance, moisture resistance and insulation reliability. SOLUTION: The metal base circuit board is obtained by laminating a conductive metal foil on a metal plate via an insulation adhesive layer. In this case, the adhesive layer contains a resin containing an epoxy resin as a main body, a curing agent compound, silicone rubber particles and an inorganic filler. The silicone rubber particles having an electrical conductivity of distilled water of 200 μS/cm or less are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal-based circuit board which is excellent in stress relaxation, insulation reliability and heat dissipation.

[0002]

2. Description of the Related Art Conventionally, a metal base circuit board having an insulating layer made of an epoxy resin or the like filled with an inorganic filler on a metal plate and having a conductive circuit disposed thereon has excellent heat dissipation. It is used as a circuit board on which high heat-generating electronic components are mounted.

[0003] On the other hand, there is a demand for mounting and disposing electronic equipment in an engine room together with the downsizing and space saving of the on-vehicle electronic equipment. The inside of the engine room has a severe environment such as a high temperature and a large temperature change, and a substrate having a large heat radiation area is required. For such applications, attention has been paid to the metal-based circuit boards having excellent heat dissipation.

A conventional metal-based circuit board often uses an aluminum plate for heat dissipation and economical reasons. However, if heating / cooling is repeated in actual use, the aluminum plate and the electronic components, In particular, there is a problem that a large thermal stress is generated due to a difference in a coefficient of thermal expansion from a chip component, and cracks are generated in a solder portion fixing the component or in the vicinity thereof, thereby lowering electrical reliability. . In order to improve such a point, the insulating adhesive layer has high thermal conductivity,
It is necessary to have a low elastic modulus and a high level of heat resistance and moisture resistance. For such a purpose, for example, Japanese Patent Application Laid-Open No. Hei 10-242606 discloses a composition in which the elastic modulus is reduced by using a reactive acrylic rubber, but the moisture resistance is not yet sufficient.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is unlikely to cause cracks or other abnormalities in the solder or in the vicinity thereof even if the temperature is repeatedly increased / decreased. It is an object of the present invention to provide a metal-based circuit board having excellent heat resistance, moisture resistance and heat dissipation.

[0006]

According to the present invention, there is provided a metal base circuit board in which a conductive metal foil is adhered to at least one principal surface of a metal plate via an insulating adhesive layer. A metal-based circuit board comprising a resin mainly composed of an epoxy resin, a curing agent compound, rubber particles, and an inorganic filler, wherein the electrical conductivity of the boiling extraction water of the rubber particles is 200 μS / cm or less. . The rubber particles are preferably epoxy-modified, and the average particle diameter is preferably 5 to 20 μm. When the rubber particles are silicone rubber particles, the unreacted polysiloxane in the particles is purified. Is preferred. Further, the storage elastic modulus of the insulating adhesive layer of the metal-based circuit board of the present invention is 30.
It is preferably 15000 MPa or less at 0K.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The insulating adhesive layer used in the present invention is made of a combination of a resin mainly composed of an epoxy resin, a curing agent compound, rubber particles and an inorganic filler to provide stress relaxation, electric insulation and heat dissipation. A cured product having excellent heat resistance, heat resistance and moisture resistance can be provided. As the epoxy resin, a bisphenol F epoxy resin, a bisphenol A epoxy resin, a phenol novolak epoxy resin, a cresol novolak epoxy resin, or the like is used. From the viewpoint of moisture resistance, it is preferable to use a material containing few ionic impurities such as sodium and chlorine. In addition, epoxy resin as the main resin, thermosetting resin such as phenolic resin and polyimide resin and high molecular weight resin such as phenoxy resin, considering the balance of stress relaxation, electrical insulation, heat resistance and moisture resistance Then, the compounding amount of the other resin is preferably 30% by mass or less based on the total amount with the epoxy resin.

The curing agent is not particularly limited.
From the viewpoint of moisture resistance, aromatic amines and phenol novolak resins are preferred. As the aromatic amine-based curing agent, diaminodiphenylmethane, diaminodiphenylsulfone, metaphenylenediamine and the like can be used.

As the rubber particles, particles such as silicone rubber, NBR and acrylic rubber are used. From the viewpoint of stress relaxation, the Tg of the rubber is preferably 0 ° C. or lower. Among them, silicone rubber is preferred because it has the lowest Tg and has a large effect of lowering the storage elastic modulus in a low temperature region and is excellent in heat resistance and moisture resistance. A general method for producing rubber particles is obtained by emulsifying and dispersing a raw material monomer or oligomer in an aqueous surfactant solution, heating and polymerizing or reacting in the presence of a catalyst, and finally by spray drying. Examples of the production method for silicone rubber include, for example, an organopolysiloxane having at least two silicon-bonded hydroxyl groups in one molecule and an organohydrogenpolysiloxane having at least two silicon-bonded hydrogens in one molecule. It is obtained by performing a dehydrogenation reaction in the presence of a platinum or tin-based curing catalyst. The particulate silicone rubber is obtained by dispersing the above uncured liquid composition in water using a surfactant, spraying the dispersion in a high-temperature gas, and curing and drying. Surfactant remains on the surface of the rubber particles obtained by the above method,
If necessary, the surface is washed and the electrical conductivity of the boiling extraction water is set to 200 μS / cm or less, whereby the moisture-resistant insulation is improved. It is preferable that the rubber particles have their surfaces modified with epoxy, because the adhesion between the insulating layer and the conductive metal foil is excellent. In the case of silicone rubber, in the case of silicone rubber, a part of the organopolysiloxane having at least two silicon-bonded hydroxy groups is replaced with a silane compound having an epoxy group such as γ-glycidoxypropyltrimethoxysilane. In the case of NBR or acrylic rubber, it is obtained by copolymerizing a monomer having an epoxy group such as glycidyl methacrylate. The particle size of the rubber particles can be adjusted by the type and amount of the surfactant, spraying conditions, etc., but when the average particle size is 5 to 20 μm, the adhesiveness between the insulating adhesive layer and the conductive metal foil can be improved. Excellent. In the case of silicone rubber particles, 2 to 4% by mass of unreacted polysiloxane usually remains after the reaction, and the silicone rubber particles are washed with an organic solvent dissolving polysiloxane such as toluene to remove unreacted polysiloxane inside the particles. The reactive polysiloxane can also be easily purified, and the adhesion between the insulating adhesive layer and the conductive metal foil is improved. Further, since a normal surfactant is soluble in an organic solvent such as toluene, the surfactant remaining on the surface can be washed at the same time, so that the moisture-proof insulation can be improved.

As the inorganic filler, those having good electric insulation and high thermal conductivity are used, such as aluminum oxide, aluminum nitride, silicon nitride, boron nitride and silica. A mixed system can also be used. Among them, aluminum oxide having a spherical particle shape and being highly packable is preferable because it is inexpensive and easily available. The inorganic filler can be surface-treated in advance with a silane coupling agent such as epoxy silane or amino silane, or by blending the silane coupling agent in the insulating adhesive, the adhesion to the conductive metal foil can be improved. .

The storage elastic modulus of the insulating adhesive layer of the present invention after curing is preferably 15000 MPa or less at 300K. If it is 15000 MPa or more, the stress relaxation property is poor.
If the storage elastic modulus is too low, it may be deformed when an external force is applied and insulation reliability may be impaired.
It is preferably at least 00 MPa.

The thickness of the insulating adhesive layer is determined in consideration of stress relaxation, heat dissipation, insulation reliability, productivity, etc., and is usually about 50 to 150 μm.

As the conductive metal foil serving as a conductor circuit,
Any of copper, aluminum, nickel, iron, tin, silver, and titanium, an alloy containing two or more of these metals, a clad foil using the metal or the alloy, or the like can be used. The foil may be manufactured by an electrolytic method or a rolling method.
Although metal plating such as Au plating or solder plating may be applied, the surface of the conductor circuit in contact with the insulating adhesive layer is roughened in advance by etching, plating, etc. from the viewpoint of adhesiveness with the insulating adhesive layer. It is more preferred that

The metal plate used in the present invention is made of aluminum, iron, copper and their alloys, or their clad materials, and the thickness thereof is not particularly limited, but is rich in heat dissipation and economical. Therefore, aluminum having a thickness of 0.5 to 5.0 mm is generally selected.

In the method for producing a metal-based circuit board according to the present invention, an insulating material obtained by appropriately adding an additive such as a dispersant, an antifoaming agent or a leveling agent to a curable resin composition is formed on a metal plate and / or a metal. Applying on a foil, laminating a metal foil or a metal plate and then curing it sufficiently, then forming a circuit from the metal foil, or preparing a sheet made of an insulating material in advance, It can be obtained by a conventionally known method such as a method of bonding a plate and a metal foil to form a circuit, or a method of directly using a conductor circuit formed in advance of a circuit instead of the metal foil in the above method.

Hereinafter, the present invention will be described in more detail with reference to Examples. Unless otherwise specified, parts and% represent parts by mass and% by mass, respectively.

[0017]

EXAMPLES (Production of Silicone Rubber Particles) [Production Example 1] 100 parts of dimethylpolysiloxane (having a hydroxyl group content of 1.3%) having a viscosity of 80 mPa · sec and both ends of a molecular chain blocked with a hydroxyl group, and a viscosity of 10 mPa · sec.
A mixture of 10 parts of methyl hydrogen polysiloxane (1.5% silicon-bonded hydrogen atom content) having both ends dimethylhydrogensiloxy group-blocked and 0.5 part of dibutyltin dilaurate is immediately mixed with a static mixer. Mix evenly. Next, this was transferred to a colloid mill, and at the same time, 5 parts of a 20% aqueous solution of sodium dodecylbenzenesulfonate and 600 parts of ion-exchanged water were added to add 1 part.
Milling was performed under the conditions of 400 rotations / minute and an interval of 0.1 mm to obtain an aqueous dispersion of the silicone composition. This dispersion was sprayed into the air at a temperature of 300 ° C. using a spray at a discharge rate of 3 L / Hr, and curing was completed in the spray state to obtain silicone rubber particles. The operation of dispersing and stirring 10 parts of the silicone rubber particles in 200 parts of ion-exchanged water and performing solid-liquid separation was repeated three times to wash and remove the surfactant on the surface. Finally, the wet cake was redispersed in ion-exchanged water using a colloid mill and spray-dried to obtain purified silicone rubber particles.

[Preparation Example 2] In Preparation Example 1, 95 dimethylpolysiloxane (having a hydroxyl group content of 1.3%) having a viscosity of 80 mPa · sec and having both molecular chain terminals blocked with hydroxyl groups was used.
, And epoxy-modified purified silicone rubber particles were obtained in the same manner as in Production Example 1 except that 5 parts of γ-glycidoxytrimethoxysilane were used.

[Production Example 3] The surfactant used in preparing the aqueous dispersion of the silicone composition in Production Example 1 was changed to 1 part of polyoxyethylene nonylphenyl ether (HLB15).
Silicone rubber particles were obtained in the same manner as in Production Example 1 except that the purification operation was not performed.

[Preparation Example 4] The surfactant used in preparing a water dispersion of the silicone composition in Preparation Example 2 was changed to 1 part of polyoxyethylene nonylphenyl ether (HLB15). Purification is performed by adding toluene 20 to 10 parts of silicone rubber.
Add 0 parts, stir at room temperature for 60 minutes, and perform filtration 3 times.
Repeated times. The third filtrate was concentrated by an evaporator, and it was confirmed that there was no more extract. Thereafter, the wet cake was dried with hot air at 80 ° C. for 1 hour while being crushed to obtain silicone rubber particles in which both the surfactant and the unreacted polysiloxane were purified.

[Production Example 5] Silicone rubber particles were obtained in the same manner as in Production Example 1 except that the number of times of washing with ion-exchanged water was one in Production Example 1.

(Production of Metal-Based Circuit Board) Example 1 100 parts of bisphenol F type epoxy resin (Epicoat 807, manufactured by Yuka Shell Epoxy Co., Ltd.) as an epoxy resin, and purified silicone rubber particles 60 produced in Production Example 1 Part, γ-glycidoxypropylmethyldiethoxysilane (AZ-6) as a silane coupling agent
165: 5 parts of Nippon Unicar Co., Ltd.) and 500 parts of alumina (AS-50: Showa Denko KK) having an average particle size of 5 μm as an inorganic filler were mixed with a universal mixing stirrer.
The mixture was further kneaded with three rolls. To this, 27 parts of diaminodiphenylmethane was added as a curing agent to prepare an insulating adhesive. The above mixture was applied on a 2.0 mm-thick aluminum plate so that the thickness of the insulating adhesive layer after curing became 100 μm, and was preliminarily cured in a B-stage state, and a 70 μm-thick electrolytic copper foil was laminated with a laminator, Then 80
C. × 2 hrs + 150 ° C. × 3 hrs after-curing to prepare a copper foil substrate with an insulating adhesive layer, and further, etching the copper foil to form a desired circuit having a pad portion, thereby obtaining a metal base circuit substrate. Further, the resin composition is
C. × 2 hrs + 150 ° C. × 3 hrs, a test piece of a cured body having a thickness of about 100 μm, a width of about 3 mm, and a length of about 50 mm was separately prepared and subjected to measurement of storage modulus.

[Examples 2 to 4] Metal-based circuit boards were prepared in the same manner as in Example 1 except that the silicone rubber particles were changed to those of Production Examples 2 to 4, respectively.

Comparative Example 1 A metal-based circuit board was prepared in the same manner as in Example 1, except that the silicone rubber in Example 1 was changed to that of Production Example 5.

Comparative Example 2 A metal-based circuit board was prepared in the same manner as in Example 1 except that the silicone rubber particles were removed.

(Evaluation of Characteristics of Silicone Rubber) Production Example 1
With regard to the characteristics of the silicone rubber particles produced in Example 5, the electrical conductivity and the average particle size were evaluated. The results are shown in Table 1. The electric conductivity was measured by dispersing 10 g of silicone rubber particles in 40 g of distilled water (electric conductivity of distilled water: 1 to 2 μS / cm), stirring for 30 minutes while boiling, cooling, and measuring the electric conductivity of the extracted water. did. The average particle diameter was determined from the result of observing a cross section of a cured body test piece for measuring storage elastic modulus with a scanning electron microscope.

(Measurement of Storage Elastic Modulus) For each of the above cured products, a dynamic viscoelasticity meter (RSA2 manufactured by Rheometrics Co., Ltd.) was used at a frequency of 11 Hz and a heating rate of 1
The storage modulus was measured in the temperature range of -50 ° C to + 150 ° C under the condition of 0 ° C / min. Table 1 shows the results of storage modulus measurement at 300K.

(Evaluation of Characteristics of Metal Substrate) Copper foil peel strength, withstand voltage and insulation resistance (surface resistance) of a metal base substrate and a heat cycle test of a metal base circuit substrate were measured under the following conditions. The measurement results are also shown in Table 1.

<Measurement of Peel Strength of Copper Foil> The metal base substrate one week after the production was measured using a Tensilon (manufactured by Orientec; model UCT-1T) with a width of 1 cm and a width of 9 cm.
The strength when peeled at a rate of 50 mm / min at room temperature in the direction of 0 ° was determined.

<Measurement of Withstanding Voltage> Test pieces after and before treatment in a pressure cooker tester at a temperature of 121 ° C., a relative humidity of 100% and a pressure of 2026 hPa for 96 hours and before the treatment were immersed in insulating oil. An AC voltage was applied between the plates, and the voltage at which dielectric breakdown occurred was measured. The initial applied voltage is 0.5 kV. After holding at each voltage for 30 seconds,
A voltage was applied by a method of stepwise increasing the voltage by 0.5 kV.

<Heat Cycle Test Method> A chip resistor having a chip size of 2.0 mm × 1.25 mm was soldered between pads, and 500 cycles of heat cycle were performed at -40 ° C. for 7 minutes to + 125 ° C. for 7 minutes. After the test, the presence or absence of cracks in the solder portion was observed with a microscope. If the occurrence of cracks in the solder portion was 10% or more, it was determined to be defective, and if the occurrence of solder cracks was less than 10%, it was determined to be good.

[0032]

[Table 1]

[0033]

According to the present invention, it is possible to provide a metal-based circuit board which is excellent in heat dissipation, chip component mounting reliability, and also excellent in moisture resistance, heat resistance and insulation reliability.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5E315 AA03 BB01 BB02 BB03 BB04 BB09 BB14 BB15 BB18 GG01 GG03 GG05 GG09

Claims (5)

[Claims] 1. A metal base circuit board in which a conductive metal foil is bonded to at least one main surface of a metal plate via an insulating adhesive layer, wherein the insulating adhesive layer is made of a resin mainly composed of an epoxy resin and a curing agent. A compound, rubber particles and an inorganic filler, wherein the electrical conductivity of the boiling extraction water of the rubber particles is 200
A metal-based circuit board having a μS / cm or less. 2. The metal-based circuit board according to claim 1, wherein the rubber particles are epoxy-modified. 3. The metal-based circuit board according to claim 1, wherein the rubber particles have an average particle size of 5 to 20 μm. 4. The rubber particles are silicone rubber particles,
4. The metal-based circuit board according to claim 1, wherein unreacted polysiloxane in said particles is purified. 5. The storage elastic modulus of the insulating adhesive layer is 15 at 300K.
4,000 MPa or less.
A metal-based circuit board as described.