JPH118450A - Metal base circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a metal plate in its adhesion to a conductive circuit and to enhance a metal base circuit board in stress relaxation properties and heat- dissipating properties by a method, wherein an insulating layer is composed of, at least, two or more layers formed of two or more kinds of resin composition, and one of the layers is set lower in elastic modulus than a specific value at a specified temperature. SOLUTION: An insulating layer 2 is formed on a metal plate 1, and a conductor circuit 6 is provided onto the insulating layer 2. The insulating layer 2 is composed of two resin composition layers 3 and 4. It is preferable that the resin composition layers 3 and 4 contain various inorganic fillers, and the insulating layer 2 be formed of at least two or more kinds of resin compositions composed of various resins, various inorganic fillers, and various additive agents which are changed in the mixing ratio. At least, one of the resin composition layers has an elastic modulus of 2×10<10> Pa or less at a temperature of -40 deg.C. When one or more of the resin composition layers whose elastic modulus is 2×10<10> Pa or less at a temperature of -40 deg.C are present, the insulation layer 2 is capable of attaining the objective.

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 excellent in stress relaxation 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 electronic equipment to be mounted in an engine room as well as to reduce the size and space of electronic equipment for vehicles. The engine room is in a harsh environment such as high temperatures and large temperature changes.
Further, a substrate having a large heat dissipation 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 electronic components and In particular, there is a problem that a large thermal stress is generated due to a difference in the coefficient of thermal expansion from the chip component, and cracks are generated in a solder portion fixing the component or in the vicinity thereof, thereby deteriorating electrical reliability. .

Further, by using a material having a low elastic modulus for the insulating layer, stress generated between the metal plate and the electronic component can be reduced. However, as the size of the chip component increases, the modulus of elasticity of the material needs to be greatly reduced.However, a material having a low modulus of elasticity generally has low adhesion to aluminum or copper of a circuit conductor. There is a problem that a metal base circuit board having excellent adhesion between the metal base plate and the metal plate cannot be obtained. In particular, since the adhesion of the conductive foil to the metal plate is significantly reduced at high temperatures, it is difficult to obtain a metal-based circuit board having excellent heat resistance.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and has excellent adhesion between a metal plate and a conductive circuit and excellent stress relaxation. It is an object of the present invention to provide a metal-based circuit board excellent in heat dissipation, which does not cause an abnormality such as crack generation in the solder or its vicinity even when received.

[0007]

SUMMARY OF THE INVENTION The present invention is a metal-based circuit board having a circuit laminated on a metal plate via an insulating layer having a multilayer structure, wherein the insulating layer has at least two layers.
And at least one of the resin composition layers has an elastic modulus at −40 ° C. of 2 × 10 ¹⁰ P
(a) or less, which is a metal-based circuit board.

[0008] The present invention also provides an elastic modulus at -40 ° C of 2 × 1.
The metal-based circuit board described above, wherein at least one or more other resin composition layers are interposed between the resin composition layer having a pressure of 0 ¹⁰ Pa or less and the circuit. Is a metal-based circuit board in which a resin composition layer having an elastic modulus at −40 ° C. of 2 × 10 ¹⁰ Pa or less is made of a cured epoxy resin.

In addition, the present invention is the above-mentioned metal-based circuit board, wherein the resin composition layer contains a rubber-based polymer having a glass transition temperature of 0 ° C. or less.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 and 2 show the metal base of the present invention.
FIG. 2 is a cross-sectional view of an example of a circuit board. An insulating layer is provided on a metal plate, and a conductor circuit is provided on the insulating layer. In the present invention, the insulating layer 2 has a multilayer structure.
In FIG. 1, the insulating layer 2 has two resin composition layers 3,
2, three resin composition layers 3 in FIG.
Although a multilayer structure composed of 4 and 5 is illustrated,
The present invention is not limited to this.

The resin composition layers 3, 4, and 5 of the present invention preferably contain various inorganic fillers in order to maintain high heat dissipation of the metal-based circuit board. , Types of inorganic fillers, types of additives to the resin, or at least two or more types of resin composition layers in which the quantitative ratios thereof are changed. For example, in FIG. 2, even if the resin composition layers 3, 4, and 5 have different compositions, the resin composition layers 3 and 5 have the same composition, and the resin composition layer 4 has the two resin compositions. The composition of the material layers 3 and 5 may be different.

In the present invention, it is essential that at least one of the plurality of resin composition layers has an elastic modulus at −40 ° C. of 2 × 10 ¹⁰ Pa or less. This is because the object of the present invention can be achieved when at least one resin composition layer having an elastic modulus at −40 ° C. of 2 × 10 ¹⁰ Pa or less exists.

The modulus of elasticity of a conventionally known resin composition is, for example, −40 ° C. when an epoxy resin is highly filled with an inorganic filler.
In this case, the pressure is about 3 × 10 ¹⁰ Pa, but the present inventors can fill the inorganic filler of the conventionally known resin composition at a high level,
As a result of an experimental study to lower the elastic modulus without deteriorating the characteristics of having a high withstand voltage characteristic and having a high thermal conductivity, as described later, 2 × 10 ¹⁰ even at −40 ° C.
The present inventors have found that a resin composition having an elastic modulus of Pa or less can be obtained, and the present invention has been found that a metal-based circuit board having excellent stress relaxation can be obtained using the resin composition having a low elastic modulus. It has been reached.

According to the study results of the present inventors, the thermal stress generated when the metal-based circuit board is subjected to a heating / cooling history under practical conditions is such that the elastic modulus at −40 ° C. is 2 × 10 ¹⁰ Pa or less. It has been found that the presence of at least one resin composition layer is relaxed, and that the position of the resin composition layer in the insulating layer does not need to be specified. Furthermore, the present inventors have found that between the resin composition layer and the circuit is -40 ℃ elastic modulus 2 × 10 ¹⁰ Pa or less, the other at least one or more layers,
That is, it has been found that when a resin composition layer having an elastic modulus at −40 ° C. of not more than 2 × 10 ¹⁰ Pa is interposed, the adhesive force between the conductor circuit and the metal plate is kept high even at a high temperature. It has been reached.

The elastic modulus at -40 ° C. of the present invention is 2 × 10 ¹⁰ P
As the resin used for the resin composition of a or less, any resin may be used as long as it is excellent in heat resistance and electrical insulation, but from the viewpoint of heat resistance and dimensional stability, thermosetting resin is used. Resins are preferred, and among the thermosetting resins, epoxy resins which are relatively low in viscosity at room temperature or under heating, are easy to handle, and are excellent in heat resistance, electrical insulation, adhesion and the like are preferred.
The epoxy resin may be a resin containing an epoxy resin as a main component and a phenol resin or a polyimide resin in combination.

In order to lower the modulus of elasticity, (1) a rubber such as butadiene rubber, acrylic rubber, silicon rubber or the like is dispersed in a normal epoxy resin, (2) urethane modification is performed, (3) glycidyl dimer acid Ester, polyglycol type epoxy resin, butyl ether-modified bisphenol
(4) using a flexible curing agent such as a modified polyamine type resin with a normal epoxy resin, or (5) using a combination thereof. Can be adopted.

In particular, in order to obtain a resin composition having a low elastic modulus in a low temperature range, it is preferable to disperse a rubber-based polymer having a glass transition temperature of 0 ° C. or less, and assume that the circuit board is used under extremely low temperatures. In this case, it is preferable to disperse those having a lower glass transition temperature. To disperse the rubber-based polymer, add the already gelled rubber particles to the epoxy resin and then cure the epoxy resin, or dissolve the liquid rubber in the epoxy resin and separate the phases when the epoxy resin cures. Various methods such as dispersing can be adopted.

The elastic modulus at -40 ° C. of the present invention is 2 × 10 ¹⁰ P
As the inorganic filler used in the resin composition having a or less, a material having good electric insulation and high thermal conductivity is used, and as such, silicon oxide, aluminum oxide, aluminum nitride, silicon nitride, There is boron nitride and the like, and a single system or a mixed system can be used. Among them, silicon oxide and aluminum oxide, which have a spherical particle shape and can be highly filled, can be easily obtained at low cost, and therefore, boron nitride is preferable because of its low dielectric constant.

The amount of the inorganic filler to be added is preferably 50 to 80% by volume in the resin composition. If it is less than 50%, the effect of heat radiation may be reduced and the application may be practically limited,
If it exceeds 80%, dispersion in the resin becomes difficult, and -4
This is because it becomes difficult to obtain a resin composition having a modulus of elasticity of 2 × 10 ¹⁰ Pa or less at 0 ° C., and it also causes a decrease in adhesion and a decrease in withstand voltage due to remaining voids.

In the present invention, the elastic modulus at −40 ° C. is 2 ×
The thickness of the resin composition layer of 10 ¹⁰ Pa or less is 10 to 10
A thickness of about 0 μm is sufficient, and a thickness of 20 to 80 μm is preferable because a metal-based circuit board can be manufactured with high productivity.

Types of resins used for resin compositions other than the resin composition having an elastic modulus at -40 ° C. of 2 × 10 ¹⁰ Pa or less, ie, a resin composition having an elastic modulus at −40 ° C. exceeding 2 × 10 ¹⁰ Pa As for the resin, any resin may be used as long as it is excellent in heat resistance and electrical insulation. However, the bending elastic modulus at −40 ° C. is 2 × 10 so that the resin composition layers are sufficiently bonded to each other. It is preferably the same type as the resin used for the resin composition having a pressure of ¹⁰ Pa or less.

The elastic modulus at -40 ° C. is 2 × 10 ¹⁰ Pa
Inorganic fillers used in resin compositions other than the following resin compositions also have good electrical insulation properties and high thermal conductivity, such as silicon oxide, aluminum oxide, aluminum nitride, silicon nitride, Boron nitride or the like can be used alone or in combination. When the adjacent resin composition layers have the same resin and inorganic filler, the difference in the amount of the inorganic filler added is about 3%, so that each of the resin composition layers is, for example, a scanning electron microscope. When used to observe their cross sections, they can be clearly distinguished.

The thickness of the resin composition layer other than the resin composition layer having an elastic modulus at −40 ° C. of 2 × 10 ¹⁰ Pa or less may be about 10 to 100 μm. Since a substrate can be manufactured, 20 to 80
μm is preferably selected.

In the present invention, the silane coupling agent such as epoxy silane or amino silane is previously blended into the resin forming the resin composition layer in contact with the conductor circuit 6 so that the adhesion between the conductor circuit 6 and the insulating layer 2 can be improved. It is desirable to improve.

The conductor circuit 6 includes copper, aluminum,
Any of 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. The foil may be plated with a metal such as Ni plating, Ni-Au plating, or solder plating. It is more preferable that the surface of the conductive circuit 6 on the side in contact with the insulating layer be roughened in advance by etching, plating, or the like, from the viewpoint of adhesion to the insulating layer 2.

The metal plate 1 used in the present invention is made of aluminum, iron, copper and alloys thereof, or a clad material thereof, and the thickness thereof is not particularly limited. Aluminum is generally chosen to be 0.5-5.0 mm thick because of its economy.

In the method of manufacturing a metal-based circuit board according to the present invention, a plurality of insulating materials are prepared by adding an additive such as a curing agent to a resin containing an inorganic filler, and a metal plate and / or a conductive foil are prepared. A method of forming a circuit from a conductive foil, or a sheet made of an insulating material in advance, or a sheet made of an insulating material is prepared in advance by applying a heat treatment or the like as needed while applying a multilayer coating thereon, and then through the sheet. It can be obtained by a conventionally known method such as a method of forming a circuit by bonding a metal plate or a conductor foil, or a method of directly using a conductor circuit formed in advance by a circuit instead of the conductor foil in the above method.

Hereinafter, the present invention will be described in more detail with reference to Examples.

[0029]

【Example】

Example 1 An aluminum plate having a thickness of 2.0 mm was first cured with a resin composition A (shown in Table 1) to a thickness of 5 mm.
The first layer was formed so as to have a thickness of 0 μm, and heated at 150 ° C. for 15 minutes. A second layer having a thickness of 50 μm after curing was formed thereon with the resin composition B (shown in Table 1).
Heated at 0 ° C for 10 minutes. Further, after a copper foil having a thickness of 35 μm was press-laminated thereon, the resin composition was cured at 150 ° C. for 5 hours to produce a metal-based substrate.
A desired circuit having a pad portion was formed by etching the copper foil to obtain a metal-based circuit board. The resin composition was cured at 150 ° C. for 5 hours to have a thickness of about 1 m.
A test piece having a m width of about 2 mm and a length of about 50 mm was separately prepared and used for measurement of elastic modulus.

For the above-mentioned cured resin, a dynamic viscoelasticity meter (manufactured by Toyo Baldwin Co., Ltd .; RHEOVIBRO)
There use the N DDV-III-EP type), frequency 11H
z, -100 ° C to +150 under the condition of a heating rate of 2 ° C / min.
The elastic modulus was measured in the temperature range of ° C. Table 1 shows the measurement results of the elastic modulus at -40 ° C. In addition, the results of copper foil peel strength measurement of a metal base substrate at 20 ° C. and 125 ° C., a heat cycle test of a metal base circuit board, and a thermal resistance were measured under the following conditions. Table 2 shows the measurement results.

<Measurement method of copper foil peel strength> Tensilon (manufactured by Orientec; model UCT-1T) was used to
The strength when peeled at a speed of 50 mm / min in a 90- degree direction at a width of cm was determined. The measurement was performed at 20 ° C and 125 ° C.

<Heat cycle test method> Chip size 2.1 mm × 2.5 mm, 3.2 mm × 2.
10 kinds of 5 mm, 5.0 mm × 2.5 mm chip resistors are soldered, each at -40 ° C. for 7 minutes to + 125 ° C.
After performing a heat cycle test 500 times with 7 minutes as one cycle, the presence or absence of cracks in the solder portion was observed with a microscope.

<Method of Measuring Thermal Resistance> A transistor (TO-220; manufactured by Toshiba Corporation) was soldered on a pad to obtain a sample. Transistor on metal base circuit board
While cooling the surface on which no was mounted, electricity was supplied to the transistor, and the temperatures of the transistor and the cooling portion metal plate were measured. Thermal resistance was calculated from the amount of electricity to the transistor and the temperature difference between the transistor and the metal plate.

[0034]

[Table 1]

[0035]

[Table 2]

Example 2 First, a resin composition B was applied to an aluminum plate having a thickness of 2.0 mm so that the thickness after curing was 50%.
A first layer was formed to a thickness of μm and heated at 150 ° C. for 10 minutes. A second layer having a thickness of 50 μm after curing was also formed from the resin composition A thereon, and heated at 150 ° C. for 15 minutes. Further, a third layer was formed thereon using a resin composition B so that the thickness after curing became 50 μm.
Heat at 0 ° C. for 10 minutes. After that, a thickness of 35μ
After pressing and laminating a copper foil having a thickness of m, the resin composition was cured at 150 ° C. for 5 hours to prepare a metal-based substrate. Various physical properties were measured in the same manner as in Example 1 using the metal base substrate and the metal base circuit board obtained from the metal base substrate.
Table 2 shows the results.

[Examples 3 to 5] Various operations were performed in the same manner as in Example 1 except that the resin composition A in the first layer was changed to the resin compositions C to E (shown in Table 1). A metal base substrate and a metal base circuit board were prepared, and physical properties were measured in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 1 A metal-based substrate and a metal-based circuit board were prepared in the same manner as in Example 1 except that the resin composition B was used for both the first and second layers. It was prepared and its physical properties were measured. Table 2 shows the results.

Comparative Example 2 A metal-based substrate and a metal-based circuit board were produced in the same manner as in Example 1, except that the resin composition A was used for both the first and second layers. And physical properties were measured. Table 2 shows the results.

Comparative Example 3 The procedure of Example 1 was repeated, except that the resin composition A of the first layer was changed to a resin composition F (shown in Table 1). A metal-based circuit board was manufactured, and physical properties were measured. The results are shown in Tables 1 and 2.

[0041]

According to the metal-based circuit board of the present invention, the insulating layer is multilayered with a plurality of resin composition layers, and at least a part thereof has a resin having an elastic modulus at -40 ° C. of 2 × 10 ¹⁰ Pa or less. Because of the presence of the composition layer, it provides a highly reliable hybrid integrated circuit with excellent stress relaxation even at low temperatures and no cracks in the solder part even under severe temperature changes under actual use conditions. be able to.

In addition, the metal-based circuit board of the present invention
The resin composition layer may contain an inorganic filler,
The stress relaxation property is improved while maintaining the excellent points of excellent heat dissipation and electric insulation such as withstand voltage. It can be used in various environments and is industrially very useful.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a multilayer circuit board of the present invention.

FIG. 2 is a sectional view showing another example of the multilayer circuit board of the present invention.

[Explanation of symbols]

 Reference Signs List 1 metal plate 2 insulating layer 3 resin composition layer (first layer) 4 resin composition layer (second layer) 5 resin composition layer (third layer) 6 conductive circuit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuo Kato 3-5-1 Asahicho, Machida-shi, Tokyo Denki Kagaku Kogyo Co., Ltd. (72) Inventor Naoki Yonemura 1135 Nakamura Shibukawa-shi, Gunma Electric Chemical Industry Co., Ltd.

Claims (4)

[Claims] 1. A metal-based circuit board having a circuit mounted on a metal plate via an insulating layer having a multilayer structure, wherein the insulating layer comprises at least two or more resin composition layers. In addition, at least one of the resin composition layers is-
A metal-based circuit board having an elastic modulus at 40 ° C. of 2 × 10 ¹⁰ Pa or less. 2. A circuit comprising a resin composition layer having an elastic modulus at −40 ° C. of 2 × 10 ¹⁰ Pa or less and at least one other resin composition layer between the circuit and the circuit. The metal-based circuit board according to claim 1, wherein 3. The metal base circuit according to claim 1, wherein the resin composition layer having an elastic modulus at −40 ° C. of 2 × 10 ¹⁰ Pa or less is made of a cured epoxy resin. substrate. 4. The metal base according to claim 1, wherein the resin composition layer contains a rubber-based polymer having a glass transition temperature of 0 ° C. or less. Circuit board.