JPH07302978A - Metal-based multilayer circuit board - Google Patents

Abstract

PURPOSE:To obtain an excellent heat-dissipating property by a method wherein the thermal conductivity of each of an insulating board and an adhesive layer for an upper-layer circuit board and an insulating layer for a metal-based circuit is set at a specific value and the thickness of each of them is set within a specific range. CONSTITUTION:A metal-based multilayer circuit board has a structure in which an upper-layer circuit board composed of an insulating board 3 provided with a circuit 4 on the surface via an adhesive layer 6 is laminated on, and integrated with, a metal-based circuit board 7 forming a circuit 5 on a metal plate 1 via an insulating layer 2. A glass epoxy material, a polyimide material, a phenol material or a ceramic material is used for the insulating board 3, its thermal conductivity is at 6X10<-4> to 1.2X10<-3>cal/cm-sec deg.C, and its thickness is at 30 to 70mum. Any organic adhesive can be used for the adhesive layer, its thermal conductivity is at 3X10<-4> to 1X10<-3>cal/cm.sec deg.C, and its thickness is at 20 to 50mum. A ceramic or a polymer resin insulating layer is used for the insulating layer 2, its thermal conductivity is at 3.5X10<-3> to 1.0X10<-2>cal/cm.sec deg.C, and its thickness is at 60 to 200mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal-based multi-layer circuit board, and more particularly to a metal-based multi-layer circuit board having a noise shielding property, an excellent withstand voltage property and a good heat dissipation property.

[0002]

2. Description of the Related Art In recent years, in a circuit board for mounting a semiconductor, how to dissipate heat generated from the semiconductor element in response to demands for miniaturization of the board, high density mounting and high power of the semiconductor element. Is a problem. Under these demands, in recent years, mainly in the field of power supply, a metal base circuit board on which a circuit is formed after bonding a conductive metal foil on the metal base circuit board via an insulating layer has excellent heat dissipation properties. Because of having, its use is increasing. However, since the metal base circuit board has a structure in which a thin insulating layer is applied on the metal base board, there is a problem that noise is likely to occur and an electronic module malfunctions easily. In order to shield this noise and realize higher density mounting, for example, a metal base circuit board is laminated with an upper layer circuit board having circuits on both sides, and a heat-generating electronic component is mounted on the upper layer circuit board. Base multilayer circuit boards are being used. In this metal-based multilayer circuit board, the heat generated through the insulating board, which is the insulating layer of the upper-layer circuit board, the adhesive layer for bonding the upper-layer circuit board, the insulating layer of the metal-based circuit board, and a large number of insulating layers is used. Although it is diffused, there is a problem that the temperature of the electronic component rises due to insufficient radiation, which causes malfunction.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and examines the thickness and the heat transfer coefficient of each insulating layer constituting a metal-based multilayer circuit board, and appropriately determines these. It has been found that a metal-based multilayer circuit board having a small heat resistance and a good heat dissipation property can be obtained by setting it. That is, an object of the present invention is to obtain a metal-based multilayer circuit board having excellent heat dissipation properties without impairing the noise shielding property and the withstand voltage characteristic.

[0004]

A metal-based multilayer circuit board of the present invention comprises a metal base circuit board having a circuit formed on at least one main surface of a metal plate via an insulating layer,
In a metal-based multi-layer circuit board in which an upper layer circuit board having circuits on both sides via an adhesive layer is laminated and integrated,
(1) The thermal conductivity of the insulating substrate of the upper circuit board is 6 × 1.
^{0 -4 ~1.2 × 10 -3 cal /} cm. Sec. Is ° C., and that the thickness of 30 to 70 .mu.m, (2) the thermal conductivity of the adhesive layer is 3 × 10 ^{-4 ~1 × 10 -3 cal / cm.} sec
^. A ° C., and its thickness is 20 to 50 m, (3) the metal base circuit thermal conductivity of the substrate of the insulating layer is ^{3.5 × 10 -3 ~1.0 × 10 -2} cal / ^{cm. sec.} is ° C., and the thickness is 60～200Myuemu, is characterized in.

[0005]

The present invention will be described in more detail with reference to the drawings. As shown in FIG. 1, the metal-based multi-layer circuit board of the present invention is provided on a metal base circuit board 7 on which a circuit 5 is formed on a metal plate 1 via an insulating layer 2 and on both sides via an adhesive layer 6. It has a structure in which an upper circuit board made of an insulating board 3 having a circuit 4 is laminated and integrated.

Base metal plate 1 used in the circuit board of the present invention
As, aluminum and aluminum alloys having good thermal conductivity, copper and copper alloys, iron and iron alloys, etc.,
Or copper / iron-nickel alloy, aluminum / iron-
It is possible to use a two-layer composite material such as a nickel-based alloy or a three-layer multilayer composite material such as copper / iron-nickel-based alloy / copper and aluminum / iron-nickel-based alloy / aluminum. The thickness of the base metal substrate 1 is not particularly limited, but 0.5 mm to 3.0 mm is generally used.

The material for forming the circuits 4 and 5 is copper, aluminum, nickel, iron, tin, silver, titanium or the like, or an alloy containing two or more kinds of these metals and a clad foil using each metal. Used. In addition, the method of manufacturing the foil at this time may be either an electrolytic method or a rolling method, and the foil may be subjected to metal plating such as Ni plating, Ni + Au plating, and solder plating.

The upper layer circuit board has circuits on both sides.
The circuit on the underside of the serves as a magnetic shield. Bottom times
The path does not necessarily have to form a circuit of a particular shape,
It is possible to play the role of Qi Shildo. For example, simply
It may be plate-shaped. And this upper layer circuit board
As the insulating substrate 3 of, glass such as FR-4, FR-5, etc.
Epoxy material, polyimide material, phenolic material and ceramic
An insulating material such as a wax material can be used. And that
Thermal conductivity is 6 × 10^-Four~ 1.2 x 10^-3cal / cm ^.sec^.
C. and its thickness is 30 to 70 .mu.m. So
Has a thermal conductivity of 6 × 10^-Fourcal / cm^.sec^.Below ℃
The thermal resistance of the metal-based multilayer circuit board increases
1.2 × 10^-3cal / cm^.
sec^.It is difficult to industrially obtain one having a temperature higher than ℃.
If the thickness is less than 30 μm, the withstand voltage will decrease.
However, if it is larger than 70 μm, the thermal resistance becomes large, which is preferable.
Absent.

As the adhesive layer for adhering the upper circuit board, any organic adhesive such as acrylic, epoxy, silicone, urethane or the like can be used. Its thermal conductivity is 3 × 10 ^-4 〜 1 × 10 ^-3 cal /
^{cm. sec.} it is ℃ and a thickness of 20 to 50 m. Its thermal conductivity of 3 × 10 ^-4 smaller than the metal base good heat dissipation heat resistance and increased and interest of the multilayer circuit board can not be ^{obtained, 1 × 10 -3 cal / cm} . Sec. From ℃ Large ones are difficult to obtain industrially. If the thickness is less than 20 μm, the withstand voltage is lowered, and if it is more than 50 μm, the thermal resistance is increased, which is not preferable.

The insulating layer 2 of (3) used in the present invention includes various ceramics, a polymeric resin insulating layer containing a filler made of inorganic powder, a polymeric resin insulating layer containing glass fiber, and a heat-resistant material. A polymeric polymer resin insulating layer can be used. As the polymer resin, an epoxy resin,
Phenol resin, polyimide resin, various engineered plastics, etc. are used. As the filler, materials such as alumina, beryllia, boron nitride, magnesia, silica, silicon nitride and aluminum nitride are preferable.

The thermal conductivity of this insulating layer is 3.
5 x 10^-3~ 1.0 x 10^-2cal / cm ^.sec^.℃,
And the thickness is 60 to 200 μm, and its thermal conductivity
Is 3.5 × 10^-3Smaller and metal based multilayer circuit board
The thermal resistance of the
Without, 1.0 × 10^-2cal / cm^.sec^.Greater than ℃
Is difficult to obtain industrially. Also, the thickness of this insulating layer
Is less than 60 μm, the withstand voltage is reduced to 200 μm
If it is larger than the above range, the heat resistance becomes large, which is not preferable.

The contents of the invention will be specifically described below based on examples.

【Example】

Example 1 First, an epoxy resin filled with alumina was applied on a 510 × 510 × 1.5 mm t aluminum plate, and a copper foil having a thickness of 35 μm was laminated on the epoxy resin and cured by heating. ^{.2 × 10 -3 cal / cm.} sec. at ° C.,
After forming an insulating layer having a thickness of 150 μm, a desired conductive circuit was formed by etching. Next, 70μ foil thickness on top
m and a lower surface with a conductive foil having a thickness of 35 μm, and having a thermal conductivity of 8 × 10 ⁻⁴ cal / cm · sec ^. ° C. and a thickness of 50 μm, the desired circuit and through holes were formed on the glass epoxy substrate. 35 of the lower surface of the glass epoxy board which is an insulating board
Pre-punched into a uniform shape with the foil side of μm as the adhesive surface, the thermal conductivity is 5 × 10 ^-4 cal / cm · sec ^. ℃ and the thickness is 2
5 μm adhesive sheet (DuPont; Piralux)
Was laminated on the insulating layer of the aluminum-based metal-based circuit board described above. The breakdown voltage and thermal resistance of this metal-based multilayer circuit board were measured. The dielectric breakdown voltage was measured by the step-up method (AC voltage) specified in JIS Z1020. The thermal resistance and the noise shield property were measured by the following measuring methods. The results are shown in Table 1 and the breakdown voltage is 10 kV.
As described above, the thermal resistance was 1.98 ° C / W. Moreover, the noise shielding property was also good.

[0013]

[Table 1]

(Measuring Method of Thermal Resistance) A conductive foil on the upper layer circuit board of the metal base multilayer circuit board in which the upper layer circuit board is formed on the metal base circuit board is etched to obtain 10 ×.
A 15 mm pad portion is formed, and a transistor (TO220, manufactured by Toshiba Corporation) is soldered on this. The base metal plate surface side was cooled, and the transistor was energized, and the thermal resistance was measured from the temperature difference between the transistor side and the metal plate side sandwiching the insulating layer and the energization amount. (In the method described in the Denka HITT plate catalog, the transistor is soldered onto the upper circuit board).

(Measurement Method of Noise Shielding Property) In the metal-based multilayer circuit board obtained as in Example 1, the same circuit as the circuit formed on the metal-based circuit board is formed on the upper layer circuit board, The noise reduction amount is the amount of noise generated by only the circuit formed on the upper layer circuit board at 200 kHz, minus the amount of noise generated by only the circuit formed on the metal base circuit board at 200 kHz. And the value (dB) was used as the noise shield property. The amount of noise generated is Yokogawa Hewlett Packard; 2/4 channel FFT analyzer H
It was measured by P25670A.

[Embodiment 2] First, 510 × 510 × 1.
5mm epoxy resins Hamazai alumina coated on the aluminum plate t, on the cured by heating laminated copper foil of 35μm thickness thereof, the thermal conductivity of ^{3.5 × 10 -3 cal / cm.} Se
c ^. After forming an insulating layer having a thickness of 60 μm at 0 ° C., a desired conductive circuit was formed by etching. Next, a glass epoxy substrate having a heat conductivity of 6 × 10 ⁻⁴ cal / cm · sec ^. ° C. and a thickness of 30 μm, which has a conductive foil with a foil thickness of 70 μm on the upper surface and a foil thickness of 35 μm on the lower surface, has a desired circuit and After forming the through-holes, the heat conductivity was 3 × 10 ^-4 cal / cm · sec ^. ℃ and the thickness was punched into a certain shape in advance with the 35 μm foil side of the lower surface of the insulating glass epoxy substrate as the adhesive surface ^. A 20 μm adhesive sheet was used to bond the aluminum-based metal-based circuit board to the insulating layer. The breakdown voltage and thermal resistance of this metal-based multilayer circuit board were measured. The results are shown in Table 1. The dielectric breakdown voltage was 6.2 kV and the thermal resistance was 1.14 ° C / W. Moreover, the noise shielding property was also good.

[Examples 3 to 5] Table 1 shows the thickness and thermal conductivity of the insulating layer of the metal base circuit board, the thickness and thermal conductivity of the upper layer circuit board, and the thickness and thermal conductivity of the adhesive sheet. A metal-based multilayer circuit board was prepared in the same manner as in Example 1 except that The breakdown voltage and thermal resistance of these metal-based multilayer circuit boards were measured in the same manner as in Example 1. The results are shown in Table 1, but the dielectric breakdown voltage was high and the thermal resistance was small.

Comparative Example 1 As a comparative example, 510 × 51
Alumina-filled epoxy resin is coated on a 0 × 1.5 mm t aluminum plate, and a 35 μm thick copper foil is laminated on it and heat-cured. The thermal conductivity is 1 × 10 ^-2 cal / cm.
After forming an insulating layer having a thickness of 50 μm at sec ^. ° C., a desired circuit was formed by etching. Next, a conductive foil having a foil thickness of 70 μm on the upper surface and a foil thickness of 35 μm on the lower surface,
After forming a desired circuit and a through hole on a glass epoxy substrate having a thermal conductivity of 1.2 × 10 ⁻³ cal / cm · sec ^. Insulation of the aluminum-based metal base circuit board using a prepreg with a thermal conductivity of 1 × 10 ^-3 cal / cm · sec ^. Laminated on layers. The dielectric breakdown voltage and thermal resistance of this metal-based multilayer circuit board were measured in the same manner as in Example 1. The results are shown in Table 1. The dielectric breakdown voltage was 4.5 kV and the thermal resistance was 1.25 ° C / W.

[Comparative Examples 2 and 3] Table 1 shows the thickness and thermal conductivity of the insulating layer of the metal base circuit board, the thickness and thermal conductivity of the upper circuit board, and the thickness and thermal conductivity of the adhesive sheet. A metal-based multilayer circuit board was prepared in the same manner as in Comparative Example 1 except that The breakdown voltage and thermal resistance of these metal-based multilayer circuit boards were measured by the same methods as in Example 1. The results are shown in Table 1. Although the dielectric breakdown voltage was high, the thermal resistance was large, which was not preferable.

[0020]

According to the present invention, it is possible to obtain a metal-based multi-layer circuit board which is excellent in noise shielding property, withstand voltage property and good in heat dissipation property.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the structure of a metal-based multilayer circuit board of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1; Metal plate 2; Insulating layer of metal base circuit board 3; Adhesive layer 4; Insulating board of upper layer circuit board 5; Upper surface circuit of upper layer circuit board 6; Lower surface circuit of upper layer circuit board 7; Circuit of metal base circuit board 8; Metal base circuit board

Claims (1)

[Claims] 1. An upper layer circuit board having circuits on both sides thereof is laminated via an adhesive layer on a metal base circuit board having a circuit formed on at least one main surface of a metal plate via an insulating layer. In the integrated metal-based multilayer circuit board, (1) the thermal conductivity of the insulating substrate of the upper layer circuit board is 6 × 1.
^{0 -4 ~1.2 × 10 -3 cal /} cm. Sec. Is ° C., and that the thickness of 30 to 70 .mu.m, (2) the thermal conductivity of the adhesive layer is 3 × 10 ^-4 ~ 1 x 10
^-3 cal / ^{cm. Sec.} Is ° C., and its thickness is 20 to 50
it is [mu] m, (3) the metal base circuit thermal conductivity of the substrate of the insulating layer is ^{3.5 × 10 -3 ~1.0 × 10 -2} cal / cm. a ^sec. ° C., and a thickness A metal-based multilayer circuit board having a thickness of 60 to 200 μm.