JPH09331123A - Metallic base multilayer wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metallic base multilayer wiring board in which warp due to temperature variation is small and which exhibits an improved heat radiation. SOLUTION: An upper insulating layer 3 and an lower insulating layer 5 are provided on both sides of a metallic base 4. A double-sided circuit board 6 is provided on the upper insulating layer 3 on the metallic base 4 to constitute a metallic base multilayer wiring board. The upper insulating layer 3 and the lower insulating layer 5 are made of a textile type material impregnated with resin to which an inorganic filler is added. The double-sided circuit base material 6 of the multilayer circuit board is made of the textile type material on which copper foil 1 is placed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal-based multilayer wiring board which is thin and has a small amount of warpage.

[0002]

2. Description of the Related Art Components such as a DC-DC converter and other on-board power supplies (power supplies to be mounted as components on a printed wiring board) are required to have high output, thinness, and miniaturization.
Accordingly, the metal-based wiring board used therefor is required to have improved heat dissipation and mounting density of components. For this reason, this metal-based wiring board uses a metal having good heat dissipation as a base. On the other hand, in order to reduce the size and increase the packaging density, the components to be packaged are multilayer circuits to increase the packaging density. For example, a multilayer circuit in which conductor circuits are formed on both surfaces of a glass epoxy base material having a thickness of about 0.1 mm is formed, and the multilayer circuit is bonded and laminated on one surface of a metal base via a glass epoxy prepreg.

[0003]

However, the above-mentioned metal-based wiring board has the following problems.
That is, 1) Since the multilayer circuit is laminated on one side of the metal base, when the metal base is made thin, the linear expansion coefficients of the glass epoxy base material and the glass epoxy prepreg are both smaller than that of the metal, so When the heating state at the time of bonding is cooled to normal temperature, warpage occurs so that the conductor circuit side becomes convex. If this warpage is large, the thickness of the DC-DC converter unit or the like is increased by the amount of the warpage, which makes it difficult to reduce the thickness of this unit. Further, if this warp is large, problems may occur in solder paste printing or automatic mounting work when components are mounted on the multilayer circuit.
Further, when the components are mounted and heated to a high temperature in the solder reflow bath, the conductor circuit side on which the components are mounted becomes concave and the conductor circuit side becomes convex at the time of cooling, so stress is applied to the solder fixing the six products. There is a risk of cracks being added. 2) The glass epoxy base material does not have good thermal conductivity. Therefore, if conductor circuits are formed on both sides and adhered and laminated to the metal base via the glass epoxy prepreg, the heat generated by the parts on the circuit or the circuit conductors The heat dissipation is limited, and there is a limit to increasing the output of the power supply unit. Further, in the case of the same power output, the mounting density of the heat-generating components is limited, and miniaturization is limited.

[0004]

The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 provides an insulating layer on both surfaces of a metal base, and an insulating layer on one surface of the metal base. A metal-based multilayer wiring board having a multilayer circuit board provided thereon, wherein the insulating layer is a woven material impregnated with a resin containing an inorganic filler, and the multilayer circuit substrate of the multilayer circuit board is the woven material. It is characterized in that it is formed by laminating copper foil on a sheet. The invention according to claim 2 is characterized in that, in the invention according to claim 1, the insulating layer provided on the surface opposite to the surface on which the metal-based multilayer circuit board is provided has unevenness on the surface. It is a thing.

In the present invention, the metal serving as the metal base includes iron, stainless steel, copper, aluminum, or alloys thereof. Among these metals, aluminum is preferable in view of its small specific gravity, good thermal conductivity, and good workability. In particular, pure aluminum (JIS1100) subjected to alumite treatment is preferable because it has good adhesiveness. Further, a metal base whose surface is provided with adhesiveness by physical roughening such as sandblasting or chemical polishing such as chemical conversion treatment may be used. Further, the thickness of the metal base is made as thin as possible in order to make the wiring board thinner. However, if the thickness is reduced to lower the rigidity, the insulating layer is likely to be damaged due to bending or the like in the wiring board manufacturing process or the power supply unit manufacturing process. Therefore, the thickness is preferably 0.5 mm or more.

As the resin containing the inorganic filler, an adhesive insulating resin such as epoxy type, polyimide type, acrylic type, BT range or a mixture thereof, silica (SiO ₂ ), alumina (Al ₂ O ₃ ). An inorganic filler such as 70 to 80 wt% is used.

For the insulating layer, a resin such as the above-mentioned inorganic filler is applied and impregnated on a substrate such as a glass cloth or a glass mat and dried to obtain a woven material having a thickness of 0.1 to 0.2 mm (prepreg state). Stuff). In addition, the multilayer circuit board uses a glass epoxy prepreg similar to that described above as a base material, and heats and pressurizes copper foil on both surfaces thereof to cure the base material to form a copper-clad board.

As described above, in the metal-based multilayer wiring board of the present invention, since the insulating layers are formed on both sides of the metal base and the multilayer circuit board is laminated on one side, the insulating layer is provided only on one side of the metal base. Compared with the conventional case of forming, the structure in the thickness direction becomes closer to symmetry, and even if the metal base is thinned, warpage caused by temperature change is reduced. Further, since the insulating layer that constitutes the metal-based multi-layer wiring board and the base material of the multi-layer circuit board are made of a woven material in which an inorganic filler is added to improve thermal conductivity, the heat dissipation is excellent and the power supply unit is excellent. Output power can be increased. In addition, when unevenness is provided on the surface of the insulating layer provided on the surface opposite to the surface provided with the metal-based multilayer circuit board, and the surface area is increased,
The heat dissipation from the back surface of the metal-based multilayer circuit board is further improved.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of one embodiment of a metal-based multilayer wiring board according to the present invention. In the present embodiment, an Alumite-treated A of 0.5 mm thickness is used.
The upper surface insulating layer 3 and the lower surface insulating layer 5 are arranged on both surfaces of the base 4, and the double-sided circuit board 6 in which the conductors 1 are provided on both surfaces of the base material 2 is arranged on the upper surface insulating layer 3. There is.

Here, the upper surface insulating layer 3 has a thickness of 0.15 mm, which is obtained by coating and impregnating a glass cloth having a thickness of 0.1 mm with an epoxy adhesive containing 82 wt% of an alumina filler and drying the semi-cured state. Inorganic filler-filled glass prepreg (1) was prepared and placed on the upper surface of the Al base 4. In addition, the lower surface insulating layer 5 is formed by stacking two sheets of the above-mentioned inorganic filler-filled glass prepreg to have a thickness of 0.30 mm and arranged on the lower surface of the Al base 4.

Further, the double-sided circuit board 6 was manufactured as follows. That is, a 105 μm electrolytic copper foil was placed on both sides of the above-mentioned inorganic filler-filled glass prepreg and heat-pressed by a vacuum press at 170 ° C. for 60 minutes to obtain a double-sided copper-clad substrate. A through hole is opened in this double-sided copper-clad substrate, 20 μm of copper is plated, and then a circuit is formed by etching.

The metal-based multilayer wiring board of this embodiment is
An upper surface insulating layer 3 and a double-sided circuit board 6 are sequentially arranged on the upper surface of the Al base 4, and a lower surface insulating layer 5 is arranged on the lower surface of the Al base 4, and a stainless steel cover plate in which unevenness having a depth of 0.1 mm is formed by sandblasting. Place on a vacuum press at 170 ℃ ×
It was manufactured by thermocompression bonding for 60 minutes.

Next, as a conventional example, a thickness of 0.15 is formed on the upper surface of a 1.0 mm thick Al base which has been subjected to an alumite treatment.
mm upper surface insulating layer made of glass epoxy prepreg,
A double-sided circuit board made of a glass epoxy base material having a thickness of 0.1 mm was sequentially arranged, and a metal-based multilayer wiring board was produced in the same manner as in the above embodiment. In this case, the Al-based lower surface insulating layer is not provided.

For the above-mentioned embodiment and the conventional example, 100
A metal-based multilayer wiring board having a size of mm × 60 mm was manufactured, and the warpage was measured at room temperature. The warpage was measured by placing a metal-based multilayer wiring board on a flat plate and measuring the distance between the central portion of the metal-based multilayer wiring board and the flat plate with a micro gauge. Further, with the power transistor, which is a heat-generating component, mounted, a predetermined energization was performed for a predetermined time, and an increase in surface temperature of the power transistor (difference from ambient temperature) was measured. Table 1 shows the measurement results.

[0015] Here, the total thickness is the total thickness of the metal-based multilayer wiring board excluding the thickness of the copper foil which becomes the conductor.

As can be seen from Table 1, in the embodiment, as compared with the conventional example, the amount of warpage is small, although the thickness of the entire metal-based multilayer wiring board is thin. Therefore, the total value of the amount of warpage and the total thickness is reduced, so that by using this metal-based multilayer wiring board, it is possible to make the power supply unit thinner. Also,
Regarding the temperature difference, although the thin Al base is used, the embodiment shows a smaller value than the conventional example, the temperature rise is small, and the heat dissipation is superior to the conventional example. Shows.

The present invention is not limited to the above embodiment,
A circuit board having two or more layers may be used as the circuit board.

[0018]

As described above, according to the present invention, there is provided a metal-based multilayer wiring board in which insulating layers are provided on both sides of a metal base, and a multilayer circuit board is provided on the insulating layer on one side of the metal base. The insulating layer is made of a woven material impregnated with a resin to which an inorganic filler is added, and the multilayer circuit substrate of the multilayer circuit board is made by laminating a copper foil on the woven material. There is an excellent effect that the generated warp can be reduced and the heat dissipation is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a metal-based multilayer wiring board according to the present invention.

[Explanation of reference numerals] 1 conductor 2 base material 3 upper surface insulating layer 4 Al base 5 lower surface insulating layer 6 double-sided circuit board

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Koichi Oyasu 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (2)

[Claims] 1. A metal-based multi-layer wiring board in which an insulating layer is provided on both sides of a metal base, and a multi-layer circuit board is provided on the insulating layer on one side of the metal base, wherein the insulating layer is a resin containing an inorganic filler. 2. A metal-based multilayer wiring board, comprising a woven fabric impregnated with a woven fabric, wherein the multilayer circuit substrate of the multilayer circuit board is formed by laminating a copper foil on the woven fabric. 2. The metal-based multilayer wiring board according to claim 1, wherein the insulating layer provided on the surface opposite to the surface provided with the metal-based multilayer circuit board has irregularities on the surface.