JPH0442592A - Metallic-core circuit board - Google Patents

Abstract

PURPOSE:To prevent impurities from being taken into an insulating layer at the time of etching a conductor layer and, at the same time, the dielectric breakdown characteristic from being lowered by a bending process by sticking a flexible substrate which is a laminated body of an insulating layer and the conductor layer and metallic thin plate to each other with the insulating layer inside by using a bonding agent layer. CONSTITUTION:A bonding agent is applied to the surface of the insulating resin film 4 of a substrate which is excellent in flexibility, bonding property, etc., and a metallic thin plate 7 of aluminum, etc., is stuck to the bonding agent layer 6. Since the substrate of two-layestructure is stuck to the bonding agent layer 6, the layer 6 does not crop out and no impurity is taken into the layer 6 when a circuit is formed by etching the conductor layer 5. In addition, since the insulating resin film 4 is put on the bonding agent layer 6, no dielectric breakdown occurs even when the layer 6 is cracked.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a metal core circuit board on which a semiconductor element is mounted and which is used as a heat generating board, that is, a power source or a high power board.

(Prior Art) Conventionally, various materials have been used and various packages have been applied to circuit boards on which electronic components such as semiconductor elements are mounted. Among these circuit boards, metal core circuit boards that have a thin metal plate such as aluminum as the core have good heat resistance, heat dissipation, shielding properties, and bending workability, so in recent years, they have been used as power supplies, It is widely considered to be used as a high-power board. be.

The structure of a conventional metal core circuit board is shown below.

That is, as shown in Fig. 2, the structure is such that an insulating layer 2 is provided on a thin plate 1 made of a lightweight and highly rigid metal such as aluminum, and a conductive layer 3 made of copper or the like is provided on top of the thin plate 1. ing.

In such a metal core circuit board, in order to increase the adhesive strength between the thin metal plate 1 and the conductor layer 3, the insulating layer 2 is
A layer of adhesive is further coated on top of an insulating coating formed of an adhesive, or provided by powder coating, electrodeposition coating, or the like.

(Problem to be Solved by the Invention) However, in such conventional metal core circuit boards, the insulation characteristics of the board are determined by the characteristics of the adhesive used as the insulating layer 2, so ordinary adhesives When using , there were various problems as shown below.

That is, (1) The bending process may cause cracks in the insulating layer 2 (adhesive layer), resulting in a decrease in dielectric breakdown characteristics.

(2) Not only does the insulating layer 2 made of an adhesive or the like contain impurities from the beginning, but also the insulating layer 2 tends to incorporate impurities when etching the conductor layer 3 to form a circuit. Therefore, the insulation properties tend to deteriorate.

(3) When applying adhesive, uneven application tends to occur. Since a circuit pattern is directly formed thereon, such coating unevenness is exposed and is unfavorable in terms of appearance.

There were various problems such as.

The present invention was made to solve these problems, and not only has good insulation properties and bending workability, but also prevents the insulating layer from taking in impurities when etching the conductive layer.
Another object of the present invention is to provide a metal core circuit board whose dielectric breakdown characteristics do not deteriorate due to bending.

[Structure of the Invention] (Means for Solving the Problems) The metal core circuit board of the present invention includes a substrate formed by laminating a flexible insulating layer and a conductor layer, and a thin metal plate, It is characterized by being attached to the inside through an adhesive layer.

(Function) In the metal core circuit board of the present invention, a thin metal plate is bonded to the insulating layer surface of the board formed by laminating a flexible insulating layer and a conductive layer via an adhesive layer. Because of this, it has good heat dissipation, insulation properties, and bendability.

Even if the adhesive layer cracks due to bending, the insulating layer of the board is bonded on top of it.
No dielectric breakdown occurs.

Furthermore, since the insulating layer is interposed between the adhesive layer and the conductor layer, impurities do not enter the adhesive layer when etching the conductor layer.

Furthermore, when the circuit is formed, the insulating layer immediately below is exposed and the adhesive layer is not exposed, so there is no appearance defect caused by uneven application of the adhesive.

Furthermore, it can be manufactured by bonding together a two-layer structure board, in which a conductor layer is provided on a highly flexible insulating layer such as an insulating film, and a thin metal plate using an adhesive. Since the substrate can be used as is, manufacturing is easy and inexpensive.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an embodiment of the metal core circuit board of the present invention.

In the figure, reference numeral 4 indicates a highly flexible insulating resin film such as a polyimide film, on which a conductor layer 5 such as copper foil is laminated.

A known adhesive is applied to the four sides of the insulating resin film of such a substrate, which has excellent flexibility and good wire bonding properties, to a thickness of 5 to 20 μm using a coating device such as a coater. On this adhesive layer 6, a thin plate 7 of metal such as aluminum is superimposed and bonded.

Here, it is desirable to form the adhesive layer 6 by coating it as thinly as possible, and it is also desirable to use an adhesive that contains as few impurities as possible.

In the metal core circuit board of the embodiment configured as described above, the two-layer structure board is stacked on the adhesive layer 6, so when etching the conductor layer 5 to form a circuit, the adhesive The agent layer 6 is not exposed and does not take in impurities. Furthermore, since the adhesive itself has few impurities, there is no increase in impurities entering in such post-processes, and a package with good characteristics can be obtained.

In addition, in the conventional metal core circuit board, there was a possibility that the adhesive layer 6 would crack during bending, resulting in dielectric breakdown, but in the metal core circuit board of the example, the adhesive layer 6 Since the insulating resin film 4 is laminated thereon, even if the adhesive layer 6 cracks, it will not lead to dielectric breakdown.

Furthermore, after the circuit is formed by etching the conductor layer 5, the insulating resin film 4 under the conductor layer 5 is exposed and the adhesive layer 6 is not exposed, so even if there is uneven application of the adhesive, the appearance will not be damaged.

[Effects of the Invention] As explained above, in the metal core circuit board wire of the present invention, the characteristics of the two-layer board bonded to the metal thin plate are clearly exhibited, regardless of the characteristics of the adhesive used. , good bending workability and wire bonding properties.

Further, impurities are not introduced into the adhesive layer during the etching process of the conductor layer, and the insulation properties do not deteriorate.

Furthermore, the occurrence of dielectric breakdown due to bending is prevented, and the appearance is also good.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the metal core circuit board of the present invention, and FIG. 2 is a sectional view of a conventional metal core circuit board. 4...Insulating resin filler 5...Conductor layer 6...Adhesive layer 7...Thin metal plate . room

Claims (1)

[Claims] (1) A substrate formed by laminating a flexible insulating layer and a conductive layer, and a thin metal plate are bonded together via an adhesive layer with the insulating layer inside. Metal core circuit board.