JPH0823165A - Manufacture of metal cored wiring board using copper foil with insulating bonding agent - Google Patents

Abstract

PURPOSE:To fill a perforated part and form an insulating bonding layer alto gether by forming a double-layer construction of a copper foil with an insulating bonding agent in terms of a first layer with a low flow and a second layer with a high flow and heating and pressuring a perforated metal board and the copper foil. CONSTITUTION:After varnish is applied to a copper foil, 35mum thick, to a prescribed film thickness as a first layer, it is dried at 150 deg.C for 10 minutes. On this coat, another varnish is applied to a prescribed film thickness after drying as a second layer, and it is dried to form a copper foil with an insulating bonding agent. Then, an aluminum sheet of 0.1mm to 2mm in thickness, say 0.3mm thick aluminum sheet, is perforated and treated with surface finish polishing to make the surface a silane coupling. Next, the copper foil with the insulating bonding agent is built over an aluminum sheet by a press, and the perforated part of the aluminum sheet is drilled to perforate to form a through hole. The through hole is plated and circuits on both surfaces are connected. Finally, a pattern 3 is formed by etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a metal core wiring board.

[0002]

2. Description of the Related Art In recent years, the number of high-density mounting of power transistors and hybrid ICs driven by high voltage is increasing, and the demand for wiring boards with excellent heat dissipation is increasing. Is used. Usually, this metal base wiring board is made by stacking an insulating layer and a copper foil on a metal plate and laminating and integrating them, or by punching a metal plate and filling the hole with resin for filling, then laminating and integrating. What you have done is known.

[0003]

However, the one in which the insulating layer and the copper foil are superposed and laminated integrally on the metal plate has a limit in increasing the wiring density because of the single-sided single-layer wiring. In addition, there is a problem in that the cost is increased because the manufacturing process becomes long because the metal plate is drilled, the hole is filled with the resin for filling the hole, and then integrated with the resin. Cracks occur at the interface of layers,
There were also problems such as the occurrence of electrolytic corrosion.

The cost can be reduced because the number of steps can be greatly reduced if the filling and laminating of the perforated portion can be performed at the same time. You can, but because the flow is large,
The thickness of the insulating layer cannot be kept constant, the required insulation resistance cannot be obtained, and if the flow is reduced, the required insulation resistance can be obtained, but the holes cannot be filled. No material suitable for various processes has been obtained.

It is an object of the present invention to provide a method for efficiently manufacturing a metal core wiring board which is capable of filling holes and forming an insulating adhesive layer at the same time and which is excellent in wiring density.

[0006]

A method of manufacturing a metal core double-sided wiring board according to the present invention is characterized by the following steps. a. Step of producing a copper foil with an insulating adhesive material formed by arranging a coating film on the copper foil b. Process of punching a metal plate having a thickness of 0.1 mm to 2 mm c. Copper foil with insulating adhesive material obtained in step a, and step b
Step of heating and pressing the perforated metal plate obtained in step 1 to perform laminated integration. D. A step of making a hole in a portion where interlayer connection is performed e. Process of electrically connecting both sides of the circuit by plating and conductive paste f. Step of forming a circuit by etching g. A step of bending and / or drawing the substrate as necessary

The copper foil with an insulating adhesive material used in such a method is prepared by applying an insulating adhesive material onto a copper foil and then applying B or C.
It can be prepared by heating and curing in a stage state, then applying an insulating adhesive material thereon, and heating and curing in an A or B stage state.

It can also be prepared by applying an insulating adhesive material on a single-sided copper-clad laminate and heating and curing it in the A or B stage state.

The insulating adhesive material used in the present invention may be made of an epoxy resin, rubber, or a high thermal conductive inorganic filler. The resin composition of the insulating adhesive material needs to contain 10 vol% or more of a low molecular weight epoxy resin having a molecular weight of 500 or less in order to improve the flowability. As such an epoxy resin, as a commercially available product, Epicoat 812, 828 (trade name of Yuka Shell Co., Ltd.)
And the like. The curing agent for the epoxy resin is not particularly limited, but one having a long varnish life and high potential is desirable. For example, at least one kind of tertiary amine, acid anhydride, imidazole compound, polyphenol resin, masked isocyanate and the like can be used. In addition, it is necessary to add a flexibility-imparting component in order to prevent the occurrence of cracks during drilling. As such a material, one or more kinds of polymer substances having good electric insulation, such as acrylic rubber, NBR, epoxy modified acrylic rubber, epoxidized polybutadiene, and phenoxy resin can be used.

Further, in order to improve the adhesiveness between the copper foil and the adhesive sheet, it is preferable to use a silane coupling agent. For example, as a commercially available product, NUC-A187,
A189, A1160 (manufactured by Nippon Unicar Co., Ltd., trade name) and the like can be used in combination. With such a composition, an insulating adhesive material having excellent flowability and adhesiveness can be obtained even when an inorganic filler is contained.

Further, heat dissipation can be improved by adding an inorganic filler having a high thermal conductivity. Alumina, silica, aluminum nitride or the like can be used as the inorganic filler having such a high thermal conductivity. The addition amount is preferably in the range of 10 to 75% by volume. The reason for this is that as the amount of addition increases, the heat dissipation improves, but on the other hand, the flowability of the adhesive sheet decreases and the hole filling property deteriorates.
Further, since the adhesiveness between the copper foil and the adhesive sheet is lowered, if the added amount exceeds 75% by volume, sufficient solder heat resistance reliability cannot be obtained. Further, if the addition amount is 10% by volume or less, the effect of improving heat dissipation is small.

The addition of a filler and a rubber component has the following advantages, so that a composition comprising an epoxy resin, a filler and a rubber is preferable. That is, 1) Although small cracks are generated at the time of drilling through-holes, their growth is suppressed at the interface of the filler and rubber, so that large cracks are less likely to occur. 2) Due to frictional heat when drilling holes, temperature rise and thermal expansion of the resin locally occur, which often causes cracks. It is possible to suppress the local temperature rise. 3) Since the side surface of the through hole has appropriate unevenness, the adhesion of plating is good.

For the metal plate to be the core, aluminum, iron and alloys containing these as main components can be used, and the thickness is preferably 0.1 mm to 2 mm. If this metal plate is thicker than 2 mm, it becomes difficult to fill the holes. Further, it is preferable that the metal plate is previously subjected to drilling, surface polishing treatment, and silane coupling agent treatment.

The insulating adhesive material is produced by applying a varnish as a first layer of a coating film on a copper foil and heating and curing the varnish in a B or C stage state to reduce the flowability.
A second layer of the coating film is applied on this, and this is heat-cured in the A or B stage state.

As a method for applying the varnish to the copper foil, there are a bar coater, a lip coater, a roll coater and the like. However, if the method has few defects such as craters and voids and the coating film thickness is almost uniform, Any method will do.

Next, a copper foil with an insulating adhesive material and a metal plate are laminated under pressure and heating, but it is preferable to use a cushioning material in order to improve the filling property of the insulating adhesive material into the holes. Examples of such cushioning materials include silicone rubber sheets and polyethylene sheets.

Next, a hole is drilled with a drill or punch, and the diameter of the hole is preferably smaller than the diameter of the hole previously drilled in the metal plate by 0.4 mm or more. The reason is,
This is because even if a work error of about 0.1 mm occurs, insulation failure will not occur.

Next, interlayer connection between both surfaces is performed, which can be performed by using a conventionally used method such as conductive paste, plating, wire bonding or the like.
The subsequent circuit formation can be performed by forming an etching resist on the copper foil and removing unnecessary copper by etching to form a conductor circuit, or by forming a coating film by plating. Furthermore, after the conductor circuit is formed, the substrate can be bent and drawn to match the shape to be incorporated in an electronic device.

[0019]

According to the present invention, since the first layer of the copper foil with insulating adhesive material has low flowability, an insulating layer can be secured between the copper foil and the metal plate sandwiching the insulating adhesive material, and the second layer can be secured. Has a high flow property, so that it is possible to fill the internal gap of the hole opened in the metal plate. Further, by adopting such a two-layer structure, it is possible to reduce the film thickness of the insulating adhesive material, and it can be expected to improve heat dissipation. Furthermore, even if the thickness of the insulating adhesive material is small, the insulation reliability is ensured and the hole filling property is high. Therefore, the adhesive sheet can be applied in two or more layers. In that case, in addition to the effect of the two-layer coating described above, coating film defects such as voids and craters can be further prevented.

[0020]

【Example】

Example 1 (1) Varnish A (the composition is shown below) as a first layer on a 35 μm copper foil so that the film thickness after drying would be 70 μm.
And then dried at 150 ° C. for 10 minutes, and a second layer having a total thickness of 140 after the first layer and the second layer is dried.
After coating with varnish A to a thickness of 10 μm,
It is minutely dried to produce a copper foil with an insulating adhesive material.・ Epoxy resin Epicoat 828 (Yukaka Shell Co., Ltd., trade name) ・ ・ ・ 60 parts by weight ・ Flexible agent phenoxy resin ・ ・ ・ ・ ・ ・ ・ ・・ 20 parts by weight Acrylic rubber ・ ・ ・ ・ 20 parts by weight ・ Curing agent Phenol novolac ・ ・ ・ ・・ ・ ・ ・ 30 parts by weight ・ Curing accelerator 2PZ-CN (manufactured by Shikoku Kasei Co., Ltd.) ・ 0.5 parts by weight ・ Silane coupling agent NUC-A187 (manufactured by Nippon Unicar Co., Ltd., Product name) 2 parts by weight Inorganic filler Alumina 130 parts by weight (2) Aluminum with a thickness of 0.3 mm After punching holes in the plate at predetermined positions, the surface is polished to remove burrs and Is subjected to silane coupling treatment. (3) A copper foil with an insulating adhesive material and the aluminum plate prepared in (2) are laminated by pressing. (4) A through hole is formed by drilling a tip hole of the amyl plate with a drill. (5) The through holes are plated to connect the circuits on both sides. (6) A pattern is formed by etching.

Example 2 (1) As the first layer of the release film, the film thickness after drying was 7
After applying Varnish A to 0 μm, 1 at 150 ° C
Dry for 0 minutes, and apply a varnish A as a second layer on the first and second layers so that the combined thickness of the first and second layers is 140 μm, and then dry at 110 ° C. for 10 minutes for insulation adhesion. Make the material. (2) After punching holes in predetermined positions of an aluminum plate having a thickness of 0.3 mm with a punch, the surface is polished to remove burrs, and the surface is subjected to silane coupling treatment. (3) The insulating adhesive material and the aluminum plate prepared in (2) are laminated by pressing. (4) A through hole is formed by drilling a tip hole of the amyl plate with a drill. (5) The through hole portion and the conductor circuit are formed by plating.

Comparative Example 1 A copper foil having a thickness of 35 μm and a thickness of 70 μm after being dried as a first layer
After coating the varnish A so as to have a thickness of m, it is dried at 110 ° C. for 10 minutes to produce a copper foil with an insulating adhesive material, which is the same as in Example 1.

The thermal resistance, withstand voltage, and peel strength of the metal core wiring board thus prepared were measured, and the results are shown in Table 1. For the thermal resistance, the metal core wiring board created on the heat dissipation block is placed, and N is used as a heat source on the copper foil.
Solder a PN type transistor, connect the positive pole of the DC power supply to the collector of the transistor and the negative pole of the emitter, fix the thermocouple at two temperature measurement points of the transistor and the heat radiation block, and connect the DC power source to the base of the transistor. The pressure applied was applied, the temperature at two locations and the supplied power were measured, and the quotient of the temperature difference at the two locations and the power was determined as the thermal resistance. Withstanding voltage is PCT treatment (120 ° C, 2 atm), 96
After a lapse of time, with the film thickness of the insulating layer being 150 μm, an AC voltage was applied between the upper and lower circuits at a rate of 0 V to 100 V per second to obtain a voltage at which dielectric breakdown occurred. The peel strength is
Based on JIS C 6481, the pulling force when the copper foil formed to have a width of 10 mm was peeled off from the substrate at a pulling speed of 50 mm / min at an angle of 90 degrees was measured.

[0024]

[Table 1]

[0025]

As described above, according to the present invention,
It is possible to fill holes and form an insulating adhesive layer at once.
It was possible to provide a method for efficiently producing a metal core wiring board having excellent wiring density.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

[Explanation of symbols]

 1. Metal core 2. Insulating adhesive material 3. Copper pattern 4. Copper plating part

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C09D 5/25 PQY C09J 9/00 JBC H05K 1/03 H 7511-4E 3/40 E 7511-4E 3/42 B 7511-4E

Claims (4)

[Claims] 1. A method of manufacturing a metal core double-sided wiring board, comprising the following steps. a. Step of producing a copper foil with an insulating adhesive material formed by arranging a coating film on the copper foil b. Process of punching a metal plate having a thickness of 0.1 mm to 2 mm c. Copper foil with insulating adhesive material obtained in step a, and step b
Step of heating and pressing the perforated metal plate obtained in step 1 to perform laminated integration. D. A step of making a hole in a portion where interlayer connection is performed e. Process of electrically connecting both sides of the circuit by plating and conductive paste f. Step of forming a circuit by etching g. A step of bending and / or drawing the substrate as necessary 2. A copper foil with an insulating adhesive material is applied to the copper foil, the insulating adhesive material is heated and cured in a B or C stage state, and then the insulating adhesive material is applied onto the copper foil, and the A or B stage is applied. The metal core double-sided wiring board according to claim 1, wherein the metal core double-sided wiring board is produced by heating and curing to a state. 3. A metal core wiring board according to claim 1, which is produced by applying an insulating adhesive material on a single-sided copper-clad laminate and heating and curing the same in an A or B stage state. Production method. 4. The insulating adhesive material comprises epoxy resin, rubber, and a high thermal conductive inorganic filler.
Alternatively, the method for manufacturing the metal core wiring board according to 3 above.