JPH02143849A - Metallic foil plated laminated sheet and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a metallic foil plated laminated sheet for printed wiring board enabling high-speed transmission such as high-frequency device, by a method wherein an adhesive agent layer of the metallic foil plated laminated sheet is made into a composite adhesive layer by providing outside adhesive agent layers on both sides of an intermediate adhesive agent layer within which fine bubbles are included. CONSTITUTION:The title laminated sheet is formed of an insulation board 1 becoming a base, a metallic foil 2 forming a circuit and an adhesive agent layer sticking both of them together. Then the adhesive agent layer is formed of a composite adhesive agent layer of outside adhesive agent layers 3, which are on both the sides 3 and not containing bubbles, and an intermediate adhesive agent layer 5 within which fine bubbles are included. A copper foil plated laminated sheet prepared in this manner is treated by a hot press for 30-90min. under terms of a heating temperature range of 180-200 deg.C and pressure of 30-50kg/cm<2>. Since the outside adhesive agent layer 3 and intermediate adhesive agent layer 5 are identical with each other in a resin composition, an interface of both the adhesive agent layers is almost welded at the time when the same is made into a C stage (cured). Since foaming progresses based on the core of a foaming agent, the foaming progresses in only the intermediate adhesive agent layer 5 comprised of an adhesive agent B and it does not happen that the bubbles do not come into contact with adhesive interface with the insulation board 1 or the metallic foil 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention is a printed layout! fA This relates to a temporary metal foil clad laminate and a method for manufacturing the same.

(Prior art and problems to be solved by the invention) - The basic structure of a printed wiring board in a film is as shown in the cross-sectional view in FIG. A circuit pattern is formed by etching or the like using laminated boards bonded together, and copper foil, which has good conductivity, is mainly used as the metal foil 2.

In a printed wiring board having such a configuration, the characteristics of the insulating layer 8 made of the insulating substrate 1 and the insulating adhesive layer 7 often directly become the physical characteristics of the printed wiring board. For example, the typical characteristics of ceramic wiring boards, such as hardness, high insulation, and high dimensional stability, are largely due to the characteristics of the base ceramic itself. Furthermore, there are an increasing number of modern issues related to the functions of electronic components installed, such as heat dissipation issues, dimensional accuracy, signal transmission speed, etc. to ensure that the functions of electronic components are not impaired. It can be said that it is a characteristic given to .

Recently, devices that operate in high frequency bands have become commonplace, and signal transmission delays due to wiring are becoming a problem for printed wiring boards as well. In other words, a wiring board for high-speed transmission is required.

In the printed wiring board having the general structure described above, the signal transmission speed is closely related to the dielectric constant of the insulating layer 8 made up of the insulating substrate 1 supporting the conductor circuit and the insulating adhesive layer 7. Therefore, fluororesin, which has a low dielectric constant, is used as an insulating substrate for wiring boards for high-speed transmission. However, in addition to being expensive, fluororesin requires high processing temperatures.
In addition, due to problems such as poor adhesion with metals, it has not been widely used as a film, and is only used in industrial hard wiring boards and multilayer wiring boards, including large computers. However, the application is limited to the field of

As is well known, the dielectric constant is lowest in the vacuum rod-like space.
Next, since it is air, there is a method of lowering the dielectric constant by foaming an insulator such as polyester resin.

However, in order to lower the dielectric constant through foaming, it is difficult to expect much unless the foaming rate is appropriate for the solid content of the material, and in addition, evenly and sufficiently foaming is required on an insulating substrate made of a thin resin layer. It is difficult to do so.

Therefore, instead of generating bubbles by foaming, a method has been reported in which hollow spheres made of glass or other materials are dispersed in the insulating layer, an example of which is shown in FIG. The same parts as in FIG. 2 are indicated by the same reference numerals, and the adhesive layer 9 includes hollow spheres 10 such as glass.

In such a structure, the insulating layer 11 inevitably becomes thick, and tends to be hard and brittle in terms of strength. Furthermore, due to problems with the dispersibility of the hollow spheres, it is necessary to add a dispersion contributing agent such as a silane coupling agent, which forces some characteristics such as moisture resistance to be sacrificed.

In addition, as mentioned above, insulating substrates made of foam are weak in strength, and it is difficult to manufacture laminates using them. If a laminate is formed and the adhesive layer is foamed at the same time as this lamination, manufacturing difficulties will be eliminated, so a laminate with a structure in which the adhesive layer is foamed and manufactured in this way has also been proposed. . FIG. 4 is a cross-sectional view of such a laminate, where 12 is an adhesive layer in which air bubbles 13 are mixed;
The same parts as in FIG. 3 are indicated by the same reference numerals. However, with this type of structure, air bubbles also occur in the adhesive layer where it contacts the insulating substrate and metal foil, which weakens the adhesive strength, forcing the foaming degree to be reduced and achieving the desired result. It becomes impossible to obtain a low dielectric constant.

(Means and effects for solving the problems) The present invention has been made to solve the above-mentioned problems, and has the same workability and cost as the conventional basic structure, and is suitable for use in high-frequency devices, etc. The present invention provides a metal foil-clad laminate for printed wiring boards that enables high-speed transmission, and a method for manufacturing the same.

That is, in a metal foil laminate formed by laminating an insulating substrate and a metal foil with an adhesive layer interposed therebetween, the adhesive layer is
To provide a metal foil-clad laminate having a composite adhesive layer structure in which outer adhesive layers containing no air bubbles are provided on both sides of an intermediate adhesive layer containing fine air bubbles.

By forming the composite adhesive layer as described above, the parts of the composite adhesive layer that contact the insulating substrate and metal foil do not contain air bubbles, so sufficient adhesive strength can be obtained, and the middle part contains air bubbles. Therefore, an insulating layer with the desired low dielectric constant can be obtained.

In addition, as a method for producing a metal foil-clad laminate having the above structure, the opposing surfaces of the insulating substrate and the metal foil are each coated with an adhesive that does not contain a foaming agent, and the solvent in the adhesive is removed by drying. After applying a semi-cured outer adhesive layer that has been B-staged to the extent that it leaves a weak tack to the touch, one of the outer adhesive layers is coated with an adhesive containing a foaming agent. The solvent in the adhesive is dried and removed, and an unfoamed intermediate adhesive layer is installed.Then, the intermediate adhesive layer and the other outer adhesive layer are brought into contact with each other, and the insulating substrate and the metal foil are laminated. After that, the foaming agent in the intermediate adhesive layer is foamed and cured by heating and pressurizing, and at the same time, the outer adhesive layer is also cured. A method of laminating an insulating substrate and a metal foil with a composite adhesive layer comprising an outer adhesive layer is provided.

(Example) Fig. 1 is a cross-sectional view of an example of a metal foil-clad laminate according to the present invention, in which an outer adhesive layer 3 containing no air bubbles on both sides and an intermediate adhesive layer containing a mixture of fine air bubbles 4 are shown. An insulating substrate 1 made of a polyimide film and a metal foil 2 made of copper for forming a circuit pattern are laminated with a composite adhesive layer 6 made of 5 interposed therebetween.

Next, a method for manufacturing the metal foil-clad laminate shown in FIG. 1 above will be explained.

As a base resin, 100 to 150 parts by weight of bisphenol A type liquid epoxy resin (Dowepoxy DER337), 50 to 100 parts by weight of bisphenol A type solid epoxy resin (Dowepoxy DER622) and diluted portion of nitrile rubber (band chemical NBR) MEK (methyl ethyl ketone) 300 to 500 parts by weight of DDS (diaminodiphenylsulfone) and 2E4MZ (2ethyl 4
An adhesive-containing resin is used in which 5 to 100 parts by weight of DCP (methyl imidazole) and DCP (dicumyl peroxide) are each added to the above-mentioned mixed resin. This adhesive will be referred to as adhesive A hereinafter.

Azodicarbonamide is added as a foaming agent to the resin solid content of Adhesive A in an amount of 50-100% by weight and mixed using a roll mill until it is sufficiently dispersed. Further, when the foaming temperature range needs to be adjusted at the time of adding the foaming agent, urea may be added in an amount equivalent to the amount added as a foaming aid for azodicarbonamide. Hereinafter, the foaming agent-containing adhesive in which the foaming agent is sufficiently dispersed and mixed in this manner will be referred to as adhesive B.

An adhesive layer is applied using a bar coater to a thickness of 0.03 to 0.0 mm on the opposite adhesive surfaces of an insulating substrate 1 made of a polyimide film with a thickness of 0.025 mm and a metal foil 2 made of copper as shown in FIG. Apply a uniform coating within a range of .10 mm, and immediately remove the solvent contained in adhesive A from 80 to 100 mm.
A B-staged outer adhesive layer 3 is formed by drying and blowing air at a temperature of .degree. C. to leave a weak tack to the touch.

Furthermore, adhesive B is applied to the outer adhesive layer 3 formed by coating adhesive A on the insulating substrate 1 to a thickness of 0.0 in the same manner as above.
It is coated uniformly in the range of 3 to 0.50 mm, and the solvent contained in adhesive B is quickly dried and removed.

Next, the heating temperature of the heating roll laminator is set to around 160° C., and the adhesive surface of the insulating substrate 1 (polyimide film) and the metal foil 2 (!Ii4 foil) are laminated at a relatively slow speed.

The copper foil-clad laminate produced as described above was heated in a heating press at a temperature of 180 to 200°C and a pressure of 3.
By each treatment of 30 to 90 m1n under the conditions of 0 to 50 kg/c transport 2, the foaming agent blended in adhesive B starts foaming, and at the same time, the curing of adhesives A and B starts, and the pressure is applied. This hinders the connection between adjacent bubbles. Since the outer adhesive layer 3 and the intermediate adhesive layer 5 have the same resin composition, the interface between both adhesive layers is C-staged (
However, since the foaming progresses with the foaming agent as the nucleus, the foaming progresses only in the intermediate adhesive layer 5 made of adhesive B, and the bubbles come into contact with the adhesive interface with the insulating substrate 1 and the metal foil 2. There will be nothing left to do. After a certain point during the pressing process, the pressure changes to higher than the set pressure, indicating that foaming inside the adhesive has started.

The equivalent dielectric constant of the composite adhesive layer in the copper foil-clad laminate produced as described above is
Due to the uniformly dispersed presence of 200 IJ- of air bubbles, the foaming capacity is 1
It was confirmed that it can be reduced by 0 to 20%.

(Effects of the Invention) Metal foil laminates using insulating substrates mixed with foam or spheres are fragile in terms of strength, so it is necessary to increase the thickness. There are some difficulties. Furthermore, those having a structure in which air bubbles are generated in the adhesive layer during lamination processing are extremely easy to manufacture without impairing the basic properties of the adhesive, but have low adhesive strength. In contrast, the laminate of the present invention can reduce the effective dielectric constant without impairing adhesive strength. Moreover,
It is possible to provide a laminate whose cost and workability are comparable to those of conventional basic structures, and which can be passed through wiring boards for high-speed transmission.

[Brief explanation of the drawing]

Fig. 1 is a schematic cross-sectional view of a metal foil-clad laminate according to the present invention, Fig. 2 is a schematic cross-sectional view showing the basic structure of a conventional metal foil-clad laminate, and Fig. 3 shows hollow spheres in the insulating layer. FIG. 4 is a schematic cross-sectional view of a metal foil-clad laminate in which air bubbles are mixed throughout the adhesive layer. 1: Insulating substrate, 2: Metal foil, 3: Outer adhesive layer, 4: Air bubbles, 5: Intermediate adhesive layer, 6: Insulating layer.

Claims (2)

[Claims] 1. In a metal foil-clad laminate consisting of an insulating substrate serving as a base, a metal foil forming a circuit, and an adhesive layer bonding the two, the adhesive layer has an outer adhesive layer on both sides that does not contain air bubbles; A metal foil-clad laminate characterized by consisting of a composite adhesive layer with an intermediate adhesive layer mixed with fine air bubbles. 2. After coating the opposing surfaces of the insulating substrate and the metal foil with an adhesive that does not contain a foaming agent, drying and removing the solvent in the adhesive to form a semi-cured outer adhesive layer, either one of them is coated with an adhesive that does not contain a foaming agent. An adhesive containing a foaming agent is coated on the outer adhesive layer, and the solvent in the adhesive is dried and removed to provide an unfoamed intermediate adhesive layer. The insulating substrate and metal foil are laminated with the outer adhesive layer in contact with each other, and then the foaming agent in the intermediate adhesive layer is foamed and cured by heating and pressing, and the outer adhesive layer is also cured at the same time. , a method for producing a metal foil laminate in which an insulating substrate and metal foil are laminated using a composite adhesive layer consisting of an intermediate adhesive layer mixed with fine air bubbles and outer adhesive layers on both sides without air bubbles.