JPH0350892A - Manufacture of conductive metal-foil-clad multilayer circuit board - Google Patents

Abstract

PURPOSE:To unite a conductive metal foil to a mold-releasing film without producing wrinkles or the like in the conductive metal foil by a method wherein the mold-releasing film is arranged and installed in advance on the outer surface of the conductive metal foil and they are pressurized and molded. CONSTITUTION:Materials are prepared by pasting mold-releasing films, e.g. polyethylene terephthalate films 6, on glossy faces (non-bonding faces) of conductive metal foils, e.g. copper foils 3. Then, copper foils 3a, provided with a mold- releasing film, which have been prepared in the same manner are piled up, via prepreg layers 2, on main faces of a prepared inner-layer circuit board 1a, and are positioned by utilizing guide holes in the inner-layer circuit board 1a; a required heating, pressurization and molding process is executed to obtain a copper-clad multilayer circuit board 4a. The surface of the copper foils 3 is covered with mold-releasing films 6; the copper foils 3a provided with the mold-releasing film are constituted, fixed and reinforced; consequently, it is possible to prevent wirnkles or the like from being produced in the heating, pressurization and molding process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to an improvement in a method for manufacturing a conductive metal foil-clad multilayer circuit board.

(Prior Art) For example, in response to the miniaturization of electronic equipment, efforts are being made to make the printed circuit boards used in these electronic equipment smaller and to increase the density of circuit patterns. That is, in printed circuit boards, the number of layers of circuit patterns (multilayer circuit boards) is increasing.

However, this type of multilayer circuit board is generally manufactured as follows. In other words, prepare an insulating support plate with conductive metal foil such as copper foil laminated on one or both sides,
Required guide holes are bored in the insulating support plate laminated with the metal foil, and the metal foil is photo-etched to form a required circuit pattern, thereby obtaining an inner layer circuit board. Next, as shown in cross section in FIG. 4, the number of inner layer circuits (la) or this inner layer circuit board are sequentially positioned and assembled together via prepreg layers, and then heated.

A metal foil, such as a copper foil 3, is overlaid on the main surface of the pressure-formed multilayer inner layer circuit board (1b) with the prepreg layer 2 in between, and the pressure-formed copper foil is A foil-covered multilayer circuit board 4 is first obtained. In addition, in the figure, 5 indicates an inner layer circuit pattern. After performing the required through-hole drilling process on the copper foil-covered multilayer circuit board 4 obtained above, the copper foil 3 disposed on the outer surface is subjected to a photoetching process to form a required circuit pattern. Furthermore, a required through-hole connection layer is provided in the drilled through-holes by chemical plating or the like to obtain a desired multilayer circuit board.

(Problems to be Solved by the Invention) However, the following disadvantages are often found in the method for manufacturing multilayer circuit boards covered with conductive metal foil, such as copper foil. That is, when the copper foil 3 is overlaid on the main surface of the inner layer circuit board 1a (lb) via the prepreg layer 2 and heated and pressure-molded, the resin flowing out from the end surface of the prepreg layer 2 is transferred to the outer surface of the copper foil 3. First, there is the problem that the circuit pattern formed by photoetching the copper foil 3 may short-circuit. Furthermore, the pressure forming process tends to cause wrinkles in the copper foil 3, making it difficult to form fine circuit patterns, and exposing the copper foil 3.
There is a problem in that the surface is easily oxidized (rust occurs) due to operator's fingerprints, etc., and excessive care is required when handling it.

[Structure of the Invention] (Means for Solving the Problems) The present invention has been made in response to the above-mentioned circumstances, and consists of stacking copper foil on the main surface of an inner layer circuit board via a prepreg layer, and forming the copper foil under pressure. The method for manufacturing a multilayer circuit board covered with conductive metal foil is characterized in that a releasable film is disposed on the outer surface of the conductive metal foil.

(Function) In the above means, a releasable film is disposed in advance on the outer surface (non-bonding surface) of the conductive metal foil that is laminated and integrated with the inner layer circuit board via the bulging layer. Since the conductive metal foil is press-formed using the same method, the conductive metal foil can be integrated without wrinkles or the like. Furthermore, during the manufacturing process, the releasable film has a protective effect against staining, etc., and can be easily peeled off and removed when forming a circuit pattern on the conductive metal foil.

(Example) The present invention will be described in detail below with reference to FIGS. 1 to 3. 1 to 3 are cross-sectional views schematically showing aspects of each step of the manufacturing method according to the present invention. First, an insulating support plate with conductive metal foil such as copper foil pasted on both sides is prepared, and required guide holes are bored in the insulating support plate with the copper foil pasted on, while a photo is inserted into the copper foil. An inner layer circuit board having a desired circuit pattern formed by etching is obtained. On the other hand, the shiny surface (non-pipe surface) of the conductive metal foil, such as the copper foil 3...usually the back surface (the surface of the pipe to be contacted) is oxidized to form a non-glossy surface...is coated with a release film such as polyethylene terephthalate. A film 6 pasted together with an adhesive or the like is prepared.

Next, as shown in FIG.
a) Lay the above-prepared copper foil 3a with a releasable film on the main surface via the prepreg layer 2, position it using the guide hole of the inner layer circuit board (la), and apply the necessary heating. By performing pressure molding, a copper foil-clad multilayer circuit board 4a as shown in cross section in FIG. 3 is obtained.

The steel foil-clad multilayer circuit board 4a obtained above is heated,
During the pressure molding process, the surface of the copper foil 3 becomes a releasable film 6.
For example, even if the resin flows out from the prepreg layer 2, it will not be attached to the surface of the copper foil 3 itself. In addition, the surface of the copper foil 3 is covered with a releasable film 6 to form a releasable film-coated copper foil 3a (composite), which is fixed and reinforced, so wrinkles may occur during the heating and pressure forming process. It is also prevented that Thus, this copper foil-covered multilayer circuit board 4a is obtained by peeling off the releasable film 6, drilling the required through holes, and then photo-etching the copper foil 3 to form a desired circuit pattern. A desired multilayer circuit board can be obtained by further providing a required through-hole connection layer on the drilled through-holes by chemical plating or the like.

In addition, although the above example shows an example of manufacturing a copper foil-clad multilayer board by means of positioning using guide pins (pin lamination method), it is also possible to manufacture a copper foil-clad multilayer board by means of positioning without using guide pins (mass lamination method). A board may also be manufactured. Further, it is also possible to manufacture a copper foil-clad multilayer film having a structure in which a plurality of inner layer circuit boards are built-in. Furthermore, although copper foil is exemplified above as the conductive metal foil, it is not limited to copper foil, and may be, for example, aluminum foil.

[Effects of the Invention] As described above, according to the method for manufacturing a conductive metal foil-covered multilayer circuit board according to the present invention, a conductive metal foil with a peelable film is placed on the main surface of an inner layer circuit board via a prepreg layer. are layered, heated, and pressure-molded.

Even if the resin flows out from the end face of the prepreg layer due to this heating and pressure molding, it will not directly adhere to the conductive metal foil surface, so the peelable film is peeled off and the conductive metal foil is photoetched. This completely eliminates the problem of short circuits and disconnections occurring in circuit patterns. Furthermore, since wrinkles are prevented from forming on the conductive metal foil during heating and pressure forming, it is possible to form fine circuit patterns. Preservation management is also easy because it prevents oxidation (growth of mackerel) caused by the fingerprints of workers.

[Brief explanation of drawings]

1 to 3 schematically show aspects of each step of the manufacturing method according to the present invention, FIG. 1 is a cross-sectional view of the structure of the conductive metal foil with a peelable film, and FIG. inner layer circuit board,
A cross-sectional view showing a state in which a prepreg layer and a conductive metal foil with a peelable film are superimposed, FIG. 3 is a cross-sectional view of the manufactured conductive metal foil-clad multilayer board, and FIGS. 4 and 5 are conventional manufacturing methods. The aspects of each step in the method are schematically shown. Fig. 4 is a cross-sectional view showing a state in which the inner layer circuit board, prepreg layer and conductive metal foil are stacked, and Fig. 5 is a cross-sectional view showing the state in which the inner layer circuit board, prepreg layer and conductive metal foil are stacked. FIG. 2 is a cross-sectional view of a foil-clad multilayer board. la, lb... Inner layer circuit board 2... Prepreg layer 3... Conductive metal foil 3a... Conductive with peelable film Conductive metal foil 4.4a... Conductive metal foil-covered multilayer board 5...
・・・・・・Inner layer circuit pattern 6・・・・・・・・・
peelable film

Claims (1)

[Scope of Claims] A method for manufacturing a conductive metal foil-clad multilayer circuit board, in which a copper foil is laminated on the main surface of an inner layer circuit board via a prepreg layer and then pressure-formed, comprising: an outer surface of the conductive metal foil; A method for producing a multilayer circuit board covered with conductive metal foil, comprising disposing a releasable film thereon.