JPH0758441A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To provide the easily manufacturing method of high density printed- wiring board. CONSTITUTION:The title manufacturing method of printed-wiring board is composed of the following five steps i.e., the first step (A) of forming an etching resist 3 on a copper foil surface of a base material whereon a copper foil 1 is bonded onto one surface of a polyimide film 2, the second step (B) of etching the etching resist 3 to form a conductor circuit, the third step (C) of removing the etching resist 3 to roughen the remaining copper surface, the fourth step (D) of lamination-molding the printed-wiring board together with an epoxy prepreg and the fifth step (E) of removing the poly-imide film 2 using an alkali solusion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board, particularly PGA (pin grid array), MCM (multi.
The present invention relates to a method for manufacturing a printed wiring board used in the electronic field such as a chip module).

[0002]

2. Description of the Related Art Conventionally, a printed wiring board is manufactured by a manufacturing method (a) a subtractive method for obtaining a desired circuit by etching a copper foil of a copper foil laminated board.
There are three methods: an additive method for electroless copper plating on the surface of an insulating plate to obtain a desired circuit, and (c) a transfer method for forming a desired conductor circuit on a smooth metal surface and transferring it to the insulating plate. Broadly divided.

Among them, the transfer method of (c) is (a)
3 is superior in reliability to the subtractive method as compared with the subtractive method, and is also a technology that has been attracting attention in recent years because the number of manufacturing steps is smaller than that in the additive method (b). As shown in
Using a conductive material such as a stainless steel plate (12),
Forming a thin film copper (11) by electroplating, then forming a plating resist (13) and forming a conductor circuit by plating, then removing the plating resist (13) and roughening the copper surface, Laminate molding is performed with semi-cured resin such as prepreg. When the stainless steel plate (12) is separated from this state, one side is entirely covered with copper, and the entire copper surface is etched to expose the conductor circuit underneath. It is manufactured based on various processes such as.

[0004]

However, the following problems occur based on the above-mentioned transfer method. (A) It is necessary to etch the copper covering the entire plate in the processes shown in FIGS. 3A to 3D, that is, in the process of exposing the conductor circuit after transfer to the insulating plate, and the conductor circuit below is also required. Since it is copper, it is simultaneously etched. (B) It is necessary to perform copper plating twice on a conductive material, such as performing thin film copper plating and further forming a conductor circuit by plating after forming a plating resist, which requires a long manufacturing process and high cost. It has become. (C) Since the conductor circuit is formed by plating, variations in the plating thickness may occur, resulting in a difference in the resistance value of the conductor.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a method for manufacturing a printed wiring board, which allows a high-density printed wiring board to be manufactured easily and simply. For the purpose, the above-mentioned problems are (A) a step of forming an etching resist on a copper foil surface of a base material in which a copper foil is adhesively processed on one surface of a polyimide film, (B)
Etching and forming a conductor circuit,
(C) removing the etching resist and roughening the remaining copper surface, (D) laminating with epoxy prepreg, and (E) removing the polyimide film with an alkaline solution. it can. Hereinafter, the present invention will be described in detail with reference to FIG.

As the base material, a film having a coefficient of thermal expansion similar to that of the copper foil and being dissolved in an alkaline solution in the final step, for example, a polyimide film laminated with the copper foil is suitable. , Mitsui Toatsu Chemicals, Inc.
Made by Neoflex Series is recommended. The thickness of the polyimide film (2) is preferably 13 to 50 μm. Further, the thickness of the copper foil (1) is preferably 9 to 70 μm, but 18 μm, 35 μm and 70 μm are general specifications. When trying to obtain a high-density pattern, copper foil (1)
The thickness of the polyimide film (2) is preferably 9 to 18 μm and the thickness of the polyimide film (2) is preferably 13 to 25 μm, considering that the polyimide film (2) is also dissolved and removed later.

If the thickness of the copper foil (1) is less than the lower limit, it is difficult to obtain, and if it exceeds the upper limit, etching time becomes long and it becomes difficult to form a fine circuit pattern, which is not preferable. Regarding the thickness of the polyimide film (2), if it exceeds the upper limit, more time is required to remove it with an alkaline solution in the final step, and if it does not reach the lower limit, it is unpreferable and difficult to handle, which is not preferable.

As the etching resist (3), a conventionally known photosensitive resin, for example, an ultraviolet curable resin containing an acrylic resin as a main component can be applied, and a liquid one or a filmed one can be used.

As an etching solution used for forming a conductor circuit by performing etching, a ferric chloride-based etching solution, a cupric chloride-based etching solution, a sulfuric acid / hydrogen peroxide-based etching solution, etc. can be used. A more known etching solution can be used.

The reason why the etching resist (3) is removed and the remaining copper surface is roughened to form a roughening treatment layer is to improve the adhesion between the copper surface and an epoxy prepreg described later. Examples of means for blackening include blackening processing,
A method such as chemical copper deposition can be applied.

As the epoxy prepreg, a glass cloth impregnated with an epoxy resin and dried can be applied. The conditions for laminating and molding may be such that the epoxy resin can be sufficiently cured, and a pressure of about 5 is generally applied. ~ 60kgf /
cm ² , temperature of 150 to 200 ° C., time of 15 minutes or more is desirable, especially when a vacuum press is used, the pressure is 5 to 1
0 kgf / cm ² is sufficient, and low pressure causes less strain,
Higher precision molding is possible. If the pressure, temperature, and time are less than the lower limits, the epoxy resin will be insufficiently cured,
Insulating properties and heat resistance tend to deteriorate, which is not preferable. Further, if the pressure exceeds the upper limit, strain is likely to occur, and if the temperature exceeds the upper limit, the epoxy resin is likely to be thermally decomposed, which is not preferable.

Any alkaline solution may be used as long as it dissolves and removes the polyimide film (2) to expose the conductor circuit. For example, water and ethyl alcohol, n-purpyru alcohol, isopropyl alcohol, etc. A mixture of a lower alcohol and a hydroxide of an alkali metal such as potassium hydroxide or sodium hydroxide can be applied. In addition, ethylenediamine and hydrazine may be appropriately added.

[0013]

As described above, in the present invention, the polyimide covering the entire plate needs to be removed when the conductor circuit is exposed after the processes shown in FIGS. 1A to 1C, that is, after the transfer to the insulating plate. Since the alkaline solution used does not attack the copper, which is the conductor circuit, the range of processing conditions can be widened and the reliability can be improved.

Further, in the case of the present invention in which a copper foil is adhered to a polyimide film to start a substrate, a conductor circuit is formed by etching from a constant copper thickness as compared with a method using a plating resist, so that the conductor thickness is They are uniform, and therefore there is no difference in the resistance value of the conductor.

[0015]

EXAMPLES The present invention will be described in detail below based on examples. Example 1 Preparation of Alkaline Solution 80 parts of ethyl alcohol, 20 parts of water, 1 part of potassium hydroxide
An alkaline solution (A) consisting of 0 part and 4 parts of hydrazine (parts represent parts by weight) was obtained. Manufacture of printed wiring board A single-sided substrate for flexible printed wiring boards (NEX-120R manufactured by Mitsui Toatsu Chemicals, Inc.) in which a copper foil having a thickness of 18 µm is bonded to a polyimide film having a thickness of 25 µm is a UV-curable dry film An etching resist was formed using a resist (HS-930, manufactured by Hitachi Chemical Co., Ltd.). Then, etching is performed with an aqueous solution containing cupric chloride as a main component to form a desired conductive circuit, the etching resist is removed, and then the copper surface is blackened (Shipley Far East Co., Ltd., Probond )did. Then, with the epoxy prepreg, pressure 10kgf /
After laminating and integrating under conditions of cm ² , temperature 170 ° C., time 15 minutes, this was immersed in an alkaline solution (A) to dissolve and remove the polyimide film to obtain a printed wiring board (A).

Example 2 Preparation of Alkaline Solution An alkaline solution (B) consisting of 30 parts of ethylenediamine, 20 parts of potassium hydroxide and 50 parts of hydrazine (parts represent parts by weight) was obtained. Manufacturing of printed wiring board Single-sided substrate for flexible printed wiring board (NEX-110R, manufactured by Mitsui Toatsu Chemicals, Inc.) in which a copper foil having a thickness of 35 µm is adhered to a polyimide film having a thickness of 25 µm.
An ultraviolet-curable dry film resist (AQ4048 manufactured by Asahi Kasei Kogyo Co., Ltd.) was used as an etching resist. Then, etching is performed with an aqueous solution containing ferric chloride as a main component to form a desired conductive circuit, the etching resist is removed, and then the copper surface is blackened (Mccubond, manufactured by Japan McDurmit Co., Ltd.). did. Then, the epoxy prepreg and the epoxy prepreg were laminated and molded under the same conditions as in the example, and integrated, and then this was immersed in an alkaline solution (B) to dissolve and remove the polyimide film to obtain a printed wiring board (B).

Example 3 Preparation of Alkaline Solution An alkaline solution (C) consisting of 80 parts of ethyl alcohol, 20 parts of water and 10 parts of sodium hydroxide (parts represent parts by weight) was obtained. Manufacture of Printed Wiring Board After laminating and integrating in the same manner as in Example 1, this was immersed in an alkaline solution (C) to dissolve and remove the polyimide film to obtain a printed wiring board (C).

[0018]

According to the present invention, in a conventional method for producing a printed wiring board by a transfer method, a film which can be easily removed later, for example, a polyimide film with a copper foil is used as a support for a conductor. It is possible to significantly reduce the manufacturing process such as the removal of the plating process.

Furthermore, since the printed wiring board obtained by the manufacturing method of the present invention is filled with resin between the conductors, it has excellent insulation properties and, as shown in FIG. 2, three sides of the conductor cross section are fixed with resin. Therefore, it is highly reliable. Therefore, it is effective for manufacturing a high-density wiring board having a narrow line width and a narrow line interval.

[Brief description of drawings]

FIG. 1 is a sectional view of a step-by-step configuration of a manufacturing method of the present invention.

FIG. 2 is a sectional view showing the configuration of a printed wiring board obtained by the manufacturing method of the present invention.

FIG. 3 is a sectional view of a structure of each step of a conventional transfer method.

[Explanation of symbols]

 1 Copper Foil 2 Polyimide Film 3 Etching Resist 4 Roughening Layer 5 Epoxy Resin 11 Thin Film Copper 12 Stainless Steel Plate 13 Plating Resist 14 Copper Plating

Claims (1)

[Claims] 1. A method for manufacturing a printed wiring board, which is based on the following steps (A) to (E). (A) A step of forming an etching resist on the copper foil surface of a base material in which a copper foil is bonded and processed on one side of a polyimide film, (B) a step of forming a conductor circuit by etching, and (C) removing the etching resist. Then, a step of roughening the remaining copper surface, (D) a step of laminating with an epoxy prepreg, and (E) a step of removing the polyimide film with an alkaline solution.