JPH0471707B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a printed wiring board made of a metal foil/polyimide film laminate and a method for manufacturing the same.
For details, we will introduce easy-to-manufacture, high-precision printed wiring boards that use a specific thermoplastic polyimide as an adhesive for bonding polyimide film and metal foil, and printed wiring boards that are easy to manufacture and highly accurate in shape processing, such as hole punching. Regarding the manufacturing method.

(Background of the Invention) Conventionally, in manufacturing metal foil/polyimide film laminates, thermosetting adhesives such as epoxy resin, thermosetting polyimide resin, and acrylic resin have been used to bond metal foil and polyimide film together. resin is used. These resins are hardly affected by the etching solution for the polyimide film that is the base film, so if a hole or other penetrating portion is required in the laminate, it is necessary to use mechanical means such as a drill or punching press.

However, drilling holes with a drill has disadvantages in that processing accuracy is poor, burrs and smear occur, and the minimum diameter of the hole is limited by the dimensions of the drill that can be used. Punching presses have poor processing accuracy, making it difficult to perform fine and complicated processing, and require the use of molds that are expensive to manufacture. Furthermore, with these methods, it is difficult to remove the resin etc. on the back side of the metal foil and use it as a new conductive part.

(Object of the Invention) The present invention has been made to solve the above-mentioned drawbacks of the prior art, and provides a printed wiring board that is easy to perform shape processing such as hole punching and has high processing accuracy, and a method for manufacturing the same. The purpose is to

As a result of extensive studies to achieve the above object, the inventors of the present invention solved the above problems by using an adhesive that can be etched with an etching solution for base polyimide films as an adhesive for bonding polyimide film and metal foil. We have discovered what can be done and arrived at the present invention.

(Structure of the Invention) That is, the present invention provides the following chemical formula on one or both sides of a polyimide film. A printing characterized in that a conductor circuit is formed through a thermoplastic polyimide adhesive layer represented by the above, and at least a portion of the exposed thermoplastic polyimide adhesive layer and the underlying polyimide film are etched. It is a wiring board.

Furthermore, the present invention also provides the following chemical formula A process of manufacturing a metal foil/polyimide film laminate by bonding metal foil to one or both sides of a polyimide film using thermoplastic polyimide as an adhesive, and a process of forming a conductor circuit by etching the metal foil. This method of manufacturing a printed wiring board is characterized by comprising the steps of: and shaping the thermoplastic polyimide adhesive layer exposed by etching the metal foil and the polyimide film thereunder by etching.

The method for manufacturing a printed wiring board of the present invention will be described below.

First, in the present invention, a metal/polyimide laminate is manufactured by bonding metal foil to one or both sides of a polyimide film using a specific thermoplastic polyimide as an adhesive. For example, a thermoplastic polyimide varnish is applied to one or both of the metal foil and polyimide film, heated to form a thermoplastic polyimide layer, and then a laminate is manufactured by hot pressing, or a laminate is produced between the metal foil and the polyimide film. A thermoplastic polyimide film is sandwiched between the two and hot pressed to produce a metal foil/polyimide film laminate.

The specific thermoplastic polyimide used as the adhesive in the present invention has the following chemical formula as described above.

Since such thermoplastic polyimide can be etched with a common polyimide etching solution, the adhesive layer and the polyimide film can be etched simultaneously in a later step.

Next, a conductor circuit is formed on the metal foil by etching using photolithography in the same manner as in the production of a normal wiring board.

Further, the adhesive layer exposed by the metal foil etching operation and the underlying polyimide film are removed by etching with an etching solution for base polyimide film to perform shape processing such as through-hole processing.

If only the exposed adhesive layer and the desired portion of the underlying polyimide film are to be etched, etching may be performed after etching the metal foil and then masking with a photoresist or the like.

In the present invention, mechanical methods such as a drill and a punching press can of course be used in conjunction with the shape processing.

As described above, in the present invention, the metal surface can be easily exposed on the back side of the metal foil, and the newly exposed metal surface can be used as a new conductive part.

Hereinafter, a detailed explanation will be given based on examples.

Example 1 FIG. 1 is a diagram illustrating a method for manufacturing a double-sided through-hole printed wiring board according to the present invention. This double-sided through-hole printed wiring board is manufactured as follows.

Thermoplastic polyimide varnish is applied to one or both sides of the copper foil 1 and the base polyimide film 3. After heating at 100°C in an oven for 30 minutes to remove the solvent, the temperature is gradually raised to 200°C and heated for 30 minutes to complete imidization. Copper foil 1 is laminated on both sides of the base polyimide film so that the newly formed polyimide adhesive layer 2 is on the inside, and the copper foil 1 and base polyimide film 3 are bonded together by heating to 300°C using a hot press. A copper foil/polyimide film laminate as shown in a is manufactured.

Photoresist is applied to both sides of the obtained laminate and exposed using a photomask. The resist in the area where the copper is to be dissolved is removed, and the copper is removed by an etching operation. Subsequently, the photoresist is removed with a stripping agent to produce a laminate as shown in FIG. 1b.

By etching and removing the polyimide adhesive layer 2 exposed by the copper etching operation and the underlying base polyimide film 3 using a base polyimide etching solution, a through hole A penetrating the laminate is formed as shown in FIG. 1c. It is formed. Thereafter, a double-sided through-hole printed wiring board is completed by a normal through-hole plating process.

Example 2 FIG. 2 shows a printed wiring board according to the present invention,
It is a figure explaining the manufacturing method of the printed wiring board which exposed the back surface of the metal foil layer provided on both surfaces of the base polyimide film. This printed wiring board is manufactured as follows.

The copper foil/polyimide film laminate shown in FIG. 1a is manufactured in the same manner as in Example 1. Photoresist is applied to both sides of the resulting laminate, and different patterns are printed on each side by exposure. After removing the resist in the area where the copper is to be dissolved, the copper is removed by etching and the photoresist is peeled off.

The polyimide adhesive layer 2 exposed by the copper etching operation and the underlying base polyimide film 3 are removed by etching with a base polyimide etching solution. In this way, Figure 2b
Complete a printed wiring board with the back side of the copper foil exposed on one or both sides as shown in .

Note that here, the exposed polyimide adhesive layer 2
When only desired portions of the base polyimide film 3 are to be etched, etching may be carried out after masking the portions that are not desired to be removed with photoresist or the like.

(Effects of the present invention) As described above, according to the present invention, the following effects are achieved.

Since photolithography is used, the minimum diameter of the hole to be opened is the minimum diameter that can be formed by photolithography, making micro-machining and high-precision machining possible. Therefore, no occurrence of burrs, smear, etc. is observed.

Since a photomask is used, the processed shape can be freely designed, and it has good compatibility with the photomask for the pattern in the next process.

In the conventional method, it was difficult to remove the adhesive layer between the metal foil and the resin, but according to the present invention, the metal surface on the back side of the metal foil can also be freely exposed and can be used as a conductive part.

Therefore, the printed wiring board manufacturing method of the present invention is suitable for manufacturing flexible wiring boards and lead frames, through-hole processing of double-sided wiring boards, hole punching of multilayer boards, and various other shapes of printed wiring boards. used.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a double-sided printed wiring board according to an embodiment of the present invention, and FIG.
Figure b shows the state after copper etching, figure c shows the state after polyimide etching, and figure 2 is a cross-sectional view of a double-sided printed wiring board according to another embodiment of the present invention, and figure a shows the state after copper etching. Figure b shows the state after polyimide etching. 1...Metal foil, 2...Thermoplastic polyimide adhesive layer, 3...Base polyimide film, A...Through hole penetration part, B...Newly exposed copper surface.

Claims (1)

[Claims] 1. On one or both sides of the polyimide film,
Chemical formula below A printing characterized in that a conductor circuit is formed through a thermoplastic polyimide adhesive layer represented by the above, and at least a portion of the exposed thermoplastic polyimide adhesive layer and the underlying polyimide film are etched. wiring board. 2 The following chemical formula A process of manufacturing a metal foil/polyimide film laminate by bonding metal foil to one or both sides of a polyimide film using thermoplastic polyimide as an adhesive, and a process of forming a conductor circuit by etching the metal foil. A method for manufacturing a printed wiring board, comprising the steps of: - processing the shape of the thermoplastic polyimide adhesive layer exposed by etching the metal foil and the polyimide film thereunder by etching.