JPH04346490A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To prevent the imperfect processing of a printed wiring board by a die from occurring at a boundary part between the rigid structure part and the flexible structure part of the printed wiring board possessed of the rigid structure part and the flexible structure part formed into one piece with injection molding resin and to protect a circuit pattern against disconnection caused by the excessive pressure of molten resin at injection molding. CONSTITUTION:A film 1 is inserted between a die 2a provided with a buffer material 5 installed at a prescribed position and a die 2b cutting-processed as deep as the prescribed thickness of a film 1 and a resin board 3, and then the dies 2a and 2b are clamped. The cutoff or the scuffing of the film 1 caused by imperfect processing at the end 7 of the die 2b can be prevented by the buffer material 5. Thereafter, the pressure of the molten resin is absorbed and relaxed by the buffer material 5 when molten resin is injection-molded, whereby a printed board where the film 1 and a resin board 3 are formed into one piece and a circuit pattern is protected against disconnection can be obtained.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method of manufacturing a printed wiring board having both a hard rigid structural part integrated with injection molded resin and a flexible flexible structural part in the form of a film. The present invention is characterized by a method of preventing disconnection of the circuit pattern at the boundary between the structure and the flexible structure.

0002

2. Description of the Related Art As a method for manufacturing a printed wiring board in which a film on which a circuit pattern is formed is integrated at the same time as resin molding, a planar mold 2a is used as shown in FIG.
A mold 2b is used, in which a recess 8 for placing a flexible film with a circuit pattern formed thereon and a recess 9 recessed further downward from the bottom of the recess 8 for resin molding are pre-cut. This is done by That is, with the surface of the film 1 in contact with the mold 2a and the end of the film 1 being held between the recess 8 of the mold 2b (FIG. 2(b)), the resin 3 welded to the recess 9 is As shown in FIG. 5, the film 1 is injected and cured (FIG. 5(c)), forming a rigid rigid structure where the film 1 is integrated with the resin substrate 3, and a flexible film that is not integrated with the resin substrate 3. A printed wiring board 4 having a flexible structure portion that remains as 1 is formed.

0003

However, in such a printed wiring board, if the surface processing of the core surface and cavity surface of the mold is poor, the film 1 is inserted into the molds 2a and 2b, When sandwiching the film 1, galling or cutting occurs in the film 1 due to the edge 7 at the boundary between the recess 8 and the recess 9 of the mold 2b. In addition, since one end of the film 1 is sandwiched and fixed between the molds 2a and 2b, the pressure of the molten resin 3 deforms the film 1 near the end 7 and causes wrinkles, which in severe cases can lead to circuit breakage. Sometimes.

0004

[Means for Solving the Problems] In order to solve the above problems, the method for manufacturing a printed wiring board of the present invention includes manufacturing a flexible film having a predetermined circuit pattern formed on at least the surface thereof, the surface of which is an inner surface of a mold. When a resin is injected into the back side of the film and cured to form a printed wiring board in which a resin substrate is integrally bonded to the back side of the film, the film surface is placed in a mold so as to be in contact with A cushioning material is arranged at a position facing the tip of the resin substrate on the inner surface of the mold in contact with the resin substrate.

[0005]

[Operation] According to this method, the boundary between the rigid structure and the flexible structure of the film can be cut due to defects in mold processing when inserting and holding the film, or due to the pressure of molten resin when molding the resin substrate. The excessive force that causes deformation and wrinkles can be absorbed by the cushioning material provided in the mold on the surface side of the film.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1(a), a mold 2a faces an end 7 of a boundary between a recess 8 and a recess 9 of a mold 2b which has been cut into a shape similar to that of a conventional mold, and has a circuit pattern formed thereon. A recessed portion having a semicircular cross section is formed in the portion that contacts the film 1, and the recessed portion is filled with a heat-resistant cushioning material 5 such as urethane rubber, silicone rubber, or synthetic rubber.

Now, in the manufacturing process of making a printed wiring board, a film 1 is placed in a mold 2 as shown in FIG.
Even if there is a risk of damage to the film 1 due to poor processing accuracy of the end 7 of the mold 2b and excessive force is applied when inserting it into the molds 2b and 2b, the cushioning material 5 prevents damage. can do. In addition, when injecting molten resin into the recess 9 to obtain the resin substrate 3 integrated with the film 1 (FIG. 1(c)), the edge 7 at the boundary between the rigid structure and the flexible structure
By absorbing and relieving the excess pressure of the molten resin that causes deformation and wrinkles of the film 1 in the vicinity, the circuit pattern can be prevented from breaking, and the printed wiring board shown in FIG. 2 can be obtained. . At this time, the cushioning material 5 is
If the shape is slightly convex from the surface of a, it is possible to more effectively prevent the occurrence of burrs during molding.

The buffer material 5 adheres to the surface of the film 1 during the molding process and remains adhered to the surface after molding, thereby obtaining the printed wiring board 4 shown in FIG. 3. This printed wiring board 4 can effectively absorb and disperse stress caused by bending of the flexible structure part by the attached cushioning material 5, and can prevent cracks and disconnections in the circuit pattern. The cushioning material 5 at this time can be prepared by applying a conventionally known adhesive material such as vinyl acetate, acrylic, or synthetic rubber resin to the surface in advance, or applying heat and pressure during molding or heat treatment after molding. A hardening thermosetting resin adhesive may be applied to the surface.

Although FIG. 1 shows a cushioning material having a circular cross section, the shape is not limited to this, and any shape such as an ellipse or a polygon may be used.

0010

As described above, according to the present invention, in the molding process of conventional rigid/flexible printed wiring boards, a cushioning material is provided to alleviate defects in mold processing accuracy and excessive pressure caused by molding resin. By installing this, it is possible to easily prevent cracks and disconnections in the circuit pattern during molding.

[Brief explanation of drawings]

FIG. 1: (a) A cross-sectional view of a main part of a mold used for manufacturing a printed wiring board according to an embodiment of the present invention; (b) A cross-sectional view of a main part of a mold in one step of a method for manufacturing the same printed wiring board (c ) Cross-sectional view of the main parts of the mold in another step of the same printed wiring board manufacturing method

[Figure 2] Cross-sectional view of the main parts of a printed wiring board produced by the same manufacturing method

[Figure 3] Cross-sectional view of the main parts of a printed wiring board produced by the same manufacturing method

FIG. 4: (a) A sectional view of the main parts of a mold used in the production of conventional printed wiring boards. (b) A sectional view of the main parts of a mold in one step of the manufacturing method of the same printed wiring board. (c) The same printed wiring. Cross-sectional view of the main parts of the mold in another step of the plate manufacturing method

[Figure 5] Cross-sectional view of main parts of a conventional printed wiring board

[Explanation of symbols]

1 Film 2a Mold 2b Mold 3 Resin substrate 4 Printed wiring board 5 Cushioning material 7 End

Claims (2)

[Claims] 1. A flexible film with a predetermined circuit pattern formed on at least its surface is placed in a mold so that the surface is in contact with the inner surface of the mold, and a resin is injected into the back side of the film and cured. When forming a printed wiring board in which a resin substrate is integrally bonded to the back surface of the film, a cushioning material is arranged at a position facing the tip of the resin substrate on the inner surface of the mold that is in contact with the surface of the film. A method for manufacturing a printed wiring board characterized by: 2. The method for manufacturing a printed wiring board according to claim 1, wherein the cushioning material placed in the mold is bonded and transferred to the surface of the flexible film.