JPH03131046A - Flexible circuit board - Google Patents

Abstract

PURPOSE:To improve the dimensional accuracy of the pattern of a flexible circuit board, and to fine the pattern by forming an organic film layer having a shape different from a first organic film layer onto the first organic film layer. CONSTITUTION:A film-like conductive substance 8 such as a copper foil, an aluminum foil, a nickel foil, etc., and the first organic film 1 of polyimide, polyester, etc., are formed in a stratiform shape. The solution of a substance as the base material of the organic film of polyimide, polyester, etc., or the solution of the raw material substance of the organic film is casted or printed onto the conductive substance 8 and the organic film 1 formed in the stratiform shape, thus forming a second organic film layer 4 having a shape different from the first organic film 1. Required sections can be thickened for ensuring the stability of processes or sections except sections, which must be thinned on application, thickened previously owing to two layer structure in which thickness is made to differ partially. Accordingly, the rigidity of a tape can be ensured collectively, thus improving the dimensional accuracy of pattern formation, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a flexible circuit board in which a wiring pattern of a conductive material is formed on a substrate of polyimide, polyester, or the like.

[Prior Art] A conventional flexible circuit board has been manufactured by a method as shown in FIG. In the figure, 21 indicates a base material such as polyimide or polyester, 22 indicates an adhesive layer, and 23 indicates a copper foil layer serving as a conductor. Further, FIG. 3 shows an example of mounting a semiconductor chip using a conventional flexible circuit board, and an example of mounting a fourth path board on a liquid crystal panel.In the figure, 24 is a semiconductor chip, 25 is a mold resin for semiconductor chips, 27 is a liquid crystal panel glass, 27 is a TO electrode, and 28 is an anisotropic conductive film.

As shown in Fig. 2, in a conventional 7x7pu circuit board, there is first a base material made of an organic film such as polyimide or polyester, and an adhesive is secondly applied to the base material made of the organic film. Ru. After this, predetermined holes such as device holes are punched, and the base material made of the organic film and the copper foil film are bonded via the adhesive layer.

Thereafter, the steel foil film attached to the organic film base material is pattern-etched to produce a flexible circuit board.

[Problem to be solved by the invention] However, the conventional 7 lexiple circuit board
As is clear from FIGS. 4 and 4, there were many problems.

First, conventional flexible circuit boards have a single-layer base material made of organic film, so the rigidity of the organic film cannot be ensured unless the thickness of the base material exceeds a certain value for process stability. If the rigidity of the material cannot be ensured, the dimensional accuracy of pattern formation, etc. will be reduced, or the mounting position accuracy of electronic chip components, such as gigang bonding in the manufacturing process, will be reduced, and the mounting yield will be reduced. It happens.

In addition, the conventional 7-lexiple circuit board has a base material made of organic film in one layer, and the base material is thick (because it has to be
For example, this flexible circuit board is coated with an anisotropic conductive film or U
In the case of bonding with a V-adhesive or the like, there is a high risk that the bonding reliability will be reduced due to residual stress or generated stress due to the difference in thermal expansion coefficient 2 elastic constant between the organic film and another inorganic substrate.

Therefore, the present invention solves these drawbacks, prevents the reduction in dimensional accuracy of the flexible circuit board, and improves the reliability of bonding with other inorganic substrates such as glass or ceramics and semiconductors and other electronic components. The purpose is to make

[Means to solve the problem] The 7-lexiple circuit board according to the present invention is made of copper foil.

A step of forming a layer of a film-like conductive material such as aluminum foil or nickel foil and a first organic film such as polyimide or polyester, which becomes a base material for an organic film such as polyimide or polyester on the first organic film. It is characterized in that it is produced by a step of forming a second organic film layer in a shape different from that of the first organic film by casting or printing a solution of a substance or a solution of a raw material for the organic film. do.

FIG.
α) shows a ribbon-shaped thin copper foil film;
) shows a polyimide film coated with an adhesive layer on one side. Moreover, FIG. 1(C) shows a state in which a copper foil film is attached to the adhesive surface of a polyimide film by heating and pressurizing.

Furthermore, FIG. 1(d) shows that a polyimide solution is printed on a polyimide film to which copper foil is attached, in a shape different from that of the polyimide film, and then the polyimide solution is dried and hardened, so that the thickness of the organic film layer can be adjusted in some areas. FIG. 1(g) shows a copper foil film layer patterned by etching.

The flexible circuit board according to the present invention has a two-layer structure with different thicknesses in different parts, so in order to ensure the stability of the process, it is possible to make the necessary parts thicker (or thicker in parts other than those that need to be thinned for the purpose of use). (As a result, the overall rigidity of the tape can be ensured, and as a result, it is possible to improve the dimensional accuracy of pattern formation, etc.).Furthermore, as a secondary effect, it is possible to improve the dimensional accuracy of pattern formation, etc. In practice, it is possible to improve the mounting position accuracy of electronic components and also to make the mounting pitch finer.

Furthermore, since the flexible circuit board according to the present invention has a two-layer structure with different thicknesses in different parts, for example, a thin part of the base material made of an organic film of the flexible circuit board is anisotropically bonded to another inorganic board such as glass or ceramic. When bonded using a conductive film or UV adhesive, it is possible to reduce the residual stress caused by the difference in thermal expansion coefficient 9 elastic constant between the organic film and another inorganic substrate, increasing the reliability of the bond. I can do things.

FIG. 6 shows one example of application of the flexible circuit board according to the present invention. In the figure, 1 is the first organic film base layer, 5
4 is a circuit wiring patterned from a metal thin film, and 4 is a second circuit wiring patterned from a metal thin film.
10 represents an organic film layer, and 10 represents a semiconductor chip. As is clear from FIG. 6, the organic film layer also exists in the portion of the flexible circuit board on which the semiconductor chip is mounted, and this portion is one step thinner than the other portions. The metal wiring pattern is formed so that the position in the plane direction corresponds to the electrode pad of the semiconductor chip. As the number of semiconductor electrode pads increases and the pitch becomes finer, the metal wiring pattern also becomes finer. At this time, since the organic film layer exists under the metal wiring pattern, it is possible to prevent the pattern shape maintenance accuracy from decreasing due to the metal wiring pattern becoming thinner. On the other hand, in order to bond the electrode pads of the semiconductor chip and the metal wiring pattern, it is necessary to apply a necessary amount of heat to the bonding portion. On the other hand, in the present invention, since the organic film layer corresponding to the part of the semiconductor chip is a negative layer, when heat is applied from the outside of the organic film, the heat is easily transmitted to the bonding part. , the heating time can be shortened (to improve the work cycle time, and damage to the organic film due to heating can be suppressed).Furthermore, since the organic film in the heating section is thin, it is possible to Residual stress is reduced and reliability of the joint can be improved.

Furthermore, FIG. 5 shows another application example of the flexible circuit board according to the present invention, in which 1 is a first organic film base layer, 4 is a second organic film layer, and 11 is a liquid crystal display panel. 12 indicates an anisotropic conductive film. In Figure 4, the copper foil terminals of the flexible circuit board are aligned with the electrode terminals of the liquid crystal display panel, the anisotropic conductive film is sandwiched between them, and the organic film layer is heated and pressurized to form the electrodes of the liquid crystal display panel. Make a conductive connection between the terminal part and the above steel foil terminal. At this time, since only the first organic film layer is the portion of the organic film of the flexible circuit board that is bonded to the electrode terminal portion of the liquid crystal display panel, residual stress caused by bonding can be reduced. On the other hand, the part of the organic film of the 7-flex circuit board that is not bonded to the electrode terminal part of the liquid crystal display panel is the overlapped part of the first organic film layer and the second organic film layer, and has stiffness. Workability during manufacturing and use is ensured.

[Effects of the Invention] As explained above, the present invention improves the dimensional accuracy of the pattern of the flexible circuit board by forming an organic film layer having a different shape on the first organic film layer in the flexible circuit board. This has the effect of improving reliability by reducing residual stress in the bonding between the 7-lexiple circuit board and other electronic components, making it possible to make patterns more detailed.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating an example of the manufacturing process of a 7x pull circuit board according to the present invention. FIG. 2 is a diagram showing an example of the manufacturing process of a conventional 7-lexiple circuit board. FIG. 3 is a diagram showing an example of semiconductor chip mounting using a conventional flexible circuit board. FIG. 4 is a diagram showing an example of mounting a conventional liquid crystal display panel. FIG. 5 is a diagram showing an example of mounting a liquid crystal display panel using a flexible circuit board according to the present invention. FIG. 6 is a diagram showing an example of semiconductor chip mounting using the flexible circuit board according to the present invention. 2...Adhesive layer 4...Second organic film layer 5...
...Metal wiring pattern 1 0...Semiconductor chip 6...Molding agent 5...Self...Resist agent 1... ...Liquid crystal display panel 2...Anisotropic conductive film 7...Electrode terminal 1...
......Organic film layer 2...Adhesive layer 5...Copper foil layer 4...Semiconductor chip 5...・・・・・・Molding agent 6・・・・・・Liquid crystal panel glasst・・・・・・
...First organic film layer 7......To
Electrode 8 - Anisotropic conductive film 8 Copper foil film Z Copper foil pattern

Claims (3)

[Claims] (1) Step of forming a layer of a film-like conductive material such as copper foil, aluminum foil, or nickel foil and a first organic film such as polyimide or polyester, and forming an organic film such as polyimide or polyester on the first organic film. A step of forming a second organic film layer in a shape different from that of the first organic film by casting or printing a solution of a substance serving as a base material or a solution of a raw material material of the organic film. A flexible circuit board characterized by manufacturing. (2) The flexible circuit board according to claim 1, further comprising a second layered film having one or more holes having substantially the same shape as at least a semiconductor chip or an electronic chip component such as a chip resistor or a chip capacitor. (3) A claim characterized in that the second layered film has at least one narrow hole curved in a rectangular shape, an L-shape, a U-shape, an O-shape, etc. 1
The flexible circuit board described.