Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Patent
1993-09-08
1995-08-22
Picard, Leo P.
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
29846, 21912169, 21912167, 21912168, H05K 300
Patent
active
054441889
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to the manufacture of flexible circuit wiring "boards" having conductors that protrude, like finger leads, beyond edge(s) of a window portion in the board or beyond an outer edge of the board.
DESCRIPTION OF THE PRIOR ART
A prior art flexible printed circuit, i.e., wiring board, having outwardly protruding conductors in the form of finger leads is shown in FIGS. 4A and 4B. In this prior art circuit board, plural conductors 11 extend outwardly into an aperture or window region 12 provided in a flexible insulating base member 13.
In a flexible circuit wiring board of conventional structure as shown in FIG. 4, the conductors must have a degree of rigidity so that the leads protruding into window region 12 will not be easily deformed. The requirement for rigidity precludes a decrease in the thickness of the conductors 11 of the circuit and thus imposes a limitation on the ability to increase wiring density by finely forming the conductors.
SUMMARY OF THE INVENTION
The present invention provides a flexible circuit wiring board having conductors, protruding in the form of finger leads, which resist deformation even when finely formed. The present invention also encompasses a method of producing such a flexible circuit wiring board having closely spaced conductors.
The protruding conductors, i.e., the leads, of a flexible circuit in accordance with the invention have a flexible insulating resin layer on part of at least one surface thereof, said resin layer having nearly the same width as the conductors and reinforcing the finger leads.
In the practice of the method of the invention, the requisite circuit wiring pattern is formed on one surface of an insulating base member, i.e., an insulating substrate. A surface protection layer is then formed on the upper, i.e., the exposed, surface of the conductors which define the wiring pattern. The surface protection layer defines cut-away portions in locations where the finger lead-like circuit wiring conductors are to be formed. The beam provided by an excimer laser is directed to the second surface of the substrate in order to remove an area of the insulating base member thus leaving outwardly extending finger lead-like circuit wiring conductors with the surface protection layer on one side thereof.
The present invention also encompasses the formation of the cut-away portion(s) in the surface protection layer by directing the excimer laser beam at the exposed surface of the surface protection layer after the substrate has been removed to form the finger lead-like circuit wiring conductors.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial top plan view which schematically illustrates a flexible circuit wiring board in accordance with a first embodiment of the present invention;
FIG. 2 is a cross-sectional, side elevation view taken along line X--X of FIG. 1;
FIGS. 3A through 3C are diagrams illustrating steps performed in the production of the flexible circuit wiring board of FIGS. 1 and 2; and
FIGS. 4A and 4B are, respectively, views similar to FIGS. 1 and 2 which show the prior art.
DESCRIPTION OF THE DISCLOSED EMBODIMENT
FIG. 1 is a plan view which schematically illustrates portions of a flexible circuit wiring board in accordance with a first embodiment of the present invention, and FIG. 2 is a sectional view taken along line X--X of FIG. 1.
In FIGS. 1 and 2, a flexible insulating base member, comprised of a polyimide film or the like, is indicated at 1. A circuit wiring pattern, formed on one surface of base member 1, is indicated at 2. Wiring pattern 2 includes conductors 2A, in the form of finger leads, that protrude beyond an edge of the flexible insulating base member 1. This edge may, for example, be a side boundary of a rectangular shaped window provided in base number 1. The circuit wiring pattern 2 and the finger lead-like circuit wiring conductors 2A, in one reduction to practice, have a width of 50.mu.m and a thickness of 17.5 .mu.m.
The circuit wiring pattern 2, except portions o
REFERENCES:
patent: 4931134 (1990-06-01), Hatkevitz et al.
patent: 4978830 (1990-12-01), Millerick et al.
patent: 5065506 (1991-11-01), Kinbayshi
patent: 5088008 (1992-02-01), Takeyama et al.
patent: 5278385 (1994-01-01), Gerome et al.
Inaba Masaichi
Iwayama Takeshi
Miyagawa Atsushi
Nippon Mektron Ltd.
Picard Leo P.
Thomas L.
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