Claims
- 1. In a method of making a flexible printed circuit wherein:
- (a) a flexible belt-like substrate strip of an insulating polymer resin film is provided with a layer of electrically conductive metal foil bonded on at least one face and is punched with a plurality of through holes;
- (b) a photopolymer film is formed on said layer of electrically conductive metal foil;
- (c) the photopolymer film is exposed in a predetermined pattern;
- (d) the photopolymer film is developed and is thereby removed according to said pattern;
- (e) the foil on the substrate, where it is now bare of photopolymer film in certain areas as a result of conducting step (d), is subjected to an etchant, for removing said layer of electrically conductive metal foil where it has thus been bared;
- (f) the photopolymer film is removed from where it remains in place upon the remaining pattern of electrically conductive metal foil that is to become electrical circuitry; and
- (g) a solder resist layer is formed on selected portions of the thus-bared pattern of electrically conductive metal foil that is to become electrical circuitry,
- an improvement for overcoming a problem which arises where the substrate strip of insulating polymeric resin film is subject to longitudinal shrinkage during processing subsequent to the conducting of step (a), in that, in conducting step (g), said selected portions where said solder resist layer is formed are inaccurately located relative to said through holes or said pattern of electrically conductive metal foil that is to become electrical circuitry,
- said improvement comprising:
- in conducting step (e) there is left on said substrate strip of insulating polymer resin, at least one long, narrow band of said layer of electrically conductive metal in a substantially non-etched condition, of which each such band lies near and extends parallel to a respective lateral extreme of said belt-like strip of insulating polymer resin and adjacent, but separate from and laterally outside said pattern of electrically conductive metal foil that is to become electrical circuitry, so that said at least one band is available at least until the completion of the conducting of step (g), to prevent inaccurate location of said selected portions where said solder resist layer is formed by preventing longitudinal polymer film of said substrate,
- said at least one band being formed so as to be on the order of as long as said pattern of electrically conductive metal foil that is to become electrical circuitry, at least to the extent that said pattern of electrically conductive metal is to become one flexible printed circuit.
- 2. The method of claim 1, wherein:
- in order to leave said at least one long, narrow non-etched band of said layer of electrically conductive material on said substrate strip when conducting step (e),
- no later than when conducting steps (b)-(d), forming a respective etch-resistant layer on the layer of electrically conductive metal foil in a pattern corresponding to where the layer of electrically conductive metal foil is to remain non-etched when conducting step (e), for each such band.
- 3. The method of claim 1, wherein:
- said pattern of electrically conductive metal foil is formed on said substrate strip of insulating polymer resin film repetitively in at least one longitudinally extending series of what can be separated by cutting across said strip subsequent to conducting step (g) to produce a plurality of like flexible printed circuits;
- in conducting step (a), at least some of the through holes are formed in two longitudinal series to function as sprocket holes, each such series lying near and extending parallel to a respective lateral extreme of said belt-like strip of insulating polymer resin film and extending along what is to become a plurality of said like flexible printed circuits; and
- in forming said at least one band, a respective said band is superimposed upon each series of sprocket holes on at least one face of the substrate belt-like strip of insulating polymer resin film, each band being broader than the respective series of sprocket holes, so that the sprocket holes do not divide the respective band into a series of longitudinally separated segments.
- 4. The method of claim 2, wherein:
- each said etch-resistant layer is formed on said layer of electrically conductive foil before step (b) is conducted, and when step (b) is conducted, said photopolymer film is formed on said layer of electrically conductive metal foil where said layer of electrically conductive metal foil is not already covered by a said etch-resistant layer.
- 5. The method of claim 1, wherein:
- in conducting step (a) a said layer of electrically conductive metal foil is bonded on each face of said substrate strip of insulating polymer resin film; and
- prior to conducting step (b) at least some of said through holes corresponding to locations in said pattern of electrically conductive metal foil that is to become electrical circuitry are plated-through with electrically conductive metal electrically joining said layers of electrically conductive metal foil on the opposite faces of said substrate of insulating polymer resin film through each such through hole, while preserving that through hole in an open condition.
- 6. The method of claim 5, wherein:
- in order to leave said at least one long, narrow non-etched band of said layer of electrically conductive material on said substrate strip when conducting step (e),
- no later than when conducting steps (b)-(d), forming a respective etch-resistant layer on the layer of electrically conductive metal foil in a pattern corresponding to where the layer of electrically conductive metal foil is to remain non-etched when conducting step (e), for each such band.
- 7. The method of claim 5, wherein:
- said pattern of electrically conductive metal foil is formed on said substrate strip of insulating polymer resin film repetitively in at least one longitudinally extending series of what can be separated by cutting across said strip subsequent to conducting step (g) to produce a plurality of like flexible printed circuits;
- in conducting step (a), at least some of the through holes are formed in two longitudinal series to function as sprocket holes, each such series lying near and extending parallel to a respective lateral extreme of said belt-like strip of insulating polymer resin film and extending along what is to become a plurality of said like flexible printed circuits; and
- in forming said at least one band, a respective said band is superimposed upon each series of sprocket holes on at least one face of the substrate belt-like strip of insulating polymer resin film, each band being broader than the respective series of sprocket holes, so that the sprocket holes do not divide the respective band into a series of longitudinally separated segments.
- 8. The method of claim 5, wherein:
- each said etch-resistant layer is formed on said layer of electrically conductive foil before step (b) is conducted, and when step (b) is conducted, said photopolymer film is formed on said layer of electrically conductive metal foil where said layer of electrically conductive metal foil is not already covered by a said etch-resistant layer.
- 9. The method of claim 1, wherein:
- said pattern of electrically conductive metal foil is formed on said substrate strip of insulating polymer resin film repetitively in at least one longitudinally extending series of what can be separated by cutting across said strip subsequent to conducting step (g) to produce a plurality of like flexible circuits;
- in conducting step (a), at least some of the through holes are formed in two longitudinal series to function as sprocket holes, each such series lying near and extending parallel to a respective lateral extreme of said strip of insulating polymer resin film and extending along what is to become a plurality of said like flexible printed circuits; and
- in forming said at least one band, a respective said band is formed laterally between a respective said longitudinal series of sprocket holes and said pattern of electrically conductive material that is to become electrical circuitry.
Priority Claims (1)
Number |
Date |
Country |
Kind |
54-124615 |
Sep 1979 |
JPX |
|
Parent Case Info
This is a continuation of application Ser. No. 188,666, filed Sept. 19, 1980 (now abandoned).
US Referenced Citations (5)
Non-Patent Literature Citations (1)
Entry |
Weaver, H. A., "High Volume Production of Flexible PWBs," Western Electric Co. Inc., Richmond, Virginia, USA, pp. 1.27.1-1.27.14. |
Continuations (1)
|
Number |
Date |
Country |
Parent |
188666 |
Sep 1980 |
|