Aqueous processable, multilayer, photoimageable permanent coatings for printed circuits
OwnerMark R. McKeever, Karuppiah Chandrasekaraninventors
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Abstract
The use of a two layer photoimageable, aqueous processable, resist with an amphoteric binder in the layer laminated directly to a printed circuit board provides a permanent coating with improved adhesion throughout the lamination process while maintaining other desirable properties such as storage stability and circuit encapsulation.
Claims16
An aqueous processble, storage stable, photoimageable permanent coating element capable of adhering to a circuit board and withstanding molten solder after cure, which comprises:
- (a) a temporary support film;
- (b) a first layer of a photoimagable permanent coating composition comprising:
- (I) an amphoteric binder;
- (II) a carboxyl containing copolymeric binder;
- (III) a monomeric component containing at least two ethylenically unsaturated groups;
- and
- (IV) a photoinitiator or photoinitiator system;
- (c) a second layer of a photoimagable permanent coating composition comprising;
- (I) a carboxyl containing copolymeric binder;
- (II) a monomeric component containing at least two ethylenically unsaturated groups;
- (III) a photoinitiator or photoinitiator system;
- and
- (IV) a thermal crosslinking agent,
- wherein the first layer is interposed between the support and the second layer.
A process for laminating an aqueous processable, storage stable, photoimageable permanent coating element having a temporary support, first and second photoimagable layers and a cover film wherein the photoimagable layers are interposed between the support and cover films, to a printed circuit substrate which comprises the steps of:
- (a) applying to a surface of the substrate a liquid which is capable of migrating into the permanent coating and becoming part of the cured permanent coating;
- (b) removing the support film from the permanent coating element;
- (c) laminating the substrate and preformed nonliquid permanent coating element whereby excess liquid is forced along at least one edge of the laminated substrate and permanent coating element, whereby adherence is obtained of the substrate to the permanent coating through the laminating liquid penetrated permanent coating interface with the substrate surface and whereby any raised relief on the substrate is encapsulated with the permanent coating;
- and
- (d) trimming the excess permanent coating element from the substrate,
- wherein the first layer of the photoimagable permanent coating composition comprises:
- (I) an amphoteric binder;
- (II) a carboxyl containing copolymeric binder;
- (III) a monomeric component containing at least two ethylenically unsaturated groups;
- and
- (IV) a photoinitiator or photoinitiator system, and the second layer of the photoimagable permanent coating composition comprises:
- (I) a carboxyl containing copolymeric binder;
- (II) a monomeric component containing at least two ethylenically unsaturated groups;
- (III) a photoinitiator or photoinitiator system;
- and
- (IV) a thermal crosslinking agent.
Dependencies are inferred from the claim text.