Aqueous processable, multilayer, photoimageable permanent coatings for printed circuits
First Claim
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1. An aqueous processable, storage stable, photoimageable permanent coating element capable of withstanding molten solder after cure, which comprises in order:
- (a) a temporary support film;
(b) a first layer of a polymerizable permanent coating composition comprising;
(I) a hydrophobic binder consisting essentially of structural units A, structural units B or structural units A and B of the formula;
##STR4## in which;
R1 is H or alkyl;
R2 is phenyl, nitrile, hydroxyl or CO2R3;
R3 is H or alkyl which is unsubstituted or substituted with one or more hydroxy groups, andR4, R5, R6 and R7 are independently H or alkyl;
and(II) a monomeric component containing at least two ethylenically unsaturated groups;
(c) a second layer of a photoimageable permanent coating composition comprising;
(I) a carboxyl containing copolymeric binder, wherein the level of carboxyl groups is determined for a given composition by optimizing the amount needed for good development in aqueous alkaline developer, having structural units of the formula;
##STR5## in which;
R1 is H or alkyl;
R2 is phenyl, CO2 R3 or macromer; and
R3 is H or alkyl which is unsubstituted or substituted with one or more hydroxy groups,(II) a monomeric component containing at least two ethylenically unsaturated groups,(III) a photoinitiator or photoinitiator system, and(IV) a thermal crosslinking agent,(d) cover film,whereinthe adhesion of said first layer (b) to said second layer (c) is greater than the adhesion between said first layer (b) and said support film (a) ;
the adhesion of said first layer (b) to said second layer (c) is greater than the adhesion between said second layer (c) and said cover film; and
the adhesion between said first layer (b) and said support film (a) is greater than the adhesion between said second layer (c) and said cover film.
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Abstract
The use of a two layer photoimageable, aqueous processable, resist with a hydrophic binder in the outermost layer provides a permanent coating highly resistant to printed circuit processing chemicals. This resistance results in levels of adsorbed or absorbed ionic contamination less than 14 micrograms per square inch.
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Citations
8 Claims
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1. An aqueous processable, storage stable, photoimageable permanent coating element capable of withstanding molten solder after cure, which comprises in order:
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(a) a temporary support film; (b) a first layer of a polymerizable permanent coating composition comprising; (I) a hydrophobic binder consisting essentially of structural units A, structural units B or structural units A and B of the formula;
##STR4## in which;
R1 is H or alkyl;R2 is phenyl, nitrile, hydroxyl or CO2R3; R3 is H or alkyl which is unsubstituted or substituted with one or more hydroxy groups, and R4, R5, R6 and R7 are independently H or alkyl; and (II) a monomeric component containing at least two ethylenically unsaturated groups; (c) a second layer of a photoimageable permanent coating composition comprising; (I) a carboxyl containing copolymeric binder, wherein the level of carboxyl groups is determined for a given composition by optimizing the amount needed for good development in aqueous alkaline developer, having structural units of the formula;
##STR5## in which;
R1 is H or alkyl;R2 is phenyl, CO2 R3 or macromer; and R3 is H or alkyl which is unsubstituted or substituted with one or more hydroxy groups, (II) a monomeric component containing at least two ethylenically unsaturated groups, (III) a photoinitiator or photoinitiator system, and (IV) a thermal crosslinking agent, (d) cover film, wherein the adhesion of said first layer (b) to said second layer (c) is greater than the adhesion between said first layer (b) and said support film (a) ;
the adhesion of said first layer (b) to said second layer (c) is greater than the adhesion between said second layer (c) and said cover film; and
the adhesion between said first layer (b) and said support film (a) is greater than the adhesion between said second layer (c) and said cover film. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification