Imaging on substrates with alkaline strippable UV blocking compositions and aqueous soluble UV transparent films
View Patent ↗Substrates, such as printed circuit boards, are coated with an aqueous alkaline developable UV photosensitive material followed by applying an aqueous soluble UV transparent film to coat the UV photosensitive material. An aqueous alkaline strippable UV blocking composition is selectively applied to the surface of the UV transparent film to function as a mask. UV light is applied to portions of the UV photosensitive material not covered by the mask. The UV blocking composition, UV transparent film and selective sections of the UV photosensitive material are simultaneously removed with an aqueous alkaline developer solution to form an image on the substrate.
1. A method comprising:
a. providing a substrate comprising raised traces, and one or more apertures selected from the group consisting of through-holes and vias;
b. applying an aqueous alkaline soluble UV photosensitive material adjacent a surface of the substrate comprising the one or more apertures and the raised traces to provide an unplanarized surface on the aqueous alkaline soluble UV photosensitive material;
c. applying a flexible aqueous soluble UV transparent film adjacent the aqueous alkaline soluble UV photosensitive material with the unplanarized surface to planarize the surface, wherein the flexible aqueous soluble UV transparent film is selected from the group consisting of aqueous soluble polyvinyl alcohols, water soluble cellulose ethers, water soluble carboxyalkylcellulose ethers, water soluble salts of carboxyalkylcellulose, water soluble salts of carboxyalkyl starch, water soluble polyvinyl pyrrolidone, water soluble polyacrylamides, water soluble salts of polyacrylic acid, gelatin and ethylene oxide polymers;
d. selectively applying an aqueous alkaline strippable UV blocking composition adjacent the flexible aqueous soluble UV transparent film;
e. exposing the aqueous alkaline soluble UV photosensitive material with the planarized surface to UV radiation except in regions covered with the aqueous alkaline strippable UV blocking composition; and
f. simultaneously removing the aqueous alkaline strippable UV blocking composition, the flexible aqueous soluble UV transparent film and selective portions of the aqueous alkaline soluble UV photosensitive material with the planarized surface with an aqueous alkaline solution.
2. The method of claim 1 , further comprising providing a vision system to capture fiducials on a surface of the substrate and scale digital aqueous alkaline soluble UV photosensitive material data.
3. The method of claim 1 , wherein the aqueous alkaline strippable UV blocking composition comprises one or more rosin resins, one or more fatty acids and one or more UV blocking agents.
4. The method of claim 3 , wherein the one or more UV blocking agents comprise benzophenone, benzophenone derivatives, benzotriazoles, benzotriazole derivatives, triazines, cinnamates, salicylates, crylenes, cyanoacrylates, malonates, oxanilides, formamides, anthraquinones, substituted anthraquinones, organic dyes and organic pigments.
5. The method of claim 3 , wherein the one or more rosin resins comprise fully hydrogenated and partially hydrogenated rosin resins.
6. The method of claim 3 , wherein the one or more fatty acids comprise caprylic acid, capric acid, lauric acid, linoleic acid, myristic acid, oleic acid, palmitic acid and stearic acid and salts thereof.
7. The method of claim 3 , wherein the one or more rosin resins are in amounts of 15% to 50% of the aqueous alkaline UV blocking composition.
8. The method of claim 3 , wherein the aqueous alkaline strippable UV blocking composition further comprises one or more of colorants.
9. The method of claim 1 , wherein the substrate is a printed circuit board.