Invention Grant
US5789142A Solder mask system 失效
焊接面罩系统

Solder mask system
Abstract:
A masking method employing a photodefinable resin as a permanent dielectric mask, in which the resin contains a catalytic filler that when activated enables direct electroless plating of the resin. The resin serves to simplify selective electroplating of isolated surface features such as metal pads, while also improving the topology of the external surface of the circuit board, particularly when small metal pads require a controlled volume of a reflowable metal. The resin is preferably photodefined to eliminate recessed areas around the metal pads, thereby promoting definition of the metal features, and yielding a nearly planar surface. Additional features that can be provided with the method include external conductive ground planes and electromagnetic shield layers within a multilayer circuit board. The masking method can be advantageously used with both reflowable metals and metal alloys, such as tin/lead, and nonreflowable metals and metal alloys, such as gold, palladium and platinum.
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