Abstract: Disclosed is a method of producing a flexible circuit board having gold selectively plated on only desired elements of the conductive circuits. These desired elements typically are attachment sites, such as wire bond pads or ball grid array pads, for semiconductor chips. This method eliminates the requirement to buss all circuits to a common plating contact by using a background seed metal for plating continuity. This method also provides a means to alleviate the requirement for precise registration or alignment when multiple photoresist layers are employed in order to selectively plate only a portion of the metallic elements present on the flexible circuit board. The defect of resist lifting followed by nickel/gold underplating is eliminated by conditioning the intermediate photoresist to survive the nickel/gold plating bath.

Abstract: Disclosed is a method of producing a flexible circuit board having gold selectively plated on only desired elements of the conductive circuits. These desired elements typically are attachment sites, such as wire bond pads or ball grid array pads, for semiconductor chips. This method eliminates the requirement to buss all circuits to a common plating contact by using a background seed metal for plating continuity. This method also provides a means to alleviate the requirement for precise registration or alignment when multiple photoresist layers are employed in order to selectively plate only a portion of the metallic elements present on the flexible circuit board. The defect of resist lifting followed by nickel/gold underplating is eliminated by conditioning the intermediate photoresist to survive the nickel/gold plating bath.

Abstract: An electrical connection between a flexible circuitized substrate and a separator conductor is formed wherein the substrate's dielectric member has a region of reduced thickness immediately adjacent the portion of the substrate's conductor that is being connected (e.g., using thermocompression bonding) to the separate conductor (e.g., a chip's contact site or a solder ball thereon). Heat and pressure is applied to form the bond between both conductors, this heat passing through the reduced thickness dielectric while appropriate pressure is applied. The reduced thickness assures heat flow (and possibly displacement of the dielectric in this region, e.g., it “melts back”) to thus facilitate bond formation, but also is able to positively retain several conductors of the substrate in spaced alignment during the bonding to respective solder balls or chip contact sites.