Abstract: A circuit pattern on a circuit board has at least one contact finger termination to be coupled to a connector contact. A conductive overlay is solder-bonded to the base metal of the contact finger. The overlay is a composite structure of a number of layers. A base layer of copper faces, and is solder-bonded, to the base. A surface layer of gold provides a contact area for the connector contact. A layer of nickel between the base layer and the surface layer acts as a barrier layer to prevent copper from migrating through the surface layer to deposit as a contaminant on the surface of the contact area.

Abstract: In a thermocompressive soldering process, a conductive overlay of a material such as gold is applied to a contact finger of a circuit board.In carrying out this process, the overlay is initially carried on an adhesively coated strip such as a polyimide tape. To transfer the overlay to the contact finger, it is aligned with the contact finger and temporarily attached to the circuit board. A heat conductive resilient sheet is then interposed between the circuit board and a thermode. The thermode is adjusted to engage the contact finger with a predetermined force. The force is resiliently distributed by the interposed sheet. Heat is then applied from the thermode through the resilient sheet to liquefy a solder coating on the overlay and to bond the overlay to the contact finger upon resolidification of the solder. The applied force is sustained during the application of head and during a subsequent cooling period during which the solder resolidifies.