Area-distributed-soldering of flexible and rigid printed circuit boards

Abstract

A novel design/process is described which facilitates area-distributed soldering of a flexible-printed-circuit to a circuit pack in an inspectable and repairable manner. In the design, solder joints are formed between surface-mount pads on a rigid printed-circuit-board and plated-through-holes on a flexible-printed-circuit. The joints are formed by heating both the flexible-printed-circuit and the printed-circuit-board to reflow temperatures and then allowing solder which has been deposited on the surface mount pads to rise through the plated-through-holes. Because solder rises up through the plated-through-holes to the exterior surface of the flexible-printed-circuit, spherical solder caps are clearly visible and inspectable. Solder joints are also easily repaired since the flexible-printed-circuit can be reheated to reflow one or all the solder joints. Two connector designs being used in AT&T products which employ area-distributed soldering of flex are discussed.<>