Encapsulation of flex inner lead bonds for enhanced reliability

A method is presented for solving the lead-bending problem by coating the inner lead bonding area with a solvent-removable poly(imide siloxane). A three dimensional finite-element model was developed and is extended to analyze the stress and strain fields in the inner-lead area for various coating and encapsulation conditions. Based on the calculated results, the fundamental mechanisms governing the lead-bending and its prevention can be derived.