Method of making a parylene coating for soldermask

摘要

A method for making an HDI circuit including backside connections uses parylene as a protective coating. The method includes the steps of: procuring an insulating substrate including an active chip which has exposed electrical or thermal connection(s) on the rear surface thereof, applying a parylene coating to the exposed connections to protect the connections; performing additional HDI interconnect processing steps as desired on the front surface of the substrate; selectively removing a portion of the parylene coating to expose at least a portion of a connection; and making electrical connection to the exposed backside connections by application of a conductive material in its liquid state to the removed regions. The parylene coating is removed by an excimer laser. The step of making electrical connection to the backside electrical connections may be performed by application of solder, or conductive epoxy in its liquid state.