Functionally graded coatings for lead wires in medical implantable hermetic feedthrough assemblies

Abstract

A feedthrough filter capacitor assembly is described. The feedthrough filter capacitor assembly comprises an outer ferrule hermetically sealed to an insulator of a dielectric material seated within the ferrule. The insulative material is also hermetically sealed to at least one lead wire. Instead of being made of platinum or platinum/iridium, the lead wire comprises a core of a non-noble metal supporting a functionally graded coating. The metal core has an inner layer of the same the non-noble metal of the core and an outer layer of a noble metal. A gradient transition zone exists between the non-noble metal and the outer noble metal. Consequently, lead wires having all the beneficial attributes of platinum and platinum/iridium wire can be built into hermetic feedthroughs, but at a significantly reduced cost. In a preferred form, a filter capacitor is mounted on the insulator and electrically connected to the lead wires and to the ferrule to prevent unwanted EMI signals from traveling along the wires and entering the interior of the medical device.