COMPOSITE LEAD FRAME STRIP - having ferritic stainless steel core and nickel, copper and tin or nickel plated coatings

摘要

A lead frame strip material comprises (a) a ferritic stainless steel core, (b) a continuous Ni strike layer, (c) a continuous inner Cu layer and (d) a continuous Ni o rSn layer, each layer surrounding and contacting the underlying material. The composite strip is coled reduced by 40-60% to at most 30 mils and has a dense, shiny, continuous outer surface. The strip can be precision stamped or etched to any required configuration and is produced at reasonable cost. It has the desired lead frame material properties of: good thermal and electrical conductivity, low thermal expansion, good mechanical properties, corrosion resistance and a surface that is wettable by encapsulating materials and can be plated with Au or Ag. With Sn outer coating, it may be directly thermo compression or ultrasonically bonded to wires.