Clad Metal Circuit Board Substrates for Direct Mounting of Ceramic Chip Carriers

For a full realisation of the packaging advantages of leadless ceramic chip carriers, these devices will be surface mounted on large area printed circuit boards. However, thermal management and solder joint reliability concerns preclude the usage of conventional board materials and manufacturing processes in most high reliability applications. A new approach for achieving rugged, large area PCBs, incorporating thermal planes and the necessary thermal expansion match to chip carriers is described in this paper. The approach is based upon the use of a clad metal core substrate material fabricated from high conductivity copper and low thermal expansion rate Invar TM, a 36% nickel‐64% iron alloy. Mechanical, electrical and thermal properties of this clad metal are presented as well as techniques for adaption of PCB and porcelain/thick film technologies. Finally, other potential applications for this clad metal in the electronics industry are discussed.