ABSTRACT
This chapter describes the purpose and usage of lead frames and the difference between heat spreaders and heat sinks and conveys the purpose and importance of lead frames in semiconductor packaging. It looks at the use of metallic lead frames as a carrier for semiconductor chips. The metal is a stable platform to withstand the various package assembly processing steps, through both mechanical and thermal stresses. The metal can be easily fabricated by a variety of processes into a number of shapes and forms. Aluminum is commonly used as a heat spreader and heat sink material. Heat slugs and spreaders contact the backside of a lead frame die paddle, or the backside of the silicon chip in the case of a flipped chip. Gold has been the standard metal for bonding wires in plastic semiconductor packages for decades, due to its high environmental stability coupled with good electrical conductivity.
