ABSTRACT
The simplest form of package is one that takes a single semiconductor chip and encloses it in a sturdy and easily handled container suitable for plugging into an array of other electronic components, that is, the single-chip can. This chapter describes the three different kinds of substrates which can be used to support chips in packages: headers in cans, leadframes and ceramic sheets. Alumina sheets for microelectronic substrates are commonly produced by a continuous casting process and some of the other important ceramic materials can be prepared by the same techniques. The mechanical properties of the fired ceramic sheet are very dependent on the retained porosity, since small pores are nucleation sites for brittle failure. The chapter also describes the die-bonding process that is used to attach the chip to the substrate and in some cases to provide an earth contact for the devices on the chip surface. It discusses the methods by which soldering processes are carried out.
