Since the invention of the integrated circuit (IC) in the latter part of the 1950s, the development of new integrated circuits of greater complexity as shown in Figure 1.1 (Chapter 1) has progressed very rapidly. Along with greater numbers of components per integrated circuit have come greater challenges in cooling of electronic equipment. Generally, heat is generated from metallized areas on a small, thin, and fragile silicon die or chip inside a package. The heat transfer engineer must address the issue of cooling of electronics at all levels of packaging.

The chip package that is the housing for the silicon die is the most fundamental level of packaging for solid-state electronic equipment; it serves to protect the chip from the environment and to facilitate handling during manufacturing as well as chip interconnection. The next higher level of packaging is the circuit board. The printed circuit board (PCB), which is also often referred to as the printed wiring board (PWB), is a major element of any electronic equipment. It serves as a mounting surface for most of the basic components (chip packages) and provides wiring channels that act as conduits for chip-to-chip connections. The PCB is also frequently considered the primary field-replaceable unit and provides a test bed of accessible points for making circuit checks.