Terminal and Cooling Requirements for LSI Packages

As the level of digital circuit integration on integrated circuit (IC) chips increases, more input-output (I/0) terminals are required on the chip package. More terminals mean a larger conventional package. This can frustrate achievement of higher overall gate density on the printed circuit (PC) board assembly. Chip packages providing terminals as a function of package area or at reduced terminal pitch offer some relief. Gate density may also be thermally limited. Coefficient and exponent values are empirically derived for the Rent equation to predict terminal requirements. A graphical means is developed which can help the designer visualize the trade-offs between package type, terminal pitch, and cooling requirements. Some practical examples are described.