This book discusses the practical aspects of electrical and thermal modeling of packages. In addition, processing concerns for plastic packaged GaAs parts are also covered. The book emphasizes low cost industry standard packages. However, the principles involved translate well to other categories of packages. Digital issues such as crosstalk are well documented in other books and are therefore not covered in detail in this text. The principles for generation of equivalent circuit package models applies to both digital and analog parts. Digital designers and packaging engineers should still find this text useful. Subtleties often overlooked by standard methods of modeling packages for digital applications are considered and will become more important to the digital packaging engineer as frequencies continue to increase. It is hoped this book will be useful to both microwave and digital integrated circuit (Ie) designers as well as packaging engineers. In the past these disciplines were distinct. Packaging engineers typically were concerned with only materials and mechanical issues of the package. As long as there was an electrical connection made from the die to the external pin, packaging engineers had the freedom to do anything they wanted between these two points. At high frequency the issues change. Packaging engineers now have to work with die level designers to either create a package that performs well at high frequencies or to use readily available low cost packages that happen to meet the needs of the application.