Abstract
Many next generation products, including automobiles, aircraft, and industrial automation equipment, are making increasingly widespread use of embedded computer systems to assist in performing their functions more easily, accurately, and cost-effectively. Introduced over 25 years ago, on-board computer systems have now replaced the navigator and flight engineer on aircraft, the carburetor and timing belts on automobiles, and the machinist on automated milling machines. These systems are continually growing in complexity, with the most advanced having 206 MHz, 32-bit RISC microprocessors and 32 Mbit DRAM along with support for PCMCIA cards, and Ethernet links. In addition, new embedded computer systems are expected to include elements that interface the computer with other high tech innovations such as global positioning systems (GPS) and the internet, and to display information via liquid crystal displays. Furthermore, the applications in which these systems are used are multiplying. For example, in the construction and mining industries, it is now possible to find earth moving equipment which uses embedded computer systems to match plans for the site, provided by CD-ROM or internet, with maps of the location, provided by GPS, to identify the precise location to dig. The market for embedded control systems is expected to be over $4 billion this year.

Because of the very nature of these applications, embedded computer systems are expected to perform in environments that are significantly harsher than the typical home computer. The classic example of this type of environment is that encountered in automotive use, where temperatures can range from –40°C when unpowered on a cold winter day to 165°C under the hood when powered on a hot summer day. In addition, to extreme temperatures, the environment includes severe shock and vibration, and high humidity, along with road salt, sand, dirt and other ionic and organic contaminants. While this is an exceptionally harsh case, most systems are expected to perform over a wide range of temperatures. In order to build systems that can withstand these environmental conditions, it is necessary to evaluate the capability and reliability of the board materials, the case materials, and the attachment materials or solders at those temperatures.