ABSTRACT
Designers of printed wiring boards would like to design boards using standard E-glass impregnated with a high-temperature epoxy, polyimide, or cyanate ester resin and with surface-mounted components on both sides of the board. Unfortunately, the differences in CTE between the board and these components can cause the solder joints, during thermal cycling, to work-harden, resulting in foil cracks, component failure, and possibly board design failure. Designers can solve the CTE problem between the board and components by using low-CTE materials such as quartz, Kevlar®, Thermount®, copper-invar-copper (CIC), copper-molybdenum-copper (CMC), or silicon carbide–aluminum (SiC/Al). All of these could solve the CTE problem. CIC and CMC offer more rigidity that could reduce vibration/flexural hardening of the solder joints. In addition, the CIC and CMC can also act as a thermal heat sink to extract most of the heat generated when the components are placed close together.
