Circuit Board Stand-Off to Reduce Thermal Fatigue
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-27
Height of a solder joint (the distance from the board surface to the component) is critical to the thermal cycle fatigue lifetime of the solder connection. This fatigue is caused by difference in thermal expansion between the printed circuit board material and the components mounted on the board by means of solder joints. The differences in the thermal coefficients of expansion are greater for components mounted on injection molded thermoplastic cards than for the same component mounted on FR-4 boards. This significantly decreases the solder joint lifetime due to thermal cycling (power on-off cycles) on injection molded boards versus conventional boards. The figure shows a platform or stand-off molded in a thermoplastic card to control such fatigue.