During the past two decades, large, high-density, high-input/output (I/O) electronic interconnect SMT (surface mount technology) packages such as ceramic column grid arrays (CCGAs) have increased usage in avionics hardware of NASA projects. The test boards built with CCGA packages are expensive and often require rework to replace reflowed, reprogrammed, failed, or redesigned CCGA packages. Theoretically, a good rework process should have a similar temperature- time profile as that used for the original manufacturing process of solder reflow. A multiple rework process may be implemented with CCGA packaging technology to understand the effect of the number of reworks on the reliability of this technology for harsh, extreme, thermal environments.
CCGA 624 packages have been increasing in use based on their advantages such as high interconnect density, very good thermal and electrical performance, and compatibility with standard surface-mount packaging assembly processes. Reworked CCGA packages are used in space applications such as logics and microprocessor functions, telecommunications, flight avionics, and payload electronic assemblies. As these packages tend to have less solder joint strain relief than leaded packages, the reliability of reworked CCGA-624 packages is very important for short- and long-term space missions.
In general, reliability of the assembled electronic packages reduces as a function of number of reworks, and the extent of reliability loss is not known yet. A CCGA rework process has been implemented to design a daisy-chain test board consisting of 624 packages. Reworked CCGA interconnect electronic packages of printed wiring polyimide boards have been assembled and inspected using non-destructive x-ray imaging and optical microscope techniques. The assembled boards after first rework were subjected to extreme temperature thermal atmospheric cycling to assess their reliability for future deepspace mission environments. The resistance of daisy-chained interconnect sections was monitored continuously during thermal cycling to determine intermittent failures. This test data shows a limitation of these reworked CCGA 624 packages for various projects. This research has reported the reliability study of CCGA 624 packages down to –185 °C and up to +125 °C.
This work was done by Rajeshuni Ramesham of Caltech for NASA’s Jet Propulsion Laboratory. NPO-49083