Ball grid array (BGA) components have been used extensively in the electronics industry for commercial and military purposes. Designing electronics with BGA components for space flight qualification presents unique challenges given the significant structural loading during launch, as well as the high-cycle thermal fatiguing often encountered in common low-earth orbits. The typical BGA consists of a thin square of plastic or ceramic material with hundreds to thousands of individual solder balls spaced in an array. The BGA is then attached to a printed circuit board using additional solder between the part and the board, or with simple reflowing of the solder balls themselves. For purposes of printed wiring assembly (PWA) improved signal routing, the optimal electrical location for the BGA is often near the center of the PWA. However, this location often coincides with the worst vibration-induced strain, as the center of the PWA flexes most under vibration. A careful balance must therefore be struck to determine the optimal overall location that maximizes layout design flexibility without compromising the reliability of the soldered connections. There has been a strong need to utilize these types of components on present and future programs within Division 15. To that end, this research effort was intended to evaluate two different BGA packages in support of this work.
A test PWA was manufactured and assembled with two each of the candidate BGAs. One of each was placed near the board center and the others near the board perimeter. The resulting assembly underwent vibration and environmental testing to validate the analysis. Thermal, environmental, and vibration requirements of the aforementioned programs, the General Environmental Verification Standard (GEVS), GSFC-STD-7000, and expected future applications were considered in the formulation of testing and analysis criteria. In the case of differing requirements, the more severe case was chosen to produce a test board design that would be most generally applicable for future designs.
The test board first underwent vibration testing and subsequently accelerated life thermal cycle testing. The smaller of the two types of BGAs passed vibration testing, while both larger parts failed. The program baselining the parts which failed has a lower vibration profile requirement than the profile tested in this research effort. To ensure the BGA was qualified for its specific application, a new part was placed on a spare board and tested again, using the applicable vibration profile. The part experienced no failures. This effort was completed by the project in parallel to the research effort.
After completion of the vibration tests, both test boards continued into the accelerated thermal cycling life test.
Neither type of BGA experienced failed solder connections after experiencing the number of cycles required by their respective programs. The test continued significantly beyond program requirements to gain additional information.
Both part types functioned normally for many additional cycles. Both parts have been qualified for their specific applications. This research effort provided valuable information and built confidence in the use of large factor BGAs for space applications. However, vibration loads in future projects should be carefully considered when baselining very large BGAs.