The evaluation of solder and circuit board materials for small satellite solar cell arrays

Body mounted germanium substrate solar cell arrays form the faces of many small satellite designs to provide the primary power source on orbit. High efficiency cells are made affordable for University scale satellite programs as triangular devices trimmed from wafer scale solar cells. The smaller cells allow the array designs to pack tightly around antenna mounts and payload instruments. We are investigating the reliability of solar cells attached to FR-4 and carbon core laminate printed circuit boards. FR-4 circuit boards have significantly higher thermal expansion coefficients and lower thermal conductivities than germanium; whereas carbon core laminates can be selected to more closely match the device substrate. We are also comparing various solder pastes and cleaning processes for array assembly. Storage, vacuum exposure, thermal cycling and vibration testing will be used to compare the survivability and performance of the solar arrays.