Evaluation of die coating materials for chip-on-board technology insertion in spaceborne applications

Chip-on-board (COB) packaging technology has become increasingly popular for miniaturization purposes in high-reliability applications such as spaceborne electronics. It eliminates the hermetic package weight, permits the use of conventional soldered devices on an organic substrate (MCM-L), and supports rework. These characteristics provide the much needed flexibility to support a faster, better and cheaper electronic design. Miniaturization of spaceborne hardware can lead to improvement in performance and reliability as well as to cost savings. The non-hermetic nature of COB requires a careful selection of coating materials and a well planned process to provide protection against moisture ingress and contamination from the surrounding environment. This paper presents a study that evaluates the effects of various die coating materials on bare dice and the wire bonding process. It includes temperature cycling and the bias humidity test results on die coating materials as the basis for the selection of the most suitable encapsulant material for spaceborne applications.