Two controlled batches of PCBs with 100 each were used in the controlled experiment. The first batch of PCBs underwent the HASS and power cycles processes before they were delivered to the system configuration. The second batch of PCBs, after received from subcontract manufacturers, went directly into the system integration without going through HASS and power cycle tests. To minimize customer usage effects, these boards were randomly mixed and configured into new systems to be shipped for different customers. The reliability performance of these PCBs can be easily tracked by a unique series number assigned to the board.