Effect of PCB Pad Structure and PWB Build-up Layer on Solder Joint Life under Thermal Cycling and Drop Condition

Rapid development of hand-held products has created new reliability concern, such as ability to withstand drop or shock condition. Different selections or combinations of solder alloy, surface pad finish, pad design have been studied to improve such reliability. However, the combination of enhancing drop reliability leads deterioration of thermal fatigue reliability. In order to find a best combination to satisfy both drop and thermal fatigue reliability, FBGA package with various new ball pad structures was evaluated under drop or thermal cycling. The most influence factor for thermal cycling reliability was PWB build-up layer configuration. NSMD pad definition type with VOP pad structure showed the significant improvement of drop reliability.