Thermal and moisture induced stressing effects of RF power amplifier modules

The trends in RF power amplifier (RFPA) modules for handsets are optimization of active device technology, circuit topology and packaging to enhance cost, size, performance, and ease of implementation. For the package in RFPA module manufacturing, device-to-board attach solder reflow condition and moisture sensitivity level (MSL) are the most challenging areas for further improvement in thermal management due to "lead-free" application which causes catastrophic failure by high temperature application. In consequence, we have been faced with industrial requirements to improve both MSL and reflow temperature without any catastrophic phenomena such as solder extrusion and solder flow in RFPA modules. This paper discusses various considerations to define critical factors that will affect thermal and moisture induced stress in RFPA modules in long term reliability assurance at the package design stage. On the analysis of severe failure mechanisms in RFPA modules, we identified the cross effects on various characteristics of moisture induced package failures caused by the alloy composition of component terminations, behaviors of component attachment materials for active/passive, and substrate metallization with its own material. Also, best raw material combinations and critical consideration factors for package integrity of RFPA module with MSL reliability are discussed.