Encapsulation process development for flexible-circuit based chip scale packages

The ultimate driving forces for the development of small form-factor chip scale packages (CSPs) are the market demands for small, light and high performance products. The flex-based /spl mu/BGA technology has been a very successful package format, and tremendous efforts have been implemented in the process development for the technology. In this article, three flex-based chip scale packages (based on patented /spl mu/BGA technology) will be discussed. The focus will be on the encapsulation process development. Because of the unique package structures and material sets used in the flex-based CSPs, various encapsulation challenges were raised. The encapsulation solutions are compared and discussed for each type of flex-based /spl mu/BGA technologies, including the dispensing pump technologies, material characterization, process characterization and optimization. Based on the evaluation results, type C /spl mu/BGA technology is recommended for its simple assemble process flow, balanced protection on beam leads and solder ball joints and shorter manufacturing cycle time as well.