The quest for thin, low profile packaging solutions for mobile devices and cost reduction with improved performance continues to drive the development of new packages. The development of the fan‐out wafer‐level package (FO‐WLP) is the latest industry trend. There are an increasing number of suppliers for FO‐WLP and a growing number of applications. This chapter examines the market trends and drivers for package adoption and the technology trends for FO‐WLP.
2.2 FO‐WLP: A Disruptive Technology
An FO‐WLP is a substrate‐less package that typically uses a carrier and mold compound to create a format on which single or multiple dies are placed and a redistribution layer (RDL) is used to “fan out” the inputs and outputs (I/Os) to create a package. When Infineon developed its FO‐WLP, the embedded wafer‐level ball grid array (eWLB), one of the drivers was to reduce package cost by removing costly parts of the package including the substrate and the flip‐chip bump. The absence of a substrate makes FO‐WLP a disruptive technology. Thin film metallization is used for interconnect instead of bumps or wires. Infineon’s FO‐WLP has the active side of the die placed facedown in the process and so is often referred to as a face‐down FO‐WLP. In the case of a face‐up process, the die has a thick Cu post. Figure 2.1 shows a face‐up and a face‐down option.