Parylene as a Novel Packaging Material for Adhesive Bonding, Flexible Electronics and Wafer Level Packaging

Advanced packaging technologies are the main driver for the growth of the packaging market. However, to enable them, new materials with improved properties are crucial. Parylene refers to the thermoplastic polymer family of Poly(para-xylylene), which unites an outstanding combination of excellent properties. This study aims to present an overview about recent research with respect to the usage of Parylene for packaging and integration. This includes the usage of Parylene for adhesive wafer and chip bonding, the realization of ultra-thin flexible circuit boards as well as for wafer level packaging. For bonding, Parylene can be used as an adhesive. Doing so, the different Parylene types address different temperature ranges between $280^{\circ}\mathrm{C}/300^{\circ}\mathrm{C}$ (Parylene C) and $420^{\circ}\mathrm{C}$ (Parylene N) / $430^{\circ}\mathrm{C}$ (Parylene F) and provide excellent bonding strengths, i.e. $(38.0\pm 7.6)$ MPa tensile strength and $(85.5\pm 11.0)$ MPa shear strength. Furthermore, a new technology for the realization of ultra-thin printed circuit boards (PCB) based on Parylene was developed. These PCBs use Parylene as a substrate, a dielectric as well as an encapsulation layer and feature multiple metallic redistribution layers at a total thickness of only 20 $\mu \mathrm{m}$ or even less. Advanced and wafer level packaging based on Parylene can be achieved by combining the results for Parylene adhesive bonding the ultra-thin flexible Parylene PCB. Doing so, different approaches are discussed.