Thermal Debonding: A Fundamental to Fanout Manufacturing

Fanout has been known to provide a more cost-effective packaging solution for advanced packaging alongside good electrical performance and flexibility, allowing multi-die and heterogeneous integration. This structure, however, has a typical process and material issue, namely die shift and warpage. Die shift is encountered several times throughout the reconstruction process and can be addressed by machine selection, process compensation, and possible design changes to allow more shift tolerance. Warpage, on the other hand, is a product of the reconstruction process, which is encountered due to the mismatch of the material properties. This is the difference in the Coefficient of Thermal Expansion between the epoxy mold compound and the silicon. Warpage is inherent to the structure resulting in manufacturing constraints in the succeeding processes. Thermal debonding is the last process step of the reconstruction flow and acts as a launchpad for RDL processing. This is where the warpage needs to be minimized to allow ease in production. Thermal debond is a fundamental process focusing on separating the wafer from the carrier. This, however, does not control the warpage. The enhanced thermal debond method must be done to not only seamlessly debond the wafer and detape the adhesive film without yield issue, it also minimizes warpage to a level that will allow wafers to run smoothly in the next machine.