Effective Thermal Solution via Wafer Level Packaging Materials

Since the first Fan-out Wafer Level Packaging (FOWLP) was introduced in 2001 by Infineon, lots of technical advancements and studies related to this technology have been reported, but thermal studies have not been reported due to their thermal favorable through-silicone vias (TSVs). The constant advancements of Wafer Level Packaging (WLP) lead to reach the maximum capacity of the thermal solutions provided by TSVs. As a result, a few thermal solutions through the structural changes of a package have been reported recently. However, the approach via a thermal conductive encapsulant has not been introduced for large area molding applications. This thermal solution via the concept has been studied and developed in our lab recently. Especially, Liquid molding compounds (LMCs) have been focused on due to their manufacturing history and well-established processes for 3D, 2.5D, and FOWLP. The high thermal conductive LMCs for WLP are dissimilar and even more challenging than the conventional epoxy molding compounds (EMCs) in terms of the fundamental properties, the warpage, and the thermal conductivity (K) of high K encapsulants for WLP and the process standards of WLP.For the warpages of WLP, the cure temperature and the degree of cure have been adjusted. The reduction of cure temperature and the degree of cure lowers the thermal shrinkage and modulus of LMCs respectively. It is able to meet the requirements of warpages in WLP steps. Next, the key challenge of these compounds is to load the maximum amount of high thermal conductive fillers into the system because heat dissipates mainly through high K fillers, a higher heat conductive material. The conventional high thermal conductive materials can load fillers up to 95 wt% and easily surpass 7 W/mK according to the recent experimental reports. Unlike these conventional materials, the development of high K LMCs for WLP are not easily achieved because the fundamental properties, warpage, and thermal conductivity have to be met at the same time. Along with these, other qualifications, including workability, reliability, and properties, must be satisfied with the process standards of wafer level packaging. Detailed experiment procedure, data, test results of this compound will be presented here.