Development of Fan-In WLP with mechanical protection and dynamic warpage characterization of eWLB

eWLB (embedded Wafer Level Ball Grid Array) is a fan-out wafer level packaging (FO-WLP) technology, its core process is the encapsulation of active and/or passive components in epoxy mold compound (MC) acting as both the physical support of the components and the base of the fan-out area accommodating the second level connections. One eWLB solution is FIMP (Fan-In WLP with Mechanical Protection) technology that consists in the embedding of the silicon dies but with a very thin layer of mold compound, which actively protects the chip sides and backside, the second level interconnections are completely contained within the die area. This solution offers fan-in components a reliable option as mold compound layer increases package reliability, without compromising package size. This paper outlines the development and implementation of FIMP, and its challenges. Due to the very thin side walls of epoxy mold compound utilized in the FIMP technology as well as the thin overmold coverage implementation of finer filler mold compounds. Understanding the implications of the transition from relatively low silicon occupation ratios (SOR) to very high SORs is fundamental to the implementation of the FIMP technology. How this transition impacts the warpage during reflow soldering provides an insight into the behavior during final component assembly and over an extended temperature range. To this end three sets of package configurations were evaluated. The first set studies identical packages in terms of SOR and silicon volume ratio (SVR) but focusing on the transition from standard to finer filler mold compound. The subsequent data set has the purpose of understanding the impact of the increase from a standard low SOR typical of eWLB technology to a relatively high silicon occupation in an identical package without yet achieving the SOR of a true FIMP package. Finally these ingredients come together in a FIMP package with extremely high SOR (>95%) and using a fine filler epoxy mold compound. In order to replicate the thermal profiles that the devices endure, an Insidix Topography and Deformation Measurement (TDM) system was used. The TDM device is used to measure the 3D deformations throughout different thermal conditions non-destructively. Tests showed very promising reliability results for FIMP package as well as component warpage for all eWLB configurations, with little volume variations after submission to different thermal conditions.