Prof. Han’s Group is Developing an Innovative Warpage Prediction Tool

The Packaging TAB (Technical Advisory Board) of SRC (Semiconductor Research Corporation) https://www.src.org/about/ has selected Prof. Han’s proposal “Innovation of warpage prediction for transfer molding and compression molding processes” for funding.

The warpage issue inherently exists and has been increasingly important ever since EMC became a part of advanced interconnect systems of various heterogeneous integration solutions, including FO-WLP and embedded technologies, where signal redistribution layers are fabricated on EMC. For the past couple of decades, a considerable amount of time and effort has been invested to enhance the predictability of warpage. Yet, even the models, “verified” by warpage measurement tools, do not predict accurately the warpage of different packages molded by the same EMC. In fact, good agreements of warpage between predictions and measurements are possible even when the properties of EMC are not correct and/or some critical properties of EMC are missing. Two possible reasons for this paradox have been identified, which are the motivation of Prof. Han’s proposed study.

The first reason is the requirement for predicting “absolute” warpage, and the second one is the incorrect assumption used in the current practice of numerical analysis - the assumption of time and temperature “independent” bulk modulus (K). As illustrated in the figure below, the accurate prediction of warpage after molding processes could not be possible without using the cure extent-dependent viscoelastic bulk modulus and the effective cure shrinkage (ECS) value, because EMC deforms continuously “only” during compression molding.

Successful completion of this three-year study (Jan. 2022 to Dec. 2024) will provide a much-needed tool to enable the industry to accurately predict the warpage right after molding as well as after post-mold curing processes. Please contact Prof. Han at bthan@calce.umd.edu if you are interested in this activity.

Published October 25, 2021