Warpage Prediction of Electronic Underfill Components During Curing

• Main Author: Lindblom, David
• Format: Bachelor Thesis
• Language: English
• Published: Umeå universitet, Institutionen för fysik 2021
• Subjects: Warpage; viscoelastic; Physical Sciences; Fysik; Dyna; Piteå
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-190888

To ensure the shelf life of a semiconductor, the integrated circuits are usually embedded in an epoxy molding compound (EMC) to shield it from stress and corrosion. The EMC is a viscoelastic material and is categorized as a thermoset. Working with viscoelastic material appose a challenge due to the cure-induced warpage. Warpage is a deformation that reduces stress resistance and can also make for assembly issues. Being able to predict the warpage accurately is an essential part of the electronics industry. To simulate the warpage, the finite element method is usually used. The Research Institutes of Sweden (RISE) in Piteå, which focuses on composites, have created a solver and corresponding material definition for simulating the curing process of a viscoelastic material. In this thesis, the solver created by RISE was investigated to see how well it could predict the warpage during the curing of an EMC. The investigation consisted of reproducing the simulating conducted by Lin et al. in the article "Modeling and Characterization of Cure-Dependent Viscoelasticityof Molded Underfill in Ultrathin Packages" where the curing of an ultrathin flip-shipChip-Scale Package (fcCSP) was simulated. The result will be reproduced using the simulating program LS-Dyna and both the RISE material definition and an build-in material definition will be simulated to see the difference. From the investigation, we could conclude that although the result from the article was unobtainable, the RISE model could predict the warpage more accurately which shows the importance of the cure shift factor. The investigation also found that the RISE model has some implementation errors for the stress-strain calculations in the RISE model. In conclusion, the RISE model was able to predict the warpage in a desired way, but more studies need to be created to ensure the model’s accuracy for the correct warpage magnitude.