IWLPC (Wafer-Level Packaging) Conference Proceedings


EXPLORATION OF MIGRATION AND STRESS EFFECTS IN POPS CONSIDERING INHOMOGENEOUS TEMPERATURE DISTRIBUTION

Authors: L. Meinshausen and K. Weide-Zaage
Company: Leibniz University Hannover
Date Published: 10/11/2010   Conference: IWLPC (Wafer-Level Packaging)


Abstract: In consequence of the continually shrinking the electronic devices three dimensional packaging was developed to place the rising number of features in a shrinking amount of space. A higher contact density leads to finer ball grid arrays, shrinking ball diameters and smaller traces. Meantime the dimension of the solder joints is reduced to several micrometers and new reliability risks of the contacts, like electromigration induced void formation or IMC growth, have to be considered. Previous stress tests at different temperatures showed a big influence of void formation on the lifetime of packages. Simulations show that current crowding is a major reason for void formation in the solder joints.

Electromigration or temperature cycle tests are performed in ovens with a constant ambient temperature. Previous simulations based on homogenous temperature fields. During this work thermal- electrical and thermal-mechanical simulations with inhomogeneous temperature fields, caused by the heat loss of the mounted ICs, were performed. Simulations with rising ambient temperatures were also performed. Based on the thermal-electrical results the electromigration induced mass fluxes and mass flux divergences were calculated with user routines. The simulations include a homogenous heat loss all over the ICs surfaces and a hot spot near to the bump chain.

Keywords: Bump, electromigration, void growth, reliability, heat sources



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