The main trends in consumer electronics are increasing performances of their products and a reduction of the costs. These trends lead to an ongoing integration on package level which leads to a decreasing size of the solder contacts. This goes along with a higher sensibility to thermal-mechanical stress and void formation due to electromigration (EM). Against this background copper pillar bumps were introduced, because they combine the robustness of metal wire bonds with the low bonding pressure of reflow soldering.Experimental results have shown a longer lifetime of Cu pillar bumps during EM tests, but a continuative analysis is still needed for design optimization. Against this background a finite element analysis (FEA) was performed to compare the EM induced mass flux in conventional solder bumps and in two different designs for Cu pillar bumps. The thermal electrical simulations were performed with ANSYS ® . Afterwards a user routine was used to calculate the EM induced mass fluxes and mass flux divergences. The simulation results are used to identify possible reasons for the increased EM per f ormance o f Cu p ill ar bumps and t h ey enab l e t h e identification of preferable designs.
The reduction of package and chip size by the need of cost reduction on one hand and the need of high voltage metallization on chip for power applications on the other hand the thermal electrical-mechanical management concerning the reliability becomes more and more critical. Breakdown failures due to mechanical stress, moisture uptake, migration effects caused by current crowding, temperature gradients due to Joule heating and stress gradients and intermetallic phase growth have an increasing importance. With the help of simulations the weakest links as well as locations with high thermal electrical and mechanical loads can be determined. This will be shown for selected examples.
Commercial of the shelf (COTS) SRAMS were investigated by measurements and simulation in terms of radiation hardness. For the simulations the GEANT4 tool was used. With GEANT4 it is possible to determine the different particles generated by the applied energy as well as the radiation source. It was found that the single event upsets (SEU) is related to the radiation energy, technology node and react differently for the investigated SRAM. Furthermore a possible correlation between the generated particles and the SEU was found.
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