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In a flip chip package (FCBGA), the presence of stress arising from the thermal mismatch between different materials is inevitable. It is a challenge for the packaging community to manage these stresses via careful selection of materials and design to achieve optimal performance and reliability of the integrated circuit. Finite Element Analysis (FEA) modeling for thermomechanical study is a widely...
In this work, a new empirical method is proposed to incorporate the initial substrate warpage into package stress simulation. As a first step, the bare substrate strip warpage characteristics were mapped. The out-of-plane displacements of the substrate strips were measured as a function of temperature using shadow moire technique. It was observed that the warpage values of the bare substrate vary...
We report board level stress tests of leadless QFN packages (pitch 0.5 mm) with focus on different application fields. We did temperature cycling tests, drop test, bend test, and power cycling tests, with special focus on the influences of board design and soldering technology. We performed the stress tests until end-of-life and determined the dominating failure modes. In our temperature cycling study...
Solder joint reliability during temperature cycling on board (TCOB) is a critical issue not only for BGA but also for quad flat non-leaded (QFN) type packages. On the latter, only a few studies are available in the literature. In this work a parameter study based on Robert Darveaux's model for BGA solder fatigue life prediction was done using full 3D FEA modeling with ANSYSreg. The target was to identify...
This paper compares the application of different constitutive material and fatigue models for lead-free (SnAg4.0Cu0.5) solder proposed by Schubert, Wiese, Dudek and Syed. The application of these models is demonstrated and results are compared with the experimental findings for different type of ball grid array packages, which are subjected to a controlled temperature cycling condition. In addition,...
We report a case study for the optimization of a flip chip based stacked die array test package. We demonstrate the importance of package substrate design and substrate thickness on the processibility and package warpage control. We found that for thin substrates copper balancing of the top and bottom die is crucial. We show the impact of flip chip die thickness and substrate thickness on the die...
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