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Materials mechanics and mechanical reliability of flip chip assemblies on organics substrates

 
: Schubert, A.; Dudek, R.; Michel, B.; Reichl, H.; Jiang, H.

:

IEEE Components, Packaging, and Manufacturing Technology Society; International Microelectronics and Packaging Society -IMAPS-; Georgia Institute of Technology, Atlanta:
3rd International Symposium on Advanced Packaging Materials - Processes, Properties and Interfaces 1997. Proceedings
New York: IEEE, 1997
ISBN: 0-7803-3818-9
pp.106-109
International Symposium on Advanced Packaging Materials <3, 1997, Braselton/Ga.>
English
Conference Paper
Fraunhofer IZM ()
finite element analysis; flip-chip devices; plastic deformation; reliability; scanning electron microscopy; Soldering; thermal stress

Abstract
This paper demonstrates a combined approach of numerical analysis and experimental investigations to study the mechanical reliability of flip chip solder joints. The effect of various design parameters like bump geometry, "soft" and "hard" underfill, and used solder mask on the thermal fatigue life of solder joints is discussed. Since special attention has been directed towards Flip Chip on Board (FCOB) assemblies, constitutive properties of polymeric and solder materials are discussed in detail. The solder is modeled using a nonlinear constitutive law with time dependent (creep) and time independent plastic strains. Furthermore, material testing shows that the underfill and solder mask materials might be considered as linear viscoelastic with temperature time shift properties. Thermal mismatch between the materials assembled is often the main reason for thermally induced stresses. Thermal cycling (125 degrees C...-55 degrees C...125 degrees C) is therefore the load generally used in t he 3D non-linear finite element analysis. Calculation results of the solder bump deformation due to temperature changes are accompanied by experimental deformation analysis. The used MicroDAC method is based on algorithms of local object tracking in images obtained from electron scanning microscopy. The measured deformation fields were utilized for proper materials selection and processing, as well as for verification of finite element analysis.

: http://publica.fraunhofer.de/documents/PX-22979.html