Advanced Viscoelastic Material Model for Predicting Warpage of a QFN Panel

Conference paper (2008)

Authors

J de Vreugd Computational Design and Mechanics - Mechanical, Maritime and Materials Engineering
K.M.B. Jansen Computational Design and Mechanics - Mechanical, Maritime and Materials Engineering
A. Xiao Computational Design and Mechanics - Mechanical, Maritime and Materials Engineering
L.J. Ernst Computational Design and Mechanics - Mechanical, Maritime and Materials Engineering
C Bohm External organisation
A Kessler External organisation
H Preu External organisation
M Stecher External organisation
Research Group
Computational Design and Mechanics (Mechanical, Maritime and Materials Engineering) (TU Delft)
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Published Date

2008

Language

Undefined/Unknown

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Faculty

Mechanical, Maritime and Materials Engineering

Department

Precision and Microsystems Engineering

Research Group

Computational Design and Mechanics

Abstract

Warpage is a critical issue for a QFN panel molding process. Much work was done in the past to predict the warpage of a package during cooling down from molding temperature. However, until now, warpage could not always be predicted well, even if the viscoelastic behavior of the molding compound is taken into account. It was for example observed that the cooling velocity affected the warpage after cooling down. Because of this reason, the mechanical behavior of the molding compound was investigated in more detail. In this research, the mechanical properties of the molding compound are determined. It turned out that the properties are highly dependent on time and temperature. A complete viscoelastic model of the model compound is achieved by combining DMA and dilatometric test results. The model is implemented in the finite element software ABAQUS. In this study, our advanced model is compared with elastic calculations which are normally done.
A validation experiment is performed in which simulation results are compared with experimental warpage data of a double layered beam, consisting of a layer of molding compound and a layer of silicon. This beam is cooled down from a temperature above Tg to room temperature with different cooling rates. In the meantime warpage is measured and compared to simulation results. Finally, the advanced material model is used for calculations on a QFN-panel.