Variation of processing conditions on warpage prediction of a plastic quad flat package (PQFP) is examined. Thermal mismatch between package constituent materials is the major cause of IC package warpage. To minimize the warpage problem, a thorough understanding of epoxy molding compound (EMC) properties with molding parameters is necessary as EMC is epoxy-based with time and temperature dependent viscoelastic properties. This paper first addressed the thermal characterization of encapsulating material. Degree-of-cure (DOC or β), coefficient of thermal expansion (CTE or α), glass transition temperature and shear modulus and G of the molded specimens were measured by various thermal analysis techniques. The glass transition temperature was shown to be a good and direct measure of the degree-of-cure. The CTEs and and were found to be decreasing functions of degree-of-cure. Viscoelastic EMC material models with DOC (i.e., dependent were formulated. Package warpage predictions against different processing conditions were performed via finite element analyses. Out-of-plane displacement measurements were performed on plastic quad flat package (PQFP) to validate the numerical results. Warpage prediction by the viscoelastic material model was found to agree with the measured data better than the thermoelastic one. For a given cured content, less warpage was found in packages molded at low temperature and longer molding time OR high temperature and shorter molding time.
Warpage of Plastic IC Packages as a Function of Processing Conditions
Contributed by the Electrical and Electronic Packaging Division for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received by the EEPD December 22, 1999. Associate Editor: M. Shiratori.
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Yeung , D. T. S., and Yuen, M. M. F. (December 22, 1999). "Warpage of Plastic IC Packages as a Function of Processing Conditions." ASME. J. Electron. Packag. September 2001; 123(3): 268–272. https://doi.org/10.1115/1.1349421
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