Warpage of flat packages is partly due to chemical shrinkage of the molding compound during cure and partly due to differences in thermal contraction in the subsequent cooling stage. The latter effect is relatively easy to incorporate in numerical simulations but the cureinduced shrinkage effect is not and is therefore often neglected in warpage simulations. Recent validation studies however showed that it is essential that both effects are taken into account. In this paper we develop explicit analytical expressions for the cure-induced residual stresses and warpage of a simple bilayer construction. We do this by assuming that curing always takes place above the molding compounds glass transition temperature such that the material is in its rubbery state and that viscoelastic effects are absent. The analytical warpage model was shown to give results comparable to numerical calculations using a fullly cure dependent viscoelastic material model. Furthermore, for the first time accurate analytical expression for the Stress Free Temperature and Stress Free Strain are obtained. With these expressions the effect of cure shrinkage on residual stresses can easily be incorporated in existing (numerical) stress analyses without the need of using extensive cure dependent viscoelastic material models.
Original languageEnglish
Title of host publicationProceedings of the 12th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2011, 18-20 April 2011, Linz, Austria
EditorsLJ Ernst, GQ Zhang, WD van Driel, P Rodgers, C Bailey, O de Saint Leger
Place of PublicationLinz, Austria
PublisherIEEE Society
Pages1-4
Number of pages4
ISBN (Print)978-1-4577-0105-4
Publication statusPublished - 2011
EventEuroSimE 2011: 12th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems - Linz, Austria
Duration: 18 Apr 201120 Apr 2011
Conference number: 12

Publication series

Name
PublisherIEEE

Conference

ConferenceEuroSimE 2011
CountryAustria
CityLinz
Period18/04/1120/04/11

    Research areas

  • conference contrib. refereed, Conf.proc. > 3 pag

ID: 1643703