Effect of critical properties of epoxy molding compound on warpage prediction: A critical review

For the past couple of decades, a considerable amount of time and effort has been spent to enhance the predictability of warpage of semiconductor packages encapsulated by epoxy molding compound (EMC). With advanced computational mechanics techniques and computing hardware, one can simulate almost any kind of packages. Thermo-mechanical properties required for numerical predictions, including the coefficient of thermal expansion (CTE), the glass transition temperature (Tg), and the temperature and time-dependent viscoelastic properties, are routinely measured by commercial tools such as thermo-mechanical analyzer (TMA) and dynamic mechanical analyzer (DMA). In addition, temperature-dependent warpage can be measured readily using commercial tools based on shadow moiré and digital image correlation (DIC). In spite of this considerable effort, accurate prediction remains a challenging task. EMC typically occupies a large portion of package volume, and thus plays a major role in package warpage behavior. This review paper examines the effect of critical EMC properties on warpage behavior. Based on the data and the analyses reported in the literature, the paper addresses three potential causes that make the prediction still difficult, and discusses what should be done to bring the prediction capability to a desired level.