Investigation on the Flexural Modulus of Silicon Dies to Improve Die Mechanical Modeling Accuracy

Mechanical modeling of integrated circuit (IC) dies is commonly performed using the mechanical properties of the bulk silicon material. However, modeling results such as die deflection and the actual results were observed to have significant difference. This paper discusses the investigation done on the flexural modulus of actual IC dies used in package assembly manufacturing. Results were then compared with the modulus of the bulk silicon die or mirror die. The measurement of flexural modulus was done using the standard 3-point bend test. It was found out that the flexural modulus of the actual IC die is significantly lower than the flexural modulus of the bulk silicon or dummy die. Even with the actual IC die, the flexural modulus of the active side is also lower than the back side. From this study, it can be concluded that mechanical modeling involving IC dies could be improved by characterizing the properties of the actual die used. The common practice of using the properties of the bulk silicon die in mechanical modeling would not provide accurate results.