A new designed trench structure to reduce the wafer warpage in wafer level packaging process

Wafer warpage in wafer level packaging process poses threats to wafer handling, process qualities, and can also lead to unacceptable reliability problems. With larger diameter wafer adopted, this issue becomes more serious. In the paper, a new designed trench structure was introduced in WLP process to reduce the final wafer warpage. Both experiment and simulation methods are used to investigated the effect of the trenches on the wafer warpage. The result indicates that, by forming deep trenches, the stress of individual dies is decoupled and the total the wafer warpage will be decreased. The effect of the geometry of these trenches on the mechanical behavior of the wafer was further studied by simulation.