A Study of Efficiency of Total Volume of Mold Resin for Warpage in COW Process

We have studied the warpage trends as a function of the total volume of mold resin in the Chip-on-Wafer (COW) process. By using face-down die bonding onto a waffle Si wafer, the remaining mold resin is reduced due to the structure of the waffle wafer and the additional thinning capability provided by face-down die bonding. This method results in a one-fourth reduction in warpage compared to the conventional face-up die bonding onto the bare Si wafer. This paper describes the changes in warpage throughout the COW and molding processes, both bare wafer and waffle wafer, and highlights the advantages of face-down die bonding.