DOUBLE STENCIL WAFER BUMPING
Original Publication Date: 1999-Jun-01
Included in the Prior Art Database: 2002-Aug-14
As I/O count increases and individual die designs are made smaller, it becomes increasingly important to reduce the pitch of solder bump con- nections. Motorola transfered C4 (evaporated) bump technology from IBM. This is a very mature, robust, and reliable but expensive wafer bumping process. Motorola has therefore invested several million dolllars to develop a lower cost wafer bump- ing process using electroless Ni and Au for the Under Bump Metallurgy (UBM) and a stencil print- er to print solder paste which is then processed through a reflow oven to form the solder bump.