The Development of a Low Cost Wafer Level Bumping Process

This paper details the development of hardware modifications for a standard stencil printer that subsequently permit the placement of solid solder spheres onto wafers and other substrates. The developed process provides a low cost method for the bumping of wafer-level packages. Test results for the bumping of both 6 and 8" wafers with spheres sizes as small as 250 microns and pitches down to 400 microns are presented.