Deposition of Solder Pads on Metallized Ceramic or Organic Chip Carriers by Evaporation
Original Publication Date: 1985-Apr-01
Included in the Prior Art Database: 2005-Feb-18
Standard solder-ball (C4) bonding on metallized ceramic (MC) substrates requires dip-tinning to create C4 pads on the substrate. This method has numerous disadvantages, especially with new chip-carrier materials. Heat-sensitive or shock-sensitive multilayer ceramic or organic carriers can be cracked or warped when tinned with molten solder. Through-mask evaporation can deposit C4 pads on the chip carrier with excellent shape and height uniformity with minimal substrate heating. The evaporation mask is formed out of a refractory metal using standard photolithographic techniques. Through-mask evaporation of C4 pads is a common process for deposition on wafers, but has not heretofore been used to form C4 pads on chip carriers.