Development of low cost, highly reliable CSP using gold-gold interconnection technology

A low cost, highly reliable CSP (Chip Size Package) named T-G/sup 2/BGA (tape gold-gold gang bond BGA), has been developed for compact, and light memory devices' package. T-G/sup 2/BGA has a structure that connects a chip and an interposer using gold-gold interconnection technology, which uses thermo-compression flip chip bonding. We studied the ways to interconnect gold stud bumps on chip and gold plated pads on tape metallurgically and succeeded in realizing a highly reliable package. T-G/sup 2/BGA can realize fan-in type, real chip size, package, and fan-out type package. For the fan-out type, sidefill resin or support ring is formed on overhang tape for solder ball coplanarity. Using TEG (test element group) samples, we selected the most suitable materials and optimized flip chip bonding conditions. Consequently, 60 pin fan-in type package was fabricated under optimized conditions using selected materials and memory device, and good reliability test results were obtained. On the other hand, 60 pin fan-out type package was fabricated with optimized sidefill resin, which showed good solder ball coplanarity and solder joint reliability. The gold stud bumps and gold pads interconnection technology is considered to be low cost, highly reliable and more suitable for CSP.