Stud-bump bonding technique onto an advanced organic substrate for MCM-Ls

This paper describes the result of our study that bare LSI chips are mounted directly onto the “ALIVH^TM” (any layer inner via hole) substrate by using Stud-Bump-Bonding (SBB^TM ) technique, which has been developed by us. The SBB^TM technique is an advanced flip-chip bonding technique, for high density Multi-Chip-Modules (MCMs), which can mount bare LSI chips directly onto substrates. The structure of the bonding portion is composed of Au bumps having two-stepped construction and conductive adhesives. The conductive adhesive is very flexible in bond, thus relaxing thermal and mechanical stresses. The ALIVH^TM substrate has been developed in our laboratory. It is a high density and high performance multi-layered printed wiring board with any layer inner via hole structure, via hole processing technology using a CO₂ laser and interconnection technology that employs conductive paste. We had good results for several reliability tests in the test vehicles of MCM-ALIVH^TM. Especially, in the thermal shock test, the increase of connecting resistance in MCM-ALIVH^TM was smaller than that of MCM-Ls which used ordinary organic substrates in stead of the ALIVH^TM substrate. The combination of SBB^TM technique and the ALIVH^TM substrate is promising for miniaturized, light-weighted, high speed (high frequency), and high quality in MCMs