Assembly of MCM thermal solution utilizing individual heat spreaders

Some recent IBM UNIX servers use multi-chip modules (MCMs) with multi-core processor chips with very high power densities, requiring aggressive thermal solutions. The thermal solution includes flip chips with individually attached heat spreaders. Because of the difficulty of reworking the thermal solution, and the high value of the module at the time the cooling solution is assembled, very high assembly yields were required. This drove new technologies, and new processes to enable assembly of highly efficient cooling structures with very high yields. This paper addresses the challenges of assembling the heat spreader cooling solution, and describes how these challenges were overcome