Comparison of SMT, COB, and MCM technologies on a 68000 CPU

Military radlocommunication equipments incorporate more and more powerful digital functions with components of various sizes and a few VLSI circuits with now more than 200 I/Os. At board level, packaging has to be compact, light and at the best possible cost. We therefore analyzed the miniaturization effect achieved by mounting integrated circuits in SMI) packages and bare chips for a number of inputs/outputs in the range from 16 to 300. Three solutions were then tested on a 68000 architecture : board with SMDs mounted on both sides, high density MultiChip Module, and board with SMIDs on one side and VLSI mounted in COS technology on the other side. The measured performances as regards compactness, weight, power consumption and cost show the interest of a solution combining SMDs and COB and the requirement of a substrate cost reduction in the MultiChip Module.