A user's view of MCM-D/C packaging: is it worth the trouble?

In todays packaging environment, we are constantly faced with an array of technology choices for our applications. When new technology is involved there is almost always the point in the development project when the designers ask themselves, "Is it worth it?" or "Did we make the right choices?" It is from this process we learn and look for more efficient ways of doing business in the future. This paper describes why we chose Multi-Chip Modules with Thin-Film wiring (MCM-D on C) for our latest AS/400 processor package. The package consists of 5 layers (2 power, 2 signal, 1 mounting/repair) of thin-film metal applied to the surface of a 30 layer ceramic substrate. The paper specifically addresses design aspects of this module such as the electrical, thermal, mechanical requirements and why this version of MCM packaging was necessary. Included is a discussion on what advantages (real and wished-for) were derived from utilizing the thin-film wiring. A comparison is provided of the actual package performance to the design requirements from the application perspective. The paper also addresses such topics as design methodology, noise analysis (power and signal), test, concurrent process development, and debug/repair strategies that burden the development process of using MCMs.