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A new integrated circuit packaging structure was needed to support the new 90-mm multilayer ceramic modules, known as Thermal Conduction Modules (TCMs), used in the IBM 3081 computers. The structure developed eliminates one level of packaging (the card level) and allows up to nine TCMs to be plugged directly into a large multilayer printed-circuit board using a new zero-insertion-force connector system. The board has 18 internal circuit planes for signal and power distribution and accommodates new signal cabling, power bus, terminating resistors, decoupling capacitors, and cooling hardware, forming a packaged unit of up to a quarter million logic gates and half a million bits of memory. This paper focuses on the detailed design of the printed-circuit board and on its signal and power transmission characteristics.
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