Method to improve isolation of an open net fault in an interposer mounted module

Abstract

A multi-chip module (MCM) assembly has two modules interconnected by respective interposers and a printed circuit board, and diagnostic logic within the modules uses the principal of signal reflection to located any open fault in the circuit path across the interposers. A first test signal is sent from module to the other and a determination is made as to whether any reflected signal represents an open fault of the circuit path at either of the interposers. If a reflected signal is received during a predetermined time, the diagnostic logic concludes that a single open fault exists only at the far interposer. If no reflected signal is received then the diagnostic logic concludes that there is at least one open fault at the near interposer, and the second module runs a similar test to check to see if both interposers have failures.