Testing and evaluating the quality-level of stratified multichip module instrumentation

In this paper, approaches to testing and evaluating the quality-level (QL) of multichip module (MCM) instrumentations are proposed. A MCM is generally composed of a number of sets (or strata) of chips with different Known-Good-Yields (KGYs), so-called stratified, since each stratum is procured from a separate manufacturer. A stratified technique is proposed for testing MCM instrumentations. The proposed testing approach is accomplished in the presence of uneven known-good-yield (KGY) for MCMs consisting of different sets (or strata) of chips. This approach referred to as the lowest yield-stratum first-testing (LYSFT) considers the unevenness of KGY between strata for testing the chips and improving the QL. For comparison purposes, exhaustive testing (ET), random testing (RT) and random stratified testing (RST) are also evaluated by using a Markov-chain model. A Markov-chain model is used to analyze the quality-levels of these testing approaches and is solved analytically in O(SN3) for the LYSFT (where S is the number of strata and N is the number of chips in the MCM). A cost model is proposed and shown as figure of merit and shown to relate the defect-level with the number of tests performed. Parametric results show that the LYSFT dramatically outperforms RT and RST for improving the quality-level. A considerable reduction in tests can be achieved by the LYSFT at a very small loss in quality-level compared with ET. Based on the proposed cost model, it is also shown that the LYSFT is the most cost-effective strategy.