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

In this paper, approaches to measuring the quality-level of multichip module (MCM) instrumentations are proposed. The 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. This characteristic of MCM is employed to enhance the performance of the testing process thereby assuring the quality-level of MCMs. A stratified technique is proposed for testing MCMs. Its advantages are an improvement in quality-level and cost-effectiveness. The proposed testing approach is accomplished in the presence of uneven 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. 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 a proposed cost model, it is also shown that the LYSFT is the most cost-effective strategy. The validity of the proposed approach is further proved through Monte Carlo simulation.