| In this paper, three types of multilayer substrates of MCMs(multichip Modules)──LTCC, MCM-C and MCM-D undergoing temperature cycles from -55℃ to +125℃ and thermal aging at +125℃. We measured the contact resistance of via holes, the metal film resistance, the capacitance as well as the sheet resistance of samples before and during environmental test. Through variations of these parameters, this paper summarizes the degration pattern of via hole, metal film and dielectric film under thermal stress. So, all-sidely evaluation on technological level and long-term reliability of different substrate is given. In the end, failure analysis is made on the unqualified and failed samples. The failure patterns and failure mechanisms are also given. More over, some improvement measures are proposed. Thus, a series of practical method for designing test structure, setting up automatic measurement system, collecting test data, dealing with statistical data as well as performing microanalysis is proposed.
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