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The increasing complexity of today's Printed Circuit Boards inevitably leads to higher failure rates at the assembled board and product levels. Electrical testing of PCBs at the bare board level always results in early identification of failures, and thus in increased production economies. The escalating costs to identify faults at various levels of the PCB manufacturing and assembly process are discussed and illustrated. The typical PCB spectrum of faults, including contamination, shorts, opens, and holes is discussed, along with reliable methods of fault removal. In addition to the economic factors such as capital equipment cost, programming, fixturing, and operating costs, several technical factors are discussed and illustrated. These include test comprehensiveness and test speed. Since fault coverage is directly proportional to the measurement capability of the test equipment, the effects of measurement threshold on fault coverage and the resultant failure rates at the assembled board and product levels are discussed and illustrated. The importance of using the standard 100 megohm threshold is also discussed and illustrated.

As SMT circuit boards continue to increase in complexity, the PCB manufacturer—in order to stay alive in an increasingly competitive market—will be forced to produce boards of the highest quality to meet marketplace performance standards. In addition, he will have to produce them economically at a profit. The complex board of today will be a subsystem tomorrow. It will certainly contain finer features, more embedded resistors, and will even exhibit analogue‐like and RF‐like features plus even more sophisticated networks. All of these developments are expected to have a strong impact on electrical testing techniques. This paper discusses the problems of increasing yields by means of better process control and higher quality testing for a changing spectrum of faults. The effects of both latent and immediate PCB faults are examined for various grades of products, including low grade commercial, commercial, ground‐based military, high rel. commercial, and high tech. military and commercial. Illustrations and tables are provided showing the impact of fault detection on product quality as well as the economic impact achieved for various levels of product quality by means of software SPC (statistical process control). The most important issue facing the PCB manufacturer in the 1990s is certain to be quality of product. This paper outlines strategies for the manufacturer to improve his process through improving the quality of electrical test and the provision of highly accurate fault data as well as the highest possible fault coverage.

The increasing level of integration in PCB technology demands from the designer a new level of sensitivity to high electrical field problems and to the degradation processes that may be involved. High electrical fields interacting with thermal and mechanical stresses could lead to the growth of ‘latent defects’, not easily identifiable during final stage acceptance tests, that could lead the PCB's failure during service. The paper discusses degradation mechanisms which can lead to dielectric failure, together with first results relevant to a wider research project regarding identification of latent defects in PCBs and the development of new test procedures.