The use of HALT to improve computer reliability for point-of-sale equipment

This paper describes a manufacturer's use of HALT (highly accelerated life test) to help identify the root causes of multiple, intermittent, and complex problems with certain personal computers (PCs) as used in point-of-sale (POS) equipment. In addition to identifying the root causes of "forced" hardware problems by means of these special and severe environmental tests, the paper describes attempts to understand the relationships between the test failures and the experienced factory and field problems. Although the tested PCs have been primarily used in point-of-sale equipment, their hardware is very similar to that of ordinary PCs, so the paper's results are applicable to the average PC user. The paper has three basic conclusions: (1) single-sided board construction, while inexpensive, is not suitable for the very high reliability required by POS applications; (2) tin-plated connectors are not reliable for use in POS equipment, especially for low-force, low-current applications like SIMMS cards; and (3) HALT served as a useful tool for identifying some of the perplexing sources of factory and field problems with PCs. Note that the second conclusion is also applicable to those not in the POS market: (a) tin platings are probably not suitable for certain connectors in home and office PCs; and (b) the data provides a rare example where an accelerated test has quickly demonstrated tin-plated connectors to be troublesome, in situ, in complex electronic systems.