I worked as a design engineer for an optical-telecom company that had deployed 1000 pieces of equipment worldwide. Having so many modules in the field means a trickle of returns, and it was my job to investigate the failures. One investigation taught me a wonderful lesson. I received a module whose source of failure was easily identifiable: a charred tantalum capacitor. It failed short, making the whole multithousand-dollar module nonoperational. This surface-mount capacitor-with a 7343 footprint and 20V rating-rnwas sitting on a 12V-dc plane. This failure rate of one capacitor in about 10,000 pieces in this time span was well below the statistical prediction. I took a picture of the fallen capacitor and considered the case closed.
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