This is the second article in a two-part series on the causes of failure in electromechanical relays. Part I, in the February 2018 issue of EDFA , examines a variety of failures caused by the formation of oxide on contact surfaces. As the author explains, electric arcing in the presence of silicon oil or vapor creates SiO 2 deposits in the contact region that build up over time. Here in Part II, the author presents examples of failures caused by nitrous gases, phosphoric acid crystals, and wax, which is often found on enameled copper wires.

This article, the first of a two-part series, investigates the causes of failure in electromechanical relays. In Part I, the author examines contact-related failures due to the buildup of nonconductive particles and films and the effects of arcing and wear. Part II, scheduled for the May 2018 issue of EDFA , presents examples of failures caused by nitrous gases, phosphoric acid crystals, and wax. It also examines a case involving a sealed relay that popped open during operation.

This is the second article in a two-part series investigating solder connection failures associated with BGA packages. Part I, in the February 2017 issue of EDFA, examines various cases of open and short circuit failures, discusses the formation of voids, and explains how to reveal important clues by grinding away the BGA package. Part II continues the analysis of voids and focuses in on failures due to circuit board faults. In such cases, the board is ground away from the backside, stopping just short of the first inner copper layer. The alignment of the two uppermost copper layers, the integrity of microvias, and other potential problems are then examined using polarized light which readily passes through the remaining resin and fibers. As the examples in the article show, this approach can reveal a wide range of manufacturing defects in PCBs.

This article is the first in a two-part series analyzing solder connection failures between BGA packages and PCB assemblies. Part I examines failures attributed to oxygen intrusion during reflow, underetched solder resist, and solder paste printing problems. In the latter case, X-ray inspection revealed no abnormalities other than a variation in ball size. To get to the root cause, the corpus of the BGA was progressively ground away, leaving only the balls and an unobstructed view of the PCB surface. A description of the process, supported by detailed images, is included in the article. In Part II, scheduled for the May 2017 issue of EDFA, the author delves deeper into the analysis of voids and presents an alternate FA approach that involves grinding away much of the PCB.