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50 SMT Magazine • November 2014 assembly, also showed that there was not a sin- gle area where the coating had lifted. endurance test The aviation industry's requirements re- garding the integrity and service life of safety- relevant components far outweighs those of the automotive industry, whose requirements are themselves recognized as being very tough. One example of this is the burn-in test that is performed post-production on tuning controls. To understand the rationale behind this test it's helpful to know that airborne radios are rare- ly installed in the plane's air-conditioned and pressurized engine area. Mostly they are located in the nose of the aircraft where very different temperature and humidity conditions prevail. This is why it is so important to ensure that the protective coating is fully bonded to the electri- cal components. Even the smallest leak would result in mois- ture ingress, potentially leading to complete failure of the radio communications system. What most air passengers don't realize is that all passenger planes are obliged to carry two sets of radio equipment on board; the second as backup in case the first one fails. If a plane lands at its destination with a defective radio system, it has to stay on ground until a spare radio set has been acquired and fitted. The purpose of the burn-in test is to investi- gate continuous operation and accelerated age- ing of electronic components. As the toughest load test available for electronic circuit boards, it is used to detect manufacturing faults which were not picked up earlier and to identify com- ponents that would fail in continuous opera- tion. Burn-in is performed on the finished radi- os under operating conditions (i.e., powered up and with antennae). The test consists of a series avionics: atmosPHeric PressUre PLasma case stUDy continues Figure 4: The coating's adhesive bond is visually inspected under uV light before the SMD assembly is mounted in the radio. Then a burn-in test is performed to verify its stability (Photo: Plasmatreat). arTiCle