Thermal Emission System for Circuit Board Troubleshooting
A great deal of time is spent debugging boards that have been kicked off the manufacturing line. Technicians use results from ICT, FCT, and other equipment to identify defects, often with little or no success. The composition of defects at this point in the manufacturing process is much different than at the end of the manufacturing line. At this stage, the majority of defects are often caused by power-to-ground shorts and bad components. EL has typically demonstrated a detection rate of over 75% when testing boards with such defects. When used as the first screen of defective boards, EL can quickly provide useful troubleshooting information, dramatically reducing time to repair.
Circuit boards that have been returned from the field can present particular problems when troubleshooting. Many times technicians have little or no idea where to begin in the failure analysis process. EL can provide very helpful information, allowing technicians to narrow down their search to a small region of the board containing only a few suspect components.
EL is frequently used for the reclamation of PCBA bone piles. Because the value of bone piles can be in the millions of dollars, their recovery brings immediate and substantial financial benefits. EL typically enables OEMs and contract manufacturers to salvage over 50% of their bone piles. In such cases, the payback period can be as short as two to three months.
EL can be used to inspect boards for basic functionality. Although EL cannot provide the same detailed level of functional verification as a functional test, it can provide verification of basic board operation. Advantages of EL over traditional functional testers include low cost and fast setup. No custom hardware is required and tests can usually be setup in less than an hour. EL is ideal when the high cost of a dedicated functional tester cannot be justified.
Because of increasing component placement density, as well as an increase in component power density, thermal imaging has become an important tool in the design process. EL aids board layout designers by helping them obtain and analyze thermal profiles of prototype boards and components. Thermal management problems can be resolved in the design phase before production begins, minimizing the high costs associated with troubleshooting and repair. Additionally, by developing an historical database of board and component thermal profiles, designers can incorporate the thermal behavior of boards and components much earlier in the design process.
EL provides an additional level of screening on the manufacturing line to identify defects that conventional test methods cannot detect. Stressed components can pass ICT and FCT only to fail early in the field and thus present reliability hazards. Many times, these components run hotter than normal and can be identified by EL before they leave the manufacturing plant. By using EL at the end of the manufacturing line, many of these defects can be identified long before they reach the scrap pile.