PCB007 Magazine

PCB-Feb2017

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86 The PCB Magazine • February 2017 In my December 2016 column, we discussed the idea of supplier surveillance and that one should put into place some type of double- check to ensure that you are getting exactly what you've asked for, designed, ordered, etc. To take that idea a step further and to circle it back to the main industry we are discussing here, let's look at some of the testing that one might do under a supplier surveillance program as it relates to a standard printed circuit board—the foundation of most electronics in today's world. The most obvious and commonly per- formed first steps in testing on bare printed circuit boards are a combination of as-received visual examinations and cross-sectional evalua- tions via microsection analysis. From an equip- ment standpoint, the as-received visual exami- nation needs only a simple stereomicroscope with magnification up to around 100x. In the as-received state, the printed circuit board can be inspected for various anomalies, such as those pertaining to conductor widths/spacings, plated through-hole/via hole construction, and surface contamination, just to name a few. A more in-depth inspection can be accom- plished through microsection analysis, whereas the printed circuit board will need to be diced, potted in an epoxy resin, and then ground and polished to specific vertical and/or horizontal planes of interest. For this inspection, internal board structures can be intimately inspected and measured to ensure that the board has been constructed as you've designed or specified. Potential anomalies that could affect reliabil- ity down the road could also be identified. Of course, the sample preparation and inspection techniques needed for this type of analysis are a bit more involved as microsection analysis is as much art as it is science and then some type of metallurgical scope will be needed for the by Keith M. Sellers NTS-BALTIMORE How Strong is Your Foundation? LET'S TALK TESTING

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