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84 SMT007 MAGAZINE I JULY 2019 The Mannifest Feature Column by Chris Ellis, MANNCORP INC. When it comes to the quality of SMT boards you produce, it can be difficult to know where to begin and what features various PCBA machines offer are most important. To avoid common errors that could compromise the boards you're looking to produce, be sure to keep an eye out on these key features before assembling your line. The first thing to keep in mind when putting together your SMT assembly area is that every step of the process is equally important. Print- ing, placing, and reflow are all essential stages that need to be considered with equal amounts of care and attention. Consider how involved the stencil printing process will be for your boards. While simpler board configurations can easily get by with manual or semi-automatic printing processes, more complex boards that use 01005 chips, micro BGAs, or fine-pitch components should make use of a printer with vision alignment, programmable squeegee pressure, and pro- grammable squeegee speed. This will ensure consistent results and minimize the possibil- ity of error that could occur during the print- ing process. Without these features, you run the risk of costly defects, such as bridging or insufficient or excessive solder. When choosing your pick-and-place machine, accuracy is your key concern. You should make certain your pick-and-place has the capability to position parts with no com- ponent more than 25% off the pad before the reflow process. This is only a minimum require- ment, of course, and an even high degree of accuracy is preferable. For the reflow process itself, you should ensure that the oven has the capability to run separate unique profiles per Common Machine Errors and How to Avoid Them