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PCB-Jan2016

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52 The PCB Magazine • January 2016 When a new PCB design is born, designers envision what the product will provide when completed. Whether the product is for the con- sumer, aerospace, military, medical or countless other markets, the designers—or more likely, the customers—expect certain deliverables on the commodity they wish to purchase. To provide the desired functionality of the product design, engineers specify these deliverables on blueprints (prints) or fabrication drawings (fab drawings). These documents are the recipe for the manufac - turing requirements of the given product. A multitude of information is provided in these documents. In most cases the designers do not know the specific processes involved that satisfy their requirements, nor do they have to. They specify their requirements on the fab drawing and allow the PCB manufac- turer to use the necessary processes to supply the final product, and herein lies the problem. Some complex designs could have fabrication drawings exceeding 20 pages, and may include requirements ranging from which raw materials are to be used to what type of anti-static packag- ing is required for shipping. For this discussion, we will focus on how these documents pertain to electrical test (ET). In most fabrication drawings, many pages are graphical in nature and depict special dimen- sional or mechanical attributes, while others show drill/cutter requirements, plating require- ments, special layup instructions, and almost always a note(s) page. Should ET read the entire package? Yes. Why? Because many times there can be mechanical attributes that will influence how the final product can be tested. However, there are some main topics ET will definitely be looking for: by Todd Kolmodin garDien serVices usa testing todd Fabrication Drawings and Electrical Test— Reading the Fine Print coluMn

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