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AUGUST 2020 I DESIGN007 MAGAZINE 61 it could just as easily be because of manufac- turing limitations at your PCB manufacturer or incompatibilities between your CAD's export files and PCB manufacturing processes. The only way to make sure none of these issues get in the way of properly working circuits is with electrical testing. The Electrical Test Process Your PCB manufacturer will perform electri- cal testing based on the information that you send them. Some perform testing straight from Gerber files. Other manufacturers will want you to generate a separate netlist file. Your CAD tool will have specific instructions that lead you through this process. The Gerber or netlist file contains all the information necessary for your PCB manufac- turer to create automated electrical tests. This includes individual nets, pad geometry, the location and sizes of through-holes, and solder mask openings. The testing process ensures that all nets are connected as expected and that no extra connections are created during the manufacturing process. What to Look for With Electrical Test Services Now that we understand the importance of electrical testing, we can spot some informa- tion to look for when picking a PCB manu- facturer. You'll have different criteria based on the scale and where you are in your produc- tion. If you are just producing a few boards, either because it's a small project or you're in the prototyping phase, look for a manufacturer that performs a flying probe test. However, if you're looking for a major PCB run, it might be more cost-effective to find a manufacturer with a bed of nails testing option. Depending on the scope of your proj- ect, you may want to pay extra for IPC-9252 certification for your electrical testing. Most importantly, electrical testing gives you the peace of mind that the manufactured PCBs shipped to you match the design files that you submitted to the manufacturer. This is the best way to make sure you aren't submitting faulty PCB designs, which will save you time, money, and headaches. DESIGN007 Bob Tise is an engineer at Sunstone Circuits, and Matt Stevenson is the VP of sales and marketing at Sunstone Circuits. To read past columns or contact Tise and Stevenson, click here. Bob Tise Matt Stevenson Figure 2: A typical Netlist for testing a PCB.

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