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38 SMT007 MAGAZINE I NOVEMBER 2020 AOI, ICT, flying probe, boundary scan, and all of that. The neat and unique thing about that is if you've done simulation, identified redun- dancies, and use our output processing, you're going to already create a lean test program. A classic is somebody who is doing a bound- ary scan and flying probe, for example. Flying probe, as we know, has a long test time in com- parison to ICT. But if you can identify the parts that are being very well tested with bound- ary scan, you can create a flying probe pro- gram that has now removed that redundancy that was tested with the boundary scan. You can get a cheaper test, less engineering time to develop the flying probe, and a faster execu- tion time, saving you engineering hours. Johnson: You're creating quite a database for coverage. Webb: Yes. Let's extend this a little bit more into coverage and measurement. I talked to you about coverage estimation or simulation and the after processing stage. The third part is, once you have tests developed and running on the produc- tion floor, we can bring in those programs or the test coverage reports that are produced by the machine, and we can measure how good the test coverage actually is. Does it meet your expecta- tions? Does it match what you simulated them to be? Are there gaps that didn't get debugged cor- rectly? It gives you a lot of visibility as to how the test program actually turned out. That completes the loop. You can estimate in the beginning, do the CAD-to-CAM con- version, and then do the measurement. We refer to that whole process as the digital twin, which is an Industry 4.0 term. You're replicat- ing your manufacturing test line inside your computer. You're modeling that and measuring the results, so you're using data to make better decisions about your test that, otherwise, you might be guessing about. Johnson: As test and inspection become more of a part of the feedback loop for the digital twin, what are the challenges? Now that you have results, how do you integrate your results with a digital twin? We b b : That's a good question. The TestWay software can allow you to do a number of things around optimizing your test. After it started 25 years ago, the objec- tive was a tool to do advanced electrical DFT. A lot of times, when peo- ple talk about DFT today, they focus strictly on the mechanical side accessibility from a flying probe or ICT viewpoint. But it actually goes a lot deeper than that. If you can start early at the time of schematic capture, even pre-layout, you have the chance of looking at the design from an electrical viewpoint, making sure the board has been designed to be testable. You're looking at things like boundary scan chains, looking at disables, you're looking at anything that would keep you from being able to fully test the board. That's one thing the tool does, and that's how the tool got started. The other equally important thing is we can analyze test cover- age. We can do test coverage simulation early on, so if you know that you have a circuit board that's coming to you and you need to have some tests, the tool allows you to simu- late different test strategies. For example, you can look at boundary scan, AOI, AXI, or ICT, and you can see what types of coverage each of those would bring to the table and decide on what your best strategy would be. You could also use the tool to elimi- nate redundancies because you might be over testing the board. You can use the tool to iden- tify places where you're testing in more than one strategy, and you might choose to elimi- nate one of those. You can also identify gaps in the test coverage, and maybe you need to think about adding another strategy to make up for some gap that you haven't thought of. The software will point all of that out. Those are the two primary things that you can use the tool for initially. We also do CAD/ CAM output processing. For example, you can use the tool to create beginning develop- ment files for a large number of machines— William Webb

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