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12 SMT007 MAGAZINE I NOVEMBER 2021 Horner: We see some challeng- es with design for test. e big- gest challenge is giving access to the key points and under- standing a test strategy prior to the assembly being built. We feel there's a lack of communi- cation among design, manufac- turing, and test that creates an opportunity for test engineer- ing to put their wishes into the design. ere's a disconnect be- tween the internal and external test engineering groups and the design group. Matties: Are there differences between test strategies based on the EMS provider that you're using, or is there a standard that design- ers should be following? Horner: ere's not really a standard to fol- low other than understanding what your EMS partner must support. What solutions do they have? Do they have an X-ray? Do they have an AOI? Do they have an in-circuit tester? Do they have a flying prober? Understanding what your partner has and what they have available for test and inspection needs to be communi- cated upstream or the design group needs to specify it: "is is a test strategy based on this AOI, this X-ray, and this electrical test." Matties: So, not only does the design layout person need to be an SI and stackup expert, now they must be an authority on test strate- gies as well. Horner: ey must have a good understanding of what they're trying to accomplish. We see a lot of designers working with a project engineer, and sometimes that role falls onto a project en- gineer or a program manager of a specific proj- ect. at understanding needs to be somewhere down the food chain where the design is in a so stage and they're coming up with a plan. Matties: Now, going back to those common problems, such as splashing, opens, and shorts, what feedback or data do you provide to the manufacturers that will help them improve their process, or is there such a cycle? Horner: For our test services, we incorporate a summary where, by serial number, they can see what the common faults are. If they have some quality man- agement system (QMS) at the contract house, they're reading in the data, and they can see trends quickly. But we do a sum- mary when we're testing product under con- tract test services. Nolan Johnson: Bert, where does a project man- ager, project engineer, or designer go to find out? Where are their resources for design for test? Horner: Most test partners have created their own, and they're all based on a very similar de- sign for tests guidelines, whether it's bed-of- nails, flying probe, or boundary scan. ere are some common papers for most partners (we're one of them), and we have a boundary scan, an ICT, and a flying probe guideline for design for tests. ere are also products in the market. ASTER Technologies has TestWay. Mentor has Text Expert. ese are tools that are encroaching on that schematic level review, where everybody has a solution that looks for access. Whether they use it is a different ques- tion, but we are seeing people in the market look at the schematic level design for test: Au- tomated Tool, TestWay, Test Expert. I know we have both products here, and when you're look- ing at the schematic level, you're seeing where the controllability of a circuit is, where you have access, and you have control of a circuit so you can isolate down on to a net, a pin, and a device. Bert Horner

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