Issue link: https://iconnect007.uberflip.com/i/1428512
30 PCB007 MAGAZINE I NOVEMBER 2021 but no one really would do any math or science behind it. e PCB fabricator would just build the boards and ship them. Sometimes there are assembly problems, and the industry says, "ere's something going on with microvias. ree-stack and four-stack are not as safe as a single microvia and staggering them." Every- body is trying to find out how strong or how weak they are. Most people were finding out at assembly because the standard IPC-6012 per- formance specs in the evaluation couldn't iden- tify a weak microvia very well. So, we came up with the OM tester, which is using the IPC-TM 650 2.6.27 test method, which actually takes a coupon with the same structures that are in the board and simulates reflow on the coupon before we ship the boards. If that structure, which is in the board that we're trying to ship, can survive reflow in a tes- ter, then we know that the boards are more than likely going to pass and survive reflow and assembly. is works great. It will tell fab- ricators that if we process everything right, the board is going to be reliable through reflow. However, aer a couple years of having the tes- ter, we discovered we did everything right, but occasionally it wasn't working. ey were fail- ing 6X reflow. Utilizing our extensive experi- ence in microvia fabrication, our portfolio of reliability testing data, materials expertise and soware tools, we can simulate the stack-up; you can actually input the microvia structure and the data output will tell you if it can sur- vive six reflows or not. We're now doing that same evolution that we did for electrical tests with microvias, where we can analyze and simulate if it's going to work before we fabricate. If we find some- thing that will appear to work, or if not, we can share and help understand between our cus- tomer and ourselves: What is the risk if we do this? Build the boards and then test it for reli- ability by reflow simulation and resistance test- ing, and make it match. at's where we have gone to this next stage of evolution, which is as important as netlist compare and down- loading. I think that's where we're at with this method. Johnson: at makes sense. Does that trigger changes in the design to get better reliability? How does that dialogue happen? Partida: at dialogue is evolving as well. As a fabricator, if somebody hands you a drawing in a stackup and you say, "at won't work, and I've even asked some people I've proven it on with their boards, that it would only last three reflows. But if we change the material, change the design, we can get it to 10X reflow." en they say, "Okay, let's rebuild and change the design. Let's do that." I asked them the ques- tion, then said, "Just give me your gut first reac- tion when I ask you this question." ey say, "Shoot. If I told you the day you gave me the print that these boards would fail if we tried to build them, what would you do?" He imme- diately responded, "We would have found another fabricator." Johnson: at's the wrong answer, isn't it? e customer is sweeping fundamental issues with their design under the rug. Gerry Partida