Issue link: https://iconnect007.uberflip.com/i/1284035
130 SMT007 MAGAZINE I SEPTEMBER 2020 land size to land size; pad to pad size is mean- ingless. Instead, the edge of the laser drill to the edge of the mechanical drill, as they get closer to each other, start to fail at a higher percent- age; the farther they go away, the safer they become. Again, you can use production house technology and generate your own coupons, and I highly recommend that the OEM checks the coupons that are generated by the board fabricator to make sure everything is correct. Again, the D-coupon matches the structure of your PCB. You are going to evaluate your structures in your process and the coupon that matches your product. If the coupon passes, your boards will be good in assembly. The coupons go into a chamber. The OM tests are currently a 24 position test. You have coupon positions and can define different strat- egies of interconnects. In some cases, you may need two or three different coupons to do all of the different drill spans you have designed into your board. Each coupon can only have two different nets. If you have propagated vias of various configurations, you may need multiple coupons on the panel that goes into the cham- ber and is tested. A real-life test is shown in Figures 13 and 14. It is kind of embarrassing, but this really hap- Figure 13: Example of test results. Figure 14: OM test reflow statistics.