Issue link: https://iconnect007.uberflip.com/i/1305670
68 SMT007 MAGAZINE I NOVEMBER 2020 • GS400000A: TH and blind vias >four layers sequentially laminated on a PCB ≤0.125 inches • GT408000B: Any-layer through-hole on a PCB ≥0.125 inches on a 5" coupon • GT501000A: Any-layer through-hole on a PCB ≥0.125 inches on a 6" coupon PerfectTest PerfectTest came along in 1989 to address the problems in multilayer material move- ment and drill registration. Unfortunately, they are no longer in business, but their idea is one that should be explained. The coupons (Figure 7a) were placed at the outer edges of the multilayer panel. The coupons worked by detecting which PTHs detected the movement of a particular I/L copper wedge. Figure 7b illustrates the 0.002" increments from 1 mil to 9 mils in the X- and Y-axis that the coupon detected. Coupons could be placed on every layer or just specific ones. Although no specific testing equipment was required, Figure 6C shows the PerfectTest unit equipped with analysis and data storage software. Figure 7d is a summary of 250,000 coupon readings collected in manu- facturing over a six-month period. At the time, there were over 185 users of this coupon in 22 countries. Figure 6: IST is a DC current-induced thermal cycling test; (a) a typical 6" coupon, (b) a sense circuit daisy chain, (c) a power circuit daisy chain, (d) an isometric view of parallel and overlapping power and sense circuits, (e) IST power, data acquisition, and fixturing test equipment, (f) typical heating-cooling cycle, (g) and failure modes of thermally stressed interconnects (PWB Interconnect Solutions Inc., pwbcorp.com) [5] .