Issue link: https://iconnect007.uberflip.com/i/750006
16 The PCB Design Magazine • November 2016 As part of the annual subscription fee, da- tabase subscribers can also sponsor up to 20 PCB supplier facility submissions during their 12-month subscription period at no additional cost. Shaughnessy: Can you explain how you conduct a typical analysis of test panels and coupon designs? Wolf: First, let me tell you about the PCQR 2 test panel designs. There are eight standardized test panel designs covering three levels of technol- ogy: • Four single lamination designs with layer counts of 6, 10,14 or 18 layers • Two sequential lamination designs, either 14 or 24 layers, each with six different via structures • Two HDI designs, both at 10 layers with either a 2+6+2 build-up construction or an any layer 4+2+4 stacked via construction These process capability panel designs were developed by the IPC D-36 Subcommit- tee that oversees the IPC PCQR2 Database and are provided under license to IPC for use by its members and the printed circuit board community. The designs are to be used exclu - sively for the support of the IPC PCQR 2 Data- base. [Ed. Note: The design files for these test panel designs can be downloaded from this link.] The designs incorporate the following struc- tures in order to provide relevant statistics on the capability, quality, and reliability of the pro- cesses used in their manufacture: • Outerlayer conductor/space capability • Innerlayer conductor/space capability • Via registration • Via formation capability • Via reliability • Soldermask registration • Single-ended controlled impedance • Differential controlled impedance • Conductive anodic filament • Cross-section All test data except controlled impedance is collected using precision resistance measure- ments. For impedance measurements, we use a robotic TDR tester. CAT uses custom designed software to ef- ficiently and accurately analyze test data and generate analysis reports and supplier facility comparison data. Shaughnessy: You come across a variety of via structures. What sorts of trends are you seeing in via construction and associated via reliability? What's the breakdown of mechanical vs. laser drilled? Wolf: The standardized PCQR 2 test panel designs contain a variety of via structures which in- clude: through vias; blind and buried microvias; buried via cores; multilayer sub-composite vias (both blind and buried); staggered and stacked microvias; and back-drilled vias. All eight of the standardized designs contain through via and 1-deep blind microvia structures using either two or four different drill diameters. The via structures and drill diameters used in the PCQR 2 test panel designs are dictated by the database subscribers through IPC's D-36 Subcommittee. Thus, the database is good source for global PCB supplier via formation process capability and via reliability data. With the increasing use of finer pitched ball grid arrays, 0.012" and 0.016" [0.3 and 0.4 mm] pitch, we are seeing an increase in the number and type of blind microvia structures with drill diameters at or below 0.004" [100 mm]. Blind microvias of this drill diameter and smaller are formed with laser drilling equipment. In the PCQR 2 test panel designs, multilayer through and sub-composite via structures with drill di- ameters of 0.006" [0.15 mm] and above are typ- ically drilled with mechanical drills. As an extreme example, the IPC-24VH-E se- quential lamination test panel design has been built at a 0.187" [4.75 mm] thickness. With 0.010" [0.25 mm] drilled through vias, the re- sult is an 18:1 via plating aspect ratio. There are global PCB supplier facilities who have success- fully formed these high aspect ratio vias and who have also demonstrated via reliability (less than 10% change in via net resistance) after 6X convection reflow assembly simulation at CAT'S DAVID WOLF ON VIA RELIABILITY ANALYSIS