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8 The PCB Design Magazine • November 2016 For such a simple structure, the PCB via cer- tainly stirs up more than its share of intrigue. The via is another one of those topics that pop up in our reader surveys when we ask about your ongoing challenges. And it's not just the blind and buried vias that draw readers' at- tention. Something as basic as a hole drilled through a circuit board can generate a whole lot of controversy. To get a handle on this issue, we sent read- ers a survey dedicated solely to vias. We asked readers to describe their greatest via challenges, and the comments told the tale. Here is a small sample of the replies: • Understanding the PCB manufacturing process • Impedance matching • Routing high I/O .65 mm pitch vias • Tolerances or limitations of the PCB house • The cost of blind and buried • Via-in-pad • Finding the smallest via that can be created with a high yield • The correct size for HDI and IPC Class 3 • The cost of filling and plating over them • Not enough pad for annular ring in the design • Designers do not understand aspect ratio. • Blind via plating technology • Vias under components • Tenting vias • In-house politics: cost, fear of the unfamiliar • Reliability concerns due to thermal cycling • Vias with large board thicknesses • Strength when temperature cycled • Cost of standard vias vs. state of the art by Andy Shaughnessy I-CONNECT007 The Hole Truth THE SHAUGHNESSY REPORT

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