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PCBD-June2016

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12 The PCB Design Magazine • June 2016 Gaines: As we have progressed into smaller-pitch components, the space in and around compo- nents has decreased even more. These smaller areas drive what the vias and routes can be, and sometimes we are restricted by our clients and vendors on the sizes we can use. This may be a costing issue on the bare boards, or the smaller lines and vias may be restricted by an internal spec that was conceived before ultra-fine-pitch came to be. We have actually had to get chief technical officers sign off on the line/space and via sizes required for layouts. Placing bypass capacitors for these finer- pitched parts can also be an issue. The pitch may drive the use of smaller body caps than the engineers or clients want to use. We end up placing caps all around the part because the ap- plication notes said to use this quantity and this value. Shaughnessy: Do your PCB design tools handle tighter tolerances well? What about PCB design tools in general? Designing with Fine Lines and Features by Andy Shaughnessy Albert Gaines is the owner and senior PCB designer at HiGain Design Services in Norcross, Georgia. He's been a PCB designer since 1981; he designed a variety of boards at Scientific At- lanta, and then ViaSat, before deciding to open his own company in metro Atlanta. I asked Al- bert to talk about some of the finer lines and features that come through his shop, as well as some design techniques for boards with tight tolerances. Andy Shaughnessy: What are the tightest toler- ances you are currently designing? Albert Gaines: We have used 3.6 mil line and space on a few but most are 4 mil line and space for HDI. Shaughnessy: What are the most challenging is- sues designers face regarding fine spaces, traces, and pitch? FEATURE INTERVIEW

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