Issue link: https://iconnect007.uberflip.com/i/1481368
OCTOBER 2022 I DESIGN007 MAGAZINE 67 and their efforts to bring these images and poten- tial standards into the view of our PCB design and manufacturing neighborhoods. But until then, with all the advertising pag- eantry and displays of low-digit micron trace patterns, I'm afraid some designers will think they can try this out on "normal" design topolo- gies. In fact, I'm currently working on a board in which the designer utilized 15-micron lines to route out of an ultra-fine pitch BGA package. is Hail Mary approach was due to the ongo- ing effects of our present supply chain crisis. e original design had a much larger processor appropriately matching the PCB topology scale of the layout surroundings. But like a thief in the night, the parts became unavailable and the only procurable parts with similar functionality were packaged within a 143 pin 0.4 mm pitch BGA. To avoid substantial redesign using conven- tional HDI via-in-land technology affecting the stackup, the designer chose to route out the inner row connections through the outer row contacts with 15-micron lines. e designer "went all UHDI" without any special process- ing notes or material specification. Our vol- ume bare board suppliers have "no bid." I have called three advertised suppliers of "X-SAP" processing, stating that I have money to spend, but I have not received a single call back. Can UHDI and X-SAP technology help get an EMS stakeholder out of a bind by delivering on this customer design application with deliv- ery requirements of 2,700+ boards per month? Is this layer 1 customer artwork containing 15-micron tracks a viable solution? Can we just add a note which says "Add UHDI processed copper here using supplied artwork?" Should we continue punching down this UHDI path or re-design the entire area of the design to con- ventional HDI via technology? Which solution will give our customer less sticker shock? Diving Into UHDI on a PCB As I depict in Figures 2 through 5, it is easy for a PCB designer to draw a 15-micron (0.59 mil) trace with a CAD tool. But now what? Is X-SAP viable, available, and cost effective for use on any PCB? ese questions must be answered before layout or PCB designers risk hitting "send" and shooting their design data beyond the comfort of our manufacturing stakeholder neighborhood. Figure 2: A common PCB design layout neighbor- hood. Not without its own challenges of manufactur- ability but at this scale appears to be exceptionally rich with applicable, perceptible attributes. For our PCB project stakeholders, this is like starting with that view of the blanket on the grass in the park in "Powers of Ten." Figure 3: Zooming in to the metallized contact end of a common 0201 chip, we can see the transition point between the land and the trace. We can see how the solder mask clearance around the land will allow the solder to flow out and away from the con- tact allowing disproportionate amounts of solder on each end of the chip, possibly leading to an assem- bly defect.