Issue link: https://iconnect007.uberflip.com/i/1014812
AUGUST 2018 I DESIGN007 MAGAZINE 37 In many cases, the via is shifted toward the terminals. Escape routing is optimized with this "off-grid" connection. However, a new strategy for fanout and escape routing must be defined for each BGA. The classical autorouter available in most ECAD systems quickly runs into its limitations. PCB manufacturing has improved to accom- modate the finer features needed to break out BGAs. Dimensions of trace width and mini- mum via size have all shrunk. High-density interconnect (HDI) has also become more and more common for high-speed boards with very dense parts placement. A pad size of .018" (0.45 mm) and a drill diameter of .006" (0.15 mm) are considered a standard for through-hole connections for 1 oz. copper. Contact your PCB fabricator to determine their exact minimums for these and other manufacturing-critical dimensions. When working with BGA breakouts, narrower traces can be used near the device to facilitate getting the signals out from the package. How- ever, it's virtually impossible to maintain target Figure 4: Design rule editor (fanout control) in Altium Designer. Figure 5: Different pin assignments for the fanout and escape routing of BGAs.