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46 The PCB Design Magazine • August 2014 to provide optimal spacing in order to minimize crosstalk, designers want to pack the traces to- gether in dense areas and spread them out in more open areas. Considering again the visual comprehension that a designer has for the rout- ing, the dense areas are known; and during the routing task, it is clear which groups of signals need to be packed together to maximize the density of the routing channels. Style and qual- ity are similar; however, the second part of this series will go deeper into all the aspects of what constitutes quality. The sketch router allows the designer to route either a packed or unpacked style. The packed style will group the traces together and is very useful in dense situations (Figure 3). The unpacked style (Figure 4) routes in a di- rect and efficient manner, which naturally will spread the traces apart compared to the packed style. In both cases, the tuning algorithms will work just fine because in both cases, the exist- ing traces are pushed and shoved to allow enough space for the serpentines, trombone or sawtooth patterns. Sketch routing is one of those things that is better demonstrated with video than still images. For a quick video of what sketch routing looks like, click here. Summary You could say that allowing the designer to control location, apply restrictions and choose a style is exactly what occurs during common interactive routing. Yes, this is true. Manual rout- ing provides the control and quality, but is often slow and significantly slower on large designs. Automatic routing pro- vides the performance and a certain amount of control, but it lacks the quality. But advanced sketch routing technology provides designers with this desired control, along with quality and high performance. PCBDESIGN Charles Pfeil is an engineering director in the systems Design Division at Mentor graphics. he was the original product archi- tect for expedition PCB and an inventor of XtremePCB. Pfeil has been in the PCB industry over 40 years as a designer, owner of a service bureau, and has also worked in marketing and engineering management at Racal-Redac, Asi, Cadence, PADs, and veriBest. To contact him, click here. sketch routing PART 1: TAKING CoNTRoL continues Figure 4: Routing using an unpacked style.