Issue link: https://iconnect007.uberflip.com/i/1174596
78 DESIGN007 MAGAZINE I OCTOBER 2019 can select the remaining parts and apply a reg- ular fanout, as we spoke about already. Now that the rules are defined and fanouts have been completed, we need to perform the actual routing, which historically is the most time-intensive portion of creating a PCB. To mitigate this level of effort, your tool must of- fer an intelligent level of automation, called interactive or sketch routing. Sketch routing achieves an optimal result in the most efficient manner. Using this technology, we will want to route those nets deemed as the most critical; this will ensure they are routed on the proper layers with the shortest length. First, let's talk about the routing of a single net using interactive routing. Unlike trace digitizing, which every tool can do, interactive routing allows you to guide a trace from its start point to end point with the tool decid - ing where corners are placed, pushing trac- es or vias in tight loca- tions to complete the route. We no longer have to worry about manually moving trac - es in tight locations to place additional routes. Next, we can move to the next level of automation by using multi-trace autorout- ing. In some tools, this is called sketch routing because you're basical- ly drawing a rough line in the location where you'd like traces routed with layer change loca - tion (if needed) and let- ting the tool completely route the nets. In most cases, this routing tech- nology is so powerful that it will produce routes in the same fashion as if you manually routed the same nets. Figures 6 and 7 show the sketch process and the com- pleted routing with no clean-up. The advantages of sketch routing are that you can look at alternative routing possibilities very quickly and explore various scenarios to find the best layout for the design. For exam- ple, a designer could try a horizontal via pat- tern, but might find that it makes the routes go between components; a horizontal via pattern produces the best route. Just like with single-ended nets, both inter- active and sketch routing should be able to Figure 6: Sketch route path. Figure 7: Complete sketch route.