Altium Designer 20 Changed My Layout Design Routines
I just finalized my first PCB design using Altium Designer 20®. At the same time, I tested some new AD20 features, and in this article, I’ll share my thoughts about new layout design features which made the biggest impression for me: sliding, and any-angle routing. Having read about and watched videos regarding these routing features beforehand, I was eager to try. I have experience with trying to route traces on curved shaped layout areas that have 45-degree routing topology, and got frustrated when trying to fit all traces in the required area. AD19 already had a kind of “any-angle routing”, as you were, in fact, free to select any angle while routing. But when adding and enabling clearance design rules, I was not able to get close enough to edges or rounded objects, and had to keep clearances much larger than needed. Meanwhile, minimizing clearance manually increased layout design time—and still the result didn’t satisfy me. Based on this frustration, I had high hopes for sliding and any-angle routing.
An improved Sliding feature changed my process for creating routings for small groups of traces. Instead of routing all traces ready at first go, I did a quick and dirty routing for a group of traces without taking care of angles, optimal clearances, or other details. However, I did the final grouping and layout optimization by utilizing the sliding feature afterwards, and in that way arranged them in the most convenient positions in the layout area. It seemed to work well that at first, I defined stack-up, and then determined width and clearance rules according to target impedance and cross-talk minimization. After this rough layout routing, I grouped traces and moved them to their final positions by sliding. Sliding also worked well for traces routed using any-angle routing at an arbitrary angle. When sliding routed traces towards a “locked” trace (select Walkaround Obstacles), the slide trace takes the same shape while still respecting the minimum clearance rule. For a small group of traces, this method allows you to create routings quickly while still fulfilling design rules. In picture1, you can see examples showing that there are a lot of options for how to arrange traces just by sliding.
When sliding traces close to the board outline or cutout area, the trace takes the shape of the edge of the PCB while keeping the predefined board edge clearance rule, as presented in picture 2. I see clear benefits for this when designing printed or structural electronics. In these situations, the board area is never rectangular, but more or less follows the part shape. With sliding, I can draw a straight trace and just push it to the edge of the board area. This allows the routing of traces to the closest allowed location to the edge of the PCB, and in this way, we can utilize the full available layout area, not just areas where we managed to put 45 angle traces. AD20 made sliding of individual or grouped traces in a smart way, which is a very useful feature for packing traces in an optimal area or maybe even in a minimum area. The benefit of this is especially notable when working with board areas which have curved shaped edges.
Any-angle routing finds out the shortest needed trace between two points. In picture 3 below is an example in which the highlighted trace was routed by the traditional 45-degree method and lighter trace is a proposal made by any angle routing. As you can see the trace changes angles in a smart way when avoiding vias. The same happened also with any obstacles, like other traces and components, while keeping routing smooth and fluent. I routed lots of traces by any angle routing and in all cases I was able to find out the shortest way for trace, even in challenging situations with many different sizes and shapes of obstacles. This gave me a new routing method: minimum trace distance principle.
Minimum trace distance design principle can have a couple of benefits. One example case is when designing capacitive sensors. These sensors measure extremely small capacitances, even less than one pico farad. Because of this, designing routing with minimum parasitic capacitance is important. Every routed trace has parasitic capacitance (and inductance as well), and capacitance depends on both the stack-up design and the trace length. Capacitance per length can be obtained quickly from the impedance profile of layer stack manager, and total capacitance is then just multiplying length of trace with capacitance per length. Minimizing trace capacitance requires minimizing trace length.
Another example case is, situations when fast rise time causes signal integrity problems. With the 45-degree routing topology, the length of a trace can be long enough to cause problems, but straightening the line by any angle routing can minimize the length at below critical length. I won’t say any angle routing alone solves this problem, as you still need to design termination if rise time is too fast even if shortening the trace. Any angle routing gives you a tool to find the minimum trace length. It may or may not help. After shortening the trace, you still need to deter,ome whether termination is needed or not.
In printed electronics, minimum trace length minimizes trace resistance. In these kinds of applications, shortening the trace length is always beneficial, as the resistance of printed conductive ink traces always plays an important role. Every ohm you can take away from the trace is worth the effort.
Any angle routing is an excellent choice in crowded layout areas. So far, 45 degree routing was jamming in “rush” conditions, but this is an easy job for any angle routing. Crowded areas where there are many vias, components, restriction areas or other obstacles in a small area, are easiest to solve with any angle routing. Instead of jamming because trace does not find a way with 45 degree angles, any angle routing finds the most suitable angle for trace, and then can bypass obstacles while still filling the clearance rule. Any angle routing allows “hugging” obstacles with minimum clearance with any trace shape. You can see an example of this in Image 4 below.
When designing layout, we also need to think about crosstalk. One reason for crosstalk is too small clearance between traces compared to thickness of dielectric between trace and reference plane. While I did routing by any angle routing I noticed that it is rare that traces are travelling in parallel with minimum allowed clearance. Instead, traces go slightly different directions, because rarely do the shortest distances between two sets of points lead in exactly in the same direction, as we can see in Picture 5. Due to this, in many cases clearances between traces were bigger than the minimum allowed, which means less cross talk. And through any angle routing, this happened accidentally. Someone could say the layout isn't exactly beautiful, but at the end of the day, does it need to be if it just works better?
After my PCB design, I concluded that sliding and any angle routing provides the following useful benefits:
- Sliding allows quick grouping of traces. No matter what the angle is, grouping can be done smoothly while considering clearance rules.
- With the sliding feature you can utilize a full PCB or printed electronics layout area, which is especially valuable in cases when the layout area is curved shaped.
- Any angle routing finds the shortest path for the trace. With this you can use the shortest trace design principle, which minimizes parasitic capacitances and inductances and resistances in printed electronics.
- Any angle routing gives huge benefits in crowded layout areas. It definitely makes routing faster by offering a lot more freedom for routing directions.
- Using the minimum trace length principle with any angle routing, you “accidentally” decrease cross-talk, because you most probably do not route traces parallel with minimum clearance.
Sliding and any angle routing together changed my routines to route traces in PCBs and printed electronics. These features bring new options for doing routings, and can make routing quicker and easier. In addition, these can also bring new opportunities to implement different routing principles, like minimum trace distance. I had big expectations when starting layout design, and after using these features, I see that these will prove incredibly useful in any layout design tasks.