PCB Auto-Route

Hi everybody,

I've been using Altium Designer for routing from the beginning of my (short) EE experience.
I don't really like their integrated routing solution especially the auto-routing that never make me save time and that I use only to get information of the routing difficulty (I do all tracks by end after that).

Now I wonder on using another PCB Design solution (free or shareware) that could make my work easier when routing tracks and has a good (at least better than Altium) auto-route algorithm.

Do someone has an experience with routing on Altium Designer?
What's your opinion?

Besides Altium, what tool do you use and like? I heard that PADS from Mentor Graphics was not that bad. Any feedback on this solution?

Thank you

Francois,

A good PCB autorouter is expensive so you'll be hard pressed to find a free or shareware version that is better than Altium's.

Have you tried to "fan-out" your connection points and setup constraints for routing?

To get a good results in an autorouter, you must spend a considerable amount of time setting up the tool before routing.

Can you tell us what the autorouter is doing that is undesirable? Maybe attach a screenshot so we can help you find way to force the tool to behave better.

I don't use auto-routing for PCBs but on the rare occasions I did, I used the PADS auto-router. In PADS 2005 it had some pretty big misbehavings, even if in the end it behaved according to constraints. One example would be some traces that went nowhere, which at low frequencies wouldn't have an effect, but at higher frequencies might cause some unwanted reflexions.

In 2009, I stopped noticing those errors, and I usually check my design. Best approach is to manually route the critical part of your design and use auto-route for the rest.

Like Joe Wolin said, you won't find very good free auto-routing tools. And even the best ones like PADS and Altium Designer need a lot of checking afterwards and a very good setup of constraints and rules before starting.

I usually setup some constraints for routing but I may miss some important rules as I don't clearly know what each setting refer to...

I just looked for a tutorial, is this one seem OK for you about basics rules to setup? http://wiki.altium.com/display/ADOH/Situs+Autorouting+Essentials

Are they some other rules or recommendation to check before auto-routing?

I don't have any example right now. I know that on my last board it was quiet long too route as Altium wasn't able to finish around 30 tracks on a four layers PCB with more than 200 connections, I basically had to move every tracks from Altium all around before getting my final results...

So you say that PADS is equivalent to Altium Designer as routing tool, so no advantage to switch?

I heard from a friend that his robot association routed their mother board all automatically with PADs and it did work. That's why I was concerned about Altium, I never finished a board with the auto-route tool... But as I said to Joe Wolin, I may have missed the important settings as I don't know the meaning of all the rules.

Do you like PADS? Is it quiet easy to handle?

I never said they were equivalent... but it's easy to find your way through both if you already know your way through one of them.

Personally I used only PADS auto-router, and find PADS more user-friendly... but also (for the versions I used) a little more buggy then Altium Designer.

In short, I would recommend PADS over Altium Designer strictly on personal preference (I find it easier to set constraints and rules and also easier to manipulate libraries)... in my circles preferences are 50-50 between the 2 and usage is on "whatever is provided" basis.

OK sorry that I misunderstood your point.

Thank you for your feedback on PADS, I should try the evaluation software to make my own opinion.

I Have used Altium for nearly a decade and find the product very useful. The aspect of routing for me is more art then process....I start by setting my rules very carefully and then setting the parameters for the route based on my understanding of the complexity of the board. If the board is simple will keep it at either one or two layers. if it is moderately complex with analog and digital will attempt to use four layers with two layers dedicated to power and ground planes or even a possible layer with mixed planes. From there you attemmpt to set your signal layers as vertical on one layer and horizontal on the other layer. Then attempt an autoroute. look at each contention found and determine if part placement can resolve or if additional layers are needed.

Finally, after all traces have been routed, you will need to review each trace carefully to verify routing and trace size. Up to this point in my career I have never blindly trusted an auto-route. I use it as a tool to simplify my work and make the ground work of PCB design easier.

Once I am clear that the traces are good, I then go further by examining my signals and add additional planes for either strong grounds or thermal relief...

On second though it is process and art. You use your knowledge of your design to make critical decisions on trace widths, locations of critical components, Grounding, Power, Thermal relief, matching to the mechanical s/case designs...etc..

A good autorouter is expensive. But worth it.

I recently did a board with 4 independent DDR RAM devices with their address and data lines very densely packed. I had lengthy constraints on all of them and only 4 routing layers (2 for the addresses and 2 for the data). There we also a few hundred other length constrained but less dense nets as well.

After some setup, I had a board which the router would complete to 99.x% in less than 10 minutes. This made it really easy to try out different placements and shuffling things around and see how it worked. I had no "investment" in the routing, just the setup, so I could rip up any time I wanted.

And it all worked first spin too :)

(Mentor Expedition in case you're interested)

PCB auto-quote,
Manufacturing Requirements

Material: FR4
Thickness: 0.4/0.6/0.8/1.0/1.2/1.6/2.0 --unit:mm
Available Layer: 1,2,4,6,8
Min.trace width/space: 4/4mil, 5/5mil, 6/6mil↑ (6mil=0.15mm)
Solder Mask Color: Green /Red /Yellow /Blue /Black /White
Letter Color: White /Black
Copper Weight: 1oz~2oz
Surface Finishing: HASL(lead), HASL Pb free, Immersion gold
Via Plugged: We confirm Via or not according to the gerber file.