21 thoughts on “Eevblog #93 – pcb autorouters suck”
When I worked at SONY as an R&D tech one of my jobs was PCB layout. One day they asked me to do a manual layout to compare against an autorouter. I looked at it as a sort of John Henry challenge, so I really busted my butt at it. The autorouter produced a real ugly mess with 30 some vias, a few going back and forth between layers twice. Not good at the frequencies we were running at. The senior hardware engineer came into my cube, looked at my completed layout and asked me to turn on all the layers, since all he saw was green traces and pads. I told him, "They are all on." I'd done the layout entirely on the top side of the board except for vias to VCC and GND layers. He went and got our manager to come look at my work. I got a good raise at my wage review. That's been a while. I hope commercial autorouters are better by now.
I used autoruter about 2 times and I had enough of it… Both times I ended up with a board full of extra wires because I just could not hand solder beneath some pieces, which may be no problem for a machine… :S
I used an autorouter to speed up the project of a board someone wanted me to make.
It worked pretty good on a very crowded double-sided pcb. But I will avoid the autorouter as much as possible, because it's not suitable for my projects.
Altium is a pretty expensive and complex tool. I'm happy to use it, but just because I used some other tools which where just worse then altium. There are some annoying bugs and behaviours… Import and export layerstack? Not implemented. Output jobs which export the right layers? Well, try to preconfigure them… Documentation? Plenty but outdated…
On the other hand, they were brilliant to use plain text underlaying all files (realy!) that allows powerful workarounds. But, yeah: It's a tool.
Auto-routers are nice for two things. One is running lots of parallel buses, after you've done a good placement. That's rarely necessary these days, though, with everything going serial. The second is finding routes for those last dozen or so lines on a tight board. Typically slow, non-critical circuits like /reset that wander all over the board. I'll let the auto-router loose on those and let it find a route. Then I'll rip it up and lay it back down cleanly myself.
That must have been a condition of providing "free" or low-cost software. I can't believe any professor would prefer that you use autorouting over manual, especially on something like a single-sided board.
I usually use perfboards instead of making PCBs in part because the routing takes so much time with an autorouter or not (the other part is that I never get it right the first time and modifications are easier on the perfboard). Last device I made has 20 logic chips so if I had a good autorouter and was willing to etch the PCB, it would have saved me some time. I used a perfboard though (with wires I get many "layers" but only 1 layer on a PCB).
I have been manually routing for 15+ years. I had never used autorouting. I just recently tried it – and LOVE IT! Of course, you have to SET IT UP to perform properly or you'll get garbage. I'll manually route critical stuff…but I'm an autorouter for life.
@jpelczar For high speed stuff you are forced to use a large number of layers to get the ground planes required for impedance control. Once oyu have all the layers, manual routing gets much easier.
It shoudln't take you long to see that autorouters suck. I sometimes use it for a single wire to save me some clicks, but that's it.
I'm only doing "home" projects (most things with an Atmel AVRs), but routing is actually a really a fun part of a project for me. I see it as some kind of game. If you can still see the board, the components aren't close together enough 😉 .
@zekonja24 I use Ultiboard to create my layouts. It has the ability to snap to 25 mills. I'm going to try it. I designed a +/-15V regulated supply with a variable heater supply for a tube preamp. Now, I just need to create a smart layout that will be good for interconnection in my chassis.
How do you feel about autoplacement? I would like to know more about PCB layout because I really don't want to have to resort to the automated means. They turn out bad results.
When I worked at SONY as an R&D tech one of my jobs was PCB layout. One day they asked me to do a manual layout to compare against an autorouter. I looked at it as a sort of John Henry challenge, so I really busted my butt at it. The autorouter produced a real ugly mess with 30 some vias, a few going back and forth between layers twice. Not good at the frequencies we were running at. The senior hardware engineer came into my cube, looked at my completed layout and asked me to turn on all the layers, since all he saw was green traces and pads. I told him, "They are all on." I'd done the layout entirely on the top side of the board except for vias to VCC and GND layers. He went and got our manager to come look at my work. I got a good raise at my wage review. That's been a while. I hope commercial autorouters are better by now.
Besides, routing tracks is fun. Why give that up to the machine.
I used autoruter about 2 times and I had enough of it… Both times I ended up with a board full of extra wires because I just could not hand solder beneath some pieces, which may be no problem for a machine… :S
Why even bother with autoplacement at all?
I used an autorouter to speed up the project of a board someone wanted me to make.
It worked pretty good on a very crowded double-sided pcb. But I will avoid the autorouter as much as possible, because it's not suitable for my projects.
Altium is a pretty expensive and complex tool. I'm happy to use it, but just because I used some other tools which where just worse then altium. There are some annoying bugs and behaviours… Import and export layerstack? Not implemented. Output jobs which export the right layers? Well, try to preconfigure them… Documentation? Plenty but outdated…
On the other hand, they were brilliant to use plain text underlaying all files (realy!) that allows powerful workarounds. But, yeah: It's a tool.
Auto-routers are nice for two things. One is running lots of parallel buses, after you've done a good placement. That's rarely necessary these days, though, with everything going serial. The second is finding routes for those last dozen or so lines on a tight board. Typically slow, non-critical circuits like /reset that wander all over the board. I'll let the auto-router loose on those and let it find a route. Then I'll rip it up and lay it back down cleanly myself.
That must have been a condition of providing "free" or low-cost software. I can't believe any professor would prefer that you use autorouting over manual, especially on something like a single-sided board.
I usually use perfboards instead of making PCBs in part because the routing takes so much time with an autorouter or not (the other part is that I never get it right the first time and modifications are easier on the perfboard). Last device I made has 20 logic chips so if I had a good autorouter and was willing to etch the PCB, it would have saved me some time. I used a perfboard though (with wires I get many "layers" but only 1 layer on a PCB).
@EEVblog Haha, I've never meant the autorouter, I'm talking about Altium in general. But you're right, it's autorouter is just a huge joke!
@Schmiki24 Altium's autorouter is universally regarded as the worst in the business. I
Use Altium!
I have been manually routing for 15+ years. I had never used autorouting. I just recently tried it – and LOVE IT! Of course, you have to SET IT UP to perform properly or you'll get garbage. I'll manually route critical stuff…but I'm an autorouter for life.
@jpelczar For high speed stuff you are forced to use a large number of layers to get the ground planes required for impedance control. Once oyu have all the layers, manual routing gets much easier.
@superdau Routing is almost like art!, and it can be fun and challenging.
It shoudln't take you long to see that autorouters suck. I sometimes use it for a single wire to save me some clicks, but that's it.
I'm only doing "home" projects (most things with an Atmel AVRs), but routing is actually a really a fun part of a project for me. I see it as some kind of game. If you can still see the board, the components aren't close together enough 😉 .
@zekonja24 I use Ultiboard to create my layouts. It has the ability to snap to 25 mills. I'm going to try it. I designed a +/-15V regulated supply with a variable heater supply for a tube preamp. Now, I just need to create a smart layout that will be good for interconnection in my chassis.
@EEVblog Where do I learn how to do it correctly? I'm an EET student. Thanks buddy; great videos!!
@fingerboy18 Autoplacement is an order of magnitude worse than autorouting.
How do you feel about autoplacement? I would like to know more about PCB layout because I really don't want to have to resort to the automated means. They turn out bad results.
I use FreePCB … Really a great program. Total control.
It's my favorite part of a project, to spend hours and hours manually route my PCB, to make it nice… Really!