I searched through the Forum posts, but couldn’t quite find anything that answered this question. At this point the situation and question is more of a curiosity than a pressing need, but it might spark some conversation…
Consider that the user may want to keep costs and lead-times low by using only a 2-sided board.
Consider also that it may not be possible to lay out the components across the board in a way that facilitates or optimizes the routing. This may be due to space considerations, heat generation and so forth.
It is conceivable that autorouting might fail to find a solution to the routing problem, given access to only 2 layers…but it is also conceivable that the placement of one (or a few) jumper wires would then solve the routing problem.
Does anybody know of an Autorouting system that determines routing solutions that may include automatically choosing the location of wire jumpers, as needed? I could imagine a system that includes user-defined rules constraining the number of jumpers, the network type (power vs digital signal vs analog signal etc)…
I’ve never seen such an Autorouter.
You might get close to that, with a 3 layer Autrorouter and a high cost applied to that 3rd layer, but PCBs tend to come as 2,4,6 layers, so you would need a higher cost on 2 layers.
I generally avoid auto-routers of the batch-run kind, and instead focus on the Shove Routers.
Using a shove router, you can do what you want, by just (manually) using a spare layer as the jumpers layer, in the rare cases it is needed. When we used to use jumpers, we kept to fixed size choices.
These days you can buy SMD jumpers, which complicates things more : https://media.digikey.com/Photos/Keystone%20Elect%20Photos/5104_tmb.JPG
I had thought about using a 3rd (but only virtual, not real!) layer, and assigning the 3rd layer the function of “jumper connections” only.
In Freerouting, the *.dsn file exported by KiCad appears to contain the layer information and the design rules. So choosing a 3-layer board is not possible, if you are using KiCad—2, 4, 6…etc are the copper layer options, only.
I could be missing something here, so please correct me if I am wrong.
That’s correct, because FABs sandwich double sided layers, PCBs physically usually come in N*2 layers.
If you want to try Autorouters, you could see if they can set differing costs to the layers & experiment.
Another approach would be to define skewed layer cost, Autoroute, and then use manual/shove router to push down the unwanted layers until they are ‘jumper equivalent’ traces.
