The interactive router has nice track width selection by net and custom values, but it doesn’t offer a way to temporarily change the clearance from what I can tell. For example, I often want to make most of a board to a more conservative 10/10 mil width and spacing spec but have some parts that require 8/8 mil leader traces going up to the pads. Is there a good way to do this or is this feature just missing?
I am familiar with net classes and custom track sizes. In order to do this now I adjust the router settings to “highlight collisions” and “allow DRC violations” then fix the traces later, but it would be much more straightforward to route with a different width/clearance pair temporarily.
I’m not quite clear on the issue - Routers do not care about track widths, only clearance.
Usually you would define the 8 mil clearance and route using that, then relax to 10 and DRC and see which outer zone traces need a nudge (ignore the sea of errors inside the 8 mil region)
Or, you just use 8 mil everywhere, and visually clean things up where more space is available.
The PCB FAB charges by the tightest region, so a 10mil area is not buying you much.
Perhaps I chose a bad example since 8 and 10 mils is a pretty small difference. In my case I would want to do this because just because the fab will make down to 8 mil clearance the probability of a board without manufacturing faults is higher if most of it has larger dimensions. In another case you would have a thick power trace (50 mil) that needs to neck down into part with narrow legs.
The features I would expect to fix this is either automatic necking or routing rooms (in altium terms) that have independent width/clearance in certain areas rather than by net. You can use the trace size override in the interactive router to draw similar features, but to change clearances you have to go to the design rules window and type in different numbers or change the net group. Since the interactive router can do automatic DRC checking it is much easier to route when you have the right width/clearances set.
You can change trace-width anytime, using the common rules.
There is a menu item called ‘Automatic neckdown’ but the hover hint is not the same as what you or I might consider neckdown.
(At least, I’ve never seen a true channel neck down occur )
This tickbox seems to control Pad Entry handling.
For now, I think manual neckdown using Q is the router solution.
I am interested in being capable of setting spacing more “dynamically” as well. My situation is that I have BGA components that require relatively tight spacing to escape the pads, but then the traces need to fan out to a given clearance for reducing crosstalk of the signals.