autorouting setup

Your routing grid should be about 5 to 10 times smaller than lead pitch.

and yes, of course it must include the lead grid or the traces can not

route!

Clearances in DRC are should be determined by the limits of

manufacturing processes and are used to make sure the routed board can

be reliably manufactured, you can set them to whatever limits your board

house can manufacture. Setting them to get a good routing is wrong.

If you want less vias, you can try increasing the "cost" of vias

relative to other entities. The router evaluates which routing is best

by minimizing the "cost" of the entire board, so if you make vias 10x

more costly, it will make eliminating them 10x more important in the

routing process. This will also make routing 10x more difficult for the

computer and perhaps take 10x or even 100x longer.

If you have critical trace alignments, like a hi speed differential

pair, I will tell you that the EAGLE autorouter will never be able to

handle that, do it manually. If you want two traces to be close or far

away, well some software will do this, not EAGLE, do it manually. if you

want your board to have nice patterns on it, that usually means more

you should realize that no autorouter produces work comparable to a

manual routing. the parameters that work for one board will likely not

work so well on the next one. also the various passes of optimization

are usually more important than tweaking the values, lowering the via

count may have a side effect of awkward trace placement for example. the

object is a good balanced outcome for all parameters.

generally, i would start with power and other critical nets and manually

route them first. then i would let the autorouter finish the board if it

is complex.

It is true that EAGLE documentation for the autorouter is weak, but it

is also true that anything critical is normally handled manually, so

there is little interest in tweaking the autorouter, mainly people want

it to get 100% routing. However, if you like to experiment with it and

you think you have improved parameters, I'm sure some will like to try

your tweaked parameters on their board, so please share them with us!

Your routing grid should be about 5 to 10 times smaller than lead pitch.

and yes, of course it must include the lead grid or the traces can not

route!

Clearances in DRC are should be determined by the limits of

manufacturing processes and are used to make sure the routed board can

be reliably manufactured, you can set them to whatever limits your board

house can manufacture. Setting them to get a good routing is wrong.

If you want less vias, you can try increasing the "cost" of vias

relative to other entities. The router evaluates which routing is best

by minimizing the "cost" of the entire board, so if you make vias 10x

more costly, it will make eliminating them 10x more important in the

routing process. This will also make routing 10x more difficult for the

computer and perhaps take 10x or even 100x longer.

If you have critical trace alignments, like a hi speed differential

pair, I will tell you that the EAGLE autorouter will never be able to

handle that, do it manually. If you want two traces to be close or far

away, well some software will do this, not EAGLE, do it manually. if you

want your board to have nice patterns on it, that usually means more

you should realize that no autorouter produces work comparable to a

manual routing. the parameters that work for one board will likely not

work so well on the next one. also the various passes of optimization

are usually more important than tweaking the values, lowering the via

count may have a side effect of awkward trace placement for example. the

object is a good balanced outcome for all parameters.

generally, i would start with power and other critical nets and manually

route them first. then i would let the autorouter finish the board if it

is complex.

It is true that EAGLE documentation for the autorouter is weak, but it

is also true that anything critical is normally handled manually, so

there is little interest in tweaking the autorouter, mainly people want

it to get 100% routing. However, if you like to experiment with it and

you think you have improved parameters, I'm sure some will like to try

your tweaked parameters on their board, so please share them with us!