For single-sided with Eagle, I turn off the top layer altogether, so it routes 
only the bottom layer.  Then with the resulting set of unrouted traces, I 
move components around and re-route, or manually route some of those.  The 
remaining unrouted traces become jumpers, so for those I just add VIAs in 
appropriate locations.

For double-sided boards that are non-PTH, I do something similar, but prior to 
routing, I place small circles with the tRestrict layer over the component 
pins that are unsolderable on the top.  For any vias that get automatically 
created, I do the same (use a wire), but I enlarge the pads first.

Cheers,
-Neil.



On Monday 30 May 2005 11:36 am, phil B scribbled:
> I've run into this (non-PTH problem) as I often make
> my own PCBs.  Its fairly easy to look at a part/pin
> and decide if you can solder it on both sides -
> resistors, axial caps and diodes, for example.
> Sockets, for example, aren't.   I avoid doing it with
> ICs because of heating issues.  You do need to take
> into account placement/installation order.  So you
> form a set of mental design rules for non-PTH boards.
> Vias can be made with a simple piece of wire soldered
> on both sides.  Its kind of ugly but does work.  I can
> turn a board around in hours rather than days and a
> board designed with the non-PTH rules still works when
> made by a board house.
>
> For the autorouter, you weight the top really costly
> and it will route mostly on the bottom.  But you still
> need to fix up the board to handle the non-PTH design
> rules.  A via will do the trick but I've found its not
> that hard to do it "right" and avoid a via.  I don't
> bother with the autorouter for a number of reasons
> though non-PTH isn't one of them.
>
> Phil


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