[sdiy] SMD layout tips

[Tom Wiltshire]

Hi All,

Having sorted out my problems with tight-pitch TQFP uPs and got lots of suggestions for places that could easily produce such a board, I'm now looking for layout tips.

The processor has legs on 0.5mm pitch - e.g. metric. Many of the connectors are on 0.1" pitch - e.g. non-metric.

I'm having trouble getting anything that looks even reasonably tidy, since I'm having to jump back and forth between metric and non-metric grids, and things that line up in one don't line up in the other, etc etc. Particularly difficult are tracks where one end is on a metric grid and the other end is on a non-metric grid. Add extra complexities if the track needs to go from very thin at the uP (0.29mm) up to some more reasonable size.
It seems to go like this:
Select thin track, start at uP, do short length, change track size, do short length, change track size, do short length, change track size, change grid size, change grid units, do final track to connector.
All this to do one simple track from one pin to another, less than an inch long! Is this what's required?! It takes an age!

Many of you must have dealt with these problems already. Any tips for good SMD layout would be much appreciated.

Thanks,
Tom