[sdiy] SMD layout tips

[Tom Wiltshire]

On 11 Sep 2012, at 07:15, db wrote:

> 
> Since 100 mil is about 2.5mm, it's not so bad to jump between to get things onto a metric pin, is it?

It's alright to start with, but goes downhill fast. Imagine what happens with a 10-way 0.1" pin header, for example. The first pin is in the right position, the next one is 0.06mm out, the next one is 0.12mm out, and after only 4 pins, I'm halfway between the positions of the 0.5mm grid that the TQFP uses.

Partly also the problem is simply the amount of switching back-and-forth between different grid sizes and units. Makes the whole thing a bit of a faff.

Thanks,
Tom