[sdiy] PCB CAD woes

[Tom Wiltshire]

Surface mount packages of all types are a nightmare, imho. Unlike through-hole parts, they don't fit on any overall grid. Through-hole parts you can fit on a 0.1" grid. Occasionally, shifting things by a 0.05" here or there helps tidy up.

SMDs are the exact opposite. Even if you want to line them up, you can't. The tracks go all over the place. Spacings aren't consistent. The devices come in a bewildering array of packages, none of which have any common multiples.

Electronics was always a mess, what with there being no real decision made whether we were in imperial or metric (6.35mm shaft or 6mm? 0.1" or 2.5mm? etc etc), but SMD made it a hundred times worse, since the little errors tend to matter much more at that scale.

I commiserate.

Tom


On 2 Oct 2015, at 18:02, Richie Burnett <rburnett at richieburnett.co.uk> wrote:

> Surface mount SSOP packages with either 0.65mm (0.0256 inch) or 0.635mm (0.025 inch) pitch.  Who's bright idea was that!?!?
> 
> Have just laid out a board full of different SSOP packages and now have to redo half of the footprints because they're "slightly" out :-(
> 
> -Richie, 
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