Seeking correct EuroCard dimensions

Eric Smith spacewar at gmail.com
Fri Jul 28 18:52:04 CDT 2017


On Fri, Jul 28, 2017 at 5:16 PM, David Griffith via cctalk <
cctalk at classiccmp.org> wrote:

>
> I'm trying to verify the correct dimensions for a 160mm x 100mm EuroCard.
> I figured this would be simple: 160 millimeters by 100 millimeters.  But
> when I submitted a template to the Kicad project at
> https://github.com/KiCad/kicad-library/pull/1441.
>
>
> I was told that I need to trim the board back by .15mm, citing this
> document: https://www.elma.com/-/media/general-web-content-files/resou
> rces/pdfs/us-corporate-dimensions-of-pcbs-d.ashx?la=en&hash=
> 13B1EAF4FF743087F8B7E87BB10A1D20C44C40BD
>
> This doesn't seem to make sense to me.  I always thought that the bearing
> surfaces on the card cage would be spaced slightly more than the card
> width.  What's going on here?  What am I missing?


I think what they're saying is that the board size specs have a tolerance
of +0.0/-0.3mm, so you should spec 0.15mm less than nominal to be right in
the middle of the tolerance range, so that any positive tolerance variation
from manufacturing should still be within the specification.

I'm in the process of designing some 220x100 mm Eurocards myself, and
hadn't previously given the tolerance limit of +0.0mm any consideration. I
think the advice to trim 0.15mm is good.

Eric


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