kicad-developers team mailing list archive

[Lorenzo Marcantonio <l.marcantonio@xxxxxxxxxxxx>]

On Sun, Jun 01, 2014 at 10:42:33PM +0100, John Beard wrote:
> I have never registered erasure of silk over pads as a problem, no
> fabricator has ever complained or delivered over-printed pads. Has
> anyone seen this happen?

Neither have I. Simply because our fabricator erase everything in 0.2mm
of the pad... silk screen registration and (most important) solder mask
registration are usually guaranteed process parameters. Typically it's
the mask enlargement (about 0.1-0.2mm, depending on the kind of
stencil).

> when assembled.  When hand assembled by hobbyists and amateurs (like
> me!) at least, having a nice graphic of what is going in that spot
> can be helpful.

Obviously this is not the target of IPC wannabe-standards (in the
C revision they changed the rounding to 0.01 from 0.05 and the C-minimum
environment as the default!) however you see in the wild high-volume
boards (PC motherboards) with, for example, round aluminum caps with the
silk half filled to mark polarity.

> I have never had a problem with fabricators and overhanging silk, I
> imagine it's fairly easily dealt with as a matter of course?

Every CAM in the world (easy to check, there are maybe 4 of them on the
market...) has a 'trim to board edges' function, exactly as a 'remove
pads from silk' function.

> I meant for these SMD connector headers. The Library Expert Lite
> software doesn't seem to include these?

SMD pads are generated depending on pin type, not on component type. BTW
the THT rules are in 7251 (still a working draft, too!). I'd use the
SODFL rules for these, since they have flat pins (not bent or
gullwings).

Seems that IPC is not exactly fast in churning out standards... too bad
for them, because they sell them:P Here is the page containing both the
7251 draft and the 7351C expected modifications:

http://www.ipc.org/committeedetail.aspx?Committee=1-13

> Indeed. I would even put it on a D-sub, just so its right there when I
> need it! The last thing needed when fiddling with cable harnesses is a
> last-second self-doubt over the PCB pin location!

Right, I forgot there are IDC D-sub connector on the market...

-- 
Lorenzo Marcantonio
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