The rule 6.6 is not clear for me.
It's clear that for most of smd components the courtyard should be 0.25
mm from pads.
What rules aplly when courtyard isn't determined by pads?
a) should it be 0.25 mm from silkscreen?
b) should it only enclose silkscreen?
c) should it be 0.25 mm from package body and then enlarged to enclose
silkscreen (if necessary)?
I think the c) is best but it's not defined in convention.
In cases b) and c) courtyard will be very close to silkscreen. Should it
be allowed that centre of courtyard line lay on boundary of silkscreen
line (0.025 overlap)? Courtyard is area limited by the line, so it seems
that the 0.025 mm overlap should be allowed, but it may look bad.
Line width for courtyard (0.05) should be defined in convention.
The same clearance for 0204 SMD resistor and 5 W THT resistor is
probably bad idea, exactly that electrolytic capacitors has bigger
courtyard because of bigger placement tolerances. Is there any reason
for using bigger courtyard for THT electrolytic capacitor than for eg
THT radial chockes? Why connectors should have bigger courtyard than eg
mechanical switches?
In document:
http://www.dnu.no/arkiv1/The%20CAD%20Library%20of%20the%20Future.pdf
in chapter 10.3 it's suggested that it's difficult to determine
courtyard for THT.
W dniu 09.01.2015 o 20:21, John Beard pisze:
On Fri, 2015-01-09 at 17:54 +0100, nnn wrote:
There is no information about courtyard line width in kicad library
convention.
Can it be 0.05 mm as suggested in:
http://www.pcblibraries.com/downloads/temp/PCB_Design_Optimization_Starts_in_the_CAD_Library_8685831.pdf
? I used 0.05 eg in Housings_SSOP, so you can check if it looks ok.
Sounds very sensible to me. Since the guy who wrote that is also one of
the people on the committee that approved IPC-7351, this is presumably
consistent with that standard.
Can overlaping courtyard with silkscreen be allowed? It may look bad,
but it's not specified in rule 6.6.
As the "IPC" way now is to draw the main silk screen lines at the
maximum material position for alignment verification purposes, and the
courtyard by definition is outside that, I think it would make sense to
at least say that all silk should be contained within the courtyard?
Otherwise it could be obscured by other components. If the silk extends
up to or outside the courtyard, that may indicate that the courtyard is
too tight.
Cheers,
John
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