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Mail Archives: geda-user/2014/02/24/02:54:05

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Date: Mon, 24 Feb 2014 08:51:31 +0100
From: Gabriel Paubert <paubert AT iram DOT es>
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] Smallest clearance and mask in pcb
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On Sun, Feb 23, 2014 at 04:41:40PM -0500, DJ Delorie wrote:
> 
> I typically leave 3mil between mask and copper.  "clearance" is
> copper-copper so should be the same as the line/space rules (typically
> 6-10mil).

Actually my preferred PCB manufacturer announced last week 
that they reduced their prices and that from now on the standard
without surcharge would be 100µm (~4mil) line/space and and 
0.2mm (~8mil) drill holes. The previous standard were 150µm (~6mil)
and 0.3mm (~12mil).

I therefore tried to change a few vias in a board I was designing
and hit a stupid PCB limit: it would not let me change via diameters
to less than 20mil. But I wanted 0.5mm and 20mil is 0.508mm.

I have applied the following stupid patch to my tree, but I'm 
convinced that it's wrong. I could understand a minimum pin size,
but for a via, the minimum should be the minimum drill size plus
twice the minimal anular ring (which can be very small with laser
drilled microvias, something the PCB does not yet support).

	Gabriel
 
diff --git a/globalconst.h b/globalconst.h
index e0779d5..b398692 100755
--- a/globalconst.h
+++ b/globalconst.h
@@ -77,7 +77,7 @@
 #define	MAX_LINESIZE		LARGE_VALUE
 #define	MIN_TEXTSCALE		10	/* scaling of text objects in percent */
 #define	MAX_TEXTSCALE		10000
-#define	MIN_PINORVIASIZE	MIL_TO_COORD(20)	/* size of a pin or via */
+#define	MIN_PINORVIASIZE	MIL_TO_COORD(10)	/* size of a pin or via */
 #define	MIN_PINORVIAHOLE	MIL_TO_COORD(4)	/* size of a pins or vias drilling hole */
 #define	MAX_PINORVIASIZE	LARGE_VALUE
 #define	MIN_PINORVIACOPPER	MIL_TO_COORD(4)	/* min difference outer-inner diameter */


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