Re: gEDA-user: solder masks, etc.

[Dan McMahill <dan@mcmahill.net>]

On Wed, May 12, 2004 at 11:40:43AM -0700, David Koski wrote:
> On Tue, 11 May 2004 20:28:40 -0400
> Dan McMahill <dan@mcmahill.net> wrote:
> 
> > On Tue, May 11, 2004 at 12:42:17PM -0700, David Koski wrote:
> > > Hello,
> > > 
> > > In the following file:
> > > 
> > > http://kosmosisland.com/island/david/test_1.pcb
> > > 
> > > I have a SOT-428_Transistor (Q1) footprint that I made. With a solder mask as
> > > shown in the file, I cannot get the large pad closer than about 170 mils from
> > > the edge of the board. It is as close as it can get in the above referenced
> > > board. If I make the solder mask parameter small, the pad can be placed next to
> > > the edge of the board. What am I missing?
> > 
> > I think PCB is preventing the soldermask relief from extending beyond the
> > edge of the board.
> 
> That is what I thought. But it doesn't seem to add up. Using the following example:
> 
> Pad(0 -92 0 -92 275 20 315 "" "2" 0x00000100)
> 
> Thickness: 275
> Clearance: 20
> Mask:      315
> 
> I expect a 10 mil clearance between the pad and any polygon (Clearance
> parameter/2). [Land Pattern Creation for Thomas Nau's and Harry Eaton's PCB,
> Stephen Meier, May 2, 2003, {Example 2}]
> 
> I expect a margin between the pad and solder mask to be 20 mils ((Mask
> parameter/2)-(Thickness parameter/2)). [Land Pattern Creation for Thomas Nau's
> and Harry Eaton's PCB, Stephen Meier, May 2, 2003, {Example 3}]
> 
> But given a Mask parameter of 315, I cannot get closer than about 170 mils from
> the edge of the board. I'm still missing something.
> 

Did you try selecting Screen->Show Soldermask in PCB to show the soldermask relief?

Do you have silk screen thats keeping you from getting closer?

-Dan

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