On Wed, 12 May 2004 21:14:58 -0400 Dan McMahill <[EMAIL PROTECTED]> wrote:
> On Wed, May 12, 2004 at 11:40:43AM -0700, David Koski wrote: > > On Tue, 11 May 2004 20:28:40 -0400 > > Dan McMahill <[EMAIL PROTECTED]> 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? Yes. There was only a few mils of white arround the pad as expected (maybe 5-10?) > Do you have silk screen thats keeping you from getting closer? Of course the silk screen outline is bigger than the pad but not much. It was not close. I will do a test and capture to image and post it. I should mention that when I reduce parameter that is 315 (Mask) to 0 the problem goes away. But of course the silk screen covers the pad then. David Koski [EMAIL PROTECTED] !.nospham
