Re: gEDA-user: Is it possible to route through ...

[Steve Meier <smeier@xxxxxxxxxxxxxxxxxxx>]

Gene,

My understanding is that the minimum solder mask is dimension is 5 mills
(check with your vendor).  So if you have a solder mask cover of 5.5
mills between pad openings then a trace of 4.5 mills or smaller should
not be a problem. I have used traces as small as 3 mills. I believe for
the copper layers this suggests you should use 0.5 oz copper thickness.

Steve Meier


On Sun, 2008-12-14 at 20:06 -0500, gene wrote:
> 1. A 0.80mm pitch TSOP?  If I have the math right, 0.80 pitch = 31.4 
> mil. Pin width = 0.375mm, = 14.7 mil.  So the clearance between pins is 
> pinPitch - pinWidth,
> = 31.4 - 14.7
> = 16.7 mil
> Assuming equal line/space, I can fit a maximum trace of 16.7 / 3 = 5.5mil
> 
> That assumes my pads are precisely the width of the pin - which doesn't 
> seem to be a very good idea.
> 
> So is this possible?  I'm sure I've seen this done on boards at work.
> 
> 2. Same question, but for a 0.50mm pitch part.  Tougher fit, I think.
> 
> Like I said, I'm pretty sure I've seen this done before, especially for 
> a bus connecting memory devices together.
> 
> gene
> 
> 
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