Dave,
PCBExpress requirement of a clearence around the pads of at least 8
mills meets the IPC specifications for silk screened soldermask.
For the geometry of the TSSOP-20 with a lead pitch of 26 mills and lead
widths of 10 Mills your soldermask width between pads would be zero. As
you stated.
I
That's interesting information, thanks.
I'm thinking I misintrepreted "mask swell" to mean .008 copper-to-mask,
as opposed to mask diamater = pad diameter + 0.008, which would yield
.004 mask-to-copper. If so, then I end up with .008 of mask between
pads. In any case, I need to verify with t
One shop I work with asks for soldermasks to be at least 5 mills wide.
If you have two adjacent pads with solder mask between the pads that
soldermask should be at least 5 mills wide. So I suspect for PCBexpress
that they need the soldermask to be at least 8mills wide. The issues has
to do with ali
Thanks, very helpful. That seems like the correct interpretation of
their use of the word "swell".
-dave
DJ Delorie wrote:
Below a certain pitch, mask becomes almost useless, because the solder
will bride from pin to pin anyway. The challenge boards are 0.50m and
0.40mm pitch and neither ha
Below a certain pitch, mask becomes almost useless, because the solder
will bride from pin to pin anyway. The challenge boards are 0.50m and
0.40mm pitch and neither has mask between the pins. What seems to
work for me is to just glob on the solder, then go over it with a
desolder braid where ne
Here is the rule in question from PCBexpress web site:
Solder mask swell is at least .008 larger than copper surfaces to keep
mask off pads.
Am I interpreting that correctly? That I need .008 all around the
copper pad? Or is a mask .008 wider than the pad sufficient?
-dave
Dave N6NZ wrot
Thought I just saw a thread on this topic, but I deleted the whole works
and can't find it in the archives.
I'm trying to reconcile a data sheet for a TSSOP-20, 0.65mm lead pitch
package with PCBexpress's design rules. The problem: 26mil l.p. and
10mil pad width leaves 16mil btw pads. The ru
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