[PCB_FORUM] Re: Strange solder paste mask creation... how to??
- To: <icu-pcb-forum@xxxxxxxxxxxxx>
- Date: Wed, 17 Nov 2004 13:53:32 -0600
That is a very workable solution.
Another method is to "add pins to the package" so that it is always
present in your symbol. And then
The paste opening is part of a pin. That's the digital world method ;-)
-----Original Message-----
From: MAILER-DAEMON@xxxxxxxxxxxxx [mailto:MAILER-DAEMON@xxxxxxxxxxxxx]
Sent: Wednesday, November 17, 2004 2:42 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Strange solder paste mask creation... how to??
OK here is one for the group...
We work with some rather strange shaped parts in the RF world... things
that are built the way they are built, due to physics, not some IPC or
JEDEC suggested "standard" footprint. (you digital folks are lucky... )
These footprints often have large odd shaped center "slugs" in the
middle of the package that needs to be soldered for RF ground and
heatsink reasons. Rather than put an equal amount of solderpaste on the
slug (in other words a 1:1 solderpaste "pad" equal to the component
"pad") we have found that smaller solder paste shapes work better... the
part will then not "float" on the huge center pad, which can cause the
outer, smaller pads to not solder correctly. Making smaller solder dots
and stripes on the center "slugs" roughly the same size as the other
connection pads works best.
Well, the problem with this is defining what ends up as several "pads"
for pastemask verses one (odd shaped) "pad" for the slug.
It looks as though the best solution, at this point, is to put the paste
mask on a new subgroup layer: package geometry pastemask_top and
pastemask_bottom... this permits us to add any unusual hourglass
shapes, dots or stripes, or whatever as recommended by the manufacture
as needed.
I am just wondering, are there any other better solutions?
Gene Carman
gcarman@xxxxxxxxxxxxxxx
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