Couldn't you temporarily mask the bottom of the vias with tape, then remove
the tape after reflow? Wouldn't the void be open on the bottom side of the
board?
Jim Marsico
Senior Engineer
Production Engineering
EDO Electronics Systems Group
[log in to unmask] <mailto:[log in to unmask]>
631-595-5879
-----Original Message-----
From: Marki Sasportas [SMTP:[log in to unmask]]
Sent: Tuesday, March 05, 2002 7:00 AM
To: [log in to unmask]
Subject: Re: [TN] Via in Pad? Need Help!!!
Hello Siggi,
We had the same problem,
1) Using HASL finish to the board will not help you because as Brain
Ellis
said the amount of solder that drains down the via is much more then
you
supply (coat + print )- we tried it without success.
2) DO not Mask the Vias from the bottom side it will cause very big
voids.
3) You can try to seal the vias with paste but note that if it will
have
height it can cause problem during printing.
4) I recommend you to use blind microvias or just take the holes out
of the
pads.
Regards,
Marki Sasportas.
-----Original Message-----
From: Zweigart, Siegmund [mailto:[log in to unmask]]
Sent: Tuesday, March 05, 2002 9:53 AM
To: [log in to unmask]
Subject: Re: [TN] Via in Pad? Need Help!!!
Hello Ken
We had the same problem (or still have).
We tried HASL and OCC Boards but there was no difference.
We also tried plugging with a special stencil and 63/37 but this
don't
works.
We did not try a high temperature solder.
Masking is quite critical because of voids.
Beside redesign you have only one chance: Look for new process
parameters.
Siggi
----------
From: Ken Patel [SMTP:[log in to unmask]]
Sent: Montag, 4. März 2002 23:37
To: [log in to unmask]
Subject: [TN] Via in Pad? Need Help!!!
Importance: High
Guys,
On our nickel gold board, solder joints are below IPC spec
(insufficient
solder) where there are vias in pad. Solder is drained down
the via
holes and deprived the joint of necessary solder. I would
like to
know
the following.
(1) How about using the surface finish 63/37 coating HASL
instead of
Ni-Gold? I think gold dissolves in solder so quickly that I
rather
use
HASL processed boards, any thoughts?
(2) Do you guys mask the via on bottom side to avoid solder
draining
out
on the other side?
(3) Does anybody try Hi Temp solder paste to fill the vias
as our
assembly house ordered via stencils to fill the via using
eutectic
(63/37) solder paste which didn't work?
Looking for
re,
Ken Patel
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