Electronics Forum | Wed Dec 06 08:29:50 EST 2006 | David
Hi Pavel, We regularly use over printing on a multitude of problem parts including fine pitch QFP's. In an Automotive Environment the only thing you can change without a mountain of paperwork is the stencil. best way to work out how much you can get
Electronics Forum | Fri Dec 22 08:25:18 EST 2006 | aj
Hi, We had issues withthese parts when we first ran them thru our process. As the other lads have said - reduce thermal pad by 35-40%. ( we achieve this by using a dot matrix) . We also offset the lead apertures by 3thou ( i.e sort of overprinting)
Electronics Forum | Fri Sep 14 09:30:29 EDT 2007 | russ
That is inherent issue with lead free, you may want to ask your customer to reconsider this specification, It was probably initiated during the pb days when an exposed pad could signify a reflow issue. Overprinting will give you solderballs and unle
Electronics Forum | Mon Nov 05 15:38:29 EST 2007 | ck_the_flip
As unlikely that this may be, if the RF circuit is sensitive enough, and the minor change in alloy is the only thing that changed, this MAY be the cause. The circuit was probably tuned to Sn63/Pb37. The reason I'm not surprised? I once had a custo
Electronics Forum | Sun May 02 11:36:27 EDT 2010 | jdeluna
I do agree with Jerry: you should apply more paste on it, either with a step stencil, or doing overprint on it by, let's say 120% on Transformer's pad. Also, you need to check : a) there's smooth movement on transport process after the placement, no
Electronics Forum | Thu Dec 17 15:53:32 EST 2020 | dwl
for option 3, if you place the connectors on the first pass then flip the board, won't the protruding leads interfere with second pass stencil printing? My vote would be to overprint onto the solder mask. you can print pretty far and still have it w
Electronics Forum | Sun Aug 06 16:37:00 EDT 2000 | fraser
1. A step stencil is a waste of perfectly good stainless steel! 2. They are characterised by lousy prints on the very parts that are most critical in your process - whilst leaving good prints on the easy stuff. 3. MMM.... nasty chemicals! 4. Exactly!
Electronics Forum | Mon Oct 15 10:51:49 EDT 2001 | davef
On over printing, the general issues are: * Paste deposits being so large that when reflowing, collapse onto many, rather than a single solder mass. * Paste expanding during heating and being close to other solder deposits and bridging [as you say].
Electronics Forum | Tue Nov 25 05:20:20 EST 2014 | grimus
Could be. I am making overprint to achieve proper amount of solder paste inside hole. Now I am trying to reduce maximum overprint and compensate it with step - up stencil. This could reduce effect that some particles of solder paste are not gathering
Electronics Forum | Wed Oct 07 15:25:02 EDT 1998 | Joe P.
Hi Everybody | | Is anyone aware of the possible causes that may lead to voids in the solder bumps after assembly. We assembled some dice on thin substrates and after assembly, void formation in the solder bumps were observed. | We have alread
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