Leland
I think this is one of those "it depends"(tm.) questions, and you are going to
have to do some experiments to see how your particular process will tolerate
it. The things I'd consider key parameters are:
1) which OSP - some cope with interrupted processing better than others.
2) what flux you are using - no-clean will likely be problematic, OA much more
forgiving of delays.
3) how are you storing them?
In a previous employment I had a large double sided memory card, one key
requirement was that the same brand of memory chips be used on both sides of
the card. The guys running the line would of course not keep track of this,
so we would end up with 10 cards 1/2 built, waiting for the next time we had
that vendor's memory available again. We also treated it the worst possible
way, keeping the board in a dry room at ~45C and ultra low humidity - great
for the MSD issue, but not great for solderability.
It was found, over time, that different OSPs differed greatly in their ability
to cope with this. Of course, that was 12 years ago and unless you are using
a 12 year old formulation I would hope you are getting better results than we
did.
Can you store them in nitrogen?
regards
- Graham Collins
** Note, "it depends" is a trademark of the Doug Pauls Diet Dew Society, used
here without permission.
>>> Leland Woodall 08/13/07 08:49AM >>>
John,
The last thing I want to do is scrap them. The problem is that we have
multi-pin connectors that are impossible to review from the topside,
making vertical fill judgments iffy at best.
I'm just trying to understand at what point OSP board finish can become
unsolderable, and thus, unacceptable.
Unfortunately, using an alternative flux is not an option...
Leland
-----Original Message-----
From: John Burke [mailto:[log in to unmask]]
Sent: Friday, August 10, 2007 7:01 PM
To: 'TechNet E-Mail Forum'; Leland Woodall
Subject: RE: [TN] OSP Processing Recommendations
Why would you want to scrap them? If it is a matter of it already being
assembled might you nto use an aggressive wave solder flux?
What is the visual color condition of the through holes?
John Burke
(408) 515 4992
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Friday, August 10, 2007 3:16 PM
To: [log in to unmask]
Subject: Re: [TN] OSP Processing Recommendations
Richard and John,
At what point would you consider scrapping double sided assemblies that
hadn't yet made it to the wave process (or would that have to involve a
lot of experimentation in order to determine)?
Leland
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Todd, Richard
Sent: Friday, August 10, 2007 5:56 PM
To: [log in to unmask]
Subject: Re: [TN] OSP Processing Recommendations
Wow, John. I would love to use those criteria. Realistically (for us,
at least), we have found through experimentation that no more than 10
days between the 2nd reflow cycle and wave soldering yields acceptable
quality. Of course, the less time the better.
Regards,
Rick Todd
Senior Engineer
Panasonic Automotive Systems
(770) 515-1087 ext. 1087
(678) 458-2887 cell
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Burke
Sent: Friday, August 10, 2007 5:52 PM
To: [log in to unmask]
Subject: Re: [TN] OSP Processing Recommendations
I would say within 2 back to back 8 hour shift cycles (or 16 real time
hours) which is what I use as a rule of thumb for both OSP and silver.
John
John Burke
(408) 515 4992
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Friday, August 10, 2007 2:37 PM
To: [log in to unmask]
Subject: [TN] OSP Processing Recommendations
Everyone,
What is the maximum recommended time to complete all reflow and wave
soldering cycles on product that is coated with OSP?
I'm trying to establish a guideline for my facility and can't seem to
find a lot of related information on this subject.
Thanks in advance for your input!
Leland Woodall
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