Here are old stuff: if you only have few solder paste in the plant, shear rate possibly the 1st indication you got something start changing (two speed viscosity measurement, check the slope). The slump, the viscosity change, the oxidation, paste saperation, etc. would most likely effect the shear rate. However, you do need establish a base line upon qualification of paste over the whole duration of shelf life, bench mark what you can use/can't use using (1) transfer efficiency, (2) yield (3)slump time, etc. to ensure it is within your process window. If you have expired tube in front of you, but little or no prior data, it is hard to say what is acceptable or not (impact on yield may be difficult to spot, depend upon how large is your sample size and how close is your "cutting edge" or "bleeding edge" design requires). I am usually stay on the safer side (if only 2 tube left, I got fresh stuff, I'll just use the new stuff... when you tested and re qualed, the money is possibly the same as use new stuff... Unless you have a LOT of that expired stuff... ).
Joyce Koo
Materials Researcher - Materials Interconnect Lab
Research In Motion Limited
Office: (519) 888-7465 79945
Mobile: (226) 220-4760
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Monday, January 16, 2012 4:33 PM
To: [log in to unmask]
Subject: Re: [TN] Expired Solder Paste
Well, I'm certainly glad I am not the only one who has observed that.
When performing solder paste evaluations I have observed:
-Excessive separation of flux and paste, such that liquid flux pours out of the sealed cartridge when you remove the cap. Not just a couple of drops, but perhaps 4 or 5 ounces. When I contacted the vendor they asked me if I had mixed it properly before use. Never mind, not using that. This paste was two weeks from manufacturing date.
-Excessive slumping upon printing onto a room temperature PWB. This was fresh paste. It would not hold any definition at all at room temperature. Major brand of paste. Vendor said that the PWBs needed to be refrigerated and kept cold while printing. I don't think so.....
-Wrong paste in tubes. Tubes were labeled as water-soluble/lead-free. Were actually Sn63/RMA flux. Not kidding.
-Right paste, wrong size. Labeled as a Type 4 paste, but was actually a Type 3.
-Wrong alloy, right flux. Labeled as SAC305 no-clean. Was Sn63 no-clean.
If I found this just on the paste candidates I personally evaluated, what do you think happens in production?
In addition to the above, I have seen paste fail many times at various CEMs because of poor paste handling practices, but that is another chapter.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: Monday, January 16, 2012 2:27 PM
To: [log in to unmask]
Subject: Re: [TN] Expired Solder Paste
We have seen solder paste fail within its specified shelf life. The thread I
mentioned as worthwhile in the archive discusses the various failure modes.
In my experience early failures involve the solder balling, hot slump, and
poor printing especially when pushing limits, small apertures, and less than
optimal aspect rations. This especially true with pastes designed for
dispensing.
Guy
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: Monday, January 16, 2012 2:47 PM
To: [log in to unmask]
Subject: Re: [TN] Expired Solder Paste
Matthias,
I also have used polymers and solder well beyond their expiration date FOR
PERSONAL USE with very good success.
For me the critical aspect of being able to trust the material is knowing
that ONLY I have been into it. If someone else were to get into my stash as
well, I would not be as confident of the materials characteristics.
You likely have the same observations.
FWIW
Steve Creswick
Sr Associate - Balanced Enterprise Solutions
http://www.linkedin.com/in/stevencreswick
616 834 1883
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Matthias Mansfeld
Sent: Monday, January 16, 2012 1:37 PM
To: [log in to unmask]
Subject: Re: [TN] Expired Solder Paste
On 16 Jan 2012 at 8:17, Stadem, Richard D. wrote:
> You can re-certify expired solder paste per J-STD-005 section 6.0.
> Used the form attached therein, and follow the appropriate test
> methods (also listed at the end of J-STD-005, #2.4.34, 2.4.34.1,
> 2.4.34.2, 2.4.34.3 for the viscometer you wish to use. You should
> always perform first article testing, monitor your PPMO, etc., and
> document all product run with the re-certified paste.
For what it's worth, a good solder paste, stored under good
conditions may work well even years after expiration. Been there,
done that without re-certification (don't worry, no customer
projects, just some own DIY-stuff....). For this stuff I use still
the same 1kg-jar with old Sn63Pb Alpha RMA390D3K from 2003.... prints
well, tacky like new, and visually perfect, shiny solder joints...
even 8 years after expiration date.
Best regards
Matthias Mansfeld
--
Matthias Mansfeld Elektronik * Leiterplattenlayout
Neithardtstr. 3, 85540 Haar; Tel.: 089/4620 093-7, Fax: -8
Internet: http://www.mansfeld-elektronik.de
GPG http://www.mansfeld-elektronik.de/gnupgkey/mansfeld.asc
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