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January 2012

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Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Mon, 16 Jan 2012 15:32:51 -0600
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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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