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From:
Paul Edwards <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Paul Edwards <[log in to unmask]>
Date:
Wed, 22 Jun 2011 14:20:56 -0700
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That's why I used o-rings and only slowly rolled sealed jars or cartridges...

Paul

Paul Edwards
Process/Quality Engineering
Surface Art Engineering


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Tuesday, June 21, 2011 12:10 PM
To: [log in to unmask]
Subject: Re: [TN] Solderpaste Storage and Use

It was quite a while ago, but I seem to remember trying one of those "hot
dog roller" do-hickies and discovering that depending on how tight the lids
were on the jars, what direction the jars were placed on the rollers, you
could come back later and discover that it had actually unscrewed the lid
off the jar! I remember it was quite the mess!

We went back to mixing the jars by hand after that I think...

Steve

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Tuesday, June 21, 2011 12:52 PM
To: [log in to unmask]
Subject: Re: [TN] Solderpaste Storage and Use

We've used the Malcom solder paste spinner units for years with great
results.  We have two, one for jars and the other for tubes.  They're
pricey but reliable, and perform according to their ads.  They both mix
the paste and bring it to room temperature within 10 minutes.

http://www.malcomtech.com/Electronics/products_sps.html

Never tried the hot dog rollers, but that's thinking outside the box!

Leland


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Tuesday, June 21, 2011 9:01 AM
To: [log in to unmask]
Subject: Re: [TN] Solderpaste Storage and Use

LOL. Hi, Dave. Good to hear from you.
I totally agree with you. I only purchase paste in tubes, whether the
larger Semco tubes (500 or 600 gram size) or the smaller 50cc cartridges
that are now available. The jars just don't cut it.
In fact, I have found the jars without the inner sealer, the plastic
disk that is used to keep moisture out. When I asked what happened to
it, one operator told me she throws them out because they get
contaminated with paste! She stated it "does a grody on my nail job".

You can just imagine my sympathy.

However folks, keep in mind that the paste will separate inside the tube
over time to some extent. Not sure how the hot dog rollers will work
inside the refrigerator. I really think that the centrifuge is a good
idea. Probably pays for itself within a year in reduced print defects.


From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Tuesday, June 21, 2011 7:32 AM
To: TechNet E-Mail Forum; Stadem, Richard D.
Cc: [log in to unmask]
Subject: Re: [TN] Solderpaste Storage and Use


Hi Richard - good discussion and information! One comment to add - one
of the advantages of we have with solderpaste shelf/use life today that
we didn't have back when Doug rode his Mammoth to work is today's modern
packaging. The SEMCO tubes only expose the solderpaste to surrounding
environment conditions at its ends - a drastic contrast to opening up a
jar of solderpaste. And the folks who are using the sealed cartridges
also have excellent isolation. Not exposing the solder paste to the
surrounding environment any more than necessary for use has been a key
parameter in storage/use time.

Dave Hillman
Rockwell Collins
[log in to unmask]


"Stadem, Richard D." <[log in to unmask]> Sent by: TechNet
<[log in to unmask]>

06/20/2011 04:48 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to "Stadem,
Richard D." <[log in to unmask]>


To

<[log in to unmask]>

cc

Subject

Re: [TN] Solderpaste Storage and Use







Please note that solder paste re-certification after shelf life
expiration IS allowed, and the methods are listed in the solder paste
standard (J-STD-005), including the test methods from IPC-TM-650 and the
forms to be used for re-certification.

I have done it several times on many different types of paste and
different brands, for multiple client companies. I have performed a
combination of viscosity tests, printing tests including tact time and
open stencil life, and monitored the DPMO of the product that expired
lots were used on. The particle size, flux type, leaded or non-leaded
alloy did not make any difference.

The only thing that mattered (affected the outcome of the test) is the
amount of flux separation that occurred while the paste was in storage,
and I only found this to be an issue on ONE major brand of paste (don't
ask, I won't tell). However, even that paste had zero shift in
comparison to the controlled samples when properly mixed.

Not surprisingly, expired paste up to 6 months past expiration that had
been properly refrigerated throughout its entire 12-month storage life
showed absolutely no difference from paste that had been stored and
tested exactly the same way BEFORE it expired at 6 months. The six sigma
test showed a 99% level of confidence there was no difference in defect
data. (P-value test)

What was really surprising was the overall DPMO. The number of solder
paste defects as seen during the paste print inspection actually
improved when expired paste was used!
Also, the number of solder joint defects seen after reflow also
improved! This was done using surreptitious testing to avoid any
Hawthorne effect from the inspectors and operators.

All pastes used are now mixed in an automatic centrifuge made for that
purpose and the viscosity tested. This eliminates the "sitting at room
temperature for 8 hours" and assures the viscosity is good from the
start. The right centrifuge (and the right settings) will provide the
exact same viscosity and paste temperature every single time a tube is
removed from the fridge, once you have established what that mix time
is.

So, for certain part numbers of solder paste from certain companies, I
recommended that the shelf life be permanently extended to 1 year, with
no re-certification requirement after the original 6-month shelf life is
expired. Remember, this was based on data from repeated testing of
several lots over time, and the resulting data was carefully reviewed by
both the client company and its customers. It took a little time to
develop that database, but it has paid off several times over when
smaller EMS companies needed to purchase larger lots of paste than they
could use within the shelf life (most distributors require a minimum buy
of 20 tubes or so).

A single lot of RMA paste "failed" (displayed much worse test results
than other candidates during evaluation), but it failed from both the
lot sample not yet expired, and the lot sample that was 8 months old and
opened for the first time. The reason why? It was shipped from the
manufacturer in July, was not kept refrigerated during storage at the
distributor, and as it turns out, the paste manufacturer re-marked the
lot expiration date. How do I know? Because when I went to pick it up
from the distributor, they had ALL of their inventory stored on a shelf
at room temp, and when I inspected the paste I found the same C of C
used on two different lots with the same date of manufacture, but
different expiration dates! Another lot of RMA paste failed because it
was shipped frozen in dry ice; that is the worst thing you can do to an
RMA paste.

So, if you really want to fix your solder paste handling issues, you
need to control the paste from the manufacturer, certify only
distributors you can audit periodically, and make sure your purchasing
requirements detail the proper handling, storage, and shipping methods
up to and including the dock door (paste should be removed from the
insulated container and placed into the refrigerator within one or two
hours from receipt). You absolutely must have some type of internal
documentation, training, and auditing system to ensure the paste is
stored and controlled correctly once received.

Please don't use expired paste based on what I just told you. You need
to ensure you have all of the qualification done to validate YOUR
particular purchasing, storage, and handling methods for your particular
paste. It takes very little time, but once done, it pays off over and
over.

Does this all seem like a bit of overkill to you? No problem; never mind
then, just go back out and support the factory doing all that solder
touchup.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Monday, June 20, 2011 2:26 PM
To: [log in to unmask]
Subject: Re: [TN] Solderpaste Storage and Use

Hi,

I do wonder where all these shelf live ideas comes from. Seems to me
that particle  size and flux type will make a BIG difference, like a
power of 10 or so.

A no clean type 3 paste with low levels of activity would seem (at least
to
me) to last MUCH longer than say type 5 in an active OA flux.

Has anyone ever done reflow studies for different types of old paste? I
don't think a paste manufacturer would do such a test, I expect to get
blasted for even suggesting the idea.

But, Look at this link:

  http://www.endtimesreport.com/Prescription_longevity.html


Bob K.


Hmmm, I have a bucket of ancient paste tubes. I should give them a try.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Roger Mack
Sent: Monday, June 20, 2011 3:12 PM
To: [log in to unmask]
Subject: Re: [TN] Solderpaste Storage and Use

Most pastes have a refrigeration spec. which gives it  a shelf life of 6
months. If you are using 600g tubes most datasheets will require 8 hours
to acclimatise. Once out of the fridge we don't return it either, but
always sign initials, date and time on each tube. Create an out of
fridge "on deck"
storage for 3 or 4 tubes, or a daily amount for a line. We use a fixture
that fills from the top and you pull tubes from the bottom like a canned
drink dispenser. If you take one, add a new one to the top from the
fridge.
You will never run into trouble with your acclimitizing time, or pull
too much. Your paste likely has a shelf life for room temperature, so
set a spec. that discards all open tubes when pulled, for say, two weeks
or a month.  If you are using jars and storing working paste, sign and
date it as well and control the out of fridge time for that as well.



Roger Mack  P.Eng.
Manufacturing Specialist
Parker Hannifin Canada
Electronic Controls Division
1305 Clarence Avenue
Winnipeg, MB  R3T 1T4 Canada
direct 204 453 3339 x373
[log in to unmask]
www.parker.com/ecd







From:
Amol Kane <[log in to unmask]>
To:
<[log in to unmask]>
Date:
06-20-2011 13:27
Subject:
[TN] Solderpaste Storage and Use
Sent by:
TechNet <[log in to unmask]>



I am re-writing our solderpaste use and storage procedures for water
soluble and no clean fluxes (SnPb and Lead-free) to say, in essence the
following:

"To be stored per the manufacturer's recommendations (usually upto 10C),
must be at room temperature before it is dispensed on the stencil (at
least an hour thawing is required). Maximum use period to be 8 hours.
Re-refrigeration and use beyond 8 hours not permitted"

The pushback is to the prohibition of re-refrigeration (for use the next
day) after it is thawed and use beyond 8 hours requirement. These
requirements are due to concerns with moisture absorption by the
solderpaste once thawed (affecting slump) and flux activity (due to
ageing)

What criteria are all the learned folks on technet using for solderpaste
management? Is there any literature available that looks at solderpaste
use limits on time and temperature?

A logical solution would be to do a DOE to look at these parameters, but
I
am being asked to come up with something ASAP:).   love how these things
work!




Thanks in advance


Amol


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