No Graham. It is what prepared me for my time as a consultant. I sure
knew how to shovel the "excrement".......
Doug Pauls
[log in to unmask]
06/22/2011 08:40 AM
To
"TechNet E-Mail Forum" <[log in to unmask]>, <[log in to unmask]>
cc
Subject
RE: [TN] Solderpaste Storage and Use
Hey Doug
It's my understanding that taking care of Fred is what led you to a life
as a cleaning expert... the dialog goes something like "how can we
clean this??? I don't know, but go talk to Pauls, he's an expert on
getting s**t off of stuff..."
regards,
- Graham
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Wednesday, June 22, 2011 10:24 AM
To: [log in to unmask]
Subject: Re: [TN] Solderpaste Storage and Use
I miss that Mammoth. His name was Fred. It was great riding him into
work. Up high with a great view of the area. Trucks got out of MY way.
Handled these 20" Iowa snowfalls with ease. Went through a hell of a
lot
of hay though. I miss the big guy.
Doug Pauls
"David D. Hillman" <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
06/21/2011 07:32 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
[log in to unmask]
To
<[log in to unmask]>
cc
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
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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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