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Subject:	Re:
From:	Jason Gregory <[log in to unmask]>
Reply To:	TechNet E-Mail Forum.
Date:	Thu, 21 Jun 2001 08:26:49 -0500
Content-Type:	text/plain
Parts/Attachments:	text/plain (65 lines)

William,
My experience has been this: if you haven't introduced any oxygen to the container, it should be fine, even a little beyond the exp. date. If it has been opened at all, I never trust it. I do, however, encourage stirring the paste. I have found too many operators in my past lives, just opening a container and scooping it out. My rule of thumb is one minute of vigorous stirring.

Jason Gregory
Software Specialist - NPI Group
SCI Systems/Plant 2
13000 S. Memorial Pkwy.
Huntsville, AL. 35803
(256) 882-4107 x3728
[log in to unmask]

>>> [log in to unmask] 06/21/01 07:55AM >>>
Fellow Techies,

We are getting ready to do a somewhat "extensive" solder paste evaluation
for an SMT operation. What to do seems fairly straight forward using
"standard" tests (wetting, solder ball, slump, etc.), but a concern I have
is age and relative age of the different pastes we are testing. In
practice, we generally use paste within three months of the date
manufacture, so the paste we use is anywhere from one to three months old.
Manufacturers claim good performance for the paste until expiration of shelf
life, but I suspect there could be a difference in performance between fresh
paste and 6 month old paste. Maybe not for all pastes, but probably for
some. My question is, at what age should we test the paste, and does it
matter (significantly?) if some pastes are fresh and others are close to 6
months old, or am I sweating the small stuff by even being concerned about
this?

The pastes we will be testing are no-clean formulations, eg. Alpha LR737, UP
78N, Omnix 5000, Indium NC-SMQ92J, AIM NC 251, Heraeus SC3401HTP, Kester
Easy Profile 256, and Qualitek 691A.

Do we really need to make a science project out of this or should we just go
with something that is popular for the type of application we have and see
if it works on our hardware as long as it meets the standard (J-Std) we are
using?

Any ideas? Thanks for any responses you give.

Bill Mengers
Process Engineer
Northrop Grumman Corp.
Baltimore, Md.

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