Jason,
Are you doing an entire battery of tests like we are proposing? What type
of hardware are you building? We do mostly solder coated polyamide boards
down to 20 mil pitch j leads, gull wings and now of course we are getting
into 20 mil pitch BGA's. What you said about the tubes and bladders makes a
lot of sense to eliminate another set of variables. Thanks.
Bill
-----Original Message-----
From: Carl Ray [SMTP:[log in to unmask]]
Sent: Thursday, June 21, 2001 10:14 AM
To: [log in to unmask]
Subject: Re: [TN]
William,
We are in the process of performing a solder paste evaluation
here (Sanmina) as well. We have decided to only evaluate solder pastes using
two different types of packaging method. We have DEK Horizon, 265GS, MPM
3000 and Fuji GSP2 Printers in house. So we utilize "bladder" and tube paste
dispensing methods.
We find that the use of "jars" offers process variables such as
operators mixing older paste in with fresh paste. Operators have also been
know to put the solder paste from a single shifts production run in the
original jar is cam packaged in. Store this container overnight in a
refrigerator and the next morning reuse the jar from the previous days
production run combined with
a fresh jar. Needless to say we use to have several process issues.
Tubes offer the opportunity to control the distribution of the
paste as well. Most Printers have the ability to dispense solder paste from
tubes so controlling the solder use and scrap has improved.
Jason Gregory wrote:
> 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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