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January 1999

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From:
Bev Christian <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 6 Jan 1999 09:35:02 -0500
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Mak,
Ideally there is no water in conventional no-clean fluxes (ie 96-98%
alcohol), but by Karl Fischer titrations I have found that typically there
is 0.15% water in no-clean fluxes.  This should not be too surprising as
water and isopropyl alcohol are "cousins" and the old rule of "like
dissolves like" is alive and well.  This level will not hurt your process.
If you are using  a closed container spray fluxer then you should have few
problems due to water.  However, if you are using a drum spray fluxer or are
still stuck with a foam fluxer then it is another story, especially if your
plant is not air conditioned.  On a hot, humid North American summer day the
water content can continually rise and I have seen it get as high as 2% when
people did not look after their system.  You will have a whole pile of
trouble at this level.  1% is not very good either.  I am not prepared to
give you the definite cut-off between 0.15 and 1% where action is required.
Besides the obviously danger already alluded to in other e-mail replies
about flash evaporation of water at the wave, excess water can fool people
who are using specific gravity to monitor their flux  activity.  People
could end up adding more thinner because they thought they had a flux
concentration problem when it was a water uptake problem.

My first recommendation would be to change to a new spray fluxer.  Quality
will be as good or better than with older fluxers and you will save enough
in flux costs to pay for the spray fluxer in short order.  I would then
change over to a no-clean, VOC free flux for safety, insurance and
environmental reasons.  We went through a couple and then have found one we
love and have changed our whole plant over to it and now two other sites as
well to the same new flux.  Another few are using another popular one from
another major flux supplier.

One thing to keep in mind with the new VOC free fluxes is that not only do
you often need more preheat, but the air-flow patterns in your oven are
important to help remove the saturated air/nitrogen so evaporation can
continue.

Good luck,

Bev Christian
Nortel

> -----Original Message-----
> From: [log in to unmask] [SMTP:[log in to unmask]]
> Sent: Tuesday, January 05, 1999 12:11 PM
> To:   [log in to unmask]
> Subject:      [TN] Water contents in no clean flux
>
>      All,
>
>      Would like to know if fresh no clean flux should contain water. If
>      yes, what is the purpose and what is the appropriate level of the
>      water content?
>
>      Appreciate if any suggestons.
>
>      Mak
>
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