Jan,

I am trying to figure out what actually you are trying to say. 
Are you referring to solderability issue, that solder is not able to wick up
through the PTH & the via-hole, or the  PTH and via-holes on the solder side
are fully covered.
Maybe you can elaborate further. And what sort of contaminant in your
solder-pot?

If you have 0.005% Al or 0.003%Zn. tt will be useless even your setting is
less than 0.15 setting.
I was once experienced with the solder pot (in SEHO system), having Zinc 
and Aluminium.
It had caused solderability issue and lot of dross being formed in the pot. 
We have to drain the whole solder-pot, and replaced with new one.

Sometimes, if we faced with some components with solderability prooblem,
we apply some flux around the component's lead. It helped  the solder to flow
up better.

If you need further exchange of information, I am very glad to, since there is 
someone using SEHO machine too.


Poh Kong Hui
Nera Electronics 
Email: [log in to unmask]


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At 01:31 PM 7/1/96 +0200, you wrote:
>Hi!
>
>We're using a SEHO nitrogen wave soldering machine and are experience a
>problem with solderability on boards and components.
>Now we are testing a new mix of flux. We're mixing 50% of a no clean
>flux (Interflux IF2005M) and 50% destillated water and an additional 2%
>adipic acid. The theory of this is that the alcohol won't evaporate as
>fast as it does and the flux have more time over the preheater to
>"crawl" into the plated holes. The solderability increased and the
>joints was less crystalized. But the problem was the contamination. It
>also increased from a factor of 0,10 to 0,70. Our standards are below
>0,15.
>Has anyone tried anything similar or have any theory why the board
>contamination increased that much? 
>We have a theory that it wasn't the acids fault but the board. The
>original flux also have a 2% solidcontent. 
>
>/Jan Merstrand 
> e-mail: [log in to unmask]
>         [log in to unmask]
>
> fax: +46 33 179669
> 
>
>