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January 2004

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Subject:
From:
Rene Lopez <[log in to unmask]>
Reply To:
Rene Lopez <[log in to unmask]>
Date:
Fri, 16 Jan 2004 08:31:32 -0800
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Russ,

A few more things to note regarding algae treatment for rinse tanks,


Warm weather can often produce a surge in algae growth in DI water systems.
Systems professionals should be consulted as to the best methods to treat
and maintain the DI water system to prevent algae from growing and
contaminating wet process chemistries.  Maintenance involves the use of UV
lights and a post-light filter.  Treatment of a contaminated system is much
more involved.  Care must be used to prevent damage to resin beds and other
sensitive system components. A system treatment schedule should be adopted,
and frequently the recommendations are for annual treatment.  Rinse tanks
are often the site where algae is first discovered, often by observing a
pink stain on the sidewall of the tank that is slimy to the touch.


Rinse tanks should be routinely leached to prevent algae buildup.  The
frequency of treatment will depend on the water temperature, but given the
harmful effects that algae can produce, an aggressive frequency of once a
week or once every other week during peak summer months is recommended.  As
temperatures moderate, monthly or even quarterly treatments may prove to be
sufficient to prevent any buildup.  When algae is present in any tank, all
rinse tanks on that process should be treated as follows:

Add 2%bv bleach to the rinse tank.  Wipe the tank sides and bottom with a
scotch brite or clean rag attached to a pole to disrupt the algae attached
to the tank.  Allow the solution to remain for 30-60 minutes, dump, rinse
thoroughly and refill with clean water.



If algae is not present on the rinse tank walls, treatment with 2%bv HCl
instead on bleach will inhibit growth, and many shops find the HCl is easier
to waste treat than bleach.  If waste treatment of bleach is not an issue,
bleach should be used as it is more effective.  Regardless of the tank
treatment used, thorough rinsing of the treated rinse tanks with clean water
is required to prevent process contamination and quality issues.


When you do clean out your EC tank (with whatever microetch solution you
maybe using) you may also want to take the extra step at this point and also
strip the tank with a 10% nitric strip acid solution to remove any residual
palladium from the tank walls.  Ensure that the tank walls are thoroughly
rinsed following this procedure.


Take Care,



Rene Lopez

Tritek Circuit Products



----- Original Message -----
From: "Scott B. Westheimer" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, January 15, 2004 5:35 PM
Subject: Re: [TN] eless copper


> Russ,
>
> The excess foaming during and after plating is an indication that the bath
> is over activate and unstable. The foaming is caused by the plating
reaction
> and should subside once the parts are removed. If it continues then that
> means that the bath is continuing to plate and that plating is occurring
on
> the tank walls. If you are not filtering your bath than you will
introducing
> particulate material from board debris as well as from the environment,
that
> will react with the plating solution,  specially if the material is
> metallic.
>
> I would agree with Dennis and you should check the specific gravity and
> other components as well as send samples to your vendor. I would also
offer
> one further recommendation that might be a reach but it caused me
sleepless
> nights many years ago. I had a problem with very much the same thing  and
> after checking all of the normal chemical parameters we were stuck for an
> answer. We were able to scrap off some of the nodules and etched them in a
> watch glass and look at them under a microscope. When the copper etched
away
> we could see that there was something under the copper. We could not
figure
> out what it was and no analysis that we performed gave us any glue. We
went
> back to the line and look in to all of the tanks and we could see
something
> floating in all of them We could not figure out what it was and than we
saw
> something had changed. There was a water line coming from the etcher which
> was the discharge from the cooling coil. In an attempt to reduce water
> consumption the company had installed a line from the etcher to the PTh
line
> to recycle the cooling water and was using it in the rinse tanks on the
> electroless plating line. We cut a piece of the pipe and inside the pipe
it
> was half the diameter of what it should have been. It was filled with
algae.
> If the lines are stagnate for a period of time the algae grows like crazy.
> We then looked at the rinse tanks and all of the process tanks after the
> rinses and could see material floating in all of them but not in any of
the
> tanks before the introduction of the etcher's cooling water. This might be
a
> stretch but look in the tanks before EC and see if you can see any
material
> floating around. If you were closed during the holidays and this problem
> occurred during or after your start up it might be a cause. Check the
basics
> first, such as chemistry and filtration. And of course get your vendor
> involved.
>
> Regards
>
> Scott Westheimer
> Colonial Circuits
> ----- Original Message -----
> From: "Russell Burdick" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Thursday, January 15, 2004 3:39 PM
> Subject: [TN] eless copper
>
>
> > Hello everybody,
> >
> > Today's chemistry question concerns electroless copper plating.
> >
> > Problem is small nodules of copper deposited on the surface of the board
> and
> > in the holes at the electroless copper bath. Noticable differences in
bath
> > operation is more foaming during plating and more foam present after
> plating
> > is completed. Also, a noticable black/dark green particulate visible on
> the
> > foam surface and eventually on the tank wall and equipment.
> >
> > Have previously found and corrected excessive EDTA conc. ( indicating
> higher
> > than wanted proprietary bath chemicals ). Problem still exists but to a
> > lesser extent.
> >
> > Thanks for all help.
> >
> > Russ
> >
> > _________________________________________________________________
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