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Reply To: | TechNet E-Mail Forum. |
Date: | Sat, 5 Jun 1999 12:33:55 -0500 |
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Francis:
One additional comment in addition to those of Dennis Fritz: All acid copper baths, regardless of the
brightener system, require carbon treating for the reasons mentioned. Since you're new to plating I
thought that additional bit of information might be useful.
Don Vischulis
Dennis Fritz wrote:
> In a message dated 99-06-04 18:09:12 EDT, [log in to unmask] writes:
>
> << I do not know why the Macdermid
> 9241 acid copper plating bath needs carbon treatment after a certain
> amp-hrs. of plating? >>
>
> 1. The brightners and grain refiners in acid coppers are organic molecules.
> There is a continuous breakdown of these additives as electrical current
> passes through them - more than the drag out of copper plating solution can
> remove with today's pollution controls. So, the "Total Organic Carbon"
> builds in the plating bath. At some point, the organics start to interfer
> with the copper grain structure in the deposits. The tensile and elongation
> properties fall off and you will get corner cracks in solder shock. Carbon
> treatment removes (hopefully) all these organics, so that you can start over
> with a new brightner add, just like on original make-up.
>
> 2. The plating resist you are using and the cleaner solution at the start of
> the pattern plate line are both organics. These are other sources of
> organic molecules, besides the breakdown products from the plating bath
> brightner. They also are removed (hopefully) in carbon treatment.
>
> You can control an acid copper plating bath by running Hull cells to
> determine brightner effectiveness -or the effect of the organic impurites,
> run a total organic carbon frequently to see how much organic is building up,
> run some sort of chromatograph (ionic, liquid, etc) to see what compound is
> building up, and run frequent physical property samples of your copper plate.
>
> OR, you can use the guidelines we have established based on shop experience
> around the world, and carbon treat after a specified number of amp hours per
> gallon of plating bath solution to be safe. Unless you have access to a lot
> of analytical equipment, better use the amp hour recommendation.
>
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