A short note to tel you that in the past we run into such a problem were it
ended up that
the air hose for air agitation of the copper bath created mouse bites and
craters.

The problem was solved by noting in which tank the boards were passing and
we found out
the bath that created that problem, THANKS TO TECHNET USERS !

Best Regards
Roland


----------
> De : Paul A Galatis <[log in to unmask]>
> A : [log in to unmask]
> Objet : Re: [Fwd: Mousebites/divots]
> Date : mardi, 1. juillet 1997 19:24
> 
> Tony,
> 
> I agree that mousebites are caused by precipitation of air from a
> supersaturated bath, and that it is not a single aspect problem, both
> plating and dry film processes must be examined.  In addition to the
> items that others have contributed, there are three additional conditions
> that we have observed that may contribute to the problem:
> 
> 1.  Supersaturation of air in the plating solution can also come from
> temperature changes.  As the temperature goes up, the solubility of air
> in the bath goes down.  This is similar to the effect seen in a cold can
> of beer vs. a warm one, the CO2 is less soluble at the higher temperature
> resulting in higher pressure.
> 
> The bath becomes saturated with air at the temperature at which it is
> running, no problem at this point.  If the bath temperature rises, the
> solubility of the air decreases resulting in supersaturation and, if the
> conditions are right, mousebites.
> 
> Track your bath temperature through the day. If you have a variation of
> more than a couple of degrees, this may be a contributor.
> 
> 2.  A majority of the shops in which we have observed mousebites also
> have an "exaggerated resist foot" or residue problem out of dry film. 
> The foot is usually greater than 0.5 mil in length and has been observed
> to be up to 2 mils long.
> 
> The foot can be observed by turning off the plating current completely
> for about 30 sec. every 8-10 min. during the plating cycle.  A properly
> prepared x-section across narrow traces will show grain boundaries at the
> current interruptions revealing that the plating does not start up
> against the resist side-wall.  In extreme cases, a normal x-section
> across narrow traces (with the resist still on the sample) will show that
> the plating never reaches the side-wall.  Most epoxy mounting compounds
> will allow mounting of the x-section sample with minimal effects on the
> dry film.
> 
> This condition would indicate that an examination of the dry film process
> is appropriate.
> 
> 3.  Mousebites tend to show up mostly on one side of the panels.  We have
> found that panels that are not hanging vertically in the tank can
> exaggerated the problem.  Angled panels also contribute to poor
> distribution of the copper deposit.
> 
> Good luck, and if you require further discussions you can e-mail me
> directly.
> 
> Paul Galatis
> Electrochemicals
> 
>
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