Emily,
Just following Rudy`s advice and with my own experience of 15 years fighting
with alkaline etchers:you have to assure,that all operating conditions are
constant,as:
1) the same replenisher.you have to set tight spec for your supplier and ask
for COA .
2) check,if you are not loosing ammonia in your storage or supply tank
3) set once air suction system and be sure,that this is the same one.You
have to assure,that air is closed while etcher is not operating and minimise
time when spray pumps are working without copper to be etched
4) check sensitivity of your specific gravity controller and response time
of the system
Personally,I found the in line pH meter more as source of headaches than
real measuring device.The required accuracy of pH meter is 0.1 and when we
reached the point of calibrating 4 times a day,we just took the in-line pH
meter away.
Good luck
Edward
Edward Szpruch
Eltek , Manager of Process Engineering
P.O.Box 159 ; 49101 Petah Tikva Israel
Tel ++972 3 9395050 , Fax ++972 3 9309581
e-mail [log in to unmask]
> -----Original Message-----
> From: <Rudy Sedlak> [SMTP:[log in to unmask]]
> Sent: ב מרץ 12 2001 6:21
> To: [log in to unmask]
> Subject: Re: [TN] Quality of Etching
>
> Emily:
>
> I get in on this discussion a bit late, and consequently do not know if
> you
> are discussing Cupric Chloride, or Ammoniacal etching.
>
> Either way though, the normal way that etching is controlled is to
> establish
> a set of chemical parameters that give you good etching, and maintaining
> those parameters. When you do this, you can be assured that the etching
> will
> remain the quality that you measured.
>
> However, this is much easier to do with Cupric Chloride that with
> Ammoniacal,
> because you literally can control all the variables in Cupric Chloride,
> with
> existing control equipment. Further you have much better control of the
> ingredients going in to your sump.
>
> One of the things that I have found disturbing (and my knowledge of this
> is
> only in the US, you are located in Taiwan, I recall?) is that the
> replenisher
> for ammonical etchant used to vary significantly, and although it always
> met
> the manufacturers specification, the manufacturers specs were so large
> that
> virtually anything from pure water, to pure ammonia would have met the
> manufacturers specs.
>
> Further, at this time, it is not possible, I believe, to monitor and
> control
> all the variables in Ammoniacal etching. You can control water/copper
> through Baume'. And of course you can measure and control pH, but the
> other
> key issue is the Cuprous/Air content, and this, to my knowledge is never
> measured. Some of the people at Atotech have done some research on
> measuring
> the ORP (Oxidation Reduction Potential), just like is done with Cupric
> Chloride etchant, which is a monitor of the Cuprous/Air levels, and have
> reported good success (verbally), but I do not believe this is
> commercially
> available.
>
> One way to deal with the Cuprous/Air issue is simply to use WAY too much
> air,
> which has the downside of evaporating the ammonia out of the system, but
> you
> compensate for that with a pH monitor/control, and inject anhydrous
> ammonia.
>
> You can see more about etching at our website www.pcBfab.com
>
> Hope this helps.
>
> Rudy Sedlak
> RD Chemical Company
>
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