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We etch inner layers using Cupric Chloride Etchant. We control the chemistry with
ORP and Conductivity probes. The ORP adds Sodium Chlorate and the Conductivity controls HCl adds.

We have experienced gas generation (chlorine or HCl fumes) when both the ORP and Conductivity
are in control. The gas/fume release occurs when the copper gets as high as 33 - 35 ounces per gallon.

Standard procedure is to feed copper into the system when a chemical out of balance situation results in gas
generation. Clearly in this case this would be the wrong thing to do.

Can anyone explain the chemical reaction behind a release of gas/fumes
when the copper is high?

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Maybe in reply to: dhowell: "FAB:Cupric Chloride Etchant"
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I have two guesses Re: fuming with high copper levels.

Guess 1: ORP reading becomes less sensitive as copper levels get higher, requiring more Cu(I) to trip ORP
adder point. This may encourage a slow control response, allowing overdosing of oxidizer.

Guess 2: Conductivity controllers are set up on a narrow response to conductance in a very specific mixture where
the only significant variable is HCl. High Cu may add to the conductivity and cause acid to fail to add.
This will definitely throw the system out of balance, either causing overadd of oxidizer (liberating gas when
some HCl is added) or some other phenomenon.

I may be able to be more complete with more detailed operation info.

Marshall Gurian
Coates ASI
e-mail: HYPERLINK mailto:marshall.gurian@coatesasi.com marshall.gurian@coatesasi.com

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Maybe in reply to: dhowell: "FAB:Cupric Chloride Etchant"

Chlorine is a gas, which is marginally soluble in water. The more salts, all other things being equal,
such as pH, the less soluble the Chlorine. So, you could be creating Chlorine when the Copper is low,
and it is soluble enough to not be given off.

One key question is do you monitor your ORP, that is to say, actually keep a continuous record of it??
If you are getting serious spikes in an ORP chart, you are creating Chlorine, whether you smell it or not.

Another factor, that could be contributing is the viscosity, and thus mixing speed of the etchant. If the Copper
is low, the mixing speed of the components is higher, and this will allow the Cuprous ion to come into contact
with the Chlorine gas, and react with it, and make it go away, faster.

One of the factors that I have seen personally that can contribute seriously to this problem is the type (and horsepower) of the pump making the additions. If the pump is too powerful, and ANY centrifugal pump I have ever seen is too powerful, It will seriously over-add before the ORP sensor tells it to shut off. Best type of pump is a bellows pump, and they should be sized so that they are running a lot of the time that panels are going down the line. Never less than 20% of the time, and more is better, up to even as high as 70% of the time. This ensures slow addition, so that the reactants can circulate around enough to find the Cuprous ion, and not have time to say, "Hey, can't find no Cuprous, I'm history!", and escape to the atmosphere.

Also, speaking of mixing, if you are running more than one chamber, you should have some serious horsepower mixing the two sumps. This is best done by pumping from the last chamber to the first, and cascading back. I am going to make a rough estimate that you want one HP of pump circulating for every etcher sump in a line.

And that is an absolute minimum.

Also, if you have more than one etcher sump, you may want to add Chlorate and HCl at more than one point.

If you would like more free opinions, which some have said are worth almost what you pay for them, e-mail, or call.

Rudy Sedlak
RD Chemical Company
415-962-8004

Paul Gould (paul@BEMBRIDG.DEMON.CO.UK)
Tue, 21 Oct 1997 22:52:59 +0100

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There is a lot of information on this at http://www.pcbfab.com/ineretch.htm which, thanks to Rudy Sedlak, is extremely helpful.

I have recent experience of putting in this process and opted for Hydrogen Peroxide as the oxidiser. If I used sodium chlorate, the company which recovers the spent etchant could not plate out the copper so easily. Disposal costs are covered by the value of copper reclaimed.

It is very economical to run at around 150 gms/litre of copper take up. HCl is kept at 60-65 gms/litre, the Redox potential is set to keep the cuprous between 1 and 2 gms/litre (as long as there is some cuprous present, you won't evolve chlorine gas).

It is very clean and safe as long as you avoid mixing peroxide and hydrochloric acid so procedures to prevent this must be watertight.

We use redox potential to dose peroxide, conductivity to dose HCL, and SG to dose water. Etch rates are very consistent and undercut minimal.

Good luck.

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Hello, everyone

I am setting up a spray etching bath using merely CuCl2.2H2O and HCl.
My questions are
1. What are the concentrations for CuCl2.2H2O (???g/l or ???lb/gallon) and HCl (???ml/l or ???gallon/gallon)?

2. What's the reading of redox potential of a fresh bath at room temperature or at working temperature?

3. How fast is the etching rate using this kind of bath?

Any input will be highly appreciated suixin zhang
ELIS-TFCG/IMEC, University of Ghent
Sint-Pietersnieuwstraat 41, B-9000 Ghent, Belgium
tel: 0032-9-2643371
fax: 0032-9-2643594
Email: HYPERLINK mailto:suixin.zhang@elis.rug.ac.be suixin.zhang@elis.rug.ac.be

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Recommend that you see the website http://www.pcbfab.com

This site has a page labeled "Innerlayer Etching", which should answer many
of your questions. If you have further questions, please feel free to e-mail
me.

Rudy Sedlak
RD Chemical Company

Cupric Chloride Etchant

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One of our process engineers is contemplating changing the etcher chemistry. Potential changes
include NaCl or sodium chlorate in traditional cupric chloride etching chemistry. Before initiating
an evaluation of these changes, I would appreciate any responses to the following:

Can anyone share any experiences (positive or negative) with using sodium chloride in cupric chloride
etchant in order to increase etch rate? Are you currently using NaCl and if so, have you found any
degredation of equipment due to corrosion? Any other comments?

In the same vein, are there any Cupric etchers out there using sodium chlorate as the oxidant as opposed
to hydrogen peroxide? Again, any positive/negative impacts?

Thanks to any and all comments and responses.

Dave Rooke
Circo Craft - Pointe Claire

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Maybe in reply to: D. Rooke: "Cupric Chloride Etchant"
Next in thread: Phil Culpovich: "Re: Cupric Chloride Etchant"

Hi Dave:

The short answer to your questions about using Sodium Chloride and/or Sodium Chlorate in Cupric Chloride
is "it depends". I have some understanding of the subject based on a study of the chemistry of the reaction,
argueably one of the smartest guys around on the subject is Don Ball, of Atotech, State College, PA. Don has
actually done significant amount of experimental work on the subject, and perhaps part of why I think he is so
smart is that the conclusions he arrived at by experimental work agree with my conclusions based on theoretical
considerations only.

The long and short of it is summed up in some papers that Don has written, and copies are available from him,
if you have enough clout, i.e., are a customer potential.

Part of the answer though depends on the method of control that you are using. If you use the ideal combination
of ORP, Baume', and acidity by conductivity, then Hydrogen Peroxide and HCl are as good as it gets. ANYTIME you
use Sodium salts to replenish, you will be forming Sodium Chloride as by-product, and this will to some extent
lower the maximum Baume' that you can run the etcher, and potentially slow your etch rate.

Many years ago, one of the colorimetric controllers REQUIRED the use of Sodium Chloride, and this, along with the use
of Sodium Chlorate was promoted as being safer, as it was less prone to Chlorine gas release. It became quite popular
for that reason, as well as the fact that it was consistent in its etch speed. Unfortunately, it was also SLOW, and
actually resulted in Cupric Chloride actually getting a worse rap than deserved in terms of etch rate.

All around, from what I am seeing in the industry, I would recommend staying away from Sodium Chloride completely, and if you are successful in using Hydrogen Peroxide, stay with it, changing to Sodium Chlorate will not help, and may hurt.

The key issue to optimizing Cupric Chloride etchant is to get good control of all the variables, and stick to Don Ball's
recommended parameters.

Rudy Sedlak
RD Chemical Company

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The purpose of the NaCl is to provide not just an increased etch rate but to provide a uniform etch speed which should typically be approximately 1oz copper removed per board per minute under spray. The NaCl is used as both a catalyst and a buffer. If properly controlled using a Vis-U-Etch colorimetric contoller, your etcher components will last for years and years. The reason for the degradation of etcher components such as titanium conveyor axles is due to too much free HCl present or in other words, out of balance cupric chloride. When an ORP type controller is used, it looks at Oxidation Reduction Potential, Specific Gravity and Normality of Acid. The problem with this type of control is that the ORP numbers can be relied on but the Specific Gravity changes and the Normality is not on a linear scale so it can not be relied on either. With two changing variables out of three all you really wind up doing is baby sitting the ORP controller. Since MOST people have frequent, daily problems with ORP controllers (ie. frequent release of Chlorine gas indicating an out of balance etchant), this is not a reliable way to control cupric chloride. The ONLY constant with cupric chloride that can be counted on is the color of the etchant which is only correct when it is a clear emerald green. For those that like the numbers game, the Vis-U-Etch controller typically maintains an ORP reading within 20mv at around 580mv to 600mv. Provided you mix your Chlorate/Chloride oxidizer solution properly and consistently, your copper content will be approximately 27oz/gallon(US). The Specific Gravity will be in the range of 38-40 degrees Baume but hold steady at one point in that range. The Normality will typically stay around .8N. Since this method of control is not dependant on an exact input of copper, you don't have to run scrap through or change the calibration every time you change your production habits. Once a controller is calibrated, it should accurately introduce Acid/Oxidizer regardless of how fast or slow copper is added.

The cost of using Hydrogen Peroxide is approximately double that of Chlorate. Also, Peroxide is not very stable and therefore hard to keep "fresh". The Chlorate/Chloride mix does not go stale as easily though mixing more than a one week supply is not recommended.

If you would like complete information on the Vis-U-Etch system, we can be reached at:

Phil Culpovich
Oxford V.U.E., Inc.
PO Box 4221
Sunland, CA 91041-4221
USA

tel. 818-353-4714
fax. 818-353-1024
http://www.oxfordvue.com
e-mail: HYPERLINK mailto:pculpovich@oxfordvue.com pculpovich@oxfordvue.com

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Dave, We use Sodium Chlorate & HCL to regenerate cupric. We have used this for years with both Oxford VUE
and ORP/Conductivity controls to make additions. If you want more details call Ajay Singh at 408-243-1976 x7626.

Dan Howell
408-557-7082(direct line)
Zycon

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When I worked in a manufacturing facility, we used sodium chloride in our cupric etcher to increase etch rate.
We did experience faster wear on the equipment using this method. Nozzles in particular seemed to wear faster,
although we also had problems with pumps.

You can achieve an increase in etch rate by running at a higher than usual normality, without causing machine wear.
There is a trade-off here as well; normality higher than about 3.0 can attack photoresist. If you decide to run a
high normality, I'd recommend using a system of carbon filtration.

Mark Dowding
Regional Technical Specialist
Insulectro

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Maybe in reply to: D. Rooke: "Cupric Chloride Etchant"

Dave and all other PWB Fabricators using Chlorine gas,

What action is being taken in response to the requirements to reduce on site gas to 1,500 lbs by May 26 , 1997
[ OSHA 1910.190] and the total elimination of gas by 6/12/99 Clean air act[ CCA 112 -r]

Mike Covel
HMSC Tucson , Az.

HYPERLINK mailto:MCCovel@ccgate.hac.com MCCovel@ccgate.hac.com

Phil Culpovich (pculpovich@oxfordvue.com)
Tue, 21 Oct 1997 18:51:26 -0700

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Jack:

I definately agree with Marty Grove from Chemcut that as far as safety is concerned, Sodium Chlorate/Sodium Chloride is the way to go. Chlorine gas is dangerous and so is peroxide. With chlorine gas, regulations being put forward are driving PWB shops away from it anyway. As to peroxide, I know of 2 shops that had fires/explosions directly attributable to their peroxide which was thought to be handled safely at the time. As to the chlorate/chloride mixture, the salt provides both buffer and catalyst delivering THE safest cupric regeneration available. Since everyone else is using this opportunity to promote specific products, I'll throw in my 2 cents. Use the Vis-U-Etch 5 that I demonstrated for you. You'll pay the least amount of all current chlorate systems, have local service representation and get a machine with the safety features you need. GFI, Input chemical flow detection, bubble detection for small leaks and answers to your questions 24 hours every day. Also, what you may not be aware of are the new glass light cells included in all new VUE 5's. The glass light cells monitor the etchant 1/4" at a time and with increased oxidizer concentration, can control the etchant easily over 30 ounces per gallon! Less spent generated, more efficient chemical usage and best of all, faster etch rate without sacrificing etch factor. At our current mixture, we are etching one ounce copper panels in 45 seconds! There is a definate resurgence in interest in Vis-U-Etch since the VUE 5 came out with all of its improvements. I'm sure that Charlie reported to you about his visit to Alphanetics in Santa Ana, CA with favorable results. If you need more references or have more questions for us, we'll be quite happy to satisfy your needs.

Phil Culpovich

Oxford V.U.E., Inc.
818-353-4714
HYPERLINK mailto:pculpovich@oxfordvue.com pculpovich@oxfordvue.com

Cupric Chloride Etchant
NCPPaul @aol.com (@aol.com")
Fri, 24 Oct 1997 07:29:10 -0400

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All the responses have included just chemical regen options, but ORP can be maintained with electricity. FSL manufactures an Electroletically Regenaration Unit that maintains ORP without adding in needless water (H2O2). The capitol investment is high but the ROI is quick, if all cost considered. With chemical regen system costs would include the chemistries, HCL and Chlorine/H2O2/or Sodium Chlorite. The amount of HCL used in any system will depend on the type of Oxidizer. The waste cost is a factor, in house treatment or off sight treatments. With the FSL unit the regen cells plate out almost pure copper that can be sold, with no waste treatment discharge. HCl is used to maintain Normality but at a much lower consumption rate than the chemical oxidizers. I have seen two diffirent insallation in the New England area that has been up and running. I do not represent FSL. I'm just giving other alternatives for Cupric Chloride Regen.

I am unsure of any down side to this system. If anyone has any input please feel free to comment.