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December 2001

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Subject:
From:
Edward Szpruch <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 6 Dec 2001 08:24:33 +0200
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I am using peroxide regeneration for a long time,but I made a lot of trials
with Sodium Perchlorate.
At the end I found peroxide easier to operate,mainly due to influence of
changes in composition of the oxidisers.
Rudy is right: peroxide regeneration produces no by-product,perchlorate does
produce sodium chloride,which affect etching rate.
Chemistry control is based on independent control of 3 factors:
oxidiser by ORP
HCl by conductivity
Copper ballance by specific gravity ( addition of water from acid rinse)
If the are some variations in concentration of incoming perchlorate,this
will result fluctuations in sodium chloride concentration and copper
concentration ( specific gravity can not differentiate between them).With
peroxide I can switch from 50% to 35% and I do not need to change setup of
control/dosing equipment.
Of course someone can switch to different controll system ( photometric
controll of copper+1  instead of ORP) and this allow to run the chemistry on
very low acid concentration.
Each system,does no matter which one, depends on control system: very good
mixing,properly sized dosing system and measuring system located in the way
, that allow  fast respond to chemical changes.
But running any of system based on 1 control parameter ( e.g. specific
gravity ) and operate 3 dosing pumps on pre-set ratios - this is a mess.
The last: here,in Israel, peroxide is easy available.Sodium Perchlorate is
rather rare and expensive.
Edward

Edward Szpruch
Eltek Ltd
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: Gary McCauley [SMTP:[log in to unmask]]
> Sent: ה דצמבר 06 2001 2:05
> To:   [log in to unmask]
> Subject:      Re: [TN] Hydrogen Peroxide vs. Sodium Chlorate
> 
> Any of the systems, if overdosed, can and will release chlorine gas.
> I know, I have done it with two of the types.
> 
> [Gary McCauley] 
>  
>  ----Original Message-----
> From: Sean Clinton [mailto:[log in to unmask]]
> Sent: Wednesday, December 05, 2001 5:55 PM
> To: [log in to unmask]
> Subject: Re: [TN] Hydrogen Peroxide vs. Sodium Chlorate
> 
> 
> 
>       Greg,
> 	
>       The other down side to the peroxide approach, aside from the
> consumption volume difference and stability of the peroxide itself, is
> that if you overdose the system with peroxide, large amounts of chlorine
> gas will be evolved...a dangerous proposition.  
> 	
>       The balanced reaction is:
>       H2O2 + 2HCL + Cu --> CuCl2 + 2H2O
> 	
>       Excess peroxide will react with free HCl acid to create water and
> free chlorine gas: (1:2 mole ratio)
>       (H2O2 + 2HCl --> 2H2O +Cl2)
> 	
>       So an excess peroxide reaction is:
>       2H2O2 + 4HCl + Cu --> CuCl2 + 4H2O + Cl2  
> 	
>       Sorry about the font layout...I can't do subscripts in Eudora.
> 	
> 	
>       At 02:05 PM 12/5/01 -0600, you wrote:
> 	
> 
>               Hey Greg, long time no talk to. The most common oversight in
> comparing
>               peroxide and chlorate is understanding consumption and
> by-products
>               generated from the reaction. The reaction using peroxide
> generates 1 mole
>               of water for 1 mole of cupric chloride regenerated, the
> reaction using
>               sodium chlorate generates 1 mole of water for 2 moles of
> cupric chloride,
>               half as much water. Also, 1 mole of peroxide consumes 1 mole
> of copper
>               whereas 1 mole of sodium chlorate consumes 3 moles of
> copper. The volume
>               consumption of 50%by weight Hydrogen Peroxide is 3 times
> that of CuOx, e.g.
>               if a process consumes 100 gallons of peroxide per day, when
> switching to
>               chlorate they will only use app. 33 gallons of chlorate in
> the same
>               conditions. Given the other dilution and stabilization
> issues with peroxide
>               it is common for the consumption difference to be closer to
> 4 times that of
>               sodium chlorate.
>       	
>               Salt is a by-product generated in the chlorate reaction,
> which my of us add
>               over the side to increase etch rate.
>       	
>               Alot of water is generated in the peroxide reaction, which
> somtimes makes
>               it difficult to maintain Cu loading. Hope this helps,
>       	
> 	
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