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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