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, > > > -------------------------------------------------------------------------- > ------- > Technet Mail List provided as a free service by IPC using > LISTSERV 1.8d > To unsubscribe, send a message to [log in to unmask] with > following text in > the BODY (NOT the subject field): SIGNOFF Technet > To temporarily halt delivery of Technet send the following > message: SET Technet NOMAIL > Search previous postings at: www.ipc.org > <http://www.ipc.org/> > On-Line Resources & Databases > E-mail Archives > Please visit IPC web site ( > <http://www.ipc.org/html/forum.htm>) for additional > information, or contact Keach Sasamori at [log in to unmask] or > 847-509-9700 ext.5315 > > -------------------------------------------------------------------------- > ------- > --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------