Industrial PCB Production: Etchant?

[BurnedResistor]

Dear All,

Having to write a science report, I was wondering what kind etchants are commonly used in PCB production. Does anyone have any insights?

Common hobby etchants I found where:

ammonium peroxydisulfate (NH4)2S2O8 a.k.a. ammonium persulfate
Ferric Chloride a.k.a. Iron (III) Chloride (FeCl3)
Sodium Persulfate Na2S2O8

Are these also used in industrial production?

Thank you!

[jpanhalt]

Chemcut -- a manufacturer of commercial etchers -- states that about half of the devices it sells are alkaline etch (ammonia + cupric chloride) and about half are cupric chloride.   I suspect what remains are ferric chloride or more esoteric etchants (http://www.chemcut.net/technical-info).   Depending on location, ferric chloride may be used more, but I have no data to support that.

[nctnico]

AFAIK cupric chloride is commonly used because it can be re-used indefinitely and the 'strength' can be kept constant.