not enough inorganic/electro chemists monitoring technet. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Eddie Rocha
Sent: Tuesday, March 21, 2006 3:57 PM
To: [log in to unmask]
Subject: Re: [TN] chromates on copper surface (Cr6)?

Was this a tough question? I didn't receive but one response. Thanks
Rudy.




Eddie:

Not clear I can "explain" something which is likely incorrect.
If your vendors start with Cr +6, the likelihood of there being zero
Cr+6 on the foil is near zero... certainly some of the Cr +6 reacts with
Copper metal Cu0 to form Cr+3 and
Cu+2, but all of it?  Hah... dream on.

However, before you go off and begin screaming, I suspect strongly that
some producers of foil may well be switching from Cr+6 to zero Cr
coating...  I cannot fathom why organics could not do as good a job...

And if there are foil producers who need some technology to assist this
change, contact me... :-)

Rudy Sedlak
RD Chemical Company

Eddie Rocha <[log in to unmask]> wrote: I understand that copper foils
are protected with chromates
(Cr6) prior to producing laminate. Since this is an RoHS banned
substance I need to understand why all my laminate suppliers have
certified their material to be RoHS compliant.

One supplier responded by stating that Cr6 is reduced to a state of Cr3
or Cr0 which is not a restricted substance.

Can somebody explain how it goes from a state of Cr6 to one of the
reduced states and why sometimes Cr3 versus Cr0?


Thank you,
Eddie Rocha

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