Hi Eddie! Just to add to Rudy's comments - any chromate conversion coating
that is Cr+6 based does convert to Cr+3 when damaged (e.g. the self healing
aspect) but there is always some of the Cr+6 species around. Any chromate
conversion coating that is Cr+6 based is not RoHS compliant. Your supplier
is incorrect unless he/she is supplying a Cr+3 or zero chromate conversion
coating as Rudy described. Qualifying a substitute conversion coating that
is "as good as or better than" a Cr+6 conversion coating is not an easy
task depending on your use environment conditions. Good Luck.

Dave



             Eddie Rocha
             <[log in to unmask]
             M>                                                         To
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                                                                   Subject
             03/21/2006 05:56          Re: [TN] chromates on copper
             PM                        surface (Cr6)?


             Please respond to
              TechNet E-Mail
                   Forum
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             ; Please respond
                    to
                Eddie Rocha
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                    M>






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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