In a message dated 98-12-07 09:05:22 EST, you write:

<< Do you think that the anodize or Iridite coatings would either remove or
coat
 the Silicon found in the Aluminum casting alloy?  We think that this may
cause
 a problem in bonding.
  >>
The Anodize or "Iridite" (which is a tradename for a chromate conversion
coating) will not coat the Silicon in Aluminum casting alloy, and, further,
the preparation for anodize, or chromate conversion coating usually
(selectively) removes some aluminum from the surface, and leaves a "smut" of
silicon residue, which can seriously foul up bonding.  There are methods to
clean up high silicon Aluminum alloy, and remove the Silicon "smut", but you
want to do this before the Aluminum is part of the PCB.

Good rule of thumb in this situation, the more different materials that you
introduce into a chemical bath, ESPECIALLY IF THEY ARE ELECTRICALLY CONNECTED
TO EACH OTHER, the more problems in processing you face.

Specifics on prep of Aluminum casting alloys are available directly, off
Technet.

Rudy Sedlak
RD Chemical Company

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