> Guys,
>       Any advise on this subject.  The Aluminium Pad size is approximately
> 500um X 500um and the leads are protected by the Passivation Layer.  I
> experience Corrosion problem only on the Bond Pads.  Bond Pads are opened
> using RIE etch process.
> Thanks,
>
> Sanjay Thekdi
> 375 Los Coches Street,
> Milpitas, CA 95035

This might be your problem:
If aluminum is plasma etched, a chlorine-based (Cl2, BCl3, etc.) chemistry
is used.
Some Cl is left on the surface after etching.
When exposed to water or water vapor in the air,
hydrochloric acid is formed that corrodes the aluminum.
The solution to this problem, found on commercial aluminum etchers,
is to add an addtional process chamber that runs a flourine-based plasma.
The F displaces the Cl on the surface and does not create a problem later.
   --Kirt Williams, Ph.D.  consultant