the Al bond pads provided by the semiconductor industry are not pure Al,
they are alloys with others metals, mostly Cu, just to avoid the
problem you have..
I do agree with Morten¨'s proposal with the Gold layer..,  I think you
will have a layer of alumina as
soon as you place your chips in the ambient air...

Jordi


On Tue, Jan 27, 2009 at 7:08 AM, shay kaplan  wrote:
> Jon
>
> The whole semiconductor industry was using gold wire bond on 1u AL pads for
> decades so you should be able to do it.
>
> The wafers are usually shipped to offshore sites for bonding where they go
> grind and other processes that will not leave the AL fresh.
>
> Try to ask a capillary or a bonder manufacturer for tips, I'm sure they will
> tell you the settings (I haven't done this for 20 years and my memory....)
>
> Shay
>