Josep,

You did not define two critial parameters - wire size, and how many you plan
to do!

I beg to differ with Bruce's response a bit.  

Fine wire aluminum wire on clean copper does work, although I much prefer
the nickel plating too!  

Fine wire aluminum (1.25 - 2 mil) IS challenging!  Normal Al wire doesn't
work very consistently - it is too soft.  One obtains too much bond
deformation before a 'real' bond is formed.  The trick is to use 'harder'
wire (lower elongation), but then the problem shifts to problems of damaging
the IC's bond pads.  If you are not very experienced at wire bonding, this
could be daunting!

Specificially, heavy aluminum (5-10 mil diameter) works REALLY WELL on
copper - its only 'fault' is that it must be operated in an non-nitrogen
(ie. non-hermetic) environment to retain good pull strengths.  

Conclusions: If you have a couple parts to do, you might struggle though as
suggested above.  If you have large numbers of parts to do, make it easier
on yourself (as Bruce suggests) and get them plated!  (But I suggest that
you test some sample plated parts before you plate up everything)

PS - In many respects, automatic wire bonding is still an 'art', although
science helps out at times.

And I can honestly say that the views expressed above are NOT those of my
employer.


Steven Creswick





At 01:41 PM 3/5/01 +0100, you wrote:
>I'm unable to make a wire ultrasonic bonding (wedge bond) with Al wire 
>directly to cupper pad.
>With your permission, I'd be interested to known if this bonding is possible
>
>Thanks in advanced
>
>
>Josep M. Badia
>Servei de Recursos Tècnics
>Tèlf/Fax: 977 559630/559605
>Univ. Rovira i Virgili
>
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