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October 2009

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Subject:
From:
Joyce Koo <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Joyce Koo <[log in to unmask]>
Date:
Thu, 29 Oct 2009 08:58:53 -0400
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Old mil spec got the requirement.  You need gold hardness match with your wire. 
--------------------------
Sent using BlackBerry


----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Thu Oct 29 08:12:53 2009
Subject: Re: [TN] Al wire bonding

Anat,

One can bond to the nickel [without the gold]!! This become especially easy
with heavier wire sizes [>2 mil].

Typically, one uses an ENIG plating.  The immersion gold results in a gold
flash of ~2-5µinches
The gold is merely there to protect the nickel from oxidizing too much.  One
actually bonds 'through' the gold layer to get to the underlying nickel.

If given a choice, I like pure soft gold instead of a hardened gold.  If you
use ENIG, you may not get much choice in your gold.

It is my opinion that the thermal history & chronology of the board has more
of an inpact on wire bond reliability than simple plating.  Eg - if one were
to reflow the board, [maybe] clean it, then let it set in que for multiple
weeks in a shop environment - I virtually guarantee you that you will note
differences in bonding characteristics as compared to a virgin board.

ENIG, or gold flash, is my answer.  Keep them moving - don't let them set
around, is my recommendation.

Steve Creswick





On Thu, Oct 29, 2009 at 3:38 AM, Anat Douek <[log in to unmask]> wrote:

>
>
> Hi,
> What is the min gold thickness required for reliable aluminum wire bonding
> ?
> Which gold type is prefered for this process?
> It is needed  for a military application.
>
> Regards,
> Anat Douek
> Process Engineer
> Herley General Microwave Israel
> tel. 972-25689455
>
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