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January 2010

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Subject:
From:
Joe Fjelstad <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Wed, 6 Jan 2010 12:34:31 -0500
Content-Type:
text/plain
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text/plain (152 lines)
Hi Steve, 
 
Sounds a lot like TAB gang bonding. 
 
Are you sure you even need the nickel? (or is it required  elsewhere for 
some reason?) 
 
That the gold bumps are undisturbed is somewhat disturbing in its own  
right. 
 
One data point from the past. The original Tessera microBGAs leads  were 
gold over copper bonded to aluminum pads and they worked quite  reliably. They 
were point bonded however. 
 
Good luck sorting it all out... 
 
Best, 
Joe    
 
 
In a message dated 1/6/2010 5:52:02 A.M. Pacific Standard Time,  
[log in to unmask] writes:

Hi Steve  et al,
Unfortunately this is not as easy as it sounds. First the lower  pull
strengths are not necessarily a failure- they are just not as good.  This 
was
an experiment designed between ourselves and our customer. The  initial
problem is we have a .0032 wide flying lead ( about 150 of them)  with no
kapton support. A chip/die is "compression bonded" onto the lead -  from 
what
I can gather it is a combination of heat/pressure/ultrasonic and  some kind
of proprietary magic. The reason we went to the lower nickel is  because the
leads being so fragile they often crack during the process so  we tried the
lower nickel to alleviate this issue. With the lower nickel  pull is approx.
5-7 grams. With the higher nickel 9-11 grams. There is a  gold bump on the
die and when the failure happens the gold bump separates  from the lead with
no damage to the gold bump. At present this is as much  as I know. Thanks 
for
the input so far. Steve Kelly

-----Original  Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven  Creswick
Sent: January-05-10 6:14 PM
To: [log in to unmask]
Subject: Re:  [TN] Pull strength of thermosonic wire bondable gold

Steve,

If  you can send me the data sets in an Excel format, I can provide you  
with
some insight based on magnitude and grouping by Weibull plot.   

If there is a big mix of failure modes, this interpretation will be  pretty
generic.  

Its free input, however    :-)

Just send it direct.

Steve C

-----Original  Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve  Kelly
Sent: Tuesday, January 05, 2010 4:17 PM
To:  [log in to unmask]
Subject: [TN] Pull strength of thermosonic wire bondable  gold

Hi All,

I have a wire bond question to the wire bond gurus  who have helped me out a
lot in the past. Made 2 versions of a flex circuit  - only varied the nickel
thickness. Application is thermosonic gold wire  bonding.

Flex circuit lead is .0032 wide - version 1 - nickel is 150  microinches -
soft gold is 50 microinches- pull strength is X

Version 2 - nickel
is 40 microinches -  soft gold is 50 microinches - pull strength is approx.
½X  of version  1-

Is this what I should expect?



Regards Steve  Kelly



Steve Kelly (PLEASE NOTE NEW E-MAIL ADDRESS)

(416)  750-8433 (work)

(416) 750-0016 (fax)

(416) 577-8433  (cell)




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