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Subject:
From:
Steven Creswick <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steven Creswick <[log in to unmask]>
Date:
Sat, 13 Nov 2010 13:18:35 -0500
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text/plain
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text/plain (211 lines)
Mumtaz,

Looks like a Au/Sn seal.  Either reflow or roller welder seal technique.
Certainly if reflow oven seal [>280°C], you have thoroughly stress relieved
the wires.  In either case, you likely have a good pre-seal bake/vac bake
taking multi-hours

I will tip-toe around your question by saying that if one were to do a
Weibull plot of all the wires in the package, you will find two different
populations - the short, 'down-bond' wires, and the long wires.  

Which set is stronger, really depends on the bond parameters and tool....

Normally, I will find the short ones to have the greatest pull strength, but
... it all depends.

Would be nice if you could use a package having a much smaller cavity size,
but I understand the economics of using what you have.


Steve Creswick
http://www.linkedin.com/in/stevencreswick




-----Original Message-----
From: Mumtaz Bora [mailto:[log in to unmask]] 
Sent: Saturday, November 13, 2010 11:51 AM
To: TechNet E-Mail Forum; Steven Creswick
Subject: RE: [TN] Wire Bond Pull failures

Hi Wayne, Yes, This is forward bonding .

I will look into the time/temp.exposures post seal.

The wire bonding configuration is uploaded. Should the long corner bonds
be expected to have low pull as #60 and #21.

Thank-you for your feedback. Much appreciated.


Mumtaz Bora

Senior Packaging Engineer

Peregrine Semiconductor

9380 Carroll Park Drive

San Diego, CA 92121

858-795-0112-direct

858-731-9499 -fax

[log in to unmask]

 


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: Saturday, November 13, 2010 5:33 AM
To: [log in to unmask]
Subject: Re: [TN] Wire Bond Pull failures

Mumtaz,

You have gotten good responses thus far.

My assumption is, this is 'normal' forward bonding.  If 'reverse'
bonding, invert my comments on first/second - front/back radius.

We are zeroed in on the Al/Al bond.

I particularly echo Wayne's comments on looping and tail.  Aluminum
wedge bonding is particularly sensitive to details - definitely much
less forgiving than gold ball bonding, for example.  Absolutely!  Be
very careful when working on the loop formation.

I suggest that rather than looking at the remnants of the pulled bonds,
you first look at the intact bonds - paying particular attention to any
looping differences and especially to the region of the first bond heel.
In the program, look for differences in looping parameters, and if that
corresponds to pre and post wire pull differences.

You may find that your 'strongest' wires are the longest ones, etc.
Look for those telltale cracks in the first bond heel and develop a
'feel' for the impact of the crack magnitude on resultant pull strength
- and what your organization deems to be acceptable.  Note - Most times,
one can find what appear to be 'cracks' in ANY first bond heel, if one
cranks up the magnification enough...

I would also contemplate increasing the back radius of the tool subject
to what you can/can not do with respect to looping.

You indicate that the pulls are 'post seal'.  What time/temp regime have
they been subjected to?  Since a little bit of heat can facilitate a
large amount of stress relief, make sure your time/temp exposures are
consistent.


Steve Creswick
http://www.linkedin.com/in/stevencreswick







-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Mumtaz Bora
Sent: Friday, November 12, 2010 9:15 PM
To: [log in to unmask]
Subject: [TN] Wire Bond Pull failures

Hello TechNetters,
 
I have some wirebonds on a Hi -Rel package that pulled below 2.0 gm
minimum  per Mil -Std -883. I have taken some SEM images of failed and
good bonds. Customer has a concern with plane of fracture of the failed
bonds even though it is break at "neck" . . It is Aluminum wire/to
Aluminum bond pad wedge bonded ultrasonically and aluminum wire to gold
plated post also bonded ultrasonic. Wire pull is post seal. I have
uploaded the file of images on the TechNet groupsite .I will appreciate
some feedback from wirebonding experts on the forum.
 
 http://ipc-technet.groupsite.com/main/summary
<http://ipc-technet.groupsite.com/main/summary> 

Thank-you, Mumtaz

Mumtaz Bora

Senior Packaging Engineer

Peregrine Semiconductor

9380 Carroll Park Drive

San Diego, CA 92121

858-795-0112-direct

858-731-9499 -fax

[log in to unmask]

 

 

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