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October 2009

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Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Wed, 28 Oct 2009 09:06:16 -0500
Content-Type:
text/plain
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text/plain (109 lines)
No, they roll until they cool.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: Wednesday, October 28, 2009 9:03 AM
To: [log in to unmask]
Subject: Re: [TN] Birth of a Solderball

Bob,

Wouldn't mid-chip solder balls in SMT display slightly flat bottoms as well?

Leland

-----Original Message-----
From: Bob Willis [mailto:[log in to unmask]] 
Sent: Wednesday, October 28, 2009 8:54 AM
To: 'TechNet E-Mail Forum'; Leland Woodall
Subject: RE: [TN] Birth of a Solderball

You can only really tell from the shape.

Trying to microsection balls is fun, you get a great section then the ball
comes out during polishing. I use these images as how not to do sections in
my microsection class at college. Next time I am doing some sections I have
a board with some nice balls from selective that I have vacuum coated.

In selective and wave if the solder ball is still in a liquid state during
contact with the mask it can have a flat bottom. This is normal in air but
not nitrogen


Bob Willis
2 Fourth Ave, Chelmsford, Essex, CM1 4HA England
Tel: (44) 1245 351502
Fax: (44) 1245 496123
Mobile: 07860 775858
www.ASKbobwillis.com
www.SolderingStandards.com 
New Package on Package Workshops 24th November
www.ASKbobwillis.com/PoPWorkshops.pdf 
PCB Inspection & Quality Control Workshop 3rd November
www.ASKbobwillis.com/faworkshops.pdf
Book Bob's "Step by Step Failure Analysis
Workshop"4th November  www.ASKbobwillis.com/faworkshops.pdf
Package on Package Assembly & Inspection Workshops 21th January ITRI
www.ASKbobwillis.com/PoPWorkshops.pdf


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Leland Woodall
Sent: 28 October 2009 11:54
To: [log in to unmask]
Subject: [TN] Birth of a Solderball

TechNetters,

Is there any possible way to determine the origin of a solder ball?
We've had a failure because of one, and we're trying to determine
whether it came from our SMT or wave soldering process.

We use SAC305 at both, so using the SEM to determine alloy composition
is not really helping.

The ball itself is spherical with no "tails" and quite shiny in
appearance.

If we cross section the ball, will we see a difference in grain
structure due to the differences in cool down rates?  Is there anything
else we can use or do?

Thanks in advance for your help!

Leland

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