Yep, Andrew knew that. I didn't.
A little "Friday story".
I have never personally prepared a cross-section in my 20 years, 5 months and 6(?) days in the industry. The closest this fumbled fingered got is breaking one cross-sectioning blade at Nortel in 1990 when blades "only" cost $200. I was going to learn anyways, but then my boss laid off all my lab staff. He wanted me to do the cross-sectioning, but I was ticked off that he laid off the staff. My boss at the time was a bean counting supply guy, not a teckie. I went to HR and asked if I was even allowed to do cross-sectioning, something I had never done. We were a CAW plant (Canadian equivalent of the UAW - United Autoworkers Union for those outside of North America). HR said no, that was "a union job". Yes! Just what I wanted to hear. So then my boss had me ask the main Toronto site what it would cost for them to provide the services we could no longer supply internally. They came back with a figure close to half a million.
Things were at an impasse. I went on vacation and then one day a neighbor lady came to the door and said she was collecting for another neighbor - "person X" - my boss. ??? I asked, "What do you mean?!" And she told me that he had rolled his tractor, and it crushed his head and killed him. Within a week I had a new boss - an engineer this time (I am a scientist, so at least a "cousin".) and within a month I had my crackerjack cross-sectioner back, who had bumped someone else in the plant out of their job because of his 20+ years of seniority and multiple abilities on his ticket. Within two years I had the other person back who had been put out the door.
And before Dewey says anything, I had nothing to do with the tractor accident - not a good idea to put a small angle between your tractor and a wagon totally loaded with hay on a steep field!
Have a great weekend everyone.
Bev
RIM
________________________________
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Friday, June 11, 2010 12:03 PM
To: TechNet E-Mail Forum; Bev Christian
Cc: [log in to unmask]
Subject: Re: [TN] Weird formation of voids
Hi Bev - one other telltale sign in the cross-section is the "comet tails" swirling off the void pockets which is part of the issue that Stewart detailed.
Dave
Bev Christian <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
06/11/2010 10:40 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
Bev Christian <[log in to unmask]>
To
[log in to unmask]
cc
Subject
Re: [TN] Weird formation of voids
Stewart,
I lieu of a Dave Hillman Friday quiz, consider this it. And you WIN! Using an SEM and then carefully examining those pictures and the shape and placement of the "voids" we were able to determine that it is exactly as you describe. We are now in the process of hitting our grinding paper supplier "up the side of the head" for a crappy lot of product.
Bev
RIM
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stewart McCracken
Sent: Friday, June 11, 2010 11:36 AM
To: [log in to unmask]
Subject: Re: [TN] Weird formation of voids
Importance: High
Hi All,
Looks as though sample preparation condition is less than ideal. Sample is a little rounded and it appears that the voids might in fact be embedded debris from the polishing equipment(?) I'm sure Vladimir would agree - get it in the SEM to be sure! Need some better imaging and if possible EDS - these will go a very long way to confirming what's going on. Lumps of silicon carbide can really make a mess of a x-section. If you don't have access to a SEM, you could etch the structure and look for abnormal /unusual structures surrounding these features. Etching would also help to refine the soft edges on a x-section (provide a more natural edge) and let you see if you have shrinkage or gas voids (look at shape) filled with grinding debris.
Contaminated mats on a polishing station could explain the pattern of occurrence and the feature. As always though, more info about condition would make diagnosis easier!
Kind regards,
Stewart
Stewart McCracken
MCS Ltd.
Centre House
Midlothian Innovation Centre
Roslin
Midlothian
EH25 9RE
m. +44(0)7711 541735
t. +44(0)131 440 9090
f. +44(0)131 440 9085
e. [log in to unmask]
w. www.themcsgroup.co.uk
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of stephen gregory
Sent: 11 June 2010 16:21
To: [log in to unmask]
Subject: Re: [TN] Weird formation of voids
Hi Bev!
Got your picture today, and have it posted now:
http://stevezeva.homestead.com/Bevs_Ball.jpg
Almost looks like little pieces of dross. I wonder if something is going on with the solder paste? Or leaded reflow profile with a lead-free BGA?
Steve
--- On Wed, 6/9/10, Bev Christian <[log in to unmask]> wrote:
From: Bev Christian <[log in to unmask]>
Subject: [TN] Weird formation of voids
To: [log in to unmask]
Date: Wednesday, June 9, 2010, 9:51 AM
TechNetters,
I am sending a picture to Steve to post. I have labs in three locations. One of them has seen weird voids in cross-sections of BGAs while the other two locations have not. For the lab that has seen them, the cross-sections were prepared by different people on different days for different products, using the same equipment. The voids are not in all balls cross-sectioned but may be only in one of two of the balls in a row of multiple solder joints examined.
Have you seen anything like this? Do you know the root cause?
Vlad,
You know what is going on, so please don't respond.
Bev
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