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June 2010

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From:
Bev Christian <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Bev Christian <[log in to unmask]>
Date:
Fri, 11 Jun 2010 12:31:25 -0400
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But we did anyways and the SEM pictures help a lot in showing the cause of the defect.
Bev

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of vladimir Igoshev
Sent: Friday, June 11, 2010 12:28 PM
To: [log in to unmask]
Subject: Re: [TN] Weird formation of voids

Hi Stewart,

Thank you for mentioning my name :-), but I didn't think of SEM. The defects were to gross to use such a delicate instrument :-)
Vladimir

SENTEC Testing Laboratory Inc.
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca

-----Original Message-----
From: Stewart McCracken <[log in to unmask]>
Date:         Fri, 11 Jun 2010 15:35:51 
To: <[log in to unmask]>
Subject: Re: [TN] Weird formation of voids

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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