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Gaby,

You need to get SEM/EDS data. My offer is still on the table, as it's really interesting :-)

Regards,

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


-----Original Message-----
From: Gabriela <[log in to unmask]>

Date:         Mon, 6 Jul 2009 19:59:01 
To: <[log in to unmask]>
Subject: Re: [TN] Weird solder joints


I am really impressed about you people, being ready to help so much.
Thank you all from all my heart.
No, these specific feature is not due to handling. 
I think that the continuation was due to outgassing from the "open" in the
solder into the mold.
Also, the feature stayed there through all the polishing steps.
Seems to me that this is a first for many of us.
Forgot to tell you: This specific ball failed during ELECTRICAL test.
The exact location-row and ball was given to me.
Two other balls had similar features, but not through all the width. I don't
know if they passed the electrical test.
Gaby


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stewart McCracken
Sent: Monday, July 06, 2009 5:28 PM
To: [log in to unmask]
Subject: Re: [TN] Weird solder joints

Hi Gaby,

Just a thought, are you 100% certain that the features which you have
shown are not caused by scoring/scratching/handling on the surface of
the section? Could be some contact on the delicate sample surface
between final polish and observation, perhaps during etch or rinse
steps, or even during mounting onto a slide for viewing (dirt of the
sample press)? This could explain the continuation of a feature from the
solder joint into surrounding mould resin or soldermask. 

Would be worth ruling out and again SEM inspection of the sample would
clarify. Would also be happy to take a quick look at them in the SEM for
you if you don't have access. 

Kind regards,

Stewart

Stewart McCracken
MCS Ltd.

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 Gabriela
Sent: 04 July 2009 08:01
To: Administrator
Subject: [TN] Weird solder joints

Dear all,
By cross sectioning BGA solder joints on a failed assembly, I found that
the
suspected joints are not uniform and that they contain unusual
separation
areas.

I suspect mixed assembly and/or bad reflow profile.

Steve was so kind and enabled me to send the links.
Please may I have your opinion?
http://stevezeva.homestead.com/files/small.jpg

 

 <http://stevezeva.homestead.com/files/small1.jpg>
http://stevezeva.homestead.com/files/small1.jpg

 

 <http://stevezeva.homestead.com/files/small2.jpg>
http://stevezeva.homestead.com/files/small2.jpg

http://stevezeva.homestead.com/files/small3.jpg

 <http://stevezeva.homestead.com/files/small4.jpg>
http://stevezeva.homestead.com/files/small4.jpg

 


Gaby


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