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April 2008

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Subject:
From:
Gabriela Bogdan <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Gabriela Bogdan <[log in to unmask]>
Date:
Tue, 29 Apr 2008 18:44:13 +0300
Content-Type:
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text/plain (55 lines)
Folks, I reply only to say that I always followed John's instructions 
concerning the cause of MLCC cracks, and his articles are one of my holy 
books.
Everybody can read , understand and improve the so wide spread occurrence of 
mechanical cracks if he checks his articles in the AVX technical papers.
Just looking at the position of the capacitor near the connector, you can 
see that being the only one which cracks has to do with mechanical stress.
When, how, where, is the challenging investigation everybody has to do on 
his own, as there are no identical circuits, processes and strains.
But again, placing the ceramic capacitor near a connector pin means trouble, 
and it comes AFTER reflow soldering.
These days, there are lots of articles on this matter written by specialists 
from many companies which manufacture MLCC's and research institutes, all in 
accordance with his older articles but the best I found is:
www.calce.umd.edu/whats_new/2001/design.pdf
And don't forget that not all MLCC's are able to withstand the same bending 
forces- their data sheets contain this parameter.
Thank you John for being there and giving your knowledge so freely!
Gaby

----- Original Message ----- 
From: "Brian Chandler" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, April 29, 2008 3:02 PM
Subject: Re: [TN] Cracking Ceramic Cap


Have you tried to take any strain measurements during the processing
downstream of SMT? ICT fixtures can induce excessive strain as well as any
other fixturing/pallets.

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