My experience with cracked caps is that they are virtually impossible to 
see by visual inspection. If the cracks occur at, or under the termination 
than they will not be seen and it takes a trained eye to see a faint 
hairline crack. We have access to SEM and x-ray and these can not also 
easily find this kind of defect.

The most reliable method we have has been to send boards to Sonoscan for 
an ultrasound C-SAM test. This test has always been able to detect cracked 
caps for us.

Temperature cycling could detect, but not all cracked caps will cause a 
failure depending on application and if connected in parallel with others 
in the circuit.

Manually changing this many parts requires very careful control. It is too 
easy to miss one, or leave an unsoldered end.



Roger Mack  P.Eng. 
Manufacturing Specialist
Parker Hannifin Canada
Electronic Controls Division
1305 Clarence Avenue
Winnipeg, MB  R3T 1T4 Canada 
direct 204 453 3339 x373
[log in to unmask]
www.parker.com/ecd







From:
"Rivera, Raye" <[log in to unmask]>
To:
<[log in to unmask]>
Date:
04-08-2011 10:04
Subject:
[TN] Cracked ceramic capacitors
Sent by:
TechNet <[log in to unmask]>



Hello Technetters,

We had an issue with cracked SMT ceramic capacitors causing boards to fail 
functional test. We isolated the problem to a reel of parts that contained 
some cracked caps and purged these. Problem solved.

My question is about what to do with boards built with these capacitors 
before we purged. The boards pass functional test. The concern is that a 
cracked cap was loaded, but has not yet failed. The range of actions 
proposed here are:

- Temperature cycle the boards between -5 C and 55 C a few times. The 
theory is that this will flush out any latent defects.

- Visually inspect for defects.

- Manually change out all the suspect caps, about 50 per board.

Does anyone have thoughts on what would be the best method or another 
idea? We don't have ICT capability.

Thanks!

Raye Rivera



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