Re: Cracking Capacitors

I am very interested in cracking in ceramic capacitors - particularly 
in switched mode power supplies (SMPS) - there is a need for large 
area capacitors which are now appearing in leaded formats - the 
leaded format would appear to be about 3 times the cost of leadless 
versions - hence the question - what is the maximum size of leadless 
ceramic capacitor which can be used with various circuit board 
materials which will not result in stress cracking during the 
lifetime of the product. This can be up to 10 years. This aspect of 
the problem is not concerned with cracking due to assembly processes 
- the concern is to do with long term stress cracking due to TCE 
mismatch between the ceramic capacitor and the substrtae material - 
this could be ceramic, FR4 or aluminium-core such as Berquist. I have 
failed to find any information on this aspect of the problem. 

Any assistance would be apriacted. Cian O Mathuna.
________________________________________________________________________________________________
Dr. Sean Cian O Mathuna                                             
Applications Director/Centre Manager                                                                             
Power Electronics Ireland,                                                                                                 
National Microelectronics Research Centre,
University College, Cork,
Ireland.

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