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Which type of SMD capacitors are more robust against PCB flexion cracking?

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asdf44

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I understand the metal or “J-lead” are better.
 
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treez

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Thanks, and i believe it would be correct to say that the bigger the case size, the more susceptible a general ceramic capacitor is toward cracking from PCB flexion?

I also wonder if the radial ceramic capacitors are even more resistant to board flexion cracking than either metal terminal SMD caps or flexiterm SMD caps?

Eg the RCER72A105K2 1uF , 100V x7r capacitor…..
https://www.mouser.co.uk/ProductDet...=sGAEpiMZZMt3KoXD5rJ2N7XzgPK/VHmNLa4kmANyQa0=

I am totally paranoid about SMD ceramic capacitors and their flexion cracking after working at an electric drives company who had an A4 size power board, strewn with SMD ceramic capacitors…and these were test boards, handled around from engineer to engineer to tech to tech…and they regularly blew up due ultimately to the cracks in the SMD ceramics..
 

asdf44

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Yes I'd expect those are basically immune to board flex cracking.

Personally I try to stay 1206 and below and make sure 1206 and above are flexiterm/automotive/J-lead (you can't avoid bigger packages for voltage spacing). I haven't witnessed any cracking issues in smaller packages.


Also I'd look to film when possible. When you take DC bias losses into consideration the size benefits of ceramic start to erode (they typically lose more than 50% of their C by 50% of their voltage rating).

TDK has the best search tool for caps (letting you filter on DC bias for example) and gives actual curves for individual part numbers.
https://product.tdk.com/en/search/capacitor/ceramic/mlcc/characteristic/
 
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schmitt trigger

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Flexiterm caps tend to fail safe.

Meaning that instead of cracking and causing a short circuit, the end caps will detach and become open circuit.

As Asdf44 mentioned, J-leads are the best, as the leads have mechanical compliance.
 
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