Are surface mount Y2 capacitors less robust than thru-hole ones?

[ocset]

Hello,
The following VJ2220 series Y capacitors are surface mount and ceramic.

SMD  (ceramic) Y capacitors
http://www.vishay.com/docs/45020/vjsafetycapsx7r.pdf

Are they  less robust to overvoltages and thermal expansion stress than  Y2 capacitors  which are radial and film based?

The Radial Film based Y capacitors don’t state a “peak impulse voltage”…

Radial (Film) Y capacitors
http://www.mouser.com/ds/2/136/Y2_B81122-31746.pdf

[floobydust]

Yes.

[Kleinstein]

Class Y caps need to be pretty robust - this is what makes them meet the class Y requirements.

Due to board stress is might be more demanding to meet this requirements in SMD form.
The SMD form might need special care when soldering and for the layout to avoid extra stress - so they be more difficult to use. Having the note on peak voltage is likely not a significant difference.

[ocset]

This link…
http://www.kemet.com/Lists/Filestore/EvoxRifaRFIandSMD.pdf
….states how films heal after high voltage stress’s, but ceramics don’t, but then it stops short of saying that their Y ceramic SMD  capacitors are therefore less robust than their thru-hole Film Y capacitors….it just leaves you in the air, wondering

[chris_leyson]

The answer is yes, surface mount Y caps are less robust than leaded components. I work in consumer electronics and we're talking about tens of thousands of PCBs. Anything over 50V rated is leaded, no arguement. Y caps are usually film in parallel with leaded disc ceramic, snubber caps are also leaded disc ceramic. There is a good reason for doing things this way, reliabillity.

Whilst on the subject of mlcc caps, I recently I used some mlcc caps for bulk storage on the auxilliary power for a flyback and it's just come back and bitten my arse. The capacitance under bias is not 20uF it's a lot less. If there is a short on the secondary side the flyback controller goes into hickup mode and the hickup timing is determined by the value of the aux supply smoothing cap.

If you've only got a few uF of capacitance then the supply hickups at 20Hz with 60% duty cycle and you got some seriously stressed devices. If the controller doesn't go into thermal shutdown then the flyback transformer runs at 75C above ambient continously !! Change the mlcc caps for a 22uF electrolytic and harmony is restored, hickup rate is a few Hz and the duty cycle is maybe 10%, Lesson learnt, it came back and bit my arse.

[ocset]

thanks, you are very conscientious...many would say stuff the customer if they short the output, then they get what they deserve.