Electronic – Is ceramic capacitor suitable for snubber

Please specify load characteristics and application. Very desirably provide a circuit diagram or at least a good word picture.

The snubber's role is to dissipate transient energy which is looking for a home at switch-off time. We need to know how much energy there is, and how it is "stored" to know what sort of home it needs. As a guide you want an energy sink that will stop reactive voltage rising dangerously high, that will dissipate available reactive energy prior to the next switching cycle and which has minimal possible effect the rest of the time. Not magic, just compromise.

Note that as your chosen optocoupler is "random phase switchable, you will have greater need of a snubber than if you were zero crossing switching - subject to the usual warnings re effects of inductive load currents not being zero at zero voltage.

• Datasheet BT139 TRIAC

• Datasheet MOC3051M / MOC3052M optoisolated Triac driver

To "start you on your way" ...

• ST AN437 - RC snubber circuit design for TRIAC

• Fairchild AN3008 - RC Snubber Networks for Thyristor Power Control and Transient Suppression

• Related Fairchild AN3004 - Applications of Zero Voltage Crossing Optically Isolated Triac Driver

• ONSemi AN1048/D - RC Snubber networks For Thyristor Power Control and Transient Suppression

While ESR is not always given it is often easy to find on a better manufacturers website. Many have online or downloadable tools that will show you all of the information you could ever want about a cap. With the rise of the need to simulate PDN for everyday boards, people have been demanding exactly this kind of information.

For example take a look at Murata's simsurfing tool

It's free of course and all you do is select a capacitor from the list and among other things you can see the graph of ESR and impedance vs frequency. If you're simulating it's easy to extract a simple RLC model from the data.