Electronic – SMD resistor maximum voltage: is 200V really a limiting factor


I need a resistor to work with 230 VAC voltage. So 400V rating would be appreciated.

However most of the chip resistor with size 1206 and above has only 200 Volts of maximum working voltage. Main of my concern is: why this voltage doesn't rise up with resistor size?

This table taken from Rohms datasheet:

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And the similar situation appears in different suppliers.

It looks very weird as 2512 is more than twice as long as 1206 but it has same voltage rating.

This is a bit frustrating… What shoud I use in a circuits working under power line voltages?

Best Answer

Generally speaking SMD resistors have lower voltage ratings than through hole .The older larger through hole resistors were used in valve circuits.Whats done these days is placing several SMD resistors in a series string to get the voltage rating.Because SMD parts are machine placed in production the extra component count is not seen as a penalty.Remember that the price of machine placing one part is a very small fraction of the cost of through hole hand placement .Some SMD resistors have laser cuts on them to get the right value .This can mean focused electric fields that reduce the voltage rating.Hence length is not going to always mean a high voltage rating.