Power rating of size 1206 SMD resistors

[treez]

Hello
These two 1206 resistors are of exactly the same construction, but one is said to be capable of 500mW dissipation, and the other , just 250mW dissipation…what is the reason?

250mW rated 1206 resistor….
https://uk.farnell.com/bourns/crl1206-fu-r020elf/res-thick-film-0r02-1-0-25w-1206/dp/2328117RL


500mW rated 1206 resistor…
https://uk.farnell.com/yageo-phycomp/rl1206fr-7w0r022l/res-thick-film-0r022-1-0-5w-1206/dp/8067546

 

[KlausST]

Hi,

the 500mW is named "high power" in the datasheet. And it has 1200ppm/°C

The other is 250mW and has 600ppm/°C

--> different types. Rely on the datasheet.
Info: Check pad sizes for heat spreading.

Klaus

 

[schmitt trigger]

There are higher temperature resistive inks.

However, there are tradeoffs like temperature stability.

Klaus recommendation to watch out for localized hot spots is very true. I've seen poorly designed PSUs which have these localized hot spots. You can see the PWB substrate turning brown. Can't be good news for long term reliability.

 

[treez]

thanks, the pad sizes are the same.
The PPM difference doesnt seem to warrant one being touted as 500mw and the other being touted as 250mw.