Is it likely that surface mount resistors will burn out at 82C? 5

[davidd31415]

Is it likely that surface mount resistors would burn out at 82C (180F) when they are not powered? I do not have a datasheet for these; a general idea of what temperature different resistors typically burn out at would be helpful.

Thanks,

David

 

[geekEE]

I really doubt it. Most common chip resistors have storage temperatures of at least 85C. And storage specs of 125C are very common.

 

[Comcokid]

The surface mount resistors I am familiar with should have no problem with a 82C non-operating (storage temperature).

Of course, a resistor operated in a ambient temperature of 82 C would have to be de-rated for it's power dissipation. The chart I have for this shows derating to about 85% of normal at this temperature. The chart I have in front of me (Venkel) shows at 150C the resistor has to be derated to about 25% of normal. If these resistors operate to these temperatures, the should be able to be stored (non-operating) at these temperatures.

 

[itsmoked]

How could they burn out at 82C if they are soldered at 250C?

Look at a data sheet you will get a feel for the subject.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[MacGyverS2000]

Sustained heat versus short time periods are different animals...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[BrianG]

You say they are burnt out, by which I assume you mean they measure open circuit? Have you checked for the possibility of hairline fractures in the surface mount resistor itself or its solder joints to the circuit board? Bad assembly procedures or subsequent bad handling of the board after soldering could produce an open circuit by one or other of these causes.

 

[davidd31415]

Thanks for the feedback everyone. I am not able to do much with these boards myself and am trying to understand if someone else has a reasonable concern.

The conformal coating on the circuit boards has been changed and he is concerned about the resistors burning out at high temperature- he only wants to expose the boards to the high temperature though, not power them at high temperature.

The exposure time is 7 days and I don't imagine the coating will change the temperature the board reaches. Perhaps it will get there a bit faster... Any thoughts?

 

[itsmoked]

What temperature?????????????????????????????

And conformal coating surface mount parts will change their power dissipation ability during powered use, of course.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com