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Subject:
From:
Rex Waygood <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Rex Waygood <[log in to unmask]>
Date:
Fri, 3 Dec 2010 11:53:01 +0000
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text/plain (92 lines)
Resistors tend to have a DeltaR/R specification and they define the
conditions under which the DeltaR/R characteristic is met.
For example http://www.vishay.com/docs/20035/dcrcwe3.pdf
Some specifications such as power dissipation include a DeltaR/R
requirement. It is often the DeltaR/R that determines the power
dissipation for a size of resistor for a given manufacturer.

If you actually want to fuse the resistor then I think that is probably
a minefield, and you are on your own................... :-)

Regards
Rex

Rex Waygood
Technical Manager
 
Hansatech EMS provides value manufacturing through engineering and
quality
 
Hansatech EMS Limited
Benson Road
Nuffield Industrial Estate
Poole
Dorset
BH17 0RY
 
+44 (0)1202 338200

 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Blair Hogg
Sent: 02 December 2010 20:39
To: [log in to unmask]
Subject: [TN] [Somewhat NTC] When does a resistor become a fuse?

This is a little off the normal Technet topic genre, but I was wondering
if anyone out there may have some data on how long a resistor can
withstand overcurrent before it changes resistance / fuses open? I'm
taling about a standard 0805 carbon film resistor, for example 100 ohms:

at 1 mA it drops 100 mV and dissipates 100 uW, no big deal for a 125 mW
device

at 10 mA it drops 1 V and dissipates 10 mW, still no big deal

at 100 mA it drops 10 V and dissipates 1 W, until the resistance
increases dramatically

How much of a time duration can the device withstand at 100 mA? Is there
a correlation between overload and time?

The graph in
http://www.koaspeer.com/pdfs/Thick_Film_Pulse_Limitation.pdf
seems to indicate that an 0805 (2A on the graph) can dissipate 1.5 W for
1 second. Does this make sense?

Thanks,

Blair

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