Applying pressure to a thermistor - not a good idea?

[ledtester]

I salvaged a thermistor like the one shown below from a laptop battery pack.

When I tested it it appeared to be of the 10K NTC variety.

I wanted to use it to measure the temperature of a heatsink, so I applied some heat sink compound and pressed it against the heatsink with a paper binder. And then I started to get really weird resistance readings - like in the megaohm range.

So I figure that applying a lot of pressure to one of these thermistors is a bad idea. So perhaps I should just use silicon/heat sink compound to affix the thermistor?

[metrologist]

Captain Tape!

[Zero999]

Captain Tape!

I've never heard of it, don't you mean Kapton tape?

[T3sl4co1l]

Yeahhh... if you clamped down on the thermistor bead part, you probably cracked it, or the soldering, or the flex circuit.

Would've been fine if you clamped before or after the bead, so the force bears on the flex (which is pretty flat and stiff, in thickness) instead.

And yes, Kapton(R) (generic: polyimide) tape is good stuff, as long as the surface isn't greasy it will stick nicely.  So, apply white goop sparingly where the thermistor sits, tape it down and you're good to go.  If you want a permanent installation instead, use a loaded epoxy (loaded with some material to give better thermal conductivity, really -- any will do, JB Weld, etc., doesn't have to be insulating since the thermistor is already insulated), and maybe some strain relief nearby so the leads don't tear the flex (if applicable).

Tim

[metrologist]

Kapton®

now I feel obligated to give acknowlegement

http://www.dupont.com/content/dam/dupont/products-and-services/membranes-and-films/polyimde-films/documents/DEC-Kapton-Trademark-Guidelines.pdf

[ledtester]

Or if you want something that's a lot cheaper but looks the same...