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LM61: quick fix to LM61 output getting not stable

David Tian
Prodigy 90 points
Part Number: LM61

Hello Sir,

We have been using your temperature sensor, LM61, TO92 package for at least 5 years. And have been suffering not stable output, not for every board and failure rate is about 1%. our annual usage is about 4000+. the quick fix is to touch up the pins of it by hand soldering with temperature 320°C. for some case, we have to solder off and solder back on. Our PCBAs supplier also use hand soldering process with temperature set 380°C +/- 10°C.  the circuitry is quite simple as below. When the output get to be not stable, the temperature reported is 162°C, or -273°C or 0°C, which is not true actually. I had a check the datasheet and there is no special soldering notes.

 output goes to AD7739, a ADC with a 10nF decoupling capacitor, also LM61 is soldered with Pin length ranging from 4mm - 8mm, varying from different products.

  • I was thinking if we can turn up tip higher temperature, say 450°C. But I didn't do that as current quick fix is to touch-up at 320°C, lower than380C as PCBAs supplier does. also for 450°C, no risk to damage the temperature sensor?

    Thanks and regards,

    David