Other Parts Discussed in Thread: LMT70
One temperature probe in a batch of 40 is consistently measuring lower temperatures than all the others.
The probes consist a flex PCB that is 4mm wide where the LMT70A is mounted, but the width increases to 10mm at the other end for a connector. Total length is 150mm. The boards have a 10um paralin overcoating.
I used one probe as a "reference" and dipped each probe tip in turn into an oil bath together with the "reference" probe to get an idea of the spread of temperature differences. Typically, measurements were within 0.2 degC of each other at 100 degC which sit nicely within the LMT70A spec. However, one probe consistently measures lower than the others:
At 100 degC, error = -0.64 degC
Around room temperatures the error is within +/-0.1 degC, so there is at least a gain error.
What could cause the accuracy variation to beyond the spec?
The contract manufacturer did not like mounting the small BGA package to the skinny flex board. Could something in the reflow temperature profile (eg. a local hot spot) cause a parametric change?
Could ESD cause a change?
Any help would be appreciated since we anticipate many more batches in the future.