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TMP117: Sensor overmoulding

Dmitry Iakovlev
Prodigy 25 points
Part Number: TMP117

Hello,

We are developing a body temperature sensor and planning to use TMP117M for it. The sensor itself is soldered to a flexi PCB, but we want to protect it from tear and wear. One option I've seen here in the SNIA021A application note is to insert the sensor board into a hollow close-ended metal probe and pot with thermal adhesive, but it might me a bit uncomfortable to wear and also adds thermal mass.

Can TMP117 be overmoulded with plastic or other mould compounds once installed on a flexi PCB? Does the overmoulding process create any internal stresses that would make TMP117 less accurate?  

Best regards,

Dmitry

  • 0
    TI__Mastermind 43725 points
    Dmitry,

    Yes, you raise genuine concerns. There is always a chance for mold compound to cause shifts in semiconductor devices, but for many devices the change is negligible. In a high accuracy temperature sensor, there is evidence that these stresses cause a noticeable temperature error in the millicelsius range. Generally it appears as an offset, but with any change comes a degradation in tolerance/specification. For this reason, TI would not be able to guarantee accuracy after undergoing a customer's mold process, and customer would need to be accountable for verifying accuracy in their process.

    Thanks,
    Ren
  • 0
    TI__Prodigy 355 points

    Hello Dmitry. 

    The common recommendation would be to use mold, which not creates mechanical stress to the package. So compound which remain semi-soft should be the best candidate.

    Regards, Michael