- Devices in WCSP BGA package on
a Flexible PCB: WCSP parts on flexible PCB exhibit the fastest settling
times. However, due to high thermal resistance to the object surface, any
temperature leakage to the air can cause significant temperature offset. To
counteract this, protection technologies such as thermal isolating foam are
highly recommended. This foam should not increase the sensor's thermal mass.
Designers should also address the challenge of contact between the flexible PCB
and the measured surface. This design is not recommended for noisy temperature
environments as temperature fluctuations will easily affect the sensor readings.
For detailed precautions to minimize self-heating, see the Precise Temperature
Measurements With the TMP116 and TMP117, application
note.
- Devices in QFN package, with
thermal pad (TP) soldered: QFN packaged parts with soldered thermal pads
demonstrate the lowest temperature resistance and highest thermal mass. However,
this design cannot be widely recommended because soldering the QFN package
thermal pad can create additional stress on the silicon die, potentially leading
to a temperature offset of up to ±100m°C. System calibration is highly
recommended if the design requires the soldering of the QFN package's thermal
pad. For more details, refer to the Precise Temperature Measurements
With the TMP116 and TMP117, application note.
- Devices in QFN package, with
NO thermal pad soldered (nTPS): QFN parts on rigid PCB with non-soldered
thermal pads are the most common application case. By varying PCB thickness,
users can adjust the effective thermal mass, which can act as a temperature
fluctuation filter and reduce the need for data averaging inside the sensor.
Using thermal isolating foam to reduce leakage to the surrounding air is also
highly recommended, if possible.
By understanding these conclusions,
designers can make informed decisions to optimize thermal response and measurement
accuracy in various applications.