Accelerometer circuit LIS2DE12 & Ultrasonic welding.

RLund.2 · ‎2020-10-27

We are developing a new product with the LIS2DE12 and are planning to use Ultrasonic welding during assembly of the ABS plastic enclosure. The welding machine will hammer on the enclosure with a frequency of 20KHz, with an amplitude of 20umeter and a 'big' pressure. The welding process will typically take 1-3 seconds. Will this be harmful for the sensor wich is mounted on a PCB inside the enclosure?

Eleon BORLINI · ‎2020-10-27

HI @RLund.2 ,

although this technique is not directly specified in the official soldering guidelines for ST sensors, and it is not the standard welding techniques used for MEMS devices, there should not be issues for soldering LIS2DE12 through ultrasonic welding, if the applied force is not to strong and since 20kHz is far above in frequency than the mechanical resonance of the MEMS accelerometer, so that frequencies are naturally dumped.

These accelerometers sustain 10.000g pulses in reliability so they should be safe also undergoing a 'big' pressure. In more details, the absolute maximum ratings are described in the datasheet p.14:

-Eleon

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Eleon BORLINI · ‎2020-10-27

HI @RLund.2 ,

although this technique is not directly specified in the official soldering guidelines for ST sensors, and it is not the standard welding techniques used for MEMS devices, there should not be issues for soldering LIS2DE12 through ultrasonic welding, if the applied force is not to strong and since 20kHz is far above in frequency than the mechanical resonance of the MEMS accelerometer, so that frequencies are naturally dumped.

These accelerometers sustain 10.000g pulses in reliability so they should be safe also undergoing a 'big' pressure. In more details, the absolute maximum ratings are described in the datasheet p.14:

-Eleon