Hi, I am using ST LIH3DH ( ST accelerometer) We use Ultrasonic Welding process to enclose the PCB in plastics. Can ultrasonic welding damage the LIH3DH ?? Thanks

[OWigd.1]

..

[niccolò]

Hi @OWigd.1​ ,

I don't know the detailed characteristics of ultrasonic welding, but here is my thought.

The sensor can be damaged due to temperature or to vibrations.

I don't think that the sensor can be subjected directly to temperatures so high that can damage it (that is higher than 125°C). The maximum operating range is shown in table 9 on page 15 of the LIS3DH datasheet ( https://www.st.com/resource/en/datasheet/cd00274221.pdf )

Regarding the vibrations, the acceleration involved should be less than 10000g for 0.2 ms or 3000 for 0.5 ms, to avoid damaging the component.

In the end it depends on the characteristics of your welding process.

Let me know if this helps you.

Niccolò

[OWigd.1]

Hi Noccolo

Thanks for your answer.

Ultrasonic welding parameter :

Frequency : 20KHz

Displacement : 40um ( 40 microns)

Time ; ~ 0.1 sec

We are still checking , but I suspect that the ultrasonic welding we use to close the PCB between 2 plastics harms the Accelerometer.

Have you an experience , or similar cases ??

Thanks

[niccolò]

Hi @OWigd.1​ ,

I never used ultrasonic welding on any component I used, so I'm not able to report any experience.

with the data you gave me, and assuming a harmonic motion, I'd say that max acceleration is = ( (2*pi*frequency)^2 ) * displacement that is roughly 630000[m/s^2] or 64000 g.

this value is over the constraints for not damaging the component, but I don't know if these calculations are right.

You should ask the producer of the welder for more info, or you can try to solder just one piece and try to run the sensor self test to see if it was damaged.

Niccolò

[OWigd.1]

Thanks Niccolo,

Yes , G values seem higher then Absolute Max ratings...

I will use your advise:

1. Passed the info to Welder vendor
2. Will run a Self Test ( what would be the pass/Fail criteria ? out of the below range Delta ?

Thanks again

Oded

[OWigd.1]

Below range means Page 11 in the Spec ( Vst)