Screw down the PCB of the FXLS8471Q

[johannes_steinb]

I am interested in using the FXLS8471Q accelerometer in an upcoming design. I read in the datasheet that it is suggested to fix the PCB without usage of screw down or stacking, to minimize the stress on the package.

What are other solutions to fix the PCB?

If we use screw down to fix the PCB and place the accelerometer next to it, which effect does it have to the package? 

Thanks for any help

Johannes

[johannes_steinb]

Hi Jose,

Thanks for your response.

In your response you recommend that we should use the correct torque, so the question is what is the correct torque ?

Johannes

[reyes]

Hi,

Regarding the max torque to be applied, unfortunately we do not have any information since this is more dependent on the resistance of the PCB before it bends of break. What I can give is general guidelines about the recommended distance according to DFM rules between the screw holes and the accelerometer (again this is generally speaking since this would also depends on the size of the screw), this distance should be around 110 mils (2.7mm).

I hope this helps.

[johannes_steinb]

Hi,

Thanks for your response, it helps a lot.

Is there a table in which I could look up the distances for the different screws?

Johannes 

[reyes · Accepted solution]

Hi,

this information depends on your PCB manufacturer, ask them directly for their DFM rules or ask them specifically for the recommended distance between the mechanial hole and a component.

Regards,

Jose

[johannes_steinb]

Hi,

Thank you for your response, it helps a lot.

Johannes

[reyes]

Hi Johannes,

The only reason of why it is recommended to avoid screwing down the PCB near the accelerometer to fix it into an enclosure is because this may cause the PCB to bend, causing stress to the soldering pads, but if you add the correct torque to the screws, there should not be any problem.

Customers are advised to be cautious about the proximity of screw-down holes to the sensor, and the location of any press fit to the assembled PCB when in an enclosure. It is important that the assembled PCB remain flat after assembly to keep electronic operation of the device optimal.

Have a great day,
Jose

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