Hello All,
We are using NXP’s MMA8653FC accelerometer sensor in a vibration sensing product (vehicular). We developed and tested, both in the lab and in the field, over 40 prototypes without issue in the past 18 months. Following pilot production we have experienced a failure rate of around 9%, some 450 assemblies during the self-test procedure. After investigation we discovered that the device in the failed assemblies are sending the same value for Z-axis, 0x80 or 0x79 (we are using 8 bit in our application).
Further research within the forum identifies the problem of ‘stiction’ (see attachment) however, this was apparently addressed and rectified in this part number 2013. Our production stock is from week 42, 2017. The devices were stored for 14 months prior to mounting in late April, 2019. The re-flow process shows no abnormalities. We are in the process of lodging the necessary paperwork for NXP to investigate but, as this will take some time, I’d like to ask if anyone else has any experience or feedback regarding the same?
Thanks in advance.
Mike
Hi Mike,
First, please make sure the soldering process is done according to these recommendations.
Peak Package Body Temperature(PPT): 260 ℃
Maximum Time at Peak Temperature: 40 s
For detailed information about how to handle the accelerometer during manufacturing process and solder profile, please recommend the customer to check the App Note AN1902: https://www.nxp.com/docs/en/application-note/AN1902.pdf
As you properly mentioned, there was a known issue with stiction of Z-axis of the NXP accelerometers MMA845x and MMA865x families, but this issue was corrected in 2013, so, I recommend you to check the marking of the accelerometers and make sure they are recently manufactured devices.
For parts that used to have this stiction issue, there was a “recovery” method, or a way to make sure the problem is caused by a mechanical issue of the internal MEMs structure, this is done by slight tap on the part. Remember that the problem was that the MEMS structure inside the accelerometer gets stuck, so the workaround was to tap it/hit it with your finger on top of the accelerometer to un-stuck it.
There seems to be no new reports of this issue for the MMA865x family in our technical support system tool.
In case you find that these are recent manufactured devices and are soldered according to the NXP recommendations, then a CQC failure analysis with the NXP Quality engineers would be recommended. You would need to contact your distributor to start a CQC (failure analysis) process.
Have a great day,
Jose
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