Can freezing/ice damage the BME680 pressure sensor?

[ThLOCP]

Dear Bosch Sensortec community,

Ou product embeds one BM680 with which we have carried out temperature and humidity test series in oven. Here are the test steps: (1) 70°C with 100%HR, then (2) a slow ramp-down from 70°C to -20°C with 100%HR. Off course, crossing the dew point, drops of water were formed. After this test the pressure sensor has not worked ever since. Both temperature and humidity measurement from the BME680 still work perfectly. 

We believe water has entered the small hole of the pressure sensor, turning into ice and potentially damaging the pressure sensor.

Questions:

- Does this analysis make sense?

- Is there a way to avoid this problem? Any workaround to protect the sensor without disrupting the measurement of the pressure sensor?

We thank you in advance for your help.

Best regards,

Thierry

[BSTRobin]

Hi ThLOCP,

Sorry for the delayed reply, we will internal check and give you feedback this week.

[BSTRobin]

Hi ThLOCP,

Please refer to our internal check,

1, Seems something wrong with the pressure sensor

• as the information from customer, register report 0xFF after the procedure
• 1/10pcs report this failure

2, Failure analysis

• The BME680 sensor passed the 80℃/85%rH test which followed JESD22 spec, so we think the sensor can be worked at most of the real environment
• Customer test at 100%rH environment, condensate water will be continuous on the sensor surface which over the dew point
• If the water drop continuous on the MEMS surface, will have influence/damage with the sensor

3, Solution/suggestion for customer

• Integrate with waterproof film which can protect the sensor
• perform the test at normal humidity environment

Dew Point Calculator: http://www.dpcalc.org

[ThLOCP]

Dear BSTRobin,

Thank you for your feedback and answer. Really appreciated on our side.

Last questions please about "Integrate with waterproof film which can protect the sensor":

- Intuitively we may think that a waterproof film could distort the pressure measure. Are we wrong in that feeling?

- Please, do you have any recommendations for waterproof films that will fit the BME680? Any references?

Thank you in advance for your anwser,

Best regards,

Thierry

[BSTRobin · Accepted solution]

Hi ThLOCP,

Waterproof film has been widely used in applications such as mobile phones and watches.
Normally, users can choose waterproof membranes based on their own performance requirements.