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HDC3022: PCB wash capability?

David F.
Prodigy 205 points
Part Number: HDC3022
Other Parts Discussed in Thread: HDC3021

Tool/software:

In the datasheet for HDC3022, it says in section 9.4.3.2:  "When soldering HDC3021 or HDC3022, both which have a protective cover which protects the sensor, these devices allow for PCB board wash."

In contrast to this statement, in this E2E forum, I have read a couple of responses recommending to not wash these parts.

We had the experience yesterday trying an ultrasonic bath to clean, and the filter membranes on the HDC3022 came loose on many of them.  But maybe the ultrasonic bath is too aggressive?  But a standard board wash process is acceptable?

In order to get the best substrate for applying a protective conformal coating, my desire is to solder the parts using an Organic Acid type flux (OR), and then immediately wash the boards in DI water.  Is this OK?

  • +1
    TI__Intellectual 2405 points

    Hi David,

    Board wash:

    We recommend do not expose the humidity sensor to ultrasonic vibrations, as this could damage the device and remove filter (as you have observed). The standard board wash process is better. 

    Humidity sensors are sensitive to contamination due to the exposed sensing element, such as from volatile organic compounds (VOCs) and solvents. The HDC3022’s IP67-rated PTFE filter protects the device from dust, debris, and condensation; however it is still susceptible to gaseous contamination such as VOCs. Generally board wash is not recommended as it contains contaminants that will affect the sensor; it is better to solder on the HDC as a last step with no-clean solder paste. However, the PTFE filter protects the sensor cavity from liquid entering, so if you do use board wash, it should be ok and you should follow up immediately by washing off all contaminants with DI water and air dry.

    Flux: 

    Generally we recommend no-clean solder paste/flux. Ensure that the flux does not have any volatile chemicals such as solvents or other inorganic compounds, which could contaminate the device. Please refer to the HDC302X Silicon Users Guide section 2.1 for additional information.

    Conformal Coating:

    Ensure the top of the humidity sensor is not covered with conformal coating. The humidity sensor functions by exposing the sensing element to the ambient air through a small hole on the top of the package (if you remove the white filter, you will see it). This hole must be exposed to the ambient air in order for the sensor to function. A suggestion would be to cover the top of the sensor with polyimide tape during the conformal coating step to protect it, and remove the tape after this step. 

    Best regards,

    Sakeenah Khan