LPS27HHW Pick&Place and conformal coating

[tve]

I'm trying to use the LPS27HHW in a 1 gram wildlife tracking device (water resistance required) and am wondering (a) how pick&place is supposed to pick up the sensor, and (b) how I can apply automated spray conformal coating to the board. I would have expected an option where the sensors are shipped with a small cap or film to facilitate p&p and to protect the sensor and that gets removed after assembly is complete... I'm probably missing something?

[Federica Bossi]

Hi @tve ,

This solution is not suggested because we have never tested this case and we don't know the reaction with the gel.

We can provide the temperature profile used by our subcontract, here attached. That is compared with standard JEDEC profile:

 

Hope this helps.

 

[Andrew Neil]

Have you check out the supporting materials on the Product Page:

https://www.st.com/en/mems-and-sensors/lps27hhw.html#documentation

 

eg,

AN5606, LPS27HHW digital pressure sensor: guidelines for system integration

 

TN0018 Surface mounting guidelines for MEMS sensors in an LGA package

[tve]

Thanks for the pointers, Andrew, I had read them and they provide zero information about pick'n'place or about conformal coating. The mounting described in AN5606 is completely impractical for me (sub-1gram device). Upon re-reading I was reminded about the issue with direct light exposure of the sensor. It looks like ST devices are not a good fit for my application...

[Federica Bossi]

Hi @tve ,

We don't have any specific guideline of pick/place since customer can do it by normal process and I know most of customers are doing pick/place without any specific tool and way. This because the methodology to pick the device is dependent to manufacturing and the machines they normally use.

The same for the cap that normally is used to avoid contamination during soldering phase. For the large number of cap present on the market  is not possible to have clear guideline.

In any case we can work on formal document acquiring information from different customer that are using this type of device in their application.