We are having an issue with an entire lot of BME280 sensors that have been reflowed onto our design. During reflow we followed the exact recommended curve for the BME280. We have now noticed the RH to be wildly off from actual RH. About 13% to 15% off. We attempted to recondition the sensors using the reconditioning procedures in the datasheet. This did not work for us. It seemed to only improve the sensors by 2%.
I am curious how SparkFun goes about reconditioning their sensors. Do you do this process before or after you reflow them? Have you had a case where the reconditioning process doesn’t work at all?
Hi raf,
Interesting. When we recondition the BME280 on [our breakout we put them in a humidor for roughly 12-24 hours after reflow. Sometimes longer if needed. The relative humidity inside there is normally between 80-90% but I believe we do that since it is so dry here in Colorado. Once the membrane has been reconditioned, they’ll maintain that setting and our initial yields during manual testing are around 99-100% of the batch. That test is checking for a device ping as well as a reasonable output from the BME280. I would need to check our code for that test procedure to be certain of what that variable is set to.
I hope this helps your yields on your boards using the BME280.](https://www.sparkfun.com/products/13676)
Thanks for the response! So this past weekend I attempted another test. This time I got a mason jar and put a humidor packet that brings the humidity up to 84%. I left the sensor in there for 24 hours and for some reason it still did not work. I came across this article https://www.sparkfun.com/news/1090 that you guys wrote in 2013. It mentions that you guys created a box to better control the reconditioning processing. Are you performing this process at room temp or something greater? Is there a specific profile for that box? Do you perform reconditioning directly after reflow? Also what is the fallout like for you guys? Do you know how many boards fail the reconditioning process?
Thanks again.
Hi again raf,
We retired El Cubano a few years back but we still use the small container with humidity beads in it from the original humidor. We essentially have it in a big sealed plastic tub that sits at room temperature. I am not sure what specific RH-type beads we have in that little container, though. Looking at some of our batch details, we place them in there pretty much immediately after they come out of the reflow oven and then the batch will sit for roughly 12-24 hours. We have a very low failure rate with these breakouts. Usually, less than 1% fail our quality control test. That test initializes the sensor and takes a few readings to make sure it is reporting reasonable data for temperature, pressure, and humidity.