NeoPixels Fail after PCB assembly

[kjav]

Hello. We're using WS2812B NeoPixel lights in the upcoming Ringo robot (plumgeek.com). When assembling prototypes, we've had some reliability problems. We are aware of moisture sensitivity requirements and we have been baking the parts at 130C for 10+ hours before touching them with a solder iron or reflowing them. We've been getting the loose pixels thus far direct from Adafruit. Often a color does not work in a pixel or it doesn't relay data to the subsequent pixel. We'll replace the bad pixels with new ones and eventually assemble a working string on the bot but we're sure we're doing something wrong here.

Can you all share any suggestions when it comes to successfully assembling these pixels onto boards? Even after baking them, when touching a lead with an iron, it can be seen under a microscope that it looks like something is de-laminating down by the die (sometimes anyway). We've been assembling our own boards via our own SMT line for a long time and we've never had other products fail due to moisture and I'm wondering if these WS2812B pixels are just super sensitive?

Also, any chance you could private message and share your source for reels of the WS2812B parts? I've found a source direct from China but it would be super helpful if I were able to go straight to a trusted source.

Thanks so much, and thank you again for writing the time critical code to drive these lights. You guys are awesome!
-Kevin

[adafruit2]

hiya, yep these are VERY temperature sensitive - good temp control at the reflow is essential, keep it as low as possible. You can buy WS281x's direct from worldsemi - just contact them :)

[kjav]

Thanks for the response. Glad to confirm what we were seeing.

Could you share more about your existing reflow profile? The overall profile would be helpful, but if not, do you know what peak temperature you're using and for how long? Also if possible, what paste are you using?

We plan to use a lead-free paste with a 245C peak temperature.

I couldn't find any temperature profile guidance in the datasheet for the pixels.

Thanks so much for the help!!
-Kevin