I made a design, which included an SMD RGB LED. I happened to choose the item C2843784 found on LCSC catalogs. My intention was to order the PCB with all SMT part mounted and for some reason that was the only component I found that JLCPCB accepted. I was in hurry, so I didn't dig deeper after alternative parts. The problem was that _the datasheet, the schematics and the footprint didn't match each other!_
This is how the footprint looked like:
The red arrow and the ellipse are added later to point out the error when I chatted with the customer support at JLCPCB. As you can see, the left schematics show that pin 1, 2 and 3 are cathodes. The right footprint shows _plus signs_ at pins 1, 2 and 3. _But_ the footprint shows the dot and the triangle mark at pin 1. All SMD RGB LEDs I have worked with have the triangle mark at the cathode side. So it was only natural to assume the error was with the plus and minus signs in the right footprint. Because _there was an error somewhere!_ Furthermore the datasheet of the item C2843784 shows that the triangle mark is at the cathode side!
My error was to rely on the customer support at JLCPCB. They said I should follow the datasheet, which showed this image:
So I went and ordered my PCBs, fifteen identical PCBs, each having three of these leds. And when I got them, they were wrong! _The triangle really points out the anode, not the cathode!_
It is my believe that the manufacturer has made an error placing the triangle mark at the anode side. The error is not that big, _if all datasheets, schematics and footprint thoroughly followed that!_ But now the people, who made the datasheets didn't notice the unconventional (but probably not erraneous) marking and they messed up everything. And I have 15 useless PCBs.
After I pointed out the error to JLCPCB (which further reported it to LCSC), the footprint has been corrected, but the datasheet still is wrong ([check it yourself](https://lcsc.com/product-detail/Light-Emitting-Diodes-LED_XINGLIGHT-XL-5050RGBC-MS_C2843784.html)), at least at the time of writing this. I even got a thank letter from LCSC for pointing out the erraneous schematics/footprint combo, but at that point I had already ordered my PCBs with wrongly placed leds. And to me, their correction still looked wrong because the plus signs were still at the triangle mark side (which turned out to be the right way!)
Lesson learned: Don't trust anything, as long as the datasheet, the schematics and the footprints and all pin numbering don't match each other in the component catalogs of LCSC or JLCPCB! Have them correct the info on all places before you rely your PCB design on the info. Don't trust advice from the customer chat.
They _do_ a good job! The chat at JLCPCB responds quickly and they got LCSC to correct the footprint rather quickly. But in my case, due to production schedules, it wasn't quick enough.