Nowadays , there are more and more build in IC led chip coming out , those build in ic ,such as SK6812, SK6822,SK9822, WS2813, GS8208 LED Chip have same MLS Level :6. which you need to pay more attention on them than normal led chip .
Before you welding them , you must do dehumidification .you need to put them in oven for 24hours on 60-70degree temperature .
,after that , you must use them within 4 hours , or you need to put them in oven again .
why we need to do dehumidification ? because the glue in the 5050 smd surface is easy to be wet , when you put them in Reflow machine，
then high temperature environment will make the glue expanded , then the glue will pull the packaged wire of ic our of the chip on 5050. so led chip is easy to be broken .
And what is the best temperature for reflow? it is about 235 degree, and the max can not be more than 240degree. too hot is also easy to harm the glue on the surface of 5050.
http://www.normandled.com/upload/201804/SMD%20Products%20Using%20Guide.pdf