Original post by: Minho ,
If you are using a Rosin based flux (RMA or RA - unlikely as that is a dark flux) then you would definitely have to clean it off. If you are using a No Clean flux, then you shouldn’t have to worry about it. That said, it really depends on the flux. I am currently using the Chipquik 291 and I don’t like it at all. I find that it tends to crystallize and it can be hard to remove. You could try to put some IPA or better yet, real [https://electronics.microcare.com/product-category/flux-removers/|flux remover], that will dissolve most of it.