Can I use a figure under CC BY-SA 3.0 in an academic paper CC BY-SA requires that you distribute anything derivative of the work with the same license. 

I found a very nice but complex diagram (let's say a CAD model) under this license and I  would like to modify it to add the relevant information on top of it for an introduction to a paper. Can I use this image on a scientific paper in any case, or I must make sure that the paper itself is under CC BY-SA?
Of course your revised figure must be released under a compatible license. However, I doubt that the paper as a whole can be considered a "derived work" under copyright law. Of course it is possible that the paper focuses so much on that figure that it actually is derived from it, but that seems unlikely.