No. pretty much (gross oversimplification, but this is the essence of it) all you need for a nuclear bomb is to slam 2 or more subcritical chunks of sufficiently enriched uranium into each other fast enough to fuse them to a single supercritical chunk of the above, and you have a boom. The hard part is the uranium. Compared to producing the uranium, designing and manufacturing a viable bomb is trivial.

I remember reading about a US research project where someone with reasonable physics knowledge, but no specific knowledge on the workings of atomic bombs, managed to put together viable plans for a bomb from only publically available information.