The beam is very narrow and the heat affected zone is minimized.  The penetration of the weld can be precisely adjusted from near zero to as much as 6 inches.  Distortion and metallurgical effects are much less than other types of welding such as TIG and MIG.  Dissimilar metals can be joined such as copper to stainless steel.  The weld itself is very pure due to the lack of contamination in the vacuum chamber.  Reflectivity is not a factor in EB welding like it is in laser welding.  Some applications benefit from the residual vacuum that is retained in a hermetically sealed enclosure once it is electron beam welded closed.  EB is a well-proven technology having been around since the 1950’s.