A succession of electronic circuit board blanks contoured in a board blank strip support electronic parts such as microcomputers and other components thereon and are joined at spaced intervals by narrow joints such as ribs which are spaced considerably apart from the microcomputers which are highly susceptible to stresses. When the board blanks are severed from each other by cutting off the joints, no substantial stresses will be applied to the microcomputers on the board blanks. The board blanks can easily be separated automatically into electronic circuit boards successively.