The invention relates to a
diffusion welding method of a
copper target material and a back plate. The
diffusion welding method comprises the following steps that (1), the
copper target material, the back plate and a
cushion block, wherein the back plate is provided with a groove, and the areas of the
copper target material and the
cushion block are equal to the bottom area of the groove of the back plate; (2), the copper target material and the
cushion block in the step (1) are sequentially put into the groove of the back plate to finish
assembly treatment, and then a
whole body is put into asheath; (3), the sheath obtained in the step (2) is sealed and then degassed; and (4),
hot isostatic pressing welding is carried out on the sheath degassed in the step (3), and then the sheath and thecushion block are removed to finish
diffusion welding of the copper target material and the back plate. According to the
diffusion welding method, by improving an
assembly structure of the copper target material and the back plate, the bonding degree of welding faces of the copper target material and the back plate is guaranteed, abnormal growth of
crystal grains is effectively avoided, and particularly the phenomenon that the
crystal grains are thick and large at the edge of the copper target material is avoided.