A composite backing plate (34) for a backing plate-target assembly (41) having a core of structural material (36) with a front face (42) and/or a rear face (44) of a different material laminated thereto. The composite backing plate (35) has the desired mechanical properties of a solid copper backing plate, for example, strength and stiffness, but is preferably less than half the density of a solid copper backing plate. The core material is preferably aluminum; the front face is preferably copper; and the rear face is preferably either copper or an organic material.