a target assembly including a plurality of target tiles bonded to a backing plate by adhesive , for example of indium or conductive polymer , filled into recesses in the backing plate formed beneath each of the target tiles . a sole peripheral recess formed as a rectangular close band may be formed inside the tile periphery . additional recesses may be formed inside the peripheral recess , preferably symmetrically arranged about perpendicular bisectors of rectangular tiles . the depth and width of the recesses may be varied to control the amount of stress and the stress direction .