Investigation of the progressive wear of individual diamond grains in wire used to cut monocrystalline silicon

The wear of diamond-coated wire is an important cost driver in the multi-wire sawing of silicon-based photovoltaics. Understanding the different forms of diamond wire wear could help the solar energy industry to be more competitive by reducing wafer costs. In this study, an innovative method was applied to investigate the wear of diamond wires: several diamond grains in a diamond wire loop were tracked during the slicing of monocrystalline silicon. The grains attached to the wire were analyzed by scanning electron microscopy and focus variation microscopy. Based on the observed non-uniformity of wear on the perimeter of the cross-section of the wire, the rotation of the wire on its longitudinal axis was investigated. A new method that promotes wire rotation during cutting was successfully applied. The form and progression of the wear were also investigated by tracking single grains during the cutting process. Observations show the occurrence of nickel layer removal/deformation, micro-chipping of the diamond grains, abrasion wear, and sporadic grain pullout.