Statistical characterization of the lapping plate surface morphology evolution in a diamond charging process

The topographical evolution of a lapping plate surface during a diamond charging process was followed by analysis of atomic force microscopy (AFM) images. AFM measurements were performed in the tapping mode on several Sn–Sb alloy lapping plates containing different amounts of encrusted diamond particles on their surface. Such plates were processed under different charging times at the Lapping Plate Area of Hitachi Global Storage Technologies in Guadalajara, Mexico. Statistical functions were applied to the AFM data to determine the height and spatial characteristics of the plate’s surface roughness. The resulting probability density function of heights, height–height correlation function (HCF) and power spectral density (PSD) showed characteristic patterns of evolution related to the amount and distribution of diamond particles incorporated on the plates. The HCF evolution proved how the locally non-flat initial plate surface evolves into a self-affine fractal after the plate is uniformly charged. Surface roughness parameters were found to increase during diamond charging up to a saturation value. The statistical analysis of surface slopes allowed determining the average angle of diamond edge protrusion. According to our results, the RMS roughness along with the HCF morphology analysis could be used to establish quality control measures for diamond charged lapping plates.