Research of abrasive embedment-free lapping on soft-brittle lithium niobate wafer

The embedment of abrasives is a large trouble when lapping soft and brittle work-pieces by loose abrasive lapping, which greatly affects the surface quality of the lapped work-piece. A newly developed hydrophilic fixed abrasive (FA) pad was applied to lap lithium niobate (LN) wafers. The orthogonal test was adopted to optimize the processing parameters in the FA lapping, including platen speed, applied load, and abrasive surface. A group of comparison tests of conventional loose abrasive lapping and FA lapping on LN wafers were conducted to explore the embedded abrasive phenomenon. The topography of the lapped LN wafer was observed by Leica microscope and scanning electron microscope (SEM). The suspected points on LN wafers were detected by energy dispersive spectrometer (EDS) to deduce whether they were embedded abrasives or not. The results show that the applied load is the main factor affecting material removal rate (MRR), which is approximately proportional to the load. And the uncoated abrasive surface modification contributes to a smooth surface. When using the same abrasive grain size, the MRR of the loose abrasive lapping is higher and the surface of the FA lapping is smoother. Residual abrasives are found on the wafer surface by loose abrasive lapping, while they are not found on the wafer by FA lapping. Hydrophilic FA lapping takes advantage of abrasives embedment-free over conventional loose abrasive lapping when processing soft-brittle crystals such as LN.