Coupling stress caused by thermal and slicing force in KDP crystal slicing with fixed abrasive wire saw

Abstract

KDP (KH2PO4) crystal is an important functional crystalline material that can be used in the area of laser frequency conversion. As the first process of machining, the slicing process of the KDP crystal is of vital importance to the yield rate of wafers. While the KDP crystal often cracks in the slicing process by the traditional method of band saw because of its properties of high brittleness, low strength, and high thermal sensitivity, the cracks may lead to waste of the whole KDP crystal and should be avoided. Fixed abrasive wire saw slicing is considered a preferred method for KDP crystal slicing due to its advantage of low sling stress. In this paper, a finite element model in fixed abrasive wire saw slicing of the KDP crystal is established with respect to distributed slicing force and thermal stress. Distribution of slicing force and heat around the kerf area is deduced and applied to the finite element model. Based on the model, temperature field and stress field of the KDP crystal in the slicing process is obtained. The maximum principle stress caused by slicing force, thermal stress, and coupling of the slicing force and thermal stress is obtained. The maximum principle stress of different slicing parameters is analyzed; function equation between the maximum principle stress and slicing parameter is obtained by the least squares method. The critical slicing parameter at which cracks would not occur in the slicing is obtained. The simulation results in this paper are useful to avoid cracking in KDP crystal slicing with fixed abrasive wire saw.