Surface damage characteristics of AlN ceramics induced by ultra-precision grinding

Abstract

ABSTRACT Aluminum Nitride (AlN) ceramic substrate is applied for heat dissipation of high-power devices, and its processing quality directly determines the service life. Ultra-precision grinding is a promising method for low-damage machining of AlN ceramics. In this paper, the ground surface quality, damage characteristics in the brittle and ductile removal regime were investigated by ultra-precision grinding, and the material properties and damage mechanism for AlN ceramics were revealed using indentation tests. The results show that with the reduction of grits size, the surface quality was greatly improved. Finishing grinding with the #5000 diamond wheel can produce a smooth surface with roughness S a 0.003 μm. The multiple nanoindentations indicated that the hardness and strength distribution at the nano-scale depth present obvious anisotropy, where grain boundaries are in the weak position. Propagation of brittle cracks along grain boundaries would induce AlN grains spalling in brittle removal. Besides, anisotropy of strength can cause random damage in ductile removal. Based on the critical cutting depth model, the critical depth of brittle-to-ductile transition for AlN ceramics is about 90 nm. The present study reveals the feasibility of ductile grinding for AlN ceramic substrates.