Research On The Machining Quality Of SiC Sliced By Diamond Wire Saw

SiC crystal is one of the third generation key semiconductor material and widely used for electronic devices, with the machining quality and precision directly influencing properties of the electronic devices. Choosing suitable processing method and parameters is essential to improve the machining efficiency and quality of SiC crystal, since the SiC crystal has a high hardness and belongs to difficult-to-machine materials. This thesis refers to a new fixed abrasive diamond wire saw technology which processes the advantages of thin kerf, high efficiency, good quality, and ability to machine harder brittle and bigger dimension materials and is applied for the machining of hard-brittle materials gradually.It was researched that the surface crack formation mechanism and the machining quality of SiC crystal materials being sawed and grinded by endless electroplated diamond wire saw in this paper, as well as the foundation of relationship between the sawing forces of abrasive and wire saw, the proposal of finite element method analyzing the crack extension, and the prediction of crack depth in sawing surface. The research work and results are given in the following:(1) The advantages and research status of wire saw were summarized, as well as the removal mechanism and machining quality of hard-brittle materials being sawed. Choosing different sawing parameters such as wire saw speed and constant feeding pressure, the endless diamond wire saw cutting SiC crystal were experimentalized, the sawing force and efficiency were recorded.(2) The surface quality of SiC crystal materials being sawed under various sawing parameters was researched. The change of surface morphology, crack damage and surface roughness of the sawed SiC crystal according to parameters were researched through the experience results.(3) The normal and tangential sawing forces as well as the ratio of them which reflecting the sawing difficulty of the SiC sawing experience and existed single crystal silicon sawing experience result were analyzed, proving that the sawing difficulty of SiC can be reduced by improving the wire saw speed and constant feeding pressure and SiC crystal with a higher hardness process a greater machining difficulty. Considering the abrasives are disjunctive distributed on the surface of the wire saw,the relationship between the sawing force of single abrasive and whole wire saw was built.(4) The surface crack production of hard-brittle materials under the effect of single abrasive was analyzed according to indentation fracture mechanics. The stress field of single abrasive and the whole wire saw influencing indentation fracture mechanics crack were founded. The analyzing and calculating method of sawing surface crack produce and expand through finite element method were provided, preparing for the simulation of the material remove and crack production of SiC crystal material being sawed and grinded under the effect of whole wire saw.(5) A theoretical model for predicting the sawing surface crack of SiC crystal was founded, according to the material removal and damage. A theoretical model of relationships between the length of median crack of sawed SiC surface and sawing force, as well as SR and sawing force were founded for predicting the sawing surface damage of SiC crystal. And effective methods to improve the sawing quality of SiC crystal being sawed were stated according to the material removal and damage mechanism.