Preparation And Size Classification Of Alumina Series Abrasive Particles For Chemical Mechanical Polishing

Alumina plays an important role in precision machining manufacturing industry due toits advantage of high degree of hardness and fine stability properties. Alumina is particularlywidely accepted for its application in chemical mechanical polishing (CMP). Micro-scratcheswill hardly appear when spherical alumina is used in CMP, and spherical alumina becomes tobe the main raw materials of CMP abrasive. The studies on the preparation of sphericalalumina are active in China and abroad. Though using emulsification, chemical vapordeposition and other methods to prepare alumina sphere has made some achievement, but thepreparation of sub-micron alumina sphere is not still satisfied. The material and report aboutthe study of this problem is quite scarce. The main work of this dissertation is around thepreparation and size classification of alumina series abrasive particles for CMP.Alumina is prepared from aluminum isopropoxide by the way of hydrolyze method,emulsion method and pressurized pyrolysis method. The characterization of productmorphology, structure and composition was carried out by TEM, SEM, XRD and TG etc.respectively. Finally cause to different alumina morphology has been discussed preparatorily.Size classification of alumina series abrasive is mainly against the alumina-silica fume ofhigh alumina content which size distribution is between 0.1μm to 10μm. Aluminum-siliconpowder suspension has been classified by centrifugalization or subsidence. The optionalcondition has been found by investigating the influence of different kinds of solvent anddispersants, addition quantity of dispersants and ultrasonication etc to suspensionperformance of the powder in dispersion media. Size classification has been realized bycontrolling subsidence time or centrifugation rotational speed. The precision and accuracy oftwo methods have been compared.Main results are as follows:1. Hydrolyze method. Spherical and submicron alumina is prepared by controlling ratioof [Al³⁺]/[SO₄^2-] and ageing time.2. White and fleecy powder is gotten from aluminum isopropoxide by pressurizedpyrolysis method. During gradual increase of temperature to 1200℃, completedcrystallizationα-Al₂O₃ is gotten. It keeps the same morphology with the spherical precursor.3. Alumina-silica fume is hydrophilic substance, so it has better dispersion effect in polarsolvent than in non-polar solvent. The suspension of aluminum-silicon powder has been prepared by adding kinds of dispersants. PAA, PAM and CTAB show better dispersion effectas dispersants. The optional addition quantity is found by considering dispersion effect andmaterial cost. Ultrasonic wave concussion makes better dispersion effect but need no toomuch time, 30min is enough.4. Different alumina-silica fume particle levels of 2.3μm, 1.7μm, 1.4μm and 0.7μm aregotten by centrifugalization or subsidence. Size classification has been realized.