The Manufacturing Technologies And Slicing Experiments Of Looped Diamond Wire

Most integrated circuit(IC) base are built on single crystal silicon wafers.For the decreasing of machining cost,the dimension of wafer increases continuously.Slicing is the key process in the manufacture of silicon wafers.Now the oscillatory free abrasive machining technique are used widely for the slicing wafer that diameter is larger than 300mm.Oscillatory free abrasive machining technique is low at productivity for the reason that material is removed by lapping and it is impossible to cut more harder material,such as SiC crystal or ceramics et al,using free abrasive machining technique.A new technique to cut silicon and other harder material with looped resin bond diamond wire is introduced in this paper,in which the grits fixed in wire grind material directly and benefit to reduce surface damage layer.The looped wire can move at high speed in one direction continuously,so the productivity is higher.This method can be used in the slicing wafer of silicon and the cutting of other harder materials.The technology is high at cutting accuracy,low in cost and no pollution.A wire saw to use looped fixed diamond abrasive wire is designed and made.The looped wire moves in one direction continuously.The wire velocity ranges from 4.5m/s to 28m/s,which meet to cut different materials.Feeding movements includes servomotor driving and constant force driving to meet the requirement of sawing experiment.The wire tension that span from 14.6N to 25.2N can be adjusted quantity by adding a torque.Some key technologies,such as,lapping bearing holes and regulating bearing clearance having been adopted,the saw is high at accuracy and good at rigidity,so the vibration amplitude of the looped fixed diamond abrasive wire is reduced greatly and cutting accuracy is higher.The mechanics performances of 304 stainless steel wire(diameter 0.4mm),304L stainless steel wire(diameter 0.3mm),65Mn spring steel wire(diameter 0.3mm) and SWPB piano wire(diameter 0.3mm) are researched.The yielding tension of the 304 stainless steel wire is 140N;the yielding tension of the 304L stainless steel wire is 45N; the broken tension of 65Mn spring steel wire is 131N and the broken tension of SWPB piano wire is 104N.304L stainless steel wire is weaker in plastic and the SWPB piano wire is weaker in welding properties for its higher carbon,so 304 stainless steel wire and 65Mn spring steel wire are chosen as base material of looped wire.Bend fatigue times of both materials exceeds 1×10⁶ times.Been welded into looped shape respectively,the welding joint broken tension of the 304 stainless steel wire gets 110N and the broken tension is 90N for 65Mn spring steel wire.The welding joint of the 304 stainless steel wire consists of fine austenite and ferrite that are higher at strength and tenacity,therefore,304 stainless steel wire is more suitable to be the base material of looped wire.The welding point fatigue life of the 304 stainless steel and the 65Mn spring steel wires are investigated and both fatigue life exceeds 1×10⁵ times.The average fatigue life of 304 stainless steel wire is about 100 minuets and the average fatigue life of 65Mn spring steel wire is about 50 minuets under experiment condition in this paper.The technology to make resin bond diamond wire is studied and optimized.The composition includes resins,diamond and some additives;in which wire is connected with diamond by resin bond and diamond is main material to remove material,fine Cu, nanometer Al₂O₃,nanometer ZrO₂ and nanometer Ti(CN) powder are chosen respectively as an additive in order to study the influence of additives on the strength and resistance of wear.It is the most effective for nanometer ZrO₂ powder to be additive.The rule that heating temperature and time influence on resin bond strength is studied also.With the increasing of heating temperature and time,the strength of resin bond increases.The quantity contained is optimized by orthogonal tests according to cutting experiment result and the quantity of epoxy resin has key influence on the wear resistance of resin bond.The study on single crystal silicon cutting roughness and its influence factors are carried out.In which the wire speeds are 4.5m/s,7.7m/s,11.8m/s and the feeding speeds are 0.033mm/s,0.083 mm/s,0.140 mm/s respectively,constant force driving model is put to use also.The wire tension are 14.6N,19.9N and 25.3N.The influence rules of wire speeds,feeding speeds,the contact length between wire and work piece, the wire tension and constant driving model on cutting roughness are indicated and the experiment results are analyzed.The experiments in which wire moves oscillatory and that electroplated diamond wire is used are carried out.There is no obvious ripple in the surfaces obtained using looped diamond wires compared with one got from the oscillatory wire saw.The cutting surfaces obtained using resin bond diamond wire is smoother without fragment compared with one obtained from the electroplated diamond wire,so it can get better surface at quality for looped resin bond diamond wire to cut.The resin bond wear and to fall off is the main reason of microcosmic failure.These are effective measures to optimum the quantity contained of each component and to improve the solidify technology of resin bond.The working condition of the looped wire is analyzed and a mathematics model on minimum tension of wire is built up.The minimum tension of wire has relations to the guide wheel friction torque,diameter,and friction coefficient between wire and guide wheel,wire wrap angle and wire velocity.The bigger the friction is,the little guide wheel diameter is,the bigger tension of wire needed is.In contrary,the tension of wire gets less.The minimum tension of wire is 7.8N from the calculation based on the friction torque getting in measuring experiment,when this wire saw is used.A model the single grit subjected to force is introduced and the cutting force formula is got to omit the influence of wire curved deform.The cutting force relates to many factors.The change rule between cutting force and velocity,feeding velocity is determined by experiment.The influence of wire curved deforms,displacement and cutting force on the adding pulling of wire is analyzed.The wire adding amount pulling subjected to is proportioned to the curved radius in cutting area and the normal unit force.The adding pulling of wire relate to the displacement with original location of wire also.With the increasing of wire displacement,the adding pulling of wire gets less.Although the cutting force is less,the adding amount cannot be neglected.