【作者】 侯志坚；

【导师】 葛培琪；

【作者基本信息】 山东大学 ， 机械制造及其自动化， 2008， 博士

【摘要】 集成电路（IC）多以单晶硅片为衬底材料,为降低单元制造成本,要求单晶硅片的直径也越来越大。切片是硅片制造的关键工序,对于直径大于300mm的单晶硅普遍采用往复式自由磨料线锯切片技术。往复式自由磨料线锯加工,其材料去除机理是研磨,加工效率较低,且不能切割硬度更高的碳化硅晶体、陶瓷等材料。本文提出环形树脂结合剂金刚石线锯切割这一新工艺,利用固结在线锯丝基体上的金刚石磨粒直接磨削去除材料,减轻加工面表层损伤,环形线锯丝单方向高速连续运动,大大提高切割速度和效率。可用于硅晶体切片及高硬度材料切割加工。具有切割精度高、制造成本低、对环境无污染等优点。本文设计制造了环形锯丝线锯床。该锯床使用环形金刚石线锯丝,可实现环形线锯丝单方向连续运动。线锯丝走丝变速范围是4.5-28m/s,满足切割不同材料的要求。根据锯切实验要求,可实现无级调速的伺服电机驱动和是恒进给力驱动的两种进给方式。利用外加力矩张紧线锯丝,张紧力可以定量调节,张紧力范围14.6-25.2N。通过装配时精密研磨轴承安装孔、配装调节轴承间隙等关键工艺,提高了锯床精度和刚度,大大降低了线锯丝振动振幅,提高了锯切表面面形精度。分析研究了304不锈钢丝（直径0.4mm）、304L不锈钢丝（直径0.3mm）、65Mn弹簧钢丝（直径0.3mm）以及SWPB钢琴丝（直径0.3mm）的力学性能。304不锈钢丝屈服拉力为140N;304L不锈钢丝的屈服拉力为45N;65Mn弹簧钢丝断裂拉力为131N,SWPB钢琴丝断裂拉力为104N。304L不锈钢丝的弹性变形较小,而SWPB钢琴丝含碳量高、焊接性能差。故选304不锈钢丝和65Mn弹簧钢丝作为环形线锯丝的基体材料。两种材料的弯曲疲劳寿命均达到1×10⁶次以上。采用电阻对焊工艺,分别将304不锈钢丝和65Mn弹簧钢丝焊接成环状。304不锈钢丝焊接接头断裂拉力为110N,65Mn弹簧钢丝焊接接头的断裂拉力90N。304不锈钢焊缝区由细小的奥氏体和铁素体组成,具有较大的强度和韧性。因此,304不锈钢丝更适合作为环形线锯丝的基体材料。实验研究表明,304不锈钢丝和65Mn弹簧钢丝焊接接头的疲劳寿命均达到1×10⁵次以上。在本文实验条件下,304不锈钢丝焊接接头的平均疲劳寿命约100分钟,65Mn弹簧钢丝平均疲劳寿命约50分钟。对树脂结合剂金刚石线锯丝制造工艺进行研究和优化。树脂结合剂金刚石线锯丝制造成分包括树脂、金刚石磨粒和粉粒添加剂等。树脂主要起粘接作用,将金刚石磨粒和线锯丝基体牢固地黏接在一起,金刚石磨料是切割工件的主体材料,分别选用了超细铜（Cu）粉、纳米氧化铝（Al₂O₃）粉、纳米二氧化锆（ZrO₂）粉、纳米氮化钛（Ti（CN））粉作为树脂添加剂,研究了不同添加剂对结合剂耐磨性的影响规律,实验证明纳米二氧化锆（ZrO₂）粉作为添加剂效果最好。实验研究了固化温度、固化时间对树脂结合剂强度的影响规律,随固化温度增高、保温时间延长,结合剂强度增大。根据锯切实验结果,用正交试验法对线锯丝制造成分的含量进行了优化,树脂结合剂中环氧树脂含量对结合剂的耐磨性影响最大。研究了锯切参数对锯切表面粗糙度的影响规律。线锯丝速度分别为4.5m/s,7.7m/s和11.8m/s,工件进给速度分别为0.033 mm/s,0.083 mm/s和0.140 mm/s三种,也采用了恒进给力驱动方式。线锯丝的张紧力分别为14.6N,19.9N和25.3N。实验揭示了线锯丝速度、进给速度、线锯丝与工件接触长度、线锯丝张紧力以及恒进给力驱动进给方式对锯切表面粗糙度的影响规律,并对实验结果进行分析。进行了不同线锯丝运动方式和不同结合剂锯丝的锯切比对实验。与往复运动锯切表面相比,环形线锯丝锯切表面切割纹理没有明显的方向性。与金属结合剂金刚石线锯锯切表面相比,树脂结合剂线锯丝锯切表面平整,无崩碎现象,并且凹坑及凸起处棱角圆滑。可见环形树脂结合剂线锯丝能获得质量更好的切片表面。树脂结合剂磨损和脱落是树脂结合剂线锯丝的微观失效原因。优化各种材料的含量、改善结合剂的固化工艺是提高树脂结合剂的强度的有效措施。分析了环形线锯丝的工作状况,建立了环形线锯丝最小预紧力数学模型。线锯丝最小预紧力与从动轮的摩擦力矩、导轮直径、线锯丝与导轮之间的摩擦系数、线锯丝包角以及线锯丝速度都有关系。导轮摩擦阻力越大,导轮直径越小,所需的预紧力就越大;线锯丝包角越小,所需的预紧力也越大。反之,所需预紧力减小。用实验方法测量实验设备轴承的摩擦力矩,据此计算出使用本线锯床时,线锯丝的最小张紧力为7.8N。建立了线锯丝上单个磨粒受力模型,在不考虑线锯丝弯曲变形的情况下推导出锯切力公式。锯切力与多种因素有关,本文应用实际测量的方法确定锯切力随线锯丝速度以及工件进给速度的变化规律。分析了线锯丝弯曲变形、线锯丝变形位移以及锯切力大小对线锯丝拉力增量的影响规律,拉力增量与切割区线锯丝弯曲曲率半径及线锯丝单位长度上法向力成正比:锯切力引起的增量还与线锯丝受力后相对原始位置的位移有关,位移增大,线锯丝拉力增量减小。虽然锯切力很小,但使线锯丝产生的拉力增量不可忽略。更多还原

【Abstract】 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.更多还原