【作者】 张宏；

【导师】 汤文明；

【作者基本信息】 合肥工业大学 ， 材料学， 2010， 硕士

【摘要】 从上世纪90年代开始,随着电子工业的发展以及人们环保、健康意识的提高,无铅材料及无铅化技术的研究日益兴起并逐渐用于生产。焊料无铅化是电子产品无铅化一个重要方面。焊膏是常用的焊料类型,主要由无铅合金焊粉组成,是电子组装中重要的连接材料。机械合金化(MA)技术常用于合成二元及多元系非平衡合金粉体,其优点是不受合金元素种类及含量的影响,在常温下即可实现固态合金化,还可以有效地避免合金成分偏析,可望用于制备Sn基焊料合金微粉。本文采用高能球磨的机械合金化技术在室温条件下球磨制备了Sn-Ag、Sn-Cu二元和Sn-Ag-Cu三元合金粉体。采用X射线衍射仪(XRD)、透射电镜(TEM)、扫描电镜(SEM)、差示扫描量热仪(DSC)和粒度分析等手段对球磨过程中粉体的结构演变、显微组织、粉体形貌及颗粒尺寸变化等进行了研究;讨论了合金化机制;研究了合金成分变化对Sn合金焊料粉体结构的影响。同时,还研究了合金化粉体的熔点及再流焊后焊料的显微组织结构,并对该Sn基粉体的可焊性进行了初步评价。Sn-Ag二元合金粉体由球磨初期的大块层片状复合颗粒,逐渐碎化,最终演变为细小均匀的球状颗粒。MA 60 h合成的三种成分Sn-Ag(2-5 wt% Ag)合金粉体粒径主要分布于0.1-20μm,Ag含量的提高使得粉体塑性增强,颗粒粒径增大。MA合成的Sn-3.5Ag合金粉体颗粒是由Sn(Ag)、Ag3Sn纳米晶粒构成,熔点为224℃。在Al2O3陶瓷基底上熔化后的焊料由先结晶Sn卵状颗粒及Ag3Sn颗粒和(Ag3Sn+Sn)共晶组织构成;在Cu基底上熔化后的Sn-3.5Ag焊料还在与Cu基底的界面处生成杆状的Ag3Sn,基体中则析出针状的Ag3Sn。Sn-Cu二元合金粉体由球磨初期的大块层片状复合颗粒组成,逐渐细化为形状不规则的团聚体;继续球磨,团聚体解散,进一步细化成细小的球状颗粒。MA 60 h合成的三种成分Sn-Cu(0.7-10 wt% Cu)合金粉体粒径也主要分布在0.1-20μm,Cu含量的提高使得粉体脆性增强,颗粒粒径减小。MA合成的Sn-10Cu合金粉体颗粒由Sn(Cu)、Cu6Sn5纳米晶构成;MA 60 h的Sn-0.7Cu、Sn-10Cu粉体的熔点分别为231℃、228℃。在Al2O3陶瓷基底上熔化后的焊料组织由先结晶Sn卵状颗粒及Cu6Sn5和(Cu6Sn5+Sn)共晶组织构成;在Cu基底上熔化后的Sn-0.7Cu焊料还析出了六方结构的Cu6Sn5。Sn-Ag-Cu三元合金粉体形貌与上述二元粉体类似,最终获得微细的近球状颗粒。MA 60 h的Sn-3.5Ag-0.7Cu粉体由Sn(Ag, Cu)、Ag3Sn和Cu6Sn5纳米晶粒构成,粉体平均粒径为19.9μm,熔点为219℃。随着Ag、Cu含量的增加,粉体中Ag3Sn和Cu6Sn5的含量增加。在Al2O3基底上熔化后的焊料组织呈过共晶组织状态,由先共晶β-Sn卵状颗粒和(β-Sn + Cu6Sn5 + Ag3Sn)共晶组织组成。在Cu基底上熔化后的Sn-3.5Ag-0.7Cu合金在Cu界面前沿形成由Cu6Sn5和Cu3Sn构成的连续薄层,焊料在Cu基底上的润湿角约为20°。此外,在焊料组织内部还析出了六方结构的Cu6Sn5块,在Cu基底界面前沿析出了板条状的Ag3Sn。更多还原

【Abstract】 With blooming electronic industry and increasing consciousness of environment-protection and health concerns, Pb-free materials and technologies have attracted more attention and gradually applied in the electronic industry since 1990s. Pb-free Sn-based alloy solders are key materials of manufacturing the Pb-free electronic products. As one type of the alloy solders, the solder pastes mainly consisting of lead-free alloy powders, are widely used in joining the electronic devices. It is known that mechanical alloying (MA), a non-equilibrium powder forming technology, is usually utilized to synthesize the binary and/or multi-element metals powders. The advantages of the MA technology are that the varieties and contents of raw materials are not restricted, and the composition segregation can be effectively avoided. It is believed that the MA technology can also be used to synthesize the Sn based alloy powders.In the present study, the MA technology was taken to synthesize the Sn-Ag, Sn-Cu and Sn-Ag-Cu powders at room temperature. Structural evolutions, morphologies and alloying mechanism of the Sn-based alloy powders during MA, melting temperatures of the milled powders, and microstructures of the melted Sn-based alloy solders were investigated using XRD, TEM, SEM, DSC and laser particle size analyzer. Moreover, the effects of the Ag, Cu compositions on the microstructures of the Sn-based alloy powders were also discussed, and the soldering characteristics of the milled powders was preliminarily evacuated.The Sn-Ag binary alloy powders are of large lamellar composite particles in the initial stage of MA. As increasing the milling time, they are gradually fractured into finer lamellar particles, and finally the ultrafine spherical particles are formed. The particle sizes of the 60 h milled Sn-Ag alloy powders (2-5 wt%Ag) increased with increasing the Ag content, but all situated in the range of 0.1-20μm. The milled Sn-Ag alloy powders was composed of nanocrystalline Sn(Ag) and Ag3Sn particles. The melting point of the 60 h milled Sn-3.5Ag powders was tested to be 224°C. After the 60 h milled Sn-3.5Ag powders melted on the Al2O3 substrate, the Sn-3.5Ag alloy solder was composed of the primaryβ-Sn and Ag3Sn particles and the (Ag3Sn+β-Sn) eutectic structure. Long Ag3Sn laths are located at the Sn-3.5Ag solder/Cu substrate interface and Ag3Sn needles are embedded in the solder.The Sn-Cu binary alloy powders are also made up of a lamellar composite structure in the initial stage of MA. As increasing the milling time, they are gradually fractured into irregular particles. Finally the superfine Sn-Cu alloy powders are formed. The particle sizes of the 60 h milled Sn-Cu alloy powders (0.7-10 wt%Cu) decrease with increasing the Cu content, but all situated in the range of 0.1-20μm. The milled Sn-Cu alloy powders was composed of nanocrystalline Sn(Cu) and Cu6Sn5. The melting points of the 60 h milled Sn-Cu alloy powders decreased from 231 oC to 228 oC with increasing the Cu content from 0.7 wt% to 10 wt%. After the 60 h milled Sn-0.7Cu alloy powders melted on the Al2O3 substrate, the Sn-0.7Cu solder was composed of the primaryβ-Sn and Cu6Sn5 particles and the (Cu6Sn5+β-Sn) eutectic structure. Except those phases, the hexagonal coarse Cu6Sn5 particles are also detected in the Sn-0.7Cu solder, after the 60 h milled Sn-0.7Cu alloy powders melted on the Cu substrate.The structural evolutions and the morphologies of the Sn-3.5Ag-0.7Cu ternary alloy powders during mechanical alloying are similar to the Sn-Ag and Sn-Cu binary powders. The untrafine spherical Sn-3.5Ag-0.7Cu powders are finally obtained. The 60 h milled Sn-3.5Ag-0.7Cu powders was composed of nanocrystalline Sn(Ag, Cu), Ag3Sn, and Cu6Sn5 particles. The average particle size (D4, 3) and the melting point of the powders were tested to be 19.9μm, and 219 oC, respectively. After the 60 h milled Sn-3.5Ag-0.7Cu powders melted on the Al2O3 substrate, the solder consists of the hypereutectic structure of the primaryβ-Sn particles and the (β-Sn+Cu6Sn5+Ag3Sn) eutectic structure. Soldering of the milled Sn-3.5Ag-0.7Cu solder powders on the Cu substrate was well performed with a wetting angle around 20°, showing a good wettability. The continuous scallop-like Cu6Sn5 and Cu3Sn layers are formed along the Sn-3.5Ag-0.7Cu solders/Cu interface. Meanwhile, the Ag3Sn laths at the solder/Cu6Sn5 layer interface, the hexagonal coarse Cu6Sn5 plates in the solder are also detected.更多还原