【作者】 赵军；

【导师】 张东明；

【作者基本信息】 武汉理工大学 ， 材料加工工程， 2012， 博士

【摘要】 电子工业中主要用锡铅焊料来完成电子元件的封装连接,但锡铅焊料中的铅对人危害大,世界上许多国家出台一系列政策法令限制铅的使用,因此需要研制可能替代锡铅功能的新材料。导电胶与锡铅焊料有相似的功能,但目前银导电胶成本较高,铜粉有较好的导电率但易氧化,在导电胶中性质不稳定。本文制备了不同形貌系列的银包覆铜粉作导电胶导电填料,并研究了其导电胶的性能。用环保维生素C(Vc)作还原剂和p-糊精作保护剂,成功制备了纳米级的银包覆铜粉体,主要研究了填料顺序、Vc浓度、温度、pH等因素对铜颗粒形貌、大小的影响,分析了各个因素对铜粉生长的作用。以制得的铜纳米粉体为核,采用异相成核的办法制备了银包覆铜粉体,对银层的成核-生长包覆原理进行了研究。用NH3·H20作络合剂制备了微米级的铜颗粒,通过化学置换的方法一次性制备了含银量较高的银包覆铜粉体,对包覆粉体的结构和抗氧化性能进行了研究,并研究了Ag/Cu比例对复合粉银含量的影响。用XRD、TEM、XPS、FT-IR、 TG-DTA等手段表征了铜粉及包覆粉的组成结构,结果制得的包覆粉体银层较为致密,银层含量较高达到90%以上,抗氧化效果明显。研究了温度、模板剂PEG800浓度对片状铜粉的影响,分析了模板剂对片状铜粉生长的导向作用,制备出了(111)方向结晶良好没有氧化的片状铜粉,最终得到较好的制备条件为：CPEG800=90ml/L, T=80℃, CCuSO45H2O=0.2mol/L, CNaH2PO2H2O=0.14mol/L。利用置换的办法制备了银包覆铜片状粉体,研究了不同的Ag/Cu比例对复合粉体含银量的影响,对包覆粉体的结构进行了表征和抗高温氧化性测试,显示包覆后的铜粉抗氧化效果明显。用乙胺、联氨、NaOH为原料在常压低温80℃下制备了铜纳米线,研究了乙二胺浓度、NaOH浓度、温度、搅拌作用对铜纳米线生长的影响,利用置换法制备了银包铜纳米线,分析了包覆机理。铜纳米线较好的制备工艺为,乙二胺17.5ml/L、NaOH为17.5M、反应温度为60℃、不搅拌的情况下可得较好的铜纳米线。研究了Ag/Cu比例对银包覆铜纳米线的影响,结果显示铜纳米线因比表面积大,易造成铜的大量损耗。将环氧树脂用丙酮稀释,在环氧树脂：丙酮=6：4时,粘度15.11mPa-s的树脂基作为导电胶基体。将所制备的粉体作为导电填料与树脂基复合制备导电胶。对不同形貌的铜粉和银包覆粉导电胶的导电性研究发现：包覆粉的导电胶导电性明显高于同比铜粉导电胶,因为包覆粉体的载流子浓度高于未包覆粉体；片状填料导电胶明显高于球状填料导电胶,因片状粉体导电胶的接触点较多,容易形成导电通路。另外,研究也发现,添加纳米导电粉体对提高导电胶的导电性无益,因为纳米粉体比表面积大、吸胶量大,当纳米粉体位于接触点中间时,相当于增加了接触电阻,导致整个导电胶的电阻率提高。所制备的Ag包覆Cu导电胶的性能与目前国内Ag导电胶的性能相当,但成本大幅降低。更多还原

【Abstract】 In electronic industry, Sn-Pb solderring alloy is used as electronic packaging material. But Sn-Pb soldering is harmful to human because of the existed Pb. Many countries in the world have made policies to restrict the use of substance containing Pb. So investigation of new material to substitute the Sn-Pb soldering is helpful. Conductive resin has the similar performance as Sn-Pb soldering. And the epoxy conductive resin is friendly to human. Now most epoxy resinsare filled with silver powders, which are expensive. Although copper has the similar electric resistivity with silver, it is easy to be oxidized in atmosphere. In this work, different morphologies of coppers are prep ared and are coated with silver to insure them stable. And the coated powders are used as fillers in epoxy resin.Envirmental friendly chemical agents of vitaminC(Vc) as reducing agent and β-cyclodextrins as protective agent were used to prepare monodisperse copper and coated copper nanoparticles. The influences of adding sequence, concentration of Vc, reacting temperature and pH on copper were disscussed. Ammonia as complexing agentis used to combine with copper ions to prepare micron scale spherical copper particles. Different Ag/Cu ratio affects the coating layer outside the copper. And the prepared particles were characterized by XRD, TEM, XPS, FT-IR, TG-DTA. Results show that copper particles were coated with dense silver shells. And TG-DTA reveals the coated copper particles have better oxidation-resistance.Flake copper particles were prepared with PEG800as template agent. Effects of PEG800volume concentration and reacting temperature on flake coppers were studied. And effect of PEG800in forming flake copper was analysised. The copper crystal has a (111) preferential orientation. The best conditionsfor preparing flake coppers were CPEG800=90ml/L, T=80℃, CCusO4·5H2O=0.2mol/L, CNaH2O·2H2O=0.14mol/L. Silver coated flake copper were prepared by replacement. And the influence of Ag/Cu on composite was discussed. Also composite powders were characterized and TG-DTA revealed their higher oxidation resistance.Copper nanowires were synthetized with quadrol, hydrazine and sodiumhydrate. The quadrol guided the orignal reduced copper nanoparticles to growth into nanowire. Effect of concentration of quadrol, concentration of sodiumhydrate, reacting temperature and stir speed on copper nanowire growth were studied. Better copper nanowires can be obtained by following conditions:quadrol concentration of17.5ml/L, hydrazine concentration of17.5M, reacting temperature of60℃. Influence of different Ag/Cu ratio on coated copper nanowire was studied. The coated copper nanowire was characterized. Results show that the Cu nanowires havea heavy loss at the Ag/Cu>1, because the nanowire has a high specific surface and a rapid replace reaction rate with silver. TG-DTA revealed that resistance to oxygen for silver coated copper nanowire has been improved greatly.Epoxy is used as matrix to prepare conductive adhesive. First, viscosity of epoxy is diluted with different epoxy/acetone mass ratio. As epoxy/acetone mass ratio is6:4, the adhesive has a proper viscosity of15.11mPa-s, which is suited for preparing conductive adhesive. The different morphologies of particles are used as fillers in epoxy matrix. Specific resistance and shear strength of epoxy resin were tested. Results show the spherical particles have a higher specific resistance than flake particles. Coated copper has lower resistance than uncoated copper. The volum resistivity is decrease with the increase of volume fractions of particles. The conductivity for adhesive with flake particles as fillers is higher because there are more contacts sites than spherical particles do. The conductivity of coated copper is higher than that of pure copper because core-shell structure affects electronic distribution. Further more, the addition of nanoparticles can’t improve the conductivity of epoxy resin, because the added nanoparticles increase the thickness between the particles, which is equivalent to increase contact resistance.更多还原