【作者】 孟繁琦；

【导师】 高家诚；

【作者基本信息】 重庆大学 ， 材料科学与工程， 2006， 硕士

【摘要】 电触头亦称触点或接点,是电器开关、仪器仪表等的接触元件,担负着通断电流的任务。因此,它的性能直接影响着开关电器的可靠运行。Ag-W触头具有良好的导热和导电性能、耐电磨损性能、抗熔焊性能、抗氧化能力等优点。银铜锌焊料是一种广泛使用的银基钎焊料。其特点是熔点较低,润湿性及填缝能力好,接头强度高等。因此,进行触头焊料扩散连接的工艺和机理研究,对触头和焊料的应用具有重要的理论意义和实际应用价值。本文采用X射线衍射仪(XRD)、扫描电镜(SEM)、显微硬度计、数字电桥等先进测试手段对界面附近区域的显微组织、电性能、相结构、断口形貌、能谱和元素的扩散分布进行了分析;通过正交试验扩散连接,研究了加热温度、保温时间、外加压力等工艺参数对扩散连接材料的电性能以及结合强度的影响,优化了工艺参数;根据Fick第二定律,采用误差函数解和能谱分析结果计算了触头焊料扩散焊接时Cu原子在银中的扩散因子D0以及扩散激活能Q,以及Cu原子扩散的距离,与实际测得的距离进行了对比分析。研究结果表明,在进行探索性试验时,在较低的压力下,加热温度低于700℃时,由于加热温度较低原子的扩散能力不足,试样之间不能形成有效地扩散。在进行正交试验分析时,分别以电阻率和结合区线百分比为指标分析时所得的结果不同。并以电阻率和结合区线百分比以3:1的权重分析,得到了本试验条件下的最佳工艺参数。在最佳工艺条件下进行的验证试验表明,所得的电阻率和结合区线百分比都有很好的重复性。进行无压扩散连接时,银中间层的含量对触头焊料的电性能有较大的影响,含银中间层较多时有更为优良的电性能。在本试验条件下,影响结合的三个工艺参数由主到次分别为焊接温度、外加压力、保温时间。触头焊料最佳的扩散连接工艺条件是675℃×2h、0.09MPa。采用本工艺条件,可以使银钨触头和银铜锌焊料较好地扩散连接在一起。连接后的电阻率为4.5343??mm。对连接区进行物相分析表明,在触头侧生成了CuZn相,在焊料侧并没有发现新相。触头焊料扩散焊接头的断口分析表明,接头具有一定的韧性,断裂从银过渡层处开始,缝隙和孔洞是导致断裂的根本原因。利用扫描电镜对触头焊料扩散连接区域进行线扫描发现,在较低温度下,只有Cu原子能够从焊料侧扩散至触头侧,Zn原子不能扩散。温度是影响扩散的最大因素,提高加热温度对原子扩散的作用比延长保温时间更显著,Cu原子和Zn原子扩散距离会随着温度的升高而增大,但Zn的扩散速度比Cu的扩散速度慢。Cu原子和Zn原子的扩散均会随着时间的延长,其浓度以指数关系衰减并很快收更多还原

【Abstract】 Electrical contact also called contact or contact junction, is the contact component of electric switch, instruments and meters and so on, which takes on the task of current on or off. Therefore its performance affects the running reliability of electric switch directly. Ag-W contact possesses good thermal and electrical conductivity, abradability, fusion welding resistance, and oxidation resistance. Ag-Cu-Zn solder based on Ag matrix has been widely used, with the characteristics of low melting point, good wetting property and caulking property, and high contact strength and so on. So the research on diffusion connection of contact solder has important theoretical meaning and practical application to enlarge the application of contact and solder.XRD, SEM, micro hardness instrument, and digital electric bridge are used to analyze the microscopic structure, electrical property, phase structure, fractography and the distribution of elements near the interface in this paper. It is also analyzed the effect of processing parameters such as heating temperature, time, and pressure on the electrical property and linear percentage in bonding pad area by used of orthogonal experiments. The processing parameters are optimized. According to Fick secondly law, error function and energy spectrum results are introduced to calculate the diffusion of Cu atom in Ag matrix when the contact solder is welded. The diffusion factor D0 and diffusion activation energy Q under the condition of this experiment are obtained, which are utilized to calculate the diffusion distance of Cu atom at a certain concentration, compared to actual measurement.The results indicate that in investigative test, when the heating temperature is lower than 700℃and little pressure, the diffusion ability of atom is deficiency and it cannot be diffused effectively. And in orthogonal test, the results are different when electrical resistivity and linear percentage of bonding interface are used as index mark. The ratio of electrical resistivity and linear percentage of bonding interface is 3:1 and the optimum processing parameters under the condition of this experiment are obtained. They are 675℃×2h, 0.09MPa and temperature is most important, pressure is second important, time is third important. The better properties both electrical resistivity and linear percentage are obtained by the optimum technology condition. The content of Ag mesosphere has great effect on the electrical property of contact solder when welding by pressure diffusion. The better the performance is, the more the Ag mesosphere is.更多还原