MnO2掺杂的KNN基无铅压电陶瓷的制备及性能

采用传统的固相反应法制备了(1-x)(Na0.65K0.35)0.94Li0.06NbO3-xmol%MnO2无铅压电陶瓷,研究了Mn的掺杂对陶瓷压电和介电性能的影响.实验结果表明,所有的样品都显示出四方相钙钛矿结构.材料的平均晶粒尺寸随着MnO2掺杂量的增加逐渐变大.MnO2的添加使样品的压电常数d33、平面机电耦合系数kp、机械品质因数Qm、介电损耗tanδ和相对密度均得到明显改善.当MnO2的掺杂量为0.50mol%的时候,样品的性能达到最佳:d33=144pC/N,kp=42%,tanδ=2.4%,Qm=168.以上数据表明,该陶瓷材料是一种极具应用潜力的无铅压电陶瓷材料.     

无铅易切削黄铜的发展现状及发展方向

叙述了国内外无铅易切削黄铜的发展和研究现状,对以其他更环保的元素替代铅的研究进行了讨论,从切削性、力学性能、热锻性和耐腐蚀性能方面总结了新型易切削黄铜的优缺点。对当前已经应用的无铅黄铜,特别是铋黄铜存在的问题进行了总结,提出了铋黄铜改性的研究方法以及发展方向。     

小尺度薄型封装焊点失效机理和可靠性设计

通过实验研究了印刷电路板（print circuit board,PCB）设计对小尺寸薄型封装（thin small outline package,TSOP）焊点可靠性的影响.实验制作了包含引脚焊盘的长度、焊盘的表面处理方式及背靠背的双面贴装偏移量3种设计参数的可靠性测试板,并采用表面贴装工艺（surface mount technology,SMT）将TSOP器件焊接到测试板上;经-40～85 ℃的高低温循环试验后,收集了TSOP引脚焊点裂纹的生长数据;讨论了焊点失效的机理,相应考虑了2种可靠性判断准则,并对各参数条件下的裂纹数据进行比较.结果表明,长尺寸焊盘、有机保焊膜（organic solderability preservatives,OSP）及不对称的两面布置方式有助于提高TSOP引脚的焊点可靠性.     

Optimization of mechanical properties of Sn-3.8Ag-0.7Cu alloys by the additions of Bi,In and Ti

Bi, In and Ti were added to Sn-3.8Ag-0.7Cu (SAC387) solder alloy to optimize the mechanical performance. The alloying effects of Bi, In and Ti on the microstructure, thermal and mechanical properties of SAC387 based solder alloys were investigated. The results demonstrate that adding 3.5 ?wt % of Bi could refine the microstructure, optimize the thermal properties, and improve the tensile strength. Meanwhile, the ductility of the solder alloys reduced evidently. Adding 2.8 ?wt % of In into SAC387–3.5 ?wt %Bi alloy could increase both the strength and ductility, which is attributed to the beneficial effect of In addition, as adding In could improve the solubility of Bi in the β-Sn matrix. Meanwhile, the melting point was reduced, and the wettability improved with the addition of In. Introducing amounts of Ti into SAC387–3.5 ?wt % Bi-2.8 ?wt % In alloy could further increase the strength. However, the ductility was significantly reduced when 0.8 ?wt % of Ti was added due to the formation of the coarse Ti₂Sn₃ phase. The undercooling was remarkably reduced with the addition of Ti. The nanoindentation tests demonstrate that the hardness increased mainly due to the hardening effect of the Bi addition. Among all the samples prepared, alloy SAC387–3.5 ?wt % Bi exhibited the highest creep resistance at the ambient temperature. Further adding In and Ti into SAC387–3.5 ?wt % Bi alloys reduced the creep resistance of the solder alloys. The mechanism associated with the different mechanical responses is also discussed in this study.