Improvement of the time dependent degradation characteristics of micro-soldered joints

研究了改善微焊点随时间退化的方法。主要研究结果如下：1)力学性能及室温时效特性：研究了不同冷却速度和室温时效对各种焊料力学性能的影响。锡-银、锡-锑和铅-银-锡焊料的抗拉强度随冷却速度的增加而增大，而锡铅焊料的抗拉强度随冷却速度的增加而降低。2)焊料合金的热疲劳：对锡-40Pb-0-25Bi焊料进行的热疲劳试验表明，含7.5-15%Bi的合金尽管固相线温度较低，但仍具有良好的抗热疲劳性能。室温下的应力松弛速率与各种焊料的热疲劳抗力有很好的对应关系，因此，应力松弛试验可以作为一种简单的方法来评估焊料的热疲劳性能。锡-7.5-15Bi、锡-25Ag-10Sb、铅-2.5Ag-1SN和锡-10Sb合金是制备高可靠焊点的候选合金。3)金属间化合物生长速率：研究了添加元素对不同二元铜合金焊点中金属间化合物生长的影响。在高强度铜铅框架合金中优选添加的元素是银、镁、锰、锌和锡。不应添加铁、磷、镍、硅、钛、钯、铝、钚和钴等元素，因为这些元素会因金属间化合物的生长而显著降低接头的可靠性。

Improvement of the time dependent degradation of micro-soldered joints was investigated. The obtained results are summarized as follows.1) Mechanical properties and room temperature aging characteristics: The effect of cooling rate and room temperature aging of various solder alloys on mechanical properties were studied. Sn-Ag, Sn-Sb and Pb-Ag-Sn solder alloys showed larger tensile strength with increasing cooling rate, on the other hand, in Sn-Pb solder the tensile strength was decreased with increasing the cooling rate. Precipitation of intermetallic compounds was found to be room temperature aging process.2) Thermal fatigue of solder alloys: Thermal fatigue test on Sn-40Pb-0-25Bi solder alloys revealed the alloy with 7.5- 15%Bi had good thermal fatigue resistance in spite of the lower solidus temperature. The stress relaxation rate at room temperature corresponded well with the thermal fatigue resistance of various solder alloys, therefore, the stress relaxation test could be used as a simple method to evaluate the thermal fatigue of solder alloys. Sn-7.5-15Bi, Sn-25Ag-10Sb, Pb-2.5Ag-1Sn and Sn-10Sb alloys are the candidates for making high reliable solder joints.3) Intermetallic compound growth rate: Effect of additional elements on the intermetallic compound growth was investigated on soldered various binary copper alloys. The elements preferable to be added in high strength copper lead frame alloys were silver, magnesium, manganese, zinc and tin. Such elements as iron, phosphorus, nickel, silicon, titanium, paradium, aluminum, plutinum and cobalt should not be added because the elements remarkably degraded the reliability of joints by the growth of intermetallic compounds.