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

研究了微焊点随时间退化的改善方法。所得结果总结如下：1)力学性能和室温时效特性：研究了冷却速度和室温时效对各种钎料合金力学性能的影响。Sn-Ag、Sn-Sb和Pb-Ag-Sn钎料合金的抗拉强度随冷却速度的增加而增大，而Sn-Pb钎料的抗拉强度随冷却速度的增加而降低。金属间化合物的析出是室温时效过程。2)焊料合金的热疲劳性能：对Sn-40Pb-0-25Bi焊料合金进行热疲劳试验，结果表明：含铋7.5 ~ 15%的钎料合金固相温度较低，但具有较好的热疲劳性能。在室温下，应力松弛速率与各种钎料合金的热疲劳性能具有良好的对应关系，因此，应力松弛试验可作为评价钎料合金热疲劳性能的一种简便方法。Sn-7.5-15Bi、Sn-25Ag-10Sb、Pb-2.5Ag-1Sn和Sn-10Sb合金是制作高可靠焊点的备选材料。3)金属间化合物生长速率：研究了添加元素对不同类型二元铜合金金属间化合物生长的影响。高强度铜铅框架合金中较适宜添加的元素有银、镁、锰、锌和锡。不应添加铁、磷、镍、硅、钛、钯、铝、铂和钴等元素，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.