本研究探討不同的Ni含量 (0.05、0.1、0.2、1.0wt%)添加對Sn-1.5Ag-0.7Cu(SAC157)低Ag無鉛銲料之影響。觀察剪切試驗、銲料硬度及150℃時效(25、100、225小時)前後對於界面IMC層成長、低週疲勞曲線之影響，以及分析低週疲勞的斷面及斷口，以評估銲料在低週疲勞的可靠度表現，並與無鉛銲料SAC157做比較。
隨著Ni的添加量增加，除了包圍β-Sn的網狀共晶組織之外，顆粒狀的(Cu,Ni)6Sn5析出也隨之增加；根據微硬度試驗顯示，Ni含量越高其網狀共晶組織與析出物越密集，銲料的硬度越高，而緻密的組織阻止了差排滑移，所以在剪切試驗中，與SAC157相比，四種含Ni銲料的剪切強度隨著Ni添加而明顯上升，但延性也隨之下降。
在低週疲勞試驗中，SAC-05Ni的壽命最佳，其次是SAC157。添加Ni後，銲料及IMC層的硬度皆提升，但SAC-05Ni和SAC-1Ni的銲料內部整體強度仍低於IMC層之強度，故在斷裂分析中，裂紋均在銲料內部發展，屬於內部破壞模式。當Ni的添加量越高，銲料的強度也會越高，其IMC層也越厚，使界面處產生應力不連續的現象，這將使裂紋在生成後從銲料內部往IMC層擴展，當裂紋與IMC層的細紋會合後，裂紋會快速發展，故屬於混和破斷模式的SAC-2Ni及SAC-10Ni的疲勞壽命會較低。在時效之後，銲料及IMC層均會發生相變化，除了SAC157外其餘四種銲料皆為銲點內部破斷模式。
綜合剪切試驗、界面層觀察、低週疲勞試驗及斷裂分析，當Ni添加量為0.05wt.%~0.1wt.%時即可顯著提升銲料之性質，擁有較佳之抗疲勞及抗熱的能力。

The effects of different Ni content (0.05, 0.1, 0.2, 1.0 wt.%) on the low Ag lead-
free solder of Sn-1.5Ag-0.7Cu (SAC157), including shear test, hardness, growth of IMC layer, low cycle fatigue and fracture morphology before and after the ageing of 150℃ (25, 100, 225 hours) were discussed and compared with the lead-free solder SAC157 in reliability performance in this study.
First, with the increase of Ni addition, both the (Cu,Ni)6Sn5 precipitation and
eutectic microstructure escalated. Therefore, in the hardness test, the hardness of the eutectic network microstructure and particles increased significantly. Besides, with higher hardness and intensive microstructure, shear strength of the solder was enhanced obviously by addition of 0.05wt.％. However, checked the elongation of solders in the shear test, the ductility decreased due to the dislocation slip was prevented by the compact eutectic network structure.
Second, in the low cycle fatigue test, the fatigue life of SAC-05Ni was the best,
and SAC157 followed. Although the Ni addition would make solder and IMC layer harder, the strength of SAC-05Ni and SAC-1Ni inside the solder was still lower than the IMC layer. Thus, in the fracture analysis, the development of cracks was generated in the solder which was an internal fracture mode. With the strength of solder and the thickness of IMC layer increasing as more Ni addition, the crack expanded from solder inside to the IMC layer because of the interface stress discontinuous phenomenon. After that, the crack from the solder combined with the crack which was between IMC and solder, and it would develop rapidly. Therefore, SAC-2Ni and SAC-10Ni were mixed fracture mode. Moreover, the solder and the IMC layers both changed in phase after ageing. In addition to SAC157, the other four Ni addition solders were all the internal fracture modes of solder joint.
Consequently, comprehensive shear test, IMC layer observation, low cycle fatigue
test and fracture analysis, it showed that the properties of solders could be improved
significantly with better fatigue and heat resistance when the Ni addition was
0.05wt.%~0.1wt.%.

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