摘要由于铅的对人体具有毒性，因此急需研发新型无铅钎料来代替传统钎料。其中，Sn-Zn钎料具有和Sn-Pb钎料相似的熔点，且其原料丰富，价格低廉，是目前最有前景的合金之一。然而，Zn元素的存在使得该钎料体系的抗氧化性和抗腐蚀性弱，润湿性较差，使其无法广泛应用在实际生产当中。为了解决Sn-Zn钎料存在的问题，本文通过在钎料中添加稀土元素Pr来提高其性能，探究Pr对钎料组织与性能的影响规律。87881

通过试验发现：加入微量稀土元素Pr的Sn-Zn钎料的润湿性能和抗氧化性能得到较大的改善。稀土元素Pr的添加能够降低熔融钎料的表面张力，从而减少Z你的氧化物的产生，提高了钎料的润湿性能。然而稀土元素Pr也易氧化，当Pr的添加量超过0。1wt。%时，Pr发生氧化，反而恶化钎料的润湿性能。根据试验结果，稀土元素Pr的最佳含量为0。08wt。%。

稀土元素Pr添加后较大的提高了焊点的剪切力和拉伸力，在Pr含量为0。04wt。%时，焊点的剪切力增加达28。7%；而在Pr含量为0。08wt。%时，焊点的拉伸力增加达38%。当Pr添加过量后，焊点在金属间化合物与钎料界面附近断裂，焊点力学性能反而下降。 

钎料基体中的富Zn相在稀土元素Pr加入后细化，从而使得界面IMC层的生长速度减慢，并且Cu-Sn化合物生成受到抑制，界面组织变得更为稳定，焊点的可靠性得到提升；但是当Pr的添加量达到0。25wt。%时，大量易被氧化的Sn-Pr化合物在界面生成，使得钎料中锡须大量生长。总的来说，在Sn-Zn钎料中稀土元素Pr的最佳添加量为0。08wt。%，此时焊点的综合性能最佳。

毕业论文关键词  无铅钎料 润湿性能 力学性能 界面 锡须

毕业设计说明书外文摘要

Title    Effect of Pr on the reliability of Sn-Zn Lead-free Solder                     

Abstract Due to the toxicity of Pb ,a new type lead-free solder with excellent performance and low cost is needed to replace the traditional solder。Sn-Zn solder having a similar melting point to Sn-Pb solder and its low prices, is one of the most promising alloys。 However, the presence of Zn makes the resistance to oxidation and corrosion resistance weak and wettability poor。 it can not be widely used in the actual production。In order to solve the problems of Sn-Zn solder and explore the influence of Pr on microstructure and properties of solder in this article ,we add infinitesimal elements Pr to improve its performance,。

According to the experiment,with infinitesimal elements Pr,Sn-Zn solder’s wettability and oxidation resistance is greatly improved。Adding the rare earth element Pr is capable of reducing the surface tension of the molten solder and educing the generation of oxides of Zn, and finally improving solder wettability。 However, the rare earth element Pr is also easily oxidized which will worsen the solder wettability, when the addition amount Pr exceeds 0。1wt。%。 According to the results, the optimum content of the rare earth element Pr is 0。08wt。%。

After the addition of rare earth elements Pr greatly improved shear strength and tensile strength of solder joints in Pr content of 0。04wt%, the solder joint shear force increase 28。7%; in Pr content of 0。08wt。 %, the tensile strength of solder joints increase 38%。 When Pr was added excessively,the mechanical properties of solder joints decreased。

Solder matrix phase of Zn-rich is refined after rare earth element Pr is added , which slows the growth rate of IMC layer and the Cu-Sn compound。Besides,the interface tissue becomes more stable and the reliability of the solder joints are raised; but when the addition amount Pr reaches 0。25wt%, a large number of Sn-Pr compound easily oxidized generate at the interface which make a large number of brazing alloy whisker generated。 In general, the optimal dosage of Pr in the Sn-9Zn solder is 0。08wt。%  in which case the joints have the best performance。