利用DSC、微焊点强度测试仪、SEM、EDS及XRD,研究了Sn0.3Ag0.7Cu、Sn1.0Ag0.5Cu和Sn3.0Ag0.5Cu钎料的熔化特性、润湿性、力学性能、显微组织及相种类。通过TL-1000型高低温循环试验箱测试了-55~125 ℃循环条件下Sn-Ag-Cu焊点的界面层变化。结果表明,随着Ag含量的增加,钎料的熔点变化不大,钎料的润湿角显著降低,N2氛围条件下,3种钎料的润湿性均出现明显的提高。此外,3种焊点的力学性能也随着Ag含量的增加显著提高。Sn0.3Ag0.7Cu、Sn1.0Ag0.5Cu焊点的基体组织存在着少量的Ag3Sn和大颗粒Cu6Sn5化合物,且分布杂乱,Sn3.0Ag0.5Cu焊点的基体组织则相对较为均匀,这也是Sn0.3Ag0.7Cu、Sn1.0Ag0.5Cu焊点的力学性能低于Sn3.0Ag0.5Cu的主要原因。对焊点进行热循环处理,发现3种焊点界面金属间化合物的厚度明显增加,界面层的形貌也由原来扇贝状向层状转化。
SnAgCu solder alloys, such as Sn3.0Ag0.5Cu, Sn3.8Ag0.7Cu and Sn3.9Ag0.6Cu, are widely used for consumer electronics due to their good wettability, high mechanical properties and excellent thermal fatigue reliability. However, the high Ag content in SnAgCu solder can bring about a relatively high cost and poor drop impact reliability because of the formations of thicker brittle Ag3Sn compound during soldering. Therefore, the development of low Ag content SnAgCu solders to satisfy the requirements of electronic production has become a hot topic in this field. In this work, the effects of Sn0.3Ag0.7Cu, Sn1.0Ag0.5Cu and Sn3.0Ag0.5Cu solder on the melting character, wettability, mechanical properties and microstructures, phase composition were investigated by DSC, micro-joint strength tester, SEM, EDS and XRD. Under -55~125 ℃ cyclic conditions, the interfacial layer change of Sn-Ag-Cu solder joints was measured by TL-1000 high and low temperature test chamber. The results showed that, with the Ag content increased, the melting point was not changed, the wetting angle significantly decreased. And the wettability of three solders was improved under N2 atmosphere. Moreover, the mechanical properties of three solder joints were enhanced with the increase of Ag content. The matrix structure of Sn0.3Ag0.7Cu and Sn1.0Ag0.5Cu solder joint have a small amount of Ag3Sn and large Cu6Sn5 particles, and the distribution of particles were disordered. However, the matrix structure of Sn3.0Ag0.5Cu solder joint was obviously uniform. This is the reason that the mechanical properties of Sn0.3Ag0.7Cu and Sn1.0Ag0.5Cu solder joints were lower than that of Sn3.0Ag0.5Cu. In addition, the solder joints were subjected to a thermal cycling reliability test, it was found that the thickness of intermetallic compounds (IMCs) increased, and the morphology of IMCs was gradually changed from scallop-like to planar-like.
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