Research on Creep Properties of Sn2.5Ag0.7CuXRE Lead-Free Soldered Joints for Surface Mount Technology

Abstract

Creep property of solder alloys is one of the important factors to effect the reliability of surface mount technology (SMT) soldered joints. The creep behavior and its rupture life of Sn2.5Ag0.7CuXRE lead-free soldered joints were separately investigated and predicted under constant temperature by a single shear lap creep specimen with a 1mm2 cross sectional area and finite element method (FEM) in this paper. Results show that the creep property of Sn2.5Ag0.7Cu0.1RE is superior to that of the commercial employed lead-free solder Sn3.8Ag0.7Cu and the creep rupture life of its soldered joints is 8.4 times more than that of Sn2.5Ag0.7Cu solder. The creep rupture life of Sn2.5Ag0.7CuXRE lead-free soldered joints indirectly predicted by FEM is better in accord with that of actual testing results, which are important to design the reliability of lead-free soldered joints for SMT.

The Morphology and Evolution of Cu₆Sn₅ at the Interface of Sn-2.5Ag-0.7Cu-0.1RE/Cu Solder Joint during the Isothermal Aging

“…3, it shows that there are lots of circular-like and paraboloid-like compound microaggregates, and most of these grains are contected 5-7 other grains in the Fig. 3, and these grains are determined as Cu 6 Sn 5 from the atom number proportion achieved by composition analysis and the literatures [9][10][11][12][13]. There are deeper grooves between the compound edge and the deepest groove is posited among the compound edge, this phenomenon maybe caused by the Kirkendall effect.…”

Effect of RE on Microstructure and Interfacial Reactions of SnAgCu Solder

“…Effect of RE on the interfacial reaction of SnAgCu solder joints. The intermetallic compound interfacial layer of soldered joints between Sn2.5Ag0.7CuxRE lead-free solder and copper substrate usually includes two parts [5,[8][9][10]: ε-Cu 3 Sn nearside the Cu substrate, which is not easy to find because of almost the same color with the Cu, and η-Cu 6 Sn 5 which can be easily found near the solder alloy. Fig.…”

“…But the commercial used SnAgCu solder alloy is expensive because of its Ag content generally greater than or equal to 3.0% [4][5][6] and its reliability properties needs to be further improved, which can limit its industrial applications in some extent. It has been proved feasible and useful to add tiny rare earth(RE) into the lead-free solder for improving or increasing the combination property of solder joints [5][6][7][8]. So the low Ag content Sn2.5Ag0.7Cu system solder alloy was prepared by adding RE element to decreasing the Ag content in the solder alloy, and the effect of RE content on microstructure and interfacial reactions of low Ag content SnAgCu solder was researched in the paper.…”

Effect of Ni on growing of intermetallic compound in interface of Sn2·5Ag0·7Cu0·1RE/Cu solder joint during aging

“…SnAgCu system lead free solder, which is considered as one of the most potential succedanea of SnPb solder, has been adopted now and is expected to be extensively used in the future due to its excellent comprehensive properties 2 – 4. The preceding studies reveal that adding 0·1 rare earth (RE) in the solder can enhance the physical properties and creep strength of SnAgCu solder alloys 5. In order to further improve the wettability, tensile strength and elongation of SnAgCuRE lead free solder, minor Ni has been added into the solder during manufacturing 6 – 8.…”