Abstract
Sn–Sb system solders and ENIG/ENEPIG surface finish layers are commonly used in electronic products. To illustrate the thermal reliability evaluation of such solder joints, we studied the interfacial microstructure and shear properties of Sn-4.5Sb-3.5Bi-0.1Ag/ENIG and Sn-4.5Sb-3.5Bi-0.1Ag/ENEPIG solder joints after aging at 150 °C for 250, 500 and 1000 h. The results show that the intermetallic compound of Sn-4.5Sb-3.5Bi-0.1Ag/ENIG interface was more continuous and uniform compared with that of Sn-4.5Sb-3.5Bi-0.1Ag/ENEPIG interface after reflow. The thickness of the interfacial intermetallic compounds of the former was significantly thinner than that of the latter before and after aging. With extension of aging time, the former interface was stable, while obvious voids appeared at the interface of the latter after 500 h aging and significant fracture occurred after 1000 h aging. The shear tests proved that shear strength of solder joints decreased with increasing aging time. For the Sn-4.5Sb-3.5Bi-0.1Ag/ENEPIG joint after 1000 h aging, the fracture mode is ductile-brittle mixed type, which means fracture could occur at the solder matrix or the solder/IMC interface. For other samples of these two types of joints, ductile fracture occurred inside of the solder. The Sn-4.5Sb-3.5Bi-0.1Ag/ENIG solder joint was thermally more reliable than Sn-4.5Sb-3.5Bi-0.1Ag/ENEPIG.
Highlights
Sn–Pb solder, as a connection material for electronic products, has always been favored by the electronics industry due to its excellent technological performance and low cost
The Sn-4.5Sb-3.5Bi-0.1Ag solder was printed on the electroless nickel-immersion gold (ENIG) or electroless nickel-electroless palladium-immersion gold (ENEPIG) substrate by using an automatic solder paste and reflowed at a peak temperature of 280 ◦C for a belt speed of 1m/min in a vacuum reflow machine (Vacm-0023, Germany) to complete the surface mounting process
A comparative analysis of interfacial microstructure and shear properties of Sn-4.5Sb-3.5Bi-0.1Ag solder with two kinds of surface finish layers (ENIG and ENEPIG) was conducted
Summary
Sn–Pb solder, as a connection material for electronic products, has always been favored by the electronics industry due to its excellent technological performance and low cost. Because of the toxicity of Pb, countries in succession set off a wave of “leadfree” after entering the 21st century. Electronic manufacturing is in a special stage of transition from lead-containing to lead-free soldering. Among the several leadfree solders, the ternary alloy Sn–Ag–Cu is regarded as the leading candidate system for reflow soldering. The lower melt point of the alloy limits its application in high temperature. The Sn–Sb system solders perform better in terms of cost and high temperature applicability [1]
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