The Reliability of Microalloyed Sn-Ag-Cu Solder Interconnections Under Cyclic Thermal and Mechanical Shock Loading

Abstract

In this study, the performance of three microalloyed Sn-Ag-Cu solder interconnection compositions (Sn-3.1Ag-0.52Cu, Sn-3.0Ag-0.52Cu-0.24Bi, and Sn-1.1Ag-0.52Cu-0.1Ni) was compared under mechanical shock loading (JESD22-B111 standard) and cyclic thermal loading (40 ± 125°C, 42 min cycle) conditions. In the drop tests, the component boards with the low-silver nickel-containing composition (Sn-Ag-Cu-Ni) showed the highest average number of drops-to-failure, while those with the bismuth-containing alloy (Sn-Ag-Cu-Bi) showed the lowest. Results of the thermal cycling tests showed that boards with Sn-Ag-Cu-Bi interconnections performed the best, while those with Sn-Ag-Cu-Ni performed the worst. Sn-Ag-Cu was placed in the middle in both tests. In this paper, we demonstrate that solder strength is an essential reliability factor and that higher strength can be beneficial for thermal cycling reliability but detrimental to drop reliability. We discuss these findings from the perspective of the microstructures and mechanical properties of the three solder interconnection compositions and, based on a comprehensive literature review, investigate how the differences in the solder compositions influence the mechanical properties of the interconnections and discuss how the differences are reflected in the failure mechanisms under both loading conditions.

Effect of Ni(P) Layer Thickness on Interface Reaction and Reliability of Ultrathin ENEPIG Surface Finish

“…In the drop test, when the inside of the solder ball is subjected to impact from the pad, the Sn crystal grains will form dislocations to absorb part of the impact energy, and the generation of dislocations will increase the tensile strength and yield strength of the solder itself. At the same time, the strain-strengthening mechanism [30] enables the solder to increase its own strength to be higher than the fracture strength of the IMC at a very high strain rate (1% s −1 to 10% s −1 ) in the drop test, resulting in failures that mostly occur in the brittle IMC layer, as shown in Figure 18. In the drop test, when the inside of the solder ball is subjected to impact from the pad, the Sn crystal grains will form dislocations to absorb part of the impact energy, and the generation of dislocations will increase the tensile strength and yield strength of the solder itself.…”

“…In the process of temperature cycling, the different CTE makes the volume change in each substance in the solder joint mismatched, which leads to stress and microcracks in the solder and promotes β-Sn grains recrystallize to form equiaxed grains [30], producing a continuous grain boundary network that provides a channel for the diffusion of microcracks. The crack extends with the volume expansion of microstructure, and finally leads to failure.…”

Research on Wiener Degradation Model and Failure Mechanism of Interconnect Solder Joints Under Random Vibration Load

“…Solder joints are a typical electronic chip connection structure, and solder joint failure has become one of the key issues that restrict the reliability of electronic equipment. Statistics show that vibration accounts for 20% of the environmental factors affecting the reliability of airborne electronic equipment [5], [6], and is the main environmental stress that causes solder joint failure. The solder joints are small, concealed in packaging, and few studies focus on the acquisition of solder joint state monitoring data and the representation of health status, while fewer systematic researches focus on the construction of degradation process models.…”