Effect of Loading Stress on the Growth of Cn/Sn Intermetallic Compounds at High Temperatures

Abstract

Fabrication of reliable solder joints is crucial in microelectronics. In this study we tested solder joints under different loads and temperature-controlled conditions to investigate the effect of external stress on the growth of interfacial Cu/Sn intermetallic compounds (IMCs). Test specimens were prepared by electroplating a layer of Sn (25 μm thick) on a copper substrate. Samples were then clamped in a micromechanical testing apparatus integrated within a furnace. Experiments were performed by using load feedback control to ensure a constant load of 25, 50, or 100 MPa at a constant temperature of 200°C for periods of 24, 72, or 120 h. We then compared samples that underwent stress with those that did not to elucidate the effect of stress and aging on the formation of IMCs. Our results indicate that the presence of external stress affects the formation of Cu/Sn IMCs, including the speed of formation and the resulting thickness. Moreover, the micrographic structure of IMCs formed under external stress varied substantially depending on the amount of stress applied.