In situ study on the effect of thermomigration on intermetallic compounds growth in liquid-solid interfacial reaction

Abstract

Articles you may be interested inMassive spalling of Cu-Zn and Cu-Al intermetallic compounds at the interface between solders and Cu substrate during liquid state reaction J. Appl. Phys. 111, 074902 (2012); 10.1063/1.3699359 Blocking hillock and whisker growth by intermetallic compound formation in Sn-0.7Cu flip chip solder joints under electromigration Massive spalling of intermetallic compounds in solder-substrate reactions due to limited supply of the active element Early stages of soldering reactions J. Appl. Phys. 98, 063525 (2005); 10.1063/1.2058186Effect of 0.5 wt% Cu addition in Sn-3.5%Ag solder on the dissolution rate of Cu metallization Synchrotron radiation real-time imaging technology was carried out in situ to observe and characterize the effect of thermomigration on the growth behavior of interfacial intermetallic compounds (IMCs) in Cu/Sn/Cu solder joint during soldering. The thermomigration resulted in asymmetrical formation and growth of the interfacial IMCs. Cu 6 Sn 5 and Cu 3 Sn IMCs formed at the cold end and grew rapidly during the whole soldering process. However, only Cu 6 Sn 5 IMC formed at the hot end and remained relatively thin until solidification. The IMCs at the cold end were nearly seven times thicker than that at the hot end after solidification. The Cu dissolution at the cold end was significantly restrained, while that at the hot end was promoted, which supplied Cu atoms to diffuse toward the cold end under thermomigration to feed the rapid IMC growth. Moreover, the thermomigration also caused asymmetrical morphology of the interfacial IMCs at the cooling stage, i.e., the Cu 6 Sn 5 IMC at the cold end transformed into facet structure, while that at the hot end remained scallop-type. The asymmetrical growth behavior of the interfacial IMCs was analyzed from the view point of kinetics. V C 2014 AIP Publishing LLC. [http://dx.

Growth kinetics of Cu6Sn5 intermetallic compound at liquid-solid interfaces in Cu/Sn/Cu interconnects under temperature gradient

“…With prolonged reaction, however, Cu atoms from the substrate could hardly diffuse across the thickening Cu 6 Sn 5 layer against temperature gradient, resulting in a negligible . This was also proved by our previous in situ observations that the relative distance between the bubbles and the Cu substrate at the cold end remained unchanged, i.e., no dissolution of the Cu substrate occurred 12 . Consequently, the fast growth of the interfacial Cu 6 Sn 5 at the cold end only sustained by J TM .…”

“…However, due to the continuity of Cu concentration in liquid Sn, it is deduced that the concentration gradient of Cu was from the hot end to the cold end during reflow, i.e., the highest Cu concentration driven by temperature gradient should exist at the cold end before cooling. Since the precipitation of interfacial Cu 6 Sn 5 was quite fast during cooling 12 , the Cu concentration near the interfaces could markedly reduce before solidification, especially at the cold end. As a result, the Cu concentrations near the interfaces became lower than that in the middle of the solder layer after solidification.…”

“…Guo et al 11 found that the interfacial Cu 6 Sn 5 was much thicker at the cold end whereas the consumption of Cu was much faster at the hot end in Cu/Sn-2.5Ag/Cu solder joints during reflow at 260 °C on a hot plate, due to the rapid migration of Cu atoms under a simulated temperature gradient of 51 °C/cm. Qu et al 12 in situ studied the soldering interfacial reactions under a temperature gradient of 82.2 °C/cm at 350 °C using synchrotron radiation real-time imaging technology, and asymmetrical growth and morphology of interfacial IMCs between the cold and hot ends were clearly observed.…”

Effect of thermomigration on evolution of interfacial intermetallic compounds in Cu/Sn/Cu and Cu/Sn0.7Cu/Cu solder joints

“…They found the IMCs grew rapidly at the cold end but slowly at the hot end, which is responsible for fast migration of Cu atoms in molten solders. The same phenomenon was also observed in situ by Qu [11]. On the whole, effect of TM on the growth behavior of the interfacial IMCs in solder joints is relatively less.…”

Role of Intermetallics in Lead-Free Alloys

“…Guo et al [7] found that the interfacial Cu 6 Sn 5 was much thicker at the cold end, whereas the consumption of Cu was much faster at the hot end in Cu/Sn▬2.5Ag/ Cu solder joints during reflow at 260°C on a hot plate, due to the rapid migration of Cu atoms under a simulated temperature gradient of 51°C/cm. Qu et al [1,8] in situ studied the soldering interfacial reactions under a temperature gradient of 82.2°C/ cm at 350°C using synchrotron radiation real-time imaging technology, and asymmetrical growth and morphology of interfacial IMCs between the cold and hot ends were clearly observed.…”