The effect of substrate on the microstructure and creep of eutectic In-Sn

The creep behavior of Sn-3.0Ag-0.5Cu (SAC305), Sn-3.4Ag-1.0Cu-3.3Bi (SACBi), and Sn-3.4Ag-4.8Bi (SnAg-Bi, all wt.%) was studied in constant-stress creep tests from room temperature to 125°C. The alloys were tested in two microstructural conditions. As-cast alloys had a composite eutectic-primary Sn structure, while in aged alloys the eutectic regions were replaced by a continuous Sn matrix with coarsened intermetallic (Cu 6 Sn 5 and Ag 3 Sn) particles. After aging, Bi in SAC-Bi and SnAg-Bi was found as precipitates at grain boundaries and grain interiors. The creep resistance of of-cast SAC305 was higher than that of as-cast Bi-containing alloys, but after aging the SAC305 had the lowest creep resistance. The creep strain rates in SAC-Bi and SnAg-Bi were much less affected by aging. The apparent activation energy for creep was also changed more for SAC305 than for the other two alloys. The creep behavior of SAC-Bi and SnAg-Bi can be understood by considering the solubility of Bi in Sn. The difference in creep behavior between as-cast and aged SAC-Bi is greatly reduced when room-temperature test results are excluded from analysis. This suggests that the strongest influence on creep in these alloys is due to Bi solute interaction with moving dislocations during deformation.

Section: Discussionmentioning

confidence: 90%

Creep Behavior of Bi-Containing Lead-Free Solder Alloys

Witkin

2011

“…[1][2][3][4][5][6][7] Roming et al 1 dipped Cu into In-50Sn molten solder and then aged the specimens in air at the temperatures ranging from 60°C to 110°C. Two intermetallic compounds of Cu 2 (Sn,In) and Cu 2 In 3 Sn were found at the In-Sn/Cu interface.…”

Section: Introductionmentioning

confidence: 99%

Phase identification and growth kinetics of the intermetallic compounds formed during in-49Sn/Cu soldering reactions

Chuang

Chang

et al. 2002

For the application of In-49Sn solder in bonding recycled-sputtering targets to Cu back plates, the intermetallic compounds formed at the In-49Sn/Cu interface are investigated. Scanning electron microscopy (SEM) observations show that the interfacial intermetallics consist of a planar layer preceded by an elongated scalloped structure. Electron-probe microanalyzer analyses indicate that the chemical compositions of the planar layer and the scalloped structure are Cu 74.8 In 12.2 Sn 13.0 and Cu 56.2 In 20.1 Sn 23.7 , respectively, which correspond to the ε-Cu 3 (In,Sn) and -Cu 6 (In,Sn) 5 phases. Kinetics analyses show that the growth of both intermetallic compounds is diffusion controlled. The activation energies for the growth of -and ε-intermetallics are calculated to be 28.9 kJ/mol and 186.1 kJ/mol. Furthermore, the formation mechanism of intermetallic compounds during the In-49Sn/Cu soldering reaction is clarified by marking the original interface with a Ta-thin film. Wetting tests are also performed, which reveal that the contact angles of liquid In-49Sn drops on Cu substrates decline to an equilibrium value of 25°C.

“…7, along with steady-state creep data for pure In on a Cr-Ni-Pd substrate, 8 InSn eutectic on a Ni substrate, 9 and Bi-Sn eutectic 4,10,11 at room temperature. The similarity of the In-Ag creep rates to those of In is not surprising.…”

Section: Resultsmentioning

confidence: 99%

The creep behavior of In-Ag eutectic solder joints

Reynolds

Kang

Morris

1999

Self Cite

The addition of 3 wt.% Ag to In results in a eutectic composition with improved mechanical properties while only slightly lowering the melting temperature. Steady-state creep properties of In-Ag eutectic solder joints have been measured using constant load tests at 0, 30, 60, and 90°C. Constitutive equations are derived to describe the creep behavior. The data are well represented by an equation of the form proposed by Dorn: a power-law equation applies to each independent creep mechanism. Two parallel mechanisms were observed for the In-Ag eutectic joints. The high-stress mechanism is a bulk mechanism with a thermal dependence dominated by the thermal dependence of creep in the Inrich matrix. The low-stress mechanism is a grain boundary mechanism. Results of this work are discussed with regard to creep behavior of typical eutectic systems.