Impression creep of a Sn60Pb40 alloy: the effect of electric current

Abstract

Solder joints provide electrical and mechanical interconnections in microelectronic circuits and devices. The mechanical behaviour of the solder joints plays an important role in determining the reliability and lifetime of microelectronic devices. Using the impression technique, the effect of electric current on the creep deformation of a Sn60Pb40 alloy was studied in the temperature range of 323–383 K and under the punching stress of 9.7–110 MPa. During the test, a constant dc electric current was passed through the sample, which introduced electromechanical interaction. A steady state creep was observed under the action of the dc electric current and punching stress. The steady state impression velocity increased with the increase in the electric current for the same punching stress, and the stress dependence of the impression velocity followed Eyring's relation. The apparent activation energy decreased linearly with the square of the electric current due to the increase in atomic mobility driven by the electric current.

Effect of electric current on the creep deformation of lead

“…The temperature rise increased with the increase in electric current under the same chamber temperature, the same as that for the electrocontact heating of tin and Sn60Pb40 alloy. For the same electric current and the chamber temperature not larger than 383 K, the temperature rise increased with the chamber temperature in contrast to the electrocontact heating of tin and Sn60Pb40 alloy which showed the temperature rise decreased with the chamber temperature [11]. This result is likely due to the formation of a thick oxidation layer on the Pb surface, which increased local resistance and the heat released through Joule heating.…”

“…An electric circuit was constructed to allow an electric current to pass through the Pb-sample from the punch. For detailed information see the schematic of the electric circuit designed by Chen and Yang [4,11]. The flat-ended, cylindrical punch used for the impression test was made of tool steel and had a diameter of 300 m. Electrocontact heating tests were first performed.…”

“…As a result, the punching stress (the load divided by the cross-sectional area of the punch) remains constant during the test, similar to the compression creep test of constant stress. Recently, Chen and Yang [4,11,12] had applied the impression test technique to study the electrocontact heating of a Sn60Pb40 alloy and the effect of electrical-thermal-mechanical interaction on the creep behavior of tin and Sn60Pb40 alloy. They observed strong effect of electric current on the local time-dependent plastic deformation of tin and Sn60Pb40 alloy.…”

Effect of DC Current on the Creep Deformation of Tin

“…An electric circuit was constructed to allow electric current to pass through the tin sample from the punch, which was the same as that designed by Chen and Yang. 8,9 The punch and the sample were insulated from the holding fixture, using insulation layers. The flat-ended, cylindrical punch used for the impression creep was made of tool steel and had a diameter of 400 lm.…”

“…They also evaluated the effect of electric current on the impression creep of the 60Sn-40Pb alloy. 9 Tu and coworkers 10,11 found that passing an electric current at elevated temperature through electronic interconnects can create voids at the cathode side and cause a ductile-to-brittle transition of the electronic interconnects.…”