The interfacial diffusion behavior and microstructure evolution of Cu/Sn/Cu diffusion couple under electric field were in-situ observed by synchrotron radiation X-ray. The growth kinetics of Cu

6

Sn

5

was in-situ investigated under absence of current

bidirectional pulse current and direct current

respectively. The results indicate that the growth of Cu

6

Sn

5

at the Sn/Cu interface is significantly inhibited by the bidirectional pulsed electric field

which forces the precipitation of Cu

6

Sn

5

in the Sn solder in form of plates.DC field can effectively promote the growth of Cu

6

Sn

5

in Cu/Sn/Cu diffusion pairs accidentally from anode to cathode.