Abstract: Through the study of electrochemical performance of several lead-free solders, it is clear that the influence of over-potential variety on lead-free solders must be taken into consideration when developing and applying them. It has been found that lead-free solders with Bi have lower over-potentials, while lead-free solders with In which attributes to the formation of InSn₄ in alloys have higher over-potentials compared with conventional Tin-Lead solders. Therefore,lead-free solders with Bi must be considered carefully, while lead-free solders with In have higher electrochemical safety when they are applied in welding electrical apparatus. So lead-free solders with In may have good prospects for electronic devices.