The Study Of The Effect Of Sb On Sn-0.7Cu Lead-free Solder

Lead is harmful both to environment and human, so that products that contain lead are prohibited to be used by some countries through legislation. New lead-free solders have been used in industry. The effects of Sb on microstructure, melting characteristic, shear strength and spreading wettability of Sn-0.7Cu lead-free solder are studied. The effects of Sb on interface of Sn-0.7Cu/Cu and the pattern of IMC after aging are also studied.The result shows that in all the Sn-0.7Cu-XSb solders, there are no low-temperature eutectic peak, which indicated that no low-temperature eutectic phase is formed while small amount of Sb is added into Sn-0.7Cu solder and reliable soldered jointis can be formed. The melting point is lifted as Sb is added into the solders. But the melting point changed a little. After adding Sb into the solder the Cu6Sn5 phase is refined, which is benefit to the improvement of solders mechanical property. The spreading wettability is descended when Sb is added into the solder, but when Sb is less than 0.75wt%, spreading wettability is advanced as the mount of Sb is increased, when the mount of Sb larger than 0.75wt%, the spreading area becomes small. The shear strength of Sn-0.7Cu solder is enhanced after Sb is added into the solder. With the mount of Sb is increased the shear strength of the solder is enhanced, when the solder contains 1.0wt% Sb, the shear strength reaches to 29.14MPa which is larger than other solders.The effects of Sb on soldering interface are studied, the Sn-0.7Cu's IMC is thicker than the Sn-0.7Cu–XSb solders after soldering. When Sn-0.7Cu solder contains 0.5wt% Sb, the pattern of IMC changes obviously: scalloplike IMC becomes smooth and the thickness of IMC becomes small and big prismatical Cu6Sn5 is avoided; the growth of IMC is inhibited and the grain is refined. The spiece of IMC isn't changed when Sb is added into Sn-0.7Cu solder. After aging 100 hours at 150℃the Cu3Sn phase is formed between Cu6Sn5 phase. and Cu substrate; some.voids are formed on the IMC After aging 500 hours the Cu3Sn phase becomes more obvious. A lot of voids are also founded at the IMC and at some place of IMC microcrack is formed because some voids contect together. This will have much influence on spot weld's reliability. The IMC becomes thicker as the aging time increased. The Sn-0.7Cu's IMC is thicker than the Sn-0.7Cu–XSb solders both after aging 100h and after aging 500h.