As support materials of integrated circuits, lead frame is the key structural components to the formation of the electrical circuits, played a role in the internal and external wire connections. As one of the commonly used lead frames at present, 5-8 mu m copper plating layer above of FeNi42 alloy often been found deep red color after chip welding. Aiming at this phenomenon, this paper collected large color change point for a long time, adopted the method of scanning electron microscope (SEM) and energy dispersal spectroscopy (EDS) analysis, classified the discoloration point on the basis of before work, and conducted laboratory simulation aimed at a kind of discoloration caused by a special petal-shaped clusters morphology. Result shows that the alkali and (CN) - in electroplating solution can absorb carbon dioxide to produce carbonate crystals coating on the surface of the crystal, which shows the deep red color point on the macro after the process of high temperature welding chip.