The Study Of Microstructure And Properties Of Cu-Ni-Si-Fe Alloys

Cu-Ni-Si and Cu-Fe alloys were the two mainstream of lead frame materials. The characteristics of Cu-Ni-Si were high strength and low conductivity, while Cu-Fe was just the opposite. The advantages and disadvantages of two kinds of materials were very obvious. The development of science and technology put forward higher requirements on the performance of the lead frame materials. The study of lead frame materials still need continuous efforts.In order to obtain a better performance alloy, Cu-Ni-Si and Cu-Fe alloy, which are used for product lead frame, was synthesized. The mix materials of Fe(and P), Ni, Si and Cu for smelting and casting, then solid solution treatment at 850℃ for 1h and aging treatment at 450～550℃ for 1h～6h, after that, conductivity meter and hardness tester were used to test the alloys. Scanning electron microscope, energy spectronmeter and X-ray diffraction were used to observe and analyze the organization, composition and phase of alloys. The microstructure, electrical conductivity and hardness of both original Cu-Ni-Si alloy and the one which Fe(and P) was added, was studied. The influence of different content of Fe, Ni and Si as well as different proportion of Ni and Si was analyzed. The result turned out that,1. Strip deposition was observed in both cast Cu-Ni-Si alloy and Cu-Ni-Si-Fe alloy. Little precipitates remains after solid solution. Large particles precipitate was observed at the early stage when Cu-Ni-Si-Fe alloy aging at 550 ℃,then dissolved. 2. Fe had a negative influence on the conductivity of Cu-Ni-Si alloy. The more elements, the lower conductivity was. The less Ni and Si were, the better conductivity was. While the proportion of Ni and Si a little more than 4, the conductivity of Cu-Ni-Si alloy was higher than others. 3. Under cast and solid solution, Fe all played a reinforcing effect, but not the more strengthened Fe content the better. After solid solution, alloys had different degrees of hardness reduction. Fe did harm to the hardness of alloys after aging. Due to the diverse elements were added, and the thermal stability of Fe Ni Si compound which was precipitated during aging was poor, leading to the trend of hardness values is more complex. The more the addition amount of iron, the lower hardness of Cu-Ni-Si-Fe alloy after aging was. When the ratio of Ni and Si lower than 4, the hardness of the Cu-Ni-Si-Fe alloy was low. As the content of Ni, Si increasing, the hardness of the alloy increased, but the amplitude of the increase becomes gradually smaller. The hardness of Cu-Ni-Si-Fe alloy is lower than Cu-Ni-Si alloy.