Study Of Oxide Dispersion Copper For IC Lead Frame Material Prepared By Internal Oxidation Method With Mixed Rare Earth-Cu-Al Alloy

Al₂O₃ dispersion strengthened copper base composite is suitable for IC lead frame materials with high electrical conductivities, high strength and high thermal at room temperate as well as at elevated temperature. The Al₂O₃ dispersion strengthened copper base composite has been widely used as weld electrode, electronic vacuum devices, and lead frame etc. Among the various fabrication methods of the composite, the internal oxidation method is a better way to fabricate Cu-Al composites with excellent properties. The shortcomings of the internal oxidation method is due to the complex process, long production cycle and high cost, etc.The internal oxidations of the Cu-Al alloy and Cu-Al-RE alloy were carried out with the commercial nitrogen gas medium in a tube-type resistance furnace. The process was relative simple. In this paper, the effects of internal oxidizing temperature, time and additive of the mixed rare earth (Ce+Y) on the Cu-Al alloy internal oxidation kinetics were investigated. The electrical conductivities and tensile strength of the Cu-Al₂O₃ composite and Cu-Al₂O₃/(Ce+Y) composite prepared by the simplified internal oxidation were investigated. The microstructure of the composites was observed by SEM, TEM and HRTEM respectively. The effects of adding rare earth elements of (Ce+Y) on the performance and microstructure of the Cu-Al₂O₃ composite were investigated. The change rules of microhardness and electrical conductivity, tensile strength with different cold deformations were determined. The relationship between the microhardness of the Cu-Al₂O₃ and Cu-Al₂O₃/(Ce+Y) composite and the annealing temperature was studied. The behaviors of the recovery and recrystallization of the Cu-Al₂O₃ composite and Cu-Al₂O₃/(Ce+Y) composite at high temperature were discussed, which is benefit to the preparement and application of the Al₂O₃ dispersion strengthened copper base composites.The results show that the addition amount of rare earth elements of (Ce+Y) in Cu- Al alloy can accelerate the internal oxidation process. The internal oxidation layer of Cu-Al-0.1(Ce+Y) increases by 60% at 950oC×2h. The Cu-Al₂O₃ composite and Cu-Al₂O₃/RE composite were succefully prepared by the simplified Cu-Al alloy internal oxidation process. The HRTEM and TEM observation and calculations show that the nanometerγ-Al₂O₃ particles distributed in the matrix of the Cu-Al₂O₃/RE composite with the size of 5nm¹0nm and the interspace of 10nm³0nm. The misfit of theγ-Al₂O₃ and matrix keeps coherent and or half-coherent.The addition of rare earth elements (Ce+Y) in Cu-Al alloy increases the microhardness, tensile strength and softening temperature after the internal oxidation. The softening temperature is about 800oC of the composite. The addition of rare earth elements (Ce+Y) in Cu-Al alloy increases the softening temperature by 100oC. The softening temperature of Cu-Al₂O₃ composite changed slowly after cold deformation. After the internal oxidation at 950oC for 2h and the cold deformation of 80%, the microhardness and the tensile strength of Cu-Al₂O₃ composite increase 45HV and 168MPa, respectively. The microhardness and the tensile strength are about 135HV and 390MPa, respectively.The results show that the Cu-Al₂O₃/0.05(Ce+Y) composite prepared by internal oxidation posseses the optimum comprehensive properties. The microhardness and tensile strength of the Cu-Al₂O₃/0.05(Ce+Y) composite reach 138HV and 407MPa after 80% cold deformation, respectively.