Rolling Technology And Properties Of Copper-Steel Thin Composite Strip With High Strength And High Conductivity

In this paper,Q345 steel strip and T2 pure copper are used as the base material and cladding material respectively.The cold roll bonding process of copper/steel/copper composite strip is mainly studied,and the composite thin strip with good bonding strength,mechanical properties and electrical conductivity is obtained.The main work and research results are as follows:(1)To the lead frame copper in the electronic industries as the target product,Cu/Steel composite strip with the thickness of 0.08mm is obtained by cold roll bonding process.The tensile strength is 500MPa,and the conductivity is 76.6%IACS.Both of the two major are better than C194,which is the most favorable material for the lead frame copper.The minimum thickness of the composite reached 0.04mm,breaking the lowest limit of the thickness of the lead frame copper,overcoming the difficulties that domestic industries cannot produce thin gauge lead frame independently.(2)When the composite strip is further rolled after intermediate annealing,tensile strength enhances with the increase of the deformation amount due to the work hardening.However,when the thickness is reduced below 0.08mm,tensile strength decreases with the increase of the deformation.The conductivity of the composite strip decreases with the increase of the annealing temperature.With the increase of the annealing temperature,tensile strength of the composite strip decreases,and the conductivity increases gradually.The tensile strength increases with the thickness of the steel layer in the composite strip,and the conductivity increases with the thickness of the copper layer in the composite strip.(3)With the increase of annealing temperature,the bending performance of the composite strip is gradually improved.After intermediate annealing,the cold rolled composite strip was rolled continuouly,and with the decrease of thickness,the bonding strength of the composite strip is significantly enhanced and the plastic forming ability is favorable.After annealed at 500? for 2h,the composite strip with thickness of 0.1mm can be bended for 325 times repeatedly.(4)With a surface treatment of steel brush polishing,at the reduction rate of 75%,the bonding effect of copper and steel composite is favorable.A greater Cu/Steel thickness ratio makes the composite strip to be more easily compounded,meanwhile making the bonding strength stronger.The bonding strength of the composite strip depends on two kinds of energy produced at the interface.One is the mechanical meshing energy produced by the physical bonding during the cold rolling process,and the other is the chemical bonding energy generated from the interfacial atomic diffusion during annealing.