Basic Research On Preparation Process Of Cu/Invar Layered Composites

Electronic packaging materials need to have low coefficient of thermal expansion,good electrical conductivity and thermal conductivity,etc.A single material can hardly meet the required properties.Therefore,the Invar which has small thermal expansion coefficient,and the Cu which has good electrical conductivity and thermal conductivity,are combined together to prepare laminated composite material that can support and protect the normal operation of the electronic device chip.In this paper,the composite are based on two material differences,Invar/Cu/Invar and Cu/Invar/Cu were prepared by the hot rolling compound method and the liquid-solid-liquid sandwich casting method.and observed the state of interface bonding and mechanical properties testing,analysis of the forming mechanism.In the process of hot rolling experiment,according to the hot rolling method of Cu/steel to determine the process of hot rolling Cu/Invar,the process used in the Invar/Cu/Invar composite material,The analysis of SEM and EDS show,Invar/Cu/Invar is prepared by hot rolling method,the interface has no obvious gap under 2000 times,and exist about element diffusion 2?m layers.the plate bending and analysis of mechanical properties of compressive shear,the results show that the composite material interface has a strong binding force,the average shear strength of 178.3Mpa.Both showed that the composite interface had better results.Good binding force.Based on the twin-roll casting process,the liquid-solid-liquid sandwich casting method is raised to prepare Cu/Invar/Cu composites.Fluent fluid calculation software was used to establish two-dimensional steady state model of the casting zone.The distribution of the flow field and temperature field in the bath was simulated under different casting speeds,Invar preheating temperature,Invar strip thickness,and Cu liquid pouring temperature conditions.A prediction model for the location of the Kiss point and the average temperature at the exit of the casting zone was established.The results show,when the other three conditions are constant,The distribution of the flow field and the temperature field of the semi-solid phase area and the solid phase area can be improved by appropriately increasing the rotation speed of the roll,the preheating temperature of the Invar strip,the thickness of the Invar strip and the pouring temperature of the Cu liquid.as well as the temperature distribution of the composite interface,contributes to the smooth progress of the casting and rolling experiments.Based on the laboratory ?160×150mm two-roll caster,the double-side flow guiding device was designed and fabricated,the liquid-solid-liquid sandwich casting experimental platform was set up.Using the Fluent numerical simulation process parameters as a guide,the Cu/invar/Cu liquid-solid-liquid sandwich casting experiment was carried out.In the roll gap was 3mm,Invar strip thickness 0.5mm,without preheating of Invar strip,the roll speed was 3.46m/min,when the temperature of molten Cu was poured at 1170°C,Cu/Invar/Cu composite plate with a thickness of 3mm was successfully prepared.The tensile,bending,and peeling mechanical tests were performed.The results showed the combined interface has better binding force.The scanning of the tensile fractures was observed.The neck fractures were found on the fractures.Cu and Invar on both sides had good ability of coordinating deformation.The molten pool was cut,and the trend of macro grain orientation in the moten pool and the thickness of the Invar strip were observed after corrosion.The results show that the thickness of Cu grains gradually become smaller and the thickness of the invar is gradually reduced as the rolling proceeds.The SEM and EDS analysis of the composite interface of Cu/Invar/Cu composite tape showed that the composite interface between Invar and Cu had no pores,gaps,inclusions,etc.,and there was a diffusion layer of about 1 ?m at the interface.