Preparation And Properties Of W-SiC_P/Cu Graded Composites By Tape Casting

W-Cu gradient composites showed excellent electrical conductivity and thermal conductivity,so it could be widely used in electronic packaging materials.However the thermal expansion coefficient of W differed from Cu,thermal stress existed in the W-Cu gradient composites and could limit widely use in the field of hot assembly materials.In order to reduce the thermal stress of W-Cu gradient composites,low thermal expansion coefficient SiC was introduced to fabricate W-SiC_P/Cu gradient composites with good parallelism.Since slight variance on thermal expansion coefficient between SiC and W,the thermal expansion coefficient of each layer could be closer by adjusting the content of W and SiC.Thermal stress of W-SiC_P/Cu gradient materials cloud be eliminated theoretically through this methodLow porosity,good parallelism and precise thickness W-SiC_P/Cu gradient composites were fabricated through tape casting and vacuum hot pressing sintering.The affect of tape casting procedure,degrease temperature and sintering process on micro-structure and phase of W-SiC_P/Cu composites were discussed.Then characterize the flatness and micro-structure of the W-SiC_P/Cu gradient composites detailedly.By adjusting the content of PVB and plasticizer,we successfully fabricated W-SiC_P/Cu slurry with different W contents with good time stability.The viscosity was below 800mPa·s.The blade gap was 50?m,the speed of baseband was 2.5mm/s and the heating temperature was 25?,under these conditions green tapes was fabricated with no obvious settlement,uniform structure and thickness about25-40?m.W-SiC_P/Cu composites degreased under high temperature H₂ process and discuss influence of H₂ treatment.By using CHONS analysis,the carbon content of the powder decreased about 1.2 wt%after H₂ treatment.The W-SiC_P/Cu homogeneous composites with low porosity and uniform micro-structure were obtained through vacuum hot press sintering.The highest porosity of the prepared W-SiC_P/Cu homogeneous composites was 0.52%when sintered at 900?-200MPa-2h.XRD results showed that when the content of W was 10vol%,composites contained W,Cu,SiC,Cu₅Si and WC_1-X five phases.W-SiC_P/Cu composites showed excellent hardness by tape casting,The Vickers hardness of composites with different W contents increased initially and then decreased,when W content was 50vol%composites reach a maximum of 614.34HV.The coefficients of thermal expansion of W-SiC_P/Cu composites were almost unchanged with different W contents,which were about 11.8×10^-6/K,the value was in accordance with mixed model.Finally,through secondary binder removal and vacuum hot press sintering,W-SiC_P/Cu composites were fabricated with W content ranging from 0⁶0vol%show excellent parallelism between layers.The thickness of W-SiC_P/Cu gradient composites can be precisely controlled and the thickness error was only 0.75%.The microstructure and OM diagrams show obvious gradient structure of composites and the interfacial layer transition was uniform.The bending deformation of W-SiC_P/Cu gradient composites was slight and the flatness of W-Cu surface was 9.08?m,the flatness of Cu-SiC surface was 8.89?m.Ultrasonic nondestructive tests show that there were no defects or cracks in the W-SiC_P/Cu gradient composites,and the parallelism between the layers was excellent.