Fabrication And Property Study Of Diamond/Al Composites Used For Electronic Packaging

Diamond/Al composites with high thermal conductivity and low coefficient of thermal expansion that can be used as high-performance electronic packaging heat sink materials.However,of the composite material,high thermal conductivity mechanism is not clear,surface is very rough,novel coating element received little attention,which need further study.In this thesis,spark plasma sintering(SPS)method and gas pressure infiltration method were used to fabricate diamond/Al materials.Manufacturing process,microstructure and thermal properties of samples were studied.The main research results are as follows:Manufacturing process of diamond/Al composite materials by SPS method was optimized.Results show that diamond particles with Ti coating can improve interfacial bonding of samples.With matrix unmelted,as sintering temperature rises,stronger interfacial bonding and better properties of samples can be achieved.Increasing sintering pressure properly contributes to tight diamond particle bridging and stronger interfacial bonding,and better material properties are acquired.When holding time is too long,defects appear at the interface of samples,and poor properties are got.Composites fabricated by pure Al powders and diamond particles with Ti coating,MBD6 type and 100p.m in diameter,under the fabrication process,sintering temperature 630? sintering pressure 50MPa,holding time 5min,achieve thermal conductivity 514.7W/(m-K)and coefficient of thermal expansion 3.82 × 10-6/K.Compared with samples fabricated by SPS method,samples fabricated by gas pressure infiltration have higher thermal conductivity for diamond volume fraction is higher(-65%)and diamond particles can bridge with each other.Manufacturing process of diamond/Al composite materials by gas pressure infiltration method was optimized.Results show that,moderate amount of reaction product appear at the interface of samples,benificial to improving material properties,under infiltration temperature 750? and proper temperature and pressure holding time.Improved interfacial bonding and less interface can be achieved by coarse dianmond particles,hence better properties are acquired.Samples fabricated by AlSi9 alloy and diamond particles with no coating,MBD6 type and 165?m in diameter,infiltration temperature 750?,gas pressure 1.5MPa,holding time 25min,can acquire thermal conductivity 514.7W/(m-K)and coefficient of thermal expansion 3.82×10-6/K.It is also found that high-performace diamond/Al composite material can be prepared using low-grade diamond by optimized manufacturing process.Novel preparation process and mechanism of high thermal conductivity of diamond/Al samples were explored.Samples,the surface of which can be processed,were fabricated by SPS method and multilayer structure,however,manufacturing process need to be optimized for low thermal conductivity.Samples prepared by diamond particles with Nb coating and V coating have poor interfacial bonding and properties,which shows that Nb and V are unqualified coating elements.Properties of samples fabricated by gas pressure infiltration and vacuum squeeze casting were compared.Result shows that samples prepared by squeeze casting method have a few defects,but no selective interfacial bonding.Diamond particles bridge tightly with each other,providing rapid transfer channels for heat current,and the thermal conductivity is as high as 838.0W/(m-K),the contribution of diamond particles bridging to thermal conductivity is over 39.02%,which indicates that vacuum squeeze casting is a promising fabrication method.