Study On The Process Of W/Cu Composites With Low CTE And High TC Used For Electronic Packaging

The heat of IC has risen severely along with its high integration scale, so urgent requirement of materials with high thermal conductivity (TC) and low coefficient of thermal expansion (CTE) which match to those of IC materials has been launched. For the tungsten-copper (W/Cu) metallic matrix composites (MMCs) having tailorable TC and CTE properties in certain range, this investigation aims at with discussion of composition design, preparing methods selection and process parameters optimization to develop the key technology of W/Cu composites materials processing.In this investigation, the preparation method selection and process parameters optimization of W-15Cu has been carried through. The process experiment results show an effective and feasible way to prepare W/Cu composites with low CTE and high TC, that is through pretreatment of Cu and W powders, addition of inducing Cu powders, forming W skeleton under high pressure, and infiltration of Cu into W skeleton under reductive atmosphere. Furthermore, through discussion of parameters, which can affect the proprieties and microstructure of W/Cu composites, the following main results can be obtained:1) The experiment results showed that the pretreatment of the powders, practical size of the W powder, addition of the inducing Cu powder, and the purity of the raw materials affect the pressing prosperities of W powders; the porosity amount and its distribution, infiltration temperatures play important role on the property of the W/Cu MMCs, while the infiltration time and heating/cooling rate have less effect on the property of W/Cu MMCs.2) The oxidation of raw materials can be decreased and the infiltration effectiveness can be enhanced in the reductive atmosphere; also the pressing properties ofskeleton and fluidity of copper liquid in the infiltration process can be improved with the addition of inducing copper powders, and the content of the inducing Cu was optimized to be about 2.5-5% to reach the best TC and CTE properties of the MMCs.3) The particle mean size and the particle size distribution of W powders have significant effect on the infiltration process. The experiment results reveal that, while particle size of W powder keep in range of 5-9 u m , the microstructure of MMCs can reach the high uniformly two constituent phases and with less defects ;4) The suitable temperature for the pre-sintering of W skeleton is about 1000癈 , and the temperature of infiltration is optimized to be about 1350 癈 .When W/Cu composites are prepared with above optimized process , and its CTE could be lower than 8 X 10~6/K, TC be about 176.6 W/(m 'K),and its density will be about 16. 1 5- 1 6. 58 g/cm3 , that can match the requirements of packaging and heat sink. The main research results of this paper can provide some certain technical support for industrialization and application of W/Cu composites used for electrical packaging and heat sink.