Effect Of SiC/Si Particle Size On Properties Of G/Al Electronic Packaging Composites

With the rapid development of network communication,the unit heat generating power of electronic components increases,which requires heat conducting materials to have higher heat dissipation capacity.Traditional metal heat-conducting materials(such as copper,aluminum,etc.)have gradually failed to meet the use requirements,and it is extremely urgent to develop new heat-conducting materials.Scaled graphite has the advantages of high thermal conductivity and low thermal expansion coeffici ent,and is considered as an ideal thermal conductive filler.Because of its adjustable thermal expansion coefficient and excellent thermal conductivity,the flake graphite/aluminum matrix composite has become a very promising thermal conductive composite in contemporary thermal management system.However,the flexural strength of the flake graphite/aluminum composite prepared at present has been difficult to meet the application requirements of the material,which leads to the failure of commercial application of this composite.In this paper,silicon carbide particles and silicon powder with different particle sizes were added into natural flake graphite/aluminum composites with directional arrangement structure by hot pressing sintering technology in a vacuum unidirectional hot pressing furnace,and the effects of particle sizes of silicon carbide particles and silicon powder on flexural strength,thermal conductivity,thermal expansion coefficient,thermal stability and friction coefficient of the composites were studied.The experimental results show that in Si C _p/flake graphite/aluminum composites prepared by Si C_p with different particle sizes:(1)when the particle size of Si C_p is 150?m,the maximum bending strength is 109.9 MPa in the plane perpendicular to the hot pressing direction(XY plane)and 45.2 Mpa;in the plane parallel to the hot pressing direction(Z plane);(2)When heated from 20?to 100?,Si C_p/flake graphite/aluminum composite with particle size of 15?m has the maximum thermal conductivity of 375W/(m k);(3)The thermal expansion coefficient of the material at room temperature is15.2×10^-6 m/K,which is much smaller than that of pure aluminum at room temperature(23.0×10^-6 m/K);(4)The friction coefficient tends to be stable and close to0.20 with the increase of Si C_p particle size,and the XY plane is larger than the Z plane.In the Si_p/flake graphite/aluminum composites prepared by Si _p with different particle sizes:(1)When the particle size of Si _p is 15?m,the maximum bending strength in XY plane is 89.2 MPa,and the maximum bending strength in Z plane is 83.8 MPa;(2)When heated from 20?to 100?,the maximum thermal conductivity of Si_p/flake graphite/aluminum composite with particle size of 15?m is 370 W/(m k);(3)At room temperature,the thermal expansion coefficient of Si_p/flake graphite/aluminum composite is 13.0×10^-6 m/K;(4)The friction coefficient tends to be stable and close to 0.20 with the increase of Si_p particle size,and the XY plane is larger than the Z plane.The Si C_p/flake graphite/aluminum composites with different particle sizes and Si _p/flake graphite/aluminum composites have excellent thermal stability.In the alternating environment of 25?and 100?,the structure of Si C_p/flake graphite/aluminum composites will not be damaged and voids will be formed,which will greatly reduce the thermal conductivity of the materials,and the internal high thermal conductivity can be maintained.After 20 cycles in the temperature range,the composites showed good thermal stability.The strength of Si C_p/flake graphite/aluminum composites increases first and then decreases with the increase of silicon carbide particle size.High strength silicon carbide particles are very beneficial to improve the strength of composites,but the increase of particle size easily leads to the increase of porosity The increase of Si C particle size is beneficial to the decrease of thermal expansion coefficient of graphite/aluminum composites in Z direction,which is mainly due to the low thermal expansion coefficient of Si C particles.Silicon particles are added into graphite/aluminum.During the vacuum hot pressing process,the edge of silicon particles and aluminum diffuse and dissolve to form an aluminum-silicon alloy,which improves the strength of matrix aluminum and forms a dense interface between silicon and aluminum.However,with the increasing of the particle size of silicon powder,the strength of the composite material decreases continuously,which is mainly related to the brittle fracture of brittle silicon particles und er pressure.There are 24 figures,4 tables and 100 references in this paper.