Infiltration of molybdenum -copper composite material prepared

For micro-electronic packaging and heat sink application, Mo-Cu composite with high relative theoretical density, excellent structural uniformity, low coefficients of thermal expansion,high thermal conduc-tivity and high electric conductivity were required,so that it was very positive to research.Molybdenum powders were successfully fabricated by MoO3 slurry suspension with appropriate volume content and the addition of ammonia and PEG-2000 via spraying drying-calcination-hydrogen reduction process,Mo-Cu composites with high relative theoretical density and low copper content were fabricated by pressing as-prepared powders to compacts,then pre-sintering and infiltrating. The mechanical and physical properties of Mo-Cu composites were analyzed by infiltration method. The result shows that as follow:1) Precursor powders were obtained by sprayig drying the slurry suspension with 15% MoO3 volume content,2wt%PEG dispersant and pH value of 4.5.Molybdenum powders were fabricated by calcinating the precursor powders(3℃/min heating rate to 420℃for 2 hours hold) and two-stage hydrogen reduction (530℃for 2 hour hold,900℃for 5 hours hold). As-prepared molybdenum powders were pure,nearly spherical and dense,in addition the size distribution is scattered under above prepared process.2) Compared to conventional molybdenum powders,as-prepared molybdenum powders have a more excellent characteristics. The relation between compact density and pressure satisfies double logarithmic equations that put forward by Huangpeiyun:mlgln [(dm-do)dl (dm-d)do] =lgP-lgM When the pressure was below 1000MPa and above 1000MPa, modulus of compression was 0.073 and 0.79 respectively,and hardening exponent was 4.17 and 2.15 respectively for conventional molybdenum powders.But modulus of compression are 0.066 and 0.15 respectively,and hardening exponent was 4.05 and 3.41 respectively for as-prepared molybdenum powders. 3)The optimal infiltration temperature for Mo65Cu,Mo70Cu and Mo75Cu, Mo80Cu,Mo85Cu was 1200℃and 1250℃. Infiltrated at 1300℃, holding time of optimal infiltration was an hour for Mo-Cu alloys different molybdenum content.4) Thermal conductivity and coefficients of thermal expansion for Mo70Cu,Mo75Cu,Mo80Cu,Mo85Cu were 190,181,166 153 W.m-1.K-1 and 8.4×10-4,7.7×10-4,7.1×10-4,6.6×10-4℃-1.5) Microstructure of Mo65Cu and Mo70Cu was homogeneous and particles of molybdenum and copper were fine with a little copper segregation,whereas Mo75Cu,Mo80Cu,Mo85Cu without copper segre-gation. Molybdenum-copper had a high relative theoretical density and the phase distribution of copper and molybdenum were homogeneous via a infiltration method, which made sure that Mo-Cu alloys possess high thermal conductivity and low gas impermeability.