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|High Temperature Stamping Forging to Fabricate Fully Densified Copper Tungsten and Copper Molybdenum Heat Sink Materials|
|Keywords: Copper Tungsten , Copper Molybdenum, Thermal Management|
|Copper tungsten and copper molybdenum composites, preserving tungsten and molybdenum¡¯s characteristic of low thermal expansion and copper¡¯s high thermal conductivity, have been widely used in the packaging of microwave devices, optoelectronic components, integrated circuits, and many other electronic packaging applications. Their measures of thermal expansion coefficient, thermal conductivity, and electrical conductivity can easily be controlled by varying copper/tungsten and copper/molybdenum ratios. They can also be matched with semiconductor silicon, arsenic, gallium arsenide, aluminum oxide and beryllium oxide, etc. Since tungsten, molybdenum and copper have considerably different melting points, it is impossible to melt W and Cu into each other at high temperatures. In other words, no eutectic will be formed. Therefore, copper/tungsten and copper/molybdenum composite material can only be fabricated through powder metallurgy. At present, there are three major techniques: infiltration, high-temperature liquid phase sintering, and metal injection molding. The state of the art CuW and CuMo materials obtained from above methods are not fully densified as shown in studies by SEM micrographs and ultrasonic scan on the CuW and CuMo material from the leading manufacturers. There are many micropores inside the composite body. These micropores would exhibit themselves as potential sources for corrosion after gold plating. In this paper, we studied the effect of high temperature forging on the densification of CuW and CuMo composite material after infiltration. In high temperature forging process, the infiltrated CuW and CuMo parts were hit repeatedly with compressive forces. Using SEM x-section, ultrasonic scan and hermeticity etc. to characterize the improved CuW and CuMo parts, we found out that the forged CuW and CuMo composite bodies were 100% fully densified and the hermeticity stabilized at 5x10-10 Pa.m3/s or 5x10-9 atm cc/s). Furthermore, the resultant material can be polished to mirror finish with the final finish comparable to that of silicon wafers.|
|Guosheng Jiang, PhD, General Manager
Changsha Saneway Electronic Materials, Co Ltd.
Changsha, Hunan 410083,