Numerous types of researches on tungsten copper composites sintering technologies are going on along with the increasing applications development and different performance requirements. Many tungsten copper sintering methods are in the research stage. From the perspective of mass production, there are mainly below new developments in tungsten copper sintering.
Direct tungsten copper sintering of superfine tungsten copper powders
Although both tungsten and copper have a good wetting ability, they differ vastly in physical properties and cannot form alloy by solid solution with each other. Therefore, through the direct tungsten copper sintering in the usual conditions, it is impossible to obtain high-density products. The sintering temperature exceeds the melting point of copper. The liquid-phase tungsten copper sintering occurs. Due to the development of superfine powders mixed sintering, tungsten copper composites with various components have been directly produced through molding and sintering superfine tungsten copper mixed powder. The powder was obtained from the co-reduction of the superfine tungsten-copper mixed compound. According to reports with this method, tungsten copper with 5-25% (mass fraction) copper content can be produced by direct sintering (Table 5) at 1200~1450 ℃ for uses of various electronic packaging devices and circuits breakers.
Sintering of tungsten copper mixed powders
Tungsten sintering has been studied extensively for many years. Ni is the most substantial activation sintering effect. When 0.2~ 0.5%(mass fraction) nickel powders are added at about 1500℃, a high density (>98% relative density) will achieve by sintering tungsten powders. However, in the latest tungsten copper electrical contact, sintering tungsten skeleton and tungsten copper mixed powders at a lower temperature by adding small amounts of nickel powders could not achieve a perfect effect. Studies of the activation sintering behavior of tungsten copper mixed powders in detail found that Co and Fe’s activation effect was notably higher than that of Ni, especially Co. For instance, 98% relative density can be achieved for Tungsten Copper material.
Moreover, when Co was for activation sintering, a tungsten and Co interface layer with high diffusion was on the surface of the tungsten grain. This promotes the diffusion and sintering of tungsten grain. Instead, when Co(Co 20.5%) was too much, a thicker W and Co layer can form. This would affect the migration and diffusion of materials to reduce the sintering density.
The most significant disadvantage of directly sintering tungsten copper is that tungsten copper’s electrical and thermal conductivity is reduced by activation sintering.
High-temperature tungsten skeleton sintering and copper infiltration method
High-temperature sintering has always been a primary method for making tungsten, molybdenum, and their alloy materials and products. Tungsten Copper composite with high skeleton density and low copper content (W (Cu)≤20%) come from the high density and low porosity super tungsten billet obtained by sintering. Tungsten Copper sintering can adjust and control the particle size of raw material tungsten powder and the system of high-temperature sintering. The required tungsten copper composites were obtained via copper infiltration.
High-temperature tungsten skeleton sintering and copper infiltration can remove the impurities in the materials to the maximum extent. The low gas content and the sintered Tungsten skeleton with high strength ensure the excellent strength performance of Tungsten Copper composites. Therefore, it is the most attractive method for many new technology applications and high performance requirements. The downsides of high-temperature sintering copper infiltration method are high energy consumed and high specialized control level, resulting in a relatively high fabrication cost of Tungsten Copper material products.