Tungsten Copper with Gradient Structure

Tungsten copper (W-Cu) and molybdenum copper (Mo-Cu) are composed of respectively tungsten and molybdenum with copper, which called two-phase composites and has many advantages when it used in some devices with high power, such as high hardness, high strength, high melting point, excellent chemical stability, excellent thermal and electrical conductivity and lower coefficient of thermal expansion. As a kind of electronic packaging heat sink material takes place of conventional materials gradually, the related researchers make an intensive study on tungsten copper, which includes add active agents, change powder properties to improve the sintering density of tungsten copper materials.

However, the conditions of some industries today have become more and more strict (including temperature, pressure, power, etc.), which requires tungsten copper has better properties. Inspired by tungsten carbide with gradient structure, the Japanese researcher propose new concept of functional materials with gradient structure and from the preparation process structure, computer simulation and forecasting has done sufficient research, have also made substantial progress, so that it plays an important role in some high-power devices. Tungsten copper composite material is kind of two-phase psudoalloy, which composed of two metals tungsten and copper with a great difference in physicochemical properties.

Its properties will change with the structure. Viewed from the aspect of gradient structure, it can has one end with a high hardness, high melting point, tungsten or copper content is low high-density tungsten copper, while the other end is a good electrical and thermal conductivity and high plasticity of copper or copper content of tungsten, copper, in this way the formation of gradient structure having a tungsten-copper composite materials have a good specificity and a broader application prospect.

For the manufacturing process of the gradient structure tungsten-copper composite materials, researchers and scholars in related fields, and also made a variety of attempts to conceive. Here is a brief introduction to several related new technologies, such as conventional dry lamination method, hierarchical load a different size of tungsten powder, cold pressed, sintered, after copper infiltration preparing different graded material consisting of tungsten-copper ( good sintered porous tungsten skeleton electrochemical corrosion formed along the direction of tungsten skeleton having a gradient porosity by infiltration of copper can be obtained having a continuous change in the composition of tungsten copper gradient material); the other one uses hot isostatic pressing diffusion bonding to form tungsten copper with gradient structure by different contents.

In addition, another type is prepared by continuous gradient layer, such as slip casting, sedimentation molding, centrifugal molding, etc. Plasma spraying is a kind of new method that are compacting and sintering tungsten copper powder with different content. There are two methods which have already patented process, one is the use of powder metallurgy - infiltration process. Preparation of powder metallurgy method which utilizes two components completely different copper tungsten compact, then where the thermal conductivity of tungsten copper larger compact embedded in another compact, due to the embedding of relatively high copper content briquette making its thermal conductivity is relatively high, and has a lower peripheral compact copper content, thus ensuring the overall coefficient of thermal expansion gradient material decreases. Another one is that combines tungsten copper (W-Cu) with ceramic based on aluminum nitride-aluminum (AlN-Al), ceramic has a gradient structure with a metal having a thermal expansion coefficient due to the match, so the lower internal stress, and as part of a combination of metal and ceramic high thermal conductivity such that heat will not affect the heat concentrated in the buffer layer and the heat radiating effect of the heat sink materials.