Tungsten-Copper Composites Preparation by Laser Cladding

With the continuous improvement of the power of electronic devices and the miniaturization of devices, the corresponding power density is also increasing, and the problem of heat dissipation is becoming more and more prominent, which puts forward higher requirements for the performance and reliability of heat sink materials.

Tungsten copper has excellent microwave shielding function and high strength. It is these characteristics that make the application of W-Cu composites in large integrated circuits and high power microwave devices develop rapidly in recent years. At present, tungsten-copper material has become an important electronic packaging and heat sink material because of its high heat resistance, good conductivity and thermal conductivity, as well as its thermal expansion coefficient matching with silicon, gallium arsenide and ceramic materials.

The technical problem to be solved is to overcome the shortcomings of the existing technology. Some enterprises in the industry use laser cladding to prepare tungsten-copper composite materials. The technological process includes:

(1)Using copper powder and tungsten powder as raw materials, the proportion is 15 wt% of copper and 85 wt% of tungsten; adding appropriate amount of isopropanol and alumina grinding balls, mixing with wet milling for 20 hours, drying the mixed powder, passing through 100 mesh sieve;

(2)Oxygen-free copper sheet is used as the matrix material with a thickness of 1 mm, which is machined into the required shape and size. The surface is cleaned before cladding, sandblasted and finally cleaned by alcohol ultrasonic.

(3)The tungsten-copper surface layer is prepared by laser cladding equipment. The laser equipment adopts optical fiber laser, the output wavelength is 1064 nm, the continuous output mode is adopted, and the powder feeding mode is synchronous powder feeding. The technological parameters are: laser power 500 W, powder feeding 2.0 g/min, scanning speed 300 mm/min. The thickness of tungsten-copper surface layer is 50-1000 um.

(4)Laser cladding W-Cu composites prepared by spraying were polished. The results show that the thermal conductivity is 330W/(m.K) and the expansion coefficient is 7.3 *10-6K-1.

Laser cladding tungsten-copper materials match silicon wafers, gallium arsenide and ceramics. Oxygen-free copper matrix provides high thermal conductivity. Its overall thermal conductivity reaches 300-350 W/(m.K), which is twice as high as bulk tungsten-copper materials. Its density reaches 99.5%, which meets the requirements of military packaging materials. The tungsten-copper composite has broad application prospects in the fields of LDMOS, high power semiconductor lasers, high power LED and IGBT devices.

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