Preparation of Microelectronic Tungsten Copper Package-Sheet

With the development of microelectronics technology, the requirements of material are higher and higher. According to the famous Moore's Law, when the price is constant, the number of transistors that can be accommodated in an integrated circuit will be doubled about every 24 months, which means that with the substantial increase in unit volume of power, the heat is also greatly increased. According to the U.S. Air Force's investigation, over 70% of the invalidity of electronic components is related to over-heat, and therefore heat-sink material is crucial for microelectronic devices.

Tungsten copper alloy is a kind of alloy composed of tungsten and copper. Because tungsten and copper are completely immiscible, it is a two-phase alloy. It combines high melting point and low coefficient of thermal expansion of tungsten, and high thermal conductivity and high electrical conductivity and other properties of copper, so it is an excellent heat-sink material.

As the difference of the melting point of tungsten and copper is too large, 3450 ℃ and 1083 ℃respectively, they can’t be produced while melting, only to be produced by powder metallurgy. At present, high-end microelectronic tungsten copper package-sheets can only be made by grinding thicker (1mm or more) tungsten copper sheets with low efficiency and high cost, and large-size ultra-thin sheets such as W90Cu10 piece (LED use) of 6-inch and 0.1mm thick is difficult to grind. Therefore, the preparation-process of tungsten copper alloy sheet which is in line with the requirements of microelectronic packaging is in urgent need of a breakthrough. The preparation method of tungsten copper flake is as following:

(1) To press the steel mold to shape

The tungsten-copper powder is pressed with a hydraulic press to shape, and to get the steel-forming mold.

(2) To repress in a cold isostatic press

To repress the pressed steel-mold got in the step (1) in a cold isostatic press to obtain a repressing mold.

(3) Sintering with high temperature

To sinter the repressing mold obtained in the step (2) in a high temperature in a hydrogen molybdenum wire furnace to obtain a sintered mold.

(4) Hot-rolled

The sintered mold obtained in the step (3) is hot-rolled with a two-roll mill and then annealed. To repeat the hot-rolling and annealing according to the thickness of the sintered mold to obtain an annealed hot-rolled tungsten copper plate. And deal with the annealed and hot-rolled tungsten-copper sheet superficially.

(5) Warm rolling

The annealed hot-rolled tungsten copper plate of step (4) is warm-rolled, and then annealed to obtain an annealed warm-rolled tungsten-copper sheet;

(6) Cold-rolled

The annealed warm-rolled tungsten-copper sheet of step 5 is cold-rolled, and finally annealed, flattened to obtain tungsten copper sheet.

This kind of preparation of this tungsten copper sheet overcomes the defects and shortcomings of the traditional preparation-method of tungsten copper alloy. The prepared material has the advantages of uniform-microstructure, compactness and air-tightness, high production efficiency, high material-utilization-rate which can meet the package-requirements of microelectronic.

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