TW202125735A - Use of indium-bismuth alloy for heat dissipation reducing the porosity and improving the heat dissipation effect - Google Patents

Abstract

A use of indium-bismuth alloy for heat dissipation is disclosed, including: an indium-bismuth alloy fixed between a heat source and an adjacent heat sink; the indium-bismuth alloy is heated and melted into a liquid phase; and the liquid indium-bismuth alloy flows to fill a gap between the heat source and the heat sink, so that the liquid indium-bismuth alloy forms a liquid-phase heat conduction channel. By densification of the indium-bismuth alloy before contacting the heat source, the porosity can be reduced and the heat dissipation effect can be effectively improved.

Description

The use of indium-bismuth alloy for heat dissipation

The present invention relates to the use of a metal in heat dissipation, in particular to the use of an indium-bismuth alloy in heat dissipation.

The heat-generating components in electronic products will continuously generate heat energy during use, and the accumulated heat energy may cause the performance of the heat-generating components to decrease. Generally, heat-generating components are matched with heat-dissipating components to dissipate heat. Heat-dissipating components usually include metal plates and heat-dissipating fins. In response to the light and thin requirements of electronic products, thin heat sinks are gradually developed. However, thin heat sinks are limited by processing procedures and are far less flat than bulk materials. There are a lot of gaps between the interfaces of thin heat sinks and heat-generating components, and there is air with a thermal conductivity of only 0.024 W/mK in these gaps. It is easy to form thermal siltation and cause severe thermal resistance.

In order to fill the gaps between thin heat sinks and heat generating components, the industry widely uses thermal paste with a thermal conductivity of about 2~5 W/mK. However, please match the seventh figure and apply the thermal paste (1') to the When the heat-generating element (2') is mounted, a large number of bubbles (A') are easily generated in the heat-dissipating paste (1'), and the air in these bubbles (A') will greatly reduce the heat dissipation effect of the heat-generating element (2').

In view of this, in order to make the heat dissipation effect better, the inventor proposed an indium-bismuth alloy for heat dissipation, including: fixing an indium-bismuth alloy between a heat source and an adjacent heat-dissipating end; the indium-bismuth alloy is heated and melted into Liquid phase; and the indium-bismuth alloy in the liquid phase flows to fill a gap between the heat source and the heat dissipation end, so that the indium-bismuth alloy in the liquid phase forms a liquid-phase heat conduction channel.

Further, the heat dissipation end is a heat dissipation fixing member, and the heat dissipation fixing member fixes the indium-bismuth alloy to the heat source.

Wherein, after the heat source stops heating, the indium-bismuth alloy in the liquid phase is cooled down and solidified into a solid interlayer between the heat source and the heat sink, and after the indium-bismuth alloy in the liquid phase is cooled down, the solid interlayer is still attached to the heat source And the heat dissipation end, and the base phase of the solid interlayer is BiIn ₂ phase or BiIn phase.

Wherein, the solid-liquid phase change volume expansion of the solid interlayer is between 0.01 cm ³ /cm ³ and 0.025 cm ³ /cm ³ .

The thickness of the indium-bismuth alloy ranges from 0.02 to 0.1 mm, and the melting point of the indium-bismuth alloy ranges from 60°C to 80°C.

Further, a flash of material flowing out from the gap is removed.

Furthermore, an anti-overflow member is arranged on the edge of the gap to prevent the overflow of the material.

Wherein, the size of the indium-bismuth alloy is not larger than the heat source and the heat dissipation end.

Further, before the indium-bismuth alloy is fixed on the heat source and the heat dissipation end, the grease on the indium-bismuth alloy is removed.

Further, the indium-bismuth alloy contains less than 40 wt% tin.

According to the above technical features, the following effects can be achieved:

1. The indium-bismuth alloy is densified before contacting the heat source to reduce the porosity and effectively improve the heat dissipation effect.

2. The heat dissipation fixture fixes the indium-bismuth alloy, and when the phase of the indium-bismuth alloy changes to a liquid state, it will not overflow from the heat source.

3. The heat dissipation fixture is a material with high thermal conductivity, and the heat energy can be conducted from the heat source through the indium-bismuth alloy to the heat dissipation fixture to dissipate heat.

4. The thickness of the indium-bismuth alloy is as thin as 0.02 mm, which will not affect the installation of the heat source and heat dissipation fixture.

5. The viscosity of the indium-bismuth alloy in the liquid phase is only one ten thousandth of the conventional heat dissipation paste, which makes it easier to completely fill the gap, and the bubbles are easier to discharge, thereby increasing the heat transfer effect.

6. After the liquid phase indium-bismuth alloy cools down, the solid interlayer will still be attached to the heat source and the heat sink to ensure that no air enters between the heat source and the heat sink, and there is no need to worry about the next time the indium-bismuth alloy forms a liquid-phase heat conduction channel. There are bubbles.

7. The volume expansion of the solid-liquid phase change of the solid interlayer is moderate, which is beneficial to keep the solid interlayer attached to the heat source and heat dissipation end.

8. The solid interlayer will still adhere to the heat source and heat sink after cooling, and the base phase of the solid interlayer is BiIn ₂ phase or BiIn phase. Even in the solid state, the indium-bismuth alloy still has a thermal conductivity coefficient of more than 28 W/m℃. , Is more than 5 times of conventional thermal paste.

Based on the above technical features, the main effects of the indium-bismuth alloy of the present invention for heat dissipation will be clearly presented in the following embodiments.

Please refer to Figures 1 to 3, which illustrate the use of indium-bismuth alloys for heat dissipation according to embodiments of the present invention, including:

A densified solid indium-bismuth alloy (2) is placed between a heat source (1) and an adjacent heat dissipating end, and the indium-bismuth alloy (2) is fixed between the heat source (1) and the heat dissipating end Before, the grease on the indium-bismuth alloy (2) was removed. In the embodiment of the present invention, the heat dissipation end is a heat dissipation fixture (3), and the indium bismuth alloy (2) is fixedly contacted with the heat source (1) by the heat dissipation fixture (3), and the indium bismuth alloy (2) The area of) is not greater than the area of the heat source (1) and the heat dissipation fixing member (3).

The heat source (1) can be a central processing unit, a graphics processor, or an LED component that generates heat during operation. The heat dissipation fixture (3) is made of a material with high thermal conductivity. For example, the heat dissipation fixture (3) can be a heat dissipation fan, and the heat conduction coefficient of the heat dissipation fixture (3) is not lower than that of the indium-bismuth alloy (2).

Please refer to the fourth figure, and please match the second figure. The densification method of the indium-bismuth alloy (2) is: heating the mixture of 67 wt% indium and 33 wt% bismuth to form a eutectic with a thermal conductivity of about 54 W/ mK of the indium-bismuth alloy (2), the indium-bismuth alloy (2) is clamped up and down by a cover plate (A) and a carrier plate (B), so that the indium-bismuth alloy (2) is not covered by the cover plate ( A) A covered area covered by the cover plate (A) still has an uncovered area not completely covered by the cover plate (A). A weight (C) is placed above the cover plate (A), and a flat heat source (D) is placed under the carrier plate (B). Use the plane heat source (D) to heat the indium-bismuth alloy (2), the indium-bismuth alloy (2) is heated and melted, and the indium-bismuth alloy (2) in the liquid phase in the coverage area is subjected to the weight (C), the The pressure of the cover plate (A) and the carrier plate (B) will flow to the uncovered area, and at the same time most of the bubbles in the indium-bismuth alloy (2) in the liquid phase will be brought to the uncovered area. The covered area is discharged. Since the viscosity of the indium-bismuth alloy (2) in the liquid phase is only 2-100 cp, the bubbles are more easily brought to the uncovered area and discharged, which can make the indium-bismuth alloy (2) in the liquid phase pores The rate is less than 15%, which means that there is no pore (E) exceeding 15% by volume in the indium-bismuth alloy (2) per unit volume of liquid phase. In this way, the surface tension of the indium-bismuth alloy (2) in the liquid phase against thinning can also be reduced, so that the thickness of the solidified indium-bismuth alloy (2) is between 0.02 and 0.1 mm, which is thinned to 0.02 The millimeter of the indium-bismuth alloy (2) will not affect the installation of the heat source (1) and the heat dissipation fixing member (3).

Please refer to the third, fifth and sixth diagrams. When the heat source (1) generates heat at a heating temperature of 20°C to 150°C, the melting point of the indium-bismuth alloy (2) is between 60°C and 60°C. At 80 degrees, once the heating temperature is higher than the melting point of the indium-bismuth alloy (2), the indium-bismuth alloy (2) phase changes into a liquid state. When the indium-bismuth alloy (2) undergoes a phase change, the indium-bismuth alloy (2) absorbs heat energy from the heat source (1) as latent heat and melts into a liquid phase, thereby cooling the heat source (1). At the same time, the indium-bismuth alloy (2) that becomes the liquid phase flows to fill a gap (30) between the heat dissipation fixture (3) and the heat source (1). For example, the heat dissipation fixture (3) is a heat dissipation fan, and the liquid In contrast, the indium-bismuth alloy (2) can mainly fill the gap (30) between the fin of the cooling fan and the heat source (1), and even fill the gap (30) between the fin and the fin, Increase the contact area between the indium-bismuth alloy (2) and the heat dissipation fixture (3) in the liquid phase, so that the gap (30) forms a liquid-phase heat conduction channel (20), and the indium-bismuth alloy (2) in the liquid phase can Continue to absorb heat energy from the heat source (1), conduct heat energy to the heat dissipation fixing member (3) through the liquid phase heat conduction channel (20) to dissipate heat, further increase the heat dissipation efficiency, and make the heat source (1) cool down more quickly. The viscosity of the indium-bismuth alloy (2) in the liquid phase is only 2~100 cp, and the low viscosity makes it easier to fill the gap (30) completely, even if the heat dissipation fixture (3) touches the indium-bismuth alloy (2) accidentally Air is brought in, and after the air is covered by the indium-bismuth alloy (2) in the liquid phase into bubbles, the bubbles will easily move in the indium-bismuth alloy (2) in the liquid phase and be discharged out of the gap (30). Further enhance the heat transfer effect. Since the area of the indium-bismuth alloy (2) is smaller than that of the heat source (1), and the thermal conductivity of the indium-bismuth alloy (2) is as high as 54 W/mK, heat energy can be quickly transferred to the heat dissipation fixture (3) for cooling and solidification, In addition, the heat dissipation fixing member (3) is fixed so that the indium-bismuth alloy (2) in the liquid phase will not overflow from the heat source (1). The indium-bismuth alloy (2) in the liquid phase reduces the porosity by densification, although there may still be less than 15% of the pores (E) in the indium-bismuth alloy (2) in the liquid phase, but a small amount of the pores (E) It will not affect the heat conduction of the indium-bismuth alloy (2) in the liquid phase. The heat energy can follow the edge of the pore (E) and the liquid-phase heat conduction channel (20) as shown in the direction of the arrow in the sixth figure. ) Is conducted to the heat dissipation fixing member (3) to dissipate heat. In this way, the indium-bismuth alloy (2) in the liquid phase can effectively improve the heat dissipation effect of the heat source (1).

When the amount of the indium-bismuth alloy (2) in the liquid phase is large, there may be a flash out of the gap (30). In addition to directly removing the flash, it is also possible to install a guard on the edge of the gap (30). Overflow parts, such as coated silicone or enclosure kits, etc., prevent the overflow from flowing out, but this scenario is not shown in the diagram.

Please refer to Figures 6 and 7. After the heat source (1) stops heating or the heating temperature drops below the melting point of the indium-bismuth alloy (2), the indium-bismuth alloy (2) in the liquid phase is solidified into the A solid interlayer between the heat source (1) and the heat dissipation fixture (3), the solid interlayer has a ^{volumetric expansion of 0.0181 cm 3} /cm ³ between the solid and liquid phases, and the solid interlayer is still attached to the heat source (1) And the heat dissipation fixing member (3). The volume expansion of the solid-liquid phase transition of the solid interlayer is between 0.01 cm ³ /cm ³ and 0.025 cm ³ /cm ³ . By volume expansion, the solid interlayer can be maintained attached to the heat source (1) and the heat dissipation fixing member (3). After the solid interlayer next time the heating temperature of the heat source (1) rises above the melting point of the indium-bismuth alloy (2), the phase change is performed again to absorb heat from the heat source (1) to cool the heat source (1), And the liquid phase heat conduction channel (20) is formed. Through the phase change of the indium-bismuth alloy (2), the indium-bismuth alloy (2) can be repeatedly used for heat dissipation purposes. Since the solid interlayer remains attached to the heat source (1) and the heat dissipation fixture (3), the adhesion strength of the solid interlayer can be ensured to be maintained. If the solid interlayer is not maintained attached to the heat source (1) and the heat dissipation fixture (3) (3), and the separation from the heat source (1) and the heat dissipation fixture (3) will cause air with a thermal conductivity of only 0.024 W/mK to be introduced into the gap (30). Next time the heat source (1) When heating, the air will isolate the thermal energy transfer of the solid interlayer. Even if the solid interlayer is re-melted into the liquid phase of the indium-bismuth alloy (2) to form the liquid phase heat conduction channel (20), the air may still form a large amount of The aperture (E) blocks the heat transfer of the liquid phase heat conduction channel (20), and makes the solid interlayer less likely to be attached to the heat source (1) and the heat dissipation fixture (3), thereby introducing more air, Such a vicious circle will cause the heat source (1) to be overheated and damaged due to inability to dissipate heat well. In addition, the base phase of the solid interlayer is BiIn ₂ phase or BiIn phase. Even in the solid state, the indium-bismuth alloy (2) still has a theoretical thermal conductivity of more than 28 W/m℃, which is a conventional heat sink paste. (1') more than 5 times.

The indium-bismuth alloy (2) may further contain less than 40 wt% tin, for example: 51 wt% of indium, 32.5 wt% of bismuth and 16.5 wt% of tin are used to form the indium-bismuth alloy (2), or The indium-bismuth alloy (2) is formed by 25 wt% indium, 57 wt% bismuth, and 18 wt% tin eutectic, which can also be used for heat dissipation. When the indium-bismuth alloy (2) is formed by a eutectic of 51 wt% indium, 32.5 wt% bismuth, and 16.5 wt% tin, the solid-liquid phase change volume expansion of the solid-state interlayer is 0.0201 cm ³ /cm ³ ; When the indium-bismuth alloy (2) is formed by 25 wt% indium, 57 wt% bismuth and 18 wt% tin eutectic, the solid-liquid phase change volume expansion of the solid interlayer is 0.0131 cm ³ /cm ³ .

Please refer to the eighth to tenth figures, and please match the first figure. The eighth to tenth figures are the microstructure photos of the indium-bismuth alloy (2) under different composition ratios observed by a scanning microscope. The eighth figure is the indium-bismuth alloy (2) formed by the eutectic of 51 wt% indium, 32.5 wt% bismuth and 16.5 wt% tin. The melting point is 60℃. At this time, the atoms of the indium-bismuth alloy (2) The percentage is indium:bismuth:tin=60.1:21.1:18.8, and after the eighth image is analyzed by Energy-dispersive X-ray spectroscopy (EDS), the percentage of the white-gray base phase is indium:bismuth : Tin = 62.2: 23.5: 14.46, BiIn ₂ phase in line with the three-phase diagram. The ninth figure is the indium-bismuth alloy (2) formed by the eutectic of 67 wt% indium and 33 wt% bismuth. The melting point is 70℃. After the ninth figure is analyzed by EDS, the percentage of the white-gray base phase is It is indium:bismuth=68.57:31.43, which conforms to the BiIn ₂ phase of the phase diagram. The tenth figure is the indium-bismuth alloy (2) formed by the eutectic of 25 wt% indium, 57 wt% bismuth and 18 wt% tin. The melting point is 80℃. The composition percentage of the gray base phase is indium:bismuth:tin=46.76:50.84:2.4, and the BiIn phase conforms to the three-phase diagram. From the above analysis, it can be known that the base phase of the solid interlayer is indeed BiIn ₂ phase or BiIn phase.

Based on the description of the above embodiments, when one can fully understand the operation and use of the present invention and the effects of the present invention, but the above embodiments are only the preferred embodiments of the present invention, and the implementation of the present invention cannot be limited by this. The scope, that is, simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the description of the invention, are all within the scope of the present invention.

this invention (1): Heat source (2): Indium-bismuth alloy (20): Liquid phase heat conduction channel (3): Heat dissipation fixture (30): Gap (A): Cover (B): Carrier board (C): Heavy objects (D): Plane heat source (E): Porosity

Prior art (1'): Thermal paste (2'): Heating element (A'): Bubble

[The first figure] is a three-dimensional exploded view of an embodiment of the present invention.

[Second Figure] is a side view of an embodiment of the present invention.

[Third Figure] is a flowchart of an embodiment of the present invention.

[Fourth figure] is the first schematic diagram of the embodiment of the present invention, showing the densification process of the indium-bismuth alloy.

[Fifth Figure] is the second schematic diagram of the embodiment of the present invention, showing that the indium-bismuth alloy phase changes into a liquid state.

[The sixth figure] is a partially enlarged view of the fifth figure of the embodiment of the present invention, showing the heat conduction of the indium-bismuth alloy.

[Figure 7] is a schematic diagram of the implementation of the conventional technology using thermal paste.

[The eighth figure] is a photo 1 of the microstructure organization of the embodiment of the present invention.

[Figure 9] is the second photo of the microstructure organization of the embodiment of the present invention.

[Figure 10] is the third photo of the microstructure organization of the embodiment of the present invention.

(1): Heat source

(2): Indium-bismuth alloy

(3): Heat dissipation fixture

Claims (10)

A use of indium-bismuth alloy for heat dissipation, including: Fixing an indium-bismuth alloy between a heat source and an adjacent heat sink; The indium-bismuth alloy is heated and melted into a liquid phase; and The indium-bismuth alloy in the liquid phase flows to fill a gap between the heat source and the heat dissipation end, so that the indium-bismuth alloy in the liquid phase forms a liquid-phase heat conduction channel. The indium-bismuth alloy described in item 1 of the scope of patent application is used for heat dissipation. Further, the heat dissipation end is a heat dissipation fixing member, and the heat dissipation fixing member fixes the indium-bismuth alloy to the heat source. The indium-bismuth alloy described in item 1 of the scope of patent application is used for heat dissipation, wherein after the heat source stops heating, the indium-bismuth alloy in the liquid phase is cooled and solidified into a solid interlayer between the heat source and the heat sink, After the indium-bismuth alloy in the liquid phase is cooled, the solid interlayer is still attached to the heat source and the heat sink, and the base phase of the solid interlayer is BiIn ₂ phase or BiIn phase. The indium-bismuth alloy described in item 3 of the scope of patent application is used for heat dissipation, wherein the solid-liquid phase change volume expansion of the solid interlayer is between 0.01 cm ³ /cm ³ and 0.025 cm ³ /cm ³ . The indium-bismuth alloy described in item 1 of the scope of the patent application is used for heat dissipation, wherein the thickness of the indium-bismuth alloy is between 0.02 and 0.1 mm, and the melting point of the indium-bismuth alloy is between 60°C and 80°C. The indium-bismuth alloy described in item 1 of the scope of the patent application is used for heat dissipation, and further, a flash flowing out of the gap is removed. For example, the indium-bismuth alloy described in item 6 of the scope of patent application is used for heat dissipation. Furthermore, an anti-overflow member is provided on the edge of the gap to prevent the overflow of the material. The indium-bismuth alloy described in item 1 of the scope of the patent application is used for heat dissipation, wherein the size of the indium-bismuth alloy is not larger than the heat source and the heat sink. The indium-bismuth alloy described in item 1 of the scope of patent application is used for heat dissipation. Furthermore, before the indium-bismuth alloy is fixed on the heat source and the heat sink, the grease on the indium-bismuth alloy is removed. The indium-bismuth alloy described in item 1 of the scope of the patent application is used for heat dissipation. Furthermore, the indium-bismuth alloy contains less than 40 wt% tin.

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