阅读说明：本技术 一种液态金属无硅热界面材料及其制备方法 (Liquid metal silicon-free thermal interface material and preparation method thereof ) 是由 贾潇 李石琨 刘斌 淮秀兰 周国辉 周敬之 于 2021-08-02 设计创作，主要内容包括：本发明公开了一种液态金属无硅热界面材料及其制备方法,该无硅热界面材料包括：液态金属、表面改性剂、无硅基体材料。本发明采用磁力搅拌与离心剪切混合相结合的方法,将表面处理过的液态金属液滴填充入无硅基体材料中,制成液态金属无硅热界面材料。通过调控金属液滴的尺寸和形状,使得复合材料具有高热导率及低热阻,能够有效解决传统硅基热界面材料硅油挥发等易老化问题,大幅提高热界面材料的稳定性与可靠性。(The invention discloses a liquid metal silicon-free thermal interface material and a preparation method thereof, wherein the silicon-free thermal interface material comprises the following components: liquid metal, surface modifier, silicon-free matrix material. The invention adopts a method combining magnetic stirring and centrifugal shearing mixing to fill liquid metal drops with surface treatment into a silicon-free matrix material to prepare the liquid metal silicon-free thermal interface material. By regulating and controlling the size and the shape of the metal liquid drop, the composite material has high thermal conductivity and low thermal resistance, can effectively solve the problem that the traditional silicon-based thermal interface material is easy to age due to volatilization of silicon oil and the like, and greatly improves the stability and the reliability of the thermal interface material.)

1. A liquid metal silicon-free thermal interface material, characterized by: the raw materials comprise: liquid metal, surface modifier, silicon-free matrix material;

the liquid metal is one of gallium indium alloy, bismuth indium alloy, indium tin alloy, gallium indium tin alloy, bismuth indium tin alloy, indium tin zinc alloy, gallium indium tin zinc alloy, bismuth indium tin zinc alloy, gallium indium tin zinc silver alloy or indium tin zinc bismuth silver alloy;

the surface modifier is selected from one or more of 3-mercapto-N-nonyl propionamide, 1-dodecanethiol, mercapto-undecanamine hydrochloride, titanate and isocyanate;

the silicon-free matrix material is selected from one of epoxy resin, acrylate or polyurethane.

2. A liquid metal silicon-free thermal interface material as defined in claim 1, wherein: the raw material of the thermal interface material comprises the following components in percentage by volume: 65-85% of liquid metal and 15-35% of silicon-free matrix material, wherein the sum of the volume fractions of the liquid metal and the silicon-free matrix material is 100%; the dosage of the surface modifier is 0.1-5% of the mass of the liquid metal.

3. A method of making a thermal interface material as defined in claim 1, comprising: the method comprises the following steps:

step 1, adding liquid metal and a surface modifier into a dispersion liquid for magnetic stirring dispersion to obtain surface-treated metal droplets;

step 2, removing the supernatant of the metal droplets in the step 1, and drying the precipitate;

and 3, adding a silicon-free matrix material into the dried metal droplets, carrying out centrifugal shearing and mixing under a vacuum condition, taking a sample in the dispersing process, observing under a microscope, and finishing the configuration when the average diameter of the metal droplets is 1-30 mu m and the average length-diameter ratio is more than 1.5 to obtain the thermal interface material.

4. The production method according to claim 3, characterized in that: the dispersion is selected from ethanol, ethyl acetate, chlorobenzene, propanol or hexane.

5. The production method according to claim 3, characterized in that: the rotation speed of the magnetic stirring dispersion in the step 1 is 500-1500rpm, and the stirring time is 15-30 min.

6. The production method according to claim 3, characterized in that: in the step 2, drying is carried out for 1-6h under the drying condition of 60-80 ℃.

7. The production method according to claim 3, characterized in that: the centrifugal shearing and mixing condition in the step 3 is that the rotating speed is 800-2500rpm, the centrifugal shearing and mixing condition is gradually increased from small to large according to 100rpm, and each rotating speed is operated for 1-5min until the mixture is uniform.

Technical Field

The invention belongs to the technical field of heat dissipation materials, and particularly relates to a liquid metal silicon-free thermal interface material and a preparation method thereof.

Background

The traditional thermal interface material is mainly prepared by filling solid particles into silicon oil or silicon rubber to prepare materials such as heat-conducting silicone grease, a heat-conducting silicone rubber pad and the like, and because a silicon-based matrix material has certain volatility, small siloxane molecules in the thermal interface material are easy to volatilize, the silicon oil is separated out and the like along with the continuous rise of the temperature of electronic equipment in the using process, so that the composite material has the phenomena of drying, hardening and the like, the electronic components are polluted, the heat-conducting efficiency is greatly reduced, and the reliability of products is influenced, and therefore, the development of a silicon-free thermal interface material is urgently needed. Compared with the traditional solid particles, the liquid metal is adopted as the filler, so that the filler has many advantages, the liquid metal can better conform to the matrix material due to the liquid property, and the undesirable phenomena of hardening of the material and the like can not be caused when the filling amount is higher.

Generally, the viscosity of the silicon-free matrix material is less than that of materials such as silicone oil, silicone rubber and the like, so that the liquid metal silicon-free thermal interface material has better wettability on the surface of an electronic component and can effectively reduce the contact thermal resistance. The liquid metal silicon-free thermal interface material has no volatilization of siloxane micromolecules or precipitation of silicone oil under the heated and pressed environment, does not pollute parts, and simultaneously can effectively improve the stability and the service life of an electronic device because the material can better conform to the solid surface and has higher heat-conducting property.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides the liquid metal silicon-free thermal interface material which has high thermal conductivity and good wettability, can greatly reduce contact thermal resistance, can effectively improve the heat dissipation efficiency of the whole system, does not volatilize silane micromolecules, does not generate silicon carbide to cause circuit failure, and can ensure the stable operation of the system.

In order to achieve the purpose, the invention adopts the following technical scheme:

a liquid metal silicon-free thermal interface material comprises the following raw materials: liquid metal, surface modifier, silicon-free matrix material;

the liquid metal is one of gallium indium alloy, bismuth indium alloy, indium tin alloy, gallium indium tin alloy, bismuth indium tin alloy, indium tin zinc alloy, gallium indium tin zinc alloy, bismuth indium tin zinc alloy, gallium indium tin zinc silver alloy or indium tin zinc bismuth silver alloy;

the surface modifier is selected from one or more of 3-mercapto-N-nonyl propionamide, 1-dodecanethiol, mercapto-undecanamine hydrochloride, titanate and isocyanate;

the silicon-free matrix material is selected from one of epoxy resin, acrylate or polyurethane.

Further, the raw material of the thermal interface material comprises the following components in volume fraction: 65-85% of liquid metal and 15-35% of silicon-free matrix material, wherein the sum of the volume fractions of the liquid metal and the silicon-free matrix material is 100%; the dosage of the surface modifier is 0.1-5% of the mass of the liquid metal.

The preparation method of the thermal interface material comprises the following steps:

step 1, adding liquid metal and a surface modifier into a dispersion liquid for magnetic stirring dispersion to obtain surface-treated metal droplets;

step 2, removing the supernatant of the metal droplets in the step 1, and drying the precipitate;

and 3, adding a silicon-free matrix material into the dried metal droplets, carrying out centrifugal shearing mixing under a vacuum condition, taking a sample in the dispersing process, observing the sample under a microscope, and finishing the preparation when the average diameter of the metal droplets is 1-30 mu m and the average length-diameter ratio is more than 1.5 to obtain the uniformly mixed composite thermal interface material.

Further, the dispersion is selected from ethanol, ethyl acetate, chlorobenzene, propanol or hexane.

Further, the rotation speed of stirring and dispersing in the step 1 is 500-1500rpm, and the stirring time is 15-30 min.

Further, in the step 2, drying is carried out for 1-6h under the drying condition of 60-80 ℃.

Further, the centrifugal shearing mixing condition in the step 3 is that the rotating speed is 800-.

The method for preparing the liquid metal thermal interface material mainly comprises the following steps: ultrasonic dispersion, magnetic stirring, centrifugal shear mixing, and the like. Wherein the liquid metal is pulverized to 10 by ultrasonic dispersion¹-10²nm size (<1 μm), the majority of the formed metal droplets are approximately distributed in a spherical shape, but the inventor finds that the thermal conductivity of the thermal interface material prepared by mixing the nano metal droplets with the silicon-free matrix material by an ultrasonic dispersion method is sharply reduced; when the metal droplets are mixed directly with the silicon-free matrix material by centrifugal shear mixing using a planetary mixer, the size of the metal droplets is in the range of about 10¹-10²In the range of μm of>30 μm), the thermal conductivity of the prepared composite material slowly decreases. Further experiments show that the average diameter of the formed metal droplets is within the range of 1-30 μm by adopting a magnetic stirring and centrifugal shearing mixing mode, the shapes of the metal droplets are different and comprise not only spherical distribution but also an ellipsoidal and cylindrical structure, and the combination of the polymorphic metal droplets enables the interior of the composite material to form an intricate and complex heat conduction path, thereby being more beneficial to improving the heat conduction performance of the material.

When the average diameter of the metal liquid drops is within the range of 1-30 mu m, the size of the liquid drops is equivalent to the roughness of the surfaces of the chip and the radiator, so that the liquid metal composite material can be better attached between the chip and the radiator, the contact thermal resistance is effectively reduced, meanwhile, the thermal conductivity of the composite material is higher, and the heat dissipation performance is greatly improved.

The liquid metal silicon-free thermal interface material has higher thermal conductivity and lower thermal resistance, and the type and proportion of the liquid metal and the silicon-free matrix material and the size and shape of metal liquid drops play a decisive role in the thermal conductivity of the thermal interface material.

The liquid metal silicon-free thermal interface material is a thermal interface material with high thermal conductivity and low thermal resistance, can effectively help heat dissipation between a heating element and a radiating element, and can be applied to heating electronic components sensitive to silicon oil precipitation or siloxane volatilization.

In the invention, the thermal conductivity and stability of the thermal interface material can be further improved by designing and adjusting parameters such as the type, filling amount, size and form of the metal liquid drop and the like of the material.

Has the advantages that: the invention creatively designs the types of materials, modifies the surface of a metal liquid drop by adding a surface modifier and stirring and dispersing to form a metal liquid drop with the size of micron to millimeter, and then adds a silicon-free matrix material for centrifugal shearing and mixing, and experimental results show that when the average size of the metal liquid drop is in the range of 1-30 mu m and the average length-diameter ratio is more than 1.5, the thermal conductivity of the material is higher, and the uniformly mixed paste composite material is smeared between a heating element and a radiating element.

Drawings

FIG. 1 is an optical magnified view of the liquid metal silicon-free thermal interface material prepared in example 1.

FIG. 2 is a flow chart of a method for preparing a liquid metal silicon-free thermal interface material according to the present invention.

Detailed Description

In order to effectively improve the heat dissipation efficiency of high-power electronic components, the invention provides a liquid metal silicon-free thermal interface material. The liquid metal silicon-free thermal interface material has high thermal conductivity and low thermal contact resistance, can be closely attached to heating and radiating components, greatly reduces the thermal contact resistance, can effectively improve the radiating efficiency of the whole system, has no volatilization of siloxane micromolecules or separation of silicone oil, and can ensure the stable operation of the system.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It is to be understood that such description is merely illustrative and not intended to limit the scope of the present invention. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention. It may be evident, however, that one or more embodiments may be practiced without these specific details. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.

Aiming at the problems in the prior art, the invention designs a liquid metal silicon-free thermal interface material based on a liquid metal heat-conducting filler and a silicon-free matrix material so as to overcome the defects of common siloxane micromolecule volatilization, silicon oil precipitation and the like of the existing silicon-based thermal interface material, and the following description is provided with a specific embodiment.

The liquid metal silicon-free thermal interface material comprises the following raw materials: liquid metal, surface modifier, silicon-free matrix material.

In an embodiment of the present invention, the liquid metal may include, for example, one of gallium-indium alloy, bismuth-indium alloy, indium-tin alloy, gallium-indium-tin alloy, bismuth-indium-tin alloy, indium-tin-zinc alloy, gallium-indium-tin-zinc alloy, bismuth-indium-tin-zinc alloy, gallium-indium-tin-zinc-silver alloy, indium-tin-zinc-bismuth-silver alloy; the surface modifier can comprise one or more of 3-mercapto-N-nonyl propionamide, 1-dodecyl mercaptan, mercapto-undecylamine hydrochloride, titanate and isocyanate; the silicon-free matrix material may comprise, for example, one of epoxy, acrylate, polyurethane.

According to the invention, the microstructure of the liquid metal silicon-free thermal interface material is regulated, so that the composite thermal interface material has good heat conductivity and stability, silicone micromolecules are not volatilized, silicone oil is not separated out, the material wettability is good, the thermal contact resistance between the composite thermal interface material and electronic components can be greatly reduced, and the ultrahigh heat dissipation requirement of high-power electronic equipment is met. The heating power of heat dissipation electronic components in the 5G communication era is continuously increased, and higher requirements are put forward on the heat conduction and stability of the heat dissipation material, so that the liquid metal silicon-free thermal interface material has wide application prospects.

In order to further improve the heat dissipation effect of the liquid metal silicon-free thermal interface material, the invention designs the relevant parameters of the composite material.

In an embodiment of the invention, the liquid metal has a filling volume fraction of, for example, 65% to 85%, the metal droplets have an average size of, for example, 1 μm to 30 μm, and the average aspect ratio is greater than 1.5. By reasonably designing the filling volume fraction and the average size of the metal liquid drops, a heat conduction path can be effectively established and the heat conductivity of the composite material is improved. The volume fraction of the silicon-free matrix material may be, for example, 15% to 35%. The surface modifier may be, for example, 0.1% to 5% by mass of the liquid metal. The surface of the metal liquid drop is treated by reasonably selecting the type and the content of the surface modifier, so that the effective combination between the metal liquid drop and the silicon-free matrix material can be assisted.

The invention can further improve the heat dissipation effect of the composite thermal interface material by optimally designing all parameters of the liquid metal silicon-free thermal interface material.

The invention also provides a preparation method of the liquid metal silicon-free thermal interface material, which comprises the steps of firstly crushing the liquid metal into small droplets with millimeter to micron order in the dispersion liquid added with the surface modifier by a magnetic stirring method, drying, adding the silicon-free matrix material, vacuumizing, centrifuging, shearing and mixing to obtain the uniformly dispersed liquid metal silicon-free thermal interface material. The composite material is coated between the heating device and the heat dissipation device, and because the material has high thermal conductivity and good infiltration performance, the air gap between the heating device and the heat dissipation device can be effectively eliminated, the thermal contact resistance is reduced, and the heat dissipation performance is improved.

FIG. 1 schematically shows an optical magnification of a liquid metal silicon-free thermal interface material having an average particle size of about 16 μm, wherein the average aspect ratio of the metal droplets is 1.6.

Fig. 2 schematically shows a flow chart of a method for preparing a liquid metal silicon-free thermal interface material according to an embodiment of the invention, specifically:

step 1, adding liquid metal and a surface modifier into a dispersion liquid for magnetic stirring dispersion to form micrometer-millimeter metal liquid drops after surface treatment;

step 2, removing the supernatant to obtain a precipitate and drying the precipitate;

and 3, adding a silicon-free matrix material into the dried metal droplets, carrying out centrifugal shearing mixing under the condition of vacuumizing, observing a small amount of samples under a microscope, taking a plurality of areas for shooting, carrying out image recognition and counting the average diameter of the metal droplets, and finishing configuration when the average diameter of the droplets is within the range of 1-30 mu m and the average length-diameter ratio is more than 1.5 to obtain the uniformly mixed composite thermal interface material.

As shown in fig. 2, the method may include, for example, operations S201-S203.

In S201, a liquid metal and a surface modifier are added to the dispersion liquid to be stirred and dispersed, and a micrometer to millimeter-sized metal droplet after surface treatment is formed.

The dispersion is selected from ethanol, ethyl acetate, chlorobenzene, propanol or hexane.

Magnetic stirring is adopted for stirring dispersion, the rotating speed is 500-.

In the invention, the surface of the metal droplet can be treated by adding a surface modifier, and the surface modifier can form an adaptive film on the surface of the metal micro-nano droplet, wherein the surface modifier can comprise one or more of 3-mercapto-N-nonyl propionamide, 1-dodecyl mercaptan, mercapto-undecyl amine hydrochloride, titanate and isocyanate. By processing the surface of the metal liquid drop, the liquid drops can be prevented from being fused with each other, and meanwhile, the combination of the metal liquid drop and a silicon-free matrix material can be effectively promoted.

At S202, the supernatant is removed after stabilization, resulting in a precipitate and dried.

In the present invention, the drying method may be, for example: and (3) putting the micro-nano metal drops with the supernatant removed into a vacuum drying oven, wherein the drying temperature is 60-80 ℃, and the drying time is 1-6 h.

And S203, adding a silicon-free matrix material into the dried metal droplets, carrying out centrifugal shearing mixing under the condition of vacuum pumping, wherein the rotating speed ranges from 800 and 2500rpm, gradually increases from small to large according to 100rpm, and each rotating speed is operated for 1-5min until the metal droplets are uniformly mixed. In the present invention, the centrifugal shear mixing method is a planetary mixer. And (3) observing a small amount of samples under a microscope, taking a plurality of areas for shooting, carrying out image recognition and counting the average diameter of the metal liquid drop, and completing the configuration when the average diameter of the liquid drop is within the range of 1-30 mu m and the average length-diameter ratio is more than 1.5 to obtain the uniformly mixed composite thermal interface material. The thermal conductivity of the material is higher, and the heat dissipation effect is better than that of the composite material containing metal liquid drops in other particle size ranges.

The liquid metal silicon-free thermal interface material can be prepared by the following steps: stirring at 1500rpm by using a planetary stirrer, and carrying out vacuum pumping treatment in the process, wherein the pressure is 1Pa, so that micron-millimeter metal droplets are preliminarily mixed with a silicon-free matrix material; then gradually increasing the rotating speed of the planetary stirrer, and increasing the rotating speed by 100rpm each time to ensure that the micron-millimeter-magnitude metal liquid drop and the silicon-free matrix material are gradually and fully mixed; and finally, when the planetary stirrer is increased to about 2300rpm, a small amount of samples are taken to be observed under a microscope, a plurality of areas are selected for image recognition, and the average diameter of the metal droplets is counted, and the experimental result shows that when the rotating speed of the planetary stirrer is about 2300rpm to 2700rpm, the diameter range of the droplets is about 1 mu m to 30 mu m, and the average length-diameter ratio is more than 1.5, the configuration is completed, and the liquid metal silicon-free thermal interface material is obtained.

In order to more clearly illustrate the above-mentioned preparation method, specific examples are described below. Wherein, the thermal conductivity is measured by adopting a DRL-III type thermal conductivity meter, and the test method is in accordance with ASTM D5470 standard.

Example 1

The embodiment provides a preparation method of a silicon-free liquid metal composite thermal interface material, which comprises the following steps:

step 1, adding 20g of liquid metal gallium indium alloy into 50mL of ethanol, adding 0.1g of surface modifier 3-mercapto-N-nonyl propionamide, and stirring for 5min by using a magnetic stirrer.

And 2, stably removing the upper-layer dispersion liquid, and drying the metal liquid drops subjected to surface treatment in a drying oven at the temperature of 60 ℃ for 1 h.

Step 3, adding 0.75g of silicon-free matrix material epoxy resin after drying, stirring at 1500rpm by adopting a planetary stirrer, and carrying out vacuum pumping treatment along with the process at the pressure of 1Pa so as to preliminarily mix the micrometer-millimeter metal liquid drops and the silicon-free matrix material; then gradually increasing the rotating speed of the planetary stirrer, and increasing the rotating speed by 100rpm each time to fully mix the micron-millimeter metal liquid drops and the silicon-free matrix material; finally, when the planetary mixer is increased to about 2300rpm, a small amount of samples are taken and observed under a microscope, a plurality of areas are selected for shooting, image recognition is carried out, the average diameter of the metal droplets is counted, the average diameter of the metal droplets is found to be 37 μm, when the rotating speed of the planetary mixer is continuously increased to 2500rpm, a small amount of samples are taken and observed, shot and counted under the microscope, the diameter range of the droplets is about 16 μm (as shown in figure 1), and the configuration of the thermal interface material is completed. As can be seen from fig. 1, the metal droplets have different sizes and forms, and the thermal interface material exhibits multi-scale and multi-state characteristics.

The thermal conductivity of the thermal interface material is 14.0W/m.K and the thermal resistance under the pressure of 10Psi is 0.0039K/W.

Example 2

The embodiment provides a method for preparing a liquid metal silicon-free thermal interface material, which is different from the embodiment 1 in that:

the liquid metal content is increased to 22g, the epoxy resin is replaced by polyurethane, and the rest conditions are unchanged.

The thermal conductivity of the thermal interface material is detected to be 13.6W/m.K, and the thermal resistance under the pressure of 10Psi is detected to be 0.0045K/W.

Example 3

The embodiment provides a method for preparing a liquid metal silicon-free thermal interface material, which is different from the embodiment 1 in that:

the liquid metal is replaced by bismuth indium tin alloy, the surface modifier is replaced by 0.15g of 1-dodecanethiol, the surface modifier is replaced by ethyl acetate, and the rest conditions are unchanged.

The thermal conductivity of the thermal interface material is detected to be 13.3W/m.K, and the thermal resistance under the pressure of 10Psi is detected to be 0.0048K/W.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.