CN115214202A - High-thermal-conductivity layered thermal interface material and preparation method thereof - Google Patents

Abstract

A preparation method of a layered thermal interface material with high thermal conductivity belongs to the field of thermal management materials. The invention relates to a high thermal conductivity, electrical, insulating and thermally conductive composite material for high-power electronic equipment. The composite material is composed of upper, middle and lower layers. The upper and lower layers have the same composition. The middle layer adopts high filling of four particle sizes, and the upper and lower layers adopt low filling of three particle sizes. The upper and lower layers have lower viscosity and are easier to fit the surface of the equipment. The higher the filling amount, the larger the viscosity, and the tighter connection between the particles, which can form more thermal conduction paths, thus achieving high thermal conductivity. Both the middle layer and the upper and lower layer composite materials are composed of the following mass ratios: 80-98wt% of thermally conductive filler, 0-10wt% of matrix, 1-5wt% of coupling agent (relative to the total mass of thermally conductive filler), and 1-5wt% of catalyst. The invention modifies fillers with different shapes and particle sizes, and calculates a ratio close to the optimal particle gradation on the basis of the Dinger-Funk tight packing model, and the thermal conductivity of the prepared material is as high as 8W·m ^{- 1} ·K- ¹ or more, the viscosity is moderate, and the cost is low, and it is suitable for industrial production and manufacturing.

Description

A kind of high thermal conductivity layered thermal interface material and preparation method thereof

technical field

The invention belongs to the field of thermal management materials, and more particularly relates to a thermal interface material with high thermal conductivity and a preparation process thereof.

Background technique

In recent years, with the rapid development of my country's intelligent equipment and mechanical equipment, the load and power consumption of various electronic equipment have continued to increase. High integration, small size and high power have become the development direction of various electronic devices.

However, while all kinds of equipment are miniaturized and the load is light, the heat dissipation problem is particularly important. There are two solid ^- solid interfaces between the electronic device and the heat sink. The actual contact area of the interface between the two is very small, and there are uneven ^gaps . It is filled with air, and the heat transfer enhancement between the two solid-solid interfaces is the weak link in the entire heat dissipation system. If the heat cannot be exported in time, the waste heat will accumulate in the small space inside the device, resulting in excessive local temperature and heat flow distribution. Problems such as unevenness will not only affect the normal operation of the device, but also increase the instability of the device during operation.

If the thermal interface material is filled in the gap between the electronic device and the heat sink, it can ensure the close contact between the two, and the heat generated when the device is working can be exported in time and effectively, so as to optimize the heat dissipation performance. It can be seen that the thermal interface material The performance of the components plays an important role in the heat dissipation effect of the components.

The Chinese invention patent with the patent authorization announcement number CN109486192B discloses a self-leveling high thermal conductivity and high temperature resistant thermal interface material and a preparation method thereof. Through the compounding of different particle sizes and different types of fillers, the silicone grease can be filled to the maximum extent to achieve a balance between thermal conductivity and viscosity. The final obtained self-leveling property is good, and the thermal conductivity is higher than 3.0W·m ^{- 1} · K ^-1 thermal interface material.

The Chinese invention patent with the patent authorization announcement number CN110204903B discloses a high thermal conductivity thermal conductive silicone grease and a preparation method thereof. , has the advantages of high thermal conductivity and good durability.

However, the above thermal greases have certain thermal conductivity or low viscosity, but none of them highlight the technical characteristics of high thermal conductivity and high fit with the equipment. At present, most devices are developing in the direction of miniaturization, high power and high heat flow. , the waste heat will accumulate in the small space inside the device, so it is necessary to develop a thermal interface material that has both high thermal conductivity and a high degree of bonding with the solid-solid interface of the heat-generating part and the heat-dissipating part of the device.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the purpose of the present invention is to provide a layered thermal interface material with high thermal conductivity, the thermal conductivity of which can reach more than 8W·m ^-1 ·K ^-1 , the process is simple, and the market demand can be met .

For achieving the above object, the present invention provides the following technical solutions:

A high thermal conductivity layered thermal interface material is characterized in that the material is composed of the following components in mass ratio:

Thermally conductive filler: 80-98wt%;

Matrix: 0-10wt%;

Coupling agent: 1-5wt%;

Catalyst 1-5wt%.

Further, the thermally conductive fillers are divided into upper, middle and lower layers, wherein the upper and lower layers of fillers are composed of the following three types of fillers:

The first type of thermal conductive filler 30-60wt%;

The second type of thermal conductive filler 40-60wt%;

The third type of thermal conductive filler 5-20wt%;

The particle size of the first type of thermally conductive filler is 50-100 microns, the second type is 3-20 microns, and the third type is 0.1-2 microns. The filler is aluminum oxide, boron nitride, aluminum nitride, zinc oxide, etc. or a mixture thereof, and the shape is spherical or nearly spherical; for most electrical appliances, it has been found that the filling amount of aluminum oxide is preferably 30-50 wt%, and the filler of aluminum nitride is preferably 30-50 wt%. The filling amount is preferably 40-60 wt%.

Further, the intermediate layer thermally conductive filler is composed of the following four types of fillers:

The first type of thermal conductive filler 30-50wt%;

The second type of thermal conductive filler 0-20wt%;

The third type of thermal conductive filler is 20-40wt%;

The fourth type of thermal conductive filler 0-20wt%;

The middle layer and the upper and lower layers have similar fillers, wherein the particle size of the first type of filler is 50-100 microns, the second type is 20-40 microns, the third type is 1-3 microns, and the fourth type is 0.1-0.3 microns. The filler can be aluminum oxide, boron nitride, aluminum nitride, zinc oxide, etc. or a mixture thereof, and the shape is spherical or nearly spherical, and the total filling amount of each filler in the intermediate layer is between 40-60 wt%.

Further, the upper and lower layer substrates and the intermediate layer substrates are one or more of polyethylene, epoxy resin, acrylic, polyurethane or silicone oil, and have significantly different hardness compared with the intermediate layer. If the substrate is a liquid with the highest viscosity, Fortunately, 90-1000cps.

Further, the coupling agent is 3-(2,3-glycidoxy)propyltrimethoxysilane, vinyltrimethoxyethoxysilane, γ-methacryloyloxypropyltrimethoxysilane One or more of silanes, etc.; the catalysts are all platinum-based catalysts.

The above-mentioned preparation method of a layered thermal interface material with high thermal conductivity is divided into two steps:

P1: Firstly, the surface modification of the thermal conductive filler is carried out respectively, and the steps are as follows:

Step 1, first put a certain quality of thermally conductive fillers into a vacuum drying oven to dry to remove surface moisture and impurities;

Step 2, according to the specific surface area possessed by each filler particle and the wettable area of the coupling agent itself, calculate the amount of deionized water and the amount of modifier required when preparing the coupling agent hydrolyzate;

Step 3, add deionized water according to the minimum water demand, and add acetic acid to adjust to acidity, add coupling agent respectively under constant vibration, stand for a period of time until the solution becomes clear to obtain a fully hydrolyzed coupling agent solution, and then add quantitative Water ethanol (alcohol-water mass ratio 95:5);

Step 4, respectively add the filler, first ultrasonically vibrate for 25-35min, then heat in a water bath and magnetically stir for 25-35min, then place it in a planetary ball mill for ball milling, and make the coupling agent in a state of high rotational speed and heating. The inorganic groups are fully bonded to the hydroxyl groups on the surface of the filler; after the ball milling, it is spread on a watch glass and placed in a constant temperature water bath for drying; finally, it is placed in a vacuum drying oven to dry;

P2: Mix filler and matrix to prepare thermal interface material, the steps are as follows:

All fillers are added to the matrix in batches according to the particle size and placed in a planetary mixer to fully stir, and then grinded for a long time until there are no small particles visible to the naked eye, and finally placed in a vacuum oven for vacuum defoaming to obtain a thermal interface material.

By adopting the above technical scheme, the above-mentioned various types, shapes, and particle sizes of filler powders are matched to produce a synergistic effect between the fillers, and a rich thermal conduction network is formed in the matrix. The amount of coupling agent can increase the affinity between the matrix and the filler, promote the dispersion of the filler in the matrix, and then uniformly fill the filler in the matrix by stirring and grinding, and the heat can be conducted through various paths in the thermal interface material body layer. Improved heat transfer efficiency. The composite material of the present invention is composed of upper, middle and lower layers, wherein the upper and lower layers have the same composition, the middle layer adopts high filling of four particle sizes, the upper and lower layers adopt low filling of three particle sizes, and the upper and lower layers have lower viscosity and are easier to fit equipment and On the surface of the intermediate layer, the filling amount of the intermediate layer is high and the viscosity is large, the particles are closely connected, and more heat conduction paths can be formed. The prepared layered composite material has high thermal conductivity and good flexibility, and has strong practical value. .

To sum up, by adopting the above technical scheme, the prepared thermal interface material has moderate viscosity, good thermal conductivity, and thermal conductivity of more than 8W·m ^-1 ·K ^-1 .

The present invention includes at least one of the following beneficial technical effects: First, by mixing and matching filler powders of different types and particle sizes, the present invention disperses evenly in the matrix to form rich heat-conducting network chains, thereby achieving better heat dissipation On this basis, a new layered structure thermal interface material is designed. The middle layer is filled with four particle sizes, and the connection between the particles is tight and the viscosity is large, which can form more heat conduction paths, so as to achieve high thermal conductivity; The layer is low-filled with three particle sizes, and the viscosity is low at low filling levels, which makes it easier to fit the surface of the device and connect the high-fill interface layer.

Second, based on the different particle sizes of various fillers and their own properties, the appropriate amount of coupling agent is theoretically calculated, which is beneficial to its dispersion in the matrix. The modified filler powder can effectively interconnect with the matrix, which can reduce The pores and air inside the material improve the compatibility and affinity of the two, thereby reducing the contact thermal resistance between the interfaces and improving the thermal conductivity.

Thirdly, the purpose of using ceramics as fillers is to prepare high thermal conductivity, electrical insulating thermal interface materials, which can be applied to occasions with high requirements on insulating properties, and the layered thermal interface materials prepared by the present invention can be thick or thin, and the preparation process is also It is relatively simple and can be applied to different electronic devices.

Description of drawings

FIG. 1 is a schematic diagram of the heat transfer principle of a thermal interface material and a schematic diagram of a layered composite material.

Figure 2 is a SEM image of the thermal interface material.

Note: a, b, c are implementation case 10; d, e, f are implementation case 13

Figure 3 is accompanied by a particle size distribution plot of the densely packed model.

Table 1: Thermal property data of the prepared composites.

Detailed ways

The following describes the implementation case of the present invention in detail

Implementation Case 1

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second and third types of fillers are spherical or nearly spherical in shape, the volume ratio of the third type: the second type: the first type of filler is 5:35:60, and the volume filling amount of the filler is 76vol% , the thermal conductivity of the material was finally measured to be 4.40W·m ^-1 ·K ^-1 .

Implementation case 2

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second and third types of fillers are spherical or nearly spherical in shape, the volume ratio of the third type: the second type: the first type of filler is 5:35:60, the filling amount is 78vol%, and the material The thermal conductivity was 4.86 W·m ⁻¹ ·K ⁻¹ .

Implementation Case 3

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second and third types of fillers are spherical or nearly spherical in shape, the volume ratio of the third type: the second type: the first type of filler is 5:35:60, the filling amount is 80vol%, and the heat The conductivity is 5.65W·m ^-1 ·K ^-1 .

Implementation Case 4

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second and third types of fillers are spherical or nearly spherical in shape, the volume ratio of the third type: the second type: the first type of filler is 5:35:60, the filling amount is 82vol%, and the heat The conductivity is 6.60W·m ^-1 ·K ^-1 .

Implementation Case 5

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second and third types of fillers are spherical or nearly spherical in shape, the volume ratio of the third type: the second type: the first type of filler is 12:25:63, the filling amount is 82vol%, and the heat The conductivity is 6.10W·m ^-1 ·K ^-1 .

Implementation Case 6

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second and third types of fillers are spherical or nearly spherical in shape, the volume ratio of the third type: the second type: the first type of filler is 15:25:60, the filling amount is 82vol%, and the heat The conductivity is 6.30W·m ^-1 ·K ^-1 .

Implementation Case 7

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second and third types of fillers are spherical or nearly spherical in shape, the volume ratio of the third type: the second type: the first type of filler is 15:25:60, the filling amount is 84vol%, and the heat The conductivity is 7.21W·m ^-1 ·K ^-1 .

Implementation Case 8

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second and third types of fillers are spherical or nearly spherical in shape, the volume ratio of the third type: the second type: the first type of filler is 15:25:60, the filling amount is 85vol%, and the heat The conductivity is 7.62W·m ^-1 ·K ^-1 .

Implementation Case 9

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second and third types of fillers are spherical or nearly spherical in shape, the volume ratio of the third type: the second type: the first type of filler is 15:25:60, the filling amount is 86vol%, and the heat The conductivity is 7.90W·m ^-1 ·K ^-1 .

Implementation Case 10

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second and third types of fillers are spherical or nearly spherical in shape, the volume ratio of the third type: the second type: the first type of filler is 10:35:55, the filling amount is 84vol%, and the heat The conductivity is 7.27W·m ^-1 ·K ^-1 .

Implementation Case 11

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second and third types of fillers are spherical or nearly spherical in shape, the volume ratio of the third type: the second type: the first type of filler is 10:35:55, the filling amount is 85vol%, and the heat The conductivity is 8.25W·m ^-1 ·K ^-1 .

Implementation Case 12

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second, third and fourth types of fillers are spherical or nearly spherical in shape, and the volume ratio of the fourth type: the third type: the second type: the first type of filler is 13:17:37 : 33, the filling amount was 85 vol%, and the thermal conductivity was 8.10 W·m ^-1 ·K ^-1 .

Implementation Case 13

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second, third and fourth types of fillers are spherical or nearly spherical in shape, and the volume ratio of the fourth type: the third type: the second type: the first type of filler is 10:35:10 : 45, the filling amount is 85vol%, and the thermal conductivity of the material is 8.42W·m ^-1 ·K ^-1 .

Implementation Case 14

A thermal interface material composite with high thermal conductivity includes a matrix, a thermally conductive filler, and a coupling agent. Among them, the first, second, third and fourth types of fillers are spherical or nearly spherical in shape, and the volume ratio of the fourth type: the third type: the second type: the first type of filler is 10:35:20 : 35, the filling amount was 85 vol%, and the final measured thermal conductivity was 7.92 W·m ^-1 ·K ^-1 .

The thermal properties of the thermal interface materials prepared in Examples 1-14 were tested, and the results are shown in Table 1.

Taking Example 10 as the upper and lower layers, and 13 as the intermediate layer, a layered thermal interface material was finally obtained by compaction, and its thermal conductivity was over 8W·m ^-1 ·K ^-1 .

其中，在复合导热粉体填料体系中Dmax＝170，Dmin＝0.15，n＝0.37，U(Dp)的值由Dp取值得到，如下表2所示：Calculation case of the compact packing model: Three fillers with different particle size distribution ranges are selected, and three fillers with D ₅₀ of 60 μm, 3 μm and 300 nm are used for multi-scale mixing and compounding. The process is as follows: First, determine the distribution range of the particle size of the thermally conductive powder filler: the distribution range of the 300nm particle size is [0.12, 2], the distribution range of the 3μm particle size is [1.6, 10.0], 60μm The particle size distribution range is [3, 140]. Then, the Dinger-Funk closest-packed equation

Among them, in the composite thermally conductive powder filler system Dmax=170, Dmin=0.15, n=0.37, the value of U(Dp) is obtained from the value of Dp, as shown in Table 2 below:

Therefore, it can be concluded that the volume of fillers with three different particle sizes of 20 μm, 6 μm and 2 μm in the total composite thermally conductive powder filler is 100-37=63(%), 37-12=15(%), 12-0= 12 (%). Finally, the volume filling amount of three kinds of thermally conductive powder fillers with different particle sizes is obtained, and the formula is as follows: the first type of filler is 63vol%, the second type of filler is 15vol%, and the third type of filler is 12vol%.

Table 1 Thermal properties data of the prepared composites

Table 2 U(Dp) calculated by different Dp

Claims (7)

1. a preparation method of high thermal conductivity layered thermal interface material, is characterized in that thermal interface material is made up of following mass ratio components: Thermally conductive filler: 80-98wt%; Matrix: 0-10wt%; Coupling agent: 1-5wt%; Catalyst 1-5wt%. 2. The preparation method of the high thermal conductivity layered thermal interface material as claimed in claim 1, wherein the thermal interface material is composed of a thermally conductive filler and a matrix, and is divided into upper, middle and lower layers, wherein the upper and lower thermally conductive fillers are composed of the following: Three types of fillers are composed: The first type of thermally conductive filler is 30-60wt%; The second type of thermally conductive filler is 40-60wt%; The third type of thermal conductive filler 5-20wt%; The particle size of the first type of thermally conductive filler is 50-100 microns, the second type is 3-20 microns, and the third type is 0.1-2 microns; the fillers are alumina, boron nitride, aluminum nitride, zinc oxide or their mixtures, and the shape spherical or nearly spherical. 3 . The method for preparing a high thermal conductivity layered thermal interface material according to claim 2 , wherein the filling amount of the alumina is 30-50 wt %, and the filling amount of aluminum nitride is 40-60 wt %. 4 . 4. the preparation method of high thermal conductivity layered thermal interface material as claimed in claim 2 is characterized in that described intermediate layer thermally conductive filler is made up of following four types of thermally conductive fillers: The first type of thermal conductive filler is 30-50wt%; The second type of thermal conductive filler 0-20wt%; The third type of thermally conductive filler is 20-40wt%; The fourth type of thermal conductive filler is 0-20wt%; The middle layer and the upper and lower layers have similar fillers, wherein the particle size of the first type of filler is 50-100 microns, the second type is 20-40 microns, the third type is 1-3 microns, and the fourth type is 0.1-0.3 microns; the filler is oxidized Aluminum, boron nitride, aluminum nitride, zinc oxide or a mixture thereof, the shape is spherical or nearly spherical, and the total filling amount of each filler in the intermediate layer is between 40-60 wt%. 5. The layered thermal interface material with high thermal conductivity according to claim 2, characterized in that: the upper and lower layer substrates and the intermediate layer substrates are a kind of polyethylene, epoxy resin, acrylic acid, polyurethane or silicone oil Or more, it has a significantly different hardness compared with the intermediate layer, if the matrix is a liquid, the viscosity is 90-1000cps. 6. A high thermal conductivity thermal interface material according to claim 1, wherein the coupling agent is 3-(2,3-glycidoxy)propyltrimethoxysilane, vinyltrimethylsilane One or more of oxyethoxysilane and γ-methacryloyloxypropyltrimethoxysilane; the catalysts are all platinum-based catalysts. 7. a kind of preparation method of the layered thermal interface material with high thermal conductivity according to claim 2 is characterized in that being divided into two steps: P1: firstly, the surface modification of the thermally conductive filler is carried out respectively, and the steps are as follows: Step 1, first put a certain quality of filler into a vacuum drying oven to dry to remove surface moisture and impurities; Step 2, according to the specific surface area possessed by each filler particle and the wettable area of the coupling agent itself, calculate the amount of deionized water and the amount of modifier required when preparing the coupling agent hydrolyzate; Step 3, according to the minimum water demand, add deionized water, add acetic acid to adjust to acidity, add coupling agent under constant vibration, stand for a period of time and wait for the solution to become clarified to obtain a fully hydrolyzed coupling agent solution, and then add a quantitative Water ethanol, the mass ratio of alcohol to water is 95:5; Step 4, respectively add the thermally conductive fillers, first ultrasonically vibrate for 25-35min, then heat in a water bath and magnetically stir for 25-35min, then place it in a planetary ball mill for ball milling, and make the coupling under high rotational speed and heating. The inorganic group of the agent is fully bonded with the hydroxyl group on the surface of the thermally conductive filler; after the ball milling, it is spread on a watch glass and placed in a constant temperature water bath for drying; finally, the mixed filler is obtained by drying in a vacuum drying oven; P2: Mix filler and matrix to prepare thermal interface material, the steps are as follows: All fillers are added to the matrix in batches according to the particle size and placed in a planetary mixer to fully stir, and then grinded for a long time until there are no small particles visible to the naked eye, and finally placed in a vacuum oven for vacuum defoaming to obtain a thermal interface material.

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