CN112111153A - Oriented heat conduction material and preparation method and application thereof - Google Patents

Abstract

The present invention provides a directional thermally conductive material and a preparation method and application thereof. The directional thermally conductive material comprises a polymer matrix and anisotropic thermally conductive fibers filled in the polymer matrix. The directional thermally conductive material of the embodiment of the present invention has at least the following beneficial effects: the directional thermally conductive material utilizes anisotropic thermally conductive fillers to form directionally arranged thermally conductive fibers, and these thermally conductive fibers are also oriented along their alignment direction on the microscale, so that the thermally conductive fibers are oriented along their alignment direction. The material can utilize the anisotropy of the filler to the greatest extent, and the orientation degree of the filler has been greatly improved. It can achieve higher thermal conductivity with a lower ratio of anisotropic thermally conductive filler, and is further adapted to the rapid development of electronic devices. Comes cooling needs.

Description

Oriented thermally conductive material, preparation method and application thereof

technical field

The present invention relates to the technical field of thermal management materials, in particular to a directional thermally conductive material and a preparation method and application thereof.

Background technique

With the rapid development of electronic technology and the continuous rise of 5G communication, Internet of Things, new energy vehicle electronics, smart wearable devices and other fields, the power density and integration of related electronic devices are increasing. When the electronic device is working, a considerable part of the power loss is exported as heat, and the heat dissipation of the electronic device will directly lead to the rapid rise of the temperature of the electronic device and the increase of thermal stress, which will affect the reliability, safety and service life of the electronic device. pose a serious threat. This also makes people in the industry gradually realize that whether the thermal management material system can break through to a certain extent determines whether the electronic device can be further developed.

The heat transfer method of the traditional thermal management material system is mainly to diffuse the heat from the point of generation to the surface of the heat sink. However, as the size of electronic devices continues to shrink, the waviness and The roughness gradually becomes larger, and the pores between the interfaces at the microscale have a great influence on the thermal conduction of the thermal management material system. In order to reduce the interface thermal resistance as much as possible, thermal interface materials are introduced between the power components such as chips and the interface of the heat sink to fill their air voids.

In order to ensure the long-term stability of electronic devices, thermal interface materials not only have requirements on thermal conductivity, but also must meet certain standards for mechanical strength, electrical insulation and other properties. High polymer materials have become the most widely used thermal interface materials due to their good electrical insulation properties, corrosion resistance, easy processing, and high mechanical strength. However, the thermal conductivity of most polymers is very low, and polymer materials are often used as the matrix, and high thermal conductivity fillers are added to increase the thermal conductivity of thermal interface composites.

The thermal conductivity in the axial or in-plane direction of anisotropic high thermal conductivity fillers can reach hundreds of W/m K, such as carbon fibers and carbon nanotubes with one-dimensional structure, boron nitride (BN) with two-dimensional structure. ), graphite, graphene, etc. If these anisotropic, highly thermally conductive fillers can be oriented in the polymer matrix, the thermally conductive material can have higher thermal conductivity in a specific direction. However, the degree of orientation that can be achieved by the existing orientation process is not high, and high thermal conductivity must be obtained through a higher proportion of fillers. Therefore, it is necessary to provide a thermally conductive material that can achieve higher thermal conductivity with a lower filler ratio.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a directional thermal conductivity material capable of achieving higher thermal conductivity with a lower filler ratio, and a preparation method and application thereof.

In a first aspect, an embodiment of the present invention provides a directional thermally conductive material, the directional thermally conductive material includes a polymer matrix and anisotropic thermally conductive fibers filled in the polymer matrix, wherein the anisotropic thermally conductive fibers are in the polymer matrix Alignment, the anisotropic thermally conductive fibers are oriented in the direction of the alignment.

The directional thermally conductive material of the embodiment of the present invention has at least the following beneficial effects:

The directional thermally conductive material utilizes anisotropic thermally conductive fillers to form directionally arranged thermally conductive fibers, and these thermally conductive fibers are also oriented along their arrangement direction on the microscale, so that the thermally conductive material can utilize the anisotropy of the filler to the greatest extent, and the orientation of the filler The degree of thermal conductivity has been greatly improved, and higher thermal conductivity can be achieved with a lower ratio of anisotropic thermally conductive fillers, which is further adapted to the heat dissipation needs brought about by the rapid development of electronic devices.

According to the directional thermally conductive material of some embodiments of the present invention, the anisotropic thermally conductive fibers are made of raw materials including anisotropic thermally conductive fillers, and the raw materials may specifically include:

(a) anisotropic thermally conductive filler;

(b) at least one of thermosetting resin, silicone rubber, and phase change material.

Anisotropic thermally conductive fillers refer to one-dimensional or two-dimensional thermally conductive fillers with anisotropy. One-dimensional thermally conductive fillers can include but are not limited to carbon nanowires, carbon nanotubes, etc., and two-dimensional thermally conductive fillers can include but are not limited to sheets Layered boron nitride, lamellar graphene, expanded graphite, etc. In order to further improve the properties of anisotropic thermally conductive fillers, such as adhesive properties, thermal stability, etc., these anisotropic thermally conductive fillers can be subjected to surface modification treatment, such as chemical grafting, coupling agent treatment, ultrasonic, microwave treatment , The way of acid-base treatment. Thermosetting resins can include but are not limited to phenolic resins, epoxy resins, amino resins, unsaturated polyesters, etc. Silicone rubber is mainly composed of silicon-oxygen chains containing methyl groups and a small amount of vinyl groups, and phase change materials can include but not limited to Limited to paraffin, fatty acid-alcohol, high density polyethylene, polyethylene glycol, etc. The thermosetting resin and silicone rubber contained in the anisotropic thermally conductive fiber can ensure the electrical insulation of the thermally conductive material, while the phase change material can strengthen its thermal conductivity to a certain extent.

According to the directional thermally conductive material of some embodiments of the present invention, based on the total mass of the anisotropic thermally conductive fibers, the mass fraction of the anisotropic thermally conductive filler is 5-20%. Since the directional thermally conductive material has extremely high orientation, the anisotropic thermally conductive filler in the material can obtain higher thermal conductivity with a lower content, thereby reducing the material cost. Of course, it is obvious that if the content of the thermally conductive filler is higher, the directional thermally conductive material will inevitably bring about higher thermal conductivity.

According to the directional thermally conductive material of some embodiments of the present invention, the raw materials for preparing the polymer matrix include:

(c) particulate thermally conductive filler;

(d) At least one of thermosetting resin and silicone rubber.

In the directional thermally conductive material, thermosetting resin and/or silicone rubber is used as the main support material to ensure that the directional thermally conductive material has sufficient mechanical strength. Among them, granular thermally conductive fillers can also be added, so that the entire directional thermally conductive material can have a certain thermal conductivity along the axial, radial and circumferential directions of the anisotropic thermally conductive fibers, so that the overall thermal conductivity of the directional thermally conductive material can be increased. improved. The particulate thermally conductive filler can be an optional thermally conductive filler in particulate form, including, but not limited to, aluminum oxide, silicon oxide, aluminum nitride, silicon nitride, zinc oxide, and the like.

According to the directional thermally conductive material of some embodiments of the present invention, the mass fraction of the particulate thermally conductive filler is 5-80% based on the total mass of the polymer matrix. Considering the improvement of the overall thermal conductivity of the directional thermally conductive material, the above content of particulate thermally conductive filler is mixed into the polymer matrix.

According to the directional thermally conductive material of some embodiments of the present invention, based on the total volume of the directional thermally conductive material, the volume fraction of anisotropic thermally conductive fibers is 20-70%. The anisotropic thermally conductive fillers on the microscopic scale in the anisotropic thermally conductive fibers have good orientation, which greatly improves the axial thermal conductivity of the anisotropic thermally conductive fibers. thermal conductivity.

According to the directional thermally conductive material of some embodiments of the present invention, the radius of the anisotropic thermally conductive fibers is 10-500 μm, and the aspect ratio of the anisotropic thermally conductive fibers is not less than 10. Setting the aspect ratio of the thermally conductive fibers above 10 can effectively ensure the high orientation of the one-dimensional or two-dimensional fillers in the anisotropic thermally conductive fibers. The larger the aspect ratio, the better the orientation effect of the one-dimensional or two-dimensional fillers on the microscopic scale. , the axial thermal conductivity of the directional thermal conductivity material is better. The micron-diameter thermally conductive fiber can ensure that the thermosetting resin, silicone rubber, phase change material and other polymers in it have a good forming orientation effect, which is the same as the orientation of the filler, bringing higher orientation to the thermally conductive fiber as a whole.

In a second aspect, an embodiment of the present invention provides a preparation method of a directional thermally conductive material, the preparation method comprising the following steps:

S1: filling the first slurry in the directionally arranged through holes in the template, and curing the first slurry in the through holes to obtain anisotropic thermally conductive fibers;

S2: removing the template, wrapping the second slurry on the anisotropic thermally conductive fiber, and curing to obtain a directional thermally conductive material;

Wherein, the first slurry includes anisotropic thermally conductive filler, the second slurry includes a polymer matrix material, the diameter of the through hole is 10-500 μm, and the aspect ratio of the through hole is not less than 10.

The preparation method of the directional thermally conductive material according to the embodiment of the present invention has at least the following beneficial effects:

The method adopts a template method to prepare a thermally conductive material, uses a template with large aspect ratio through holes to obtain a large number of highly oriented anisotropic thermally conductive fibers, and then solidifies with a second slurry containing a polymer matrix material to form a directional thermally conductive material. Through holes with small diameter and high aspect ratio can promote the orientation of anisotropic thermally conductive fillers, and at the same time, the polymer materials used in them may also have a certain orientation, which may cause the slurry to require greater pressure when filling, However, on the other hand, the overall thermal conductivity material can also have a higher orientation, and a higher thermal conductivity can be obtained with a lower filler ratio compared to the existing thermal conductivity material.

According to the preparation method of the directional thermally conductive material according to some embodiments of the present invention, when the template is removed, the anisotropic thermally conductive fibers are fixed between the upper cover plate and the lower cover plate of the mold. Since the through-holes used in this embodiment to obtain anisotropic thermally conductive fibers have a high aspect ratio, the fibers may collapse and bend without support, so it needs to pass through the upper cover plate and the lower cover plate. The fixing makes the anisotropic thermally conductive fibers oriented in the template without bending, and then the subsequent step of filling the second slurry is performed.

According to the method for preparing a directional thermally conductive material according to some embodiments of the present invention, the template used can be prepared from materials such as ice, anodized aluminum, silica, polycarbonate or polyester according to actual use requirements.

In a third aspect, an embodiment of the present invention provides an electronic device comprising the above-mentioned directional thermally conductive material. In electronic devices, the above-mentioned directional thermal conductive materials are used for heat dissipation or auxiliary heat dissipation. Because the directional thermal conductivity material has high axial thermal conductivity, its temperature rise can be effectively controlled when used in electronic devices, so as to avoid long-term high temperature from affecting the working reliability, safety and service life of electronic devices.

Description of drawings

FIG. 1 is a side view of a mold used in the method for producing a directional thermally conductive material of Example 1 of the present invention.

Detailed ways

The concept of the present invention and the technical effects produced will be clearly and completely described below with reference to the embodiments, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts are all within the scope of The scope of protection of the present invention.

Example 1

This embodiment provides a directional thermally conductive material, the directional thermally conductive material includes a polymer matrix and anisotropic thermally conductive fibers filled in the polymer matrix. The polymer matrix included 40 wt% spherical alumina and 60 wt% silicone rubber, and the anisotropic thermally conductive fibers included 5 wt% carbon fiber and 95 wt% paraffin wax. The volume fraction of the anisotropic thermally conductive fibers in the total volume of the directional thermally conductive material is 30%. The anisotropic thermally conductive fibers are oriented in the polymer matrix, and the anisotropic thermally conductive fibers are oriented along the direction in which they are oriented.

The mold used in the preparation process of the directional thermally conductive material is shown in FIG. 1 . Referring to FIG. 1 , it is a side view of the mold according to an embodiment of the present invention. The mold is a cylindrical structure, including a lower cover plate 101, a side wall 102 is fixed along the outer edge of the lower cover plate 101, the side wall 102 wraps the template 110, and the height of the template 110 is slightly lower than the height of the side wall 102, Therefore, after the template 110 is loaded into the cavity enclosed by the side wall 102 and the lower cover plate 101 , a cavity 120 is still formed in the upper part. At the upper end of the side wall 102, the upper cover plate 103 can be in contact therewith and penetrate deep into the cavity 120 to seal it. The template 110 is provided with uniformly distributed cylindrical through holes 111 , the diameter d of the through holes 111 is 200 μm, and the length L of the through holes 111 along its extending direction is 3 cm, which is perpendicular to the plane of the lower cover 101 . The sum of the cross-sectional areas of the through holes 111 is 20% of the cross-sectional area of the template 110 . The template 110 is an anodized aluminum template, and the upper cover 103 , the side wall 102 and the lower cover 101 are made of stainless steel. Both the upper cover 103 and the lower cover 101 can be disassembled, and sealing rings (not shown in the figure) are also provided on the upper cover 103 and the lower cover 101 to ensure air tightness.

The preparation method of the directional thermally conductive material is as follows:

Step 1: Mix the paraffin wax and the carbon fiber pretreated with the coupling agent KH550 according to the above ratio to form the first slurry, and mix the silicone rubber and the spherical alumina treated with the coupling agent KH550 according to the above ratio to form the second slurry material;

Step 2: Keep the temperature of the first slurry above the temperature of the phase transition point of the paraffin wax, inject it into the cavity 120, install the upper cover 103, and then vacuumize and pressurize, so that the first slurry enters the channel of the template 110. inside the hole 111, and fill the through hole 111;

Step 3: removing the excess first slurry on the surface of the template 110, making the upper cover plate 103 fit on the upper surface of the template 110, cooling to solidify the paraffin, and obtaining anisotropic thermally conductive fibers;

Step 4: Remove the sidewall 102 of the mold, soak the upper cover 103, the lower cover 101 and the template 110 of the mold in sodium hydroxide solvent, dissolve and remove the template 110, use ethanol and deionized water to fix the upper cover The anisotropic thermally conductive fibers between the plate 103 and the lower cover plate 101 are cleaned and dried under vacuum conditions;

Step 5: Completely soak the upper cover 103 and the lower cover 101 and the anisotropic thermally conductive fibers fixed between the upper cover 103 and the lower cover 101 into the second slurry, and replace the upper cover 103 and the lower cover After the plate 101 is installed on the side wall 102, the anisotropic thermally conductive fibers in the mold are covered with a second slurry that replaces the template 110, and the mold is taken out and heated to completely solidify the second slurry;

Step 6: Remove the side wall 102, the upper cover plate 103 and the lower cover plate 101 to obtain a directional thermally conductive material.

The small diameter and high aspect ratio through holes of the template used in this embodiment can promote the anisotropic thermally conductive fillers to be oriented along the through holes on both macro and micro scales during the pressurization process. At the same time, this The aspect ratio and small diameter can also make the polymer material in it have a certain orientation, so that the overall orientation of the thermally conductive material is higher, and compared with the existing thermally conductive material, a lower filler ratio can be obtained. High thermal conductivity.

Example 2

This embodiment provides a directional thermally conductive material, the directional thermally conductive material includes: a polymer matrix and anisotropic thermally conductive fibers filled in the polymer matrix. The polymer matrix includes 50wt% spherical silica and 50wt% silicone rubber, and the anisotropic thermally conductive fibers includes 10wt% boron nitride and 90wt% silicone rubber. The volume fraction of the anisotropic thermally conductive fibers in the total volume of the directional thermally conductive material is 30%. The anisotropic thermally conductive fibers are oriented in the polymer matrix, and the anisotropic thermally conductive fibers are oriented along the direction in which they are oriented.

The preparation method of the directional thermally conductive material is as follows:

Step 1: Mix the silicone rubber and the boron nitride treated with the coupling agent KH550 into a first slurry, and mix the silicone rubber and the spherical silica treated with the coupling agent KH550 into the second slurry;

Step 2: Add the first slurry to the upper cavity of the mold loaded with the anodized aluminum template, install the upper cover, and then vacuumize and pressurize, so that the first slurry enters the through holes of the template and fills up through hole;

Step 3: Remove the excess first slurry on the surface of the template, make the upper cover fit the upper surface of the template, and heat the silicone rubber to semi-cure (to facilitate re-softening and cross-linking with the polymer matrix material when heated in the subsequent step 5) react and combine) to obtain anisotropic thermally conductive fibers;

Step 4: Remove the sidewall of the mold, immerse the mold and the template as a whole in sodium hydroxide solution, remove the template, clean with ethanol and deionized water, and then vacuum dry;

Step 5: Completely soak the upper cover plate and the lower cover plate and the anisotropic thermally conductive fibers fixed between the upper cover plate and the lower cover plate into the second slurry, and the upper cover plate and the lower cover plate are in the second slurry. After the cover plate is installed on the side wall, the mold is taken out and heated to completely cure the polymer matrix;

Step 6: Remove the side walls and the upper and lower cover plates to obtain directional thermal conductivity materials.

Thermal conductivity test

Comparative Example 1

The comparative example provides a thermally conductive material, the thermally conductive material includes a polymer matrix and thermally conductive fibers, the volume ratio of the polymer matrix to the thermally conductive fibers is 4:1, and the polymer matrix includes 40wt% spherical alumina and 60wt% silicone rubber , the thermally conductive fibers include 5wt% carbon fiber and 95wt% paraffin. The preparation method of the thermally conductive material is that the above-mentioned raw materials are simply mixed and then solidified and shaped.

Comparative Example 2

The comparative example provides a thermally conductive material, the thermally conductive material includes a polymer matrix and a thermally conductive fiber, the volume ratio of the polymer matrix to the thermally conductive fiber is 4:1, and the polymer matrix includes 50wt% spherical silica and 50wt% silicone rubber , the thermally conductive fibers include 10wt% boron nitride and 90wt% silicone rubber. The preparation method of the thermally conductive material is that the above-mentioned raw materials are simply mixed and then solidified and shaped.

The steady-state method is used to determine the thermal conductivity of the directional thermally conductive material along the axial direction of the anisotropic thermally conductive fiber. The specific test method is as follows: place the directional thermally conductive material between the instrument bars of the resistance conductivity measuring instrument, and after establishing a stable heat flow, The temperature in the meter strip is measured at two or more locations along its axial direction, and the temperature difference is calculated to determine the thermal conductivity of the directional thermally conductive material along its axial direction.

The thermal conductivity of the thermally conductive materials prepared in Examples 1 to 2 and Comparative Examples 1 to 2 was used to measure the thermal conductivity according to the above method, and the results are shown in Table 1.

Table 1. Thermal Conductivity Measurement Results

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Thermal conductivity (W/m·k) 15.6 12.3 3.7 2.4

It can be seen from the above results that, compared with Comparative Examples 1 and 2, the thermal conductivity in the axial direction of the oriented thermally conductive material provided in the embodiment of the present invention has been significantly improved due to the good orientation effect achieved.

Example 3

This embodiment provides an electronic device, the electronic device includes a chip and a heat sink arranged in sequence, a heat transfer adhesive is sandwiched between the chip and the heat sink, and the heat transfer adhesive includes the directional thermally conductive material of Embodiment 1 . Using the directional thermal conductive material, the heat generated by the chip during operation can be quickly transferred to the heat sink to be dissipated, thereby effectively slowing down the temperature rise of the chip.

The present invention has been described in detail above in conjunction with the embodiments, but the present invention is not limited to the above-mentioned embodiments, and within the scope of knowledge possessed by those of ordinary skill in the technical field, various changes can also be made without departing from the purpose of the present invention. . Furthermore, the embodiments of the present invention and features in the embodiments may be combined with each other without conflict.

Claims (10)

1. The oriented heat conduction material is characterized by comprising a polymer matrix and anisotropic heat conduction fibers filled in the polymer matrix, wherein the anisotropic heat conduction fibers are aligned in the polymer matrix in an oriented mode, and the anisotropic heat conduction fibers are oriented along the direction of the aligned mode.

2. The oriented thermal conductive material of claim 1, wherein the anisotropic thermal conductive fiber is prepared from:

(a) an anisotropic thermally conductive filler;

(b) at least one of thermosetting resin, silicon rubber and phase change material.

3. The oriented heat conduction material according to claim 2, wherein the mass fraction of the anisotropic heat conduction filler is 5-20% based on the total mass of the anisotropic heat conduction fibers.

4. The oriented thermal conductive material of claim 1, wherein the polymer matrix is prepared from materials comprising:

(c) a particulate thermally conductive filler;

(d) at least one of thermosetting resin and silicone rubber.

5. The oriented thermal conduction material according to claim 4, wherein the mass fraction of the granular thermal conductive filler is 5-80% based on the total mass of the polymer matrix.

6. The oriented heat conduction material according to any one of claims 1 to 5, wherein the volume fraction of the anisotropic heat conduction fibers is 20-70% based on the total volume of the oriented heat conduction material.

7. The oriented heat conduction material according to any one of claims 1 to 5, wherein the radius of the anisotropic heat conduction fiber is 10 to 500 μm, and the aspect ratio of the anisotropic heat conduction fiber is not less than 10.

8. The preparation method of the oriented heat conduction material is characterized by comprising the following steps of:

s1: filling first slurry into through holes which are arranged in a template in an oriented mode, and curing the first slurry in the through holes to obtain anisotropic heat conducting fibers;

s2: removing the template, coating the anisotropic heat conduction fibers with second slurry, and curing to obtain an oriented heat conduction material;

the first paste comprises anisotropic heat conduction filler, the second paste comprises polymer matrix material, the diameter of the through hole is 10-500 mu m, and the length-diameter ratio of the through hole is not less than 10.

9. The method as claimed in claim 8, wherein in the step S2, the anisotropic thermal conductive fiber is fixed between an upper cover plate and a lower cover plate of the mold when the template is removed.

10. An electronic device comprising the oriented thermal conductive material of any one of claims 1 to 7.

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