COC / h-BN composite material with high thermal conductivity and low loss and preparation method thereof

Abstract

The invention relates to a high-thermal-conductivity and low-loss COC / h-BN composite material and a preparation method thereof. The COC / h-BN composite material comprises a cycloolefin copolymer matrix and h-BN particles distributed in the cycloolefin copolymer matrix, the volume content of the h-BN particles is 5 to 30 vol%.

Description

Technical Field

[0001] The present invention relates to a polymer composite microwave dielectric chip and its application field, and specifically relates to a high thermal conductivity and low loss COC / h-BN composite material and its preparation method, belonging to the technical field of dielectric chips. Background Art

[0002] High thermal conductivity composite materials usually consist of a resin matrix and a thermal conductivity enhancing phase. Boron nitride (BN) has unique electrical insulation properties, excellent thermal conductivity and chemical stability, and extremely low dielectric constant and thermal expansion coefficient, and is an ideal thermal conductivity filler.

[0003] At present, thermal conductive polymer materials can be roughly divided into two categories: intrinsic thermal conductive polymers and filled thermal conductive polymers. Currently, it is relatively difficult and costly to prepare intrinsic thermal conductive polymer materials. Filled thermal conductive polymer materials are prepared by adding high thermal conductivity fillers to a polymer matrix, which is currently the main method for preparing high thermal conductivity materials. Since the dielectric loss of the dielectric material will cause heat generation, high thermal conductivity materials also need to have extremely low dielectric loss. Currently, the resin matrix is mainly polytetrafluoroethylene (PTFE), polyphenylene oxide (PPO), polystyrene (PS) or polyimide (PI), but the high-frequency losses of PPO, PS and PI are relatively high. Although PTFE has extremely low dielectric loss, it itself is a soft and weak resin, and the mechanical properties of the composite material based on it are poor. Therefore, at present, the research on preparing composite materials that simultaneously take into account thermal conductivity, dielectric properties and mechanical properties is of great significance. Summary of the Invention

[0004] To this end, the present invention provides a high thermal conductivity and low loss COC / h-BN composite material and its preparation method.

[0005] On the one hand, the present invention provides a COC / h-BN composite material, including: a cycloolefin copolymer matrix, and h-BN particles distributed in the cycloolefin copolymer matrix; the volume content of the h-BN particles is 5-30 vol% (such as 5 vol%, 10 vol%, 15 vol%, 20 vol%, 25, 30 vol%)

[0006] In the present invention, the cycloolefin copolymer matrix COC is a special high-performance plastic, which belongs to one of the olefin polymers. COC has good transparency, good chemical stability and inertness, relatively low water absorption rate, has good strength and stiffness, while maintaining a certain toughness and is easy to process).

[0007] Preferably, the h-BN particles are flaky, with a diameter of 10-25 μm.

[0008] Preferably, the coefficient of thermal expansion of the COC / h-BN composite material is 17.73 to 55.88 ppm / °C.

[0009] Preferably, the dielectric constant of the COC / h-BN composite material is 2.46 to 3.12, and the dielectric loss is 3.681E-04 to 5.397E-04; The thermal conductivity of the COC / h-BN composite material in the X / Y direction is 0.208 to 0.766 W·m -1 ·K -1 , and the thermal conductivity in the Z direction is 0.302 to 1.204 W·m -1 ·K -1 .

[0010] On the other hand, the present invention provides a method for preparing a COC / h-BN composite material, comprising: (1) Mixing h-BN particles and a COC raw material to obtain an h-BN / COC mixture; (2) Granulating the h-BN / COC mixture to obtain h-BN / COC particles; (3) Subjecting the h-BN / COC particles to drying, hot pressing at high temperature to form the particles, and cooling treatment to obtain the COC / h-BN composite material.

[0011] Reaction mechanism of the present invention: During the granulation process, when the melt temperature reaches 220 to 240 °C (for example, 220 °C), the COC changes from a solid state to a rubber state, and the viscosity gradually decreases. The h-BN powder can be fully and uniformly mixed in the resin matrix without settling and agglomerating together. In addition, high temperature is more suitable for extrusion and subsequent processing and forming.

[0012] Preferably, in step (1), the purity of the h-BN particles > 99.9%; the mixing method is mechanical mixing and stirring; the temperature of the stirring and mixing is 20 to 30 °C, and the stirring time is 0.5 to 1 h.

[0013] Preferably, in step (2), the parameters of the granulation treatment include: first filling the h-BN / COC mixture into the feed port of a granulator, then subjecting it to high-temperature melting, then subjecting it to water bath cooling and forming, and finally subjecting it to cutting treatment; The temperature of the high-temperature melting is 220 to 240 °C; The temperature of the water bath cooling and forming is 0 to 25 °C.

[0014] Preferably, in step (3), the drying temperature is 100 to 110 °C, and the time is 6 to 8 hours; preferably, the drying temperature is 100 °C, and the drying time is 8 hours.

[0015] Preferably, in step (3), the temperature of the hot pressing is 150-220°C, the time is 0.5-1 hour, and the pressure is 160-180 MPa

[0016] Preferably, in step (3), the temperature of the cooling treatment is 0-25°C, and the cooling time is 6-10 hours, preferably 8 hours.

[0017] Advantages of the present invention: 1. The h-BN-COC thermally conductive composite material prepared by the method of the present invention has an improved thermal conductivity compared to the COC resin matrix, excellent thermal conductivity, and good mechanical properties; 2. The h-BN-COC thermally conductive composite material prepared by the method of the present invention has a low coefficient of thermal expansion and can be matched with copper electrodes; 3. The h-BN-COC thermally conductive composite material prepared by the method of the present invention has a low dielectric constant and a fast signal transmission speed; 4. The h-BN-COC thermally conductive composite material prepared by the method of the present invention has a low dielectric loss. Specific embodiments

[0018] The present invention will be further described below by the following embodiments. It should be understood that the following embodiments are only used to illustrate the present invention and do not limit the present invention.

[0019] In the present invention, a four-step method is used to prepare a composite material of h-BN particles and cyclo-olefin copolymer (COC). In the present invention, h-BN and COC are mixed, and the resulting composite material has a low dielectric loss, good mechanical properties, and can achieve a relatively precise regulation of the dielectric constant, and relatively excellent thermal conductivity.

[0020] The process of preparing the composite material of h-BN particles and cyclo-olefin copolymer (COC) by the four-step method is exemplarily described below.

[0021] Weigh h-BN (10μm / 25μm) and COC raw materials with a purity greater than 99.9%, and stir at room temperature for 2h by a micro mixer to fully and uniformly fill the h-BN powder into the COC particles.

[0022] Put the stirred h-BN / COC raw materials into the feed port of the granulator at a melt temperature of 220°C, and make it in an unfrozen molten state through high-temperature melting. After being cooled and formed by a water bath, put the formed raw material strip into a cutting machine to obtain h-BN / COC particles.

[0023] Put the h-BN / COC particles into an oven (for example, 110°C, dried for 8h), and take them out.

[0024] The dried h-BN / COC particles are formed by hot pressing at high temperature and then cooled at room temperature to obtain a composite material plate, thereby preparing a composite thermal conductive material.

[0025] In the present invention, a dilatometer (DIL 402C, NETZSCH Scientific Instruments GmbH) is used to measure the coefficient of thermal expansion of the obtained COC / h-BN composite material. The flexural strength of the obtained COC / h-BN composite material is 40 - 60 MPa.

[0026] In the present invention, a split dielectric resonator (SPDR) is used to measure that the dielectric constant of the obtained COC / h-BN composite material is 2.46 - 3.12, and the dielectric loss is 3.730E-04 - 5.397E-04.

[0027] In the present invention, a laser thermal conductivity meter (LFA-467, NETZSCH Scientific Instruments GmbH) is used to measure that the thermal conductivity of the obtained COC / h-BN composite material in the X / Y direction is 0.208 - 0.766 W·m -1 ·K -1 , and the thermal conductivity in the Z direction is 0.302 - 1.204 W·m -1 ·K -1 .

[0028] The following further gives examples to illustrate the present invention in detail. It should be understood that the following examples are only used to further illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the protection scope of the present invention. The specific process parameters and the like in the following examples are also only an example within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description herein, rather than being limited to the specific values in the following examples.

[0029] Example 1 A low thermal expansion h-BN-COC thermal conductive composite material and a preparation method thereof are carried out according to the following steps: Step (1): Weigh h-BN (10 μm) with a purity greater than 99.9% and COC, and the volume ratio is: filler: resin = 1:9. Add them to a micro mixer and mechanically stir at room temperature for 2 h. Take out the stirred raw materials to obtain COC particles uniformly covered with h-BN. Step (2): Fill the h-BN-COC synthesis material into the feed port of a granulator at a melt temperature of 220 °C. Through high-temperature melting, make it present an unfrozen molten state. After cooling and forming in a water bath, put the formed raw material strip into a cutting machine to obtain h-BN / COC particles. Step (3): Put the h-BN / COC particles into an oven, dry them at 110 °C for 8 h, and then take them out; Step (4): Shape the dried h-BN / COC particles by hot pressing at high temperature (temperature: 200 °C, time: 0.5 h, pressure: 170 MPa), and then cool them at room temperature to obtain a composite material plate. The properties of the prepared composite thermal conductive material are shown in Table 1.

[0030] Example 2 A low thermal expansion h-BN-COC thermal conductive composite material and its preparation method are carried out according to the following steps: Step (1): Weigh h-BN (10 μm) with a purity greater than 99.9% and COC, and the volume ratio is: filler: resin = 2:8. Add them to a micro mixer and mechanically stir at room temperature for 2 h: Take out the stirred raw materials to obtain COC particles uniformly covered with h-BN; Step (2): Fill the h-BN-COC synthetic material into the feed port of a granulator at a melt temperature of 220 °C. Through high-temperature melting, make it in an unfrozen molten state, cool and form it through a water bath, and then put the formed raw material strip into a cutting machine to obtain h-BN / COC particles; Step (3): Put the h-BN / COC particles into an oven, dry them at 110 °C for 8 h, and then take them out; Step (4): Shape the dried h-BN / COC particles by hot pressing at high temperature (temperature: 200 °C, time: 0.5 h, pressure: 170 MPa), and then cool them at room temperature to obtain a composite material plate. The properties of the prepared composite thermal conductive material are shown in Table 1.

[0031] Example 3 A low thermal expansion h-BN-COC thermal conductive composite material and its preparation method are carried out according to the following steps: Step (1): Weigh h-BN (10 μm) with a purity greater than 99.9% and COC, and the volume ratio is: filler: resin = 3:7. Add them to a micro mixer and mechanically stir at room temperature for 2 h: Take out the stirred raw materials to obtain COC particles uniformly covered with h-BN; Step (2): Fill the h-BN-COC synthetic material into the feed port of a granulator at a melt temperature of 220 °C. Through high-temperature melting, make it in an unfrozen molten state, cool and form it through a water bath, and then put the formed raw material strip into a cutting machine to obtain h-BN / COC particles; Step (3): Put the h-BN / COC particles into an oven, dry them at 110 °C for 8 h, and then take them out; Step (4): The dried h-BN / COC particles are formed by hot pressing at high temperature (temperature: 200 °C, time: 0.5 h, pressure: 170 MPa), and then cooled at room temperature to obtain a composite material plate. The performance of the prepared composite thermal conductive material is shown in Table 1.

[0032] Example 4 A low thermal expansion h-BN-COC thermal conductive composite material and its preparation method are carried out according to the following steps: Step (1): Weigh h-BN (25 μm) and COC with a purity greater than 99.9%, and the volume ratio is: filler: resin = 1:9. Add them to a micro mixer and mechanically stir at room temperature for 2 h. Take out the stirred raw materials to obtain COC particles uniformly covered with h-BN. Step (2): The h-BN-COC synthetic material is filled into the feeding port of a granulator at a melt temperature of 220 °C. Through high-temperature melting, it is in an unfrozen molten state. After forming by water bath cooling, the formed raw material strip is put into a cutting machine to obtain h-BN / COC particles. Step (3): Put the h-BN / COC particles into an oven at 110 °C and dry for 8 h, then take them out. Step (4): The dried h-BN / COC particles are formed by hot pressing at high temperature (temperature: 200 °C, time: 0.5 h, pressure: 170 MPa), and then cooled at room temperature to obtain a composite material plate. The performance of the prepared composite thermal conductive material is shown in Table 2.

[0033] Example 5 A low thermal expansion h-BN-COC thermal conductive composite material and its preparation method are carried out according to the following steps: Step (1): Weigh h-BN (25 μm) and COC with a purity greater than 99.9%, and the volume ratio is: filler: resin = 2:8. Add them to a micro mixer and mechanically stir at room temperature for 2 h. Take out the stirred raw materials to obtain COC particles uniformly covered with h-BN. Step (2): The h-BN-COC synthetic material is filled into the feeding port of a granulator at a melt temperature of 220 °C. Through high-temperature melting, it is in an unfrozen molten state. After forming by water bath cooling, the formed raw material strip is put into a cutting machine to obtain h-BN / COC particles. Step (3): Put the h-BN / COC particles into an oven at 110 °C and dry for 8 h, then take them out. Step (4): The dried h-BN / COC particles are formed by hot pressing at high temperature (temperature: 200 °C, time: 0.5 h, pressure: 170 MPa), and then cooled at room temperature to obtain a composite material plate. The properties of the prepared composite thermal conductive material are shown in Table 2.

[0034] Example 6 A low thermal expansion h-BN-COC thermal conductive composite material and its preparation method are carried out according to the following steps: Step (1): Weigh h-BN (25 μm) and COC with a purity greater than 99.9%, and the volume ratio is: filler: resin = 3:7. Add them to a micro mixer and mechanically stir at room temperature for 2 h. Take out the stirred raw materials to obtain COC particles uniformly covered with h-BN. Step (2): The h-BN-COC synthetic material is filled into the feed port of a granulator at a melt temperature of 220 °C. Through high-temperature melting, it is in an unfrozen molten state. After being cooled and formed by a water bath, the formed raw material strip is put into a cutting machine to obtain h-BN / COC particles. Step (3): Put the h-BN / COC particles into an oven, dry them at 110 °C for 8 h, and then take them out. Step (4): The dried h-BN / COC particles are formed by hot pressing at high temperature (temperature: 200 °C, time: 0.5 h, pressure: 170 MPa), and then cooled at room temperature to obtain a composite material plate. The properties of the prepared composite thermal conductive material are shown in Table 2.

[0035] Example 7 In Example 7, the preparation process of the composite thermal conductive material refers to Example 1, and the difference is only that: the content of h-BN (10 μm) is 5 vol%.

[0036] Example 8 In Example 8, the preparation process of the composite thermal conductive material refers to Example 4, and the difference is only that: the content of h-BN (25 μm) is 5 vol%.

[0037] Comparative Example 1 In Comparative Example 1, the preparation process of the composite thermal conductive material refers to Example 1, and the difference is only that: the content of h-BN (10 μm) is 35 vol%. When the HBN filler increases to 35 vol%, the preparation fails. Specifically, because the volume ratio of the HBN raw material is too large and there is too much powder, it cannot uniformly pass through the granulator to form with the COC particles, making it difficult to prepare and the ratio inaccurate, thus unable to prepare the composite material substrate.

[0038] Comparative Example 2 The preparation process of the composite thermal conductive material in Comparative Example 2 was the same as that in Example 4, except that the content of h-BN (25μm) was 35 vol%. When the HBN filler increased to 35 vol%, the preparation failed. Specifically, because the volume ratio of the HBN raw material was too large and there was too much powder, it could not uniformly pass through the granulator to form with the COC particles, making it difficult to prepare and the ratio inaccurate, thus unable to prepare the composite material substrate.

[0039] Table 1 shows the performance parameters of the composite thermal conductive materials obtained in Examples 1-3 and 7:

[0040] Table 2 shows the performance parameters of the composite thermal conductive materials obtained in Examples 4-6 and 8:

[0041] Comparing Examples 1, 2, 3, 7 with Examples 4, 5, 6, 9 respectively, as the content of h-BN increases, the thermal conductivity of the composite material increases significantly. At the same time, large-sized h-BN particles usually have a longer heat conduction path, and the heat conduction path between the particles is longer. The longer conduction path helps to improve the overall thermal conductivity of the composite material, so the thermal conductivity of Examples 4, 5, and 6 is better.

[0042] Comparing Examples 1, 2, 3, 7 with Examples 4, 5, 6, 8 respectively, as the content of h-BN increases, the dielectric constant of the composite material increases accordingly. For large-sized h-BN compared to small-sized ones, the number of fillers may be relatively less. Therefore, the filling effect is more significant, resulting in an increase in the dielectric constant of the overall material. And there are relatively fewer interfaces between large-sized h-BN and the COC matrix, but these interfaces may be more prominent, and these interfaces can affect the way the electric field propagates, thus increasing the overall dielectric constant of the composite material. So the dielectric constants of Examples 4, 5, 6, and 8 are larger, and the regulation of the dielectric constant of the composite material between 2.5 - 3.1 can be achieved.

[0043] Comparing Examples 1, 2, 3, 7 with Examples 4, 5, 6, 8 respectively, as the content of h-BN increases, the coefficient of thermal expansion of the composite material decreases significantly. This is because the coefficient of thermal expansion of h-BN is much lower than that of the COC matrix, so as the content increases, the coefficient of thermal expansion of the composite material gradually decreases. Large-sized h-BN forms larger particle clusters in the composite material, and these particle clusters may exhibit larger expansion when the temperature changes. In contrast, small particles may be more likely to form smaller particle clusters, resulting in a lower coefficient of thermal expansion of the overall material. And large-sized particles usually have a larger surface area, leading to an increase in the interaction between particles. This can increase the coefficient of thermal expansion of the overall material. Therefore, the coefficients of thermal expansion of Examples 4, 5, 6, and 8 are higher.

[0044] For Comparative Examples 1, 2, 3, and 7, as the h-BN content increases, the dielectric loss gradually increases but remains in the order of 4×10 -4 , meeting the requirement of low dielectric loss.

[0045] Comparing Comparative Examples 1, 2, 3, and 7 with Examples 4, 5, 6, and 8 respectively, as the h-BN content increases, the thermal conductivity of the composite material in the Z direction is greater than that in the X / Y direction. The h-BN particles are arranged in layers in the COC matrix, and these layers are more closely packed in the X / Y plane than in the Z direction. Then the heat conduction path along the Z direction may be relatively short. The relatively short heat conduction path results in a relatively large thermal conductivity in the Z direction.

Claims

1. A COC / h-BN composite material, characterized in that, Comprising: A cycloolefin copolymer matrix, and h-BN particles distributed in the cycloolefin copolymer matrix; the volume content of the h-BN particles is 5 to 30 vol%.

2. The COC / h-BN composite material according to claim 1, wherein The h-BN particles are flaky, with a diameter of 10 to 25 μm.

3. The COC / h-BN composite material according to claim 1 or 2, wherein The thermal expansion coefficient of the COC / h-BN composite material is 17.73 to 55.88 ppm / °C.

4. The COC / h-BN composite material according to any one of claims 1-3, characterized in that, The dielectric constant of the COC / h-BN composite material is 2.46 to 3.12, and the dielectric loss is 3.681E-04 to 5.397E-04; The thermal conductivity of the COC / h-BN composite material in the X / Y direction is 0.208 - 0.766 W·m -1 ·K -1 , and the thermal conductivity in the Z direction is 0.302 - 1.204 W·m -1 ·K -1 .

5. A method for preparing a COC / h-BN composite material as described in any one of claims 1-4, characterized in that, Comprising: (1) Mix h-BN particles and COC raw materials to obtain an h-BN / COC mixture; (2) Granulate the h-BN / COC mixture to obtain h-BN / COC particles; (3) Subject the h-BN / COC particles to drying, hot pressing at high temperature to form the particles, and cooling treatment to obtain the COC / h-BN composite material.

6. The preparation method according to claim 6, wherein In step (1), the purity of the h-BN particles > 99.9%; The mixing method is mechanical mixing and stirring; the stirring and mixing temperature is 20 to 30°C, and the stirring time is 0.5 to 1 h.

7. The preparation method according to claim 5 or 6, characterized in that, In step (2), the parameters of the granulation treatment include: first filling the h-BN / COC mixture into the feed port of the granulator, then melting at high temperature, then forming by cold water bath, and finally cutting treatment; The high-temperature melting temperature is 220 to 240°C; The temperature of the cold water bath forming is 0 to 25°C.

8. The preparation method according to any one of claims 5-7, characterized in that, In step (3), the drying temperature is 100 to 110°C, and the time is 6 to 8 hours; preferably, the drying temperature is 100°C, and the drying time is 8 hours.

9. The preparation method according to any one of claims 5-8, characterized in that, In step (3), the high-temperature hot pressing temperature is 150 to 220°C, the time is 0.5 to 1 hour, and the pressure is 160 to 180 MPa.

10. The preparation method according to any one of claims 5-9, characterized in that, In step (3), the cooling treatment temperature is 0 to 25°C, and the cooling time is 6 to 10 hours, preferably 8 hours.

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