High-thermal-conductivity insulating PTFE / BN ball and diamond composite thermal interface material and dry preparation method thereof

Abstract

The invention discloses a high-thermal-conductivity and insulating PTFE / BN ball and diamond composite thermal interface material and a dry preparation method of the high-thermal-conductivity and insulating PTFE / BN ball and diamond composite thermal interface material. The material is prepared from, by mass, 20%-30% of polytetrafluoroethylene (PTFE), 70%-80% of boron nitride balls (BN) and diamond powder through dry cold press molding, the thermal conductivity ranges from 12.3 W / m.K to 15.6 W / m.K, and the volume resistivity is gt; the thickness is 1015 omega.cm. The preparation process does not need a solvent, comprises the steps of BN ball and diamond dry mixing, PTFE powder vacuum ultrasonic dispersion, cold press molding and the like, and is environment-friendly and low in consumption. The obtained material has high thermal conductivity, electrical insulativity and flexibility, and is suitable for heat dissipation management of chips, 5G equipment and other high-temperature environments.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electronic heat dissipation materials, and particularly relates to a polytetrafluoroethylene (PTFE) based BN ball@diamond composite thermal interface material suitable for high-power chip heat dissipation and a solvent-free dry process preparation process thereof. BACKGROUND

[0002] With the continuous increase in the power density of 5G communication equipment, artificial intelligence chips and new energy devices, the heat dissipation bottleneck problem in the devices is increasingly prominent. The traditional thermal interface materials (such as silicon-based thermal conductive grease and epoxy glue) have the following defects:

[0003] (1) Limited thermal conductivity: the thermal conductivity of conventional materials is generally lower than 6 W / m·K, which is difficult to meet the heat dissipation requirements of high-power devices (such as AI chips and IGBT modules), resulting in device overheating failure;

[0004] (2) Process pollution: the wet blending process relies on organic solvents such as dimethylformamide, which not only causes environmental burden, but also increases the interfacial thermal resistance due to residual solvents; (3)

[0005] Unbalanced material performance: under the traditional process, the high ceramic filler filling amount easily leads to material brittleness and loose structure, and powder dropping phenomenon occurs;

[0006] (4) High production cost: processes such as thermal compression molding require high-temperature treatment, and the equipment is complex and the energy consumption is huge, which limits the scale application.

[0007] Existing researches show that boron nitride BN (thermal conductivity ≈ 300 W / m·K) and diamond (thermal conductivity ≈ 2000 W / m·K) are ideal high-thermal-conductivity insulating fillers, but how to build an efficient thermal conduction network in a polymer matrix still needs to be broken through. PTFE is a high-temperature-resistant, low-dielectric-constant polymer material, and its non-polar surface is expected to optimize the thermal conduction path with the interface compatibility of diamond, but there is no dry process preparation technology reported based on the PTFE / BN ball@diamond system. Therefore, it is of great value to develop an environmentally friendly, low-cost and flexible PTFE-based thermal interface material preparation process with high thermal conductivity. SUMMARY

[0008] The application aims to provide a high-thermal-conductivity PTFE / BN ball@diamond composite thermal interface material and a dry process preparation method thereof, which are solvent-free, low-energy-consumption and can be produced on a large scale, and solve the problems of insufficient thermal conductivity of traditional materials, process pollution and lack of flexibility.

[0009] TECHNICAL SOLUTION

[0010] Filler premixing: 80-90% mass fraction of BN balls (particle size 90-110 μm) and 10-20% mass fraction of diamond powder (particle size 50-60 μm) are mixed by dry method to build a "BN ball skeleton-diamond filling" multi-level heat conduction network;

[0011] Vacuum ultrasonic mixing: 25-30% mass fraction of PTFE powder and 70-75% BN ball-diamond mixture are mixed by dry method under vacuum ultrasonic environment for 30-60 min, using ultrasonic cavitation effect to promote uniform dispersion of fillers and enhance the interface bonding between PTFE and fillers.

[0012] The ratio of PTFE to BN ball-diamond mixture is shown in the following table:

[0013] Table 1: PTFE and BN ball-diamond mixture ratio range interval

[0014] Scheme 1 Scheme 2 Scheme 3 Scheme 4 PTFE 25％ 25％ 30％ 30％ BN balls (90-110 μm) 60％ 67.5％ 56％ 63％ Diamond (50-60 μm) 15％ 7.5％ 14％ 7％

[0015] Cold pressing: the mixture is loaded into the mold and cold pressed at a pressure of 10-30 MPa for 5-15 min, using the cold flow characteristics of PTFE powder to realize the wrapping and bonding of fillers;

[0016] Post-processing: cut into sheet materials with a thickness of 0.5-2 mm after demolding.

[0017] Beneficial effects

[0018] 1. Breakthrough in thermal conductivity: through the synergistic filling of BN balls and diamond and the low interfacial thermal resistance characteristics of PTFE matrix, the material thermal conductivity reaches 15.6 W / m·K, which is 300% higher than traditional wet BN ball / PTFE materials, covering the range of 12.3-15.6 W / m·K, meeting the heat dissipation needs of different power devices;

[0019] 2. Green process advantage: the whole process is dry process without solvent, avoiding environmental pollution and solvent residue thermal resistance, cold pressing energy consumption is reduced by 45% compared with hot pressing process, and the equipment is simple and easy to mass production;

[0020] 3. Balanced comprehensive performance: 25-30% PTFE as a binder phase still maintains excellent flexibility (bending radius <5 mm) under 70-80% high filler load, volume resistivity >10 15 Ω·cm, with electrical insulation and structural stability;

[0021] 4. Anti-dust characteristics: dry mixing and cold pressing process makes the fillers and PTFE matrix form a tight interface, and there is no dust phenomenon when the filler content reaches 80%, which is suitable for harsh electronic assembly environment. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 : Dry preparation process diagram of high thermal conductivity insulating PTFE / BN ball@diamond composite thermal interface material

[0023] Figure 2 : Comparison diagram of thermal conductivity under different BN ball and diamond ratios DETAILED DESCRIPTION

[0024] Example 1

[0025] (1) 60 g of BN balls (particle size 90-110 μm) and 15 g of diamond powder (particle size 50-60 μm) were weighed and dry mixed in a planetary ball mill for 25 min to obtain a filler mixture;

[0026] (2) 25 g of PTFE powder and 75 g of the above filler mixture were weighed and placed in a vacuum ultrasonic device, and ultrasonic stirring was carried out under a vacuum degree of -0.09 MPa for 50 min;

[0027] (3) The material was loaded into a mold with a diameter of 50 mm, and cold pressing was carried out at a pressure of 30 MPa for 10 min;

[0028] (4) After demolding, cut into 1 mm thick sheets.

[0029] Test results: thermal conductivity 15.6 W / m·K (laser flash method), volume resistivity 3×10 15 Ω·cm, no powder dropping phenomenon.

[0030] Example 2

[0031] (1) The content of BN balls was adjusted to 85%, the content of diamond powder was adjusted to 15%, and the rest was the same as step (1) of Example 1;

[0032] (2) The content of PTFE powder was adjusted to 28%, the content of filler mixture was adjusted to 72%, and vacuum ultrasonic mixing was carried out for 40 min;

[0033] (3) The cold pressing pressure was reduced to 20 MPa, and the pressure was maintained for 12 min.

[0034] Test results: thermal conductivity 14.2 W / m·K, volume resistivity 2.5×10 15 Ω·cm, no powder dropping phenomenon.

[0035] Example 3

[0036] (1) The ratio of BN balls to diamond powder was the same as Example 1;

[0037] (2) The cold pressing pressure was reduced to 10 MPa, and the pressure was maintained for 5 min.

[0038] Test results: thermal conductivity 12.3 W / m·K (slightly reduced packing density of fillers due to pressure reduction), still meeting the heat dissipation requirements of medium-power devices.

[0039] Comparative Example 1

[0040] (1) Single BN ball filler (particle size 90-110 μm) was used, content 80%, PVDF content 20%;

[0041] (2) Hot pressing (110°C, 20MPa, 30min).

[0042] Test results: thermal conductivity 3.1 W / m·K, volume resistivity 1.2 x 10 15 Ω·cm, the material has a powder dropping phenomenon and is prone to cracking.

[0043] Table 2: Comparison of thermal conductivity of comparative examples and examples

[0044] Thermal conductivity (W / m-K) Example 1 15.6 Example 2 14.2 Example 3 12.3 Comparative Example 3.1

[0045] The above examples are all prepared within the range of the ratio of PVDF to BN ball / diamond mixture proposed in the technical solution. Through comparison of the comparative examples and examples, it can be concluded that the dual filler system of PTFE and BN ball / diamond constructs a high-efficiency heat conduction network through particle size matching (BN ball 90-110 μm, diamond 50-60 μm), and the PTFE content is optimized to 25%-30% to balance the adhesion and flexibility. The cold pressing process realizes non-thermal processing by using the cold rheological property of PTFE, reduces the cost and improves the feasibility of mass production. The thermal conductivity of 15.6 W / m·K reaches the leading level of polymer-based thermal interface materials, and at the same time, it has electrical insulation and anti-powder dropping performance, and is suitable for heat dissipation scenarios of high-end electronic equipment such as 5G base stations and new energy vehicles.

[0046] The above examples are only illustrative of the principles and effects of the present application, and are not intended to limit the present application. Any person skilled in the art can modify or change the above examples without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical idea disclosed by the present application should be covered by the claims of the present application.

Claims

1. A method for preparing a high thermal conductivity insulating PTFE / BN sphere@diamond composite thermal interface material, characterized in that, Includes the following steps: Step 1: Dry mix 80%–90% by mass of BN balls with 10%–25% by mass of diamond powder until homogeneous; Step 2: Mix 25%–30% by mass of PTFE powder with 70%–75% by mass of BN sphere-diamond mixture by dry mixing under vacuum ultrasonic conditions until homogeneous; Step 3: Pour the mixture into the mold; Step 4: Cold press molding under pressure of 10–30 MPa; Step 5: After demolding, cut into sheet-like thermal conductive material.

2. The method according to claim 1, characterized in that, The BN spheres have a particle size of 90–110 μm, and the diamond powder has a particle size of 50–60 μm.

3. The method according to claim 1, characterized in that, The mixing conditions are vacuum ultrasonic mechanical stirring dry mixing, and the mixing time is 30–60 min.

4. The method according to claim 1, characterized in that, The holding time for the cold pressing process is 5–15 minutes.

5. The method according to claim 1, characterized in that, The thermal conductivity of the obtained thermal interface material is 12.3–15.6 W / m·K.

6. A PTFE / BN sphere@diamond composite thermal interface material prepared by any one of claims 1–5, characterized in that, It contains a mixture of 20%–30% PTFE and 70%–80% BN spheres with diamond powder, with a thermal conductivity ≥15.6 W / m·K and a volume resistivity >10. 15 Ω·cm.

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