A method for preparing a diamond / aluminum composite material with a low coefficient of thermal expansion using a negative expansion material

Abstract

A method for preparing diamond / aluminum composite materials with a reduced coefficient of thermal expansion using a negative expansion material. This invention relates to a method for preparing diamond / aluminum composite materials. To reduce the coefficient of thermal expansion of diamond / aluminum composite materials and improve the thermal matching between the diamond / aluminum composite material and semiconductors, this invention introduces a material with a negative coefficient of thermal expansion as a reinforcement into the diamond / aluminum composite material. The resulting diamond / aluminum composite material has an adjustable coefficient of thermal expansion, and its composition can be designed to meet the requirements of different service conditions, thereby achieving control over the coefficient of thermal expansion of the composite material. The prepared diamond / aluminum composite material has a coefficient of thermal expansion closer to that of semiconductor devices such as Si and GaN, better meeting the requirements of thermal management materials for electronic packaging for matching coefficients of thermal expansion.

Description

Technical Field

[0001] This invention relates to a method for preparing diamond / aluminum composite materials containing negative expansion materials. Background Technology

[0002] With the advent of the 5G era, the computing speed and power of electronic devices, such as high-performance computer chips and communication base station power amplifiers, are constantly increasing, leading to increasingly stringent demands for heat dissipation. For example, high-end CPUs can have heat flux densities of hundreds of watts per square centimeter, and under certain extreme conditions, they can even exceed 1000 W / cm². 2 If heat cannot be dissipated in a timely and effective manner, the equipment temperature will rise, which will affect its performance and reliability, and may even lead to failure.

[0003] Diamond, possessing the highest thermal conductivity found in nature, makes diamond / aluminum composites, a promising candidate for novel thermal management materials, particularly those made by mixing diamond with aluminum. However, poor wettability between diamond and aluminum leads to poor interfacial bonding. Researchers both domestically and internationally have improved the interfacial bonding between diamond and aluminum and enhanced the thermal conductivity of diamond / aluminum composites through methods such as process optimization, diamond particle surface treatment, and matrix metal alloying. Specifically, diamond particle surface treatment and matrix alloying modification involve introducing carbide-forming elements into the reinforcing diamond or the aluminum matrix, thereby improving interfacial bonding by forming corresponding carbides at the diamond-aluminum interface. Diamond / aluminum composites hold immense application potential in the field of thermal management materials for electronic packaging.

[0004] Nevertheless, the control of the coefficient of thermal expansion remains lacking in the research of diamond / aluminum composites. The coefficient of thermal expansion of diamond is 1×10⁻⁶. -6 / K, while the coefficient of thermal expansion of aluminum is as high as 23×10 -6 / K. In diamond / aluminum composites, increasing the volume fraction of diamond can reduce the coefficient of thermal expansion of the composite. However, the volume fraction of diamond is limited by the bulk density and cannot be increased indefinitely, making it difficult for diamond / aluminum composites to fully meet the diverse thermal matching requirements of different electronic devices. If there is a mismatch in the coefficient of thermal expansion between the diamond / aluminum composite and the semiconductor chip, thermal stress will be generated due to the difference in their thermal expansion rates when the ambient temperature changes. This thermal stress may trigger the propagation of microscopic defects within the material, such as the initiation and propagation of cracks, which will have a serious negative impact on the reliability of the device, reducing its service life and performance stability. Summary of the Invention

[0005] In order to reduce the coefficient of thermal expansion of diamond / aluminum composite materials, achieve control over the coefficient of thermal expansion of diamond / aluminum composite materials, and improve the matching of the coefficient of thermal expansion between diamond / aluminum composite materials and semiconductors, this invention provides a method for preparing diamond / aluminum composite materials by using negative expansion materials to reduce the coefficient of thermal expansion.

[0006] The method for preparing diamond / aluminum composite materials with reduced thermal expansion coefficient using negative expansion materials according to the present invention is carried out according to the following steps:

[0007] I. Weighing the raw materials

[0008] Weigh diamond particles, negative expansion material and aluminum matrix as raw materials;

[0009] The volume fraction of the aluminum matrix in the raw material is 30-38%, the volume fraction of the diamond particles is 55-60%, and the negative expansion material is the balance.

[0010] The negative expansion material is ZrW2O8, manganese nitrogen compound, or Cu. 2-x M x V₂O₇; Cu 2-x M x In V₂O₇, M is either Mn or Ba, and 0 < x < 2;

[0011] The average particle size of the diamond particles is larger than that of the negative expansion material.

[0012] The aluminum matrix block is either pure aluminum or an aluminum alloy;

[0013] II. Preform Preparation

[0014] The negative expansion material weighed in step one is mixed with diamond particles and ball-milled. The mixed particles obtained after ball milling are then filled into a graphite mold to obtain a preform.

[0015] III. Preparation of Composite Materials

[0016] Place the preform obtained in step two into a vacuum impregnation furnace, and place the aluminum matrix block weighed in step one on the preform; evacuate the impregnation furnace, and then preheat the preform and aluminum matrix under a protective atmosphere. After preheating, raise the furnace temperature to 680-750°C, and then perform gas pressure impregnation at 680-750°C for 5-15 minutes. Finally, cool and demold to obtain the composite material.

[0017] IV. Annealing treatment of composite materials

[0018] The composite material obtained in step three is annealed to remove residual stress, resulting in a diamond / aluminum composite material containing negative expansion material.

[0019] The annealing process described in step four involves heating the composite material to 100°C at a rate of 5–10°C / min and holding it at that temperature for 0.5–1 h, then heating it to 200–450°C at the same rate and holding it at that temperature for 0.5–6 h, and finally cooling it to room temperature at a rate of less than 5°C / min.

[0020] The present invention has the following beneficial effects:

[0021] 1. This invention, based on diamond / aluminum composite materials, introduces a small amount of material with a negative coefficient of thermal expansion as a reinforcement. This is due to the different proportions of manganese-nitrogen compounds or Cu... 2-x M x V2O7 or ZrW2O8 have different coefficients of thermal expansion, and the coefficient of thermal expansion of the diamond / aluminum composite material can be adjusted. The requirements for the coefficient of thermal expansion under different service conditions can be met through composition design.

[0022] 2. The negative expansion phase particles introduced in this invention are smaller than diamond particles, which allows the negative expansion phase to effectively fill the gaps between diamond particles. The negative expansion phase is introduced without reducing the volume fraction of diamond in the composite material, thereby achieving the control of the thermal expansion coefficient of the composite material.

[0023] 3. This invention employs a combination of reducing the cooling rate and performing annealing to remove residual stress in the composite material. Furthermore, annealing promotes the transformation of g-ZrW₂O₈ to α-ZrW₂O₈, and using ZrW₂O₈ as the negative expansion phase further reduces the coefficient of thermal expansion. The diamond / aluminum composite material prepared by this invention has a coefficient of thermal expansion of 6–7.5 × 10⁻⁶. -6 / K, with a thermal expansion coefficient closer to that of semiconductor devices such as Si and GaN, better meets the requirements of electronic packaging thermal management materials for matching thermal expansion coefficients.

[0024] 4. This invention combines a material with a negative expansion coefficient with an aluminum matrix with a high expansion coefficient. When the temperature changes, the negative expansion effect can offset part of the thermal expansion of aluminum, thereby reducing the overall thermal expansion coefficient of the composite material.

[0025] 5. The ZrW2O8, manganese nitrogen compound, or Cu introduced in this invention 2-x M x V₂O₇ can improve the mechanical properties of the matrix. Specifically, the uniform dispersion of ZrW₂O₈ particles in the matrix can enhance its rigidity and hinder dislocation movement; Cu 2-x M x Metal ions in V2O7 may diffuse with Al to form a transition layer, which effectively alleviates the internal stress caused by the mismatch of thermal expansion coefficients and improves the thermal stability of the composite material. Attached Figure Description

[0026] Figure 1 The thermal expansion curves of the diamond / aluminum composite material with ZrW2O8 negative expansion material prepared in Example 1 before and after annealing are shown. Detailed Implementation

[0027] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any reasonable combination of the specific embodiments.

[0028] Specific Implementation Method 1: This implementation method utilizes a negative expansion material to reduce the coefficient of thermal expansion in a diamond / aluminum composite material, and the preparation method follows these steps:

[0029] I. Weighing the raw materials

[0030] Weigh diamond particles, negative expansion material and aluminum matrix as raw materials;

[0031] The volume fraction of the aluminum matrix in the raw material is 30-38%, the volume fraction of the diamond particles is 55-60%, and the negative expansion material is the balance.

[0032] The negative expansion material is ZrW2O8, manganese nitrogen compound, or Cu. 2-x M x V₂O₇; Cu 2-x M x In V₂O₇, M is either Mn or Ba, and 0 < x < 2;

[0033] The average particle size of the diamond particles is larger than that of the negative expansion material.

[0034] The aluminum matrix block is either pure aluminum or an aluminum alloy;

[0035] II. Preform Preparation

[0036] The negative expansion material weighed in step one is mixed with diamond particles and ball-milled. The mixed particles obtained after ball milling are then filled into a graphite mold to obtain a preform.

[0037] III. Preparation of Composite Materials

[0038] Place the preform obtained in step two into a vacuum impregnation furnace, and place the aluminum matrix block weighed in step one on the preform; evacuate the impregnation furnace, and then preheat the preform and aluminum matrix under a protective atmosphere. After preheating, raise the furnace temperature to 680-750°C, and then perform gas pressure impregnation at 680-750°C for 5-15 minutes. Finally, cool and demold to obtain the composite material.

[0039] IV. Annealing treatment of composite materials

[0040] The composite material obtained in step three is annealed to remove residual stress, resulting in a diamond / aluminum composite material containing negative expansion material.

[0041] The annealing process described in step four involves heating the composite material to 100°C at a rate of 5–10°C / min and holding it at that temperature for 0.5–1 h, then heating it to 200–450°C at the same rate and holding it at that temperature for 0.5–6 h, and finally cooling it to room temperature at a rate of less than 5°C / min.

[0042] This embodiment has the following beneficial effects:

[0043] 1. This embodiment introduces a small amount of material with a negative coefficient of thermal expansion as a reinforcement based on a diamond / aluminum composite material. This is due to the different proportions of manganese nitride compounds or Cu... 2-x M x V2O7 or ZrW2O8 have different coefficients of thermal expansion, and the coefficient of thermal expansion of the diamond / aluminum composite material can be adjusted. The requirements for the coefficient of thermal expansion under different service conditions can be met through composition design.

[0044] 2. The negative expansion phase particles introduced in this embodiment are smaller than diamond particles, which allows the negative expansion phase to effectively fill the gaps between diamond particles. The negative expansion phase is introduced without reducing the volume fraction of diamond in the composite material, thereby achieving the control of the thermal expansion coefficient of the composite material.

[0045] 3. This embodiment combines reducing the cooling rate with annealing to remove residual stress in the composite material. Furthermore, annealing promotes the transformation of g-ZrW₂O₈ to α-ZrW₂O₈, and using ZrW₂O₈ as the negative expansion phase further reduces the coefficient of thermal expansion. The diamond / aluminum composite material prepared in this embodiment has a coefficient of thermal expansion of 6–7.5 × 10⁻⁶. -6 / K, with a thermal expansion coefficient closer to that of semiconductor devices such as Si and GaN, better meets the requirements of electronic packaging thermal management materials for matching thermal expansion coefficients.

[0046] 4. This embodiment combines a material with a negative expansion coefficient with an aluminum matrix with a high expansion coefficient. When the temperature changes, the negative expansion effect can offset part of the thermal expansion of aluminum, thereby reducing the overall thermal expansion coefficient of the composite material.

[0047] 5. The ZrW2O8, manganese nitrogen compound, or Cu introduced in this embodiment 2-x M x V₂O₇ can improve the mechanical properties of the matrix. Specifically, the uniform dispersion of ZrW₂O₈ particles in the matrix can enhance its rigidity and hinder dislocation movement; Cu 2-x M xMetal ions in V2O7 may diffuse with Al to form a transition layer, which effectively alleviates the internal stress caused by the mismatch of thermal expansion coefficients and improves the thermal stability of the composite material.

[0048] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the diamond particles mentioned in step one are artificial single-crystal diamonds, and the average particle size of the diamond particles is 100-500μm.

[0049] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the average particle size of the negative expansion material described in step 1 is 30-250 μm.

[0050] Specific Implementation Method Four: This implementation method differs from one of the specific implementation methods one to three in that: the diamond particles in step one have no coating on their surface, or are diamond particles coated with a metal coating. The thickness of the metal coating is 50-300 nm, and the metal coating is Ti, Cr, Mo, or W.

[0051] Specific Implementation Method Five: This implementation method differs from one of Specific Implementation Methods One to Four in that the aluminum alloy mentioned in step one is one or a combination of several of the following: Al-Si alloy, Al-Si-Cu alloy, Al-Cu-Mg alloy, Al-Zn-Cu alloy, Al-Zn-Mg-Cu alloy, and Al-Si-Cu-Mg alloy.

[0052] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the ball milling process described in step two is as follows: the ball-to-material ratio is (10-30):1, the rotation speed is 50-300 rpm, and the time is 0.5-10 h.

[0053] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the preheating temperature in step three is 450-550℃ and the preheating time is 1-3 hours.

[0054] Specific Implementation Method Eight: This implementation method differs from one of Specific Implementation Methods One to Seven in that the protective atmosphere described in step three is one of helium atmosphere, argon atmosphere, and nitrogen atmosphere.

[0055] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the air pressure is set to 5-30 MPa during the air pressure infiltration process described in step three.

[0056] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that the cooling rate described in step 3 is less than 2°C / min.

[0057] Example 1

[0058] The preparation method of diamond / aluminum composite material with reduced thermal expansion coefficient using negative expansion materials in this embodiment is carried out according to the following steps:

[0059] I. Weighing the raw materials

[0060] Weigh diamond particles, negative expansion material and aluminum matrix as raw materials;

[0061] The raw material contains 38% aluminum matrix blocks by volume, 60% diamond particles by volume, and the remainder is negative expansion material.

[0062] The diamond particles are synthetic single-crystal diamonds with an average particle size of 355 μm.

[0063] The negative expansion material is ZrW2O8;

[0064] The average particle size of the negative expansion material is 50 μm;

[0065] The diamond particles have no coating on their surface.

[0066] The aluminum matrix block is pure aluminum;

[0067] II. Preform Preparation

[0068] The negative expansion material weighed in step one is mixed with diamond particles and ball-milled. The mixed particles obtained after ball milling are then filled into a graphite mold to obtain a preform.

[0069] The ball milling process described in step two is as follows: ball-to-material ratio is 15:1, rotation speed is 200 rpm, and time is 4 hours;

[0070] III. Preparation of Composite Materials

[0071] Place the preform obtained in step two into a vacuum impregnation furnace, and place the aluminum matrix block weighed in step one on the preform; evacuate the impregnation furnace, and then preheat the preform and aluminum matrix under a protective atmosphere. After preheating, raise the furnace temperature to 700°C, and then perform gas pressure impregnation at 700°C for 10 minutes. Finally, cool and demold to obtain the composite material.

[0072] The preheating temperature is 500℃ and the preheating time is 1 hour;

[0073] The protective atmosphere is a helium atmosphere;

[0074] The pressure during the gas pressure infiltration was set to 15 MPa.

[0075] The cooling rate is 1.5℃ / min;

[0076] IV. Annealing treatment of composite materials

[0077] The composite material obtained in step three is annealed to remove residual stress, resulting in a diamond / aluminum composite material containing negative expansion material.

[0078] The annealing process involves heating the composite material to 100°C at a rate of 10°C / min and holding it at that temperature for 0.5 hours, then heating it to 200°C at the same rate and holding it at that temperature for 0.5 hours, and finally cooling it to room temperature at a rate of 4°C / min.

[0079] Figure 1 The figures show the thermal expansion curves of the diamond / aluminum composite material with ZrW2O8 negative expansion material prepared in Example 1 before and after annealing. In the temperature range of 50–150 °C, the average coefficient of thermal expansion of the composite material in the original and annealed states increased from 9.63 × 10⁻⁶ to 9.63 × 10⁻⁶. -6 / K decreased to 6.01×10 -6 / K, the coefficient of thermal expansion of diamond / aluminum composite material decreased by 37.6% after annealing.

[0080] Example 2

[0081] The preparation method of diamond / aluminum composite material with reduced thermal expansion coefficient using negative expansion materials in this embodiment is carried out according to the following steps:

[0082] I. Weighing the raw materials

[0083] Weigh diamond particles, negative expansion material and aluminum matrix as raw materials;

[0084] The raw material contains 35% aluminum matrix blocks by volume, 60% diamond particles by volume, and the remainder is negative expansion material.

[0085] The diamond particles are synthetic single-crystal diamonds with an average particle size of 355 μm.

[0086] The negative expansion material is a manganese nitrogen compound, Mn3Zn. 0.5 Ge 0.5 N;

[0087] The average particle size of the negative expansion material is 30 μm;

[0088] The diamond particles have no coating on their surface.

[0089] The aluminum matrix block is pure aluminum;

[0090] II. Preform Preparation

[0091] The negative expansion material weighed in step one is mixed with diamond particles and ball-milled. The mixed particles obtained after ball milling are then filled into a graphite mold to obtain a preform.

[0092] The ball milling process described in step two is as follows: ball-to-material ratio of (10-30):1, rotation speed of 50-300 rpm, and time of 0.5-10 h;

[0093] III. Preparation of Composite Materials

[0094] Place the preform obtained in step two into a vacuum impregnation furnace, and place the aluminum matrix block weighed in step one on the preform; evacuate the impregnation furnace, and then preheat the preform and aluminum matrix under a protective atmosphere. After preheating, raise the furnace temperature to 720°C, and then perform gas pressure impregnation at 720°C for 10 minutes. Finally, cool and demold to obtain the composite material.

[0095] The preheating temperature is 500℃ and the preheating time is 1 hour;

[0096] The protective atmosphere is a helium atmosphere;

[0097] The pressure during the gas pressure infiltration was set to 15 MPa.

[0098] The cooling rate is 1°C / min;

[0099] IV. Annealing treatment of composite materials

[0100] The composite material obtained in step three is annealed to remove residual stress, resulting in a diamond / aluminum composite material containing negative expansion material.

[0101] The annealing process involves heating the composite material to 100°C at a rate of 10°C / min and holding it at that temperature for 0.5 hours, then heating it to 200°C at the same rate and holding it at that temperature for 0.5 hours, and finally cooling it to room temperature at a rate of less than 5°C / min.

[0102] Testing revealed that the average coefficient of thermal expansion (50–150°C) of the diamond / aluminum composite material prepared in Example 2 before and after annealing was 9.56 × 10⁻⁶. -6 / K, 7.54×10 -6 / K, the coefficient of thermal expansion of the composite material decreased by 21.1% after annealing.

Claims

1. A method for preparing a diamond / aluminum composite material with a reduced coefficient of thermal expansion using a negative expansion material, characterized in that: The preparation method of diamond / aluminum composite material with reduced coefficient of thermal expansion using negative expansion material is carried out according to the following steps: I. Weighing the raw materials Weigh diamond particles, negative expansion material and aluminum matrix as raw materials; The volume fraction of the aluminum matrix in the raw material is 30-38%, the volume fraction of the diamond particles is 55-60%, and the negative expansion material is the balance. The negative expansion material is ZrW2O8, manganese nitrogen compound, or Cu. 2-x M x V₂O₇; Cu 2-x M x In V₂O₇, M is either Mn or Ba, and 0 < x < 2; The average particle size of the diamond particles is larger than that of the negative expansion material. The aluminum matrix block is either pure aluminum or an aluminum alloy; II. Preform Preparation The negative expansion material weighed in step one is mixed with diamond particles and ball-milled. The mixed particles obtained after ball milling are then filled into a graphite mold to obtain a preform. III. Preparation of Composite Materials Place the preform obtained in step two into a vacuum impregnation furnace, and place the aluminum matrix block weighed in step one on the preform; evacuate the impregnation furnace, and then preheat the preform and aluminum matrix under a protective atmosphere. After preheating, raise the furnace temperature to 680-750°C, and then perform gas pressure impregnation at 680-750°C for 5-15 minutes. Finally, cool and demold to obtain the composite material. IV. Annealing treatment of composite materials The composite material obtained in step three is annealed to remove residual stress, resulting in a diamond / aluminum composite material containing negative expansion material. The annealing process described in step four involves heating the composite material to 100°C at a rate of 5–10°C / min and holding it at that temperature for 0.5–1 h, then heating it to 200–450°C at the same rate and holding it at that temperature for 0.5–6 h, and finally cooling it to room temperature at a rate of less than 5°C / min.

2. The method for preparing diamond / aluminum composite material with reduced thermal expansion coefficient using negative expansion material according to claim 1, characterized in that: The diamond particles mentioned in step one are synthetic single-crystal diamonds, with an average particle size of 100–500 μm.

3. The method for preparing diamond / aluminum composite material with reduced thermal expansion coefficient using negative expansion material according to claim 1, characterized in that: The average particle size of the negative expansion material described in step one is 30–250 μm.

4. The method for preparing diamond / aluminum composite material with reduced thermal expansion coefficient using negative expansion material according to claim 1, characterized in that: The diamond particles mentioned in step one are diamonds without a surface coating or diamonds coated with a metal coating. The thickness of the metal coating is 50-300 nm, and the metal coating is Ti, Cr, Mo, or W.

5. The method for preparing diamond / aluminum composite material with reduced thermal expansion coefficient using negative expansion material according to claim 1, characterized in that: The aluminum alloy mentioned in step one is one or a combination of several of the following: Al-Si alloy, Al-Si-Cu alloy, Al-Cu-Mg alloy, Al-Zn-Cu alloy, Al-Zn-Mg-Cu alloy, and Al-Si-Cu-Mg alloy.

6. The method for preparing diamond / aluminum composite material with reduced thermal expansion coefficient using negative expansion material according to claim 1, characterized in that: The ball milling process described in step two is as follows: the ball-to-material ratio is (10-30):1, the rotation speed is 50-300 rpm, and the time is 0.5-10 h.

7. The method for preparing diamond / aluminum composite material with reduced thermal expansion coefficient using negative expansion material according to claim 1, characterized in that: The preheating temperature in step three is 450–550℃, and the preheating time is 1–3 hours.

8. The method for preparing diamond / aluminum composite material with reduced thermal expansion coefficient using negative expansion material according to claim 1, characterized in that: The protective atmosphere described in step three is one of helium, argon, or nitrogen.

9. The method for preparing diamond / aluminum composite material with reduced thermal expansion coefficient using negative expansion material according to claim 8, characterized in that: In step three, the gas pressure during gas pressure infiltration is set to 5–30 MPa.

10. The method for preparing diamond / aluminum composite material with reduced thermal expansion coefficient using negative expansion material according to claim 1, characterized in that: The cooling rate described in step three is less than 2°C / min.

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