Al-aln composite packaging substrate and preparation method thereof

Abstract

The application discloses an Al-AlN composite packaging substrate and a preparation method thereof. The preparation method comprises the following steps: surface pretreatment of an aluminum base: performing grinding and polishing treatment on the surface of the aluminum base, and then performing ultrasonic cleaning and blowing dry; surface preparation of a transition layer: placing the pretreated base and high-W alloy powder into a ball mill tank, and performing surface mechanical nano-alloying treatment for 2 hours, wherein the high-W alloy powder is composed of W powder and one of Al, Ni, Cu, Ti and the like according to a certain proportion; surface preparation of an aluminum nitride coating: simultaneously placing the sample with the high-W alloy coating, aluminum nitride powder and a ball milling aid into a ball mill tank, and performing surface mechanical alloying treatment for 1-3 hours, wherein the ball milling aid is one or a mixture of more than one of CaO, MgO, Y2O3 and La2O3. The Al-AlN composite packaging substrate has good thermal conductivity and excellent insulation at the same time, and can provide a new choice for high-power chip packaging substrate materials.

Description

Technical Field

[0001] This invention relates to the field of electronic packaging material preparation, specifically to an Al-AlN composite packaging substrate and its preparation method. Background Technology

[0002] LED light sources boast advantages such as small size, low power consumption, long lifespan, fast response speed, low cost, and environmental friendliness, making them one of the most widely used light sources. However, the limited lighting power of single-chip packaged LEDs cannot meet the ever-increasing lighting and display requirements. Therefore, packaging multiple chips in series and parallel has become a trend in LED development. However, since a single chip can only convert approximately 20% of its electrical energy into light energy, while nearly 80% is converted into heat, multi-chip packaged devices generate significant heat. This heat gradually concentrates within the small chip and cannot dissipate, leading to reduced electronic device performance and accelerated device aging. Therefore, solving the heat dissipation problem of high-power LEDs has become an urgent need in the industry.

[0003] Using suitable heat dissipation materials is a crucial way to solve the heat dissipation problem of high-power LEDs. Aluminum nitride (AlN) substrates possess advantages such as high thermal conductivity, low coefficient of thermal expansion, high hardness, and good electrical insulation, making them valuable for high-power LED packaging. However, AlN's high cost and processing difficulty limit its large-scale application. Metallic aluminum is also an important material for LED packaging substrates. Although it has good thermal conductivity, its poor insulation leads to lower reliability, requiring a layer of insulating epoxy resin to be coated on its surface. However, the poor thermal conductivity of epoxy resin results in poor overall thermal conductivity of the metal substrate. If AlN is prepared as an insulating layer on the surface of the metal substrate, the resulting metal-aluminum nitride composite substrate possesses both good thermal conductivity and excellent insulation. Furthermore, the preparation process avoids the processing difficulties caused by the brittleness of bulk ceramics, saving costs. It also effectively utilizes the good thermal conductivity of metals, meeting the heat dissipation requirements of the packaging substrate while also ensuring its insulation properties.

[0004] Currently, techniques for preparing AlN coatings on Al surfaces include chemical vapor deposition, magnetron sputtering, and pulsed laser deposition. However, the aluminum nitride coatings obtained through these deposition techniques are relatively thin and have poor adhesion to the substrate. Furthermore, these techniques require stringent production conditions, resulting in significant costs in actual production. In conclusion, there is currently no low-cost, simple method for preparing high-quality aluminum nitride coatings. Summary of the Invention

[0005] The purpose of this invention is to provide an Al-AlN composite packaging substrate and its preparation method, which can solve the technical problems mentioned in the background. To achieve the above objective, this invention provides the following technical solution:

[0006] A method for preparing an Al-AlN composite packaging substrate includes the following steps:

[0007] (1) Material preparation and surface pretreatment: 7005 aluminum alloy sheet is cut into round blocks using wire cutting equipment, and its surface is pretreated by metallographic polishing machine. It is then ultrasonically cleaned in anhydrous ethanol for 3-5 minutes and dried to obtain the pretreated round block substrate.

[0008] (2) Preparation of intermediate high tungsten alloy nano-transition layer: Mixed powder of specific components and round block substrate are loaded into the vibration chamber of ball mill at a certain mass ratio and subjected to surface mechanical nano-alloying treatment for 1-3 hours to obtain a sample with high tungsten alloy nano-layer.

[0009] (3) Preparation of surface AlN layer: The sample with high tungsten alloy nanolayer is ultrasonically cleaned and dried, and then loaded into a ball mill jar with a certain mass ratio of aluminum nitride powder for 1-3 hours of surface mechanical nano-alloying treatment.

[0010] Preferably, in step (1), the specific steps of the material surface pretreatment are as follows: 7005 aluminum alloy is processed into a Ф25mm×3mm round block by wire cutting, and then ground with 320-grit, 800-grit, 1500-grit and 2000-grit sandpaper in sequence, and the four sides are ground and polished into rounded corners. Then, the surface is polished to a mirror finish on a polishing machine with 2.5μm diamond polishing paste, and then ultrasonically cleaned in anhydrous ethanol for 3-5 minutes. After drying, the pretreated round block substrate is obtained.

[0011] Preferably, in step (2), the mixed powder composition for preparing the intermediate high tungsten alloy nano-transition layer is W and one of Cu, Cr, Al, Ni and Ti elements, wherein the mass percentage of W is 60%-90% and the mass percentage of other alloying elements is 10%-40%.

[0012] Preferably, in step (2), the W powder used to prepare the intermediate nano-transition layer has a particle size of 75 μm, and the other alloy powders have a particle size of 15-75 μm.

[0013] Preferably, in step (2), the relevant parameters for surface mechanical nano-alloying are as follows: the protective atmosphere is high-purity argon, the ball milling media is stainless steel balls with a diameter of 6mm, the ball mill speed is 1725 rpm, the working mode is ∞-type three-dimensional motion, the mass ratio of the ball milling media to the mixed powder is 4-8:1, and the processing time is 1-3h.

[0014] Preferably, in step (3), the aluminum nitride powder is composed of AlN and a ball milling aid, with AlN accounting for 85%-95% by mass and the ball milling aid accounting for 5%-15% by mass. The ball milling aid is one or more of CaO, MgO, Y2O3 and La2O3 mixed together.

[0015] Preferably, in step (3), the AlN particle size is selected as 2-6 μm.

[0016] Preferably, in step (3), the relevant parameters for surface mechanical nano-alloying are as follows: the protective atmosphere is high-purity argon, the ball milling media is Ф6mm stainless steel balls, the ball mill speed is 1725 rpm, the working mode is ∞-type three-dimensional motion, the mass ratio of ball milling media to ball milling material is 4-8:1, and the processing time is 1-3h.

[0017] The present invention also proposes a method for preparing the Al-AlN composite packaging substrate described above.

[0018] The present invention also proposes a chip that is packaged using the aforementioned Al-AlN composite packaging substrate.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] (1) This invention utilizes surface mechanical nano-alloying to prepare an AlN coating on the surface of an aluminum alloy, obtaining an Al-AlN composite packaging substrate. This material, while ensuring the high thermal conductivity required of a substrate material, also possesses excellent surface insulation properties, providing a new option for high-power packaging substrate materials. During the preparation process, the surface mechanical nano-alloying method is characterized by its simple process and relatively low cost. Furthermore, the prepared coating is uniform and continuous, maintaining a dense structure while possessing a large thickness. Additionally, the coating prepared by the surface mechanical nano-alloying process forms a diffusion layer of a certain thickness with the substrate, resulting in good adhesion between the coating and the substrate, thus extending the coating's service life.

[0021] (2) Due to the high hardness and brittleness of AlN, its coating-forming ability is insufficient when using surface mechanical nano-alloying to prepare this coating, which seriously affects the quality of the final coating. This invention adds a ball milling aid composed of metal oxides and rare earth oxides during the preparation of the AlN coating. Utilizing the dual activation effect of the surface mechanical nano-alloying process and the ball milling aid on the sample and alloy powder, on the one hand, the powder particles generate numerous crystal defects under extensive plastic deformation, providing numerous channels for atomic diffusion, allowing reactions occurring at high temperatures to proceed at room temperature; on the other hand, during high-energy ball milling, the collision between the steel ball and the powder particles generates a large amount of mechanical energy, causing a significant increase in the local temperature of the powder particles, resulting in a certain chemical reaction in that area, while releasing a large amount of heat. This, in turn, causes the surrounding powder to continue reacting until the reactants are completely consumed and the reaction ends. This allows solid AlN to react with the solid ball milling aid to form liquid-phase salts, such as calcium aluminate and yttrium aluminate, improving the AlN coating-forming ability, thereby promoting the formation of the surface coating and making the coating structure more compact.

[0022] (3) Due to the significant difference in mechanical and physical properties between the AlN coating and the aluminum alloy substrate, the aluminum nitride coating is prone to peeling off during service. To address this issue, this invention introduces a high-tungsten alloy nano-transition layer between the AlN coating and the aluminum alloy substrate. The hardness and coefficient of thermal expansion of this transition layer are between those of the AlN coating and the aluminum alloy substrate, effectively mitigating their incompatibility. This prevents the AlN coating from deforming or cracking during high-temperature service, significantly improving the substrate's service life. Simultaneously, this high-tungsten nano-alloy transition layer also possesses excellent thermal conductivity, ensuring excellent reliability without affecting the overall heat dissipation performance of the composite packaging substrate. Attached Figure Description

[0023] Figure 1 This is a schematic diagram illustrating the principle of surface mechanical nano-alloying process in an embodiment of the present invention;

[0024] Figure 2 These are SEM images of the intermediate nanolayer and the surface AlN coating of the W-Al alloy in Example 1 of this invention;

[0025] Figure 3 This is a SEM image of the intermediate nanolayer of the W-Al alloy in step (2) of Example 1 of the present invention;

[0026] Figure 4 This is a comparison image of the original substrate (left) after surface pretreatment and the substrate (right) after AlN coating preparation in Example 1 of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] A method for preparing an Al-AlN composite packaging substrate, comprising the following steps:

[0030] (1) Material preparation and surface pretreatment: 7005 aluminum alloy sheet was processed into Ф25mm×3mm round blocks using wire cutting equipment. 320 grit, 800 grit, 1500 grit and 2000 grit sandpaper were used to grind the blocks in sequence and polish the edges to rounded corners. Then, the surface was polished to mirror finish on a polishing machine with 2.5μm diamond polishing paste. The blocks were then cleaned with anhydrous ethanol using ultrasonic cleaning for 5 minutes and dried to obtain the pretreated round block substrate.

[0031] (2) Surface mechanical nano-alloying treatment (preparation of intermediate high-tungsten alloy nano-transition layer): The pretreated 7005 aluminum alloy round substrate was placed in a ball mill jar, along with 30 steel balls with a diameter of 6 mm and 6 g of W and Al mixed powder in a mass ratio of W:Al = 9:1. The W powder had a particle size of 75 μm, and the Al powder had a particle size of 15 μm. Surface mechanical nano-alloying treatment was performed for 2 h. After treatment, scanning electron microscopy images showed that a uniform and dense tungsten-aluminum alloy nanolayer with a thickness of approximately 90 μm was formed on the surface of the 7005 aluminum alloy.

[0032] (3) Surface mechanical nano-alloying treatment (preparation of surface AlN layer): The sample with W9Al1 alloy nano-layer was ultrasonically cleaned and dried, and then placed in a ball mill jar with 30 steel balls with a diameter of 6 mm. At the same time, 4 g of AlN and CaO mixed powder was added, in which the mass ratio of CaO was 10%, the particle size of AlN was 2 μm, and the particle size of CaO was 75 μm. The surface mechanical nano-alloying treatment was carried out for 2 h.

[0033] After processing, scanning electron microscopy images showed that a dense AlN coating of about 30-45 μm was formed on the surface of the 7005 aluminum alloy.

[0034] The obtained Al-AlN composite packaging substrate material had a coefficient of thermal expansion of 6.37 × 10⁻⁶ as measured by a thermomechanical analyzer. -6 The thermal conductivity was measured to be 232.69 W / (m·K) using a laser thermal conductivity meter.

[0035] Example 2

[0036] A method for preparing an Al-AlN composite packaging substrate, comprising the following steps:

[0037] (1) Material preparation and surface pretreatment: 7005 aluminum alloy sheet is processed into Ф25mm×3mm round blocks using wire cutting equipment. 320 grit, 800 grit, 1500 grit and 2000 grit sandpaper are used to grind the blocks in sequence and polish the edges to rounded corners. Then, the surface is polished to mirror finish on a polishing machine with 2.5μm diamond polishing paste. The blocks are then cleaned with ultrasonic waves in anhydrous ethanol for 3-5 minutes and dried to obtain the pretreated round block substrate.

[0038] (2) Surface mechanical nano-alloying treatment (preparation of intermediate high-tungsten alloy nano-transition layer): The pretreated 7005 aluminum alloy round substrate was placed in a ball mill jar, along with 30 steel balls with a diameter of 6 mm and 6 g of W and Ni mixed powder, where the W:Ni mass ratio was 6:4 and the particle size of both W and Ni powder was 75 μm. Surface mechanical nano-alloying treatment was performed for 1 h. After treatment, scanning electron microscopy images showed that a uniform and dense tungsten-nickel alloy nanolayer with a thickness of approximately 60 μm was formed on the surface of the 7005 aluminum alloy.

[0039] (3) Surface mechanical nano-alloying treatment (preparation of surface AlN layer): The sample with W6Ni4 alloy nano-layer was ultrasonically cleaned and dried, and then placed in a ball mill jar with 30 steel balls with a diameter of 6 mm. At the same time, 4 g of mixed AlN and Y2O3 powder was added, in which the mass ratio of Y2O3 was 5%, the particle size of AlN was 2 μm, and the particle size of Y2O3 was 2 μm. The surface mechanical nano-alloying treatment was carried out for 2 h.

[0040] After processing, scanning electron microscopy images showed that a dense AlN coating of about 22 μm was formed on the surface of the 7005 aluminum alloy.

[0041] The obtained Al-AlN composite packaging substrate material had a coefficient of thermal expansion of 7.87 × 10⁻⁶ as measured by a thermomechanical analyzer. -6 The thermal conductivity was measured to be 225.36 W / (m·K) using a laser thermal conductivity meter.

[0042] Example 3

[0043] A method for preparing an Al-AlN composite packaging substrate, comprising the following steps:

[0044] (1) Material preparation and surface pretreatment: 7005 aluminum alloy sheet was processed into Ф25mm×3mm round blocks using wire cutting equipment. 320 grit, 800 grit, 1500 grit and 2000 grit sandpaper were used to grind the blocks in sequence and polish the edges to rounded corners. Then, the surface was polished to mirror finish on a polishing machine with 2.5μm diamond polishing paste. The blocks were then cleaned with anhydrous ethanol using ultrasonic cleaning for 5 minutes and dried to obtain the pretreated round block substrate.

[0045] (2) Surface mechanical nano-alloying treatment (preparation of intermediate high tungsten alloy nano-transition layer): The pretreated 7005 aluminum alloy round substrate was placed in a ball mill jar, 30 steel balls with a diameter of 6 mm were added, and 6 g of W and Cu mixed powder was added at the same time, wherein the mass ratio of W:Cu was 7:3, and the particle size of W powder and Cu powder was 75 μm. Surface mechanical nano-alloying treatment was carried out for 1 h.

[0046] (3) Surface mechanical nano-alloying treatment (preparation of surface AlN layer): The sample with W7Cu3 alloy nano-layer was ultrasonically cleaned and dried, and then placed in a ball mill jar with 30 steel balls with a diameter of 6 mm. At the same time, 4 g of AlN and Y2O3 were added, with the mass ratio of Y2O3 being 15% of the mixed powder. The particle size of AlN was 2 μm, and the particle size of Y2O3 was 2 μm. The surface mechanical nano-alloying treatment was carried out for 2 h.

[0047] After processing, scanning electron microscopy images showed that a dense AlN coating of about 18 μm was formed on the surface of the 7005 aluminum alloy.

[0048] The obtained Al-AlN composite packaging substrate material had a coefficient of thermal expansion of 8.4 × 10⁻⁶ as measured by a thermomechanical analyzer. -6 The thermal conductivity was measured to be 213.34 W / (m·K) using a laser thermal conductivity meter.

[0049] Example 4

[0050] An Al-AlN composite packaging substrate and its preparation method are carried out according to the following steps:

[0051] (1) Material preparation and surface pretreatment: 7005 aluminum alloy sheet was processed into Ф25mm×3mm round blocks using wire cutting equipment. 320 grit, 800 grit, 1500 grit and 2000 grit sandpaper were used to grind the blocks in sequence and polish the edges to rounded corners. Then, the surface was polished to mirror finish on a polishing machine with 2.5μm diamond polishing paste. The blocks were then cleaned with anhydrous ethanol using ultrasonic cleaning for 5 minutes and dried to obtain the pretreated round block substrate.

[0052] (2) Surface mechanical nano-alloying treatment (preparation of intermediate high tungsten alloy nano-transition layer): The pretreated 7005 aluminum alloy round substrate was placed in a ball mill jar, 30 steel balls with a diameter of 6 mm were added, and 6 g of W and Cu mixed powder was added at the same time, with a mass ratio of W:Cu = 7:3 and a particle size of 75 μm for W powder and Cu powder. Surface mechanical nano-alloying treatment was carried out for 2 h.

[0053] (3) Surface mechanical nano-alloying treatment (preparation of surface AlN layer): The sample with W7Ti3 alloy nano-layer was ultrasonically cleaned and dried, and then placed in a ball mill jar with 30 steel balls with a diameter of 6 mm. At the same time, 4 g of AlN and MgO mixed powder was added, in which the mass ratio of MgO was 10%, the particle size of AlN was 2 μm, and MgO was selected as 200 mesh. The surface mechanical nano-alloying treatment was carried out for 2 h.

[0054] After processing, scanning electron microscopy images showed that a dense AlN coating of about 31 μm was formed on the surface of the 7005 aluminum alloy.

[0055] The obtained Al-AlN composite packaging substrate material had a coefficient of thermal expansion of 8.6 × 10⁻⁶ as measured by a thermomechanical analyzer. -6 The thermal conductivity was measured to be 205.77 W / (m·K) using a laser thermal conductivity meter.

[0056] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the present invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing an Al-AlN composite packaging substrate, characterized in that, Includes the following steps: (1) Material preparation and surface pretreatment: 7005 aluminum alloy sheet is cut into round blocks using wire cutting equipment, and its surface is pretreated by metallographic polishing machine. It is then ultrasonically cleaned in anhydrous ethanol for 3-5 minutes and dried to obtain the pretreated round block substrate. (2) Preparation of intermediate high-tungsten alloy nano-transition layer: Mixed powder of specific composition and round substrate are loaded into the vibration chamber of ball mill at a certain mass ratio and subjected to surface mechanical nano-alloying treatment for 1-3 hours to obtain a sample with high-tungsten alloy nano-layer. The mixed powder composition for preparing intermediate high-tungsten alloy nano-transition layer is W and one of Cu, Cr, Al, Ni and Ti elements, wherein the mass ratio of W is 60%-90% and the mass ratio of other alloying elements is 10%-40%. (3) Preparation of surface AlN layer: The sample with high tungsten alloy nanolayer is ultrasonically cleaned and dried, and then loaded into a ball mill jar with a certain mass ratio of aluminum nitride powder for 1-3 hours of surface mechanical nano-alloying treatment. The aluminum nitride powder is composed of AlN and ball milling aid, with AlN accounting for 85%-95% by mass and ball milling aid accounting for 5%-15% by mass. The ball milling aid is one or more of CaO, MgO, Y2O3 and La2O3.

2. The method for preparing an Al-AlN composite packaging substrate according to claim 1, characterized in that: In step (1), the specific steps of the material surface pretreatment are as follows: 7005 aluminum alloy is processed into a Ф25mm×3mm round block by wire cutting, and then ground with 320 grit, 800 grit, 1500 grit and 2000 grit sandpaper in sequence, and the four sides are ground and polished into rounded corners. Then, the surface is polished to a mirror finish on a polishing machine with 2.5μm diamond polishing paste, and then ultrasonically cleaned in anhydrous ethanol for 3-5 minutes. After drying, the round block substrate with surface pretreatment is obtained.

3. The method for preparing an Al-AlN composite packaging substrate according to claim 1, characterized in that: In step (2), the W powder used to prepare the intermediate nano-transition layer has a particle size of 75 μm, and the particle size of other alloy powders is selected as 15-75 μm.

4. The method for preparing an Al-AlN composite packaging substrate according to claim 1, characterized in that: In step (2), the relevant parameters for surface mechanical nano-alloying are as follows: the protective atmosphere is high-purity argon, the ball milling media is Ф6mm stainless steel balls, the ball mill speed is 1725 rpm, the working mode is ∞-type three-dimensional motion, the mass ratio of ball milling media to mixed powder is 4-8:1, and the processing time is 1-3h.

5. The method for preparing an Al-AlN composite packaging substrate according to claim 1, characterized in that: In step (3), the AlN particle size is selected as 2-6 μm.

6. The method for preparing an Al-AlN composite packaging substrate according to claim 1, characterized in that: In step (3), the relevant parameters for surface mechanical nano-alloying are as follows: the protective atmosphere is high-purity argon, the ball milling media is Ф6mm stainless steel balls, the ball mill speed is 1725 rpm, the working mode is ∞-type three-dimensional motion, the mass ratio of ball milling media to ball milling material is 4-8:1, and the processing time is 1-3h.

7. An Al-AlN composite packaging substrate prepared by the method of any one of claims 1-6.

8. A chip, characterized in that: The Al-AlN composite packaging substrate described in claim 7 is used for packaging.

Images