A copper-diamond-copper sandwich structure water-cooled heat spreader and a preparation method thereof

Abstract

The application is suitable for the field of high-power electronic device heat dissipation technology, and provides a copper-diamond-copper sandwich structure water-cooled radiator and a preparation method thereof.The main structure of the water-cooled radiator is a sandwich structure, the upper layer is copper, the middle layer is MPCVD diamond polycrystal or single crystal material, and the lower layer is copper.The lower layer of copper can have a special water-cooled channel structure to meet the purpose of liquid-cooled heat dissipation.The middle diamond layer quickly conducts the heat of the chip, and the water-cooled channel carries away the heat.The surface copper is convenient for processing when the chip is packaged.The sandwich structure is realized through AMB active brazing technology, the middle layer slurry is nano-silver active solder, which realizes low-temperature brazing and meets the high-temperature thermal cycle reliability after brazing, and the technical application has strong application value and provides strong support for the next generation of water-cooled heat dissipation.

Description

Technical Field

[0001] This invention belongs to the field of heat dissipation technology for high-power electronic devices, and particularly relates to a copper-diamond-copper sandwich structure water-cooled heat sink and its preparation method. Background Technology

[0002] With the rapid development of fields such as artificial intelligence and high-performance computing, the computing power requirements of high-power electronic devices (such as GPUs and AI chips) continue to rise, and chip power density has increased significantly. Traditional heat dissipation technologies are facing severe challenges, especially in the field of liquid cooling, where the thermal conductivity and structural design of existing materials are gradually failing to meet the requirements for efficient heat dissipation.

[0003] Currently, copper-based water-cooled plates remain the mainstream solution due to their ease of processing. However, their upper limit of thermal conductivity (approximately 400 W / m·K) is insufficient to meet the heat dissipation requirements of future higher-power GPU devices. The industry urgently needs breakthrough material and structural innovations to achieve more efficient and stable heat dissipation solutions.

[0004] The thermal conductivity of traditional copper-based water-cooled plates is insufficient to meet the heat dissipation requirements of high-power chips (e.g., heat flux density of 500 W / cm²). Furthermore, the interfacial thermal conductivity of traditional diamond / copper composite materials decreases significantly after high-temperature heat treatment, affecting long-term reliability. Conventional brazing processes lack sufficient temperature resistance, making the heat sink prone to interfacial cracking or delamination during thermal cycling. Summary of the Invention

[0005] The purpose of this invention is to provide a copper-diamond-copper sandwich structure water-cooled heat sink and its preparation method, aiming to solve the problem of low thermal conductivity of traditional copper and the problem of significant decrease in thermal conductivity of diamond / copper composite materials under high and low temperature cycles.

[0006] This invention is implemented as follows:

[0007] A copper-diamond-copper sandwich structure water-cooled radiator, employing a sandwich structure:

[0008] Top layer: Electrolytic copper foil (thickness 0.3-0.5mm), used for chip packaging and processing adaptation.

[0009] Intermediate layer: Diamond single crystal or polycrystalline layer grown by MPCVD (thickness 0.1-2mm, thermal conductivity ≥1200 W / m·K) as the core heat-conducting layer.

[0010] The lower layer is a copper substrate (2-6mm thick) with a surface featuring microchannels or macrochannels arranged in an asymmetrical involute pattern (channel spacing to depth ratio of 1:3 to 1:5) for liquid cooling.

[0011] Interface connection technology:

[0012] The active metal brazing (AMB) process is employed, using nano-silver solder paste (Ag content ≥95%, particle size 20-50nm, added at 0.5-1.5wt%). (Activator), brazing temperature 260-300℃, pressure 0.5-1.2MPa, holding time 8-15 minutes, to achieve low-temperature bonding and high-temperature reliability.

[0013] The present invention provides a copper-diamond-copper sandwich structure water-cooled heat sink and its preparation method, which have the following beneficial effects:

[0014] 1. By introducing an MPCVD diamond layer with a thermal conductivity ≥1200 W / m·K, the overall thermal conductivity of the heat sink is increased to >800 W / m·K, which is twice that of the traditional copper-based solution.

[0015] 2. The AMB active brazing process combined with nano-silver solder paste ensures an interfacial thermal resistance of <5× m²·K / W, with no failure after 1000 cycles of thermal cycling from -40℃ to 150℃.

[0016] 3. The surface roughness of the upper copper foil reaches the nanometer level, meeting the requirements of electronic-grade chip packaging.

[0017] 4. The lower copper substrate meets the requirements for shovel tooth performance and is denser than the copper layer obtained by traditional powder metallurgy composite materials.

[0018] 5. By designing different thicknesses of the upper copper foil, the thermal expansion coefficient of the sandwich structure can be adjusted to meet the requirements of different chip packages for thermal expansion coefficient. Attached Figure Description

[0019] Figure 1 This is a diagram of a copper-diamond-copper sandwich structure. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0022] like Figure 1 As shown, a copper-diamond-copper sandwich structure water-cooled radiator includes an upper layer, a middle layer, and a lower layer, wherein:

[0023] The upper layer is electrolytic copper foil, with a thickness of 0.3-0.5mm;

[0024] The intermediate layer is either a single-crystal or polycrystalline diamond thermal conductive layer grown by MPCVD, with a thickness of 0.1-2 mm and a thermal conductivity ≥1200 W / m·K;

[0025] The lower layer is a copper substrate with a thickness of 2-6mm. The surface is provided with one of microchannels and macrochannels. The channel layout is an asymmetric involute structure, and the channel spacing to depth ratio is 1:3 to 1:5.

[0026] The upper, middle, and lower layers are connected by an AMB active brazing process.

[0027] A method for fabricating a copper-diamond-copper sandwich structure water-cooled heat sink, the method comprising:

[0028] S1. Laser texturing is applied to the diamond layer to form a regular array of pits;

[0029] S2. Microchannels with an asymmetric involute layout are fabricated on a copper substrate and then surface-etched and activated.

[0030] S3. Apply nano-silver active solder paste to the connection interface using ultrasonic-assisted screen printing.

[0031] S4. The three-layer structure is brazed in a vacuum brazing furnace using a gradient pressure control process. The brazing temperature is 260-300℃, the pressure is 0.5-1.2MPa, and the holding time is 8-15 minutes.

[0032] Example 1:

[0033] Diamond layer preparation: Polycrystalline diamond (30% methane concentration, deposition rate 10 μm / h) with a thickness of 0.5 mm was grown in an MPCVD system. A regular array of pits (20 μm depth, 100 μm spacing) was formed by double-sided laser etching.

[0034] The thickness of the electrolytic copper foil is 0.3 mm.

[0035] The copper substrate is 3mm thick, and the microchannel fabrication is performed using femtosecond laser etching (pulse energy 0.5mJ, frequency 100kHz), followed by surface acid pickling and activation. =1:3, processing time 30s)

[0036] Brazing process:

[0037] Nano silver solder paste (containing 20-50nm silver powder and nano The composite filler (ethyl cellulose and rosin derivative in a 3:1 ratio) was coated onto the interface by ultrasonic-assisted screen printing, with a thickness of 50 μm.

[0038] Implement a three-stage heating process in a vacuum brazing furnace:

[0039] Preheating stage: Maintain at 150℃ for 5 minutes;

[0040] Brazing stage: Maintain at 260℃ for 10 minutes, pressure 0.8MPa;

[0041] Slow cooling stage: Cool to room temperature at a rate of 10℃ / minute, with a vacuum degree ≤5× Pa.

[0042] Example 2:

[0043] Diamond layer preparation: Polycrystalline diamond (40% methane concentration, deposition rate 12 μm / h) with a thickness of 1.5 mm was grown in an MPCVD system. A regular array of pits (10 μm depth, 30 μm spacing) was formed by double-sided laser etching.

[0044] The thickness of the electrolytic copper foil is 0.5 mm.

[0045] The copper substrate is 6mm thick, and the microchannel fabrication is performed using femtosecond laser etching (pulse energy 0.5mJ, frequency 100kHz), followed by surface acid pickling and activation. =1:3, processing time 60s)

[0046] Brazing process:

[0047] Nano silver solder paste (containing 20-50nm silver powder and nano The composite filler (ethyl cellulose and rosin derivative in a 3:1 ratio) was coated onto the interface by ultrasonic-assisted screen printing, with a thickness of 30 μm.

[0048] Implement a three-stage heating process in a vacuum brazing furnace:

[0049] Preheating stage: Maintain at 150℃ for 5 minutes;

[0050] Brazing stage: Maintain at 260℃ for 10 minutes, pressure 0.8MPa;

[0051] Slow cooling stage: Cool to room temperature at a rate of 10℃ / minute, with a vacuum degree ≤5× Pa.

[0052] Example 3:

[0053] Diamond layer preparation: Single-crystal diamond (20% methane concentration, deposition rate 2 μm / h) with a thickness of 2 mm was grown in an MPCVD system. A regular array of pits (5 μm depth, 10 μm spacing) was formed by double-sided laser etching.

[0054] The thickness of the electrolytic copper foil is 0.4 mm.

[0055] The copper substrate is 2mm thick, and the microchannel fabrication is performed using femtosecond laser etching (pulse energy 0.6mJ, frequency 100kHz), followed by surface acid pickling and activation. =1:3, processing time 20s)

[0056] Brazing process:

[0057] Nano silver solder paste (containing 20-50nm silver powder and nano The composite filler (ethyl cellulose and rosin derivative in a 3:1 ratio) was coated onto the interface by ultrasonic-assisted screen printing, with a thickness of 30 μm.

[0058] Implement a three-stage heating process in a vacuum brazing furnace:

[0059] Preheating stage: Maintain at 150℃ for 5 minutes;

[0060] Brazing stage: Maintain at 260℃ for 10 minutes, pressure 0.8MPa;

[0061] Slow cooling stage: Cool to room temperature at a rate of 10℃ / minute, with a vacuum degree ≤5× Pa.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A copper-diamond-copper sandwich structure water-cooled heat spreader, characterized in that, The copper-diamond-copper sandwich structure water-cooled heat sink comprises an upper layer, a middle layer and a lower layer, wherein: The upper layer is an electrolytic copper foil with a thickness of 0.3-0.5mm; The middle layer is one of a diamond single crystal thermal conductive layer and a polycrystalline thermal conductive layer grown by an MPCVD method, with a thickness of 0.1-2mm and a thermal conductivity of ≥1200 W / m·K; The surface of the middle layer is subjected to laser texturing treatment to form a pit array with a depth of 20μm and a pitch of 100μm. The lower layer is a copper substrate with a thickness of 2-6mm, provided with one of microchannels and macrochannels on the surface, and the channel layout is an asymmetric involute structure with a channel pitch-depth ratio of 1:3 to 1:5; The upper layer, the middle layer and the lower layer are connected by an AMB active brazing process.

2. The copper-diamond-copper sandwich structure water-cooled heat spreader of claim 1, wherein, The surface of the microchannel copper substrate is provided with a turbulent flow promoting structure comprising periodic protrusions with a height of 50μm.

3. A method of producing a copper-diamond-copper sandwich structure water-cooled heat spreader as claimed in any one of claims 1-2, characterized by, The preparation method comprises: S1, laser texturing treatment is performed on the diamond layer to form a regular pit array; S2, microchannels with an asymmetric involute layout are machined on the copper substrate, and surface pickling activation is performed; S3, nano-silver active solder paste is applied to the connection interface by ultrasonic assisted screen printing; S4, the brazing connection of the three-layer structure is completed in a vacuum brazing furnace using a gradient pressure control process, with a brazing temperature of 260-300℃, a pressure of 0.5-1.2MPa, and a holding time of 8-15 minutes.

4. The method of claim 3, wherein the copper-diamond-copper sandwich structure water-cooled heat spreader is prepared by the steps of: The nano-silver active solder paste comprises a composite filler of 20-50nm silver powder and nano-TiO2 particles, and an organic carrier composed of ethyl cellulose and rosin derivatives in a ratio of 3:

1. ​ 5. The method of claim 3, wherein the copper-diamond-copper sandwich structure water-cooled heat spreader is prepared by the steps of: 5-1) preparing a copper-diamond-copper sandwich structure by the method of claim 1; 5-2) preparing a copper-diamond-copper sandwich structure water-cooled heat spreader by the method of claim 2. The brazing process adopts a three-stage temperature rising curve, including preheating at 150℃ for 5 minutes, brazing at 260℃ for 10 minutes, and a cooling rate of 80℃ / min.

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