Full-encapsulation metal matrix / diamond composite heat spreader with heat fins and method of making

Abstract

The application relates to the technical field of heat sinks, and discloses a full-wrapping metal base / diamond composite heat sink with heat dissipation fins and a preparation method thereof. The heat sink comprises a central metal base / diamond composite layer, a peripheral copper frame, a lower copper layer and an upper copper layer. The central composite layer is composed of a pure copper or copper alloy base and diamond particles; the peripheral copper frame is distributed in a closed peripheral line around the composite layer and is provided with connecting features such as mounting through holes, positioning holes, fastening screw holes, sealing grooves, positioning bosses or turning edges; a plurality of heat dissipation fins are formed through a one-time processing of a chipping process, and the remaining copper thickness between the fin root and the upper surface of the composite layer is greater than or equal to 0.3 mm. The above layers are integrally formed through continuous metallurgical diffusion of the copper base in the same powder metallurgy sintering process, and the heat sink of the application has no solder layer between the interfaces of the layers, is low in overall thermal resistance and high in reliability.

Description

Technical Field

[0001] This invention relates to the field of radiator technology, and more specifically, to a fully enclosed metal-based / diamond composite radiator with heat dissipation fins and its preparation method. Background Technology

[0002] The heat dissipation path for high-power electronic devices is typically: chip → thermally conductive interface material (TIM) → heat sink substrate → heat sink fins → fluid (air or coolant). The thermal resistance of the heat sink substrate and heat sink fins is the key bottleneck in the entire heat dissipation chain. Traditional heat sinks (copper or aluminum) are no longer sufficient for high-power density applications, and the industry is gradually shifting towards a combination of "high thermal conductivity composite substrate and high-density fins."

[0003] In some existing technologies, a copper / diamond composite substrate is first sintered and then a separately processed copper fin array is bonded to the upper surface of the substrate by brazing or diffusion bonding. This method has weld thermal resistance, typically 1×10⁻⁶. -6 -5×10 - 6 m 2 K / W, the temperature cycling during welding can cause some damage to the interface of the composite material, and the fin density is limited by the welding precision, usually ≤8 fins / cm. The multiple steps lead to low yield and high cost. In some other existing technologies, a thick copper / diamond composite substrate is first prepared, and then fins are formed on the upper surface of the substrate by machining methods such as milling and EDM. This method has the problem that the composite material cannot be machined by conventional means, and the fins can only be processed by EDM or laser. The cycle is extremely long, and the machining surface will result in a large amount of diamond exposed, affecting heat dissipation and corrosion resistance. The fin height is limited by the thickness of the composite material, usually ≤3mm. In other existing technologies, a thick copper / diamond composite substrate is first prepared, and a thick layer of pure copper is first bonded or co-fired on the upper end of the substrate. Then, fins are formed by chiseling teeth on the copper layer. This method has interfacial thermal resistance between the upper and lower layers. It can only solve the problem of machining the upper surface. There is still no machined area at the edge of the substrate. It still needs to be welded to the shell for subsequent use. In addition, the CTE mismatch between the upper copper layer and the substrate may cause stress cracking during temperature cycling.

[0004] Therefore, it is necessary to provide a fully enclosed metal-based / diamond composite radiator with heat dissipation fins and its preparation method, in order to solve the problems of low heat dissipation efficiency and limited application scenarios caused by the current technology of radiators not having both machinable edge areas and one-piece molded heat dissipation fin arrays at the same time. Summary of the Invention

[0005] In view of this, the present invention proposes a fully enclosed metal-based / diamond composite heat sink with heat dissipation fins and its preparation method, aiming to solve the problems of low heat dissipation efficiency and limited application scenarios caused by the current technology heat sink not having both a machinable edge area and a one-time molded heat dissipation fin array.

[0006] This invention proposes a fully enclosed metal-based / diamond composite heat sink with heat dissipation fins, comprising: The central metal-matrix / diamond composite layer consists of a metal matrix and diamond particles. The metal matrix is ​​made of pure copper or a copper alloy, and the volume fraction of the diamond particles is... Satisfy: 40% ≤ ≤70%; The outer copper frame, made of pure copper or copper alloy, surrounds the central metal substrate / diamond composite layer in one or more closed concentric circles, and the radial width Wo of the outer copper frame is ≥1mm; wherein, The central metal-based / diamond composite layer has the same thickness as the outer copper frame; The lower copper cladding layer is made of pure copper or copper alloy and is located on the lower surface of the central metal base / diamond composite layer and the outer peripheral copper frame. The thickness of the lower copper cladding layer is 0.1-5mm. The copper cladding layer is made of pure copper or copper alloy and is located on the upper surface of the central metal base / diamond composite layer and the outer peripheral copper frame. The thickness of the copper cladding layer is ≥4mm. A plurality of heat dissipation fins, wherein the heat dissipation fins are formed in one step by a tooth-shaving process from the upper copper layer, the height H of the heat dissipation fins is ≥2mm, the thickness t of the heat dissipation fins is ≤1mm, and the remaining copper thickness between the root of the heat dissipation fin and the upper surface of the central metal substrate / diamond composite layer is [missing information]. ≥0.3mm; The central metal matrix / diamond composite layer, the outer copper frame, the lower copper layer and the upper copper layer are integrally formed by continuous metallurgical diffusion of the metal matrix in the same powder metallurgy sintering process. The annular area containing the outer copper frame has at least one connection feature, which is at least one of the following: a free mounting through hole, a positioning hole, a fastening screw hole, a sealing groove, a positioning boss, or a machined edge.

[0007] Furthermore, the spacing g of each heat dissipation fin is 0.3-3mm, and the density of each heat dissipation fin is 3-30 fins / cm.

[0008] Furthermore, the arrangement of the heat dissipation fins is at least one of the following: unidirectional parallel arrangement, cross arrangement, radial arrangement, and square column array.

[0009] Furthermore, the remaining copper thickness between the root of the heat dissipation fins and the upper surface of the central metal substrate / diamond composite layer... It is 0.5-2mm.

[0010] Furthermore, the average particle size of the diamond particles is 30-500 μm; The diamond particles are bare diamonds from the factory; or The diamond particles have a metallized coating on their surface, and the metallized coating is made of at least one of Ti, Cr, W, Mo, Zr, Nb, Ta, and carbides or nitrides of the above elements; wherein... The thickness of the metallized coating is 10-1000 nm.

[0011] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The radiator of the present invention is formed in one sintering process with a four-zone structure. All interfaces are metallurgically diffused and bonded to the copper matrix, with no welds or interface thermal resistance, and the overall heat flow path is continuous.

[0012] 2. The top heat dissipation fins of the heat sink of the present invention are formed by a one-time processing of the overcoated copper layer through a tooth-shaving process. The heat dissipation fins and the overcoated copper layer are made of the same copper polycrystalline material. There is no welding interface at the root of the heat dissipation fins, which can achieve high density (typically 10-20 fins / cm) and height-to-diameter ratio (H / t can reach 10-30:1). The heat dissipation capacity of the heat dissipation fins of the present invention far exceeds that of welded fins.

[0013] Third, the heat dissipation fins of the heat sink of the present invention are made of pure copper or copper alloy, with a thermal conductivity of approximately 400 W / mK, which is much higher than that of aluminum (230 W / mK). Combined with the lower central metal base / diamond composite layer, the thermal conductivity of the central metal base / composite layer is 500-1000 W / mK. Therefore, the equivalent thermal resistance of the heat sink of the present invention is as low as 1 / 3 to 1 / 2 of that of existing copper heat sinks, resulting in superior heat dissipation performance.

[0014] Fourth, the annular area where the outer copper frame of the heat sink of the present invention is located can be connected by conventional machining through holes, fastening screw holes, sealing grooves, positioning bosses and other features, without the need to weld the heat sink to the outer shell. Based on the connection features of the heat sink itself, it can be directly installed on the cold plate or device, further ensuring heat dissipation efficiency.

[0015] 5. The heat sink of the present invention has a lower copper layer, which provides a continuous copper contact surface for welding with the device. It can be easily connected directly to the power device by means of brazing or bonding. There are no diamond particles exposed on the welding surface, resulting in high welding quality and good sealing performance.

[0016] VI. The fully enclosed structure of the heat sink of the present invention encloses the central metal base / diamond composite layer in three directions through the outer copper frame, the upper copper layer and the lower copper layer. During temperature cycling, the outer copper layer of the central metal base / diamond composite layer can play a role in stress buffering and thermal expansion coordination, which significantly improves the long-term reliability and thermal cycle life of the heat sink.

[0017] On the other hand, this application also provides a method for preparing a fully enclosed metal-based / diamond composite heat sink with heat dissipation fins, comprising the following steps: S1. Mold loading: A copper sheet or copper powder made of pure copper or copper alloy is laid on the bottom surface of the sintering mold cavity to form a bottom layer, the thickness of which is 0.1-5mm; On the upper surface of the bottom layer, copper or copper alloy components are provided along the inner periphery of the cavity, so that the copper or copper alloy components form a closed annular area within the cavity; The enclosed annular region is filled with a mixture of copper powder (made of pure copper or copper alloy) and diamond particles, wherein the volume fraction of diamond particles in the mixture is 40%-70%. A top layer is formed by laying copper sheets, copper blocks or copper powder made of pure copper or copper alloy on the upper surface of the closed annular area and the mixed powder, and the thickness of the top layer is ≥4mm. S2. Single-stage sintering: The preform formed after loading in step S1 is subjected to powder metallurgy integral sintering to obtain a heat dissipation substrate. The heat dissipation substrate consists of, from top to bottom, an upper copper layer, a coaxial central metal substrate / diamond composite layer and an outer copper frame, and a lower copper layer. The sintering temperature is 500-1000℃, the pressure is 20-500MPa, the holding time is 5min-5h, and the vacuum degree is ≤ Pa; S3, External machining: The heat dissipation substrate obtained by sintering is taken out from the sintering mold, and the outer peripheral area of ​​the heat dissipation substrate is machined to form at least one connection feature; wherein, the outer peripheral area is the area corresponding to the outer peripheral copper frame of the heat dissipation substrate, and the connection feature is at least one of the following: free mounting through hole, positioning hole, fastening screw hole, sealing groove, positioning boss or machined edge. S4. Tooth cutting: The copper overlay is serrated using a serrated cutting tool, which feeds parallel to the upper surface of the heat sink substrate. In one pass, several parallel heat sink fins are formed. During the serration process, the feed depth of the cutting tool is controlled to ensure that the remaining copper thickness between the root of the heat sink fin and the upper surface of the central metal substrate / diamond composite layer is within a certain range. ≥0.3mm.

[0018] Furthermore, step S4 also includes a secondary tooth-shaving process, specifically: After the first tooth-shaving process, the heat dissipation substrate is rotated 90 degrees for a second tooth-shaving process to form a square column array heat dissipation structure.

[0019] Furthermore, the sintering in step S2 is performed using one of the following methods: Temperature 800-1000℃, pressure 20-80MPa, mold made of high-purity graphite or isostatic graphite; or Temperature 700-850℃, pressure 50-150MPa, mold using isostatic graphite or stainless steel sheathing; or Temperature 500-700℃, pressure 150-500MPa, mold made of cemented carbide or silicon carbide ceramic.

[0020] Furthermore, the pure copper or copper alloy used to form the bottom layup, the pure copper or copper alloy components used to form the closed annular area, and the pure copper or copper alloy used to form the top layup in step S1 are pre-treated with surface cleaning before being loaded into the mold. The surface cleaning treatment includes at least one of the following: ultrasonic cleaning with anhydrous ethanol, acid washing with dilute hydrochloric acid or dilute sulfuric acid, rinsing with pure water, or drying.

[0021] Furthermore, the tooth-shaving process in step S4 also includes monitoring the tooth-shaving process, and the monitoring method includes at least one of the following: Real-time feedback of tool feed position and depth limit; or The cutting pattern is monitored visually or microscopically; or Real-time monitoring of cutting resistance of the tool; or Ultrasonic / vibration signal detection during tooth shaving.

[0022] It is understood that the preparation method of the fully enclosed metal-based / diamond composite radiator with heat dissipation fins of the present invention and the fully enclosed metal-based / diamond composite radiator with heat dissipation fins have the same beneficial effects as described above, and the same beneficial effects of the two will not be repeated here.

[0023] Compared with the prior art, the preparation method of the fully enclosed metal-based / diamond composite heat sink with heat dissipation fins of the present invention also has the following beneficial effects: I. Compared with the existing three-step method of "first sintering the substrate separately, then welding the fins, and then welding them to the shell", the preparation method of the present invention simplifies the process to three steps: "one sintering, one toothing, and one peripheral processing", which significantly shortens the production line cycle and improves the production efficiency of the heat sink.

[0024] II. Key Process Constraints of the Shovel Tooth Process in the Preparation Method of the Invention With a diameter of ≥0.3mm, the cutting tool can be successfully processed in one go without having to change the cutting tool midway to avoid the diamond. It also protects the cutting tool from being chipped by the diamond particles, which significantly improves the yield rate of the production line. Attached Figure Description

[0025] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A schematic diagram of an isometric view of a fully enclosed metal-based / diamond composite heat sink with heat dissipation fins provided in an embodiment of the present invention; Figure 2 for Figure 1 The structural cross-sectional view at point AA is specifically a longitudinal cross-sectional view of the fully enclosed metal-based / diamond composite heat sink with heat dissipation fins provided in the embodiment of the present invention. Figure 3 for Figure 1 The structural cross-sectional view at BB is specifically a transverse cross-sectional view of the fully enclosed metal-based / diamond composite heat sink with heat dissipation fins provided in the embodiment of the present invention. Figure 4 This is a schematic diagram of the preparation method of Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the shovel process in Embodiment 1 of the present invention; Figure 6 This is a physical image of the heat sink prepared according to Embodiment 1 of the present invention.

[0026] In the diagram: 1. Central metal base / diamond composite layer; 2. Outer copper frame; 3. Lower copper layer; 4. Upper copper layer; 5. Heat dissipation fins; 6. Free mounting through holes. Detailed Implementation

[0027] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] In some embodiments of this application, a fully enclosed metal-based / diamond composite heat sink with heat dissipation fins is provided, characterized in that it includes: The central metal-matrix / diamond composite layer 1 is composed of a metal matrix and diamond particles. The metal matrix is ​​made of pure copper or a copper alloy, and the volume fraction of the diamond particles is... Satisfy: 40% ≤ ≤70%; The outer copper frame 2, made of pure copper or copper alloy, surrounds the central metal substrate / diamond composite layer in one or more closed circumferential rings, and the radial width Wo of the outer copper frame 2 is ≥ 1 mm; wherein, The central metal-based / diamond composite layer 1 has the same thickness as the outer copper frame 2; The lower copper layer 3 is made of pure copper or copper alloy. The lower copper layer 3 is located on the lower surface of the central metal base / diamond composite layer 1 and the outer peripheral copper frame 2. The thickness of the lower copper layer 3 is 0.1-5mm. The upper copper layer 4 is made of pure copper or copper alloy. The upper copper layer 4 is located on the upper surface of the central metal base / diamond composite layer 1 and the outer peripheral copper frame 2. The thickness of the upper copper layer 4 is ≥4mm. A plurality of heat dissipation fins 5 are formed in one step by the upper copper layer 4 through a tooth-shaving process. The height H of the heat dissipation fins 5 is ≥ 2 mm, the thickness t of the heat dissipation fins 5 is ≤ 1 mm, and the remaining copper thickness between the root of the heat dissipation fins 5 and the upper surface of the central metal substrate / diamond composite layer 1 is [not specified]. ≥0.3mm; The central metal matrix / diamond composite layer 1, the outer copper frame 2, the lower copper layer 3 and the upper copper layer 4 are integrally formed by continuous metallurgical diffusion of the metal matrix in the same powder metallurgy sintering process. The annular area where the outer copper frame 2 is located has at least one connection feature, which is at least one of the following: a free mounting through hole 6, a positioning hole, a fastening screw hole, a sealing groove, a positioning boss, or a machined edge.

[0029] Specifically, the interfaces between each pair of the upper copper layer 4, the outer copper frame 2, the central metal base / diamond composite layer 1, and the lower copper layer 3 do not contain solder layers, welding interfaces, or metallization intermediate layers.

[0030] In some embodiments of this application, the spacing g of each heat dissipation fin 5 is 0.3-3 mm, and the density of each heat dissipation fin 5 is 3-30 fins / cm.

[0031] In some embodiments of this application, the arrangement of the plurality of heat dissipation fins 5 is at least one of unidirectional parallel arrangement, cross arrangement, radial arrangement, and pin-fin array.

[0032] In some embodiments of this application, the shape of the interface between the central metal substrate / diamond composite layer 1 and the outer copper frame 2 in the plane of the heat dissipation substrate is one of the following: circular, elliptical, rectangular, polygonal, or irregular curved.

[0033] It is understood that the shape of the central metal matrix / diamond composite layer 1 can be circular, elliptical, rectangular, polygonal, or irregular curved.

[0034] In some embodiments of this application, the remaining copper thickness between the root of the heat dissipation fin 5 and the upper surface of the central metal substrate / diamond composite layer 1 is... It is 0.5-2mm.

[0035] In some embodiments of this application, the thickness of the top copper layer 4 is 4-15 mm.

[0036] In some embodiments of this application, the outer peripheral copper frame 2 is formed by winding 1-50 turns of copper wire or copper wire with a diameter of 0.5-5mm. After sintering, the copper wire / copper wire are bonded together through metallurgical diffusion to form a continuous outer peripheral copper area.

[0037] In some embodiments of this application, the metal base material is at least one of pure copper, Cu-Cr alloy, Cu-Cr-Zr alloy, Cu-Zr alloy, and Cu-Ag alloy with a purity ≥99.0wt%. The material of the outer copper frame 2 is at least one of pure copper, Cu-Cr alloy, Cu-Cr-Zr alloy, Cu-Zr alloy, and Cu-Ag alloy with a purity ≥ 99.9wt%. The material of the lower copper layer 3 is at least one of pure copper with a purity ≥ 99.9 wt%, Cu-Cr alloy, Cu-Cr-Zr alloy, Cu-Zr alloy, and Cu-Ag alloy; The material of the copper cladding layer 4 is at least one of pure copper with a purity ≥ 99.9 wt%, Cu-Cr alloy, Cu-Cr-Zr alloy, Cu-Zr alloy, and Cu-Ag alloy.

[0038] In some embodiments of this application, the average particle size of the diamond particles is 30-500 μm; The diamond particles are bare diamonds from the factory; or The diamond particles have a metallized coating on their surface, and the metallized coating is made of at least one of Ti, Cr, W, Mo, Zr, Nb, Ta, and carbides or nitrides of the above elements; wherein... The thickness of the metallized coating is 10-1000 nm.

[0039] In some embodiments of this application, the outer copper frame 2 is provided with at least two mounting through holes 6 and / or at least one sealing groove. The diameter of the mounting through holes 6 is 0.5-10 mm, the width of the sealing groove is 0.5-5 mm, and the depth of the sealing groove is 0.2-3 mm.

[0040] In some embodiments of this application, the size of the heat sink is Φ40-Φ60mm, and under room temperature and no forced fluid cooling conditions, the overall equivalent thermal resistance of the heat sink is ≤0.2K / W.

[0041] In another preferred embodiment based on the above embodiments, this embodiment provides a method for preparing a fully enclosed metal-based / diamond composite heat sink with heat dissipation fins, characterized by comprising the following steps: S1. Mold loading: A copper sheet or copper powder made of pure copper or copper alloy is laid on the bottom surface of the sintering mold cavity to form a bottom layer, the thickness of which is 0.1-5mm; On the upper surface of the bottom layer, copper or copper alloy components are provided along the inner periphery of the cavity, so that the copper or copper alloy components form a closed annular area within the cavity; The enclosed annular region is filled with a mixture of copper powder (made of pure copper or copper alloy) and diamond particles, wherein the volume fraction of diamond particles in the mixture is 40%-70%. A top layer is formed by laying copper sheets, copper blocks or copper powder made of pure copper or copper alloy on the upper surface of the closed annular area and the mixed powder, and the thickness of the top layer is ≥4mm. S2. Single-stage sintering: The preform formed after loading in step S1 is subjected to powder metallurgy integral sintering to obtain a heat dissipation substrate. The heat dissipation substrate consists of, from top to bottom, an upper copper layer, a coaxial central metal substrate / diamond composite layer and an outer copper frame, and a lower copper layer. The sintering temperature is 500-1000℃, the pressure is 20-500MPa, the holding time is 5min-5h, and the vacuum degree is ≤ Pa; S3, External machining: The heat dissipation substrate obtained by sintering is taken out from the sintering mold, and the outer peripheral area of ​​the heat dissipation substrate is machined to form at least one connection feature; wherein, the outer peripheral area is the area corresponding to the outer peripheral copper frame of the heat dissipation substrate, and the connection feature is at least one of the following: free mounting through hole, positioning hole, fastening screw hole, sealing groove, positioning boss or machined edge. S4. Tooth cutting: The copper overlay is serrated using a serrated cutting tool, which feeds parallel to the upper surface of the heat sink substrate. In one pass, several parallel heat sink fins are formed. During the serration process, the feed depth of the cutting tool is controlled to ensure that the remaining copper thickness between the root of the heat sink fin and the upper surface of the central metal substrate / diamond composite layer is within a certain range. ≥0.3mm.

[0042] In some embodiments of this application, the process parameters for the shovel teeth in step S4 are: fin height H = 2-15mm, fin thickness t = 0.2-1mm, fin spacing g = 0.3-3mm, shovel tooth feed speed of 50-300mm / min, and cooling method of at least one of dry, oil mist, and water cooling.

[0043] In some embodiments of this application, step S4 further includes a secondary tooth-shaving process, specifically: After the first tooth-shaving process, the heat dissipation substrate is rotated 90 degrees for a second tooth-shaving process to form a pin-fin heat dissipation structure.

[0044] In some embodiments of this application, the sintering in step S2 is performed in one of the following ways: High temperature and low pressure method: temperature 800-1000℃, pressure 20-80MPa, mold using high-purity graphite or isostatic graphite mold; or Medium temperature and medium pressure method: temperature 700-850℃, pressure 50-150MPa, mold using isostatic graphite or stainless steel encased mold; or Low temperature and high pressure method: temperature 500-700℃, pressure 150-500MPa, mold made of cemented carbide or silicon carbide ceramic.

[0045] In some embodiments of this application, the pure copper or copper alloy used to form the bottom layup, the pure copper or copper alloy components used to form the closed annular region, and the pure copper or copper alloy used to form the top layup in step S1 are pre-treated with surface cleaning before being loaded into the mold. The surface cleaning treatment includes at least one of anhydrous ethanol ultrasonic cleaning, dilute hydrochloric acid or dilute sulfuric acid pickling, pure water rinsing, or drying.

[0046] In some embodiments of this application, the diamond particles in the mixed powder in step S1 are bare diamonds or surface-metallized diamonds. The surface-metallized coating of the surface-metallized diamond is made of at least one of Ti, Cr, W, Mo, Zr, Nb, Ta and carbides or nitrides of the above elements, and the coating thickness is 10-1000 nm.

[0047] In some embodiments of this application, the tooth-shaving process in step S4 further includes monitoring the tooth-shaving process, and the monitoring method includes at least one of the following: Real-time feedback of tool feed position and depth limit; or The cutting pattern is monitored visually or microscopically; or Real-time monitoring of cutting resistance of the tool; or Ultrasonic / vibration signal detection during tooth shaving.

[0048] Example 1 Step 1: Material Preparation Diamond particles: HPHT synthetic single crystals, with an average particle size of 210-230μm and a nitrogen content of ≤50ppm. They are shipped in a state of acid-alkali-pure water washing and are bare diamonds with no metallized coating on the surface. Spherical copper powder: average particle size 5-20μm, Cu purity ≥99.85wt%, oxygen content ≤500ppm; External copper components: Φ2mm T2 copper wire, Cu purity ≥99.9wt%, soft state, no oxide layer. Before use, soak in dilute hydrochloric acid (5%) for 3-5 minutes to remove the surface oxide layer, rinse with pure water, dehydrate with anhydrous ethanol, and dry. The lower copper sheet is a Φ40mm × 0.5mm thick pure copper sheet (Cu purity ≥ 99.9 wt%), which is pretreated with dilute hydrochloric acid and then dried. Copper sheet: Φ40mm×5mm thick pure copper block, pretreated with dilute hydrochloric acid and then dried; using a 5mm thick pure copper block can provide machining allowance for subsequent tooth-shaving processes.

[0049] Sintering mold: Φ40mm inner diameter high-purity graphite mold, the volume needs to match the total thickness of 7-8mm, that is, it can accommodate a 0.5mm lower copper cladding thickness, a 2mm central metal base / diamond composite layer thickness and a 5mm upper copper cladding thickness.

[0050] Step 2: Mold loading: Insert the pressure head into the bottom of the mold; A sheet of graphite paper with a diameter of 40mm is laid flat on the surface of the lower pressure head; Place a copper sheet with a specification of Φ40×0.5mm into the paper and lay it flat on the surface of the first graphite paper. Wrap a Φ2mm copper wire around the inner wall of the mold once, with the ends overlapping by 5-10mm to form a copper ring with an inner diameter of Φ36mm and a height of 2mm. Place the copper ring on the upper surface of the lower copper sheet. The inner ring formed by the copper ring is filled with a mixed powder. The mixed powder is obtained by mixing 4.31g of diamond and 7.31g of spherical copper powder in a three-dimensional mixer for 30 minutes. The volume fraction of diamond is 60 vol%. The mixed powder is lightly compacted with a graphite rod so that the top of the powder is flush with the top of the copper ring, both of which are 2mm high.

[0051] A second sheet of graphite paper with a diameter of 40 mm is placed over the central powder and the top of the copper ring. Place a copper-coated block with dimensions of Φ40×5mm on the upper surface of the second graphite paper; Cover the top of the copper block with a third sheet of graphite paper; Insert the upper pressure head onto the upper surface of the third graphite paper.

[0052] Step 3, First SPS sintering: The SPS process parameters are: heating rate 100℃ / min; sintering temperature 800℃; sintering pressure 50MPa to match the high-purity graphite mold; holding time 15min to ensure complete densification of the thick upper copper layer and metallurgical bonding with the underlying layers; vacuum degree ≤10. -2 Pa; After sintering, the pressure is maintained and the furnace is cooled to below 100°C before being depressurized and removed.

[0053] The total thickness of the heat dissipation substrate obtained after sintering is about 7-7.5mm. The heat dissipation substrate consists of the following layers from bottom to top: a 0.5mm thick lower copper layer, a 2mm thick coaxial central metal substrate / diamond composite layer and an outer copper frame, and a 5mm thick upper copper layer.

[0054] Step 4: External peripheral machining: Three Φ1.5mm mounting through holes are drilled at 120° intervals in the outer peripheral area. The outer peripheral area is formed by a 2mm wide copper wire, an upper copper layer corresponding to a 2mm diameter of the copper wire, and a lower copper layer corresponding to a 2mm diameter of the copper wire.

[0055] Step 5: Tooth machining: The process parameters for the tooth-shaving machining process are set as follows: the height of the heat sink fins H = 3.5 mm, that is, a 3.5 mm heat sink fin is shaved out from the upper surface of the 5 mm thick copper cladding layer; the thickness of the heat sink fins is t = 0.4 mm, which is adapted to the standard tooth thickness of the tooth-shaving cutter; the spacing of the heat sink fins g = 0.8 mm, and the density of the heat sink fins is approximately 8.3 fins / cm; the safety thickness between the root of the heat sink fins and the upper surface of the central metal substrate / diamond composite layer is specified. The thickness is 1.5mm; the feed speed of the shovel teeth is 150mm / min, which is compatible with the industry standard speed; the cooling method is to use a small amount of oil mist for cooling, which can prevent copper chips from adhering to the cutting edge of the shovel teeth; the direction of the heat dissipation fins is unidirectional and parallel, that is, from one side of the upper surface of the heat dissipation substrate to the opposite side.

[0056] Close monitoring is conducted simultaneously during the tooth-shaving process. The monitoring includes: the feed depth of the tooth-shaving tool, which should not exceed 3.5mm; the chip shape, which should be a continuous band for pure copper. If chips or metal sparks appear, it indicates that the tooth-shaving tool may have come into contact with diamond particles, and the machine should be stopped immediately for inspection; and the forming quality of the heat dissipation fins, which should be straight, without curling or burrs after forming.

[0057] Step Six: Performance Characterization The integrity of the heat dissipation fins was observed visually and with a 50× microscope. It can be seen that the heat dissipation fins are straight, without chipped teeth or curling.

[0058] The height and spacing of the heat dissipation fins were measured using calipers and a microscope. The measured height of the heat dissipation fins was H = 3.5 ± 0.1 mm, and the spacing of the heat dissipation fins was g = 0.8 ± 0.05 mm.

[0059] The radial sections of the heat sink were measured using an optical microscope or SEM to determine the distance between the root of the heat sink fins and the upper surface of the central metal substrate / diamond composite layer. ≈1.5mm, with no diamond exposed at the base of the heat dissipation fins.

[0060] Based on microscopic observation of the wear of the cutting edge of the shovel before and after the shovel teeth, it was observed that there was no obvious chipping on the cutting edge after the shovel teeth were shoveled.

[0061] The overall equivalent thermal resistance of the heat sink was measured using steady-state thermal resistance testing or transient heat source testing. The measured overall equivalent thermal resistance of the Φ40 heat sink was <0.15K / W.

[0062] The heat sink was radially cut and polished. SEM was used to observe the interfaces between each pair of the top copper layer, the outer copper frame, the central metal substrate / diamond composite layer and the top copper layer. The measured matrix of all interfaces was continuous and without weld seams.

[0063] Additionally, it should be noted that the order of steps four and five in Example 1 is not limited. The peripheral machining can be performed first, followed by the tooth-shaping, or vice versa.

[0064] Example 2 The difference from Example 1 is that a finer shaving cutter is used, and the process parameters for the shaving process are: the thickness of the heat dissipation fins t=0.2mm, the spacing of the heat dissipation fins g=0.3mm, the height of the heat dissipation fins H=3.5mm, and the density of the heat dissipation fins is 20 fins / cm.

[0065] Example 2 corresponds to a forced air cooling or liquid cooling scenario for high power density chips (such as GaN power amplifiers).

[0066] Example 3 The difference from Example 1 is that the mold is changed to an 80×80mm rectangular graphite mold, with the outer perimeter consisting of a copper frame spliced ​​from four Φ2mm copper strips, and the inner 64×64mm ring filled with a mixture of diamond particles and spherical copper powder. The top copper sheet is changed to an 80×80×6mm rectangular copper block (thicker to accommodate the large area of ​​the spade teeth). After sintering, the spade teeth form a heat dissipation fin array of 80mm long × 4mm high × 0.4mm thick × 0.8mm spacing (the 80mm width can accommodate approximately 67 fins).

[0067] Example 3 corresponds to applications such as high-power laser diode bar arrays and IGBT high-power modules.

[0068] Example 4 The difference from Example 1 is that the fin-shaving process includes a second fin-shaving step. The direction of the first fin-shaving step in Example 1 is designated as the X direction, with a fin height of 1.7 mm. Then, the heat sink substrate is rotated 90°, and a second fin-shaving step is performed along the Y direction of the heat sink substrate. The fin height of the second fin-shaving step is also 1.7 mm. This ultimately forms a 5×5 mm × 1.7 mm pin-fin array.

[0069] Example 4 corresponds to a natural convection heat dissipation application scenario.

[0070] Comparative Example 1 The copper / diamond composite substrate with copper plating on both the top and bottom is first prepared using the process described in Chinese patent document (patent number: CN112974809B). The copper plating thickness on the substrate is 1-2 mm, and it is not a toothed design. A separately processed pure copper fin array is then bonded to the upper surface of the substrate by Ag-Cu brazing.

[0071] The above solution has the following problem: there is weld thermal resistance, and the weld thermal resistance is approximately 2 × 10⁻⁶. -6 m 2 K / W; the welding temperature of 800℃ and the second cycle cause some damage to the interface of the composite material; the fin density is limited by the welding accuracy, and the fin density is ≤8 fins / cm; the upper copper layer is too thin to accommodate the machining allowance required by the tooth-shaving process.

[0072] This invention eliminates the welding interface by performing a single sintering and molding process and a single tooth-shaving process, achieving a fin density of up to 20 fins / cm.

[0073] Comparative Example 2 First, a thick copper / diamond composite substrate is prepared, and then the heat sink fins are directly processed by electrical discharge machining.

[0074] The above solution has the following problems: a large number of diamond particles are exposed on the machined surface, affecting thermal contact and corrosion resistance; the processing time for a single group of 80 heat sink fins is 8-24 hours, resulting in extremely low production line efficiency; the height of the heat sink fins is limited by the thickness of the composite material, with a fin height ≤3mm, making it impossible to form heat sink fins with a high aspect ratio; the cost of EDM is approximately 50-200 RMB / cm. 2 The fin area is large, resulting in high processing costs.

[0075] This invention's shovel can process 50 heat dissipation fins in one go in just 1-3 minutes, with a processing cost of approximately 0.5-2 yuan / cm. 2 The fin area, efficiency, and economy are all significantly better than existing solutions.

[0076] Comparative Example 3 The mainstream products in the current heat sink industry use a pure copper substrate, and fin arrays are formed by shaving teeth on the pure copper substrate.

[0077] While the aforementioned solution boasts a mature tooth-scraping process and high production line efficiency, the substrate's thermal conductivity is only approximately 400 W / mK, which is insufficient for high power densities (e.g., 500 W / cm²). 2 In the above scenarios, the heat dissipation capacity is insufficient.

[0078] The heat dissipation substrate of this invention can improve the overall equivalent thermal conductivity by 1.5-2 times compared with the pure copper substrate. Moreover, the tooth-shaving process of this invention is fully compatible with existing production lines and can be directly upgraded on existing tooth-shaving production lines without the need to introduce additional equipment, which is convenient for implementation.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A fully enclosed metal-based / diamond composite heat sink with heat dissipation fins, characterized in that, include: The central metal-matrix / diamond composite layer consists of a metal matrix and diamond particles. The metal matrix is ​​made of pure copper or a copper alloy, and the volume fraction of the diamond particles is... Satisfy: 40% ≤ ≤70%; The outer copper frame, made of pure copper or copper alloy, surrounds the central metal substrate / diamond composite layer in one or more closed concentric circles, and the radial width Wo of the outer copper frame is ≥1mm; wherein, The central metal-based / diamond composite layer has the same thickness as the outer copper frame; The lower copper cladding layer is made of pure copper or copper alloy and is located on the lower surface of the central metal base / diamond composite layer and the outer peripheral copper frame. The thickness of the lower copper cladding layer is 0.1-5mm. The copper cladding layer is made of pure copper or copper alloy and is located on the upper surface of the central metal base / diamond composite layer and the outer peripheral copper frame. The thickness of the copper cladding layer is ≥4mm. A plurality of heat dissipation fins, wherein the heat dissipation fins are formed in one step by a tooth-shaving process from the upper copper layer, the height H of the heat dissipation fins is ≥2mm, the thickness t of the heat dissipation fins is ≤1mm, and the remaining copper thickness between the root of the heat dissipation fin and the upper surface of the central metal substrate / diamond composite layer is [missing information]. ≥0.3mm; The central metal matrix / diamond composite layer, the outer copper frame, the lower copper layer and the upper copper layer are integrally formed by continuous metallurgical diffusion of the metal matrix in the same powder metallurgy sintering process. The annular area containing the outer copper frame has at least one connection feature, which is at least one of the following: a free mounting through hole, a positioning hole, a fastening screw hole, a sealing groove, a positioning boss, or a machined edge.

2. The fully enclosed metal-based / diamond composite heat sink with heat dissipation fins according to claim 1, characterized in that, The spacing g of each heat dissipation fin is 0.3-3mm, and the density of each heat dissipation fin is 3-30 fins / cm.

3. The fully enclosed metal-based / diamond composite heat sink with heat dissipation fins according to claim 1, characterized in that, The arrangement of some of the heat dissipation fins is at least one of the following: unidirectional parallel arrangement, cross arrangement, radial arrangement, and square column array.

4. The fully enclosed metal-based / diamond composite heat sink with heat dissipation fins according to claim 1, characterized in that, The remaining copper thickness between the root of the heat dissipation fins and the upper surface of the central metal substrate / diamond composite layer It is 0.5-2mm.

5. The fully enclosed metal-based / diamond composite heat sink with heat dissipation fins according to claim 1, characterized in that, The average particle size of the diamond particles is 30-500 μm; The diamond particles are bare diamonds from the factory; or The diamond particles have a metallized coating on their surface, and the metallized coating is made of at least one of Ti, Cr, W, Mo, Zr, Nb, Ta, and carbides or nitrides of the above elements; wherein... The thickness of the metallized coating is 10-1000 nm.

6. The method for preparing a fully enclosed metal-based / diamond composite heat sink with heat dissipation fins according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Mold loading: A copper sheet or copper powder made of pure copper or copper alloy is laid on the bottom surface of the sintering mold cavity to form a bottom layer, the thickness of which is 0.1-5mm; On the upper surface of the bottom layer, copper or copper alloy components are provided along the inner periphery of the cavity, so that the copper or copper alloy components form a closed annular area within the cavity; The enclosed annular region is filled with a mixture of copper powder (made of pure copper or copper alloy) and diamond particles, wherein the volume fraction of diamond particles in the mixture is 40%-70%. A top layer is formed by laying copper sheets, copper blocks or copper powder made of pure copper or copper alloy on the upper surface of the closed annular area and the mixed powder, and the thickness of the top layer is ≥4mm. S2. Single-stage sintering: The preform formed after loading in step S1 is subjected to powder metallurgy integral sintering to obtain a heat dissipation substrate. The heat dissipation substrate consists of, from top to bottom, an upper copper layer, a coaxial central metal substrate / diamond composite layer and an outer copper frame, and a lower copper layer. The sintering temperature is 500-1000℃, the pressure is 20-500MPa, the holding time is 5min-5h, and the vacuum degree is ≤ Pa; S3, External machining: The heat dissipation substrate obtained by sintering is taken out from the sintering mold, and the outer peripheral area of ​​the heat dissipation substrate is machined to form at least one connection feature; wherein, the outer peripheral area is the area corresponding to the outer peripheral copper frame of the heat dissipation substrate, and the connection feature is at least one of the following: free mounting through hole, positioning hole, fastening screw hole, sealing groove, positioning boss or machined edge. S4. Tooth cutting: The copper overlay is serrated using a serrated cutting tool, which feeds parallel to the upper surface of the heat sink substrate. In one pass, several parallel heat sink fins are formed. During the serration process, the feed depth of the cutting tool is controlled to ensure that the remaining copper thickness between the root of the heat sink fin and the upper surface of the central metal substrate / diamond composite layer is within a certain range. ≥0.3mm.

7. The method for preparing a fully enclosed metal-based / diamond composite heat sink with heat dissipation fins according to claim 6, characterized in that, Step S4 also includes secondary tooth-shaving machining, specifically: After the first tooth-shaving process, the heat dissipation substrate is rotated 90 degrees for a second tooth-shaving process to form a square column array heat dissipation structure.

8. The method for preparing a fully enclosed metal-based / diamond composite heat sink with heat dissipation fins according to claim 6, characterized in that, The sintering in step S2 is performed using one of the following methods: Temperature 800-1000℃, pressure 20-80MPa, mold made of high-purity graphite or isostatic graphite; or Temperature 700-850℃, pressure 50-150MPa, mold using isostatic graphite or stainless steel sheathing; or Temperature 500-700℃, pressure 150-500MPa, mold made of cemented carbide or silicon carbide ceramic.

9. The method for preparing a fully enclosed metal-based / diamond composite heat sink with heat dissipation fins according to claim 6, characterized in that, The pure copper or copper alloy used to form the bottom layup, the pure copper or copper alloy components used to form the closed annular area, and the pure copper or copper alloy used to form the top layup in step S1 are pre-treated with surface cleaning before being loaded into the mold. The surface cleaning treatment includes at least one of the following: ultrasonic cleaning with anhydrous ethanol, acid washing with dilute hydrochloric acid or dilute sulfuric acid, rinsing with pure water, or drying.

10. The method for preparing a fully enclosed metal-based / diamond composite heat sink with heat dissipation fins according to claim 6, characterized in that, Step S4, the tooth-shaving process, also includes monitoring the tooth-shaving process, and the monitoring method includes at least one of the following: Real-time feedback of tool feed position and depth limit; or The cutting pattern is monitored visually or microscopically; or Real-time monitoring of cutting resistance of the tool; or Ultrasonic / vibration signal detection during tooth shaving.

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