Preparation method of high-thermal-conductivity and low-thermal-expansion laser bar heat sink sheet

Abstract

This invention discloses a method for preparing a high thermal conductivity, low thermal expansion laser bar heat sink. The method involves laser cutting sheet-shaped synthetic diamond into a core material for the laser bar heat sink; magnetron sputtering to deposit chromium or titanium onto the core material surface, followed by coating with an active brazing metal to form an inner core mold; a graphite mold with an array of through holes, each hole equipped with upper and lower graphite pressure heads; the inner core mold, along with a matching metal shell and cover plate, is placed inside the through holes, and the upper and lower graphite pressure heads are assembled to form a template assembly; the template assembly is vacuum hot-pressed to obtain a laser bar heat sink blank, which is then ground and polished to obtain the finished laser bar heat sink. The product obtained by this invention uses sheet-shaped synthetic diamond as the core, with a copper or copper alloy composite surface, further improving the overall thermal conductivity while ensuring a suitable coefficient of thermal expansion, exhibiting good machinability and suitability for mass production.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a method for preparing a laser bar heat sink with high thermal conductivity and low thermal expansion. Background Technology

[0002] With the rapid development of semiconductor laser technology and the continuous expansion of its application fields, high-power semiconductor lasers are widely used in laser processing, laser medicine, laser communication, and national defense. When a high-power semiconductor laser is working, the active region generates a large amount of heat. If this heat is not dissipated in time, it will seriously affect the laser's output power, electro-optical conversion efficiency, and lifespan. Currently, relatively mature heat sink materials on the market, such as aluminum nitride, tungsten copper alloy, and molybdenum copper alloy, although their coefficients of thermal expansion are close to those of the laser chip, have low thermal conductivity and limited heat dissipation capacity. Diamond, on the other hand, has the highest thermal conductivity in nature, reaching up to 2200 W / (mK), and its coefficient of thermal expansion is as low as 0.8 × 10⁻⁶. -6 / ℃. Therefore, by using synthetic diamond as the core and bonding suitable metal materials to the surface, heat sinks with high thermal conductivity and low coefficient of thermal expansion can be fabricated to meet the thermal management requirements of high-power semiconductor lasers.

[0003] Patent CN117340256A discloses a method for preparing a laser bar heat sink. It uses a molybdenum alloy or tungsten alloy as a template, with the core filled with coated diamond particles encapsulated in copper powder and copper alloy powder. After hot pressing and sintering, a surface molybdenum alloy or tungsten alloy is formed, and the core has a diamond / copper composite material structure. The thermal conductivity of the diamond / copper composite material is generally 500–800 W / (mK), and the coefficient of thermal expansion is (6–8) × 10⁻⁶. -6 At a temperature of / ℃, surface coating with molybdenum or tungsten alloys will significantly reduce the overall thermal conductivity of the product. Furthermore, the coefficient of thermal expansion of the selected molybdenum or tungsten alloy must be within 8×10⁻⁶. -6 Only temperatures below a certain temperature can ensure the thermal expansion coefficient matches the chip. Furthermore, using molybdenum or tungsten alloys as templates is prone to deformation under high temperature and pressure, leading to changes in geometry, making processing and positioning difficult, and resulting in uneven thickness of the six-sided metal layer in the finished product.

[0004] How to further improve the overall thermal conductivity of the product, while ensuring a suitable coefficient of thermal expansion and good processability, has become an urgent technical problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a high thermal conductivity and low thermal expansion laser bar heat sink. The resulting product has a sheet-like synthetic diamond as the core and a copper or copper alloy composite on the surface, which further improves the overall thermal conductivity of the product while ensuring a suitable coefficient of thermal expansion. It has good processability and is suitable for mass production.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] A method for preparing a high thermal conductivity, low thermal expansion laser bar heat sink includes the following steps:

[0008] (1) Laser cutting is used to cut sheet-shaped artificial diamond into laser bar heat sink core material;

[0009] (2) The core material is plated with chromium or titanium by magnetron sputtering and coated with an active brazing metal to form an inner mold of the core material.

[0010] (3) A graphite mold with several through holes array is used, and each through hole is equipped with upper and lower graphite pressure heads; the core material inner mold is combined with a matching metal shell and cover plate and placed in the through hole, and the upper and lower graphite pressure heads are assembled to form a template assembly;

[0011] (4) The template assembly is vacuum hot-pressed and sintered to obtain a laser bar heat sink blank, which is then ground and polished to obtain a finished laser bar heat sink.

[0012] According to the above scheme, the thermal conductivity of the sheet-like synthetic diamond in step (1) is 800-2200 W / (mK), and the coefficient of thermal expansion is 0.8-4×10⁻⁶. -6 / ℃, thickness 0.3~3.0mm. Specifically, high thermal conductivity, low thermal expansion synthetic diamond sheets and their composite sheets can be used.

[0013] According to the above scheme, step (1) also includes mechanical grinding and polishing of the core material. This removes the graphite generated on the surface of the sheet-like synthetic diamond core material due to laser cutting, avoiding the adverse effects of free carbon on the interface bonding.

[0014] According to the above scheme, in step (2), the thickness of the chromium or titanium coating deposited by magnetron sputtering is 50-500 nm. The coating on the core material surface can improve the wettability between the metal and diamond, enhance the interfacial bonding strength, and reduce the thermal damage of the core material at high temperatures.

[0015] According to the above scheme, the active brazing metal in step (2) is a brazing sheet containing chromium or titanium, specifically any one of Cu-Sn-Cr, Ag-Cu-Cr, Cu-Sn-Ti, and Ag-Cu-Ti, with a brazing sheet thickness of 0.01 to 0.5 mm.

[0016] According to the above scheme, the coating method used in step (2) includes: forming the active brazing sheet into a cup shape and sheet shape that matches the core material by stamping and pressing it onto the surface of the core material.

[0017] According to the above scheme, the metal shell and cover plate mentioned in step (3) are made of pure copper, molybdenum copper alloy, or tungsten copper alloy; wherein the molybdenum content of the molybdenum copper alloy is 30-80 wt%, and the remainder is copper; the tungsten content of the tungsten copper alloy is 30-80 wt%, and the remainder is copper.

[0018] According to the above scheme, the thickness of the bottom of the metal shell and the cover plate in step (3) is 0.1-1.0mm, and the wall thickness of the four sides of the shell is 1.0-5.0mm.

[0019] According to the above scheme, the vacuum hot pressing sintering in step (4) includes: evacuating to 10 -1 ~10 -2 Pa, heat to 750-850℃ at 5-10℃ / min, hold for 30-60min, and pressurize to 1-10MPa while holding; continue to heat to 850-1000℃ at 1-5℃ / min, and hold for 10-30min.

[0020] According to the above scheme, the outer metal thickness of the laser bar heat sink obtained in step (4) is 0.05 to 0.5 mm.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] By using artificial diamond sheets or their composite sheets with higher thermal conductivity and lower coefficient of thermal expansion as the core, the composition and thickness of the surface composite metal material have greater flexibility, which can result in laser bar heat sink sheets with higher overall thermal conductivity and lower coefficient of thermal expansion.

[0023] By utilizing active brazing metal to composite the core and surface metal, a good bond can be formed between the core and surface metals, while reducing the temperature and time of vacuum hot pressing and minimizing thermal damage to the diamond. Furthermore, the core is completely covered on all six sides by the active brazing metal and placed within the six-sided cavity formed by the copper or copper alloy shell and cover plate, making it less prone to bonding defects such as porosity.

[0024] The laser bar heat sink blank of the present invention is assembled from core material, active brazing metal, copper or copper alloy shell and cover plate one by one. At the same time, high-temperature and high-strength graphite is used as mold. After vacuum hot pressing, the blank has good dimensional consistency. After symmetrical grinding and polishing, the finished product can be obtained. The finished product has good uniformity of the thickness of the metal layer on all six sides. The preparation process is simple and suitable for large-scale production. Attached Figure Description

[0025] Figure 1 : A schematic diagram of the structure of the inner mold of the core material of this invention.

[0026] Figure 2 : Schematic diagram of the assembly structure of a single through hole in the template assembly of the present invention.

[0027] Figure 3 : Schematic diagram of the template assembly of the present invention. Detailed Implementation

[0028] The following embodiments further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.

[0029] Example 1

[0030] 1) Select synthetic diamond multi-crystal wafers with a thickness of 0.8 mm, a thermal conductivity of 1053 W / (mK), and a coefficient of thermal expansion of 1.2 × 10⁻⁶. -6 / ℃; the core material is laser-cut into a size of 9.6×4.6×0.8mm; the core material is placed in a grinding and polishing machine for 10 minutes, and then cleaned with deionized water and alcohol in sequence.

[0031] 2) A 100 nm thick layer of metallic chromium is deposited on the surface of the core material using magnetron sputtering.

[0032] 3) Select a Cu-Sn-Cr active brazing sheet with a thickness of 0.05mm and stamp it into cup-shaped and sheet-shaped parts that match the core material in step 1); such as Figure 1 As shown, the core material 33 and the sheet-like part 31 are placed in the cup-shaped part 32 in sequence, and the cup opening is pressed inward to form the core material inner mold.

[0033] 4) The shell and cover plate are made of pure copper and matched with the inner mold of the core material. The thickness of the bottom of the shell and the cover plate is 0.5mm, and the wall thickness of the four sides of the shell is 2mm; a graphite mold with several through-hole arrays is made of graphite. Figure 3 As shown, the size of each through-hole matches the housing and is equipped with upper and lower graphite pressure heads; as Figure 2 As shown, the lower graphite pressure head 5, copper shell 4, core material inner mold 3, copper cover plate 2, and upper graphite pressure head 1 are combined and placed into each through hole of the graphite mold 6 to form a template assembly.

[0034] 5) Place the template assembly into a vacuum hot press furnace for hot pressing and sintering. The process conditions are: vacuum evacuation to 5×10⁻⁶. - 1 Start heating below Pa; increase the temperature to 800℃ at 10℃ / min, hold for 30min, and pressurize to 3MPa while holding; continue to increase the temperature to 950℃ at 5℃ / min, and hold for 10min.

[0035] 6) Remove the graphite mold and the upper and lower graphite pressure heads to obtain the blank. Grind and polish the blank to obtain the finished laser bar heat sink sheet with dimensions of 10×5×1.2mm and a copper layer thickness of 0.2mm on all six sides.

[0036] Testing revealed that the obtained laser bar heat sink has a comprehensive thermal conductivity of 673 W / (mK) and an average coefficient of thermal expansion of 7.5 × 10⁻⁶ at 25–100 °C. -6 / ℃.

[0037] Example 2

[0038] 1) Select synthetic diamond multi-crystal wafers with a thickness of 0.8 mm, a thermal conductivity of 1053 W / (mK), and a coefficient of thermal expansion of 1.2 × 10⁻⁶. -6 / ℃; the core material is laser-cut into a size of 9.6×4.6×0.8mm; the core material is placed in a grinding and polishing machine for 10 minutes, and then cleaned with deionized water and alcohol in sequence.

[0039] 2) A 50nm thick layer of titanium metal was deposited on the surface of the core material using magnetron sputtering.

[0040] 3) Select a Cu-Sn-Ti active brazing sheet with a thickness of 0.05mm and stamp it into a cup-shaped part and a sheet-shaped part that match the core material in step 1); put the core material and the sheet-shaped part into the cup-shaped part in sequence, and press the cup opening inward to form the core material inner mold.

[0041] 4) A molybdenum-copper alloy with a molybdenum content of 40wt% is selected to process a shell and cover plate that match the inner mold of the core material. The thickness of the bottom of the shell and the cover plate is 0.5mm, and the wall thickness of the four sides of the shell is 2mm. A graphite mold with several through holes is processed by graphite. The size of each through hole matches the shell and is equipped with upper and lower graphite pressure heads. The lower graphite pressure head, the molybdenum-copper alloy shell, the inner mold of the core material, the molybdenum-copper alloy cover plate, and the upper graphite pressure head are combined and placed into each through hole of the graphite mold to form a template assembly.

[0042] 5) Place the template assembly into a vacuum hot press furnace for hot pressing and sintering. The process conditions are: vacuum evacuation to 5×10⁻⁶. - 1 Start heating below Pa; increase the temperature to 800℃ at 10℃ / min, hold for 30min, and pressurize to 5MPa while holding; continue to increase the temperature to 900℃ at 5℃ / min, and hold for 10min.

[0043] 6) Remove the graphite mold and the upper and lower graphite pressure heads to obtain a blank. Grind and polish the blank to obtain a finished laser bar heat sink sheet with dimensions of 10×5×1.2mm and a six-sided molybdenum-copper alloy layer thickness of 0.2mm.

[0044] Testing revealed that the obtained laser bar heat sink has a comprehensive thermal conductivity of 604 W / (mK) and an average coefficient of thermal expansion of 6.3 × 10⁻⁶ at 25–100 °C. -6 / ℃.

[0045] Example 3

[0046] 1) A multi-crystal synthetic diamond wafer with a thickness of 1.6 mm was selected, with a thermal conductivity of 931 W / (mK) and a coefficient of thermal expansion of 1.4 × 10⁻⁶. -6 / ℃; the core material is laser-cut into a size of 9.6×4.6×1.6mm; the core material is placed in a grinding and polishing machine for 10 minutes, and then cleaned with deionized water and alcohol in sequence.

[0047] 2) A 50nm thick layer of titanium metal was deposited on the surface of the core material using magnetron sputtering.

[0048] 3) Select a Cu-Sn-Ti active brazing sheet with a thickness of 0.05mm and stamp it into a cup-shaped part and a sheet-shaped part that match the core material in step 1); put the core material and the sheet-shaped part into the cup-shaped part in sequence, and press the cup opening inward to form the core material inner mold.

[0049] 4) Select a tungsten-copper alloy with a tungsten content of 50wt% to process a shell and cover plate that match the inner mold of the core material. The thickness of the bottom of the shell and the cover plate is 0.5mm, and the wall thickness of the four sides of the shell is 2mm. Use graphite to process a graphite mold with several through holes. The size of each through hole matches the shell and is equipped with upper and lower graphite pressure heads. Place the lower graphite pressure head, tungsten-copper alloy shell, inner mold of the core material, tungsten-copper alloy cover plate, and upper graphite pressure head into each through hole of the graphite mold to form a template assembly.

[0050] 5) Place the template assembly into a vacuum hot press furnace for hot pressing and sintering. The process conditions are: vacuum evacuation to 5×10⁻⁶. - 1 Start heating below Pa; increase the temperature to 800℃ at 10℃ / min, hold for 30min, and pressurize to 5MPa while holding; continue to increase the temperature to 900℃ at 5℃ / min, and hold for 10min.

[0051] 6) Remove the graphite mold and the upper and lower graphite pressure heads to obtain a blank. Grind and polish the blank to obtain a finished laser bar heat sink sheet with dimensions of 10×5×2.0mm and a tungsten copper alloy layer thickness of 0.2mm on all six sides.

[0052] Testing revealed that the obtained laser bar heat sink has a comprehensive thermal conductivity of 559 W / (mK) and an average coefficient of thermal expansion of 5.8 × 10⁻⁶ at 25–100℃. -6 / ℃.

Claims

1. A method for preparing a high thermal conductivity, low thermal expansion laser bar heat sink, characterized in that... Including the following steps: (1) The sheet-shaped artificial diamond is cut into laser bar heat sink core material by laser cutting method; (2) A core material is plated with chromium or titanium by magnetron sputtering, and an active brazing metal is coated on the core material to form an inner mold of the core material; the coating method includes: forming the active brazing sheet into a cup shape and sheet shape that matches the core material by stamping, and pressing and coating it on the surface of the core material; the active brazing metal is a brazing sheet containing chromium or titanium, specifically any one of Cu-Sn-Cr, Ag-Cu-Cr, Cu-Sn-Ti, and Ag-Cu-Ti, and the thickness of the brazing sheet is 0.01 to 0.5 mm; (3) A graphite mold with several through holes is used, and each through hole is equipped with upper and lower graphite pressure heads; the core material inner mold is combined with a matching metal shell and cover plate and placed in the through hole, and the upper and lower graphite pressure heads are assembled to form a template assembly; the metal shell and cover plate are made of pure copper, molybdenum copper alloy, or tungsten copper alloy; wherein the molybdenum content of the molybdenum copper alloy is 30-80 wt%, and the remainder is copper; the tungsten content of the tungsten copper alloy is 30-80 wt%, and the remainder is copper; (4) The template assembly is vacuum hot-pressed and sintered to obtain a laser bar heat sink blank, which is then ground and polished to obtain a finished laser bar heat sink; the vacuum hot-pressing and sintering includes: evacuating to 10 -1 ~10 -2 Pa, heat to 750-850℃ at 5-10℃ / min, hold for 30-60min, and pressurize to 1-10MPa while holding; continue to heat to 850-1000℃ at 1-5℃ / min, and hold for 10-30min.

2. The method for preparing a high thermal conductivity, low thermal expansion laser bar heat sink as described in claim 1, characterized in that... The sheet-like synthetic diamond described in step (1) has a thermal conductivity of 800–2200 W / (mK) and a coefficient of thermal expansion of 0.8–4 × 10⁻⁶ W / (mK). -6 / ℃, thickness 0.3~3.0mm.

3. The method for preparing a high thermal conductivity, low thermal expansion laser bar heat sink as described in claim 1, characterized in that... Step (1) also includes mechanical grinding and polishing of the core material.

4. The method for preparing a high thermal conductivity, low thermal expansion laser bar heat sink as described in claim 1, characterized in that... Step (2) The thickness of the chromium or titanium coating is 50-500 nm by magnetron sputtering.

5. The method for preparing a high thermal conductivity, low thermal expansion laser bar heat sink as described in claim 1, characterized in that... The thickness of the bottom of the metal shell and the cover plate in step (3) is 0.1-1.0 mm, and the wall thickness of the four sides of the shell is 1.0-5.0 mm.

6. The method for preparing a high thermal conductivity, low thermal expansion laser bar heat sink as described in claim 1, characterized in that... The outer metal thickness of the laser bar heat sink obtained in step (4) is 0.05 to 0.5 mm.

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