Non-silver brazing process for copper needle plate radiator with cavity

Abstract

The invention relates to the field of welding processes for needle plate radiators with cavity fluid heat dissipation, and discloses a non-silver brazing process for a copper needle plate radiator with a cavity, which comprises the following steps: S1, base material selection: firstly, selecting a heat dissipation needle plate 1 and a bottom plate 2 made of a copper material as base materials; s2, base material treatment is conducted, specifically, chemical polishing is conducted on the brazing face A3 and the brazing face B4 of the heat dissipation needle plate 1 and the brazing face B4 of the bottom plate 2; s3, brazing materials are replaced, wherein silver brazing sheets of a brazing face A3 and a brazing face B4 in the original technology are replaced with copper-based brazing sheets without scaling powder; s4, assembling a copper-based brazing sheet: cutting the copper-phosphorus alloy brazing sheet, and pre-arranging the brazing sheet at the joint of the brazing surface A3 and the brazing surface B4; s5, assembling and locking, wherein the heat dissipation needle plate 1 and the bottom plate 2 with the cavity are fixed through a special clamp to form a weldment assembly; and S6, welding forming is conducted, specifically, the assembly is placed in a brazing furnace, and seamless connection of the brazing face A3 and the brazing face B4 is completed. According to the method, the copper-based brazing sheets are used for welding, and the problem of cavity cleanliness caused by soldering flux residues is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of welding processes for needle plate radiators with cavity fluid cooling, and specifically to a non-silver brazing process for copper needle plate radiators with cavities. Background Art

[0002] In the field of electronic device cooling, copper needle plate radiators with cavities are widely used due to their good heat dissipation performance. Through efficient heat conduction and convection methods, such radiators can quickly dissipate the heat generated by electronic devices, ensuring the stable operation of electronic devices, and playing a key role in many devices with strict heat dissipation requirements, such as computers and communication base stations.

[0003] Currently, in the manufacturing process of copper needle plate radiators with cavities, traditional processes mostly use silver brazing sheets combined with soldering fluxes for welding. The specific operation is to join the heat dissipation needle plate and the bottom plate with a cavity (both made of copper), and perform welding through the brazing surface and the silver brazing sheet with the assistance of the soldering flux to form a cooling cavity. During the welding process, the silver brazing sheet melts at an appropriate temperature, fills and connects the gaps between copper components, and the soldering flux plays the role of removing metal surface oxides and reducing the surface tension of the liquid filler metal to facilitate the smooth progress of the welding process.

[0004] However, the existing welding technology based on silver brazing sheets and soldering fluxes has many obvious defects. Firstly, the problem of soldering flux residue is prominent. After welding, it is difficult to completely remove the soldering flux, which seriously affects the cleanliness of the cavity. The cleanliness inside the cavity is crucial for the long-term stable operation of the radiator. The remaining soldering flux may cause problems such as corrosion during subsequent use, reducing the service life of the radiator. Secondly, the soldering flux residue has a negative impact on the surface electroplating process of the radiator. During surface electroplating, poor surfaces are likely to form at the locations where the soldering flux remains, affecting the appearance quality and protective performance of the radiator, and unable to meet the strict requirements of high-end electronic devices for the appearance and protection of radiators. Thirdly, the cost of silver brazing sheets is relatively high. As a relatively expensive metal, silver significantly increases the manufacturing cost of the radiator, which is particularly prominent in large-scale production, limiting the market competitiveness and application scope of the product. Therefore, there is an urgent need for a new brazing process to solve these problems. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a non-silver brazing process for copper needle plate radiators with cavities, which solves the problems that the existing welding technology based on silver brazing sheets and soldering fluxes has soldering flux residue affecting the cavity cleanliness and being prone to cause corrosion and reduce the service life of the radiator.

[0006] To achieve the above object, the present invention is realized through the following technical solutions: A copper-based cavity needle plate type radiator, comprising: a heat dissipation needle plate 1, a brazing surface A3 is fixedly connected to the bottom of the heat dissipation needle plate 1, a bottom plate 2 is arranged below the heat dissipation needle plate 1, a brazing surface B4 is fixedly connected to the top of the bottom plate 2, and the materials of the brazing surface A3 and the brazing surface B4 are both copper-based brazing chips.

[0007] A non-silver brazing process for a copper-based cavity needle plate type radiator comprises the following steps: S1. Substrate selection: First, select the heat dissipation needle plate 1 and the bottom plate 2 made of copper materials as substrates, and the bottom plate 2 is provided with a cooling cavity; S2. Substrate treatment: Chemically polish the brazing surfaces A3 and B4 of the heat dissipation needle plate 1 and the bottom plate 2 to remove surface oxides; S3. Brazing material replacement: Then replace the silver-based brazing chips on the brazing surfaces A3 and B4 in the original process with copper-based brazing chips without flux; S4. Copper-based brazing chip assembly: Cut the copper-phosphorus alloy brazing chip into a width *W =* 1.1 - 1.2 times the width of the brazing surface, and then pre-place the brazing chip at the joint of the brazing surfaces A3 and B4; S5. Assembly and locking: Fix the heat dissipation needle plate 1 and the cavity bottom plate 2 through a special fixture to form a welded component; S6. Welding and forming: Place the component in a brazing furnace, heat it up to 780 ± 10 °C at a rate of 10 - 15 °C / min, keep the temperature for ≥ 15 min, and then cool it to room temperature with the furnace to complete the seamless connection of the brazing surfaces A3 and B4 and form a sealed cooling cavity; S7. Post-treatment and inspection: After brazing, verify the airtightness of the cavity by the helium mass spectrometry leak detection method, and then detect the brazing seam state through a metallographic microscope to determine whether it meets the production standards.

[0008] Preferably, the roughness of the chemical polishing in step S2 is controlled at Ra ≤ 1.6 μm.

[0009] Preferably, the copper-based brazing chip in step S3 is specifically a copper-phosphorus alloy brazing chip, the phosphorus content is 6% - 8%, and the melting point range is 700 - 800 °C.

[0010] Preferably, the fixture parameters in step S5 are: the clamping force ≤ 0.5 MPa to prevent deformation of the copper substrate, and it is made of high-temperature resistant alloy steel, with a tolerance temperature ≥ 1000 °C.

[0011] Preferably, a nitrogen protective atmosphere needs to be filled in the brazing furnace in step S6, and the oxygen concentration is controlled at ≤ 50 ppm to prevent oxidation of the copper material.

[0012] Preferably, the production standards in step S7 include: the leakage rate ≤ 1×10⁻8 Pa·m³ / s, brazing rate ≥ 95%, without crack and hole defects.

[0013] The present invention provides a non - silver brazing process for copper - based cavity needle - plate radiators, with the following beneficial effects: 1. The present invention abandons the use of flux in traditional processes, chemically polishes the surface oxides of the base material, and uses copper - based brazing sheets without flux for welding. This innovation avoids the problem of cavity cleanliness caused by flux residues, fundamentally eliminates the corrosion risk caused by residual flux, greatly improves the long - term stable operation ability of the radiator, and effectively extends its service life.

[0014] 2. The present invention replaces the silver - based brazing sheets in the original process with copper - based brazing sheets with relatively low cost, especially copper - phosphorus alloy brazing sheets. In large - scale production, the raw material cost is significantly reduced.

[0015] 3. Since the present invention does not need to worry about the negative impact of flux residues on the surface electroplating process, when the radiator manufactured by the new brazing process is electroplated on the surface, there will be no surface defects formed due to flux residues. It can ensure that the radiator has good appearance quality and protective performance. Description of the Drawings

[0016] Figure 1 is the process flow chart of the present invention; Figure 2 is the schematic cross - sectional structure diagram of the heat - dissipating needle - plate of the present invention.

[0017] Among them, 1. Heat - dissipating needle - plate; 2. Bottom plate; 3. Brazing surface A; 4. Brazing surface B. Specific Embodiments

[0018] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than 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 work belong to the scope of protection of the present invention.

[0019] Embodiment: Please refer to the attached Figure 1 - attached Figure 2 , the embodiment of the present invention provides a copper - based cavity needle - plate radiator, including: a heat - dissipating needle - plate 1, a brazing surface A3 is fixedly connected to the bottom of the heat - dissipating needle - plate 1, a bottom plate 2 is arranged below the heat - dissipating needle - plate 1, and a brazing surface B4 is fixedly connected to the top of the bottom plate 2.

[0020] The materials of the brazing surface A3 and the brazing surface B4 are both copper - based brazing sheets.

[0021] A non-silver brazing process for a copper cavity needle plate radiator, comprising the following steps: S1. Substrate selection: First, select a heat dissipation needle plate 1 and a bottom plate 2 made of copper material as substrates, and a cooling cavity is provided on the bottom plate 2; S2. Substrate treatment: Chemically polish the brazing surfaces 3 and 4 of the heat dissipation needle plate 1 and the bottom plate 2 to remove surface oxides, and control the roughness at Ra ≤ 1.6 μm; S3. Brazing material replacement: Then replace the silver brazing sheets on the brazing surfaces 3 and 4 in the original process with copper-based brazing sheets without flux. The copper-based brazing sheets are specifically copper-phosphorus alloy brazing sheets, with a phosphorus content of 6% - 8% and a melting point range of 700 - 800 °C, so that self-cleaning can be achieved without adding flux during the brazing process; S4. Assembly of copper-based brazing sheets: Cut the copper-phosphorus alloy brazing sheet into a width *W* = 1.1 - 1.2 times the width of the brazing surface, and then pre-place the brazing sheet at the joint of the brazing surfaces 3 and 4; S5. Assembly and locking: Fix the heat dissipation needle plate 1 and the cavity bottom plate 2 through a special fixture to form a welded component. The fixture parameters are: the clamping force ≤ 0.5 MPa to prevent deformation of the copper substrate, and it is made of high-temperature resistant alloy steel, with a tolerance temperature ≥ 1000 °C; S6. Welding and forming: Place the component in a brazing furnace, heat it up to 780 ± 10 °C at a rate of 10 - 15 °C / min, keep it warm for ≥ 15 min, and then cool it to room temperature with the furnace to complete the seamless connection of the brazing surfaces 3 and 4, forming a sealed cooling cavity. The brazing furnace needs to be filled with a nitrogen protective atmosphere, and the oxygen concentration is controlled at ≤ 50 ppm to prevent oxidation of the copper material; S7. Post-treatment and inspection: After brazing, verify the airtightness of the cavity through the helium mass spectrometry leak detection method, and then detect the brazing seam state through a metallographic microscope to determine whether it meets the production standards. The production standards include: the leakage rate ≤ 1×10⁻ 8 Pa·m³ / s, the brazing rate ≥ 95%, and there are no crack and hole defects.

[0022] Comparative experiment: To verify the performance differences between the non-silver brazing process (experimental group) and the traditional silver brazing process (control group) of the present invention, the following comparative experiment was designed: 1. Experimental setup 2. Experimental steps Step 1: Substrate preparation and pretreatment Both groups of substrates were processed as follows: Chemically polish the brazing surface (H 2 SO 4 + H 2 O 2Solution, time 30 s); Surface roughness Ra ≤ 1.6 μm, ultrasonic cleaning with acetone (20 min).

[0023] Step 2: Brazing process Experimental group: Assemble and braze the copper-based brazing chips according to the S4 - S6 process (nitrogen protection).

[0024] Control group: Apply boric acid flux (thickness 0.1 mm), then lay the silver-based brazing chips, lock with the same fixture, and there is no protective atmosphere in the brazing furnace.

[0025] Step 3: Cooling and post-treatment Both groups are taken out after being cooled in the furnace to below 50°C. The control group uses ultrasonic cleaning with deionized water (20 min) to remove the flux.

[0026] Step 4: Performance testing Inspect airtightness, brazing rate, and defect rate according to the S7 standard. At the same time, supplement the following tests: Flux residue detection (control group): Use EDX energy spectrum analysis to analyze the surface residual elements (detect the contents of B, K, and Na); Shearing strength of the brazing seam: Test with a universal testing machine (according to ASTM D1002 standard); Surface electroplating yield: Observe the pitting and peeling area after nickel plating (qualified if the area ratio ≤ 1%).

[0027] 3. Comparison of experimental data 4. Analysis of key results Flux residue: Due to the self-deoxidation property of the copper-phosphorus brazing chips in the experimental group, the surface cleanliness meets the electroplating requirements; The residual borate in the control group causes electroplating pitting (surface defect rate ≥ 15%).

[0028] Brazing seam performance: The denseness of the brazing seam in the experimental group is improved (porosity ≤ 0.5%, while in the control group ≥ 2.5%), and the shearing strength is increased by 18% - 25%.

[0029] Cost and environmental protection: The material cost of the experimental group is reduced by 70% - 75%; Due to the excessive discharge of cleaning wastewater in the control group (COD ≥ 200 mg / L), no wastewater is generated in the experimental group.

[0030] 5. Conclusion The copper-based brazing process of the present invention is comprehensively superior to the traditional silver brazing in terms of reliability, economy, and environmental protection, and is particularly suitable for mass production of power electronic radiators with high cleanliness requirements.

[0031] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A copper pin plate heat sink with cavity, characterized in that: include: A heat dissipation needle plate (1), wherein a brazing surface A (3) is fixedly connected to the bottom of the heat dissipation needle plate (1), a bottom plate (2) is arranged below the heat dissipation needle plate (1), and a brazing surface B (4) is fixedly connected to the top of the bottom plate (2), and the brazing surface A (3) and the brazing surface B (4) are both made of copper-based brazing sheets.

2. A non-silver brazing process for a copper cavity pin plate type heat sink according to claim 1, characterized in that: The following steps are involved: S1. Substrate selection: first select a heat dissipation pin plate (1) and a base plate (2) made of copper material as the substrate, and a cooling cavity is provided on the base plate (2); S2. Substrate treatment: chemically polishing the brazing surface A (3) and the brazing surface B (4) of the heat dissipation pin plate (1) and the base plate (2) to remove surface oxides; S3. Replacement of brazing material: Replace the silver brazing sheet of the brazing surface A (3) and the brazing surface B (4) in the original process with a copper-based brazing sheet without flux; S4. Copper-based brazing sheet assembly: The copper-phosphorus alloy brazing sheet is cut to a width * W = * 1.1 to 1.2 times the width of the brazing surface, and then the brazing sheet is pre-placed at the joint of the brazing surface A (3) and the brazing surface B (4); S5. Assembly and locking: Fix the heat dissipation pin plate (1) and the cavity bottom plate (2) by a special fixture to form a weldment assembly; S6. Welding: Place the assembly in a brazing furnace and heat it to 780±10℃ at a rate of 10~15℃ / min for ≥15min, then cool it to room temperature in the furnace to complete the seamless connection between the brazing surface A (3) and the brazing surface B (4), forming a closed cooling cavity; S7. Post-processing and inspection: After brazing is completed, the air tightness of the cavity is verified by helium mass spectrometry leak detection, and then the state of the brazing seam is detected by metallographic microscope to determine whether it meets the production standards.

3. A non-silver brazing process for a copper cavity pin plate type heat sink according to claim 2, characterized in that: The chemical polishing roughness in step S2 is controlled to be Ra≤1.6 μm.

4. The non-silver brazing process for a copper cavity pin plate type heat sink according to claim 2 is characterized in that: The copper-based brazing sheet in step S3 is specifically a copper-phosphorus alloy brazing sheet with a phosphorus content of 6% to 8% and a melting point range of 700 to 800°C.

5. The non-silver brazing process for a copper cavity pin plate type heat sink according to claim 2 is characterized in that: The clamp parameters in step S5 are: clamping force ≤ 0.5 MPa to prevent deformation of the copper substrate, made of high-temperature resistant alloy steel, and withstanding temperature ≥ 1000°C.

6. The non-silver brazing process for a copper cavity pin plate type heat sink according to claim 2 is characterized in that: In step S6, the brazing furnace needs to be filled with a nitrogen protective atmosphere, and the oxygen concentration is controlled to be ≤50ppm to prevent oxidation of the copper material.

7. The non-silver brazing process for copper cavity pin plate type heat sink according to claim 2 is characterized in that: The production standards in step S7 include: leakage rate ≤ 1×10⁻ 8 Pa·m³ / s, brazing rate ≥95%, no cracks and holes.

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