A production process of copper strip for a vapor chamber radiator

Abstract

The application discloses a production process of a copper strip of a vapor chamber radiator, and the process route and specific process parameters of the production of the copper strip of the vapor chamber through the design of the upper continuous extrusion mode can obtain the copper strip with low oxygen content and compact and uniform internal organization, effectively solve the air leakage phenomenon caused by the loose organization and layering defects of the copper strip produced by the traditional process level continuous casting after high-temperature sintering, and can control the oxygen content to avoid the problem of uneven sintering surface bubbling.

Description

Technical Field

[0001] This invention belongs to the technical field of 5G base station heat sink materials, specifically relating to a production process of copper strip for a heat spreader. Background Technology

[0002] With the development of technology, electronic products are becoming increasingly diversified in function and more efficient in processing tasks, while also becoming thinner and lighter. This has led to a significant increase in the heat generated per unit area by chips. How to solve the heat dissipation problem is a major issue that must be addressed today. Currently, the high thermal conductivity devices used in computer and electronic products are mainly heat pipes and vapor chambers. However, heat pipes are cylindrical in shape, with a very small contact area with the heat source or heat dissipation device. Therefore, flat vapor chambers are currently the most commonly used. Vapor chambers are easy to fit onto the chip surface, have a large heat dissipation surface, and have a certain degree of flexibility in shape. They can be designed according to the heat dissipation configuration of different electronic products. Moreover, compared with circular heat pipes, they have a greater heat transfer limit and can more effectively dissipate heat into the environment.

[0003] The vapor chamber mainly comprises three components: a sealed container, a capillary structure, and a working fluid. The sealed container is vacuum-sealed, and its sidewalls are brass frames containing sealing grooves and water injection pipes. A round hole is drilled in the center of the short side of the brass frame to insert a filling tube. Both the upper and lower base plates are made of oxygen-free copper plates, and the capillary structure is sintered onto the lower base plate. The manufacturing process involves sintering a copper mesh along with the lower base plate. Spherical and irregular copper powders are filled into the copper mesh for sintering. The temperature rise curve during sintering is 90 minutes to 850℃.

[0004] Because oxygen-free copper plates require high-temperature sintering, the material structure and microstructure must be carefully controlled. After high-temperature sintering, defects such as loose microstructure and delamination must be avoided to prevent gas leakage. Simultaneously, oxygen content must be controlled to prevent surface blistering and unevenness after sintering. Current technologies generally employ horizontal continuous casting and hot rolling. While horizontal continuous casting produces billets with low oxygen content, their grains are mostly equiaxed and intermediate columnar, resulting in a less dense and uniform microstructure compared to hot-rolled billets, making them prone to gas leakage due to loose microstructure and delamination. Although hot-rolled billets, through secondary heating and hot rolling, can effectively improve casting defects and achieve a uniform and dense metal microstructure due to the combined effects of deformation speed, degree of deformation, and deformation temperature, the furnace structure and processing methods make it difficult to achieve a low oxygen content, leading to surface blistering problems after copper strip sintering.

[0005] In recent years, many domestic enterprises have introduced the upward continuous casting and extrusion method for producing copper strip. Under the continuous extrusion at high temperature and high pressure, the as-cast structure of the upward copper rod is transformed into a recrystallized structure with fine and uniform grains. It is dense and uniform with excellent mechanical properties. Moreover, using the upward continuous casting copper rod as raw material, the upward continuous casting process can produce copper strip billets with an oxygen content of 10ppm. It can simultaneously meet the requirements of dense structure and low oxygen content for high-temperature sintering uniform plate copper strips.

[0006] Therefore, adopting the upward continuous extrusion method to produce homogenized copper strip is the optimal way to solve the current quality problems of homogenized copper strip for high-temperature sintering. Developing the production process of homogenized copper strip by upward extrusion is an inevitable direction for copper strip enterprises and an inevitable requirement of the market. Summary of the Invention

[0007] The purpose of this invention is to provide a manufacturing process for copper strips in a vapor chamber radiator.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention includes the following steps:

[0009] A manufacturing process for copper strips in a vapor chamber radiator, the specific process flow is as follows:

[0010] (1) Raw material ratio: 100% electrolytic copper is used as raw material;

[0011] (2) Casting copper rods in the upper drawing furnace: After preheating the electrolytic copper plate on the furnace mouth or furnace cover for 3~15 minutes, it is added to the melting furnace through the automatic feeder. At the same time, dried charcoal is added to the melting furnace to cover the copper liquid. Then, the φ30mm baked crystallizer is inserted into the copper liquid and installed on the traction machine mounting plate. Then, the servo system is turned on to start drawing the rod. The temperature difference between the inlet and outlet cooling water is adjusted to 12~15℃. The drawing rod is removed and the drawn copper rod is guided into the guide wheel frame, intermediate bracket, limit device and winding machine. When the weight of the copper rod reaches 6 tons, it is unwound.

[0012] (3) Continuous extrusion of copper billets: 8-10 φ30mm copper rods with a length of 400mm are preheated and fed into the extruder. Then the speed of the extruder is slowly increased to 2.5-2.8r / min. When the current is less than 900A, the φ30mm copper rod material is continuously fed in. Then the product cooling pump is turned on and the speed of the extruder spindle is increased to 4.5r / min. At the same time, the nitrogen protection device and the drying device are turned on. The extruded copper rods are passed through the copper rod flattening machine, the leveling machine and the centerless winding machine in sequence to form copper strip rolls. Finally, 0.6mm backing paper is added to the surface of the copper strip roll.

[0013] (4) Milling: The copper strip coil with a thickness of 12.0 mm after extrusion is milled on its upper and lower surfaces using a milling machine;

[0014] (5) Rough rolling: The copper strip coil with a milled surface of 10.4 mm is subjected to multiple rough rolling passes and rolled to 2.3 mm before unwinding;

[0015] (6) Rewinding: The copper strip coil with a thickness of 2.3 mm after rough rolling is rewound using a rewinding machine;

[0016] (7) Bell-type furnace annealing: The copper strip coil with a thickness of 2.3 mm after rewinding is annealed in a bell-type annealing furnace;

[0017] (8) First cleaning: The copper strip coil with a thickness of 2.3mm after annealing in the bell furnace is processed by pickling, rinsing with clean water, polishing, rinsing with hot water, passivation, drying and rewinding in sequence;

[0018] (9) Intermediate rolling: The copper strip coil with a thickness of 2.3mm after one cleaning is rolled in multiple passes until the thickness is the specified thickness of the product. The finished copper strip coil is then unrolled.

[0019] (10) Air cushion furnace annealing: The finished copper strip coil after intermediate rolling is processed by alkali washing, air cushion annealing, pickling, water rinsing, polishing, hot water rinsing, passivation, drying and rewinding in sequence.

[0020] (11) Slitting, packaging and delivery by slitting machine: The copper strip coils annealed by air cushion furnace are slitted and delivered.

[0021] Furthermore, the composition of the electrolytic copper in step (1) should meet the data in Table 1 of the national standard GB / T467-2010.

[0022] Further, in step (2), the copper liquid level must be less than the maximum value of 600 mm; the copper liquid temperature is 1150℃±10℃; the charcoal covering thickness is 80~100 mm. If the charcoal covering thickness is less than 80 mm, fresh charcoal should be added first before cleaning; the crystallizer head assembly requires that the graphite mold be screwed into the cooling inner sleeve of the crystallizer, and the screwing depth must reach the contact with the head of the inner tube of the crystallizer. The cooling outer sleeve of the crystallizer is then tied tightly with alkali-free glass fiber tape, and a slag wool insulation sleeve is installed. Then, a slag wool insulation sleeve is put on the outside of the insulation sleeve. A graphite protective sleeve is used. The gap at the interface where the graphite mold passes through the protective sleeve is filled with asbestos thread and sealed with refractory mortar to prevent copper liquid from seeping in. Asbestos packing is inserted into the sealing sleeve in the crystallizer head, pressed in with a clamping ring, and then tightened with a clamping sleeve. A guide head is attached to the lower end of the guide rod and tightened. The lower end of the guide rod is then inserted into the crystallizer, with the guide head extending 5-10 mm beyond the bottom of the graphite mold. The depth to which the crystallizer is inserted into the copper liquid is 150-170 mm. The cooling water inlet temperature is 25-35℃, and the water pressure is 0.28-0.4 MPa.

[0023] Further, the preheating mentioned in step (3) is to heat the copper rod to 680~700℃.

[0024] Furthermore, in step (4), the milling speed is 3 m / min, the milling amount on the upper and lower surfaces of the copper strip is 0.8 mm each, and the surface roughness after milling is controlled within 1.6 Ra / um.

[0025] Furthermore, in step (5), the roughing mill has a specification of Φ330 / Φ715×600mm, a rolling speed of 180m / min, and uses emulsion lubrication with an emulsion mass concentration of 3%.

[0026] Furthermore, in step (6), the rewinding speed is ≤80m / min and the rewinding tension is 2800~3500N.

[0027] Furthermore, the specific annealing process in step (7) is to heat the copper strip from room temperature to 380°C for 3.5 hours, then keep it at that temperature for 5 hours, and finally cool it to room temperature after the heat preservation is completed.

[0028] Furthermore, in step (8), the acid pickling uses sulfuric acid with a mass concentration of 12%; the polishing uses 240 mesh single-strand silicon carbide at a rotation speed of 600 r / min; and the cleaning speed is 30 m / min.

[0029] Furthermore, in step (9), the specifications of the rolling mill are Φ230 / Φ600×560mm, and it adopts full oil rolling with a rolling speed of 240m / min.

[0030] Further, the alkaline washing in step (10) involves adding 12.5L of neutral degreasing agent per shift at room temperature; the air cushion annealing has an annealing temperature of 600℃, an annealing speed of 20m / min, a fan speed of 1370r / min, a gas composition of 1.5~3%H2+98.5~96%N2, O2 content <5PPM, residual ammonia <3PPM, an atmosphere dew point <-60℃, and a gas flow rate of 100~120m³ / min. 3 / h; the pickling uses sulfuric acid with a mass concentration of 9~14%; the passivation is carried out at 70~90℃ and with a conductivity of <500us / cm using a passivation solution with a concentration of 0.05~0.1%, wherein the passivation solution is a mixture of copper passivating agent and deionized water.

[0031] The beneficial effects of this invention are as follows:

[0032] This invention designs a process route and specific process parameters for producing uniformly heated copper strips using an upward continuous extrusion method. This method can obtain copper strips with low oxygen content and dense and uniform internal structure, effectively solving the problem of air leakage caused by defects such as loose structure and delamination after high-temperature sintering of copper strips produced by horizontal continuous casting. At the same time, it can control the oxygen content to avoid the problem of uneven surface blistering after sintering. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to the embodiments. Example

[0034] Taking a heat spreader copper strip product of grade Tu, size 0.8×400mm, and state M as an example, the specific production steps are as follows:

[0035] (1) Raw material ratio: 100% electrolytic copper is used;

[0036] (2) Upper drawing rod: The raw materials after the proportioning in step (1) are cast into a φ30mm copper rod using an upper drawing furnace;

[0037] (3) Continuous extrusion: The φ30mm copper rod material drawn from step (2) is extruded into a 12×420mm copper strip coil;

[0038] (4) Milling: The copper strip coil with a thickness of 12.0 mm after extrusion in step (3) is milled on the upper and lower surfaces. The milling speed is 3 m / min, the milling amount on the upper and lower surfaces of the strip is 0.8 mm each, the surface roughness after milling is controlled within 1.6 Ra / um, and the milled size is 10.4*420 mm.

[0039] (5) Rough rolling: The copper strip coil with a diameter of 10.4 mm after milling in step (4) is subjected to multiple rough rolling passes. After rolling to 2.3 mm, the coil is unloaded. The rough rolling mill has a diameter of Φ330 / Φ715×600 mm and a rolling speed of 180 m / min. The rough rolling mill uses emulsion lubrication with an emulsion mass concentration of 3%. The rolled size is 2.3*416 mm.

[0040] (6) Rewinding: The copper strip coil with a thickness of 2.3mm after rough rolling in step (5) is rewinded to release stress and prevent annealing adhesion. The specific rewinding parameters are: speed ≤80m / min, rewinding tension controlled at 2800-3500N;

[0041] (7) Bell-type furnace annealing: The copper strip coil with a thickness of 2.3 mm after rough rolling in step (6) is annealed in a bell-type annealing furnace. After 3.5 hours, the temperature is raised to 380℃ and then held for 5 hours. After the holding period, the furnace is cooled to room temperature and the coil is taken out. The annealed coil is in a soft state.

[0042] (8) First cleaning: The copper strip coil with a thickness of 2.3 mm after annealing in the bell furnace in step (7) is processed by pickling, rinsing with clean water, polishing, rinsing with hot water, passivation, drying and rewinding in sequence. Among them, sulfuric acid pickling is used with a sulfuric acid mass concentration of 12%; polishing is done with a 240 mesh single-strand wire brush with silicon carbide bristles, the polishing speed is 600 r / min, and the cleaning speed is 30 m / min.

[0043] (9) Intermediate rolling: The copper strip coil with a thickness of 2.3mm after one cleaning in step (8) is rolled in multiple passes until the thickness is 0.8mm and then unloaded. The intermediate rolling mill has a specification of Φ230 / Φ600×560mm, uses full oil rolling, and the rolling speed is 240m / min. The product specification after rolling is 0.8×420mm.

[0044] (10) Air cushion furnace annealing: The copper strip coil with a thickness of 0.8 mm after rolling in step (9) is processed by alkali washing, air cushion annealing, acid washing, water rinsing, polishing, hot water rinsing, passivation, drying and winding in sequence. The air cushion annealing adopts a heating zone of 600 degrees, an annealing speed of 20 m / min, a fan speed of 1370 r / min, a gas composition of 1.5~3% H2 + 98.5~96% N2, O2 < 5 PPM, residual ammonia < 3 PPM, an atmosphere dew point < -60℃, and a gas flow rate controlled at 100~120 m³ / min. 3 / h. After annealing, the product performance was tested and found to meet customer requirements;

[0045] (11) Slitting, packaging and delivery by slitting machine: The copper strip coils annealed in the air cushion furnace in step (10) are slitting and delivered.

[0046] The prepared heat spreader copper strip was tested for performance indicators. The specific data are shown in Table 1.

[0047] Table 1. Test results of various performance indicators of copper strip for heat exchange plate.

[0048] index Test results chemical composition Cu:99.9736%S:0.0005%P:0.0005%O:0.0004% Thickness tolerance 0.798mm Surface defects Smooth surface, free of stains; dense texture, free of bubbles and peeling. Burr height ≤10mm Finished product grain size: Grain size: 0.0102mm plate type ≤3I Main performance indicators: Vickers hardness Vickers Hardness: 56.1 HV; Elongation: 41.7%; Tensile Strength: 241 MPa; Electrical Conductivity: 100.3% IACS High-temperature sintering test No air leakage or surface bubbling

[0049] As can be seen from Table 1, the heat spreader copper strip prepared by the present invention has very few impurities; extremely low thickness deviation; no obvious surface defects; and can form a suitable grain size, which significantly improves the mechanical properties of the heat spreader copper strip; at the same time, no problems such as gas leakage and surface bubbles are generated under high temperature sintering conditions.

Claims

1. A manufacturing process for copper strips in a vapor chamber radiator, characterized in that: The specific process flow is as follows: (1) Raw material ratio: 100% electrolytic copper is used as raw material; (2) Casting copper rods in the upper drawing furnace: After preheating the electrolytic copper plate on the furnace mouth or furnace cover for 3~15 minutes, it is added to the melting furnace through the automatic feeder. At the same time, dried charcoal is added to the melting furnace to cover the copper liquid. Then, the φ30mm baked crystallizer is inserted into the copper liquid and installed on the traction machine mounting plate. Then, the servo system is turned on to start drawing the rod. The temperature difference between the inlet and outlet cooling water is adjusted to 12~15℃. The drawing rod is removed and the drawn copper rod is guided into the guide wheel frame, intermediate bracket, limit device and winding machine. When the weight of the copper rod reaches 6 tons, it is unwound. (3) Continuous extrusion of copper billets: 8-10 φ30mm copper rods with a length of 400mm are preheated and fed into the extruder. Then the speed of the extruder is slowly increased to 2.5-2.8r / min. When the current is less than 900A, the φ30mm copper rod material is continuously fed in. Then the product cooling pump is turned on and the speed of the extruder spindle is increased to 4.5r / min. At the same time, the nitrogen protection device and the drying device are turned on. The extruded copper rods are passed through the copper rod flattening machine, the leveling machine and the centerless winding machine in sequence to form copper strip rolls. Finally, 0.6mm backing paper is added to the surface of the copper strip roll. (4) Milling: The copper strip coil with a thickness of 12.0 mm after extrusion is milled on its upper and lower surfaces using a milling machine; (5) Rough rolling: The copper strip coil with a milled surface of 10.4 mm is subjected to multiple rough rolling passes and rolled to 2.3 mm before unwinding; (6) Rewinding: The copper strip coil with a thickness of 2.3 mm after rough rolling is rewound using a rewinding machine; (7) Bell-type furnace annealing: The copper strip coil with a thickness of 2.3 mm after rewinding is annealed in a bell-type annealing furnace; (8) First cleaning: The copper strip coil with a thickness of 2.3mm after annealing in the bell furnace is processed by pickling, rinsing with clean water, polishing, rinsing with hot water, passivation, drying and rewinding in sequence; (9) Intermediate rolling: The copper strip coil with a thickness of 2.3mm after one cleaning is rolled in multiple passes until the thickness is the specified thickness of the product. The finished copper strip coil is then unrolled. (10) Air cushion furnace annealing: The finished copper strip coil after intermediate rolling is processed by alkali washing, air cushion annealing, pickling, water rinsing, polishing, hot water rinsing, passivation, drying and rewinding in sequence. (11) Slitting, packaging and delivery by slitting machine: The copper strip coils annealed by air cushion furnace are slitted and delivered; Among them, (2) the copper liquid level must be less than the maximum value of 600mm; the copper liquid temperature is 1150℃±10℃; the charcoal covering thickness is 80~100mm. If the charcoal covering thickness is less than 80mm, fresh charcoal should be added first and then the ash removal treatment should be carried out; the crystallizer head assembly requirements are that the graphite mold is screwed into the cooling inner sleeve of the crystallizer, and the screwing depth must reach the contact with the head of the inner tube of the crystallizer. The cooling outer sleeve of the crystallizer is tied tightly with alkali-free glass fiber tape, and a slag wool heat insulation sleeve is installed. Then, a graphite mold is put on the outside of the heat insulation sleeve. The protective sleeve is filled with asbestos thread at the interface gap where the graphite mold passes through the protective sleeve, and then sealed with refractory mortar to prevent copper liquid from seeping in. Asbestos packing is inserted into the sealing sleeve in the head of the crystallizer, pressed in with a clamping ring, and then tightened with a clamping sleeve. A guide head is attached to the lower end of the guide rod and tightened. The lower end of the guide rod is then inserted into the crystallizer, with the guide head extending 5-10mm beyond the bottom of the graphite mold. The depth to which the crystallizer is inserted into the copper liquid is 150-170mm. The cooling water inlet temperature is 25-35℃, and the water pressure is 0.28-0.4MPa. Among them, the preheating mentioned in (3) is to heat the copper rod to 680~700℃; Among them, the specific annealing process in (7) is to raise the copper strip coil from room temperature to 380°C in 3.5 hours, then keep it at that temperature for 5 hours, and finally cool it to room temperature after the holding time is over. Among them, (10) refers to alkaline washing, which involves adding 12.5L of neutral degreasing agent per shift at room temperature; the air cushion annealing has an annealing temperature of 600℃, an annealing speed of 20m / min, a fan speed of 1370r / min, a gas composition of 1.5~3%H2+98.5~96%N2, O2 content <5PPM, residual ammonia <3PPM, an atmosphere dew point <-60℃, and a gas flow rate of 100~120m³ / min. 3 / h; the pickling uses sulfuric acid with a mass concentration of 9~14%; the passivation is carried out at 70~90℃ and with a conductivity of <500us / cm using a passivation solution with a concentration of 0.05~0.1%, wherein the passivation solution is a mixture of copper passivating agent and deionized water.

2. The manufacturing process of copper strip for a heat spreader as described in claim 1, characterized in that: (4) The milling speed is 3m / min, the milling amount on the upper and lower surfaces of the copper strip is 0.8mm each, and the surface roughness after milling is controlled within 1.6Ra / um.

3. The manufacturing process of copper strip for a heat spreader as described in claim 1, characterized in that: (5) The specifications of the intermediate roughing mill are Φ330 / Φ715×600mm, the rolling speed is 180m / min, the roughing mill uses emulsion lubrication, and the emulsion mass concentration is 3%.

4. The manufacturing process of copper strip for a heat spreader as described in claim 1, characterized in that: (6) The rewinding speed is ≤80m / min and the rewinding tension is 2800~3500N.

5. The manufacturing process of copper strip for a heat spreader as described in claim 1, characterized in that: (8) The acid pickling uses sulfuric acid with a mass concentration of 12%; the polishing uses 240 mesh single-strand silicon carbide at a speed of 600 r / min; the cleaning speed is 30 m / min.

6. The manufacturing process of copper strip for a heat spreader as described in claim 1, characterized in that: (9) The specifications of the medium-sized rolling mill are Φ230 / Φ600×560mm. It adopts full oil rolling and the rolling speed is 240m / min.