Oxygen-free copper for ceramic copper clad and vacuum melting method thereof

Abstract

The application provides oxygen-free copper for ceramic copper cladding and a vacuum smelting method thereof, and the vacuum smelting method comprises the following steps: (1) placing electrolytic copper base material into a crucible of a vacuum induction furnace, and placing metal additive into a charging bin of the vacuum induction furnace; the metal additive comprises Ti, Co, Ni and Ag; (2) after the vacuum induction furnace is vacuumized, the vacuum induction furnace is heated to a first temperature, and the electrolytic copper base material in the crucible is preheated; the heating is continuously performed to a second temperature, the electrolytic copper base material in the crucible is melted, and electrolytic copper melt is obtained; (3) the metal additive is added into the electrolytic copper melt, alloying treatment is performed, and the oxygen-free copper for ceramic copper cladding is obtained by casting. The vacuum smelting method is simple in operation, and the oxygen-free copper prepared by the method has fine crystal grains after being welded with ceramics at high temperature, and meets the use requirement of ceramic copper cladding material.

Description

Technical Field

[0001] This invention relates to the field of metal material preparation technology, and in particular to an oxygen-free copper for ceramic copper plating and its vacuum melting method. Background Technology

[0002] Ceramic-clad copper is a technology that directly bonds oxygen-free copper to ceramic substrates such as Al2O3 or AlN at high temperatures. Ceramic-clad copper laminates possess the high thermal conductivity, high electrical insulation, high mechanical strength, and low expansion properties of ceramics, as well as the high electrical conductivity and excellent welding performance of oxygen-free copper, making them ideal for use as substrate materials for power devices. Typically, the welding temperature for ceramic-clad copper is between 1065-1083℃. At such high temperatures, the grains of ordinary oxygen-free copper grow rapidly, reaching hundreds of micrometers or even millimeters in size, forming a texture similar to "orange peel." This negatively impacts the weld strength, electrical and thermal conductivity of the final ceramic-clad copper laminate.

[0003] CN115213076A discloses a production process for palladium-bonded oxygen-free copper wires used in microelectronic packaging. The process involves preparing single-crystal oxygen-free copper rods using a dual-path hot-casting equipment. After drawing, a dense, smooth, and uniform nano-palladium layer is deposited on the surface of the oxygen-free copper wire using an environmentally friendly immersion plating method. The delivery rate of the plating solution is controlled by a sample pump, and the optimal delivery rate and drying temperature can be selected to optimize the plating quality.

[0004] CN108962860A discloses a method for preparing an oxidation-resistant bonded copper wire material, comprising the following steps: raw material preparation, firstly purifying the raw copper wire material by using a vacuum furnace, creating a vacuum in the furnace, melting the raw copper material into high-purity copper with a purity greater than 99.95%, stirring, adding zinc powder and manganese powder to the molten copper solution, stirring the mixture until the zinc powder and manganese powder are fully fused with the copper solution, cooling and processing, allowing the mixture to stand for 30-60 minutes until the mixture is in an alloy state, rough drawing and annealing, placing the alloy state mixture into a copper wire making mold for rough drawing, and annealing the rough drawn copper wire at a temperature of 480 degrees Celsius.

[0005] CN119216399A discloses a process for refining the grains of oxygen-free copper plates. The process includes the following steps: melting an electrolytic copper plate in a furnace, covering the surface with charcoal, and then performing semi-continuous casting to produce oxygen-free copper ingots; preheating the oxygen-free copper ingots in a holding furnace at a temperature of 800-900℃ for 2-3 hours; and then upsetting and drawing the preheated ingots, with an upsetting deformation of 50%-60% and a drawing length of 150%-160% of the original length, repeated 3-4 times. The process begins with warm forging and squaring at 700-750℃. The ingot is then uprooted to 50%-60% of its original length and squared to the desired billet length, maintaining a final forging temperature ≥700℃. The billet is then cooled to room temperature, and cold forging begins. This process involves multiple passes, with each pass reducing the ingot by 10%-15%, resulting in a final cold forging deformation of 30-60%. The cold-forged oxygen-free copper billet undergoes aging heat treatment at 350-450℃ for 1-2 hours. After annealing, it is air-cooled to obtain oxygen-free copper sheet.

[0006] However, the above-mentioned method for preparing oxygen-free copper is complex and the copper obtained is not suitable for ceramic copper-clad laminates. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides an oxygen-free copper for ceramic cladding and its vacuum melting method. The method uses vacuum induction melting to melt electrolytic copper base material and then adds metal additives for micro-alloying to prepare oxygen-free copper for ceramic cladding. After being welded to ceramic at high temperature, the copper has fine grains, which meets the requirements for ceramic cladding.

[0008] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a vacuum melting method for oxygen-free copper used in ceramic copper cladding, the vacuum melting method comprising the following steps: (1) Place the electrolytic copper base material into the crucible of the vacuum induction furnace and place the metal additives into the charging chamber of the vacuum induction furnace; the metal additives include Ti, Co, Ni and Ag; (2) After the vacuum induction furnace is evacuated, it is heated to the first temperature to preheat the electrolytic copper base material in the crucible; then it is heated to the second temperature to melt the electrolytic copper base material in the crucible to obtain electrolytic copper melt. (3) Add metal additives to the electrolytic copper melt, perform alloying treatment, and then cast to obtain the oxygen-free copper for ceramic copper coating.

[0009] The vacuum melting method for oxygen-free copper for ceramic cladding described in this invention involves melting electrolytic copper base material in a vacuum induction furnace and achieving micro-alloying by adding specific metals to the molten electrolytic copper base material. This results in oxygen-free copper with fine grains after welding to ceramics at high temperatures, meeting the requirements for ceramic cladding. The role of the metal additives in this invention is to refine the grains. Adding too much metal additive to the molten electrolytic copper will reduce the purity of the resulting oxygen-free copper for ceramic cladding. Adding too little metal additive will result in large grains in the oxygen-free copper after welding to ceramics at high temperatures, affecting the quality of the ceramic cladding material. The metal additives described in this invention include Ti, Co, Ni, and Ag. The absence of any one of these metals will result in large grains in the final oxygen-free copper for ceramic cladding after welding to ceramics at high temperatures.

[0010] Preferably, the oxygen content of the oxygen-free copper used for ceramic cladding is <5ppm, for example, it can be 0.1ppm, 0.5ppm, 1ppm, 2ppm, 3ppm or 4.9ppm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0011] Preferably, the content of Ag in the oxygen-free copper used for ceramic cladding is 10-40 ppm, for example, it can be 10 ppm, 15 ppm, 20 ppm, 25 ppm, 35 ppm or 40 ppm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0012] The Ti content is 10-20 ppm, for example, it can be 10 ppm, 12 ppm, 14 ppm, 16 ppm, 18 ppm or 20 ppm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0013] The Co content is 10-20 ppm, for example, it can be 10 ppm, 12 ppm, 14 ppm, 16 ppm, 18 ppm or 20 ppm, but it is not limited to the listed values. Other unlisted values ​​within this range also apply.

[0014] The Ni content is 5-15 ppm, for example, it can be 5 ppm, 7 ppm, 9 ppm, 11 ppm, 13 ppm or 15 ppm, but it is not limited to the listed values. Other unlisted values ​​within this range also apply.

[0015] Preferably, the purity of the electrolytic copper base material in step (1) is ≥6N, for example, it can be 6N, 6.2N, 6.3N, 6.5N, 7N or 7.5N, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] The impurities contained in the electrolytic copper base material of the present invention include Ag, Fe, O, S, Ni, Zn, Sn and Pb, etc., and the purity of the electrolytic copper base material is ≥6N.

[0017] Preferably, in step (2), the vacuum induction furnace is evacuated to a vacuum degree ≤10. -3 Pa, for example, could be 10. -3 Pa, 8×10 -4 Pa, 7×10 -4 Pa, 5×10 -4 Pa, 4×10 -4 Pa, 3×10 -4 Pa or 1×10 -4 Pa, etc., but not limited to the listed values; other unlisted values ​​within this range also apply.

[0018] Preferably, the vacuum induction furnace of the present invention is evacuated to a vacuum degree ≤10. -3 The primary function of the vacuum chamber (Pa) is to remove harmful gases such as hydrogen, nitrogen, and oxygen, ensuring that the oxygen content of the final oxygen-free copper used in ceramic cladding meets the requirements. This high-vacuum environment reduces the reaction between the metal and residual gases, preventing elemental oxidation and burn-off, and ensuring that the added trace metal additives are precisely retained in the oxygen-free copper.

[0019] Preferably, after the vacuum induction furnace is evacuated in step (2), it is kept for 1-2 hours, for example, 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours or 2 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] Preferably, the first temperature in step (2) is 800-900℃, for example, it can be 800℃, 825℃, 850℃, 865℃, 885℃ or 900℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] Preferably, after heating to the first temperature, the temperature is maintained for 0.5-1 hour, such as 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 0.9 hours, or 1 hour, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] Preferably, the second temperature in step (2) is 1190-1230℃, for example, it can be 1190℃, 1195℃, 1200℃, 1210℃, 1220℃ or 1230℃, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] In step (2) of this invention, the electrolytic copper base material in the crucible is first preheated, and then the electrolytic copper base material in the crucible is melted. This staged heating step is beneficial for degassing and removing volatile impurities. If the vacuum induction furnace is heated to the second temperature at one time to melt the electrolytic copper base material in the crucible, the oxygen content of the final oxygen-free copper for ceramic cladding will not meet the standard.

[0024] Preferably, in step (3), the electrolytic copper melt is kept at a constant temperature for 30-60 minutes before adding metal additives. For example, the time can be 30 minutes, 35 minutes, 40 minutes, 45 minutes, 55 minutes, or 60 minutes, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, the casting time in step (3) is 1-5 min, for example, it can be 1 min, 2 min, 3 min, 4 min, 4.5 min or 5 min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] As a preferred technical solution of the present invention, the vacuum melting method includes the following steps: (1) Place the electrolytic copper base material into the crucible of the vacuum induction furnace and place the metal additives into the feeding chamber of the vacuum induction furnace; the purity of the electrolytic copper base material is ≥6N; the metal additives include Ti, Co, Ni and Ag; (2) Evacuate the vacuum induction furnace to a vacuum degree ≤10 -3 After Pa, maintain for 1-2 hours, heat to the first temperature of 800-900℃ and maintain for 0.5-1 hours to preheat the electrolytic copper base material in the crucible; continue heating to the second temperature of 1190-1230℃ to melt the electrolytic copper base material in the crucible and obtain electrolytic copper melt. (3) After the electrolytic copper melt is kept at a constant temperature for 30-60 minutes, metal additives are added to it, and after alloying treatment, it is cast to obtain the oxygen-free copper for ceramic copper coating; the casting time is 1-5 minutes. The oxygen content of the oxygen-free copper used for ceramic copper cladding is <5ppm; the content of Ag in the oxygen-free copper used for ceramic copper cladding is 10-40ppm, the content of Ti is 10-20ppm, the content of Co is 10-20ppm, and the content of Ni is 5-15ppm.

[0027] Secondly, the present invention also provides oxygen-free copper for ceramic cladding prepared by vacuum melting method of oxygen-free copper for ceramic cladding as described in the first aspect.

[0028] This invention uses a vacuum induction melting method to microalloy oxygen-free copper, resulting in fine grains after welding with ceramics at high temperatures, thus meeting the requirements for using copper-clad ceramics.

[0029] Compared with the prior art, the present invention has at least the following beneficial effects: The oxygen-free copper for ceramic cladding and its vacuum melting method provided by this invention are simple to operate. By performing micro-alloying through vacuum induction melting, oxygen-free copper with fine grains after welding with ceramics at high temperature is prepared, which meets the requirements for ceramic cladding and is suitable for widespread application. Detailed Implementation

[0030] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0031] The contents of Ag, Ti, Co and Ni in the oxygen-free copper obtained in the following examples and comparative examples were determined by glow discharge mass spectrometry.

[0032] Example 1 This embodiment provides a vacuum melting method for oxygen-free copper used in ceramic copper cladding, the vacuum melting method comprising the following steps: (1) The electrolytic copper base material is placed in the crucible of the vacuum induction furnace, and the metal additives are placed in the feeding chamber of the vacuum induction furnace; the purity of the electrolytic copper base material is 6.2N; the metal additives include Ti, Co, Ni and Ag; (2) Evacuate the vacuum induction furnace to a vacuum degree of 8×10. -4 After Pa, hold for 1.2 h, heat to the first temperature of 860℃ and hold for 0.7 h to preheat the electrolytic copper base material in the crucible; continue heating to the second temperature of 1200℃ to melt the electrolytic copper base material in the crucible and obtain electrolytic copper melt. (3) After the electrolytic copper melt is kept at a constant temperature for 50 minutes, metal additives are added to it, and after alloying treatment, it is cast to obtain the oxygen-free copper for ceramic copper coating; the casting time is 3 minutes.

[0033] The oxygen-free copper for ceramic cladding prepared in this embodiment has an oxygen content of 3 ppm, an Ag content of 30 ppm, a Ti content of 15 ppm, a Co content of 13 ppm, and a Ni content of 10 ppm.

[0034] Example 2 This embodiment provides a vacuum melting method for oxygen-free copper used in ceramic copper cladding, the vacuum melting method comprising the following steps: (1) The electrolytic copper base material is placed in the crucible of the vacuum induction furnace, and the metal additives are placed in the feeding chamber of the vacuum induction furnace; the purity of the electrolytic copper base material is 6N; the metal additives include Ti, Co, Ni and Ag; (2) Evacuate the vacuum induction furnace to a vacuum degree of 4×10 -4 After Pa, maintain for 1 hour, heat to the first temperature of 800℃ and maintain for 1 hour to preheat the electrolytic copper base material in the crucible; continue heating to the second temperature of 1190℃ to melt the electrolytic copper base material in the crucible and obtain electrolytic copper melt. (3) After the electrolytic copper melt is kept at a constant temperature for 60 minutes, metal additives are added to it, and after alloying treatment, it is cast to obtain the oxygen-free copper for ceramic copper coating; the casting time is 5 minutes.

[0035] The oxygen-free copper for ceramic cladding prepared in this embodiment has an oxygen content of 1 ppm, an Ag content of 10 ppm, a Ti content of 10 ppm, a Co content of 20 ppm, and a Ni content of 15 ppm.

[0036] Example 3 This embodiment provides a vacuum melting method for oxygen-free copper used in ceramic copper cladding, the vacuum melting method comprising the following steps: (1) The electrolytic copper base material is placed in the crucible of the vacuum induction furnace, and the metal additives are placed in the feeding chamber of the vacuum induction furnace; the purity of the electrolytic copper base material is 6.5N; the metal additives include Ti, Co, Ni and Ag; (2) The vacuum induction furnace is evacuated to a vacuum degree of 10. -3 After Pa, maintain for 2 hours, heat to the first temperature of 900℃ and maintain for 0.5 hours to preheat the electrolytic copper base material in the crucible; continue heating to the second temperature of 1230℃ to melt the electrolytic copper base material in the crucible and obtain electrolytic copper melt. (3) After the electrolytic copper melt is kept at a constant temperature for 30 minutes, metal additives are added to it, and after alloying treatment, it is cast to obtain the oxygen-free copper for ceramic copper coating; the casting time is 1 minute.

[0037] The oxygen-free copper for ceramic cladding prepared in this embodiment has an oxygen content of 4 ppm, an Ag content of 40 ppm, a Ti content of 20 ppm, a Co content of 10 ppm, and a Ni content of 5 ppm.

[0038] Based on Examples 1-3, the vacuum melting method for oxygen-free copper for ceramic cladding provided by the present invention uses vacuum induction melting to microalloy the copper, resulting in oxygen-free copper with grain size below 100μm after welding with ceramic at high temperature, which meets the requirements for ceramic cladding.

[0039] Example 4 This embodiment provides a vacuum melting method for oxygen-free copper used in ceramic copper cladding. The vacuum melting method, except for step (2) where the vacuum induction furnace is evacuated to a vacuum degree of 10... -2Except for Pa, everything else is the same as in Example 1.

[0040] In this embodiment, due to the high vacuum level of the vacuum induction furnace, harmful gases such as hydrogen, nitrogen, and oxygen cannot be fully removed, resulting in oxygen content of the oxygen-free copper for ceramic cladding that does not meet the usage requirements.

[0041] Example 5 This embodiment provides a vacuum melting method for oxygen-free copper for ceramic copper cladding. Except for step (3), in which the content of Ag added to the electrolytic copper melt is 50 ppm, the vacuum melting method is the same as that in Example 1.

[0042] In this embodiment, the addition of a large amount of Ag will reduce the purity of the oxygen-free copper used for ceramic cladding, which will not meet the requirements for subsequent use.

[0043] Example 6 This embodiment provides a vacuum melting method for oxygen-free copper for ceramic copper cladding. Except for step (3), in which the content of Co added to the electrolytic copper melt is 5 ppm, the vacuum melting method is the same as that in embodiment 1.

[0044] In this embodiment, the addition of less Co results in a lower Co content in the final oxygen-free copper used for ceramic cladding, leading to a poorer grain refinement effect. As a result, the grains remain large even after welding with ceramics at high temperatures, affecting the quality of the ceramic cladding material.

[0045] Comparative Example 1 This comparative example provides a vacuum melting method for oxygen-free copper for ceramic copper cladding. Except for steps (1) and (3) where no metal additives are added, the vacuum melting method is the same as in Example 1.

[0046] Because no metal additives were added in this comparative example, the oxygen-free copper prepared in this example will grow rapidly in grain size after being welded to ceramics at high temperature, reaching hundreds of micrometers or even millimeters, which will seriously affect its subsequent use.

[0047] Comparative Example 2 This comparative example provides a vacuum melting method for oxygen-free copper for ceramic copper cladding. Except for heating the electrolytic copper base material in the crucible in step (2) to 1200°C to obtain electrolytic copper melt, the vacuum melting method is the same as in Example 1.

[0048] In this comparative example, the oxygen content of the final oxygen-free copper for ceramic cladding cannot meet the standard because the vacuum induction furnace is heated to the second temperature in one go, causing the electrolytic copper base material in the crucible to melt.

[0049] Comparative Example 3 This comparative example provides a vacuum melting method for oxygen-free copper for ceramic copper cladding. The vacuum melting method is the same as in Example 1, except that the metal additives in steps (1) and (3) do not include Ti.

[0050] Comparative Example 4 This comparative example provides a vacuum melting method for oxygen-free copper for ceramic copper cladding. The vacuum melting method is the same as in Example 1, except that the metal additives in steps (1) and (3) do not include Co.

[0051] Comparative Example 5 This comparative example provides a vacuum melting method for oxygen-free copper for ceramic copper cladding. The vacuum melting method is the same as in Example 1, except that the metal additives in steps (1) and (3) do not include Ni.

[0052] Comparative Example 6 This comparative example provides a vacuum melting method for oxygen-free copper for ceramic copper cladding. The vacuum melting method is the same as in Example 1, except that the metal additives in steps (1) and (3) do not include Ag.

[0053] Comparative Examples 3-6 show that the lack of one of the metals Ti, Co, Ni and Ag in the metal additives leads to poor grain refinement. As a result, the oxygen-free copper used for ceramic cladding still has a large grain size after being welded to the ceramic at high temperature.

[0054] It should be noted that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A vacuum melting method for oxygen-free copper used in ceramic copper cladding, characterized in that, The vacuum melting method includes the following steps: (1) Place the electrolytic copper base material into the crucible of the vacuum induction furnace and place the metal additives into the charging chamber of the vacuum induction furnace; the metal additives include Ti, Co, Ni and Ag; (2) After the vacuum induction furnace is evacuated, it is heated to the first temperature to preheat the electrolytic copper base material in the crucible; then it is heated to the second temperature to melt the electrolytic copper base material in the crucible to obtain electrolytic copper melt. (3) Add metal additives to the electrolytic copper melt, perform alloying treatment, and then cast to obtain the oxygen-free copper for ceramic copper coating.

2. The vacuum melting method according to claim 1, characterized in that, The oxygen content of the oxygen-free copper used for ceramic copper cladding is <5ppm; Preferably, the oxygen-free copper used for ceramic cladding contains 10-40 ppm Ag, 10-20 ppm Ti, 10-20 ppm Co, and 5-15 ppm Ni.

3. The vacuum melting method according to claim 1 or 2, characterized in that, The purity of the electrolytic copper substrate in step (1) is ≥6N.

4. The vacuum melting method according to any one of claims 1-3, characterized in that, Step (2) involves evacuating the vacuum induction furnace to a vacuum level ≤10. -3 Pa.

5. The vacuum melting method according to any one of claims 1-4, characterized in that, After the vacuum induction furnace in step (2) is evacuated, it is kept for 1-2 hours.

6. The vacuum melting method according to any one of claims 1-5, characterized in that, Step (2) The first temperature is 800-900℃; Preferably, the temperature is maintained at the first temperature for 0.5-1 hour.

7. The vacuum melting method according to any one of claims 1-6, characterized in that, Step (2) The second temperature is 1190-1230℃.

8. The vacuum melting method according to any one of claims 1-7, characterized in that, In step (3), the electrolytic copper melt is kept at a constant temperature for 30-60 minutes before adding metal additives.

9. The vacuum melting method according to any one of claims 1-8, characterized in that, The casting time in step (3) is 1-5 minutes.

10. Oxygen-free copper for ceramic cladding prepared by vacuum melting method according to any one of claims 1-9.