A manufacturing process for a high-reliability copper optical module

Abstract

This invention discloses a manufacturing process for a high-reliability copper optical module, belonging to the field of optical module manufacturing technology. The process includes the following steps: material forming, using oxygen-free copper with a purity ≥99.99% as the substrate, pressing copper powder into shape through powder metallurgy, and sintering in a reducing atmosphere to form a dense copper component with an internal porosity ≤0.5%; machining: milling and surface polishing the sintered copper component; welding and assembly: welding the optical components and circuit board to the inner cavity of the copper shell. During welding, an inflation port and an exhaust port are pre-reserved on the side of the copper shell, and one-way inlet valves and one-way outlet valves are installed in the inflation port and exhaust port respectively. Finally, the inner cavity of the copper shell is sealed, filled with helium, coated, welded shut, and airtightness tested. This invention, by coating a dense layer on the outside of the copper shell, can prevent helium leakage during copper shell welding, ensuring the accuracy of subsequent helium testing.

Description

Technical Field

[0001] This invention belongs to the field of optical module manufacturing technology, specifically relating to a manufacturing process for a high-reliability copper optical module. Background Technology

[0002] Optical modules, as core components of modern optical communication systems, are widely used in data centers, 5G networks, fiber-to-the-home (FTTH), and long-distance backbone transmission. Their core function is to achieve efficient conversion and transmission of photoelectric signals. With data transmission rates evolving towards 400G, 800G, and even 1.6T, high-density packaging and long-term reliability of optical modules have become key technological challenges. Among these, hermeticity is one of the core indicators affecting the reliability of optical modules, especially for high-end applications such as high-speed coherent modules and aerospace optical communications, where the helium mass spectrometry leak detection rate must be strictly controlled to ≤1×10⁻⁶. -9 Pa·m 3 To ensure stable operation of the device under harsh environments such as high temperature, high humidity, and mechanical vibration, the speed of the copper casing is below a certain value. Currently, copper is often chosen as the substrate for optical module housings due to its excellent thermal conductivity and low cost. However, ensuring the airtightness of copper housings during manufacturing presents a significant challenge. Specifically, before helium mass spectrometry leak detection, the optical module cavity needs to be filled with helium as a tracer gas. However, subsequent sealing and welding of the copper housings can easily lead to helium leakage within the cavity, thus affecting the subsequent leak detection results. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a manufacturing process for a high-reliability copper optical module, which can solve the above-mentioned technical problems.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] This invention discloses a manufacturing process for a high-reliability copper optical module, comprising the following steps:

[0006] For material forming, oxygen-free copper with a purity of ≥99.99% is selected as the base material. Copper powder is pressed into shape through powder metallurgy process and sintered in a reducing atmosphere to form a dense copper component with an internal porosity of ≤0.5%.

[0007] Machining: The sintered copper components are milled and polished to ensure that the dimensional tolerance is within ±0.01mm and the surface roughness Ra≤0.1μm;

[0008] Welding assembly: Weld the optical components and circuit boards into the inner cavity of the copper shell. During welding, make an air inlet and an air outlet on the side of the copper shell. Install a one-way air inlet valve and a one-way air outlet valve in the air inlet and the air outlet respectively. Finally, seal the inner cavity of the copper shell.

[0009] Helium filling: In a closed environment, connect the helium cylinder to the one-way inlet valve and continuously flush the optical module cavity with helium to replace the internal air; then temporarily close the one-way outlet valve and continue filling until the pressure inside the optical module cavity meets the requirements.

[0010] Coating: A dense layer is plated on the outer side of the main body of the copper shell;

[0011] Welding and sealing: Weld the air inlet and outlet to seal the inner cavity of the copper shell;

[0012] Air tightness test: The assembled optical module is placed in a helium mass spectrometer leak detector to test its leakage rate.

[0013] Furthermore, after the dense layer is plated, a shrinkage layer is plated on the outside of the dense layer. The shrinkage layer is wrapped around the outside of the dense layer in a ring. The coefficient of thermal expansion of the shrinkage layer is higher than that of copper and the dense layer.

[0014] Furthermore, the material of the shrinkage layer is zinc. Before the zinc layer is plated, the entire copper shell is heated to 150-200°C, kept at that temperature, and then the zinc layer is plated. After that, it is rapidly cooled to room temperature. After the entire shell is kept in a cooled state for a specified time, the copper shell is welded to seal the cavity. Finally, the shrinkage layer is peeled off from the outside of the dense layer.

[0015] Furthermore, when reserving the air inlet and outlet, copper pipes are welded to the outside of the air inlet and outlet, and the copper pipes protrude towards the outside of the copper shell; multiple sets of shrinkage layers are evenly spaced along the length of the copper shell, and the copper pipes are located in the interval between two adjacent sets of shrinkage layers.

[0016] Furthermore, in the coating process, the copper surface is first pickled and ultrasonically cleaned to remove the oxide layer and organic matter. Then, a nano-alumina layer is added between the copper and nickel before coating. After coating, the surface is vacuum annealed at 200-250°C for 1 hour to promote atomic interdiffusion and eliminate interfacial micropores.

[0017] Furthermore, vacuum annealing is carried out in a sealed chamber filled with hydrogen or nitrogen. The low-temperature annealing method can increase the surface smoothness of the coating, promote atomic rearrangement of the coating, eliminate micro-pores on the coating surface, and make it easier to peel off the shrinkage layer in the future.

[0018] Furthermore, the manufacturing process also includes environmental reliability testing, which follows the airtightness testing. Specifically, the assembled optical module is subjected to temperature, humidity, and mechanical vibration tests in sequence to ensure that the optical module performance meets the requirements.

[0019] The beneficial effects of this invention are as follows:

[0020] The present invention discloses a manufacturing process for a high-reliability copper optical module. By pre-filling the copper shell with helium, the helium is evenly distributed, resulting in high detection sensitivity. This process is particularly suitable for complex cavity structures and can achieve high detection accuracy.

[0021] Helium is the smallest molecule besides hydrogen and can penetrate the lattice gaps or microscopic defects of most metals. Therefore, even if the macroscopic seal is intact, helium can still escape through lattice penetration or instantaneous thermal defects. This invention coats a dense layer on the outside of the copper shell. Because the lattice on the surface of the nickel layer is dense, it can prevent helium leakage and ensure the accuracy of subsequent helium detection.

[0022] Other advantages, objectives, and features of the invention will be set forth in the following description and will be apparent to those skilled in the art in some respects, or may be learned by practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0023] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration:

[0024] Figure 1 This is a flowchart of the manufacturing process of the present invention;

[0025] Figure 2 This is a schematic diagram of the structure of the copper shell of the present invention.

[0026] The following are the markings in the attached diagram: 1. Copper shell, 2. Dense layer, 3. Shrinkage layer, 4. Inflation port, 5. Exhaust port, 6. Copper pipe. Detailed Implementation

[0027] Example 1, as Figure 1 and 2 As shown, the present invention discloses a manufacturing process for a high-reliability copper optical module, comprising the following steps:

[0028] For material forming, oxygen-free copper with a purity ≥99.99% is selected as the base material. Copper powder is pressed into shape using powder metallurgy, significantly reducing the internal porosity of the material and fundamentally minimizing helium permeation paths, thus improving its airtightness. The material is then sintered in a reducing atmosphere to form a dense copper component with an internal porosity ≤0.5%.

[0029] Specifically, during the copper powder pressing process, the copper powder particle size is 1-10μm, the pressing pressure is 400-800MPa, the sintering temperature is 850-950℃, the holding time is 2-4 hours, and the oxygen content in the hydrogen atmosphere is ≤10ppm.

[0030] Machining: The sintered copper components are milled and polished to control the dimensional tolerance within ±0.01mm and the surface roughness Ra≤0.1μm. This ensures the flatness of the welding surface, reduces the concentration of thermal stress during laser welding, and avoids the generation of microcracks.

[0031] Welding Assembly: The optical components and circuit boards are welded to the inner cavity of the copper housing 1. During welding, an inflation port 4 and an exhaust port 5 are pre-drilled on the side of the copper housing 1, and one-way inlet valves and one-way outlet valves are installed in the inflation port 4 and exhaust port 5 respectively. Finally, the inner cavity of the copper housing 1 is sealed to facilitate the subsequent filling of helium into the inner cavity. Laser welding is used during welding, with a coaxial shielding gas flow rate of 10-20 L / min and a welding speed of 2-5 mm / s.

[0032] Helium filling: In a closed environment, connect the helium cylinder to the one-way inlet valve and continuously flush the optical module cavity with helium to replace the internal air; then temporarily close the one-way outlet valve and continue filling until the pressure inside the optical module cavity reaches twice the atmospheric pressure.

[0033] Coating: A dense layer 2 is plated on the outer side of the main body of the copper shell 1. The dense layer 2 is a nickel layer with a thickness of 2-4 μm, which is used to enhance corrosion resistance. Helium is the smallest molecule except hydrogen and can penetrate the lattice gaps or micro defects of most metals. Therefore, even if the macroscopic seal is intact, helium can still escape through lattice penetration or instantaneous thermal defects. Due to the dense lattice on the surface of the nickel layer, helium leakage can be prevented.

[0034] The present invention can prevent helium leakage during the welding of the copper shell 1 by plating a dense layer 2 on the outside of the copper shell, thus ensuring the accuracy of subsequent helium detection.

[0035] Welding and sealing: Weld the filling port 4 and the outlet 5 to seal the inner cavity of the copper shell 1, ensuring that the leakage channels of helium are completely blocked.

[0036] Air tightness test: The assembled optical module is placed in a helium mass spectrometer leak detector, and its leakage rate is tested to be ≤1×10⁻⁶. - 9 Pa·m 3 / s.

[0037] In another embodiment, the dense layer 2 has two layers, including a nickel layer and a gold layer. First, the nickel layer is plated on the outside of the copper shell 1, and then the gold layer is plated on the outside of the nickel layer. The two layers work together to achieve both barrier and corrosion resistance, resulting in the best helium barrier effect. The interface can be sealed by key welding.

[0038] Example 2 differs from Example 1 in that, in this embodiment of the invention, after the dense layer 2 is plated, a shrinkage layer 3 is plated on the outside of the dense layer 2. The shrinkage layer 3 is circumferentially wrapped around the outside of the dense layer 2, and its coefficient of thermal expansion is higher than that of copper and the dense layer 2. After shrinkage, the shrinkage layer 3 can apply pressure to the outside of the plating, thereby promoting the interdiffusion of copper and nickel atoms, reducing interface defects, enhancing bonding strength, and blocking helium permeation. Using a planar pressure method, the external pressure can compress the crystal lattice, shorten the interatomic spacing, and make it easier for copper / nickel atoms to migrate across the interface. Through the compression effect of the outermost shrinkage layer 3, the pressure is applied more uniformly and will not cause deformation of the copper shell 1 or the plating.

[0039] Meanwhile, if the electroplating or electroless plating process is poor, micropores, cracks, or unbonded areas may exist between the plating layer and the copper substrate. The interfacial gap between the plating layer and the copper substrate may become a potential path for helium gas to escape. Therefore, by setting an annular shrinkage layer 3 on the outside of the plating layer, interfacial micropores can be eliminated. After welding, local scanning of the plating edge by helium mass spectrometry is used to specifically detect leaks and ensure that the interfacial leakage rate is <10-10 Pa·m 3 / s.

[0040] Comparative Example 1: After filling the inner cavity of the copper shell 1 with helium, Comparative Example 1 did not seal the filling / exit port 5, and then directly conducted an airtightness test.

[0041] Comparative Example 2 differs from Comparative Example 1 in that after Comparative Example 2 is filled with helium, the filling / exit port 5 is directly welded closed, but without coating, and the welding temperature is 1200-1500℃.

[0042] The table below records the leakage of helium gas inside copper casing 1 at an initial pressure of 200 kPa after different time intervals, with the unit being Pa·m. 3 / s, with an error controlled within 0.2×10 -9 about.

[0043]

[0044]

[0045] As a further improvement of Embodiment 2 of the present invention, the material of the shrinkage layer 3 is zinc. Before plating the zinc layer, the entire copper housing 1 is heated to 150-200°C, causing it to expand. After holding at this temperature, the zinc layer is plating, followed by rapid cooling to room temperature. At this time, the zinc layer rapidly shrinks inward, which can act on the outer plating layer. After keeping the entire structure in a cooled state for a specified time, the copper housing 1 is welded and sealed. Finally, the shrinkage layer 3 is peeled off from the outside of the dense layer 2. Since zinc acts as an anode in a humid environment, accelerating its own corrosion and potentially causing galvanic corrosion, leading to the erosion of the nickel or copper substrate, it is necessary to peel off the zinc layer to prevent it from affecting the optical module.

[0046] In this embodiment, when reserving the air outlet 5 and the air release port 5, a copper tube 6 is welded to the outside of the air inlet 4 and the air release port 5, with the copper tube 6 protruding outwards towards the copper shell 1; multiple sets of shrinkage layers 3 are evenly spaced along the length of the copper shell 1, and the copper tube 6 is located in the interval between two adjacent sets of shrinkage layers 3. By reserving the copper tube 6, not only can air inflation and deflation be conveniently facilitated, but the welded area can also be shielded to a certain extent when the air outlet 5 and the air release port 5 are welded closed, preventing high temperature from affecting the zinc layer or plating.

[0047] In this embodiment, during the coating process, the copper surface is first acid-washed and ultrasonically cleaned to remove the oxide layer and organic matter. Then, a nano-alumina layer is added between the copper and nickel layers before coating. After coating, vacuum annealing at 200–250°C for 1 hour promotes atomic rearrangement, eliminates micropores, reduces the bonding force between the zinc and nickel layers, and facilitates zinc layer peeling. Furthermore, annealing at the aforementioned temperature also promotes atomic interdiffusion between copper and nickel, eliminates interfacial micropores, and prevents helium leakage.

[0048] In this embodiment, vacuum annealing is carried out in a closed cavity filled with hydrogen or nitrogen. The low-temperature annealing method can increase the surface smoothness of the coating, promote the rearrangement of coating atoms, eliminate micro-pores on the coating surface, and make it easier to peel off the shrinkage layer 3 in the future.

[0049] In this embodiment, the manufacturing process also includes environmental reliability testing, which is conducted after the airtightness test. Specifically, the assembled optical module is subjected to temperature, humidity, and mechanical vibration tests in sequence. Specifically, the high temperature is 85°C, the high humidity is 85%RH for 1000 hours, the temperature cycle is -40°C to +85°C for 500 cycles, and the mechanical vibration is tested at 20G for 30 minutes on each axis to ensure that the performance degradation of the optical module is less than 5%.

[0050] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A manufacturing process for a high-reliability copper optical module, characterized in that: Includes the following steps: For material forming, oxygen-free copper with a purity of ≥99.99% is selected as the base material. Copper powder is pressed into shape through powder metallurgy process and sintered in a reducing atmosphere to form a dense copper component with an internal porosity of ≤0.5%. Machining: The sintered copper components are milled and polished to ensure that the dimensional tolerance is within ±0.01mm and the surface roughness Ra≤0.1μm; Welding assembly: Weld the optical components and circuit boards into the inner cavity of the copper shell. During welding, make an air inlet and an air outlet on the side of the copper shell. Install a one-way air inlet valve and a one-way air outlet valve in the air inlet and the air outlet respectively. Finally, seal the inner cavity of the copper shell. Helium filling: In a closed environment, connect the helium cylinder to the one-way inlet valve and continuously flush the optical module cavity with helium to replace the internal air; then temporarily close the one-way outlet valve and continue filling until the pressure inside the optical module cavity meets the requirements. Coating: A dense layer is plated on the outer side of the main body of the copper shell; Welding and sealing: Weld the air inlet and outlet to seal the inner cavity of the copper shell; Air tightness test: The assembled optical module is placed in a helium mass spectrometer leak detector to test its leakage rate; After the dense layer is plated, a shrinkage layer is then plated on the outside of the dense layer. The shrinkage layer is wrapped in a ring around the outside of the dense layer, and the coefficient of thermal expansion of the shrinkage layer is higher than that of copper and the dense layer. The shrinkage layer is made of zinc. Before plating the zinc layer, the entire copper shell is heated to 150~200℃, kept at that temperature, and then the zinc layer is plating. Afterward, it is rapidly cooled to room temperature, and the entire shell is kept in a cooling state for a specified time. Then, the copper shell is welded to seal the cavity, and finally, the shrinkage layer is peeled off from the outside of the dense layer. When reserving air inlets and outlets, copper pipes are welded to the outside of the air inlets and outlets, with the copper pipes protruding outwards from the copper shell; multiple sets of shrinkage layers are evenly spaced along the length of the copper shell, and the copper pipes are located in the interval between two adjacent sets of shrinkage layers.

2. The manufacturing process of a high-reliability copper optical module according to claim 1, characterized in that: In the coating process, the copper surface is first pickled and ultrasonically cleaned to remove the oxide layer and organic matter. Then, a nano-alumina layer is added between the copper and nickel before coating. After coating, the surface is vacuum annealed at 200~250℃ for 1 hour to promote atomic interdiffusion and eliminate interfacial micropores.

3. The manufacturing process of a high-reliability copper optical module according to claim 2, characterized in that: Vacuum annealing is performed in a closed chamber filled with hydrogen or nitrogen gas. This low-temperature annealing method can increase the smoothness of the coating surface.

4. The manufacturing process of a high-reliability copper optical module according to any one of claims 1-3, characterized in that: The manufacturing process also includes environmental reliability testing, which follows the airtightness testing. Specifically, the assembled optical module is subjected to temperature, humidity, and mechanical vibration tests in sequence to ensure that the optical module performance meets the requirements.

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