Manufacturing process of high-reliability copper optical module

Abstract

The invention discloses a manufacturing process of a high-reliability copper optical module, which belongs to the technical field of optical module manufacturing, and comprises the following steps: material forming: selecting oxygen-free copper with the purity of more than or equal to 99.99% as a base material, pressing and forming copper powder through a powder metallurgy process, and sintering in a reducing atmosphere to form a compact copper component with the internal porosity of less than or equal to 0.5%; machining is conducted, specifically, milling and surface polishing are conducted on the sintered copper component; and welding and assembling: welding the optical assembly and the circuit board in the inner cavity of the copper shell, reserving an inflation inlet and an air outlet in the side surface of the copper shell during welding, respectively installing a one-way air inlet valve and a one-way air outlet valve in the inflation inlet and the air outlet, and finally performing sealing, helium filling, film coating, welding and cavity sealing and air tightness detection on the inner cavity of the copper shell. The compact layer is plated on the outer side of the copper shell, so that the problem of helium leakage caused by welding of the copper shell can be prevented, and the accuracy of subsequent helium detection is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical module manufacturing, and particularly relates to a manufacturing process for a high-reliability copper optical module. Background Art

[0002] As a core device of modern optical communication systems, optical modules are widely used in fields such as data centers, 5G networks, fiber to the home, and long-distance backbone transmission. Their core function is to achieve efficient conversion and transmission of optical and electrical signals. With the evolution of data transmission rates towards 400G, 800G, and even 1.6T, the high-density packaging and long-term reliability of optical modules have become key technical challenges. Among them, airtightness 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 communication, the helium mass spectrometry leak rate needs to be strictly controlled at ≤1×10 -9 Pa·m 3 / s or less to ensure the stable operation of the device in harsh environments such as high temperature, high humidity, and mechanical vibration. Currently, due to its excellent thermal conductivity and low cost, copper is often selected as the base material for the optical module housing. However, the copper housing faces severe challenges in ensuring airtightness during the manufacturing process. Specifically, before helium mass spectrometry leak detection, helium gas needs to be filled into the optical module cavity as a tracer gas, but it is easy to cause helium gas leakage in the inner cavity during the subsequent closed welding between copper housings, thereby 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 technical problems.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] A manufacturing process for a high-reliability copper optical module disclosed by the present invention includes the following steps:

[0006] Material forming: Select oxygen-free copper with a purity ≥99.99% as the base material, press the copper powder into shape through powder metallurgy, and sinter it in a reducing atmosphere to form a dense copper component with an internal porosity ≤0.5%;

[0007] Machining: Milling and surface polishing are performed on the sintered copper component to control its dimensional tolerance within ±0.01mm and the surface roughness Ra ≤0.1μm;

[0008] Welding and assembly: Weld the optical components and the circuit board in the inner cavity of the copper housing. When welding, an air inlet and an air outlet are reserved on the side of the copper housing, and a one-way intake valve and a one-way exhaust valve are respectively installed in the air inlet and the air outlet. Finally, the inner cavity of the copper housing is sealed;

[0009] Helium filling: In a closed environment, connect the helium gas cylinder to the one-way intake valve, continuously flush the optical module cavity with helium to displace the internal air; then temporarily seal the one-way outlet valve and continue to fill with gas until the pressure in the optical module cavity meets the requirements;

[0010] Coating: Deposit a dense layer on the outer side of the main body of the copper housing;

[0011] Welding and sealing the cavity: Weld and seal the gas inlet and outlet to ensure the inner cavity of the copper housing is sealed;

[0012] Air tightness detection: Place the assembled optical module in a helium mass spectrometer leak detector to test its leak rate.

[0013] Furthermore, after depositing the dense layer, deposit a shrinkage layer on the outer side of the dense layer. The shrinkage layer is wound around the outer side of the dense layer in a ring shape, and the thermal expansion coefficient 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 depositing the zinc layer, heat the entire copper housing to 150 - 200 °C, keep it warm and then deposit the zinc layer. Subsequently, quickly cool it to room temperature. After maintaining the overall cooling state for a specified time, weld and seal the cavity of the copper housing, and finally peel off the shrinkage layer from the outer side of the dense layer.

[0015] Furthermore, when reserving the gas inlet and outlet, weld copper pipes on the outer sides of the gas inlet and outlet. The copper pipes protrude towards the outer side of the copper housing; multiple groups of shrinkage layers are arranged at equal intervals along the length direction of the copper housing, and the copper pipes are located within the intervals between adjacent groups of shrinkage layers.

[0016] Furthermore, in the coating step, first perform pickling and ultrasonic cleaning on the copper surface to remove the oxide layer and organic substances. Subsequently, add a nano-aluminum oxide layer between the copper and nickel and then perform the coating; after coating, perform vacuum annealing at 200 - 250 °C for 1 hour to promote atomic interdiffusion and eliminate interface micropores.

[0017] Furthermore, during vacuum annealing, it is carried out in a closed cavity filled with hydrogen or nitrogen. The method of low-temperature annealing can increase the surface smoothness of the coating, promote the rearrangement of coating atoms, eliminate microscopic pores on the coating surface, increase the surface smoothness of the coating, and facilitate the subsequent peeling off of the shrinkage layer.

[0018] Furthermore, the manufacturing process also includes environmental reliability testing. The environmental reliability testing is carried out after the air tightness testing. Specifically: subject the assembled optical module to temperature, humidity, and mechanical vibration tests in sequence to ensure that the performance of the optical module meets the requirements.

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

[0020] A manufacturing process for a highly reliable copper optical module disclosed in the present invention. Since helium gas is pre-filled into the copper housing, the helium gas is evenly distributed, the detection sensitivity is high, it is especially suitable for complex cavity structures, and relatively high detection accuracy can be achieved.

[0021] Helium is the smallest molecule except hydrogen and can penetrate the lattice gaps or microscopic defects of most metals. Therefore, even if the macroscopic seal is intact, helium gas will still escape through lattice penetration or transient thermal defects. In the present invention, a dense layer is plated on the outer side of the main body of the copper housing. Since the lattice on the surface of the nickel layer is dense, it can prevent helium gas leakage and ensure the accuracy during subsequent helium gas detection.

[0022] Other advantages, objectives and features of the present invention will be described in the subsequent specification, and to some extent, they are obvious to those skilled in the art, or those skilled in the art can obtain teachings from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] To make the objectives, technical solutions and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

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

[0025] Figure 2 It is a schematic structural diagram of the copper housing of the present invention.

[0026] The reference numerals in the drawings are as follows: copper housing 1, dense layer 2, shrinkage layer 3, gas inlet 4, gas outlet 5, copper tube 6. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] Example 1, as Figure 1 and 2 shown, a manufacturing process for a highly reliable copper optical module disclosed in the present invention includes the following steps:

[0028] Material forming: Select oxygen-free copper with a purity ≥ 99.99% as the base material, and press the copper powder into shape through powder metallurgy process, significantly reducing the porosity inside the material, fundamentally reducing the helium gas penetration path, and improving the basic airtightness performance. And sinter in a reducing atmosphere to form a dense copper component with an internal porosity ≤ 0.5%;

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

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

[0031] Welding and assembly: The optical components and the circuit board are welded inside the cavity of the copper housing 1. During welding, an air inlet 4 and an air outlet 5 are reserved on the side of the copper housing 1, and a one-way intake valve and a one-way exhaust valve are respectively installed in the air inlet 4 and the air outlet 5. Finally, the cavity of the copper housing 1 is sealed, which is convenient for filling helium into the cavity later. Laser welding is used during welding, with coaxial shielding gas, a flow rate of 10 - 20 L / min, and a welding speed of 2 - 5 mm / s.

[0032] Helium filling: In a closed environment, the helium gas cylinder is docked with the one-way intake valve, and the optical module cavity is continuously flushed with helium to displace the internal air; then the one-way exhaust valve is temporarily closed, and helium is continuously filled until the pressure in 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 housing 1. The dense layer 2 is made of 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 microscopic defects of most metals. Therefore, even if the macroscopic seal is intact, helium will still escape through lattice penetration or transient thermal defects. Since the lattice on the surface of the nickel layer is dense, it can prevent helium leakage.

[0034] The present invention can prevent the leakage problem of helium caused during the welding of the copper housing by plating a dense layer 2 on the outer side of the copper housing, ensuring the accuracy of subsequent helium detection.

[0035] Welding and sealing the cavity: The air inlet 4 and the air outlet 5 are welded and sealed to ensure the sealing of the cavity of the copper housing 1 and completely block the helium leakage channel.

[0036] Air tightness detection: The assembled optical module is placed in a helium mass spectrometer to test its leakage rate ≤ 1×10 - 9 Pa·m 3 / s.

[0037] In other embodiments, the dense layer 2 has two layers, including a nickel layer and a gold layer. First, the nickel layer is plated on the outer side of the copper housing 1, and then the gold layer is plated on the outer side of the nickel layer. Through the cooperation of the two layers, both barrier and corrosion resistance are considered, and the best helium blocking effect is achieved. Key welding and sealing are carried out at the interface.

[0038] Example 2. Different from Example 1, in this embodiment of the present invention, after the dense layer 2 is plated, a shrinkage layer 3 is plated on the outer side of the dense layer 2. The shrinkage layer 3 is wound around the outer side of the dense layer 2 in a ring shape, and the coefficient of thermal expansion of the shrinkage layer 3 is higher than that of copper and the dense layer 2. After the shrinkage layer 3 of the present invention shrinks, it can apply pressure to the outside of the coating, thereby promoting the interdiffusion of copper-nickel atoms, reducing interface defects, enhancing the bonding force, and blocking helium penetration. Using a planar pressure method, the external pressure can compress the lattice and shorten the atomic spacing, making it easier for copper / nickel atoms to migrate across the interface. Through the compression of the outermost shrinkage layer 3, the action of the pressure is more uniform and will not cause deformation of the copper shell 1 or the coating.

[0039] Meanwhile, if the electroplating or electroless plating process is not good, there may be micropores, cracks or unbonded areas between the coating and the copper substrate. The interface gap between the coating and the copper substrate may become a potential path for helium gas to escape. Therefore, by setting a ring-shaped shrinkage layer 3 on the outside of the coating, the interface micropores can be eliminated. After welding is completed, local helium mass spectrometry scanning is carried out on the edge of the coating to specifically detect leaks, ensuring that the interface leakage rate < 10-10 Pa·m 3 / s.

[0040] Comparative Example 1. In Comparative Example 1, after filling the inner cavity of the copper shell 1 with helium gas, the inflation / outlet port 5 was not closed, and then the airtightness test was directly carried out.

[0041] Comparative Example 2. The difference between Comparative Example 2 and Comparative Example 1 is that after filling with helium gas, the inflation / outlet port 5 was directly welded and sealed, but there was no coating, and the welding temperature was 1200 - 1500 °C.

[0042] The following table records the leakage situation of helium gas in the copper shell 1 after different time intervals under an initial pressure of 200 kPa, with the unit of Pa·m 3 / s, and the error is controlled within 0.2×10 -9 or so.

[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 to cause overall expansion. After heat preservation, the zinc layer is plated, and then it is rapidly cooled to room temperature. At this time, the zinc layer rapidly shrinks inward and can act on the outer plating layer. After maintaining the overall cooling state for a specified time, the copper housing 1 is welded and sealed, and finally the shrinkage layer 3 is peeled off from the outside of the dense layer 2. Since zinc will accelerate its own corrosion as an anode in a humid environment and may cause galvanic corrosion, resulting in 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 outlet 5, copper pipes 6 are welded on the outside of the air inlet 4 and the air outlet 5, and the copper pipes 6 protrude towards the outside of the copper housing 1; multiple groups of shrinkage layers 3 are arranged at equal intervals along the length direction of the copper housing 1, and the copper pipes 6 are located in the intervals between adjacent two groups of shrinkage layers 3. By reserving the copper pipes 6, it is not only convenient for inflation and deflation, but also can shield the welding part to a certain extent when welding and sealing the air outlet 5 and the air outlet 5, preventing high temperature from affecting the zinc layer or the plating layer.

[0047] In this embodiment, in the coating step, first, pickling and ultrasonic cleaning are performed on the copper surface to remove the oxide layer and organic substances. Then, a nano-aluminum oxide layer is added between the copper and the nickel before plating; after plating, vacuum annealing is performed at 200 - 250 °C for 1 hour to promote the rearrangement of coating atoms, eliminate microscopic pores, reduce the bonding force between the zinc layer and the nickel layer, and facilitate the peeling of the zinc layer. And annealing treatment at the above temperature can also promote the atomic interdiffusion between copper and nickel, eliminate the interface micropores, and prevent helium gas from overflowing.

[0048] In this embodiment, during vacuum annealing, it 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 layer, promote the rearrangement of coating atoms, eliminate the microscopic pores on the surface of the coating layer, increase the surface smoothness of the coating layer, and facilitate the subsequent peeling off of the shrinkage layer 3.

[0049] In this embodiment, the manufacturing process further includes environmental reliability testing, which is carried out after airtightness testing. Specifically: the assembled optical module is sequentially subjected to temperature, humidity, and mechanical vibration tests. Specifically, the high temperature is 85 °C, the high humidity is 85% RH, the time is 1000 hours, the temperature cycle is -40 °C to +85 °C, 500 times, and the mechanical vibration is 20G for 30 minutes for each axis to ensure that the performance attenuation of the optical module < 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 not to limit them. 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 in form and details 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: The following steps are involved: Material molding: oxygen-free copper with a purity of ≥99.99% is selected as the base material. The copper powder is pressed into shape through a powder metallurgy process and sintered in a reducing atmosphere to form a dense copper component with an internal porosity of ≤0.5%; Machining: Milling and surface polishing of sintered copper components to control the dimensional tolerance within ±0.01mm and the surface roughness Ra≤0.1μm; Welding assembly: Weld the optical components and circuit boards to the inner cavity of the copper shell. During welding, reserve an air inlet and an air outlet on the side of the copper shell, and 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 tank to the one-way air inlet valve, and continuously flush the optical module cavity with helium to replace the internal air; then temporarily close the one-way air outlet valve and continue to fill until the pressure in the optical module cavity meets the requirements; Coating: A dense layer is plated on the outside of the main body of the copper shell; Welding and sealing the cavity: weld and seal the air inlet and outlet to ensure the inner cavity of the copper shell is sealed; Air tightness test: Place the assembled optical module in a helium mass spectrometer leak detector to test its leakage rate.

2. The manufacturing process of a high reliability copper optical module according to claim 1, characterized in that: After the dense layer is plated, a shrinkage layer is plated on the outside of the dense layer. The shrinkage layer is annularly wound on the outside of the dense layer. The thermal expansion coefficient of the shrinkage layer is higher than that of copper and the dense layer.

3. The manufacturing process of a high reliability copper optical module according to claim 2, characterized in that: The shrinkage layer is made of zinc. Before the zinc layer is plated, the copper shell is heated to 150-200°C as a whole, and then the zinc layer is plated after insulation. It is then quickly cooled to room temperature. After the whole is kept in a cooling state for a specified time, the copper shell is welded and sealed, and finally the shrinkage layer is peeled off from the outside of the dense layer.

4. The manufacturing process of a high reliability copper optical module according to claim 3, characterized in that: When reserving the air inlet and outlet, a copper tube is welded on the outside of the inflation port and the air outlet, and the copper tube protrudes toward the outside of the copper shell; the shrinkage layer is evenly arranged in multiple groups along the length direction of the copper shell, and the copper tube is located in the interval between two adjacent groups of shrinkage layers.

5. The manufacturing process of a high reliability copper optical module according to claim 2, characterized in that: In the coating step, the copper surface is first pickled and ultrasonically cleaned to remove the oxide layer and organic matter, and then a nano-aluminum oxide layer is added between the copper and the nickel before coating. After coating, vacuum annealing is performed at 200-250°C for 1 hour to promote atomic interdiffusion and eliminate interface micropores.

6. The manufacturing process of a high reliability copper optical module according to claim 5, characterized in that: During vacuum annealing, which is carried out in a closed chamber filled with hydrogen or nitrogen, low-temperature annealing can increase the surface smoothness of the coating.

7. A manufacturing process for a high reliability copper optical module according to any one of claims 1 to 6, characterized in that: The manufacturing process also includes an environmental reliability test, which is located after the air tightness test. Specifically, the assembled optical module is subjected to temperature, humidity and mechanical vibration tests in sequence to ensure that the performance of the optical module meets the requirements.

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