A shell structure for a laser control module in a microwave photonics system and its fabrication method

Abstract

This invention discloses a shell structure and fabrication method for a laser control module in a microwave photonics system. The structure includes a ceramic component with a first metal frame and a second metal frame disposed on its upper and lower surfaces, forming a double-sided cavity structure for encapsulating multiple components. Several lead pads are arranged around the ceramic component, with a metal lead soldered onto each lead pad. Several metallized patterns are formed on each layer of the ceramic component's surface and interior. The metallized patterns on the surface of the ceramic component are connected to the metallized patterns inside the ceramic component through metal holes, forming multiple signal networks. Signal networks not connected to the lead pads are called island networks. Electroplated interconnects are distributed on the surface of the ceramic component, connecting the island networks to the lead pads for nickel-gold plating of the island networks. This invention effectively improves the integration of the circuit module and also improves electroplating efficiency, ensuring a high plating yield.

Description

Technical Field

[0001] This invention belongs to the field of microwave photonic system packaging, specifically relating to a shell structure of a laser control module for a microwave photonic system and its fabrication method. Background Technology

[0002] Microwave photonics technology, as an interdisciplinary field integrating microwave and photonics technologies, effectively overcomes the "electronic bottleneck problem" by leveraging the advantages of photonics, such as low loss, large bandwidth, light weight, anti-interference, and wavelength division multiplexing. Microwave photonics technology is a cutting-edge optoelectronic technology that realizes microwave signal processing in the optical domain, and it is widely used in broadband wireless access networks, satellite communications, and radar systems.

[0003] Currently, most functional modules in microwave photonic systems are packaged in metal, which makes it difficult for the entire system to realize its potential advantages in terms of overall performance, size, weight, power consumption, and cost.

[0004] With increasingly demanding performance requirements in applications such as satellite communication and radar, microwave photonic systems represent a future development trend. Ceramic shells based on high-temperature co-fired ceramic (HTCC) technology offer higher reliability, lower cost, and the ability to achieve higher integration. HTCC-based packaging technology will become an important direction for future development in the field of microwave photonic system packaging. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a shell structure for a laser control module of a microwave photonics system and its fabrication method. This solution can effectively improve the integration of the circuit module, improve electroplating efficiency, and ensure a high plating yield.

[0006] Technical Solution: The present invention discloses a housing structure for a laser control module of a microwave photonics system, comprising a ceramic component. A first metal frame is disposed on the upper surface of the ceramic component, and a second metal frame is disposed on its lower surface. The first and second metal frames form a double-sided cavity structure on the ceramic component, which is used to encapsulate multiple components. Several lead pads are arranged around the ceramic component, and a metal lead is soldered onto each lead pad. The ceramic component has multiple layers, with several metallized patterns disposed on each layer, both on the surface and inside. The metallized patterns on the surface of the ceramic component are connected to the metallized patterns inside the ceramic component through metal holes disposed inside the ceramic component, forming multiple signal networks. Signal networks not connected to the lead pads are called island networks. Electroplated interconnects are distributed on the surface of the ceramic component, connecting the island networks to the lead pads. The metal leads soldered to the lead pads are connected to the signal networks disposed on the housing, enabling nickel-gold plating of the island networks.

[0007] Furthermore, the surface of the electroplated connecting lines is covered with a ceramic slurry pattern.

[0008] Furthermore, the metal leads are connected by an outer frame to form a whole, the width of the metal leads is 1.0mm to 1.5mm, and the spacing between adjacent metal leads is 1.5mm to 2.0mm.

[0009] Furthermore, a first metal cover plate is provided on the top surface of the first metal frame, and a second metal cover plate is provided on the bottom surface of the second metal frame.

[0010] Furthermore, the metal lead wire is bent into a Z-shaped structure, and the height of the metal lead wire is the sum of the heights of the second metal frame and the second metal cover plate, with a height of 1.6mm to 1.65mm.

[0011] Furthermore, the second metal frame and the second metal cover are made of molybdenum-copper alloy, forming a downward heat dissipation channel.

[0012] Based on the same inventive concept, the present invention provides a method for fabricating a shell structure for a microwave photonic system laser control module, used to fabricate the aforementioned shell structure for the microwave photonic system laser control module, comprising:

[0013] Ceramic green porcelain strips with a thickness of 0.20mm to 0.35mm were selected as ceramic parts;

[0014] The process involves drilling, filling holes, printing metallized patterns, printing ceramic slurry patterns, stacking, laminating, green cutting, and sintering ceramic parts.

[0015] Nickel plating is applied to the metallized patterns on the surface of the sintered ceramic parts;

[0016] The nickel-plated ceramic parts, metal leads, first metal frame, second metal frame, and silver-copper solder are placed into a prefabricated graphite mold in sequence and assembled together by high-temperature brazing to form a shell preform. The metal pattern on the surface of the shell preform is then electroplated with a nickel layer and a gold layer.

[0017] Laser is used to cut the electroplated wires and trim the outer frame of the metal leads.

[0018] Furthermore, the method of using a laser to cut the electroplating lines includes:

[0019] A protective adhesive is sprayed onto the surface of the double-sided cavity structure of the outer shell;

[0020] Place the outer shell structure coated with protective adhesive into an oven to allow the protective adhesive to cure.

[0021] Based on the metal graphics on the ceramic part and the location of the electroplating lines that need to be cut, create a laser cutting file; place the entire shell structure on the worktable of the laser equipment, adjust the laser height, and make the laser spot focus fall on the inner cavity surface of the shell structure;

[0022] The outer contour of the shell structure is aligned, and laser cutting is performed according to the processing documents;

[0023] After laser cutting is completed, the protective adhesive is removed.

[0024] Furthermore, the pre-assembled shell, which is assembled together by high-temperature brazing, includes:

[0025] Brazing is performed using framed metal leads, which, together with the electroplated connections on the ceramic components, connects all networks. Nickel and gold layers are then electroplated by binding the metal leads together.

[0026] Furthermore, the nickel layer has a thickness of 1.3-8.9 μm, and the gold layer has a thickness of 1.3-5.7 μm.

[0027] Beneficial effects: Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0028] This invention utilizes electroplated interconnects to connect the metallized pattern on the upper surface of a ceramic component to lead pads, enabling the islanded network and lead pads to conduct electricity, thus achieving nickel-gold plating of the islanded network.

[0029] The present invention uses framed metal leads during brazing to connect all metal leads into a whole, which facilitates electroplating. After plating, the outer frame is cut off. Combined with the method of laying electroplating lines, the electroplating qualification rate of the shell is effectively improved.

[0030] This invention utilizes a molybdenum-copper alloy for the metal frame and cover plate beneath the ceramic component, thereby enabling the circuit module to have excellent heat dissipation capabilities and improving the module's reliability.

[0031] This invention forms a double-sided cavity by welding a metal frame to the upper and lower surfaces of a ceramic component, which can effectively improve the integration of the circuit module, achieve miniaturization and weight reduction of the laser control module, and is beneficial to the integration of microwave photonic systems. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the housing structure of a laser control module for a microwave photonic system disclosed in an embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of the outer shell structure disclosed in an embodiment of the present invention with the cover plate removed from another perspective.

[0034] Figure 3This is a schematic diagram of the outer shell surface pattern disclosed in an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the protective adhesive sprayed onto the outer shell according to an embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram of the bent state of the metal lead wire disclosed in an embodiment of the present invention;

[0037] Figure 6 The diagram shows the heat dissipation simulation results disclosed in the embodiments of the present invention. Detailed Implementation

[0038] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0039] Example 1

[0040] like Figures 1 to 5 As shown, the outer shell structure of the microwave photonics system laser control module of the present invention includes a first metal cover plate 1, a first metal frame 2, a ceramic part 3, a metal lead wire 4, a second metal frame 5, a second metal cover plate 6, an electroplating connection line 7, a ceramic slurry pattern 8, a laser-cut line pattern 9, a protective adhesive 10, and a lead wire pad 11.

[0041] like Figure 1-3 As shown, a first metal frame 2 is disposed on the upper surface of the ceramic component 3, and a second metal frame 5 is disposed on its lower surface. The first metal frame 2 and the second metal frame 5 form a double-sided cavity structure on the ceramic component 3, which is used to encapsulate multiple components. Several lead pads 11 are arranged around the ceramic component 3, and a metal lead 4 is soldered onto each lead pad 11. In this embodiment, 20 lead pads 11 are arranged around the ceramic component 3. A first metal cover plate 1 is disposed on the top surface of the first metal frame 2, and a second metal cover plate 6 is disposed on the bottom surface of the second metal frame 5. In this embodiment, after chip mounting, a gas-tight cap is formed by parallel seam welding or fusion sealing, fixing the first metal cover plate 1 to the top surface of the first metal frame 2 and the second metal cover plate 6 to the bottom surface of the second metal frame 5. This shell structure uses parallel seam welding and fusion sealing processes for capping and has gas tightness, with a helium leak detection rate ≤1×10⁻⁶. -3 Pa·cm 3 / s.

[0042] In this embodiment, the ceramic component 3 is located between the first metal frame 2 and the second metal frame 5, and is connected by silver-copper solder. The main material of the ceramic component 3 is black alumina ceramic, with a bending strength ≥350 MPa.

[0043] In this embodiment, the metal lead 4, the first metal cover 1, and the first metal frame 2 are made of 4J42 iron-nickel alloy or 4J29 iron-nickel-cobalt alloy. The second metal frame 5 and the second metal cover 6 are made of molybdenum-copper alloy. Compared with the iron-nickel alloy material of the traditional shell, a downward heat dissipation channel is formed below the ceramic part 3, which can achieve better and more effective heat dissipation. The thermal conductivity of molybdenum-copper alloy is 190 W / (m·K). The height of the second metal frame 5 is 1.3 mm, and the thickness of the second metal cover 6 is 0.3 mm.

[0044] like Figure 5 As shown, the metal leads 4 are connected by an outer frame to form a whole. The width of the metal leads 4 is 1.0mm to 1.5mm, and the spacing between adjacent metal leads 4 is 1.5mm to 2.0mm. In this embodiment, the width of the metal leads 4 is 1.0mm, and the spacing between adjacent metal leads 4 is 2.0mm. The metal leads 4 are bent into a Z-shaped structure, and the height of the metal leads 4 is the sum of the heights of the second metal frame 5 and the second metal cover plate 6. In this embodiment, the height of the metal leads 4 is 1.6mm, enabling surface mounting of the control module.

[0045] In this embodiment, the ceramic component is a high-temperature co-fired multilayer ceramic (HTCC) flat plate structure. The ceramic component 3 has multiple layers, and several metallized patterns are formed on each layer, both on the surface and inside the ceramic component 3. The metallized patterns on the surface of the ceramic component 3 are connected to the metallized patterns inside the ceramic component 3 through metal holes, forming multiple signal networks. Among them, the signal networks that are not connected to the lead pads 11 are called island networks, and the metallized patterns in different layers are connected through metal holes.

[0046] In this embodiment, the metallized pattern and the metal hole are made of tungsten metal. For example... Figure 3 As shown, electroplated interconnects 7 are arranged on the surface of the ceramic part 3, connecting the islanded network and the lead pads 11. In this embodiment, the surface of the electroplated interconnects 7 is covered with a ceramic paste pattern 8. During electroplating, the electroplating fixture is connected to the metal lead 4, and the network on the outer casing that is connected to the metal lead 4 can be electroplated with nickel-gold. The islanded network is not connected to the metal lead 4, but is connected through the electroplated interconnects 7 to facilitate electroplating. In this solution, the islanded network is connected to those networks that are connected to the metal lead 4 through the electroplated interconnects 7. Except for the islanded network, other metallized patterns are connected to the lead pads 11 through internal wiring and holes.

[0047] The technical solution of this invention is based on a high-temperature co-fired ceramic process, which processes a ceramic component 3 with complex internal wiring. A double-sided cavity is formed using an iron-nickel alloy and a molybdenum-copper alloy as a brazing sealing frame, used to encapsulate multiple analog chips, digital chips, power chips, and other components. A surface-mount housing is formed by bending leads on all four sides. The double-sided cavity allows for higher integration within the same size. The molybdenum-copper sealing frame and cover plate on the underside of the ceramic component form a downward heat dissipation channel, providing excellent heat dissipation capabilities. The bent leads ensure good board-level soldering reliability within this housing size. Electroplated interconnects on the ceramic component enable nickel-gold plating of islanded networks, ensuring a high plating yield.

[0048] Example 2

[0049] The present invention discloses a method for fabricating a housing structure for a laser control module of a microwave photonic system. This method, used to fabricate the housing structure of the laser control module of the microwave photonic system described in Example 1, includes the following steps:

[0050] S1. Select a ceramic green porcelain strip with a thickness of 0.20mm to 0.35mm as ceramic part 3.

[0051] In this embodiment, a black alumina green ceramic strip with a thickness of 0.24 mm is selected for later use.

[0052] S2. Drilling, filling, printing metallized patterns, printing ceramic slurry patterns on ceramic parts 3, stacking, laminating, green cutting, and sintering.

[0053] Among them, the printed metallized pattern includes printed electroplating lines 7.

[0054] S3. Nickel plating is performed on the metallized pattern on the surface of the sintered ceramic part 3.

[0055] S4. The nickel-plated ceramic part 3, metal lead wire 4, first metal frame 2, second metal frame 5, and silver-copper solder are placed into a prefabricated graphite mold in sequence and assembled together by high-temperature brazing to form a shell pre-product. The metal pattern on the surface of the shell pre-product is electroplated with nickel and gold layers.

[0056] After being subjected to a high temperature of 780±5℃, and under the protection of nitrogen or hydrogen atmosphere, they are brazed together to form a pre-made shell.

[0057] The components are assembled together by high-temperature brazing to form a pre-made shell, including: using framed metal leads 4 for brazing, cooperating with electroplated connecting lines 7 on ceramic parts 3 to connect all networks, and electroplating nickel and gold layers by binding wires on the metal leads 4.

[0058] In this step, the nickel layer thickness is 1.3-8.9 μm and the gold layer thickness is 1.3-5.7 μm.

[0059] S5. Use a laser to cut the electroplating connection 7 and trim the outer frame of the metal lead 4.

[0060] In this embodiment, laser is used to cut the electroplating connection 7, including:

[0061] S5.1 Apply a layer of protective adhesive 1 to the surface of the double-sided cavity structure of the outer shell, such as... Figure 4 As shown.

[0062] In this embodiment, protective adhesive is sprayed onto the upper and lower inner cavities of the gold-plated shell and the side walls of the metal frame.

[0063] S5.2 Place the outer shell structure coated with protective adhesive 10 into an oven to allow the protective adhesive to cure.

[0064] S5.3. Based on the metal pattern on the ceramic part 3 and the position of the electroplating line to be cut, make the laser cutting pattern 9;

[0065] S5.4 Place the entire outer shell structure on the worktable of the laser equipment and adjust the laser height so that the laser spot focus falls on the inner cavity surface of the outer shell structure;

[0066] S5.5 Align the outer contour of the shell structure and perform laser cutting according to laser cutting pattern 9.

[0067] After laser cutting is completed, remove the protective adhesive 10.

[0068] Compared to traditional double-sided cavity shells, this invention uses a metal frame and metal cover made of molybdenum-copper material, which can achieve better heat dissipation. The temperature cloud diagram of chip heat dissipation is shown in the figure. Figure 6 As shown.

Claims

1. A housing structure for a laser control module in a microwave photonics system, characterized in that: The ceramic part (3) includes a first metal frame (2) on its upper surface and a second metal frame (5) on its lower surface. A double-sided cavity structure is formed on the ceramic part (3) by setting the first metal frame (2) and the second metal frame (5). The double-sided cavity structure is used to encapsulate multiple components. The ceramic part (3) has several lead pads (11) arranged around it, and a metal lead (4) is soldered on each lead pad (11). The ceramic part (3) has multiple layers, and several metallized patterns are provided on the surface and inside each layer of the ceramic part (3); The metallized pattern on the surface of the ceramic part (3) is connected to the metallized pattern inside the ceramic part (3) through metal holes provided inside the ceramic part (3) to form multiple signal networks; among them, the signal network that is not connected to the lead pad (11) is called an island network. The ceramic part (3) has electroplated connecting lines (7) on its surface. The island network and the lead pad (11) are connected through the electroplated connecting lines (7). The metal lead (4) soldered on the lead pad (11) is connected to the signal network set on the housing, which is used to realize the nickel-gold plating of the island network. The surface of the electroplating line (7) is covered with a ceramic slurry pattern (8); The first metal frame (2) is provided with a first metal cover plate (1) on its top surface, and the second metal frame (5) is provided with a second metal cover plate (6) on its bottom surface; the first metal frame (2) and the first metal cover plate (1) are made of 4J42 iron-nickel alloy or 4J29 iron-nickel-cobalt alloy. The second metal frame (5) and the second metal cover plate (6) are made of molybdenum-copper alloy, forming a downward heat dissipation channel.

2. The housing structure of the laser control module of the microwave photonic system according to claim 1, characterized in that: The metal leads (4) are connected by an outer frame to form a whole. The width of the metal leads (4) is 1.0mm to 1.5mm, and the spacing between adjacent metal leads (4) is 1.5mm to 2.0mm.

3. The housing structure of the laser control module of the microwave photonics system according to claim 1, characterized in that: The metal lead wire (4) is bent into a Z-shaped structure. The height of the metal lead wire (4) is the sum of the heights of the second metal frame (5) and the second metal cover plate (6), and the height is 1.6mm~1.65mm.

4. A method for fabricating a shell structure for a laser control module in a microwave photonics system, characterized in that, This method is used to prepare the shell structure of the laser control module of the microwave photonic system according to claim 1, comprising: Ceramic green porcelain strips with a thickness of 0.20mm~0.35mm were selected as ceramic parts (3); The ceramic parts (3) are drilled, filled, printed with metallized patterns, printed with ceramic slurry patterns (8), stacked, laminated, cut, and sintered. Nickel plating is performed on the metallized pattern on the surface of the sintered ceramic part (3); The nickel-plated ceramic part (3), metal lead wire (4), first metal frame (2), second metal frame (5), and silver-copper solder are placed into a prefabricated graphite mold and assembled together by high-temperature brazing to form a shell pre-product. The metal pattern on the surface of the shell pre-product is electroplated with nickel and gold layers. The electroplating wire (7) was cut off using a laser, and the outer frame of the metal lead (4) was trimmed.

5. The method for fabricating the shell structure of the laser control module of the microwave photonic system according to claim 4, characterized in that, The method of cutting the electroplating connection (7) using a laser includes: A protective adhesive is sprayed onto the surface of the double-sided cavity structure of the outer shell; The outer shell structure coated with protective adhesive (10) is placed in an oven to allow the protective adhesive (10) to cure. Create a laser cutting file based on the metal pattern on the ceramic part (3) and the location of the electroplating line that needs to be cut; Place the entire outer shell structure on the worktable of the laser equipment, and adjust the laser height so that the laser spot focus falls on the inner cavity surface of the outer shell structure; Align the outer contour of the shell structure, perform laser cutting according to the processing documents, and remove the protective adhesive after laser cutting.

6. The method for fabricating the shell structure of the laser control module of the microwave photonic system according to claim 4, characterized in that, The pre-assembled shell, which is brazed together at high temperature, includes: Brazing is performed using framed metal leads (4) and electroplated wires (7) on the ceramic part (3) to connect all networks. Nickel and gold layers are electroplated by binding wires on the metal leads (4).

7. The method for fabricating the shell structure of the laser control module of the microwave photonic system according to claim 4, characterized in that; The nickel layer has a thickness of 1.3-8.9 μm, and the gold layer has a thickness of 1.3-5.7 μm.

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