Ceramic and metal integrated hermetic packaging for high-speed optical module

Abstract

The application discloses a kind of high-speed optical module ceramic and metal integrated hermetic packaging in the field of optical communication packaging, including the sealing cavity mainly by from top to bottom Metal cover plate, transition ring, metal ring frame, ceramic substrate is formed, the circumferential side of metal ring frame is installed guide pipe, guide pipe, transition ring and metal ring frame are formed hermetic structure using silver copper welding process;The surface of guide pipe towards sealing cavity is provided with guide hole, the interface of fiber with sealing section passes through guide hole and extends into sealing cavity, and makes sealing section be located in guide hole.The application proposes a kind of packaging structure, ceramic substrate is used instead of PCB board as packaging shell, reduce product size;Using welding process of different temperature gradient, makes the hermetic packaging structure of integral type of fiber and sealing cavity, optical chip is directly connected with high thermal conductivity metal shell, enhances heat conduction performance, to realize the hermetic, miniaturization, good heat dissipation and high reliability of product.

Description

Technical Field

[0001] This invention relates to the field of optical communication packaging, specifically to a ceramic and metal integrated hermetically sealed package for high-speed optical modules. Background Technology

[0002] Optical modules are characterized by high integration, high performance, and flexible applications. With the development of 5G new infrastructure base station construction, they are widely used in civilian fields such as telecommunications backbone networks, data, communication, and storage networks. Simultaneously, due to their high speed and small size, they align with the miniaturization and lightweight development trend of aerospace components, becoming core optical devices in military fields such as satellite communication, spaceborne weapon platforms, and space station systems. However, current optical module products are mainly packaged using a PCB + metal casing process. On the one hand, PCB materials are polymers, which are prohibited materials in some high-reliability military applications, and PCBs have low thermal conductivity and poor heat dissipation performance. On the other hand, because optical fibers need to pass through the casing, an airtight structure cannot be formed at the fiber optic interface, making it impossible to achieve an airtight packaging for the entire optical module. For these reasons, traditional non-airtight optical modules cannot fully meet the requirements of aerospace, weaponry, and other military fields with high long-term reliability requirements. Summary of the Invention

[0003] The purpose of this invention is to provide a ceramic and metal integrated hermetically sealed package for high-speed optical modules to solve the problems mentioned in the background art.

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

[0005] A ceramic-metal integrated hermetic package for a high-speed optical module includes a sealed cavity mainly composed of a metal cover plate, a transition ring, a metal ring frame, and a ceramic substrate arranged from top to bottom. A guide tube is installed on one side of the circumferential direction of the metal ring frame. The guide tube, the transition ring, and the metal ring frame are formed into a hermetic structure by silver-copper soldering. A guide hole is opened on the surface of the guide tube facing the sealed cavity. The interface of the optical fiber with a sealing joint extends into the sealed cavity through the guide hole and places the sealing joint in the guide hole. The guide tube and the sealing joint are formed into a hermetic structure by gold-tin soldering.

[0006] As an improvement of the present invention, the metal ring frame is made of gradient aluminum-silicon material. At the bottom where the metal ring frame is fixed to the ceramic substrate, the silicon content is 75% (mass fraction), and the metal ring frame has a thermal expansion coefficient that matches the ceramic substrate. At the upper part where the metal ring frame is fixed to the transition ring, the silicon content is 50% (mass fraction).

[0007] As an improvement of the present invention, the metal ring frame is made of a high thermal conductivity encapsulation material.

[0008] As an improvement of the present invention, the ceramic substrate and the lower surface of the metal ring frame are airtightly welded using gold-tin solder sheets.

[0009] As an improvement of the present invention, the metal cover plate is made of Kovar alloy or aluminum-silicon alloy. When Kovar alloy is used, the metal cover plate and the transition ring are gas-tightly welded by parallel seam welding. When aluminum-silicon alloy is used, the metal cover plate and the transition ring are gas-tightly welded by laser welding.

[0010] As an improvement of the present invention, the ceramic substrate is an LTCC substrate or an HTCC substrate, and components are mounted or bonded to the upper surface.

[0011] As an improvement to the present invention, the guide tube is made of Kovar alloy.

[0012] As an improvement of the present invention, the sealing joint, the guide tube, and the optical fiber have matching coefficients of thermal expansion, and the optical fiber and the sealing joint are connected by gold-tin soldering to form an airtight connection.

[0013] As an improvement of the present invention, a protective sleeve is fitted on the outside of the interface of the optical fiber. The protective sleeve is made of rubber and is bonded and fixed to the metal ring frame.

[0014] Beneficial effects: Based on hybrid integration technology, this invention proposes a packaging structure with a ceramic substrate, a metal ring frame, an optical fiber, and a metal cover plate. The ceramic substrate replaces the PCB board, and the optical fiber and the sealed cavity are integrated into a hermetically sealed packaging structure by using welding processes with different temperature gradients, thereby achieving the product's airtightness, miniaturization, and high reliability. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the optical module packaging structure of the present invention;

[0016] Figure 2 This is an exploded view of the optical module packaging structure of the present invention.

[0017] Figure 3 This is a schematic diagram of the fiber optic assembly welding process of the present invention;

[0018] Figure 4 This is a schematic diagram of the metal ring frame structure of the present invention;

[0019] Figure 5 This is a schematic diagram of the ceramic substrate structure of the present invention.

[0020] In the figure: 1-Ceramic substrate; 2-Metal ring frame; 3-Transition ring; 4-Guide tube; 5-Gold solder pad; 6-Optical fiber; 7-Sealing joint; 8-Metal cover plate; 9-Spring frame; 10-Spring connector; 11-Protective sleeve; 12-Guide hole; 13-Metal connecting plate; 14-Optical chip. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1, see Figure 1-2 A ceramic-metal integrated hermetic package for high-speed optical modules includes a sealed cavity mainly composed of a metal cover plate 8, a transition ring 3, a metal ring frame 2, and a ceramic substrate 1 arranged from top to bottom.

[0023] The transition ring 3 is made of Kovar alloy, which has good machinability and strength. The metal cover plate 8 is made of Kovar alloy or aluminum-silicon alloy. When the metal cover plate 8 is made of Kovar alloy, the metal cover plate 8 and the transition ring 3 are gas-tightly welded by parallel seam welding; when aluminum-silicon alloy is used, the metal cover plate 8 and the transition ring 3 are gas-tightly welded by laser welding. The material of the metal cover plate 8 is mainly determined by the sealing process.

[0024] In a preferred embodiment, the metal ring frame 2 is made of gradient aluminum-silicon material. At the bottom where the metal ring frame 2 is fixed to the ceramic substrate 1, the silicon content is 75% by mass. The metal ring frame 2 has a thermal expansion coefficient that matches that of the ceramic substrate 1 to avoid ceramic cracking caused by welding thermal stress mismatch. At the top where the metal ring frame 2 is fixed to the transition ring 3, the silicon content is 50% by mass, which has good machinability and strength.

[0025] As a preferred embodiment, the metal ring frame 2 can also be made of other high thermal conductivity packaging materials, such as molybdenum copper, tungsten copper, Kovar, etc., to ensure effective heat dissipation on the one hand, and to match the coefficient of thermal expansion with the ceramic substrate 1 on the other hand, to prevent cracking after welding or temperature cycling.

[0026] like Figure 3-4 As shown, a stepped slot is formed on one side of the circumferential surface of the metal ring frame 2. A metal connecting plate 13 is formed between the two inner walls adjacent to the slot in the metal ring frame 2. An optical chip 14 is installed on the metal connecting plate 13. A guide tube 4 is installed in the slot. The guide tube 4 is made of Kovar alloy, which has good machinability and sealing performance. The guide tube 4, the transition ring 3 and the metal ring frame 2 are connected by silver-copper welding to form a reliable airtight structure. The silver-copper welding temperature is generally set at 820-840℃.

[0027] The guide tube 4 has a guide hole 13 on its surface facing the sealed cavity. The interface of the metallized optical fiber 6 extends into the sealed cavity through the guide hole 13 and is coupled to the optical chip 14 on the metal connection plate 13. The optical fiber 6 has a sealing joint 7, which is located in the guide hole 13. The sealing joint 7 can be made of Kovar alloy, molybdenum copper, tungsten copper, or other materials. It needs to have a matching coefficient of thermal expansion with the guide tube 4 and the optical fiber 6 to prevent the optical fiber 6 from breaking. The optical fiber 6 and the sealing joint 7 are connected by gold-tin solder to form an airtight connection. The space between the guide tube 4 and the sealing joint 7 is filled with gold-tin solder. Local induction heating is used to wet the gap between the guide hole 13 of the guide tube 4 and the sealing joint 7, forming an airtight structure that provides effective sealing protection for the interface of the optical fiber 6. In this embodiment, the temperature of the gold-tin solder can be set at about 280°C.

[0028] As a preferred embodiment, a protective sleeve 11 is fitted over the interface of the optical fiber 6. The protective sleeve 11 is made of rubber and is bonded and fixed to the metal ring frame 2, mainly to protect the exposed optical fiber 6.

[0029] The ceramic substrate 1 and the lower surface of the metal ring frame 2 are airtightly welded together using gold-tin solder sheets 5. The gold-tin solder sheets 5 can be stamped separately or pre-made on the surface of the ceramic substrate 1. After welding, a reliable airtight structure is formed.

[0030] like Figure 5 As shown, the ceramic substrate 1 uses an LTCC or HTCC substrate and has a multilayer wiring structure. Components are mounted or bonded on the upper surface, and signals are led out through metallized pads on the lower surface. The optical chip 14 is bonded to the ceramic substrate 1 through the gap between the metal connecting plate 13 and the remaining inner wall of the metal ring frame 2. The optical chip 14 generates a lot of heat, but it is directly mounted on the metal connecting plate 13, which facilitates good heat dissipation. In this embodiment, the spring frame 9 is fixed to the bottom of the ceramic substrate 1 by welding or bonding, and a spring connector 10 is set inside the spring frame 9. The spring connector 10 is fixed to the ceramic substrate 1 by welding or bonding. Therefore, the ceramic substrate 1 can realize the interconnection of internal and external signals through the spring connector. However, the signal lead-out method of the ceramic substrate 1 is not limited to the spring connector 10; signal lead-out can also be achieved through BGA, PGA, surface mount, etc.

[0031] In this embodiment, a ceramic substrate 1 is used instead of a PCB board. On the one hand, the ceramic substrate 1 can be directly used as the package body, effectively reducing the package size. On the other hand, the increased thermal conductivity is beneficial to improving heat dissipation performance. At the same time, by combining the materials system of ceramic substrate 1, aluminum-silicon metal ring frame 2, Kovar transition ring 3, Kovar metal cover plate 8, Kovar guide tube 4, and optical fiber 6 with sealing joint 7, and then using welding processes with different temperature gradients such as silver-copper soldering, gold-tin soldering, and parallel seam welding, an integrated hermetically sealed package of the optical module is achieved. Experiments show that the hermetically tight performance reaches within 1×10-3 Pa·cm3 / s (A4He), meeting the long-term high reliability requirements of military fields such as aerospace and weaponry.

[0032] In this embodiment, the ceramic substrate 1, metal ring frame 2, transition ring 3, guide tube 4, and spring clip frame 5 are first processed into the following shapes: Figure 2 The structure is shown; then, the metal ring frame 2, transition ring 3, and guide tube 4 are assembled by silver-copper soldering to form the ring frame assembly; next, the ceramic substrate 1 and the ring frame assembly are soldered by gold-tin soldering, and the optical chip 14 is directly connected to the metal connecting plate 13 to enhance the thermal conductivity. Then, the optical fiber 6 is passed through the guide hole 12 to ensure good assembly and coupling between the optical fiber 6 and other components. Gold-tin solder is filled between the sealing joint 7 and the guide tube 4, and a sealing structure is formed by local induction heating. After assembly, the metal cover plate 8 and transition ring 3 are finally welded by parallel seam welding or laser welding. A protective sleeve is glued to the interface of the optical fiber 6, and the spring frame and spring connector are glued or welded to the bottom of the ceramic substrate 1 to complete the final assembly. Figure 1 The optical module product shown.

[0033] This invention, based on hybrid integration technology, proposes a packaging structure with a ceramic substrate, a metal ring frame, an optical fiber, and a metal cover plate. The ceramic substrate replaces the PCB board as the packaging shell, reducing product size. A sealing joint structure is designed using welding processes with different temperature gradients, enabling the optical fiber and the sealed cavity to form an integrated hermetically sealed packaging structure. The optical chip is directly connected to a highly thermally conductive metal connecting plate, enhancing thermal conductivity. This achieves hermetically tight, miniaturized, well-ventilated, and highly reliable product. Furthermore, the processing technology and procedures are simple, highly reliable, and suitable for mass production.

[0034] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0035] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A ceramic-metal integrated hermetically sealed package for a high-speed optical module, comprising a sealed cavity mainly composed of a metal cover plate (8), a transition ring (3), a metal ring frame (2), and a ceramic substrate (1) arranged from top to bottom, characterized in that, A guide tube (4) is installed on one side of the metal ring frame (2). The guide tube (4), the transition ring (3), and the metal ring frame (2) are connected by silver-copper soldering to form an airtight structure. A metal connecting plate (15) is formed between two inner walls of the metal ring frame (2). An optical chip (14) is disposed on the metal connecting plate (15). A guide hole (13) is opened on the surface of the guide tube (4) facing the sealed cavity. The interface of the optical fiber (6) with the sealing joint (7) passes through the guide hole (13) and extends into the sealed cavity and is coupled to the optical chip. The sealing section (7) is located in the guide hole (13). The optical fiber (6) and the sealing section (7) are connected by gold-tin solder to form an airtight weld. The space between the guide tube (4) and the sealing section (7) is filled with gold-tin solder. The gap between the guide tube (4) and the sealing section (7) is wetted by local induction heating to form an airtight structure. The integrated airtight device is achieved by welding process with different temperature gradients of silver-copper soldering, gold-tin soldering and parallel seam welding. The temperature range of silver-copper soldering is 820-840℃. The temperature of gold-tin soldering is 280℃.

2. The ceramic-metal integrated hermetically sealed package for a high-speed optical module according to claim 1, characterized in that, The metal ring frame (2) is made of gradient aluminum silicon material. At the bottom where the metal ring frame (2) is fixed to the ceramic substrate (1), the mass fraction of silicon is 75%. The metal ring frame (2) has a thermal expansion coefficient that matches that of the ceramic substrate (1). At the top where the metal ring frame (2) is fixed to the transition ring (3), the mass fraction of silicon is 50%.

3. The ceramic-metal integrated hermetically sealed package for a high-speed optical module according to claim 2, characterized in that, The ceramic substrate (1) and the lower surface of the metal ring frame (2) are airtightly welded together using gold-tin solder sheets (5).

4. The ceramic-metal integrated hermetically sealed package for a high-speed optical module according to claim 3, characterized in that, The metal cover plate (8) is made of Kovar alloy or aluminum-silicon alloy. When Kovar alloy is used, the metal cover plate (8) and the transition ring (3) are gas-tightly welded by parallel seam welding. When aluminum-silicon alloy is used, the metal cover plate (8) and the transition ring (3) are gas-tightly welded by laser welding process.

5. A ceramic-metal integrated hermetically sealed package for a high-speed optical module according to claim 1 or 2, characterized in that, The ceramic substrate (1) is an LTCC substrate or an HTCC substrate, with components mounted or bonded on its upper surface. The optical chip (14) is bonded to the ceramic substrate (1) through the gap between the metal connecting plate (15) and the remaining inner wall of the metal ring frame (2).

6. The ceramic-metal integrated hermetically sealed package for a high-speed optical module according to claim 1, characterized in that, The guide tube (4) is made of Kovar alloy.

7. The ceramic-metal integrated hermetically sealed package for a high-speed optical module according to claim 6, characterized in that, The interface of the optical fiber (6) is covered with a protective sleeve (11), which is made of rubber and is bonded and fixed to the metal ring frame (2).

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