Optical packaging structure and method for optoelectronic chips

Abstract

This application relates to an optical packaging structure and method for an optoelectronic chip. The structure includes: an optoelectronic chip with at least one optical port; an optical fiber array with at least one optical fiber, the end of the optical fiber to be coupled being optically coupled to the optical port; an optical fiber array fixing body including a ring-shaped body for fixing the optical fiber array; one of the optoelectronic chip and the optical fiber array fixing body has at least one fusible metal bump on its surface, and the other has at least one metal protrusion on its surface, the positions of the metal protrusions corresponding one-to-one with the metal bumps; the metal bumps and the metal protrusions are mechanically connected by fusion welding; and a refractive index matching adhesive is filled into the gap between the optical port and the end of the optical fiber to be coupled. This structure can solve the technical problems of insufficient optical fiber-chip coupling alignment accuracy, poor fixing reliability, and complex processes in the prior art.

Description

Technical Field

[0001] This application relates to the field of optoelectronic integration technology, and in particular to an optical packaging structure and method for optoelectronic chips. Background Technology

[0002] With the rapid development of artificial intelligence, big data, cloud computing, and 5G / 6G communication technologies, the demand for high-speed optical interconnects within data centers and between servers is experiencing explosive growth. Photonic integrated circuits (PICs), especially silicon photonic chips, have become the core technology for next-generation optical communication and optical computing due to their advantages such as high integration, low power consumption, and compatibility with CMOS processes. In the manufacturing and packaging process of optoelectronic chips, optical coupling—that is, connecting the waveguides on the optical chip to external optical fibers in a low-loss, high-reliability manner—is one of the most technically challenging and costly links in the entire industry chain.

[0003] Currently, the coupling and packaging technologies for optoelectronic chips and optical fibers are mainly divided into two categories: active alignment and passive alignment. Active alignment technology transmits optical signals in the optical path, monitors the coupled optical power in real time, and precisely adjusts the position of the fiber or chip accordingly to achieve minimal coupling loss. This technology offers high precision but suffers from low assembly efficiency, high equipment investment, and stringent requirements for the operating environment. Passive alignment technology relies on precision-machined mechanical alignment structures (such as V-grooves and alignment marks) to define the relative position of the fiber and chip, eliminating the need for optical power monitoring during assembly. However, passive alignment requires extremely high processing precision and struggles to compensate for individual differences between devices and alignment drift caused by thermal stress. In terms of packaging and fixing technologies, UV-cured adhesive bonding is currently the most commonly used method. However, UV adhesives have limited long-term thermal stability; under high-temperature operating environments or after multiple temperature cycles, the adhesive layer may creep, age, or crack, leading to decreased coupling efficiency or even failure. While laser welding technology offers excellent long-term stability, the equipment is expensive, the process is complex, and there are strict limitations on material selection.

[0004] In summary, the existing technologies have the following technical problems: (1) Pure passive alignment accuracy is limited and it is difficult to meet the coupling loss requirements of high-performance optical modules; (2) Traditional active alignment has the risk of alignment drift during the curing process and relies on expensive six-dimensional adjustment equipment; (3) UV adhesive fixation has insufficient long-term thermal stability and mechanical reliability; (4) There is a lack of a simplified encapsulation solution that integrates precise alignment, reliable fixation and environmental sealing. Summary of the Invention

[0005] Therefore, it is necessary to provide an optical packaging structure and method for optoelectronic chips that combines high alignment accuracy, good connection reliability, simple process, and suitability for automated mass production, in order to address the above-mentioned technical problems.

[0006] In a first aspect, this application provides an optical packaging structure for an optoelectronic chip, comprising:

[0007] Optoelectronic chip, including at least one optical port;

[0008] An optical fiber array, comprising at least one optical fiber, wherein the end of the optical fiber to be coupled is optically coupled to the optical port;

[0009] The fiber optic array fixing body includes an annular body for fixing the fiber optic array. In the optoelectronic chip and the fiber optic array fixing body, one of the surfaces is provided with at least one fusible metal bump, and the other surface is provided with at least one metal protrusion. The positions of the metal protrusions correspond one-to-one with the metal bumps. The metal bumps and the metal protrusions are mechanically connected by fusion welding.

[0010] Refractive index matching adhesive is applied to the gap between the optical port and the end of the optical fiber to be coupled.

[0011] In one embodiment, the inner wall of the through hole of the annular body is provided with a positioning step, which is used to limit the insertion depth of the optical fiber.

[0012] In one embodiment, the optical port is an end-face coupler, and the optical coupling direction of the end-face coupler to the optical fiber is parallel to the surface of the optoelectronic chip.

[0013] In one embodiment, the fiber array fixing body further includes a cuboid, which is perpendicularly connected to the annular body. The perpendicular connection is provided with a rounded corner to reduce stress concentration. It is an integrally formed or welded metal structure, and the metal protrusions or metal bumps are provided on the surface of the cuboid.

[0014] In one embodiment, the optical port is a grating coupler, and the optical coupling direction of the grating coupler to the optical fiber is perpendicular to the surface of the optoelectronic chip.

[0015] In one embodiment, the metal bumps or metal protrusions are disposed on the surface of the annular body.

[0016] In one embodiment, the structure further includes a sealing cover plate covering the connection area between the optoelectronic chip and the optical fiber array, and is sealed to the optical fiber array fixture or the substrate of the optoelectronic chip to form an airtight package.

[0017] Secondly, this application also provides an optical packaging method for an optoelectronic chip based on the optoelectronic chip optical packaging structure described in the first aspect, comprising:

[0018] The fiber array fixture is placed above the optoelectronic chip, so that the metal protrusion contacts the metal bump.

[0019] The metal bumps are heated to melt them;

[0020] While the metal bumps are in a molten state, the coupled optical power is monitored and the relative position of the fiber array fixture and the optoelectronic chip is adjusted to achieve optical coupling between the optical port and the optical fiber.

[0021] The metal bumps are cooled and cured to form a mechanical connection between the fiber array fixture and the optoelectronic chip; and refractive index matching adhesive is filled into the gap between the optical port and the optical fiber and cured.

[0022] In one embodiment, monitoring the coupled optical power and adjusting the relative position of the fiber array fixture and the optoelectronic chip to achieve optical coupling between the optical port and the optical fiber includes:

[0023] By using active alignment technology, the relative positions of the fiber array fixture and the optoelectronic chip in six-dimensional space are adjusted by monitoring the coupled optical power or extinction ratio.

[0024] In one embodiment, after cooling the metal bumps to solidify them, thereby forming a mechanical connection between the fiber array fixture and the optoelectronic chip, and filling the gap between the optical port and the optical fiber with refractive index matching adhesive and allowing the refractive index matching adhesive to solidify, the method further includes covering the optical coupling area between the optoelectronic chip and the fiber array with a sealing cover.

[0025] The aforementioned optoelectronic chip optical packaging structure and method utilize the sliding motion of molten metal bumps within a molten metal bump pool, providing controllable positional adjustment freedom and improving alignment accuracy. After alignment, cooling and solidification form an intermetallic compound connection, exhibiting excellent shear strength and thermal stability. Compared to UV adhesive bonding, it can withstand a wider temperature range and more temperature cycles, significantly improving long-term reliability. The fiber array fixation unit integrates chip connection, fiber fixation, and structural support, reducing parts and assembly steps and facilitating automated mass production. Metal welding provides mechanical connection and initial sealing, while refractive index matching adhesive provides optical optimization and secondary protection, forming a dual protection system that effectively resists environmental stresses such as mechanical vibration, temperature cycling, and humidity changes. The materials and processes used are compatible with existing production lines, solving the technical problems of insufficient fiber-chip coupling alignment accuracy, poor fixation reliability, and complex processes in existing technologies. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a front view of the optical chip and fiber array after packaging in one embodiment;

[0028] Figure 2 This is a top view of the optical chip in one embodiment;

[0029] Figure 3 This is a left view of the fiber array fixture and the fiber array assembled in one embodiment;

[0030] Figure 4 This is a front view of the optical chip and fiber array after they have been packaged in another embodiment;

[0031] Figure 5 A top view of the optical chip in another embodiment;

[0032] Figure 6 This is a left view of the fiber array fixture and the fiber array assembled in another embodiment;

[0033] Figure 7 This is a flowchart illustrating an optical packaging method for an optoelectronic chip in one embodiment. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0035] To address the technical problems of insufficient fiber-to-chip coupling alignment accuracy, poor fixation reliability, and complex processes in existing technologies, this invention provides an optical packaging structure for an optoelectronic chip.

[0036] like Figures 1 to 6 As shown, the optical packaging structure of the optoelectronic chip includes an optoelectronic chip 5, a fiber array fixing body 1, a refractive index matching adhesive 6, and a fiber array 4.

[0037] The optoelectronic chip 5 can be a silicon photonic chip, an indium phosphide photonic chip, or a silicon nitride photonic chip, and includes at least one optical port 52 for optical signal coupling with each optical fiber 41 in the external optical fiber array.

[0038] The fiber array includes at least one fiber 41, which can be a single-mode fiber array or a multimode fiber array, and the number of channels can be 4, 8, 16 or 32. The end of the fiber to be coupled is optically coupled to the optical port.

[0039] The fiber optic array fixture 1 includes an annular body 12 for fixing the fiber optic array. In the optoelectronic chip 5 and the fiber optic array fixture 1, one surface has at least one fusible metal bump, and the other surface has at least one metal protrusion. The positions of the metal protrusions 2 correspond one-to-one with the metal bumps 51, and the metal bumps 51 and metal protrusions 2 are mechanically connected by fusion welding.

[0040] Refractive index matching adhesive 6 is applied to the gap between optical port 52 and the end of the optical fiber to be coupled. The refractive index of the refractive index matching adhesive can be selected from 1.40 to 1.50, and the difference between it and the refractive index of the fiber core should not exceed 0.05. It can be a UV-curable adhesive or a thermosetting adhesive.

[0041] It is understandable that during the encapsulation process of the above structure, the metal bumps 51 are first heated to melt and form a liquid pool. At this time, the metal bumps 2 can slide slightly in the liquid pool, providing a controllable degree of freedom for adjusting the relative position between the fiber array fixture 1 and the optoelectronic chip 5. In this floating state, the coupled optical power can be monitored in real time and the relative position of the two can be finely adjusted using active alignment technology. After alignment is completed, the metal bumps 51 are cooled and solidified, forming a stable intermetallic compound connection with the metal bumps 2, thereby achieving mechanical fixation between the fiber array fixture 1 and the optoelectronic chip 5. This metal connection has excellent shear strength and thermal stability. Compared with traditional UV adhesive bonding, it can withstand a wider operating temperature range and more temperature cycles, solving the problem of decreased coupling efficiency caused by adhesive layer creep and aging.

[0042] Based on this, the refractive index matching adhesive 6 is filled into the gap between the optical port 52 and the coupling end of the optical fiber 41. On the one hand, it matches the refractive index between the fiber core and the optical port, reducing interface reflection loss; on the other hand, it forms a secondary sealing protection for the optical coupling interface, isolating external dust and moisture, so that the encapsulation structure can effectively resist the influence of environmental stresses such as mechanical vibration, temperature cycling and humidity changes.

[0043] In addition, the fiber array fixture 1 integrates the metal protrusion 2 or metal bump 51 and the ring body 12 into a single metal component, which reduces the number of parts and assembly steps, simplifies the packaging process, and is conducive to automated mass production and cost control.

[0044] In one specific embodiment, an optical packaging structure for an optoelectronic chip is provided. For example... Figure 1 As shown, Figure 1This is a front view of the packaging structure, which includes an optoelectronic chip 5, a fiber array fixture 1, a refractive index matching adhesive 6, a fiber array 4, and fiber 41 in the array.

[0045] Among them, the optoelectronic chip 5 is a silicon photonic chip, and its optical port 52 is an end-face coupler, which is used to couple optical signals horizontally with each optical fiber 41 in the external optical fiber array 4.

[0046] Specifically, the end-face coupler can be a mode-spot converter, an inverted conical waveguide coupler, or a lens-integrated coupler. In this embodiment, a mode-spot converter is used as an example for illustration.

[0047] like Figure 2 As shown, a series of fusible metal bumps 51 are included near the end face coupler.

[0048] like Figure 3 As shown, the fiber optic array fixture 1 consists of two mutually perpendicular cuboids 11 and an annular body 12. The two cuboids and the annular body are perpendicularly connected, and the perpendicular connection is provided with rounded corners to reduce stress concentration. It is a one-piece or welded metal structure. The lower surface of the cuboid 11 contains a series of metal protrusions 2, whose positions correspond one-to-one with the metal bumps 51 on the optoelectronic chip 5.

[0049] The fiber array 4 is an 8-channel single-mode fiber array, which is fixed to the precision through hole of the ring body 12 by the fixing glue 3.

[0050] Optionally, the inner wall of the through hole of the annular body is also provided with positioning steps to control the fiber insertion depth, so that the coupling distance between the end face of the fiber and the optical port is 5 micrometers to 10 micrometers.

[0051] Similar to the above embodiments, in one embodiment, an optical packaging method for an optoelectronic chip with metal bumps disposed on a fiber array fixture is provided.

[0052] Still with Figure 1 For example, the fusible metal bump 51 at high temperatures can also be disposed on the fiber array fixture 1, specifically on the lower surface of the cuboid 11, while the metal bump is disposed on the optoelectronic chip 5, and can be a square copper or aluminum pad. This variant is functionally equivalent to the above embodiment, but has process advantages in certain application scenarios. For example, when the manufacturing process of the optoelectronic chip is not suitable for directly forming tin bumps, tin bumps can be formed on the subsequent fixture, improving process flexibility.

[0053] In another specific embodiment, such as Figure 4 As shown, an optical packaging structure for an optoelectronic chip suitable for vertical optical coupling scenarios using grating couplers is provided.

[0054] The difference from the above embodiments is that the optical port of the optoelectronic chip 5 is a grating coupler, which is used to realize the input and output of optical signals in a direction perpendicular to the surface of the optoelectronic chip.

[0055] The fiber array fixing body 1 consists only of a ring-shaped body 12, without any cuboid structure perpendicular to it. The ring-shaped body 12 is directly fixed to the surface of the optoelectronic chip 5 by engaging with the metal bumps on the optoelectronic chip 5 through metal protrusions on its lower surface. The optical fiber 41 extends vertically downward from the through-hole of the ring-shaped body 12, and the coupling distance between its end face and the grating coupler is limited by a positioning step.

[0056] In this embodiment, due to the vertical coupling characteristics of the grating coupler, there is no need for a cuboid structure to extend the optical path. This structure makes the packaging structure more compact, which is beneficial for realizing a high-density optical I / O array.

[0057] It is understood that the above-described packaging structure applicable to grating couplers can also be implemented by setting metal bumps on the fiber array fixture and metal protrusions on the optoelectronic chip. Other parts of this packaging structure are similar to the above-described embodiments and will not be described in detail here.

[0058] In one exemplary embodiment, the metal protrusion is made of copper, gold, or a nickel-gold alloy, and is cylindrical or truncated conical in shape with a height of 20 micrometers to 100 micrometers.

[0059] The metal bump can be made of at least one of tin, gold-tin alloy, indium, or bismuth-tin alloy, and is hemispherical before melting. After melting and solidification, the metal bump forms a welded joint with a smooth top. The shear strength of the welded joint is not less than 10 MPa, and the electrical resistance is not higher than 10 mΩ.

[0060] In one exemplary embodiment, to further enhance the hermetic seal, a sealing cover is also placed over the optical coupling region of the optoelectronic chip after the refractive index matching adhesive is filled and cured.

[0061] Optionally, the sealing cover is made of Kovar alloy, whose coefficient of thermal expansion matches that of the silicon chip and glass fiber. The sealing cover is laser-welded to the substrate of the fiber array fixture or optoelectronic chip to form a hermetic package. This hermetic packaging solution is suitable for aerospace and submarine optical communication applications with high reliability requirements.

[0062] Based on the same inventive concept, this application also provides an optical packaging method for optoelectronic chips based on the above-described packaging structure. The solution provided by this method is similar to the solution described above. Therefore, the specific limitations in one or more embodiments of the optoelectronic chip optical packaging method provided below can be found in the limitations on the optoelectronic chip optical packaging structure described above, and will not be repeated here.

[0063] In one exemplary embodiment, such as Figure 7 As shown, an optical packaging method for optoelectronic chips is provided, comprising:

[0064] Step S1: Place the fiber array fixture above the optoelectronic chip so that the metal protrusions contact the metal bumps.

[0065] Step S2: Heat the metal bumps to melt them.

[0066] Optionally, the heating method can be hot plate heating, laser local heating or induction heating, and the heating temperature can be determined by the material of the metal protrusion.

[0067] Step S3: While the metal bumps are in a molten state, monitor the coupled optical power and adjust the relative position of the fiber array fixture and the optoelectronic chip to achieve optical coupling between the optical port and the optical fiber.

[0068] For example, active alignment technology is used to adjust the relative positions of the fiber array fixture and the optoelectronic chip in six-dimensional space by monitoring the coupled optical power or extinction ratio.

[0069] It is understandable that when the metal bump is in a molten state, the metal bump can slide in the bump liquid pool. At this time, with the help of active alignment technology, the coupling optical power can be monitored in real time and the relative position of the fiber array fixation body and the optoelectronic chip can be finely adjusted, so that low-loss optical coupling can be achieved between the optical port and the optical fiber. This combines the process simplification of passive alignment with the high precision of active alignment.

[0070] Step S4: Cool the metal bumps to solidify them, so that the fiber array fixture and the optoelectronic chip can be mechanically connected; and fill the gap between the optical port and the optical fiber with refractive index matching glue and let the refractive index matching glue solidify.

[0071] Alternatively, cooling methods such as air cooling or TEC cooling can be used, and the cooling rate can be adjusted as needed, thereby controlling the microstructure and mechanical strength of the metal bumps after solidification.

[0072] For example, when using metal bumps made of gold-tin alloy, the higher melting point and superior creep resistance of gold-tin alloy bumps make them suitable for applications with higher operating temperatures. Considering the melting temperature of the material, the heating temperature and cooling rate need to be readjusted. The heating temperature should be adjusted to 300°C to 320°C, and the cooling rate to 1°C / second to 5°C / second, to obtain a fine gold-tin eutectic structure, thereby improving the mechanical strength and fatigue life of the joint.

[0073] In some embodiments, when the packaging structure of the optoelectronic chip has a high hermeticity requirement, the following step is included after step S4:

[0074] A sealing cover is placed over the optical coupling area between the optoelectronic chip and the fiber optic array. The sealing cover is then laser-welded to the fiber optic array fixture or the substrate of the optoelectronic chip to form a hermetically sealed package.

[0075] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0076] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0077] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. An optoelectronic chip optical packaging structure, characterized by, include: Optoelectronic chip, including at least one optical port; An optical fiber array, comprising at least one optical fiber, wherein the end of the optical fiber to be coupled is optically coupled to the optical port; The fiber optic array fixing body includes an annular body for fixing the fiber optic array. In the optoelectronic chip and the fiber optic array fixing body, one of the surfaces is provided with at least one fusible metal bump, and the other surface is provided with at least one metal protrusion. The positions of the metal protrusions correspond one-to-one with the metal bumps. The metal bumps and the metal protrusions are mechanically connected by fusion welding. Refractive index matching adhesive is applied to the gap between the optical port and the end of the optical fiber to be coupled.

2. The structure of claim 1, wherein The inner wall of the through hole of the annular body is provided with a positioning step, which is used to limit the insertion depth of the optical fiber.

3. The structure of any one of claim 1 or claim 2, wherein, The optical port is an end-face coupler, and the optical coupling direction of the end-face coupler and the optical fiber is parallel to the surface of the optoelectronic chip.

4. The structure of claim 3, wherein The fiber array fixing body also includes a cuboid, which is perpendicularly connected to the annular body. The perpendicular connection is provided with a rounded corner to reduce stress concentration. It is a one-piece molded or welded metal structure. The metal protrusions or metal bumps are provided on the surface of the cuboid.

5. The structure according to claim 1 or claim 2, characterized in that, The optical port is a grating coupler, and the optical coupling direction of the grating coupler and the optical fiber is perpendicular to the surface of the optoelectronic chip.

6. The structure of claim 5, wherein The metal bumps or metal protrusions are disposed on the surface of the annular body.

7. The structure of claim 1, wherein Also includes: A sealing cover is placed over the connection area between the optoelectronic chip and the optical fiber array, and is sealed to the optical fiber array fixture or the substrate of the optoelectronic chip to form an airtight package.

8. An optoelectronic chip optical packaging method based on the optoelectronic chip optical packaging structure according to any one of claims 1 to 7, characterized in that, The method includes: The fiber array fixture is placed above the optoelectronic chip, so that the metal protrusion contacts the metal bump. The metal bumps are heated to melt them; While the metal bumps are in a molten state, the coupled optical power is monitored and the relative position of the fiber array fixture and the optoelectronic chip is adjusted to achieve optical coupling between the optical port and the optical fiber. The metal bumps are cooled and cured to form a mechanical connection between the fiber array fixture and the optoelectronic chip; and refractive index matching adhesive is filled into the gap between the optical port and the optical fiber and cured.

9. The method of claim 8, wherein, The step of monitoring the coupled optical power and adjusting the relative position of the fiber array fixture and the optoelectronic chip to achieve optical coupling between the optical port and the optical fiber includes: By using active alignment technology, the relative positions of the fiber array fixture and the optoelectronic chip in six-dimensional space are adjusted by monitoring the coupled optical power or extinction ratio.

10. The method of claim 9, wherein, After cooling and curing the metal bumps to form a mechanical connection between the fiber array fixture and the optoelectronic chip, and filling the gap between the optical port and the optical fiber with refractive index matching adhesive and allowing the adhesive to cure, the method further includes: A sealing cover is placed over the optical coupling area between the optoelectronic chip and the fiber array.

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