Tir microlens array coupling method based on micro-led optical interconnection

Abstract

The application relates to the technical field of Micro-LED optical interconnection technology and optical coupling, in particular to a TIR microlens array coupling method based on Micro-LED optical interconnection, which is a Micro-LED chip and a TIR microlens array high-efficiency coupling module, and through an integrated process of mechanical pre-alignment, optical feedback manual fine alignment and elastic stress compensation fixing, the problems of large alignment error, high loss and weak environmental adaptability in the traditional coupling method are solved. Meanwhile, through accurate matching with the parameter design in the preparation stage of the TIR microlens array, the coupling link is optimized in cooperation, and the overall performance of the optical interconnection link is maximally improved.

Description

Technical Field

[0001] This invention relates to the technical field of Micro-LED optical interconnect technology and optical coupling, specifically to a TIR microlens array coupling method based on Micro-LED optical interconnect. Background Technology

[0002] As optical interconnect technology develops towards higher speeds, miniaturization, and integration, the coupling efficiency between Micro-LEDs, as core light-emitting devices, and TIR microlens arrays directly determines the performance of optical interconnect links. TIR microlens arrays have gained widespread attention in the field of Micro-LED optical interconnects due to their high light-gathering efficiency and lack of additional reflection loss. However, existing coupling technologies still have many shortcomings. The relevant background technologies mainly present the following status: In the coupling of Micro-LEDs and TIR microlens arrays, existing technologies are mainly divided into passive alignment coupling and active alignment coupling. Passive alignment coupling achieves alignment between the two through mechanical positioning structures (such as positioning pins and positioning slots). This method is simple to operate and low in cost, but the alignment accuracy is low, resulting in high coupling loss, which makes it difficult to meet the low-loss requirements of high-speed optical interconnects. Active alignment coupling achieves precise alignment by real-time monitoring of optical coupling efficiency and adjusting the relative positions of the two. The alignment accuracy is high, but it requires complex alignment equipment, is cumbersome to operate, has low coupling efficiency, and the fixing method after coupling is prone to stress, leading to coupling accuracy drift. In addition, existing coupling structures lack effective environmental adaptability design. Under harsh environments such as vibration and high and low temperatures, the coupling accuracy is prone to decrease, affecting the stability of optical signal transmission.

[0003] Meanwhile, in existing technologies, the fabrication process and coupling method are independent of each other, lacking synergistic optimization design. For example, the size, spacing, and other parameters of the fabricated TIR microlens array do not fully consider the coupling compatibility with the Micro-LED chip, leading to increased difficulty in subsequent coupling. The surface characteristics of the microlens array are not considered during coupling, easily causing surface contamination and further increasing coupling losses. Furthermore, existing coupling methods have poor material compatibility, making it difficult to adapt to Micro-LED chips on different substrates, thus limiting their application range. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a TIR microlens array coupling method based on Micro-LED optical interconnects, which solves the problems mentioned in the background section. Technical solution

[0005] To achieve the above objectives, the present invention provides the following technical solution: a TIR microlens array coupling method based on Micro-LED optical interconnects, characterized by comprising the following steps: S1, Parameter Co-design: Based on the key parameters of the target Micro-LED chip, the structural parameters of the TIR microlens are optimized in reverse; when fabricating the TIR microlens array, positioning marks matching the four corner positioning holes of the Micro-LED chip are reserved at the edge of the array. S2, Preparation before coupling: Ensure that the Micro-LED chip and the TIR microlens array are clean and stably fixed to avoid impurities and fixing deviations affecting coupling accuracy; including device cleaning and device fixing. S3, Mechanical pre-alignment: Quickly narrows the alignment deviation range through visual positioning, laying the foundation for subsequent active fine alignment and reducing the time required for fine alignment; including positioning mark recognition and preliminary alignment; S4, manual fine alignment with optical feedback: By monitoring the optical coupling efficiency in real time, manual fine-tuning is used to achieve precise alignment between the Micro-LED chip and the TIR microlens array; including optical signal excitation, optical power monitoring and manual fine alignment; S5, Elastic Stress Compensation Fixing: Achieves stable fixing of Micro-LED chips and TIR microlens arrays, while compensating for stress generated during the fixing process, avoiding coupling accuracy drift, and improving environmental adaptability; including adhesive selection and coating, UV curing and stress compensation; S6, Coupling performance test: Verify the performance indicators of the coupling structure to ensure that it meets the requirements of optical interconnection. Qualified products complete the coupling, and unqualified products are reworked. S3 is used for secondary alignment and fixation and subsequent steps are repeated.

[0006] Preferably, the device cleaning involves cleaning the Micro-LED chip and the TIR microlens array separately; the specific cleaning steps are to first gently wipe the surface with anhydrous ethanol, then blow it dry with nitrogen, and finally use plasma cleaning.

[0007] Preferably, the device is fixed by fixing the Micro-LED chip on the vacuum chuck of the chip carrier stage, and the chip carrier stage is equipped with a temperature control function; the TIR microlens array is fixed on the fixture of the high-precision three-dimensional displacement stage with conductive adhesive.

[0008] Preferably, the positioning mark recognition is achieved by using a visual positioning system to activate the coupling device, which captures images of the four corner positioning holes of the Micro-LED chip and the corresponding positioning marks of the TIR microlens array. The preliminary alignment is achieved by controlling a high-precision three-dimensional displacement stage to move along the X, Y, and Z axes based on the center coordinate deviation between the preset four corner positioning holes of the Micro-LED chip and the preset corresponding positioning marks of the TIR microlens array, thereby adjusting the position of the TIR microlens array and simultaneously adjusting the parallelism between the chip carrier stage and the three-dimensional displacement stage.

[0009] Preferably, the optical signal excitation is achieved by turning on the Micro-LED chip driver power supply, using a constant current driving mode, and setting the driving current; the optical power monitoring is achieved by placing an optical power meter probe at the light-emitting end of the TIR microlens array to ensure that all emitted optical signals can be received by the optical power meter probe; the optical power meter displays the optical output power data in real time, providing an intuitive reference for manual alignment.

[0010] Preferably, the manual fine alignment involves observing the real-time readings of the optical power meter, manually controlling the high-precision three-dimensional displacement stage to make fine adjustments along the X, Y, and Z axes, and simultaneously manually adjusting the rotation angle of the TIR microlens array.

[0011] Preferably, the selection and application of the fixing adhesive are based on the thermal expansion coefficient of the Micro-LED chip substrate and the refractive index of the SiO2 antireflection film on the surface of the TIR microlens array. The specific application steps are to use a dispensing machine to apply an appropriate amount of curing adhesive to the edge gap between the Micro-LED chip and the TIR microlens array.

[0012] Preferably, the ultraviolet curing involves irradiating the coated area with an ultraviolet light source for curing; the stress compensation involves placing the coupling structure in a vacuum oven for low-temperature annealing after curing to release the internal stress generated during the curing process.

[0013] Preferably, the specific steps for the coupling performance test are as follows: turn on the Micro-LED chip driver power supply and test the coupling loss using an optical power meter; test the spectral stability of the optical signal using a spectrometer; place the coupling structure in a high and low temperature test chamber and test the coupling loss at different temperatures; fix the coupling structure on a vibration test bench and perform random vibration tests.

[0014] (III) Beneficial Effects This invention provides a TIR microlens array coupling method based on Micro-LED optical interconnects, which has the following beneficial effects: 1. Improve coupling alignment accuracy and reduce coupling loss. Adopt an integrated pre-alignment-manual fine alignment method, resulting in low coupling alignment error, reduced coupling loss, and increased optical signal transmission power; short single-channel coupling time and improved coupling efficiency of large-scale arrays.

[0015] 2. Enhance the stability and environmental adaptability of the coupled structure by adopting the "elastic stress compensation and fixing" design, which reduces residual curing stress; under vibration and high and low temperature environments, the coupling loss changes little and the structural stability is significantly improved.

[0016] 3. Improve the synergy between fabrication and coupling, and expand the application range. Through parameter synergy optimization, the compatibility of TIR microlens arrays with Micro-LED chips on different substrates is improved; the surface contamination rate is reduced during coupling, further reducing light reflection loss.

[0017] 4. The process is simplified and the operation threshold is lowered. The coupling method uses integrated equipment, which improves the degree of automation and can complete the coupling operation without professional operators. The precise control of alignment parameters reduces the difficulty of operation and is conducive to the promotion and application of the technology.

[0018] 5. Optimize the reliability of the coupling structure and extend its service life. Annealing not only improves environmental adaptability, but also effectively reduces the performance degradation of the coupling structure during long-term use. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the coupling process of the present invention; Figure 2 This is a schematic cross-sectional view of the coupled structure; Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] In this application, the terms "upper," "lower," "inner," "middle," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0022] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0023] Example 1: Please refer to Figures 1 to 2 This invention provides a technical solution: 1. A TIR microlens array coupling method based on Micro-LED optical interconnect, comprising the following steps: S1, Parameter Co-design: Based on the key parameters of the target Micro-LED chip (such as the size of the light-emitting area, the emission angle, and the emission wavelength), the structural parameters of the TIR microlens (such as the diameter, spacing, radius of curvature, and numerical aperture) are optimized in reverse using optical simulation software (such as ZEMAX). For example, when the diameter of the Micro-LED light-emitting area is 10μm and the emission angle is ±30°, the corresponding TIR microlens are designed with a diameter of 15μm, a radius of curvature of 8μm, and a spacing of 20μm to ensure that the light signal emitted by the Micro-LED can be fully focused by the microlens. When fabricating the TIR microlens array, positioning marks matching the four corner positioning holes of the Micro-LED chip are reserved at the edge of the array. The size and position of the positioning marks are required to be completely consistent with the four corner positioning holes of the Micro-LED chip. The fabrication of the positioning marks adopts the same photolithography etching process as the TIR microlens array to ensure that the center deviation of the positioning marks is ≤0.1μm. S2, Preparation before coupling: Ensure that the Micro-LED chip and the TIR microlens array are clean and stably fixed to avoid impurities and fixing deviations affecting coupling accuracy; including device cleaning and device fixing. S3, Mechanical pre-alignment: Quickly narrows the alignment deviation range through visual positioning, laying the foundation for subsequent active fine alignment and reducing the time required for fine alignment; including positioning mark recognition and preliminary alignment; S4, manual fine alignment with optical feedback: By monitoring the optical coupling efficiency in real time, manual fine-tuning is used to achieve precise alignment between the Micro-LED chip and the TIR microlens array. This is a key step in reducing coupling loss; it includes optical signal excitation, optical power monitoring and manual fine alignment. S5, Elastic Stress Compensation Fixing: Achieves stable fixing of Micro-LED chips and TIR microlens arrays, while compensating for stress generated during the fixing process, avoiding coupling accuracy drift, and improving environmental adaptability; including adhesive selection and coating, UV curing and stress compensation; S6, Coupling performance test: Verify the performance indicators of the coupling structure to ensure that it meets the requirements of optical interconnection. Qualified products complete the coupling, and unqualified products are reworked. S3 is used for secondary alignment and fixation and subsequent steps are repeated.

[0024] The device cleaning process involves cleaning the Micro-LED chip (in this embodiment, the chip size is selected as 100μm×100μm-500μm×500μm, and the emission wavelength is 850nm-1550nm) and the TIR microlens array respectively. The specific cleaning steps are as follows: First, gently wipe the surface with a lint-free cotton swab soaked in anhydrous ethanol (purity ≥99.7%), ensuring that the wiping direction is unidirectional and avoiding reciprocating friction to remove surface dust and oil. Then, dry it with nitrogen gas (flow rate 5L / min). Finally, use plasma cleaning (O2 atmosphere, power 50W, processing time 10s) to remove organic residues on the surface (the particle size of surface impurities after cleaning is ≤0.1μm). During the cleaning process, avoid damaging the SiO2 antireflection film and protective film on the surface of the TIR microlens array, and ensure that the surface roughness is maintained at Ra≤10nm.

[0025] The device is fixed by fixing the Micro-LED chip onto the vacuum chuck (0.03MPa adsorption) of the chip carrier stage. The chip carrier stage is equipped with a temperature control function (the temperature is controlled at 25℃±2℃ to avoid thermal expansion and deformation of the Micro-LED chip due to temperature changes). The TIR microlens array is fixed onto the fixture of the high-precision three-dimensional displacement stage with conductive adhesive (the conductive adhesive thickness is 50μm to ensure that the surface flatness of the TIR microlens array is ≤0.2μm / mm after fixing). During the fixing process, the surface of the TIR microlens array is not squeezed.

[0026] The positioning mark recognition is achieved by activating the visual positioning system of the coupling device (in this embodiment, two high-definition CCD cameras with a resolution ≤0.5μm and a magnification of 100x are used) to photograph the four corner positioning holes (positioning hole diameter 2μm, depth 1μm) of the Micro-LED chip and the corresponding positioning marks of the TIR microlens array. The preliminary alignment is achieved by controlling a high-precision three-dimensional displacement stage to move along the X, Y, and Z axes (movement step size 1μm) based on the center coordinate deviation between the four corner positioning holes of the Micro-LED chip and the corresponding positioning marks of the TIR microlens array, adjusting the position of the TIR microlens array so that the center coordinate deviation between the four corner positioning holes of the Micro-LED chip and the corresponding positioning marks of the TIR microlens array is controlled within 5μm. At the same time, the parallelism between the chip carrier stage and the three-dimensional displacement stage is adjusted (monitored by a laser interferometer, parallelism error ≤0.5μm / mm) to avoid the optical signal propagation path shift due to the tilt of the two.

[0027] The optical signal excitation involves turning on the Micro-LED chip driver power supply, using a constant current driving mode, and setting the driving current to 10-50mA (adjusted according to the rated current of the Micro-LED chip to avoid overcurrent damage), enabling the Micro-LED chip to emit light stably (the ripple coefficient of the driver power supply is ≤1% to ensure stable luminous intensity). The optical power monitoring involves placing an optical power meter probe (with a receiving aperture ≥1mm, measurement accuracy ±0.01dBm, and measurement range -70dBm to +10dBm) at the light-emitting end of the TIR microlens array. The distance between the optical power meter probe and the light-emitting surface of the TIR microlens array is adjusted to 5mm to ensure that all emitted light signals can be received by the optical power meter probe. The optical power meter displays the optical output power data in real time, providing an intuitive reference for manual precision alignment.

[0028] The manual fine alignment involves the operator observing the real-time readings of the optical power meter and manually controlling the high-precision three-dimensional displacement stage to make fine adjustments along the X, Y, and Z axes (fine-tuning step size 0.1μm), while simultaneously manually adjusting the rotation angle of the TIR microlens array (fine-tuning step size 0.01°). During the fine-tuning process, the light output power will increase with the improvement of alignment accuracy. When the optical power meter shows that the light output power has reached its maximum value and the fluctuation is ≤0.5% for 3 consecutive seconds, the fine-tuning is stopped. At this time, the alignment error between the light-emitting center of the Micro-LED chip and the center of the TIR microlens is ≤1μm, and the manual fine alignment is completed. The entire fine alignment process requires the operator to accurately control the process in conjunction with the optical power data to ensure alignment accuracy.

[0029] The selection and application of the fixing adhesive are based on the thermal expansion coefficient of the Micro-LED chip substrate and the refractive index of the SiO2 antireflection film on the surface of the TIR microlens array. The selected adhesive is a UV-curable adhesive with a shrinkage rate of ≤2% and a refractive index of 1.5-1.6, which has good bonding strength and resistance to high and low temperatures. The specific coating steps are as follows: an appropriate amount of UV-curable adhesive is applied to the edge gap between the Micro-LED chip and the TIR microlens array using a dispensing machine. The coating amount is 0.1μL-0.5μL (edge ​​gap width 5μm-10μm, coating range is around the Micro-LED chip, avoiding the adhesive from covering the light-emitting area and the effective area of ​​the TIR microlens array).

[0030] The ultraviolet curing involves irradiating the coated area with an ultraviolet light source (in this embodiment, a wavelength of 365nm and a power of 50-100mW) for 30-60 seconds, resulting in a bond strength ≥5MPa after curing; this constitutes the coupling structure. The stress compensation involves placing the coupling structure in a vacuum oven for low-temperature annealing after curing (temperature 80℃-100℃, vacuum degree ≤1Pa, time 30min), raising the temperature to the target temperature at a rate of 1℃ / min, holding it at that temperature, and then allowing it to cool naturally to room temperature. This annealing process releases the internal stress generated during curing (stress residue ≤5MPa).

[0031] The specific steps for the coupling performance test are as follows: Turn on the Micro-LED chip driver power supply (the driving current is consistent with the manual alignment stage of the optical feedback); test the coupling loss using an optical power meter (measurement accuracy ±0.01dBm), where coupling loss = ((Micro-LED chip direct light emission power - light emission power after passing through the TIR microlens array) / Micro-LED chip direct light emission power) x 100%, with a pass / fail standard of coupling loss ≤5%; test the spectral stability of the light signal using a spectrometer (wavelength resolution 0.1nm), with a spectral half-width variation ≤0.5nm for pass; place the coupling structure in a high and low temperature test chamber (temperature range -40℃-85℃), and hold it at -40℃, 25℃, and 85℃ for 30 minutes each, testing the coupling loss at different temperatures, with a loss variation ≤1% for pass; fix the coupling structure on a vibration test bench (frequency range 10Hz-1000Hz) and perform random vibration tests at frequencies of 10Hz-1000Hz and accelerations of 10g, with a coupling loss variation ≤1% after the test for pass.

[0032] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A TIR microlens array coupling method based on Micro-LED optical interconnects, characterized in that, Includes the following steps: S1, Parameter Co-design: Based on the key parameters of the target Micro-LED chip, the structural parameters of the TIR microlens are optimized in reverse; when fabricating the TIR microlens array, positioning marks matching the four corner positioning holes of the Micro-LED chip are reserved at the edge of the array. S2, Preparation before coupling: Ensure that the Micro-LED chip and the TIR microlens array are clean and stable, and avoid impurities and fixing deviations from affecting the coupling accuracy; Includes component cleaning and component securing; S3, Mechanical pre-alignment: Quickly narrows the alignment deviation range through visual positioning, laying the foundation for subsequent active fine alignment and reducing the time required for fine alignment; including positioning mark recognition and preliminary alignment; S4, manual fine alignment with optical feedback: By monitoring the optical coupling efficiency in real time, manual fine-tuning is used to achieve precise alignment between the Micro-LED chip and the TIR microlens array; including optical signal excitation, optical power monitoring and manual fine alignment; S5, Elastic Stress Compensation Fixing: Achieves stable fixing of Micro-LED chips and TIR microlens arrays, while compensating for stress generated during the fixing process, avoiding coupling accuracy drift, and improving environmental adaptability; including adhesive selection and coating, UV curing and stress compensation; S6, Coupling performance test: Verify the performance indicators of the coupling structure to ensure that it meets the requirements of optical interconnection. Qualified products complete the coupling, and unqualified products are reworked. S3 is used for secondary alignment and fixation and subsequent steps are repeated.

2. The TIR microlens array coupling method based on Micro-LED optical interconnection according to claim 1, characterized in that: The device cleaning process involves cleaning the Micro-LED chip and the TIR microlens array separately. The specific cleaning steps are: first, gently wipe the surface with anhydrous ethanol, then dry it with nitrogen, and finally use plasma cleaning.

3. The TIR microlens array coupling method based on Micro-LED optical interconnection according to claim 2, characterized in that: The device is fixed by fixing the Micro-LED chip on the vacuum chuck of the chip carrier stage, and the chip carrier stage is equipped with temperature control function; the TIR microlens array is fixed on the fixture of the high-precision three-dimensional displacement stage with conductive adhesive.

4. The TIR microlens array coupling method based on Micro-LED optical interconnection according to claim 1, characterized in that: The positioning mark recognition refers to the activation of the visual positioning system of the coupling device, which captures images of the four corner positioning holes of the Micro-LED chip and the corresponding positioning marks of the TIR microlens array. The preliminary alignment refers to the control of a high-precision three-dimensional displacement stage to move along the X, Y, and Z axes based on the center coordinate deviation between the preset four corner positioning holes of the Micro-LED chip and the preset corresponding positioning marks of the TIR microlens array, thereby adjusting the position of the TIR microlens array and simultaneously adjusting the parallelism between the chip carrier stage and the three-dimensional displacement stage.

5. The TIR microlens array coupling method based on Micro-LED optical interconnection according to claim 1, characterized in that: The optical signal excitation is achieved by turning on the Micro-LED chip driver power supply, using a constant current driving mode, and setting the driving current; the optical power monitoring is achieved by placing an optical power meter probe at the light-emitting end of the TIR microlens array to ensure that all emitted optical signals can be received by the optical power meter probe; the optical power meter displays the optical output power data in real time, providing an intuitive reference for manual alignment.

6. The TIR microlens array coupling method based on Micro-LED optical interconnection according to claim 5, characterized in that: The manual fine alignment refers to observing the real-time reading of the optical power meter, manually controlling the high-precision three-dimensional displacement stage to make fine adjustments along the X, Y, and Z axes, and simultaneously manually adjusting the rotation angle of the TIR microlens array.

7. The TIR microlens array coupling method based on Micro-LED optical interconnection according to claim 1, characterized in that: The selection and coating of the fixing adhesive are based on the thermal expansion coefficient of the Micro-LED chip substrate and the refractive index of the SiO2 antireflection film on the surface of the TIR microlens array. The specific coating operation steps are to use a dispensing machine to apply an appropriate amount of curing adhesive to the edge gap between the Micro-LED chip and the TIR microlens array.

8. The TIR microlens array coupling method based on Micro-LED optical interconnection according to claim 7, characterized in that: The ultraviolet curing involves directing an ultraviolet light source at the coated area and curing it; the stress compensation involves placing the coupling structure in a vacuum oven for low-temperature annealing after curing to release the internal stress generated during the curing process.

9. The TIR microlens array coupling method based on Micro-LED optical interconnection according to claim 1, characterized in that: The specific steps for the coupling performance test are as follows: turn on the Micro-LED chip driver power supply and test the coupling loss using an optical power meter; test the spectral stability of the optical signal using a spectrometer; place the coupling structure in a high and low temperature test chamber and test the coupling loss at different temperatures; fix the coupling structure on a vibration test bench and perform random vibration test 2.

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