A preparation method of a double-layer microstructure array and a multi-primary color LED packaging structure

Abstract

The present invention discloses a method for preparing a double-layer microstructure array. This method uses microdroplets formed by active cooling as a template for imprinting the microstructure array. A double-layer polymer film is used as a sacrificial layer, and the droplet array is introduced through active cooling. The upper and lower double-layer polymer films are introduced, and the microstructures are imprinted on the upper and lower surfaces of the second polymer film simultaneously, thereby achieving a double-layer microstructure array with controllable morphology on both surfaces of the second polymer film. The present invention also discloses a multi-primary color LED package structure, comprising a package substrate, several LED chips of different primary colors, a die-bonding layer, leads, a primary optical lens, a reflective layer, and a polymer film with a double-layer microstructure array. Compared to traditional package structures, the double-layer microstructure array can effectively mix and scatter light of different colors. Its application in multi-primary color LED packages significantly improves the spatial color uniformity (ACU) of the light source.

Description

Technical Field

[0001] The present invention relates to a technology for preparing organic colloid surface microstructures, and in particular to a method for preparing a double-layer microstructure array and a multi-primary color LED packaging structure. Background Art

[0002] In the scheme of obtaining white light illumination by mixing multi-primary LEDs, the differences in the spatial distribution of multi-primary LED chips will cause the light patterns of LED chips of different colors to not match, which in turn causes the light emitted by the LED module to exhibit different correlated color temperatures (CCT) at different viewing angles. In other words, multi-primary LED modules usually have the problem of poor spatial color uniformity, which will greatly reduce the quality of the light source and user experience, and also greatly limit its application expansion.

[0003] In traditional phosphor-converted LEDs, the scattering of phosphors can effectively improve the spatial color uniformity of the light source. However, multi-primary color LEDs usually use transparent packaging, and doping with micro-nano particles to achieve mixed light is usually an effective light color mixing solution. This solution uses the scattering effect of micro-nano particles on the light emitted by the LED to change the propagation direction of the light, so that the light emitted by LED chips of different colors is fully mixed, and ultimately improves the spatial color uniformity of the LED light source. However, there will be a certain amount of backscattering caused by micro-nano scattering particles. Part of the backscattered light is absorbed by the device and cannot be emitted, which ultimately leads to a decrease in the light efficiency of the LED light source.

[0004] Fabricating scattering structures (e.g., microstructure arrays) on the surface of encapsulating colloids is an effective method for improving the spatial color uniformity of multi-primary LED light sources. Numerous methods for fabricating microstructure arrays have been studied. Currently, the most common method for fabricating microstructure arrays on encapsulating colloids is the imprinting method, which generally involves mold fabrication and compression molding. However, the mold fabrication process relies on complex and expensive photolithography techniques, resulting in complex and costly processing. This complexity and cost are particularly significant when fabricating non-standard single-layer microstructure arrays. Droplet imprinting technology, a common moldless processing technique, has garnered widespread attention. Depending on the method used to obtain the droplet array, this technology primarily includes droplet printing and breathing patterning (BF). Droplet printing utilizes direct writing or laser pulse induction techniques to prepare a droplet template, which is then imprinted onto the surface of a polymer film. However, this method still suffers from low efficiency and high cost. In the breathing patterning method, a solid polymer is dissolved in a volatile solvent. The volatile solvent evaporates quickly, lowering the surface temperature of the solution and causing water vapor in the air to condense into water droplets on the surface of the solution. When the solvent is completely evaporated, a polymer film containing a microstructure array is obtained. However, the surface temperature of the solute polymer is difficult to control during the solvent evaporation process because it changes the physical properties of the polymer, making the preparation process non-isothermal and non-equilibrium. In addition, the evaporating solvents commonly used in the breathing patterning method are toxic, such as chloroform and carbon disulfide. These shortcomings limit the application of the breathing patterning method in the preparation of microstructure arrays. Therefore, it remains a huge challenge to develop a microlens array preparation process with simple process, low cost, and flexible and controllable morphology.

[0005] Invention patent CN107188114B proposes a surface microstructure preparation method based on active cooling droplet condensation, which directly prepares a microstructure array on the surface of a UV-cured polymer through active cooling technology. However, since multi-primary color LEDs contain chips of multiple wavelengths, the spatial distribution of chips of different colors varies greatly, resulting in poor spatial color uniformity, which places higher requirements on light mixing. The scattering performance of the single-layer microstructure prepared by the above method is not able to meet the actual application requirements in terms of improving color uniformity. The strong scattering effect of the double-layer microstructure array can effectively mix the different colors of transmitted light. Therefore, it is proposed to use a double-layer microstructure in multi-primary color LED packaging, which is expected to achieve a significant improvement in the spatial color uniformity of the light source.

[0006] In summary, how to achieve low-cost, simple-process double-layer microstructure preparation technology and apply it to multi-primary color LED packaging to achieve improved spatial color uniformity remains a challenge. Summary of the Invention

[0007] In view of the problem that the current traditional surface microstructure preparation technology cannot realize the preparation of double-layer microstructures, the purpose of the present invention is to provide a preparation method of a double-layer microstructure array and a multi-primary color LED packaging structure.

[0008] The first objective of the present invention is to provide a method for preparing a double-layer microstructure array. This method uses microdroplets formed by active refrigeration droplet condensation self-assembly technology as a template for imprinting the microstructure array. A double-layer polymer material is used as a sacrificial layer instead of air, transforming the three-phase interface from polymer-microdroplet-air to polymer-microdroplet-sacrificial layer. Simultaneously, microstructures are imprinted on the upper and lower surfaces of a second polymer film, ultimately yielding a double-layer microstructure array with controllable morphology on both surfaces of the second polymer film. This method features a simple process and can be used to control temperature, refrigeration time, ambient humidity, and other conditions to produce double-layer microstructure arrays with varying morphologies.

[0009] A second object of the present invention is to provide a double-layer microstructure array.

[0010] A third object of the present invention is to provide a multi-primary LED package structure. This multi-primary LED package structure utilizes a highly transparent polymer layer provided with a double-layer microstructure array to address the problem of poor light mixing in multi-primary LED packages and improve the spatial color uniformity of the multi-primary LED package structure.

[0011] The first object of the present invention is achieved in this way:

[0012] A method for preparing a double-layer microstructure array, characterized by comprising the following steps:

[0013] A. preparing a first polymer film on a surface of a first substrate, and placing the first substrate on a temperature-controlled platform;

[0014] B. placing the temperature control platform in a closed environment control box with a constant temperature and humidity and a steam atmosphere, wherein the temperature control platform adjusts the temperature of the first polymer film to be lower than the ambient temperature in the closed environment control box, and the steam in the closed environment control box forms a first droplet array on the surface of the first polymer film;

[0015] C. arranging a dam device on the first substrate, preparing a second polymer film on the surface of the first polymer film, and obtaining a three-phase interface of the first polymer film-the first droplet array-the second polymer film;

[0016] D. adjusting the temperature of the second polymer film to a temperature lower than the ambient temperature in the closed environmental control box through the temperature control platform, so that the vapor in the closed environmental control box forms a second droplet array on the upper surface of the second polymer film;

[0017] E. preparing a third polymer film on the surface of the second substrate, and covering the third polymer film on the second substrate on the surface of the second polymer film having the second droplet array;

[0018] F. Stabilizing to a three-phase equilibrium state of a second polymer film, a second droplet array, and a third polymer film, and curing the second polymer film;

[0019] G. Peeling off the first substrate and the second substrate, removing the first droplet array, the second droplet array, the first polymer film and the third polymer film, and forming a double-layer microstructure array on the upper and lower surfaces of the second polymer film.

[0020] Furthermore, the first substrate and the second substrate materials described in steps A and E are one of glass, silicone, polystyrene, polycarbonate or polymethyl methacrylate high-transmittance materials; the preparation method of the first polymer film and the third polymer film in steps A and E is spin coating, and the first polymer film and the third polymer film are planar films with uniform thickness distribution.

[0021] Furthermore, the temperature control platform is a semiconductor refrigerator; the control range of the ambient temperature of the closed environment control box described in steps B and D is -20-70°C; the cooling temperature of the temperature control platform is 5-40°C lower than the ambient temperature; the concentration range of the vapor atmosphere in the closed environment control box described in steps B and D is 10-90%, and the vapor atmosphere is one of water, methanol, ethanol, ethylene glycol or glycerol or one of a mixed solution; the droplet condensation time in steps C and D is 15s-30min, and the droplet diameter of the first droplet array and the second droplet array is 0.5-100μm.

[0022] Furthermore, the second polymer film is a UV-curable polymer, the first polymer film and the third polymer film are non-UV-curable polymers, the curing method in step F is UV curing, and the curing time is 1-30 minutes; or the second polymer film is a heat-curable polymer, the first polymer film and the third polymer film are non-heat-curable polymers, the curing method in step F is heat curing, and the curing time is 10-300 minutes.

[0023] Furthermore, the materials of the first polymer film and the third polymer film are liquid polymers at room temperature and pressure; the first polymer film is doped with high thermal conductivity nanoparticles; the second polymer film is a high light transmittance material with a transmittance of >99% and a refractive index of 1.5-1.8; the second polymer film is doped with transparent high thermal conductivity nanoparticles, and the refractive index of the high thermal conductivity nanoparticles is the same as that of the second polymer film.

[0024] Furthermore, in step C, the central area of ​​the dam device is hollowed out, and the geometric relationship between the height h of the dam device and the thickness d1 of the first polymer film and the thickness d2 of the second polymer film is: h≥d1+d2, and the thickness d2 of the second polymer film is 0.05-3mm; the cone angle α of the dam device is equal to the contact angle of the second polymer film on the inner wall of the dam device, and the second polymer film forms a film of uniform thickness inside the dam.

[0025] Furthermore, in step E, the second substrate is limited by the plane on the top of the dam device; and in step G, the size of the double-layer microstructure array is 0.5-100 μm.

[0026] This invention uses active cooling at the interfaces between a second polymer film and a double-layer sacrificial polymer layer to induce condensation of water droplets. The morphology of the double-layer microstructure array is then controlled by controlling parameters such as temperature and time. Ultimately, a morphologically controllable double-layer microstructure array is fabricated on both surfaces of the second polymer film. Using this method as the encapsulation layer of a multi-primary-color LED device significantly improves its optical performance.

[0027] The second object of the present invention is achieved in this way:

[0028] A double-layer microstructure array prepared according to the above-mentioned preparation method of the double-layer microstructure array.

[0029] The third object of the present invention is achieved in this way:

[0030] A multi-primary color LED packaging structure comprises a packaging substrate, a plurality of LED chips of different primary colors, a solid crystal layer, leads, a primary optical lens, a reflective layer and a polymer film with a double-layer microstructure array provided by the invention.

[0031] Furthermore, a primary optical lens is mounted on a packaging substrate, and a number of LED chips, a substrate, a solid crystal layer, and leads are sealed on the substrate; the reflective layer is mounted on the surface of the packaging substrate, and on the outside of the primary optical lens, the polymer film with a double-layer microstructure array is mounted on the upper surface of the reflective layer; the LED packaging structure includes ceramic packaging, chip-on-board, system packaging, and silicon-based packaging; the primary optical lens is a spherical cap lens, and the material of the primary optical lens includes silicone, epoxy resin, and polyurethane; the reflectivity of the reflective layer is greater than 95%, and it adopts the form of diffuse reflection or mirror reflection; the height of the reflective layer is H1, the bottom diameter of the reflective layer is D1, the height of the primary optical lens is H2, and the diameter of the primary optical lens is D2, H1>H2, D1>D2.

[0032] Compared with the prior art, the technical solution proposed by the present invention has the following advantages:

[0033] 1. The method for preparing a double-layer microstructure array proposed in the present invention uses microdroplets formed by active cooling as a template for imprinting the microstructure array. By using a double-layer polymer as a sacrificial layer, the droplet array is introduced through active cooling, and the upper and lower double-layer polymer films are introduced to simultaneously imprint the microstructures on the upper and lower surfaces of the second polymer film, thereby achieving a double-layer microstructure array with controllable morphology on both surfaces of the second polymer film. The method for preparing a double-layer microstructure array proposed in the present invention is low-cost, and the diameter and spacing of the resulting microstructures can be adjusted by the coagulation time and cooling temperature. This solves the problem that traditional photolithography and mold imprinting methods cannot produce microstructure arrays on both upper and lower polymer surfaces in one go.

[0034] 2. In the preparation method of the double-layer microstructure proposed in the present invention, the thermal conductivity is improved by doping the first polymer film and the second polymer film with nanoparticles with high thermal conductivity. A dam device with a certain internal cone angle is provided on the first substrate. The cone angle of the dam is equal to the contact angle of the second polymer film on the inner wall of the dam. After the second polymer film is added to the dam device, a second polymer film of uniform thickness will be formed inside the dam. At the same time, due to the effect of the top plane of the dam, the second substrate is limited, thereby preventing deformation of the second polymer film caused by the gravity of the second substrate.

[0035] 3. The multi-primary color LED packaging structure proposed in the present invention introduces a packaging layer with a double-layer microstructure array. Through the strong scattering ability of the double-layer microstructure array, the probability of different colors of light propagating in all directions is increased, so that the different colors of light emitted from the multi-primary color LED packaging module are better matched and more fully mixed, significantly improving spatial color uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Flowchart of the method for preparing the double-layer microstructure array according to Example 1 of the present invention.

[0037] Figure 2 This is a structural view of the multi-primary color LED package of the present invention.

[0038] Figure 3 This is a schematic diagram of the arrangement of the lamp bead chips in the multi-primary color LED packaging structure of the present invention.

[0039] Figure 4 SEM morphology images of the upper surface of the double-layer microstructure array prepared with different condensation times: (a) average diameter and spacing of the microstructure array with condensation time of 15s, (b) condensation time of 25s, and (c) condensation time of 45s.

[0040] Figure 5SEM morphologies of the lower surface of the double-layer microstructure array prepared with different condensation times: (a) average diameter and spacing of the microstructure array with condensation time of 15s, (b) condensation time of 25s, and (c) condensation time of 45s.

[0041] Figure 6 Structural parameters of (a) the upper surface and (b) the lower surface with different coagulation times.

[0042] Figure 7 Figure 2 shows the spatial color temperature distribution of multi-primary color LED package structures: (a) blank multi-primary color LED package module, (b) multi-primary color LED package module with only a mirror reflective layer, (c) multi-primary color LED package structure with both a mirror reflective layer and a single-layer microstructure array, and (d) multi-primary color LED package structure with both a mirror reflective layer and a double-layer microstructure array.

[0043] Figure 8 Spatial color temperature distribution diagram of the multi-primary color LED package structure corresponding to the double-layer microstructure array prepared with different condensation times: (a) condensation time is 15s, (b) condensation time is 25s, (c) condensation time is 45s, and (d) the maximum correlated color temperature deviation of samples with different condensation times.

[0044] Figure 9 This is a flow chart of the method for preparing the double-layer microstructure array of Example 6 of the present invention. DETAILED DESCRIPTION

[0045] The present invention will be further described below with reference to the embodiments and accompanying drawings. However, the following embodiments are only illustrative, and the protection scope of the present invention is not limited by these embodiments. Example 1

[0046] A method for preparing a double-layer microstructure array, characterized in that: Figure 1 As shown, the following steps are included:

[0047] A. Prepare a semiconductor cooler 1 and a first substrate 2. First substrate 2 is made of glass. Spin-coat a layer of polymer (OE6636, Dow Corning, USA) onto the surface of first substrate 2 using a spin coating method. A first polymer film 3 with a uniform thickness is formed on the surface of first substrate 2. First substrate 2 is then placed on semiconductor cooler 1. First polymer film 3 is doped with high-thermal-conductivity nanoparticles of aluminum nitride to increase thermal conductivity and enhance the condensation of active cooling droplets. The thickness d1 of first polymer film 3 is 0.5 mm.

[0048] B. Place the semiconductor refrigerator 1 and the first substrate 2 in a closed environment control box 10 with a constant temperature and humidity and a vapor atmosphere. Use the semiconductor refrigerator 1 to actively cool the first substrate 2, so that the surface temperature of the first polymer film 3 is lower than the temperature in the closed environment control box 10, thereby causing the vapor in the closed environment control box 10 to nucleate and condense into droplets on the surface of the first polymer film 3. Over time, the droplets on the surface of the first polymer film 3 gradually grow and self-assemble into an ordered droplet array. Due to surface tension, some of the droplets enter the interior of the first polymer film 3 and self-assemble into evenly distributed droplets on the upper surface of the first polymer film 3, resulting in a first droplet array 4. The temperature in the closed environment control box 10 is 25°C, the relative humidity is 70%, the vapor atmosphere is water vapor, the cooling temperature of the semiconductor refrigerator 1 is 10°C, and the condensation time is 15 seconds.

[0049] C. A dam device 5 with a height of h = 1.5 mm is placed at the edge of the first substrate 2. A layer of UV polymer (NOA61, Norland, USA) is then coated on the first polymer film 3 forming the first droplet array 4 to form a second polymer film 6, resulting in a three-phase interface of first polymer film 3 - first droplet array 4 - second polymer film 6. The second polymer film 6 is immiscible with both the first polymer film 3 and the first droplet array 4. The second polymer film 6 is a highly transparent material with a transmittance of >99% and a refractive index of 1.52. Transparent, high-thermal-conductivity nanoparticles of silica are doped into the second polymer film 6 to increase its thermal conductivity and enhance the active cooling droplet condensation effect. The high-thermal-conductivity nanoparticles of silica and the second polymer film 6 have the same refractive index, preventing backscattering and degradation of optical performance. The thickness d2 of the second polymer film 6 is 1 mm. The dam device 5 is a unique structure with a hollowed-out center. The geometric relationship between the height h of the dam device 5 and the thickness d1 of the first polymer film 3 and the thickness d2 of the second polymer film 6 is h ≥ d1 + d2. The dam device 5 is made of acrylic. Because the contact angle of the second polymer film 6 on the acrylic surface is 12°, the cone angle α of the dam device 5 is set to 12°. This cone angle α is equal to the contact angle of the second polymer film 6 on the inner wall of the dam device 5, forming a uniform film inside the dam device 5.

[0050] D. Similar to step B, semiconductor cooler 1 is used to actively cool first substrate 2. Through heat conduction, the temperature of the upper surface of second polymer film 6 is lower than the temperature within sealed environmental control box 10, causing vapor within sealed environmental control box 10 to nucleate and condense on the upper surface of second polymer film 6. After a certain condensation time, the droplets on the upper surface of second polymer film 6 gradually grow and self-assemble into an orderly and evenly distributed droplet array. Due to surface tension, some droplets enter the interior of second polymer film 6, forming a second droplet array 7 on the upper surface of second polymer film 6. The cooling temperature of semiconductor cooler 1 is 10°C, and the condensation time is 15 seconds.

[0051] E. Prepare a second substrate 9 made of glass. Spin-coat a layer of polymer (OE6636, Dow Corning, USA) on the surface of second substrate 9 to form a third polymer film 8 of uniform thickness on second substrate 9. Place second substrate 9 with third polymer film 8 on the second polymer film 6, which has the second droplet array 7 formed on its upper surface. Second substrate 9 is positioned by the top surface of the dam device 5 to prevent deformation of the second polymer film 6 due to gravity. Third polymer film 8 is immiscible with the second polymer film 6 and the second droplet array 7. The thickness of third polymer film 8 is 0.5 mm.

[0052] F. After stabilization for a certain period of time, when the third polymer film 8, the second droplet array 7, and the second polymer film 6 reach a three-phase equilibrium state, the second polymer film 6 is irradiated with an ultraviolet lamp to form a microstructure array on the lower and upper surfaces of the second polymer film 6 using the first droplet array 4 and the second droplet array 7 as templates. The peak wavelength of the ultraviolet lamp is 385 nm, and the output light power density is 1.5 mW / cm 2 .

[0053] G. Peel off the first substrate 2 and the second substrate 9, and use acetone and deionized water to remove the first polymer film 3, the third polymer film 8, the first droplet array 4, and the second droplet array 7. The cleaning time is 60 seconds and 30 seconds, respectively. A dense double-layer microstructure array 11 is formed on the upper and lower surfaces of the solidified second polymer film 6.

[0054] By the above-mentioned double-layer microstructure array preparation method, the first droplet array 4 and the second droplet array 7 are prepared in a closed environmental control box 10 at an ambient temperature of 25°C, an ambient relative humidity of 70%, a temperature control platform cooling temperature of 10°C, and a condensation time of 15 seconds, thereby obtaining the double-layer microstructure array prepared in this embodiment. The SEM morphology of the double-layer microstructure array 11 prepared in this embodiment is shown in FIG. Figure 4 (a) and Figure 5As shown in (a), the width D1, average spacing L1, and average depth A1 of the upper surface microstructure array of the double-layer microstructure array 11 are 4.17±0.36, 5.49±0.28, and 2.15±0.24 μm, respectively. The width D2, average spacing L2, and average depth A2 of the lower surface microstructure array of the double-layer microstructure array 11 are 4.58±0.39, 6.14±0.27, and 2.51±0.21 μm, respectively. For the prepared double-layer microstructure array 11, the aspect ratios of the microstructure arrays on the upper and lower surfaces are 1.82 and 1.93, respectively.

[0055] This embodiment also provides a multi-primary color LED packaging structure, including the double-layer microstructure array prepared above.

[0056] Multi-primary color LED packaging structure, such as Figure 2 As shown, the device comprises a packaging substrate 101, several LED chips 102 of different primary colors, a bonding layer 103, leads 104, a primary optical lens 105, and a reflective layer 106. Several LED chips 102 are mechanically connected to the packaging substrate 101 via the bonding layer 103. Each LED chip 102 is electrically conductive to the packaging substrate 101 via the leads 104. The primary optical lens 105 seals the LED chips 102 on the packaging substrate 101. The reflective layer 106 is mounted on the surface of the packaging substrate 101. Outside the primary optical lens 105, a second polymer film 6 having a double-layer microstructure array 11 is mounted on the upper surface of the reflective layer 106. The double-layer microstructure array 11 is obtained using the preparation method of a double-layer microstructure array in this embodiment.

[0057] Multi-color LED package structure lamp bead chip arrangement as follows Figure 3 shown.

[0058] Among them, the LED chips 102 of different primary colors include several types of red LED chips, orange LED chips, yellow LED chips, green LED chips, cyan LED chips, and blue LED chips. The peak wavelength range of the red LED chip is 615nm~635nm, the peak wavelength range of the orange LED chip is 590nm~610nm, the peak wavelength range of the yellow LED chip is 560nm~580nm, the peak wavelength range of the green LED chip is 510nm~530nm, the peak wavelength range of the cyan LED chip is 480nm~500nm, and the peak wavelength range of the blue LED chip is 445nm~465nm. The LED packaging structure is not limited to ceramic packaging, chip-on-board, system packaging and silicon-based packaging.

[0059] The primary optical lens 105 is a spherical cap lens made of silicone (OE6636, Dow Corning, USA), with a light transmittance of 99% and a refractive index of 1.54. The reflective layer 106 adopts a diffuse reflection form or a mirror reflection form, with a reflectivity greater than 95%. The geometric relationship between the height H1 of the reflective layer 106, the bottom diameter D1 of the reflective layer 106, the height H2 of the primary optical lens 105, and the diameter D2 of the primary optical lens 105 is H1>H2, and D1>D2. Example 2

[0060] The preparation method of the double-layer microstructure array of Example 2 is basically the same as that of Example 1, except that:

[0061] The coagulation time in step C is different from that in step D, and the coagulation time is 25 s.

[0062] The SEM morphology of the double-layer microstructure array 11 prepared in this embodiment is as follows: Figure 4 (b) and Figure 5 As shown in (b), the width D1, average spacing L1, and average depth A1 of the upper surface microstructure array of the double-layer microstructure array 11 are 7.81±1.04, 8.31±0.49, and 4.19±0.34 μm, respectively. The width D2, average spacing L2, and average depth A2 of the lower surface microstructure array of the double-layer microstructure array 11 are 8.01±0.94, 8.48±0.50, and 4.08±0.39 μm, respectively. For the prepared double-layer microstructure array 11, the aspect ratios of the microstructure arrays on the upper and lower surfaces are 1.91 and 1.91, respectively. Example 3

[0063] The preparation method of the double-layer microstructure array of Example 3 is basically the same as that of Example 1, except that:

[0064] The coagulation time in step C is different from that in step D, and the coagulation time is 45 s.

[0065] The SEM morphology of the double-layer microstructure array 11 prepared in this embodiment is as follows: Figure 4 As shown in Figures 5(c) and 5(c), the width D1, average spacing L1, and average depth A1 of the upper surface microstructure array of the double-layer microstructure array 11 are 11.16±1.04, 11.67±0.31, and 5.07±0.54 μm, respectively. The width D2, average spacing L2, and average depth A2 of the lower surface microstructure array of the double-layer microstructure array 11 are 10.79±1.04, 11.56±0.43, and 4.96±0.55 μm, respectively. For the prepared double-layer microstructure array 11, the aspect ratios of the microstructure arrays on the upper and lower surfaces are 2.17 and 2.20, respectively.

[0066] Image Pro software was used to perform data statistics and analysis on the surface and cross-sectional SEM images of a large number of double-layer microstructure arrays 11 prepared at different coagulation times, and the statistical average width and statistical average depth of the upper and lower surfaces of each group of double-layer microstructure array structures were obtained. Figure 6 As shown, the morphology is semicircular. For the double-layer microstructure array 11 with condensation times of 15s, 25s, and 45s, the widths of the microstructure array on the upper surface are 4.17±0.36, 7.81±1.04, and 11.16±1.04 μm, and the depths are 2.15±0.24, 4.19±0.34, and 5.07±0.54 μm; the widths of the microstructure array on the lower surface are 4.58±0.39, 8.01±0.94, and 10.79±1.04 μm, and the depths are 2.51±0.21, 4.08±0.39, and 4.96±0.55 μm. The aspect ratio was used to evaluate changes in cross-sectional profile. For the microstructure arrays of different diameters, the aspect ratios for the upper surface were 1.82, 1.91, and 2.17, respectively, while the aspect ratios for the lower surface were 1.93, 1.91, and 2.20, respectively. This demonstrates that this method achieves a double-layer microstructure array with uniform distribution, consistent morphology, and compact arrangement on both the upper and lower surfaces.

[0067] The effect of different condensation times on the optical properties of the prepared double-layer microstructure array 11 was further studied using a spatial spectrum distribution tester. Spatial color temperature distribution tests were conducted on the multi-primary color LED package module with a double-layer microstructure array 11 obtained with condensation times of 15s, 25s, and 45s, respectively. The test input current was set to 80mA, and the distance between the detector test probe and the multi-primary color LED package module was 1m. The test results are shown in Figure 2. Figure 7 and Figure 8 As shown in the figure, the maximum color temperature deviation of the blank multi-primary color LED package module measured is 1183.9K, the maximum color temperature deviation of the multi-primary color LED package module with only a mirror reflective layer is 3115K, the maximum color temperature deviation of the multi-primary color LED package module with a mirror reflective layer and a single-layer microstructure array is 728.6K, and the maximum color temperature deviation of the multi-primary color LED package module with both a mirror reflective layer and a double-layer microstructure array prepared under three different condensation times is reduced to 211.2K, 165.4K, and 169.9K, respectively. In this embodiment, the average diameter of the single-layer microstructure array is about 8μm. This shows that introducing a microstructure array structure on the surface of a multi-primary color LED package module can significantly improve its spatial color uniformity. The array size of the double-layer microstructure array 11 prepared under different condensation time conditions has little effect on the spatial color uniformity in the multi-primary color LED package module, and the improvement of the spatial color uniformity by the double-layer microstructure array 11 is very stable. Example 4

[0068] A method for preparing a double-layer microstructure array, characterized in that: Figure 1 As shown, the following steps are included:

[0069] A. Prepare a semiconductor cooler 1 and a first substrate 2. First substrate 2 is made of polystyrene. Spin-coat a layer of polymer (EP1026, Resinlab, USA) onto the surface of first substrate 2 to form a first polymer film 3 with a uniform thickness. Place first substrate 2 on semiconductor cooler 1. First polymer film 3 is doped with high-thermal-conductivity nanoparticles of boron nitride to increase thermal conductivity and enhance the condensation of active cooling droplets. The thickness d1 of first polymer film 3 is 1.5 mm.

[0070] B. Place the semiconductor refrigerator 1 and the first substrate 2 in a closed environment control box 10 with a constant temperature and humidity and a vapor atmosphere. Use the semiconductor refrigerator 1 to actively cool the first substrate 2, so that the surface temperature of the first polymer film 3 is lower than the temperature in the closed environment control box 10, thereby causing the vapor in the closed environment control box 10 to nucleate and condense on the surface of the first polymer film 3. Over time, the droplets on the surface of the first polymer film 3 gradually grow and self-assemble into an ordered droplet array. Due to surface tension, some of the droplets enter the interior of the first polymer film 3 and self-assemble into evenly distributed droplets on the upper surface of the first polymer film 3, resulting in a first droplet array 4. The temperature in the closed environment control box 10 is 40°C, the relative humidity is 75%, the vapor atmosphere is a 1:1 mixed solution of water and ethylene glycol, and the cooling temperature of the semiconductor refrigerator 1 is 0°C.

[0071] C. A dam device 5 with a height of h = 4.5 mm was placed at the edge of the first substrate 2. A layer of UV polymer (NOA61, Norland, USA) was then coated on the first polymer film 3 forming the first droplet array 4, forming a second polymer film 6. This resulted in a three-phase interface consisting of the first polymer film 3, the first droplet array 4, and the second polymer film 6. The condensation time was 2 minutes. The second polymer 6 was immiscible with both the first polymer film 3 and the first droplet array 4. The second polymer film 6 was made of a highly transparent material with a transmittance of >99% and a refractive index of 1.52. Transparent, high-thermal-conductivity nanoparticle silica was doped into the second polymer film 6 to increase its thermal conductivity and enhance the active cooling droplet condensation effect. The high-thermal-conductivity nanoparticle silica and the second polymer film 6 had the same refractive index, preventing backscattering and degradation of optical performance. The thickness d2 of the second polymer film 6 was 3 mm. The dam device 5 is a specific structure with a hollowed-out central area. The geometric relationship between the height h of the dam device 5 and the thickness d1 of the first polymer film 3 and the thickness d2 of the second polymer film 6 is h≥d1+d2. The material of the dam device 5 is PCT plastic. Since the contact angle of the second polymer film 6 on the PCT plastic surface is 19°, the cone angle α of the dam device 5 is set to 19°. The cone angle α of the dam device 5 is equal to the contact angle of the second polymer film 6 on the inner wall of the dam device 5, and the second polymer film 6 forms a film of uniform thickness inside the dam device 5.

[0072] D. Similar to step B, the first substrate 2 is actively cooled using a semiconductor cooler 1. Through heat conduction, the temperature of the upper surface of the second polymer film 6 is lower than the temperature within the sealed environmental control box 10. This allows the vapor within the sealed environmental control box 10 to nucleate and condense on the upper surface of the second polymer film 6. After a certain condensation time, the droplets on the upper surface of the second polymer film 6 gradually grow and self-assemble into an orderly and evenly distributed droplet array. Due to surface tension, some of the droplets enter the interior of the second polymer film 6, forming a second droplet array 7 on the upper surface of the polymer 6. The cooling temperature of the semiconductor cooler 1 is 0°C, and the condensation time is 2 minutes.

[0073] E. Prepare a second substrate 9 made of polystyrene. Spin-coat a layer of polymer (EP1026, Resinlab, USA) onto the surface of second substrate 9 to form a third polymer film 8 of uniform thickness. Place the prepared second substrate 9 onto the second polymer film 6 with the second droplet array 7 formed on its upper surface. The second substrate 9 is positioned by the top surface of the dam device 5 to prevent deformation of the second polymer film 6 due to gravity. The third polymer film 8 is immiscible with the second polymer film 6 and the second droplet array 7 and has a thickness of 1.5 mm.

[0074] F. After stabilization for a certain period of time, when the third polymer film 8, the second droplet array 7, and the second polymer film 6 reach a three-phase equilibrium state, the second polymer film 6 is irradiated with an ultraviolet lamp to form a microstructure array on the surface of the second polymer film 6 using the first droplet array 4 and the second droplet array 7 as templates. The peak wavelength of the ultraviolet lamp is 385 nm, and the output light power density is 1.5 mW / cm 2 .

[0075] G. Peel off the first substrate 2 and the second substrate 9, and use acetone and deionized water to remove the first polymer film 3, the third polymer film 8, the first droplet array 4, and the second droplet array 7. The cleaning time is 60 seconds and 30 seconds, respectively. A dense double-layer microstructure array 11 is formed on the upper and lower surfaces of the solidified second polymer film 6.

[0076] A double-layer microstructure array prepared by the double-layer microstructure array preparation method.

[0077] This embodiment also provides a multi-primary color LED packaging structure, including the double-layer microstructure array prepared above.

[0078] Multi-primary color LED packaging structure, such as Figure 2 and Figure 3 As shown, the device comprises a packaging substrate 101, several LED chips 102 of different primary colors, a bonding layer 103, leads 104, a primary optical lens 105, and a reflective layer 106. Several LED chips 102 are mechanically connected to the packaging substrate 101 via the bonding layer 103. Each LED chip 102 is electrically conductive to the packaging substrate 101 via the leads 104. The primary optical lens 105 seals the LED chips 102 on the packaging substrate 101. The reflective layer 106 is mounted on the surface of the packaging substrate 101. Outside the primary optical lens 105, a second polymer film 6 having a double-layer microstructure array 11 is mounted on the upper surface of the reflective layer 106. The double-layer microstructure array 11 is obtained using the preparation method of a double-layer microstructure array in this embodiment.

[0079] Among them, the LED chips 102 of different primary colors include a blue light LED chip with a main wavelength of 455 nm, a cyan LED chip with a main wavelength of 490 nm, a green light LED chip with a main wavelength of 520 nm, a yellow light LED chip with a main wavelength of 560 nm, and a red light LED chip with a main wavelength of 620 nm. The LED packaging structure is not limited to ceramic packaging, chip-on-board, system packaging, and silicon-based packaging.

[0080] The primary optical lens 105 is a spherical cap lens made of silicone (OE6636, Dow Corning, USA), with a light transmittance of 99% and a refractive index of 1.54. The reflective layer 106 adopts a diffuse reflection form or a mirror reflection form, with a reflectivity greater than 95%. The geometric relationship between the height H1 of the reflective layer 106, the bottom diameter D1 of the reflective layer 106, the height H2 of the primary optical lens 105, and the diameter D2 of the primary optical lens 105 is H1>H2, and D1>D2. Example 5

[0081] The preparation methods of the double-layer microstructure arrays of Example 5 and Example 4 are basically the same, except that:

[0082] The cooling temperature of the semiconductor refrigerator 1 is different from the ambient temperature and vapor atmosphere in the closed environmental control box 10: in steps B and D, the temperature in the closed environmental control box 10 is 15°C, the relative humidity of the environment is 90%, the vapor atmosphere is a 1:1 mixed solution vapor of water and propylene glycol, the cooling temperature of the semiconductor refrigerator 1 is -5°C, and the condensation time is 3 minutes.

[0083] The multi-primary color LED package module of Example 5 is basically the same as that of Example 4, except that the double-layer microstructure array 11 of the multi-primary color LED package module in this embodiment is prepared by the preparation method of the double-layer microstructure array in this embodiment. Example 6

[0084] A method for preparing a double-layer microstructure array, characterized in that: Figure 9 As shown, the following steps are included:

[0085] A. Prepare a semiconductor cooler 1 and a first substrate 2. First substrate 2 is made of glass. Spin-coat a layer of non-thermosetting polymer (NOA61, NORLAND, USA) onto the surface of first substrate 2 to form a uniformly distributed first polymer film 3. Place first substrate 2 on semiconductor cooler 1. First polymer film 3 is doped with high-thermal-conductivity graphene nanoparticles to increase thermal conductivity and enhance the condensation of active cooling droplets. The thickness d1 of first polymer film 3 is 1 mm.

[0086] B. Actively cool the first substrate 2 using a semiconductor cooler 1, lowering the surface temperature of the first polymer film 3 below the ambient temperature. This allows water vapor in the air to nucleate and condense on the surface of the first polymer film 3. Over time, the droplets on the surface of the first polymer film 3 gradually grow and self-assemble into an ordered droplet array. Due to surface tension, some of the droplets enter the interior of the first polymer film 3 and self-assemble into evenly distributed droplets on the upper surface of the first polymer film 3, forming a first droplet array 4. The ambient temperature is 25°C, the relative humidity is 50%, and the cooling temperature of the semiconductor cooler 1 is 0°C.

[0087] C. A dam 5 with a height of h = 3 mm was placed at the edge of the first substrate 2. A layer of 99% transmittance thermosetting polymer silicone (OE6636, Dow Corning, USA) was then applied to the first polymer film 3 forming the first droplet array 4, forming a second polymer film 6. This resulted in a three-phase interface consisting of the first polymer film 3, the first droplet array 4, and the second polymer film 6. The condensation time was 5 minutes. The second polymer film 6 was immiscible with both the first polymer film 3 and the droplets 4. The second polymer film 6 was made of a highly transparent material with a refractive index of 1.54. Transparent, high-thermal-conductivity nanoparticles of aluminum oxide were doped into the second polymer film 6 to increase its thermal conductivity and enhance the active cooling droplet condensation effect. The high-thermal-conductivity nanoparticles of aluminum oxide and the second polymer film 6 had the same refractive index, preventing backscattering and degradation of optical performance. The thickness d2 of the second polymer film 6 was 2 mm. The dam device 5 is a specific structure with a hollowed-out central area. The geometric relationship between the height h of the dam device 5 and the thickness d1 of the first polymer film 3 and the thickness d2 of the second polymer film 6 is h≥d1+d2. The material of the dam device 5 is a silicon wafer. Since the contact angle of the second polymer film 6 on the surface of the silicon wafer is 17°, the cone angle α of the dam device 5 is set to 17°. The cone angle α of the dam device 5 is equal to the contact angle of the second polymer film 6 on the inner wall of the dam device 5, and the second polymer film 6 forms a film of uniform thickness inside the dam device 5.

[0088] D. Similar to step B, semiconductor cooler 1 is used to actively cool first substrate 2. Heat conduction lowers the upper surface temperature of second polymer film 6 below the ambient temperature, causing water vapor in the air to nucleate and condense on the upper surface of second polymer film 6. After a certain condensation time, the droplets on the upper surface of second polymer film 6 gradually grow and self-assemble into an orderly and evenly distributed droplet array. Due to surface tension, some droplets enter the interior of second polymer film 6, forming a second droplet array 7 on the upper surface of polymer 6. The cooling temperature of semiconductor cooler 1 is 0°C, and the condensation time is 5 minutes.

[0089] E. Prepare a second substrate 9 made of glass. Spin-coat a layer of non-thermosetting polymer (NOA61, NORLAND, USA) on the surface of substrate 9 using a spin coating method. A third polymer film 8 of uniform thickness is formed on second substrate 9. Place second substrate 9 with third polymer film 8 on the second polymer film 6, which has the second droplet array 7 formed on its upper surface. Second substrate 9 is restrained by the top surface of dam device 5 to prevent deformation of second polymer film 6 caused by gravity. Third polymer film 8 is immiscible with second polymer film 6 and second droplet array 7 and has a thickness of 1 mm.

[0090] F. After stabilization for a certain period of time, when the third polymer film 8, the second droplet array 7, and the second polymer film 6 reach a three-phase equilibrium, the device is placed on a hot plate 12 to completely cure the second polymer film 6. A microstructure array, using the first droplet array 4 and the second droplet array 7 as templates, is formed on the surface of the second polymer film 6. The curing temperature of the hot plate 12 is 80°C, and the curing time is 90 minutes.

[0091] G. Peel off the first substrate 2 and the second substrate 9, remove the first polymer film 3, the third polymer film 8, the first droplet array 4 and the second droplet array 7, and form a dense double-layer microstructure array 11 corresponding to the droplet array on the upper and lower surfaces of the solidified second polymer film 6.

[0092] A double-layer microstructure array prepared by the double-layer microstructure array preparation method.

[0093] The multi-primary color LED package module of Example 6 is basically the same as that of Example 4, except that the double-layer microstructure array 11 of the multi-primary color LED package module in this embodiment is prepared by the preparation method of the double-layer microstructure array in this embodiment.

Claims

1. A method for preparing a double-layer microstructure array, characterized in that: The following steps are involved: A. preparing a first polymer film on a surface of a first substrate, and placing the first substrate on a temperature-controlled platform; B. placing the temperature control platform in a closed environment control box with a constant temperature and humidity and a steam atmosphere, wherein the temperature control platform adjusts the temperature of the first polymer film to be lower than the ambient temperature in the closed environment control box, and the steam in the closed environment control box forms a first droplet array on the surface of the first polymer film; C. Disposing a dam device on a first substrate, and preparing a second polymer film on the surface of the first polymer film to obtain a three-phase interface of the first polymer film, the first droplet array, and the second polymer film; the central area of ​​the dam device is hollowed out, and the geometric relationship between the height h of the dam device and the thickness d1 of the first polymer film and the thickness d2 of the second polymer film is: h ≥ d1 + d2, and the thickness d2 of the second polymer film is 0.05-3 mm; the cone angle α of the dam device is equal to the contact angle of the second polymer film on the inner wall of the dam device, and the second polymer film forms a film of uniform thickness inside the dam; D. adjusting the temperature of the second polymer film to a temperature lower than the ambient temperature in the closed environmental control box through the temperature control platform, so that the vapor in the closed environmental control box forms a second droplet array on the upper surface of the second polymer film; E. preparing a third polymer film on the surface of the second substrate, and covering the third polymer film on the second substrate on the surface of the second polymer film having the second droplet array; F. Stabilizing to a three-phase equilibrium state of a second polymer film, a second droplet array, and a third polymer film, and curing the second polymer film; G. Peeling off the first substrate and the second substrate, removing the first droplet array, the second droplet array, the first polymer film and the third polymer film, and forming a double-layer microstructure array on the upper and lower surfaces of the second polymer film.

2. The method for preparing a double-layer microstructure array according to claim 1, wherein: The first substrate and the second substrate described in steps A and E are made of one of glass, silicone, polystyrene, polycarbonate or polymethyl methacrylate high-transmittance materials; the first polymer film and the third polymer film in steps A and E are prepared by spin coating, and the first polymer film and the third polymer film are planar films with uniform thickness distribution.

3. The method for preparing a double-layer microstructure array according to claim 1, wherein: The temperature control platform is a semiconductor refrigerator; the control range of the ambient temperature of the closed environment control box described in steps B and D is -20-70°C; the cooling temperature of the temperature control platform is 5-40°C lower than the ambient temperature; the concentration range of the vapor atmosphere in the closed environment control box described in steps B and D is 10-90%, and the vapor atmosphere is one or more of water, methanol, ethanol, ethylene glycol or glycerol; the droplet condensation time described in steps B and D is 15s-30min, and the droplet diameter of the first droplet array and the second droplet array is 0.5-100μm.

4. The method for preparing a double-layer microstructure array according to claim 1, wherein: The second polymer film is a UV-curable polymer, the first polymer film and the third polymer film are non-UV-curable polymers, the curing method in step F is UV curing, and the curing time is 1-30 minutes; or the second polymer film is a heat-curable polymer, the first polymer film and the third polymer film are non-heat-curable polymers, the curing method in step F is heat curing, and the curing time is 10-300 minutes.

5. The method for preparing a double-layer microstructure array according to claim 1, wherein: The materials of the first polymer film and the third polymer film are liquid polymers at room temperature and pressure; the first polymer film is doped with high thermal conductivity nanoparticles; the second polymer film is a high light transmittance material with a transmittance of >99% and a refractive index of 1.5-1.8; the second polymer film is doped with transparent high thermal conductivity nanoparticles, and the refractive index of the transparent high thermal conductivity nanoparticles is the same as the refractive index of the second polymer film.

6. The method for preparing a double-layer microstructure array according to claim 1, wherein: In step E, the second substrate is limited by the plane on the top of the dam device; in step G, the size of the double-layer microstructure array is 0.5-100 μm.

7. A double-layer microstructure array prepared according to the preparation method according to any one of claims 1 to 6.

8. A multi-primary color LED package structure, characterized in that: Comprising the double-layer microstructure array according to claim 7.

9. The multi-primary color LED package structure according to claim 8, characterized in that: include: A packaging substrate, several LED chips of different primary colors, a die-bonding layer, leads, a primary optical lens, a reflective layer, and a polymer film with a double-layer microstructure array, wherein the primary optical lens is mounted on the packaging substrate, and the several LED chips, the die-bonding layer, and the leads are sealed on the packaging substrate; the reflective layer is mounted on the surface of the packaging substrate, and the polymer film with a double-layer microstructure array is mounted on the upper surface of the reflective layer outside the primary optical lens; the primary optical lens is a spherical cap lens; the reflective layer has a reflectivity greater than 95% and adopts diffuse reflection or mirror reflection; the reflective layer has a height of H1, a bottom diameter of D1, a height of H2, and a diameter of D2, where H1>H2 and D1>D2.

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