LED packaging structure, packaging method and packaging module

Abstract

The invention discloses an LED packaging structure, a packaging method and a packaging module, provides a non-rotational-symmetry free-form surface lens structure, breaks through the size limitation of a substrate on a traditional rotational-symmetry lens, realizes a packaging adhesive layer structure adaptive to an extended light source, and adopts a convex structure with a certain height-width ratio. Small-angle light emitting is realized by controlling a light emitting path; the reflection structure is arranged on the substrate, so that direct emission of large-angle light rays is avoided, and large-angle light leakage is reduced; in addition, the invention provides a light mixing layer structure and a preparation process using ion wind, light mixing of a discontinuous light-emitting surface is realized, the problems of electrode imaging and dark areas of an extended light source are effectively eliminated by further combining with a micro-structure array on the surface of a packaging adhesive layer, and uniform light emitting of the structure is realized; the invention further provides a packaging module for the multi-primary-color LED, and spatial mixing of light rays of different colors is enhanced.

Description

Technical Field

[0001] The present invention relates to the field of light emitting diode packaging, and in particular to an LED packaging structure, a packaging method, and a packaging module. Background Art

[0002] With the continuous development of LED technology and the expansion of its application areas, the demand for precise lighting continues to grow. Certain lighting scenarios require highly directional and uniform LED lighting sources. Compared with traditional LED light sources, LED small-angle lamp beads can effectively reduce light loss through their focusing design, improve light utilization, and indirectly enhance the luminous efficiency of LED lamps at the same brightness.

[0003] Currently, the mainstream solution for achieving precise, narrow-angle lighting is to use LED packages paired with secondary lenses or reflectors. However, these are bulky, preventing close arrangement of LED light sources and failing to meet the trend toward miniaturization in some lighting products. Therefore, developing a package structure that delivers narrow-angle illumination, high energy density, and a compact size is crucial.

[0004] In order to improve the energy density, a single large-size chip or multiple chips, that is, an extended light source, is often used and packaged in a single LED lamp bead. In this case, the following problems often exist when achieving small-angle light emission at the packaging level: (1) Large-angle light leakage problem: Small-angle light emission is achieved by controlling the light emission direction through the lens shape, but the constraint ability for large-angle light is limited, and there is a problem of constraint failure leading to large-angle light leakage; (2) Imaging problem of the extended light source: For the extended light source, small-angle light emission is achieved through a single optical lens. For example, when the beam angle is reduced to below 60°, there is a chip imaging problem due to the discontinuity of the luminous surface such as the electrode line blocking the chip surface or the dark area between multiple chips, resulting in dark stripes on the target plane light spot, which seriously affects the uniformity of the light spot; (3) The contradiction between the substrate size limitation and the lens design: Due to the limitation of the substrate size, the lens diameter cannot be infinitely expanded. The existing central axis symmetrical lens (such as hemispherical or parabolic) is difficult to achieve effective constraint on light under limited size, resulting in the inability to further reduce the light emission angle. Summary of the Invention

[0005] In view of this, the embodiments of the present invention provide an LED packaging structure, a packaging method, and a packaging module to solve the problems of large-angle light leakage, uneven light spots caused by imaging phenomena, and conflicts between substrate size limitations and lens design in the prior art when achieving uniform light output at small angles from an extended light source at the packaging level.

[0006] In a first aspect, the present invention provides an LED packaging structure, comprising a substrate, a reflective structure, an LED chip, and an encapsulation layer; the reflective structure is provided with a concave arc surface, the reflective structure is provided on the substrate, and the concave arc surface and the surface of the substrate are enclosed to form a cavity; the LED chip is provided in a light-emitting area in the cavity, and the LED chip is bonded to the substrate; the encapsulation layer fills the cavity and protrudes from the cavity, and covers the LED chip; the encapsulation layer is composed of an upper lens and a lower lens, and the interface between the upper lens and the lower lens is located at the same horizontal plane as the upper surface of the reflective structure; the upper surface of the upper lens The invention relates to a free-form surface having a non-rotational symmetry; the interface between the upper lens and the lower lens is a centrosymmetric plane figure, the centrosymmetric plane figure is composed of a free curve or a combination of a free curve and a line segment; the lower lens includes a light-mixing layer, the light-mixing layer is composed of a microlens array, the light-mixing layer covers the surface of the LED chip, and the relationship between the refractive index n1 of the light-mixing layer and the refractive index n2 of the encapsulation layer is n1>n2; wherein, the relationship between the ratio of the height H of the encapsulation layer to the width characteristic dimension b of the interface is 0.5<H / b≤2; the maximum width characteristic dimension L of the interface is max The relationship between the width characteristic dimension D of the substrate is D<L max <D; the relationship between the width characteristic dimension a of the light emitting area and the width characteristic dimension D of the substrate is 0.2≤a / D≤0.8.

[0007] The present invention adopts a non-rotationally symmetric free-form surface structure on the upper surface of the upper lens through innovative design. Compared with the traditional rotationally symmetric lens, under the same external dimensions, this structure can increase the effective optical surface utilization rate of the free-form surface by more than 10%, significantly improving the optical performance. At the same time, the graphics and maximum width characteristic dimensions of the interface between the upper and lower lenses are limited to ensure that the area of ​​the interface is larger than the area of ​​the inscribed circle of the substrate. This design can effectively increase the volume of the encapsulation glue layer, thereby realizing the regulation of the light type of the extended light source, and can effectively improve light extraction. In addition, a mixing layer is introduced into the LED packaging structure, and the light emitted by the chip is mixed through the mixing layer to achieve continuous light emission from the light-emitting surface of the mixing layer, solving the problem of dark stripes in the target surface light spot caused by the discontinuity of the light-emitting surface, and achieving uniform light emission. The technical solution of the present invention breaks the bottleneck of the traditional rotationally symmetric lens being limited by the substrate size, and successfully designs a raised encapsulation glue layer structure that is compatible with the extended light source. By precisely controlling the light emission path through a non-rotationally symmetric free-form surface lens, a small-angle light emission effect can be achieved, which not only improves the efficiency of the optical system but also meets the high-precision light distribution requirements of specific lighting scenarios.

[0008] Optionally, the relationship between the height h of the reflective structure and the width characteristic dimension b of the interface is b / 2×cot70°≤h≤b / 2×cot50°, and the relationship between the width characteristic dimension d of the reflective structure and the width characteristic dimension D of the substrate is d=D.

[0009] Optionally, the concave curved surface of the reflective structure is mirror reflective, and the reflectivity of the mirror reflective is greater than 95%.

[0010] Optionally, the LED chip is single or multiple; the LED chip is a vertical structure, and the specific structure includes the first electrode of the chip, the substrate, the p-type layer, the quantum well layer, the n-type layer and the second electrode from bottom to top. The side wall of the LED chip is covered with a passivation layer, and the current flows vertically inside the LED chip.

[0011] Optionally, a microstructure array is provided on the top or the entire upper surface of the upper lens; the microstructure units of the microstructure array are one of scales, protrusions, and pyramids, and the characteristic size of the base of the microstructure unit is 10 μm-500 μm.

[0012] In a second aspect, the present invention provides a packaging method for the above-mentioned LED packaging structure, comprising the following steps: S1. Providing a substrate with a reflective structure, wherein the reflective structure has a concave arc surface, and the concave arc surface and the surface of the substrate enclose a cavity; S2. Bonding the LED chip to the light-emitting area in the cavity on the substrate to achieve electrical connection between the LED chip and the substrate; S3. Prepare a light-mixing layer. Place the substrate that has completed step S2 on a hot plate. Apply encapsulation glue on the upper surface of the LED chip and cover the LED chip. Prepare upper and lower electrodes. Apply a high-voltage electric field between the upper and lower electrodes. The encapsulation glue forms a raised microlens array through the generated ion wind. After the microlenses are formed and stabilized, heat and cure them to complete the preparation of the light-mixing layer.

[0013] S4. Through the mold top process, using the lens mold, prepare an encapsulation layer on the substrate that has completed step S3. The encapsulation layer fills the cavity and protrudes from the cavity, and covers the LED chip and the light mixing layer; cure the encapsulation layer to complete the preparation of the encapsulation structure.

[0014] Optionally, in step S4, the surface of the lens mold is provided with a microstructure array, the microstructure units of the microstructure array are one of scales, protrusions, and pyramids, and the base feature size of the microstructure units is 10μm-500μm; the surface finish of the lens mold is in the range of 0.15μm≤Ra≤0.35μm, 0.65μm≤Rz≤12μm.

[0015] In a third aspect, the present invention provides an LED packaging module, comprising four of the above-mentioned LED packaging structures, wherein the four LED packaging structures are rotated 90° in sequence and closely distributed; each packaging structure comprises a plurality of LED chips of different colors.

[0016] In summary, the beneficial effects of the present invention are as follows: 1. The present invention provides a lens structure with a non-rotationally symmetric free-form surface, which breaks through the size limitation of the substrate on traditional rotationally symmetric lenses and realizes a raised packaging glue layer structure adapted to the extended light source. The light emitted at a small angle is controlled by the non-rotationally symmetric free-form surface lens to control the light emission path. A light mixing layer is introduced into the LED packaging structure. The light emitted from the chip is mixed by the light mixing layer, realizing continuous light emission from the light-emitting surface of the light mixing layer, solving the problem of dark stripes in the target surface light spot caused by the discontinuity of the light-emitting surface, and realizing uniform light emission.

[0017] 2. This invention incorporates a reflective structure on the substrate, with its characteristic height and width dimensions meeting a specific ratio. This reflective structure mirrors wide-angle light and directs it toward a narrower angle, resolving wide-angle light leakage issues while simultaneously improving light energy utilization. This invention combines a non-rotationally symmetric free-form lens structure with a reflective structure to achieve narrow-angle light emission from LED packages.

[0018] 3. The present invention sets a microstructure array on the surface of the encapsulation glue layer, so that the light is scattered on the light-emitting surface, solving the problem of extended light source imaging. At the same time, it can play a role in mixing light and color for multi-chip LED packaging, further achieving uniform light output.

[0019] 4. The present invention provides a method for preparing a light-mixing layer microlens array. By applying an electric field to generate an ion wind, the encapsulation adhesive is formed into a raised microlens array, and the encapsulation adhesive is thermally cured to achieve the preparation of a light-mixing layer composed of a microlens array. This aspect has the advantages of simple process and low cost.

[0020] 5. The present invention provides an LED packaging module that improves the color separation of multi-primary colors at small angles. The four packaging structures (containing chips of different colors) are rotated 90° in sequence and arranged closely, promoting the mixing of light of different colors in space and achieving spatial color uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the maximum cross-section of a traditional lens for LED packaging.

[0022] Figure 2 3D schematic diagram of a rotationally symmetric lens that breaks the substrate size limitation.

[0023] Figure 3 3D schematic diagram of a non-rotationally symmetric free-form surface.

[0024] Figure 4 Schematic diagram of small-angle and large-angle light emission when the LED package has a non-reflective structure.

[0025] Figure 5 This is the light distribution curve when the LED package has a non-reflective structure.

[0026] Figure 6 This is the light distribution curve when the LED package has a reflective structure.

[0027] Figure 7 Schematic diagram of the traditional LED chip structure and passivation layer coverage position.

[0028] Figure 8 Schematic diagram of the LED chip structure and passivation layer coverage position used in the present invention.

[0029] Figure 9 This is a schematic front view of the cross section of the LED packaging structure in Example 1 of the present invention.

[0030] Figure 10 Schematic diagram of the interface and LED chip in Example 1 of the present invention.

[0031] Figure 11 This is a schematic diagram of the reflection structure in Example 1 of the present invention.

[0032] Figure 12 This is the simulation result of the light distribution curve of the LED package in Example 1 of the present invention.

[0033] Figure 13 This is a schematic diagram of the principle of preparing the light mixing layer in Example 1 of the present invention.

[0034] Figure 14 This is a schematic diagram of the LED packaging module in Example 1 of the present invention.

[0035] Figure 15 This is a schematic diagram of the central symmetric graphics of the interface in Example 2 of the present invention.

[0036] Figure 16 This is the simulation result of the light distribution curve of the LED package in Example 2 of the present invention.

[0037] Figure 17 This is a schematic diagram of the principle of preparing the light mixing layer in Example 2 of the present invention.

[0038] Figure 18 This is a schematic front view of the cross-section of the LED packaging structure in Example 3 of the present invention.

[0039] Figure 19 This is a schematic diagram of the reflection structure in Example 3 of the present invention.

[0040] Figure 20 This is the simulation result of the light distribution curve of the LED package in Example 3 of the present invention.

[0041] Figure 21 Schematic diagram of the front cross-section of the LED packaging structure in Example 4 of the present invention.

[0042] Figure 22 This is a schematic diagram of the reflection structure in Example 4 of the present invention.

[0043] Figure 23 This is the simulation result of the light distribution curve of the LED package in Example 4 of the present invention. DETAILED DESCRIPTION

[0044] The following will provide a clear and complete description of the concept and technical effects of the present invention in conjunction with the accompanying drawings to fully illustrate the purpose, scheme and effects of the present invention.

[0045] like Figure 1 As shown in the figure, the maximum cross-section of a traditional lens is a circle. Due to the limitation of the substrate size, the diameter of the circle must be smaller than the side length of the substrate, which in turn limits the volume of the lens and the size of the light-emitting surface. In order to break the limitation of the substrate size, as shown in the figure, Figure 2 As shown, the general method is to increase the size of the bottom circle of the rotationally symmetric lens and then cut off the excess lens that exceeds the packaging substrate, while also cutting off part of the effective optical surface.

[0046] The technical solution proposed in the embodiment of the present application can completely preserve the effective optical surface while breaking through the substrate size limitation.

[0047] In a first aspect, the present application provides an LED packaging structure, such as Figure 9 As shown, it includes a substrate 1, a reflective structure 4, an LED chip 2 and an encapsulation layer 3; the reflective structure 4 is provided with a concave arc surface, the reflective structure 4 is provided on the substrate 1, and the concave arc surface and the surface of the substrate 1 enclose a cavity; the LED chip 2 is provided in the light-emitting area of ​​the cavity, and the LED chip 2 is bonded to the substrate 1; the encapsulation layer 3 fills the cavity and protrudes from the cavity, and covers the LED chip 2; the encapsulation layer 3 is composed of an upper lens 31 and a lower lens 32, and the interface between the upper lens 31 and the lower lens 32 is located at the same horizontal plane as the upper surface of the reflective structure 4; the upper surface of the upper lens 31 is a non-rotationally symmetric free-form surface; the interface between the upper lens 31 and the lower lens 32 is a centrosymmetric plane figure, and the centrosymmetric plane figure is composed of free curves or a combination of free curves and line segments; the lower lens 32 includes a light-mixing layer 5, which is composed of a microlens array. The light-mixing layer 5 covers the surface of the LED chip 2, and the relationship between the refractive index n1 of the light-mixing layer 5 and the refractive index n2 of the encapsulation layer 3 is n1>n2. The ratio of the height H of the encapsulation layer 3 to the width characteristic dimension b of the interface is 0.5<H / b≤2; the maximum width characteristic dimension L of the interface is max (like Figure 10 The relationship between the width characteristic dimension D of the substrate 1 is D<L max <D; the relationship between the width characteristic dimension a of the light emitting area and the width characteristic dimension D of the substrate 1 is 0.2≤a / D≤0.8.

[0048] The luminous area of ​​the embodiment of the present application is relatively large on the substrate, and is an extended light source rather than a point light source. Compared with a point light source, the extended light source has problems such as large-angle light leakage, imaging, and uneven light spot when using a single optical lens to emit light at a small angle. The embodiment of the present application adopts a non-rotationally symmetric free-form surface structure on the upper surface of the upper lens, such as Figure 3 As shown, compared with the traditional rotationally symmetric lens, the non-rotationally symmetric free-form surface structure can increase the effective optical surface utilization rate of the free-form surface by more than 10% under the same external dimensions, significantly improving the optical performance. At the same time, the graphics and maximum width characteristic dimensions of the upper and lower lens interfaces are limited to ensure that the area of ​​the interface is larger than the area of ​​the inscribed circle of the substrate. This design can effectively increase the volume of the encapsulation layer, thereby realizing the regulation of the light type of the extended light source. The technical solution of the present invention breaks the bottleneck of the traditional rotationally symmetric lens being limited by the size of the substrate, and successfully designs a raised encapsulation layer structure that is compatible with the extended light source. Through the precise control of the light emission path by the non-rotationally symmetric free-form surface lens, a small-angle light emission effect can be achieved, which not only improves the efficiency of the optical system but also meets the high-precision light distribution requirements of specific lighting scenes. The chip of the present invention is provided with a light-mixing layer on its upper surface. After emitting light from the LED chip, it enters the light-mixing layer. Because the refractive index of the light-mixing layer differs from that of the encapsulation layer, light is refracted as it passes through the microlens array of the light-mixing layer, changing the light propagation path. This shifts the light-emitting surface from discontinuous light emission from the chip surface to continuous light emission from the light-emitting surface of the light-mixing layer. The light-mixing layer covers the surface of the LED chip, achieving light mixing without increasing the area of ​​the light-emitting surface. Furthermore, n1>n2, with light emitting sequentially passing through the LED chip, the light-mixing layer, the encapsulation layer, and then into the air, the refractive indices of these four layers vary in a gradient, further facilitating the efficient extraction of light.

[0049] In some embodiments, the relationship between the height h of the reflective structure 4 and the width characteristic dimension b of the interface is b / 2×cot70°≤h≤b / 2×cot50°, and the relationship between the width characteristic dimension d of the reflective structure 4 and the width characteristic dimension D of the substrate 1 is d=D. Figure 4 As shown, the light emitted at a small angle can be controlled by the surface of the encapsulation layer to control the direction of the light, but the light emitted at a large angle is difficult to be constrained by only passing through the encapsulation surface, such as Figure 5 As shown, there is a problem of large-angle light. Therefore, a reflective structure is added, and the large-angle light is emitted to the reflective structure and then reflected by the mirror surface to be emitted in the direction of small angle (such as Figure 11 As shown in the figure), it avoids direct emission, solves the problem of light leakage at large angles, and improves the utilization rate of light energy. Figure 5As shown in the figure, large-angle light leakage is mainly concentrated in the range of ±50° to ±70°. The height of the reflective structure is limited to b / 2×cot70°≤h≤b / 2×cot50°. The height of the reflective structure should not be less than b / 2×cot70° to prevent large-angle light from being directly emitted. However, the height cannot be too high, as it will cause a large amount of light to be emitted after reflection, resulting in a decrease in light extraction efficiency. Therefore, the height of the reflective structure should be within a reasonable range to achieve the constraint on large-angle light emission, such as Figure 6 As shown in the figure, after adding the reflective structure, the light distribution curve of the LED package significantly reduces the light at large angles.

[0050] In some embodiments, the concave curved surface of the reflective structure 4 is mirror-reflective, with a reflectivity greater than 95%. With mirror reflection, light is reflected according to the rule that the angle of incidence equals the angle of reflection. This allows high-angle light to be reflected by the reflective structure 4 and emitted at a smaller angle, thus achieving control over the high-angle light.

[0051] In some embodiments, the LED chip 2 is a single or multiple LED chips; the LED chip 2 is a vertical structure, and the specific structure includes a chip substrate (first electrode), a p-type layer, a quantum well layer, an n-type layer, and a second electrode from bottom to top. The sidewalls of the LED chip 2 are covered with a passivation layer, and the current flows vertically inside the LED chip. Figure 7 As shown, the passivation layer of the traditional LED chip covers the side walls and the upper surface of the LED chip, and the passivation layer has good insulation performance. However, the passivation layer of the LED chip used in the present invention only covers the side walls of the LED chip, and there is no passivation layer on the upper surface of the LED chip. Figure 8 As shown, the upper surface of the LED chip is conductive, and charges can enter from the upper surface of the LED chip. The second electrode of the LED chip is a patterned electrode on the upper surface of the LED chip, and the first electrode is the lower surface of the LED chip.

[0052] In some embodiments, a microstructure array 311 is provided on the top or the entire upper surface of the upper lens 31; the microstructure units of the microstructure array 311 are one of scales, protrusions, and pyramids, and the characteristic size of the base of the microstructure unit is 10μm-500μm. The surface of the encapsulation layer is provided with a microstructure array, which can change the direction of light emission, alleviate the problem of dark stripes in the light spot at a small angle, and at the same time play a role in mixing light and color for the packaging structure of multiple chips. The imaging problem depends to a certain extent on the curvature of the top of the encapsulation layer, so providing a microstructure array on the top of the encapsulation layer also has the effect of eliminating imaging. At the same time, the size of the microstructure unit is limited to achieve a good balance between light mixing and light extraction by the microstructure.

[0053] In a second aspect, embodiments of the present application provide a packaging method for the above-mentioned LED packaging structure, comprising the following steps: S1. Provide a substrate 1 having a reflective structure 4, wherein the reflective structure 4 has a concave arc surface, and the concave arc surface and the surface of the substrate 1 enclose a cavity; S2, bonding the LED chip 2 to the light-emitting area in the cavity on the substrate 1 to achieve electrical connection between the LED chip 2 and the substrate 1; S3. Prepare the light-mixing layer 5. Place the substrate 1 after completing step S2 on a hot plate. Apply encapsulation glue on the upper surface of the LED chip 2 and cover the LED chip 2. Prepare the upper electrode and the lower electrode. Apply a high-voltage electric field between the upper electrode and the lower electrode. The encapsulation glue is formed into a raised microlens array through the generated ion wind. After the microlens array is formed and stabilized, it is heated and cured to complete the preparation of the light-mixing layer 5.

[0054] S4. Through the mold top process, using the lens mold, prepare the packaging glue layer 3 on the substrate 1 that completes step S3. The packaging glue layer 3 fills the cavity and protrudes from the cavity, and covers the LED chip 2 and the light mixing layer 5; cure the packaging glue layer 3 to complete the preparation of the packaging structure.

[0055] The specific process for preparing the light-mixing layer 5 is as follows: preparing an upper electrode and a lower electrode, where the upper electrode is a needle-tip electrode and the lower electrode is the negative electrode (second electrode) of the LED chip; using a DC power supply to apply a high-voltage electric field between the needle-tip electrode and the LED chip, which have a large difference in curvature, to achieve corona discharge. The gas molecules are ionized to generate charges that move downward under the action of the Coulomb force; the charges first accumulate on the surface of the non-conductive encapsulant, and then the electric field force drives the encapsulant to flow, causing the encapsulant to bulge and form a microlens array. At the same time, the charges are introduced from the upper surface of the LED chip into the LED chip, passing through the n-type layer, quantum well layer, p-type layer and chip substrate in sequence, and then flowing into the external circuit; after the above process stabilizes, the encapsulant is cured by heating on a hot plate while continuously powered, thereby completing the preparation of the light-mixing layer microlens array.

[0056] This preparation method is to use the ion wind generated by applying an electric field to form a raised microlens array on the packaging glue, and thermally cure the packaging glue to achieve the preparation of the microlens array on the surface of the mixed light layer. Compared with the traditional imprinting process for preparing microlens arrays, this method is a non-contact in-situ production method, which avoids damage to the gold wire and has the advantages of simple process and low cost.

[0057] In some embodiments, in step S4, a microstructure array is formed on the surface of the lens mold. The microstructure units of the microstructure array are selected from the group consisting of scales, protrusions, and pyramids. The base feature size of the microstructure units ranges from 10 μm to 500 μm. The surface finish of the lens mold is within the range of 0.15 μm ≤ Ra ≤ 0.35 μm and 0.65 μm ≤ Rz ≤ 12 μm. The lens surface is treated with a graining treatment to provide a certain scattering effect, facilitating light mixing.

[0058] In a third aspect, the present application provides an LED packaging module, comprising four of the above-mentioned LED packaging structures, which are rotated 90° in sequence and closely distributed; each packaging structure comprises multiple LED chips of different colors, such as Figure 14 As shown in the figure, each package structure includes chips of multiple colors. Because each color chip is offset from the center of the substrate, the light of each color is emitted into the air in different directions, preventing full mixing. Furthermore, the package structure emits light at a small angle, which exacerbates the color separation phenomenon. Therefore, by rotating adjacent package structures 90°, the same color light of different package structures is emitted in different directions, further enhancing the light mixing effect of the package module.

[0059] Some typical embodiments are described below. Example 1

[0060] like Figure 9-11 The figure shows an LED package structure comprising a substrate 1, an LED chip 2 bonded to the substrate 1, and an encapsulating adhesive layer 3 covering the LED chip 2. The substrate 1 is provided with a reflective structure 4 having a concave curved surface. The concave curved surface and the surface of the substrate 1 form a cavity. The LED chip 2 is located in the light-emitting area of ​​the cavity. The high-angle light emitted by the LED chip 2 passes through the reflective structure 4, changing its path and achieving a narrow-angle emission.

[0061] The LED chip 2 includes four vertical structure chips of four colors, namely red (R), yellow (Y), green (G) and blue (B). Each LED chip structure includes a chip substrate, a p-type layer, a quantum well layer, an n-type layer and a passivation layer. The passivation layer is located on the side wall of the LED chip. There is no passivation layer on the upper surface of the LED chip. The positive electrode is the lower surface of the LED chip, and the negative electrode of the LED chip is a patterned electrode on the upper surface of the LED chip. Figure 11 As shown, the dimensions of the four chips are 26 mil, 27 mil, 27 mil, and 20 mil, respectively. The characteristic width dimension a = 1.5 mm of the light-emitting area where the LED chip is located is related to the characteristic width dimension D = 3.5 mm of the substrate by a / D = 0.43. The encapsulation layer 3 is a raised structure with a height H = 4.2 mm and a characteristic width dimension b = 3.2 mm, resulting in an aspect ratio of 1.31. The encapsulation layer 3 comprises an upper lens 31 and a lower lens 32. The interface between the upper lens 31 and the lower lens 32 is coplanar with the upper surface of the reflective structure 4. The surface of the upper lens 31 is a non-rotationally symmetric free-form surface, and the interface between the upper lens 31 and the lower lens 32 is a centrosymmetric figure composed of free-form curves. The maximum width characteristic dimension of the interface is 2.

[0062] This embodiment utilizes a non-rotationally symmetric free-form surface lens, increasing effective optical surface utilization while maintaining the same dimensions. The shape of this free-form surface is determined by the geometry of the interface between the upper and lower lenses and the height of the upper lens. This limits the geometry of the interface and its maximum width, making the interface larger than the inscribed circle of the substrate. This increases the volume of the encapsulation layer and enables control of the extended light source's light pattern.

[0063] like Figure 11 As shown, the characteristic height dimension of reflective structure 4 (mm) limits the direct emission of light emitted from the center of substrate 1 at an angle greater than 50° to the normal, reducing wide-angle light leakage. The characteristic width dimension d of reflective structure 4 is related to the characteristic width dimension D of substrate 1 by d = D = 3.5 mm. The surface of reflective structure 4 is specular, with a specular reflectivity greater than 95%.

[0064] The entire surface of the encapsulation layer 3 is densely packed with a microstructure array 311. The microstructure units of the microstructure array are scales, and the base characteristic size of the microstructure units is 50. The microstructure array on the surface of the encapsulation layer 3 scatters light, which can alleviate the problem of dark stripes in the light spot at small angles. It also plays a role in light and color mixing for the packaging structure of multiple chips.

[0065] The lower lens 32 includes a light-mixing layer 5, which is composed of a micro-lens array and covers the surface of the LED chip 2. The refractive index of the light-mixing layer 5 is n1=1.54, and the refractive index of the encapsulation layer 3 is n2=1.41, which is n1>n2. After the light is emitted from the LED chip 2, it enters the light-mixing layer 5. Since the refractive index of the light-mixing layer 5 is different from that of the encapsulation layer 3, the light is refracted when passing through the micro-lens array of the light-mixing layer 5, which changes the light propagation path and realizes the change from discontinuous light emission from the chip surface to continuous light emission from the light-emitting surface of the light-mixing layer. The light-mixing layer 5 covers the surface of the LED chip 2, achieving light mixing without increasing the area of ​​the light-emitting surface. At the same time, n1>n2, the light is emitted in sequence through the LED chip 2, the light-mixing layer 5, the encapsulation layer 3 and then into the air. The refractive indices of the four are gradiently changed, which is more conducive to the full extraction of light.

[0066] According to the optical simulation results of the light distribution curve of the LED package in this embodiment, Figure 12 As shown, the packaging structure provided in this embodiment can achieve a half-intensity angle of 36°.

[0067] This embodiment also provides a packaging method for the above-mentioned LED packaging structure, comprising the following steps: A: Through a die-bonding process, the LED chips 2 are bonded to the substrate 1 provided with the reflective structure 4. The four LED chips 2 all have a vertical structure, specifically comprising a chip substrate, a p-type layer, a quantum well layer, an n-type layer, and a passivation layer. The passivation layer is different from that of conventional LED chips. In conventional LED chips, the passivation layer covers both the sidewalls and the top surface of the LED chip 2. In contrast, the passivation layer of the LED chip 2 in this embodiment only covers the sidewalls, with no passivation layer on the top surface. The cathode of the LED chip 2 is a patterned electrode on the top surface, and the anode is on the bottom surface.

[0068] B: Using wire bonding technology, the electrodes of the LED chip 2 are connected to the circuit of the substrate 1 to achieve electrical connection.

[0069] C: Preparation of light mixing layer 5: Place the substrate 1 after the above process on a hot plate, and apply encapsulation glue on the surface of the LED chip 2 to cover the LED chip 2. Figure 13 As shown, the LED package structure is connected to circuit ①, and the upper electrode and the lower electrode are prepared. The upper electrode is a needle tip electrode, the upper electrode is the negative electrode and is grounded, and the lower electrode is the negative electrode of the LED chip. The positive electrode of the LED chip is connected to the positive electrode pad of the package substrate, and the positive electrode pad of the package substrate is connected to the positive electrode of circuit ①. A DC power supply is used to apply an 8000V high-voltage electric field between the needle-tip electrode (with a large curvature difference) and the LED chip 2, achieving corona discharge. The gas molecules are ionized to form a negative ion wind, and the negative charges move downward under the action of the Coulomb force. The negative charges first accumulate on the surface of the non-conductive encapsulant. The electric field then drives the encapsulant to flow, causing the encapsulant to bulge and form a microlens array. At the same time, the negative charges are introduced from the top surface of the LED chip 2 into the LED chip 2, passing through the n-type layer, quantum well layer, p-type layer, and chip substrate in sequence. At this time, the negative charge flow process is consistent with the normal LED chip conduction principle. Therefore, the negative charges can turn on the LED chip 2 and then flow into the positive electrode of circuit ①. After the microlens array is formed and stabilized, the encapsulant is cured using a hot plate under continuous power supply, completing the preparation of the light-mixing layer microlens array.

[0070] D: Through the mold top process, using a lens mold with a non-rotationally symmetric free-form surface, an encapsulation layer is prepared on the substrate that has completed the above process. The surface of the lens mold is provided with a slice microstructure array with a certain embossing, and its surface finish range is Ra=2.0±1.0, Rz=8.5±3.5, to achieve the preparation of the microstructure array on the surface of the encapsulation layer. Then, the encapsulation layer is cured by heating to complete the preparation of the encapsulation structure.

[0071] This embodiment also provides an LED packaging module, such as Figure 14As shown, the LED package structure comprises four of the aforementioned LED packages, rotated 90° in sequence and tightly spaced. Each package structure contains chips of multiple different colors. Because each color chip is offset from the center of the substrate, the light emitted by each color is uneven in space. Furthermore, the package structures emit light at a narrow angle, exacerbating the color separation phenomenon. Therefore, by rotating adjacent package structures 90°, the same color light from different package structures is emitted in different directions, achieving uniform light mixing in the package module. Example 2

[0072] The LED packaging structure of Example 2 is similar to that of Example 1, except that: The LED package structure of this embodiment includes four chips of the same color and size. The characteristic width dimension a of the light-emitting area where the LED chip 2 is located is 1.5mm, and the characteristic width dimension D of the substrate 1 is 3.5mm. The relationship between the width dimension a / D is 0.43. The encapsulation layer 3 is a raised structure with a height of H = 3.5mm and a characteristic width dimension b = 3.2mm. Its aspect ratio is 1.09. Figure 15 As shown, the interface between the upper lens 31 and the lower lens 32 is a centrosymmetric figure, which is a combination of a free curve and a line segment.

[0073] According to the optical simulation results of the light distribution curve of the LED package in this embodiment, Figure 16 As shown, the LED packaging structure provided in this embodiment can achieve a half-intensity angle of 54°.

[0074] This embodiment also provides a packaging method for the above-mentioned LED packaging structure, comprising the following steps: A: The LED chip 2 is bonded to the substrate 1 provided with the reflective structure 4 through the die bonding process; the four LED chips 2 are all vertical structure chips, and the specific structure includes a chip substrate, a p-type layer, a quantum well layer, an n-type layer and a passivation layer, wherein the passivation layer is different from the traditional LED chip. The passivation layer of the traditional LED chip covers the side wall of the LED chip 2 and the upper surface of the LED chip, while the passivation layer of the LED chip 2 of this embodiment 1 only covers the side wall of the LED chip, and there is no passivation layer on the upper surface of the LED chip 2. The cathode of the LED chip 2 is the patterned electrode on the upper surface of the LED chip 2, and the anode is the lower surface of the LED chip 2.

[0075] B: Using wire bonding technology, the electrodes of the LED chip 2 are connected to the circuit of the substrate 1 to achieve electrical connection.

[0076] C: Place the substrate 1 after the LED chip die bonding and wire bonding process on a hot plate, and apply packaging glue on the surface of the LED chip 2 to cover the LED chip 2. Figure 17As shown, the LED package structure is connected to circuits 1 and 2. The upper and lower electrodes are prepared. The upper electrode is the needle-tip electrode of circuit 1, which is the negative electrode and grounded. The positive electrode of circuit 1 is connected to the positive pad of the package substrate. The lower electrode is the negative electrode of the LED chip. The negative electrode of the LED chip is connected to the negative pad of the package substrate via wire bonding. The positive electrode on the lower surface is connected to the positive pad of the package substrate. The negative pad of the package substrate is connected to the negative electrode of circuit 2, and the positive pad of the package substrate is connected to the positive electrode of circuit 2. A 2mA current is applied to the LED chip through circuit 2 to turn it on. A DC power supply applies a 5000V high-voltage electric field between the needle-tip electrode (with a significant difference in curvature) and the LED chip 2, creating a corona discharge. Ionization of gas molecules generates a negative ion wind, and negative charges move downward under the Coulomb force. The negative charges first accumulate on the surface of the non-conductive encapsulant, where they are then driven to flow by the electric field, causing the encapsulant to bulge and form a microlens array. Simultaneously, negative charges are introduced from the top surface of the LED chip 2, passing sequentially through the n-type layer, quantum well layer, p-type layer, chip substrate, and positive pad of the encapsulation substrate before entering circuit ②. Once the microlens array is formed and stabilized, the encapsulant is cured using a hot plate while continuously powered, completing the fabrication of the light-mixing layer microlens array.

[0077] D: Through the mold top process, using a lens mold with a non-rotationally symmetric free-form surface, an encapsulation layer is prepared on the substrate that has completed the above process. The surface of the lens mold is provided with a smooth flake microstructure array with a surface finish range of Ra=0.15±0.13 and Rz=0.6±0.5, thereby realizing the preparation of the microstructure array on the surface of the encapsulation layer. The encapsulation layer is then cured by heating to complete the preparation of the encapsulation structure. Example 3

[0078] This embodiment is similar to embodiment 1, except that: like Figure 18 As shown, the package structure of this embodiment includes a 27mil LED chip 2. The characteristic width dimension a of the light emitting area of ​​the LED chip 2 is 27mil, and the characteristic width dimension D of the substrate 1 is 3.5mm. The relationship between a / D is 0.2. The encapsulation layer 3 of this embodiment is a convex structure with a height of H = 3.7mm and a characteristic width dimension b = 3.2mm. Its aspect ratio is 1.16. Figure 19 As shown, the characteristic height dimension of the reflective structure 4 is mm, which limits the direct emission of light emitted from the center of the substrate 1 with an angle greater than 70° with the normal phase, thereby reducing large-angle light leakage.

[0079] According to the optical simulation results of the light distribution curve of the LED package in this embodiment, Figure 20 As shown, the LED packaging structure provided by Example 3 of the present invention can achieve a half-intensity angle of 20°. Example 4

[0080] This embodiment is similar to embodiment 1, except that: like Figure 21 As shown, the package structure of this embodiment includes a 45mil LED chip 2. The characteristic width dimension a of the light-emitting area of ​​the LED chip 2 is 45mil, and the characteristic width dimension D of the substrate 1 is 3.5mm. The relationship between a / D is 0.33. The encapsulation layer 3 of this embodiment is a convex structure with a height H of 3mm and a characteristic width dimension b of 3.2mm. Its aspect ratio is 0.94. There is no microstructure array on the surface of the encapsulation layer 3. Figure 22 As shown, the characteristic height dimension of the reflective structure 4 is mm, which limits the direct emission of light emitted from the center of the substrate 1 with an angle greater than 65° with the normal phase, thereby reducing large-angle light leakage.

[0081] According to the optical simulation results of the light distribution curve of the LED package in this embodiment, Figure 23 As shown, the LED packaging structure provided in this embodiment can achieve a half-intensity angle of 42°.

[0082] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may be modified or some of the technical features thereof may be replaced with equivalents. Such modifications or replacements do not deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention. Therefore, any equivalent changes or modifications made based on the principles and design ideas disclosed by the present invention are within the scope of protection of the present invention.

Claims

1. An LED packaging structure, characterized in that: Including substrate, reflective structure, LED chip and packaging layer; The reflective structure is provided with a concave arc surface, and the reflective structure is provided on the substrate, and the concave arc surface and the surface of the substrate enclose a cavity; The LED chip is arranged in the light emitting area of ​​the cavity, and the LED chip is bonded to the substrate; The encapsulation layer fills the cavity and protrudes from the cavity, and covers the LED chip; The encapsulation adhesive layer is composed of an upper lens and a lower lens, and the interface between the upper lens and the lower lens is located at the same horizontal plane as the upper surface of the reflective structure; The upper surface of the upper lens is a non-rotationally symmetric free-form surface; The interface between the upper lens and the lower lens is a centrosymmetric plane figure, and the centrosymmetric plane figure is composed of free curves or a combination of free curves and line segments; The lower lens includes a light-mixing layer, which is composed of a microlens array. The light-mixing layer covers the surface of the LED chip, and the refractive index n1 of the light-mixing layer and the refractive index n2 of the encapsulation layer are in the relationship of n1>n2; Wherein, the ratio of the height H of the encapsulation adhesive layer to the width characteristic dimension b of the interface is 0.5<H / b≤2; The maximum width characteristic dimension L of the interface max The relationship between the width characteristic dimension D of the substrate is D<L max <D; The relationship between the characteristic width dimension a of the light emitting region and the characteristic width dimension D of the substrate is 0.2≤a / D≤0.

8.

2. The LED packaging structure according to claim 1, wherein: The relationship between the height h of the reflective structure and the width characteristic dimension b of the interface is b / 2×cot70°≤h≤b / 2×cot50°, and the relationship between the width characteristic dimension d of the reflective structure and the width characteristic dimension D of the substrate is d=D.

3. The LED packaging structure according to claim 1, wherein: The concave arc surface of the reflective structure is mirror-reflective, and the reflectivity of the mirror-reflective structure is greater than 95%.

4. The packaging structure according to claim 1, wherein: The LED chip is single or multiple; the LED chip is a vertical structure, and the specific structure includes a first electrode, a chip substrate, a p-type layer, a quantum well layer, an n-type layer and a second electrode from bottom to top. The sidewalls of the LED chip are covered with a passivation layer, and the current flows vertically inside the LED chip.

5. The LED packaging structure according to claim 1, wherein: A microstructure array is provided on the top or the entire upper surface of the upper lens; the microstructure units of the microstructure array are scales, protrusions, and pyramids, and the characteristic size of the base of the microstructure unit is 10μm-500μm.

6. A packaging method for the LED packaging structure according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Providing a substrate having a reflective structure, wherein the reflective structure has a concave curved surface, and the concave curved surface and the surface of the substrate enclose a cavity; S2. Bonding the LED chip to the light-emitting area in the cavity on the substrate to achieve electrical connection between the LED chip and the substrate; S3. Prepare a light-mixing layer. Place the substrate obtained in step S2 on a hot plate. Apply encapsulation glue to the upper surface of the LED chip and cover the LED chip. Prepare upper and lower electrodes. Apply a high-voltage electric field between the upper and lower electrodes. The generated ion wind causes the encapsulation glue to form a raised microlens array. After the microlenses are formed and stabilized, heat and cure them to complete the preparation of the light-mixing layer. S4. Through the mold top process, using the lens mold, prepare an encapsulation layer on the substrate that has completed step S3. The encapsulation layer fills the cavity and protrudes from the cavity, and covers the LED chip and the light mixing layer; cure the encapsulation layer to complete the preparation of the encapsulation structure.

7. The LED packaging method according to claim 6, wherein: In step S4, a microstructure array is provided on the surface of the lens mold, wherein the microstructure units of the microstructure array are one of scales, protrusions, and pyramids, and the base feature size of the microstructure units is 10 μm-500 μm; and the surface finish of the lens mold is in the range of 0.15 μm≤Ra≤0.35 μm and 0.65 μm≤Rz≤12 μm.

8. An LED package module, characterized in that: The packaging module comprises four LED packaging structures according to any one of claims 1 to 5, wherein the four LED packaging structures are rotated 90° in sequence and closely distributed; each packaging structure comprises a plurality of LED chips of different colors.

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