A white light LED packaging structure and a manufacturing method thereof

Abstract

The application relates to the technical field of semiconductor packaging, and particularly discloses a white light LED packaging structure and a manufacturing method thereof. The packaging structure does not have an air cavity and at least comprises the following structural arrangement: a blue light flip LED wafer with opposite first and second surfaces; a retaining wall with opposite upper and lower end faces, which is arranged in close contact around the circumference of the blue light flip LED wafer and has an upper end face that is level with the first surface; a spacer layer with a gradually changing refractive index, which is arranged in layers on the first surface of the blue light flip LED wafer and the upper end face of the retaining wall; a thermal control layer arranged in layers on the spacer layer; and a composite layer arranged in layers on the thermal control layer, wherein the composite layer is a quantum dot fluorescent powder composite layer. The application designs a brand-new white light LED packaging structure, which optimizes the comprehensive performance and avoids the design defects of a traditional remote fluorescent structure.

Description

Technical Field

[0001] This invention relates to the field of semiconductor packaging technology, and more specifically, to a white LED packaging structure and its manufacturing method. Background Technology

[0002] Currently, traditional white LEDs use a bracket or CSP form, and excite yellow / red light to mix into white light by applying phosphor glue or attaching a phosphor film. The phosphor glue or phosphor film is in complete contact with the LED chip, which causes the heat of the LED chip to be directly conducted to the phosphor glue or phosphor film. However, the phosphor glue or phosphor film has poor thermal conductivity, which can easily lead to reduced luminous efficiency and greater light decay.

[0003] Traditional remote fluorescence structures employ a design where the chip and the fluorescent layer are separated, with a millimeter-level air or transparent medium spacer between them and an independent self-supporting fluorescent film. This type of structure not only has a relatively large overall thickness, but also suffers from optical reflection loss at the interface between different media. Furthermore, the fluorescent layer has limited heat dissipation capabilities, making it prone to thermal quenching with long-term use. Summary of the Invention

[0004] The purpose of this invention is to design a novel white LED packaging structure that optimizes overall performance while avoiding the design defects of traditional remote phosphor structures.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention designs a white LED packaging structure that has no air cavity and includes at least the following structural configuration: Blue flip-chip LEDs have opposing first and second surfaces. A barrier wall having opposing upper and lower surfaces, the barrier wall being circumferentially attached to the blue flip-chip LED chip, and its upper surface being flush with the first surface; A spacer layer having a gradient refractive index is stacked on the first surface and the upper surface of the blue flip LED chip and the barrier. A thermal control layer is stacked on the spacer layer; And a composite layer, which is stacked on the thermal control layer, wherein the composite layer is a quantum dot phosphor composite layer.

[0006] Furthermore, a white LED packaging structure is provided in which the thickness of the spacer layer is set to 10–80 μm, and several interconnected porous channels are formed inside it.

[0007] Furthermore, a white LED packaging structure is provided: the spacer layer is formed by curing a composite slurry composed of silicon dioxide, epoxy resin and a pore-forming agent, the refractive index of the spacer layer gradually changes from 1.55 to 1.40 along the thickness direction, and the refractive index of the spacer layer near the blue flip LED chip is 1.55.

[0008] Furthermore, a white LED packaging structure includes an adhesive layer disposed on the spacer layer, wherein the thermal control layer is bonded to the spacer layer via the adhesive layer; the thickness of the adhesive layer is set to 5–15 μm, and it is a UV thermal double-curing adhesive layer.

[0009] Furthermore, a white LED packaging structure is provided: the thickness of the thermal control layer is set to 5-15 μm, which is composed of 1-5 layers of graphene nanosheets and low-melting-point borosilicate glass powder sintered together, wherein the mass fraction of graphene nanosheets is 5-15%.

[0010] Furthermore, a white LED packaging structure is provided in which the thickness of the composite layer is set to 20–50 μm.

[0011] Furthermore, a white LED packaging structure: the composite layer includes a green quantum dot layer, a yellow phosphor layer, and a red phosphor layer stacked sequentially, wherein the green quantum dot layer is stacked on the thermal control layer; the yellow phosphor layer is made of YAG:Ce 3+ The yellow phosphor and the red phosphor layer are made of CaAlSiN3:Eu. 2+ Red phosphor.

[0012] Furthermore, a white LED packaging structure: the lower end face of the barrier is flush with the second surface.

[0013] Furthermore, a white LED packaging structure also includes a substrate, wherein the lower end face of the barrier and the second surface of the blue flip LED chip are connected to the substrate.

[0014] The present invention also provides a method for manufacturing a white LED packaging structure, the method comprising the following steps: S1. Place the electrode pads of several blue flip-chip LEDs face down on a UV temporary film or substrate so that several blue flip-chip LEDs are arranged in an array, and leave gaps for the white adhesive between the blue flip-chip LEDs. S2. A barrier flush with the first surface of the blue flip LED chip is made with white glue on the outer periphery of the chip and on the UV temporary film or substrate, and then cured. S3, a composite slurry including SiO2, epoxy resin and pore-forming agent is spin-coated on the coplanar surface of the flip-chip blue LED wafer and the barrier wall by a spin-coating process, and after spin-coating, pre-baking is performed to remove volatile solvents, then UV curing is performed, internal pore-forming agents are removed using warm water to form connected porous channels, and finally drying is performed to form a spacing layer on the flip-chip blue LED wafer and the barrier wall; S4, graphene nanosheets and borosilicate glass powder are mixed and sintered on a separate carrier to form a thermal control layer sheet; S5, the thermal control layer sheet is bonded to the spacing layer by a bonding layer to form a thermal control layer; S6, green fluorescent quantum dots, yellow fluorescent powder and red fluorescent powder are respectively coated on the thermal control layer by a spin-coating process to form a quantum dot fluorescent powder composite layer; S7, cutting and sorting are performed by a conventional LED cutting and sorting process, the UV temporary film is removed, and a single white light LED packaging structure is obtained.

[0015] Advantages of the application: The white light LED packaging structure designed in the application can avoid the quantum dot fluorescent powder composite layer being in close contact with the LED wafer, and the quantum dot fluorescent powder composite layer being directly exposed to the high-temperature zone of the LED wafer can easily cause thermal quenching (the higher the temperature, the lower the quantum efficiency, and the weaker the light emission), thereby causing the problems of low light efficiency and large light decay.

[0016] The white light LED packaging structure designed in the application further has a thermal control layer between the quantum dot fluorescent powder composite layer and the LED wafer, and the thermal conductivity of the thermal control layer is higher than that of the fluorescent glue used in conventional white light, which is beneficial to heat dissipation of the LED wafer and improves the stability of the LED.

[0017] The white light LED packaging structure designed in the application is a flip-chip LED packaging without an air cavity, which discards the cavity structure (air cavity) of the conventional CSP, avoids total reflection at the interface in the air cavity, reduces the reflection loss of blue light in the cavity, improves the light extraction efficiency, and completely eliminates the problem of thermal expansion of air in the cavity, thereby avoiding the risks of bubbling, delamination and cracking of each functional layer caused by changes in cavity air pressure when the device works at high temperature, and greatly improving the high-temperature working reliability. BRIEF DESCRIPTION OF DRAWINGS

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A cross-sectional schematic diagram of the white LED packaging structure designed for Example 1; Figure 2 A schematic diagram showing the arrangement of the blue flip-chip LED and the barrier in the white LED packaging structure designed for Example 1; Figure 3 A schematic diagram of the layered structure of the composite layer in the white LED packaging structure designed for Example 1; Figure 4 This is a cross-sectional schematic diagram of the white LED packaging structure designed for Example 2.

[0020] The markings in the image are as follows: 1-Blue flip-chip LED, 2-Blocking wall, 3-Spacer layer, 4-Adhesive layer, 5-Thermal control layer, 6-Composite layer, 7-Substrate, 61-Green quantum dot layer, 62-Yellow phosphor layer, 63-Red phosphor layer. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0022] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "top," and "bottom," etc., indicating orientation or positional relationships, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," etc., are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein.

[0023] Example 1

[0024] like Figures 1 to 3 As shown, this embodiment 1 designs a white LED packaging structure. This packaging structure has no air cavity and includes the following structural configuration: Blue flip-chip LED 1, which is fixed on a substrate and serves as the excitation light source for the LED, has a first surface 11 and a second surface 12 facing each other; The barrier 2 has an upper end face 21 and a lower end face 22. The barrier 2 is circumferentially attached to the blue flip LED chip 1, and its upper end face 21 is flush with the first surface 11. This can form a flat surface, providing a basis for the subsequent setting of each functional layer and ensuring thickness consistency. Spacer layer 3, having a gradually changing refractive index, is stacked on the first surface 11 and the upper end surface 21 of the blue flip LED chip 1 and the barrier 2. The thickness of spacer layer 3 is set to 10-80 μm, and several interconnected porous channels are formed inside it. The refractive index of spacer layer 3 gradually changes from 1.55 to 1.40 along the thickness direction, and the refractive index of spacer layer 3 near the blue flip LED chip 1 is 1.55. Adhesive layer 4 is disposed on the spacer layer 3. Adhesive layer 4 is a UV thermal double-curing adhesive layer with a thickness of 5-15 μm, used to connect spacer layer 3 and subsequent thermal control layer 5. A thermal control layer 5 is stacked on the adhesive layer 4, and the spacer layer 3 and the thermal control layer 5 are bonded together through the adhesive layer 4. The thickness of the thermal control layer 5 is set to 5-15 μm, and it is composed of 1-5 layers of graphene nanosheets and low melting point borosilicate glass powder sintered together, wherein the mass fraction of graphene nanosheets is 5-15%. Composite layer 6 is stacked on the thermal control layer 5. Composite layer 6 is a quantum dot phosphor composite layer with a thickness of 20-50 μm. Composite layer 6 includes a green quantum dot layer 61, a yellow phosphor layer 62 and a red phosphor layer 63 stacked sequentially. The green quantum dot layer 61 is stacked on the thermal control layer 5. The substrate 7 is connected to the lower end face 22 of the barrier 2 and the second surface 12 of the blue flip LED chip 1. The substrate 7 can be a ceramic substrate to support the LED chip 1 and the barrier 2.

[0025] Preferably, the lower end face 22 of the barrier 2 is flush with the second surface 12, which allows heat to be directly conducted to the PCB after it comes out from the second surface 12 of the LED chip 1, resulting in a short path.

[0026] This invention presents a novel white LED packaging structure that optimizes overall performance while avoiding the design flaws of traditional remote phosphor structures. The overall white LED packaging structure of this invention is a solid multilayer structure, circumventing the vulnerability of traditional cavity CSPs to moisture intrusion, resulting in high packaging reliability.

[0027] Specifically, in the white LED packaging structure designed in Example 1, the baffle 2 is arranged circumferentially around the blue flip LED chip 1, with the upper end face 21 flush with the first surface 11 of the LED chip and the lower end face 22 flush with the second surface 12 of the LED chip. This completely eliminates the air cavity inside the packaging structure. On the one hand, it avoids total internal reflection at the interface inside the air cavity, reduces the loss of blue light reflected back and forth in the cavity, and improves the light extraction efficiency. On the other hand, it completely eliminates the problem of air expansion inside the cavity due to heat, avoids the risk of bubbling, delamination, and cracking failure of each functional layer caused by changes in cavity air pressure when the device is heated during operation, and greatly improves the reliability of high-temperature operation. Meanwhile, the baffle 2 is circumferentially attached to the outer periphery of the LED chip 1, which provides physical restraint and lateral light shielding for the chip, preventing blue light leakage from the chip's sidewalls, reducing lateral stray light, and mitigating color shift issues. The baffle 2 also serves as structural support, providing a flat substrate for the upper spacer layer, thermal control layer, and composite layer, allowing for uniform film formation of each functional layer and preventing uneven film thickness, thus ensuring color consistency across the entire device. The baffle 2 and the surface of the chip 1 are flush, and the upper spacer layer 3 directly covers the plane shared by the chip 1 and the baffle 2, eliminating step differences and preventing stress concentration and cracking defects at step points.

[0028] Specifically, the fabrication method of the white LED packaging structure designed in Embodiment 1 above includes the following specific steps: S1. Place several blue flip-chip LEDs 1 with their electrode pads facing down on the substrate 7. The blue flip-chip LEDs 1 are arranged in an array on the substrate, and gaps are reserved between the blue flip-chip LEDs 1 for the white adhesive used to dam them. S2. A barrier 2, flush with the top surface (first surface 11) of the LED chip 1, is made on the outer periphery of the blue flip LED chip 1 and the substrate 7 using white glue and then cured. S3. A composite slurry including SiO2, epoxy resin and pore-forming agent is spin-coated on the coplanar surface of LED chip 1 and barrier wall 2 using a spin-coating process. The spin-coating process induces vertical liquid-liquid phase separation through solvent evaporation. After spin-coating, low-temperature pre-baking removes most of the volatile solvents, followed by UV curing. Warm water is used to dissolve the internal pore-forming agent to form interconnected porous channels. Finally, drying is performed to form a spacer layer 3 between blue flip-chip LED chip 1 and barrier wall 2. S4. Graphene nanosheets and borosilicate glass powder are mixed and sintered on an independent carrier to form a thermal control layer sheet. S5. The thermal control layer sheet is cured and bonded to the spacer layer 3 through the adhesive layer 4 (optical adhesive) to form the thermal control layer 5; S6. Green fluorescent quantum dots and yellow phosphor (YAG:Ce) 3+ Yellow phosphor, red phosphor (CaAlSiN3:Eu) 2+ Red phosphors were coated onto the thermal control layer 5 using a spin-coating process to form a quantum dot phosphor composite layer 6. S7. Cut and sort LEDs using traditional LED cutting and sorting processes to obtain a single white LED packaging structure.

[0029] Example 2

[0030] like Figure 4 As shown, the difference between Embodiment 2 and Embodiment 1 is that the white LED packaging structure of Embodiment 2 does not include the substrate 7; the rest of the design is the same as that of Embodiment 1. Specifically, the packaging structure of Embodiment 2 is a white CSP LED packaging structure.

[0031] Example 2 describes a method for fabricating this white LED packaging structure, which includes the following specific steps: S1. Place the electrode pads of several blue flip-chip LEDs 1 facing down on a UV temporary film. The several blue flip-chip LEDs 1 are arranged in an array on the UV temporary film, and a gap of white glue is reserved between the blue flip-chip LEDs 1. S2. A barrier 2, flush with the top surface (first surface 11) of the LED chip 1, is made on the outer periphery of the blue flip LED chip 1 and on the UV temporary film using white glue and then cured. S3. A composite slurry including SiO2, epoxy resin and pore-forming agent is spin-coated on the coplanar surface of LED chip 1 and barrier wall 2 using a spin-coating process. The spin-coating process induces vertical liquid-liquid phase separation through solvent evaporation. After spin-coating, low-temperature pre-baking removes most of the volatile solvents, followed by UV curing. Warm water is used to dissolve the internal pore-forming agent to form interconnected porous channels. Finally, drying is performed to form a spacer layer 3 between blue flip-chip LED chip 1 and barrier wall 2. S4. Graphene nanosheets and borosilicate glass powder are mixed and sintered on an independent carrier to form a thermal control layer sheet. S5. The thermal control layer sheet is cured and bonded to the spacer layer 3 through the adhesive layer 4 (optical adhesive) to form the thermal control layer 5; S6. Green fluorescent quantum dots and yellow phosphor (YAG:Ce) 3+ Yellow phosphor, red phosphor (CaAlSiN3:Eu) 2+ Red phosphors were coated onto the thermal control layer 5 using a spin-coating process to form a quantum dot phosphor composite layer 6. S7. Cut and sort LEDs using traditional LED cutting and sorting processes, remove the UV temporary film, and obtain a single white CSP LED packaging structure.

[0032] The above-described preferred embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of the invention. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A white LED packaging structure, characterized in that, This packaging structure has no air cavity and includes at least the following structural features: Blue flip-chip LED (1) has a first surface (11) and a second surface (12) opposite to each other; A barrier (2) having an opposing upper end face (21) and a lower end face (22) is provided in close contact with the blue flip LED chip (1) around its circumference, and its upper end face (21) is flush with the first surface (11). A spacer layer (3) having a gradient refractive index is stacked on the first surface (11) and the upper surface (21) of the blue flip LED chip (1) and the barrier (2); A thermal control layer (5) is stacked on the spacer layer (3); And a composite layer (6), which is stacked on the thermal control layer (5), wherein the composite layer (6) is a quantum dot phosphor composite layer.

2. The white LED packaging structure according to claim 1, characterized in that, The thickness of the spacer layer (3) is set to 10-80 μm, and several interconnected porous channels are formed inside it.

3. A white LED packaging structure according to claim 1 or 2, characterized in that, The spacer layer (3) is formed by curing a composite slurry composed of silicon dioxide, epoxy resin and pore-forming agent. The refractive index of the spacer layer (3) gradually changes from 1.55 to 1.40 along the thickness direction, and the refractive index of the spacer layer (3) near the blue flip LED chip (1) is 1.

55.

4. The white LED packaging structure according to claim 1, characterized in that, The encapsulation structure also includes an adhesive layer (4) disposed on the spacer layer (3), and the thermal control layer (5) is bonded to the spacer layer (3) through the adhesive layer (4); the thickness of the adhesive layer (4) is set to 5-15 μm, and it adopts a UV thermal double-curing adhesive layer.

5. A white LED packaging structure according to claim 1, characterized in that, The thickness of the thermal control layer (5) is set to 5-15 μm, and it is made of graphene nanosheets and low-melting-point borosilicate glass powder sintered together.

6. The white LED packaging structure according to claim 1, characterized in that, The thickness of the composite layer (6) is set to 20-50 μm.

7. The white LED packaging structure according to claim 1, characterized in that, The composite layer (6) includes a green quantum dot layer (61), a yellow phosphor layer (62) and a red phosphor layer (63) stacked sequentially, with the green quantum dot layer (61) stacked on the thermal control layer (5); The yellow phosphor layer (62) is made of YAG:Ce. 3+ The yellow phosphor, and the red phosphor layer (63) is made of CaAlSiN3:Eu 2+ Red phosphor.

8. The white LED packaging structure according to claim 1, characterized in that, The lower end face (22) of the retaining wall (2) is flush with the second surface (12).

9. A white LED packaging structure according to claim 1, characterized in that, It also includes a substrate (7), the lower end face (22) of the barrier (2) and the second surface (12) of the blue flip LED chip (1) are connected to the substrate (7).

10. A method for manufacturing a white LED packaging structure according to any one of claims 1 to 9, characterized in that, The method includes the following steps: S1. Place the electrode pads of several blue flip LED chips (1) with the electrode pads facing down on a UV temporary film or substrate (7) so that several blue flip LED chips (1) are arranged in an array, and leave gaps for dammed white glue between the blue flip LED chips (1). S2. A barrier (2) flush with the first surface (11) of the chip is made with white glue on the outer periphery of the blue flip LED chip (1) and the UV temporary film or substrate (7) and then cured. S3. A composite slurry including SiO2, epoxy resin and pore-forming agent is spin-coated on the coplanar surface of the blue flip-chip LED chip (1) and the barrier (2) by spin-coating. After spin-coating, the volatile solvent is removed by pre-baking, and then UV curing is performed. The internal pore-forming agent is dissolved by warm water to form interconnected porous channels. Finally, the chip is dried to form a spacer layer (3) on the blue flip-chip LED chip (1) and the barrier (2). S4. Graphene nanosheets and borosilicate glass powder are mixed and sintered on an independent carrier to form a thermal control layer sheet. S5. The thermal control layer sheet is cured and bonded to the spacer layer (3) through the adhesive layer (4) to form the thermal control layer (5). S6. Green fluorescent quantum dots, yellow phosphor and red phosphor are coated onto the thermal control layer (5) by spin coating process to form a quantum dot phosphor composite layer (6). S7. Cut and sort LEDs using traditional LED cutting and sorting processes to obtain a single white LED packaging structure.

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