White light LED heat conduction cup-shaped packaging structure and preparation method thereof

Abstract

The invention relates to a white light LED heat conduction cup-shaped packaging structure and a preparation method thereof. The white light LED heat conduction cup-shaped packaging structure comprises a substrate, an LED chip set, a packaging support, a heat conduction cup-shaped layer and a fluorescence conversion layer. Wherein the electrode surface of the LED chip set is welded or bonded on the substrate; heat conducting cup-shaped layers are arranged on the other side surfaces of the LED chip group except the light emitting surface; the bottom of the heat-conducting cup-shaped layer is attached to the substrate, the side face of the heat-conducting cup-shaped layer makes continuous contact with the packaging support, and the thickness of the heat-conducting cup-shaped layer is gradually increased towards the packaging support in the radial direction to form a cup-shaped structure. The fluorescence conversion layer is located in the central concave cavity of the heat conduction cup-shaped layer and wraps the LED chip set. According to the invention, thermal quenching and color drift of the fluorescent powder can be obviously inhibited, and high luminous intensity, stable color rendering index and related color temperature can be still maintained under high current density; the process adopts two-step curing and vacuum defoaming, is matched with a dispensing / potting process, and has good universality.

Description

Technical Field

[0001] This invention belongs to the field of LED packaging technology, and specifically relates to a heat-conducting cup-shaped packaging structure for white LEDs and its preparation method. Background Technology

[0002] White LEDs achieve mixed-color white light emission through fluorescence conversion and are currently widely used in displays, lighting, and signal indicators. The luminescence performance of phosphors is affected by ambient temperature. At high temperatures, lattice vibrations are easily intensified, causing excited-state energy to be released through non-radiative transitions such as phonon relaxation, resulting in a decrease in luminous intensity, i.e., thermal quenching. In various existing packaging methods, polymer encapsulation materials have low thermal conductivity, making it difficult to dissipate the heat generated during chip operation in a timely manner, leading to problems such as phosphor thermal quenching and color coordinate drift. To balance optical and thermal performance, it is necessary to reduce device thermal resistance and improve heat dissipation efficiency without significantly sacrificing light extraction efficiency. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a heat-conducting cup-shaped package structure for white LEDs and its preparation method. This structure can significantly suppress phosphor thermal quenching and color coordinate drift, maintain high luminous intensity under high current density, and have a stable color rendering index and correlated color temperature.

[0004] This invention provides a white LED thermally conductive cup-shaped package structure, including a substrate, an LED chip assembly, a package holder, a thermally conductive cup-shaped layer, and a phosphor conversion layer; wherein, the electrode surfaces of the LED chip assembly are soldered or bonded to the substrate; the other sides of the LED chip assembly, excluding the light-emitting surface, are provided with thermally conductive cup-shaped layers; the bottom of the thermally conductive cup-shaped layer is attached to the substrate, and the sides form continuous contact with the package holder, with the thickness increasing radially towards the package holder to form a cup-shaped structure; the phosphor conversion layer is located in the central cavity of the thermally conductive cup-shaped layer and covers the LED chip assembly.

[0005] Preferably, the thermally conductive cup-shaped layer is a composite material composed of a polymer matrix and a highly thermally conductive powder, and the composite material has an intrinsic transmittance of ≥85% in the visible light band.

[0006] Preferably, the polymer matrix is ​​selected from one or more of epoxy resin, silicone resin, polycarbonate, polyethylene terephthalate or polymethyl methacrylate.

[0007] Preferably, the high thermal conductivity powder is a powder material with a thermal conductivity greater than 50 W / m·K, including aluminum nitride (AlN) or boron nitride (BN), etc.

[0008] Preferably, the high thermal conductivity powder has a mass fraction of 5-35 wt% in the thermally conductive cup-shaped layer, more preferably 10-25 wt%.

[0009] Preferably, the high thermal conductivity powder body D 50 With a particle size of 0.5-10 μm, the mass fraction and particle size distribution of the high thermal conductivity powder meet the requirements for constructing a microscopic thermally conductive network.

[0010] Preferably, the thickness of the thermally conductive cup-shaped layer near the LED chipset is less than the chip height of the LED chipset, and the thickness near the packaging bracket is not greater than the height of the packaging bracket, so as to avoid blocking the light emission and ensure a continuous thermal conduction channel.

[0011] Preferably, the fluorescence conversion layer comprises one or more of the following: red, green, and blue phosphors excited by ultraviolet light (λ < 400 nm), violet light (400 nm ≤ λ ≤ 420 nm), or blue light (420 nm < λ ≤ 480 nm).

[0012] Preferably, the fluorescent conversion layer comprises a polymer matrix selected from one or more of epoxy resin, silicone resin, polycarbonate, polyethylene terephthalate or polymethyl methacrylate.

[0013] The fluorescence conversion layer consists of a polymer matrix and phosphors containing a different emission color than that of the chip. After absorbing light from the chip, the phosphors are converted into corresponding light through photoluminescence, and then white light is obtained through color mixing.

[0014] Preferably, the refractive index difference Δn between the fluorescence conversion layer and the thermally conductive cup-shaped layer is ≤0.1, so as to reduce the light loss caused by interface reflection.

[0015] This invention also provides a method for preparing a thermally conductive cup-shaped encapsulation structure for white LEDs, comprising the following steps:

[0016] (1) Take a substrate including an LED chip group, wherein the electrode surface of the LED chip group is welded or bonded to the substrate;

[0017] (2) Weigh the high thermal conductivity powder and the polymer matrix, mix them thoroughly, and then perform vacuum degassing to obtain a thermally conductive composite material;

[0018] (3) Apply adhesive or pot the above thermally conductive composite material from the inside of the encapsulation bracket, so that the material naturally extends into the LED chip group to form a cup-shaped structure with a thickness lower than the chip height near the chip and a thickness close to the encapsulation bracket height near the encapsulation bracket.

[0019] (4) Curing at 80-130 ℃ for 0.5-3 h yields a thermally conductive cup-shaped layer that is continuously bonded to the substrate;

[0020] (5) Mix red, green and blue phosphors with the polymer matrix, disperse them evenly and degas them under vacuum to obtain a fluorescent conversion material;

[0021] (6) The above-mentioned fluorescent conversion material is poured into the central cavity of the cup-shaped structure and naturally spread and flattened. It is cured at 80-130 ℃ for 0.5-3 h to form a fluorescent conversion layer and obtain a white LED thermally conductive cup-shaped encapsulation structure.

[0022] Beneficial effects

[0023] (1) The present invention forms a radial heat conduction channel from the chip sidewall outward by setting a heat-conducting cup-shaped layer with controllable thickness between the substrate and the packaging bracket, which significantly reduces the junction temperature rise rate and reduces the temperature fluctuation in the phosphor area; at the same time, by using a polymer matrix with the same type or similar refractive index as the fluorescence conversion layer, the interface reflection and scattering are reduced, and the light extraction efficiency is improved.

[0024] (2) The present invention can significantly suppress the thermal quenching and color drift of phosphors, maintain a high luminous intensity under high current density, and have a stable color rendering index and correlated color temperature; the process adopts two-step curing and vacuum degassing, which is compatible with dispensing / potting processes and has good versatility. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the white LED structure provided in Example 1.

[0026] Figure 2 This is a comparison of the luminous intensity of the white LED provided in Example 1 under the same load between Comparative Example 1 (without thermally conductive powder filling) and the experimental group (with thermally conductive powder filling).

[0027] Figure 3 The curves show the comparison of the luminous intensity of the white LED provided in Example 1 under different loads in Comparative Example 1 (without thermally conductive powder filling) and the experimental group (with thermally conductive powder filling).

[0028] Figure 4 This shows the relative variation trend of the luminous intensity of the white LED provided in Example 1 under different loads in Comparative Example 1 (without thermally conductive powder filling) and the experimental group (with thermally conductive powder filling).

[0029] Figure 5 The color rendering trends of the luminous intensity of the white LED provided in Example 1 under different loads are shown in Comparative Example 1 (without thermally conductive powder filling) and the experimental group (with thermally conductive powder filling).

[0030] Figure 6 The color temperature trend of the luminous intensity of the white LED provided in Example 1 under different loads is shown in Comparative Example 1 (without thermally conductive powder filling) and the experimental group (with thermally conductive powder filling). Detailed Implementation

[0031] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0032] Unless otherwise specified, the raw materials used in the following examples were obtained through conventional means and no further processing was performed on the reagents.

[0033] Example 1

[0034] In this embodiment, a white LED thermally conductive cup-shaped encapsulation structure is provided, such as... Figure 1 As shown. The packaging structure includes: a packaging bracket 1, a thermally conductive cup-shaped layer 2, a phosphor conversion layer 3, a substrate 4, and an LED chip assembly 5. The packaging bracket 1 is located outside the substrate 4 and fixed to the substrate 4, with its relative position perpendicular to the substrate. The electrode surface of the LED chip assembly 5 is soldered to the substrate 4. The LED chip assembly 5, except for the light-emitting surface, has a thermally conductive cup-shaped layer 2 on its other sides. The bottom of the thermally conductive cup-shaped layer 2 is in contact with the substrate 4, and its sides form continuous contact with the packaging bracket 1. Its thickness is not uniform; the thickness near the LED chip assembly 5 is slightly lower than the chip height of the LED chip assembly 5, and the thickness near the packaging bracket 1 gradually approaches the height of the packaging bracket 1, forming a cup-shaped structure. The polymer substrate in the thermally conductive cup-shaped layer 2 is epoxy resin, and the interior is filled with high thermal conductivity inorganic powder 9, which is AlN in this embodiment. The polymer substrate and the high thermal conductivity powder together constitute the thermally conductive layer. The phosphor conversion layer 3 is located in the central cavity of the thermally conductive cup-shaped layer 2 and covers the LED chip assembly 5, while also being encapsulated by the thermally conductive cup-shaped layer 2. The polymer substrate in the fluorescence conversion layer 3 is also epoxy resin, and its interior is filled with green phosphor 6, red phosphor 7, and blue phosphor 8. In this embodiment, the corresponding system is red phosphor Sr2Si5N8:Eu. 2+ (λ) em = 648 nm), green phosphor β-SiAlON (λ em = 550 nm) and blue phosphor BaMgAl 10 O 17 Eu 2+ (λ) em = 447 nm). The phosphor and the polymer substrate together form the fluorescence conversion layer 3.

[0035] In this embodiment, three experimental groups containing high thermal conductivity powder within the cup-shaped layers and one control group without high thermal conductivity powder were designed, and the device performance was characterized.

[0036] The preparation method includes the following steps:

[0037] S1. Weigh 0.60 g of epoxy resin as the thermally conductive cup-shaped layer substrate. Weigh different masses of AlN powder according to the mass percentage of epoxy resin, where experimental group 1 is 0.06 g (10 wt%), experimental group 2 is 0.12 g (20 wt%), and experimental group 3 is 0.18 g (30 wt%). Thoroughly mix the weighed AlN with epoxy resin, and then place it in a vacuum oven for degassing at a vacuum degree of -0.1 MPa for 30 minutes.

[0038] S2. After selecting multiple locations inside the packaging bracket, slowly pour in epoxy resin mixed with AlN powder. The epoxy resin flows naturally to the central LED chip group, forming a cup-shaped structure with a thermally conductive cup layer thickness that is slightly lower than the chip height when close to the chip and basically parallel to the packaging bracket when close to the packaging bracket.

[0039] S3. Perform the first curing process by placing the above product in an oven and keeping it at 120°C for 2 hours. After it naturally cools to room temperature, remove it to form a cured thermally conductive cup-shaped layer on the bottom of the substrate.

[0040] S4. Weigh 0.03 g of the red phosphor Sr2Si5N8:Eu 2+ 0.06 g of green phosphor β-SiAlON and 0.03 g of blue phosphor BaMgAl 10 O 17 Eu 2+ All phosphors were thoroughly and evenly ground in an agate mortar for 20 minutes. The total mass ratio of phosphors to epoxy resin substrate was fixed at 1:5, therefore 0.60 g of epoxy resin was weighed. After uniformly mixing the phosphors and epoxy resin, the mixture was placed in a vacuum oven and degassed under a vacuum of -0.1 MPa for 30 minutes.

[0041] S5. Slowly coat the epoxy resin substrate mixed with phosphor onto the center of the cup-shaped structure, so that the coating mass in each experimental group and the control group is basically the same. Then, perform a second curing treatment on the white LED and keep it at 120 ℃ for 2 hours to finally obtain the thermally conductive cup-shaped encapsulation structure of white LED.

[0042] Comparative Example 1

[0043] Compared to Example 1, in Comparative Example 1, only epoxy resin was weighed as the substrate, and AlN, which is a highly thermally conductive powder, was not weighed. The substrate was also degassed. The remaining encapsulation steps in the control group were exactly the same as in Example 1.

[0044] Device performance comparison test:

[0045] Figure 2The graphs show the comparison of luminescence intensity between experimental groups 1, 2, and 3 and Comparative Example 1 after operating for approximately 5 minutes under a load of 35 V / 16 mA. Experimental groups 1-3 all contain a thermally conductive cup-shaped layer containing AlN. The cup-shaped structure in Comparative Example 1 does not contain the thermally conductive AlN. As can be seen from the graphs, the luminescence intensity of experimental groups 1 and 2 is slightly higher than that of Comparative Example 1. This is because the improved heat dissipation capacity of the devices reduces the influence of temperature on the luminescence performance of the fluorescent material, resulting in higher luminescence intensity under this load, and superior performance at an AlN mass fraction of 20 wt%. The luminescence intensity of experimental group 3 is significantly lower than that of Comparative Example 1, possibly due to excessive AlN filling. The refractive index of AlN is approximately 2.0, while that of epoxy resin is approximately 1.5. This difference in refractive index leads to excessive reflection, thus increasing light loss, specifically manifested as a decrease in luminescence intensity.

[0046] Figure 3 The graph shows the comparison curves of the luminous intensity of the devices in experimental groups 1, 2, and 3 and comparative example 1 under different loads. The test voltage was fixed at 35 V, and the test current ranged from 16 to 240 mA. The luminous intensity of the devices was measured after operating under a certain load for about 1 minute. The graph shows that the luminous intensity of comparative example 1, compared to experimental groups 1-3, exhibits a similar trend under low load, but a decrease in luminous intensity under high load. Under low load, the heat generated by the LED chip group is not significant, so the presence or absence of a heat-conducting channel has little impact on device performance. Under high load, the LED chip group generates significant heat. Comparative example 1, lacking a heat-conducting channel, experiences heat accumulation inside the device, leading to a significant thermal quenching effect of the phosphor, thus resulting in a decrease in luminous intensity.

[0047] Figure 4-6 This shows the trends in luminous intensity, color rendering index, and relative color temperature of the devices in experimental groups 1, 2, and 3, and comparative example 1, under different loads. Figure 4 As can be seen, since the proportion of light in each part of the device spectrum does not change significantly under different loads, therefore for Figure 5 Medium color rendering index and Figure 6 The variation trend of the relative color temperature under different loads showed no significant difference between the experimental group and Comparative Example 1. However, the experimental group filled with thermally conductive material maintained its luminous intensity without decreasing under high loads due to improved heat dissipation.

Claims

1. A white LED thermally conductive cup-shaped packaging structure, characterized in that, The device includes a substrate, an LED chip assembly, a package bracket, a thermally conductive cup-shaped layer, and a phosphor conversion layer. The electrode surfaces of the LED chip assembly are soldered or bonded to the substrate. Thermally conductive cup-shaped layers are provided on the sides of the LED chip assembly, excluding the light-emitting surface. The bottom of the thermally conductive cup-shaped layer is attached to the substrate, and its sides form continuous contact with the package bracket. The thickness increases radially towards the package bracket to form a cup-shaped structure. The phosphor conversion layer is located within the central cavity of the thermally conductive cup-shaped layer and covers the LED chip assembly.

2. The white LED thermally conductive cup-shaped packaging structure according to claim 1, characterized in that, The thermally conductive cup-shaped layer is a composite material composed of a polymer matrix and highly thermally conductive powder.

3. The white LED thermally conductive cup-shaped packaging structure according to claim 2, characterized in that, The polymer matrix is ​​selected from one or more of epoxy resin, silicone resin, polycarbonate, polyethylene terephthalate or polymethyl methacrylate; the high thermal conductivity powder is a powder material with a thermal conductivity greater than 50 W / m·K.

4. The white LED thermally conductive cup-shaped packaging structure according to claim 2, characterized in that, The mass fraction of the high thermal conductivity powder in the thermally conductive cup-shaped layer is 5-35 wt%.

5. The white LED thermally conductive cup-shaped packaging structure according to claim 2, characterized in that, The high thermal conductivity powder body D 50 The range is 0.5-10 μm.

6. The white LED thermally conductive cup-shaped packaging structure according to claim 1, characterized in that, The thickness of the thermally conductive cup-shaped layer near the LED chipset is less than the height of the LED chipset, and the thickness near the packaging bracket is no greater than the height of the packaging bracket.

7. The white LED thermally conductive cup-shaped packaging structure according to claim 1, characterized in that, The fluorescence conversion layer contains one or more of the red, green, and blue phosphors excited by ultraviolet, violet, or blue light.

8. The white LED thermally conductive cup-shaped packaging structure according to claim 1, characterized in that, The fluorescent conversion layer comprises a polymer matrix selected from one or more of epoxy resin, silicone resin, polycarbonate, polyethylene terephthalate, or polymethyl methacrylate.

9. The white LED thermally conductive cup-shaped packaging structure according to claim 1, characterized in that, The refractive index difference Δn between the fluorescent conversion layer and the thermally conductive cup-shaped layer is ≤0.

1.

10. A method for preparing a white LED thermally conductive cup-shaped encapsulation structure as described in any one of claims 1-9, characterized in that, Includes the following steps: (1) Take a substrate including an LED chip group, wherein the electrode surface of the LED chip group is welded or bonded to the substrate; (2) Weigh the high thermal conductivity powder and the polymer matrix, mix them thoroughly, and then perform vacuum degassing to obtain a thermally conductive composite material; (3) Apply adhesive or pot the above thermally conductive composite material from the inside of the encapsulation bracket, so that the material naturally extends into the LED chip group to form a cup-shaped structure with a thickness lower than the chip height near the chip and a thickness close to the encapsulation bracket height near the encapsulation bracket. (4) Curing at 80-130 ℃ for 0.5-3 h yields a thermally conductive cup-shaped layer that is continuously bonded to the substrate; (5) Mix red, green and blue phosphors with the polymer matrix, disperse them evenly and degas them under vacuum to obtain a fluorescent conversion material; (6) The above-mentioned fluorescent conversion material is poured into the central cavity of the cup-shaped structure and naturally spread and flattened. It is cured at 80-130 ℃ for 0.5-3 h to form a fluorescent conversion layer and obtain a white LED thermally conductive cup-shaped encapsulation structure.

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