High-brightness UV LED packaging method with high anti-sulfuration characteristics

Abstract

The present invention discloses a high-brightness ultraviolet LED packaging method with high anti-sulfuration characteristics. First, with the bracket light-emitting cup opening placed vertically upward, a high-refractive-index organic silicone is dispensed into the bracket cup through a dispenser for the inner encapsulation close to the chip. The height of the inner encapsulation is between at least completely covering all chips and bonding wires but lower than the horizontal plane of the bracket light-emitting cup opening. Then, a pre-baking is carried out by heating at 40 - 70 °C for 15 - 30 min for preliminary gelation. Then, on the preliminarily gelled inner encapsulation, a low-refractive-index organic silicone is directly dispensed for the outer lens encapsulation. After both the inner and outer encapsulations are filled and formed, the bracket is slowly flipped until the bracket light-emitting cup opening is vertically downward, which is more conducive to forming a curved outer lens encapsulation. Finally, a high-temperature curing bake is carried out by heating and maintaining at 100 - 170 °C for 3 - 6 h. After implementing this solution, a curved high-brightness ultraviolet LED with high anti-sulfuration can be produced at a lower cost and on a large scale quickly.

Description

Technical Field

[0001] The present invention relates to the field of LED packaging processes, and particularly to a high-brightness ultraviolet LED packaging method with high anti-sulfuration characteristics. Background Art

[0002] At present, as a semiconductor optoelectronic device, the light-emitting principle of an ultraviolet LED lamp bead is based on the electroluminescence effect of a PN junction. When a forward current passes through the PN junction, electrons and holes combine and release energy to generate light radiation. Compared with traditional light sources, LEDs have advantages such as high energy conversion efficiency, long lifespan, fast response speed, environmental protection and safety. Due to the characteristics of high heat and short emission wavelength of ultraviolet UVLEDs, the requirements for the performance of packaging materials are more stringent. The packaging of LED lamp beads is a process of placing an LED chip in a support structure, combining packaging processes and physically and chemically protecting and dissipating heat through packaging materials. The packaging process and materials have important influences on the performance, stability and reliability of LEDs.

[0003] However, in the existing actual application process, when the lamp beads are used in some specific working external environments that may contain substances with a relatively high sulfur content, etc., sulfur elements will gradually penetrate into the lamp beads over time and react with silver ions in the silver-plated layer of the bracket or the bonding wire to present an oxidation and blackening phenomenon. This is very likely to accelerate the light decay of the LED and shorten its service life. Furthermore, the performance and reliability of the product cannot be effectively guaranteed. Currently, the commonly used method to prevent sulfur elements from penetrating is to coat an anti-sulfuration layer inside the bracket or deepen the depth of the bowl of the bracket. The modification of the bracket structure will undoubtedly increase the cost accordingly, and this is a relatively single-layer local anti-sulfuration, and its anti-sulfur effect still has certain limitations. After the lamp beads are used for a period of time, there may be oxidation and blackening phenomena of different degrees of sulfuration reactions.

[0004] In view of this, the present technical solution proposes a high-brightness ultraviolet LED packaging method with high anti-sulfuration characteristics. The structure of the interface between the inner and outer packaging materials formed inside the bracket cup and the dislocation of the inner and outer interfaces effectively prevents harmful substances such as external sulfur elements from directly infiltrating from the inside. The bonding surface between the inner and outer packaging colloids and the surrounding materials is enlarged, and the bonding strength is greatly improved, so as to enhance the high-efficiency anti-sulfuration ability from the inside to the outside; the refractive indices of different inner and outer packaging colloids are reduced to minimize the refractive index difference from the surrounding packaging materials, thereby increasing the total internal reflection angle and reducing the total reflection loss, and improving the external light extraction efficiency, so as to obtain a high-brightness ultraviolet LED with long-lasting and effective high anti-sulfuration. Summary of the Invention

[0005] The technical solution of the present invention aims to solve at least one of the technical problems in the related art to a certain extent. For this reason, the main purpose of the present invention is to provide a high-brightness ultraviolet LED packaging method with high anti-sulfuration characteristics, aiming to solve the problems of blackening, short service life and poor stability of ultraviolet lamp beads due to sulfuration reaction during use caused by the existing packaging technology.

[0006] To achieve the above object, the present invention provides a high-brightness ultraviolet LED packaging method with high anti-sulfuration characteristics, including the following steps:

[0007] Inner layer encapsulation potting step,

[0008] Place the light-emitting cup mouth with a chip at the inner bottom vertically upward, and pour in a high-refractive-index silicone rubber similar to the refractive index of the chip, and keep the height of the high-refractive-index silicone rubber between the bonding wire of the chip and the horizontal plane of the light-emitting cup mouth;

[0009] Baking step,

[0010] Pre-bake the inner layer encapsulation body formed by combining the above chip and the high-refractive-index silicone rubber, and keep the baking temperature between 40-60°C and the baking time between 10-25 min;

[0011] Outer layer encapsulation potting step,

[0012] Dot-jet and pour in a low-refractive-index silicone rubber on the surface of the baked inner layer encapsulation body above to form a curved lens outer layer encapsulation body;

[0013] Overall curing and baking step,

[0014] Place the light-emitting cup mouth vertically downward, and heat-cure the above inner and outer layer encapsulation bodies together at a temperature of 100-170°C, and keep the duration at 3-6 h.

[0015] As a further scheme of the present invention, in the inner layer encapsulation potting step, the high-refractive-index silicone rubber is a silicone rubber with a refractive index greater than 1.5, and after the two-component glue is mixed in a ratio of 1:4, its viscosity is 12000-14000 mpa.s, the hardness is 75-80 HA, and the light transmittance is greater than 95% of the two-component high-refractive-index silicone rubber.

[0016] As a further scheme of the present invention, in the inner layer encapsulation potting step, the height of the high-refractive-index silicone rubber is between 1 / 2 and 2 / 3 times the cup depth height.

[0017] As a further scheme of the present invention, in the baking step, the baking temperature is a constant temperature of 50°C, and the duration is 15 min.

[0018] As a further solution of the present invention, in the outer layer encapsulation and potting step, the inner and outer layer encapsulation bodies are heated and cured together at a temperature of 150 °C, and the duration is maintained at 3 h.

[0019] As a further solution of the present invention, the light-emitting cup is a cup device with a bowl-shaped structure, and a bracket is provided at one end of the bowl-shaped cup structure.

[0020] As a further solution of the present invention, in the inner layer encapsulation and potting step, after the high refractive index organosilicon rubber is poured into the light-emitting cup, it is left standing at room temperature for 5 - 10 min.

[0021] As a further solution of the present invention, in the overall curing and baking step, after the light-emitting cup mouth is placed vertically downward, it is left standing at room temperature for 5 - 10 min.

[0022] As a further solution of the present invention, in the outer layer encapsulation and potting step, the low refractive index organosilicon rubber is an organosilicon rubber with a refractive index greater than 1.4, and after two groups of this organosilicon rubber are mixed in a ratio of 1:1, it is a two-component low refractive index organosilicon rubber with a viscosity of 15000 - 18000 mPa·s, a hardness of 70 - 75 HA, and a light transmittance greater than 96%.

[0023] As a further solution of the present invention, in the overall curing and baking step, when the inner and outer layer encapsulation bodies are cured at high temperature, a multi-stage heating method is adopted. This multi-stage heating method includes heating at 70 - 100 °C in the low-stage high temperature zone for 15 - 30 min while gradually increasing the temperature, then heating and raising the temperature to 110 - 130 °C in the middle-stage high temperature zone and keeping warm for 30 - 50 min, and finally keeping warm at 140 - 170 °C in the high-stage high temperature zone for 3 - 4 h.

[0024] The beneficial effects of the present invention are as follows:

[0025] The high-brightness ultraviolet LED encapsulation method with high anti-sulfuration characteristics proposed by the present invention, through the structure of the interface between the inner and outer layer encapsulation materials formed inside the bracket cup and the dislocation of the inner and outer interfaces, effectively prevents harmful substances such as external sulfur elements from directly infiltrating from the inside. The bonding surface between the inner and outer layer encapsulation colloids and the surrounding materials is enlarged, and the bonding strength is greatly improved, enhancing the high-efficiency anti-sulfuration ability from the inside to the outside; the refractive index differences between the different inner and outer layer encapsulation colloids and the surrounding encapsulation materials are reduced, thereby increasing the total internal reflection angle and reducing the total reflection loss, improving the external light extraction efficiency, and thus obtaining a high-brightness ultraviolet LED with long-lasting and effective high anti-sulfuration, extending the overall service life and stability of the product. Description of the Drawings

[0026] To more clearly illustrate the embodiments of the technical solution of the present invention or the inventive technical solution in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the technical solution of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0027] Figure 1 Schematic diagram of the implementation steps of the present invention.

[0028] Figure 2 Schematic diagram of the structure containing the inner encapsulation colloid in the present invention.

[0029] Figure 3 Schematic diagram of the structure of the inner encapsulation colloid in the present invention from another perspective.

[0030] Figure 4 Schematic diagram of the structure containing the inner and outer encapsulation colloids in the present invention.

[0031] Figure 5 Schematic diagram of the structure with the light-emitting cup mouth of the bracket in the present invention vertically downward. Detailed implementation manners

[0032] Are as follows:

[0033] Please refer to the attached Figures 1-5 ,

[0034] The main implementation steps include: the step of injecting glue for inner encapsulation.

[0035] Referring to Figure 2 , 3 , place the light-emitting cup mouth with a chip at the inner bottom vertically upward, and inject a high-refractive-index silicone rubber with a refractive index similar to that of the chip, and keep the height of the high-refractive-index silicone rubber between the bonding wire of the chip and the horizontal plane of the light-emitting cup mouth;

[0036] The inside of the lamp bead bracket has a cup depth with a bowl-shaped light-emitting cup. The 5054 type square cup bracket, which is a conventional and commonly used bracket in the market, can be selected. Two high refractive index silicone materials A / B with a refractive index greater than 1.5 are fully stirred evenly according to a ratio of 1:4 and subjected to vacuum degassing for about 5 minutes to obtain a mixed glue with a viscosity of 12000 - 14000 mpa.s, a hardness of 75 - 80 HA, and a light transmittance greater than 95%. The high refractive index silicone glue is automatically dispensed into the bottom of the bracket cup through a dispenser as the inner encapsulation glue close to the chip, which can effectively reduce the loss of photons at the chip light-emitting interface layer and increase the total reflection angle of light emitted from the chip interior, reducing the loss of light emission. Then, it is left to stand at room temperature for a certain period of time until the fluid glue evenly spreads and levels to form the inner encapsulation glue. The thickness of the glue is between at least completely covering all chips, bonding wires and below the horizontal plane of the bracket light-emitting cup mouth. Its thickness is preferably between 1 / 2 and 2 / 3 times the height of the bracket cup depth. In this way, the chip and the bonding wire 5 are respectively in the same inner encapsulation glue, effectively resisting damages such as peeling and cracking caused by stress change differences under different glues, greatly reducing external interference to it, and improving the reliability of the LED device.

[0037] Baking step,

[0038] The inner encapsulation body formed by combining the above chips and high refractive index silicone glue is pre-baked, and the baking temperature is maintained between 40 - 60 °C, and the baking time is between 10 - 25 min;

[0039] The inner encapsulation glue still needs to be pre-baked at a temperature of 40 - 60 °C for 10 - 25 min. It can be set to be heated and insulated at a constant temperature of 50 °C for 15 min. After a short period of pre-baking, the fluid inner encapsulation glue gradually forms a harder gel-like glue. The surface of the quasi-solidified glue is convenient for subsequent production process operations. During this process, the moisture slowly evaporates and the glue is gently and initially cured, and the inner encapsulation stress is slowly released, further reducing the damage to the inside caused by stress mutation, and also greatly reducing the formation of microvoids due to volume shrinkage after the inner encapsulation glue is thermally cured and cooled, resulting in interface peeling from the surrounding materials. From the inside of the lamp bead, the bonding strength and heat resistance are further improved. Compared with the low refractive index silicone material for the outer encapsulation, the high refractive index silicone material for the inner encapsulation is a higher density polymer, and has higher adhesiveness and denseness, and thus can effectively prevent external sulfur elements from infiltrating from the inside.

[0040] Outer encapsulation glue filling step,

[0041] Reference Figure 4 , the surface of the above-mentioned baked inner encapsulation body is further dispensed with low refractive index silicone glue to form a curved lens outer encapsulation body;

[0042] The preferred material for the outer encapsulation colloid is a low-refractive-index silicone rubber with a refractive index greater than 1.4. Two types of A / B adhesives are mixed in a ratio of 1:1. When preparing the ingredients, please note that the mixing ratio error should not exceed ±2%. The viscosity of the two adhesives after mixing is 15000 - 18000 mPa·s, the hardness is 70 - 75 HA, and the light transmittance is greater than 96%. On the basis of the flat surface of the inner encapsulation colloid that is already in a gel state, a low-refractive-index silicone rubber is poured in through a dispensing head different from that of the inner encapsulation and extruded to form a preliminary curved lens outer encapsulation colloid. Moreover, the thickness of the outer encapsulation colloid is higher than the horizontal plane of the light-emitting cup opening of the bracket by a certain distance. Then, the bracket is slowly placed vertically downward with the light-emitting cup opening reversed and left standing at room temperature for a period of time. Under the action of the gravitational field, the surface tension of the material is further utilized to form a more smooth curved lens outer encapsulation colloid in a pendant drop shape. The curved lens can narrow the light-emitting angle to improve the brightness. The way of pendant drop configuration downward also greatly avoids the overflow of the outer encapsulation colloid from the edge of the bracket in the case of placing the bracket vertically upward with the light-emitting cup opening, making the colloid flow more evenly.

[0043] The overall curing and baking steps

[0044] Reference Figure 5 , place the light-emitting cup opening vertically downward, and heat-cure the above inner and outer encapsulation bodies together at a temperature of 100 - 170 °C for a duration of 3 - 6 h.

[0045] Under the arrangement of the light-emitting cup opening of the bracket vertically downward, the inner encapsulation colloid and the outer encapsulation colloid are subjected to high-temperature curing and baking at a heating and curing temperature of 100 - 170 °C for 3 - 6 h. First, heat for 15 - 30 min while gradually increasing the temperature in the low-temperature high-temperature zone of 70 - 100 °C, then heat up to the middle-temperature high-temperature zone of 110 - 130 °C and keep it warm for 30 - 50 min, and finally keep it warm at the high-temperature high-temperature zone of 140 - 170 °C for 3 - 4 h. Further, keep it at a constant temperature of 150 °C for 3 h. Through three-stage high-temperature segmented heating of low, medium, and high temperatures, the inner and outer encapsulation colloids finally complete the final curing. This results in a bonding cross-linking interface that is lower than the horizontal plane of the light-emitting cup opening of the bracket, so that a more effective bonding surface with a greater depth can be formed between the outer encapsulation colloid and the bracket, playing a role in more effectively improving the outer bonding force. In addition, the bonding cross-linking interface lower than the horizontal plane of the light-emitting cup opening of the bracket is inside the cup, and the misalignment between the inside and outside of the two interfaces forms a certain protection, maximizing the avoidance of direct immersion of external sulfur elements, and also extending the immersion path, thereby greatly delaying the infiltration of external sulfur elements and prolonging the service life of the product.

[0046] The materials of the inner encapsulation colloid and the outer encapsulation colloid are of the same type of silicone, enabling a high compatibility between the two, thus forming a more powerful effective bonding cross-linking interface at the interface, and further continuously and effectively avoiding potential hazards such as silicone peeling and cracks caused by internal stress resulting from volume expansion and contraction changes due to external temperature variations and moisture absorption in a humid environment, and achieving high reliability in maintaining high luminous efficiency and high brightness for a long time.

[0047] A preferred embodiment of the present invention: In the step of inner encapsulation potting, the high refractive index silicone rubber is a silicone rubber with a refractive index greater than 1.5, and this silicone rubber is a two-component high refractive index silicone rubber with a viscosity of 12000 - 14000 mPa·s, a hardness of 75 - 80 HA, and a light transmittance greater than 95% after being mixed by two groups of glue in a ratio of 1:4.

[0048] A preferred embodiment of the present invention: In the step of inner encapsulation potting, the height of the high refractive index silicone rubber is between 1 / 2 and 2 / 3 times the height of the cup depth.

[0049] A preferred embodiment of the present invention: In the baking step, the baking temperature is a constant temperature of 50 °C, and the duration is 15 min.

[0050] A preferred embodiment of the present invention: In the step of outer encapsulation potting, the inner and outer encapsulation bodies are heated and cured together at a temperature of 150 °C, and the duration is maintained at 3 h.

[0051] A preferred embodiment of the present invention: The light-emitting cup is a cup body device with a bowl-shaped structure, and a bracket is provided at one end of the bowl-shaped cup body structure.

[0052] A preferred embodiment of the present invention: In the step of inner encapsulation potting, after the high refractive index silicone rubber is poured into the light-emitting cup, it is left to stand at room temperature for 5 - 10 min.

[0053] A preferred embodiment of the present invention: In the overall curing and baking step, after placing the light-emitting cup mouth vertically downward, it is left to stand at room temperature for 5 - 10 min.

[0054] A preferred embodiment of the present invention: In the step of outer encapsulation potting, the low refractive index silicone rubber is a silicone rubber with a refractive index greater than 1.4, and this silicone rubber is a two-component low refractive index silicone rubber with a viscosity of 15000 - 18000 mPa·s, a hardness of 70 - 75 HA, and a light transmittance greater than 96% after being mixed by two groups of glue in a ratio of 1:1.

[0055] A preferred embodiment of the present invention: In the overall curing and baking step, when the inner and outer encapsulation bodies are cured at high temperature, a multi-stage temperature increase method is adopted. The multi-stage temperature increase method includes heating for 15 - 30 minutes while gradually increasing the temperature in the low-stage high-temperature zone of 70 - 100°C, then maintaining the temperature for 30 - 50 minutes while heating and increasing the temperature to the middle-stage high-temperature zone of 110 - 130°C, and finally continuously maintaining the temperature for 3 - 4 hours in the high-stage high-temperature zone of 140 - 170°C.

[0056] The above is only the preferred embodiment of the technical solution of the present invention, and does not limit the patent scope of the technical solution of the present invention. Any equivalent structural transformation made under the inventive concept of the technical solution of the present invention by using the description and drawings of the technical solution of the present invention, or any direct / indirect application in other related technical fields, is included in the patent protection scope of the technical solution of the present invention.

Claims

1. A high-brightness UV LED packaging method with high anti-sulfuration characteristics, characterized in that it includes the following steps: S1. Inner layer encapsulation potting step, Place the light-emitting cup mouth with a chip at the inner bottom vertically upward, and pour in a high-refractive-index silicone rubber similar to the refractive index of the chip. The high-refractive-index silicone rubber is a mixture of two groups of glue in a ratio of 1:4, with a viscosity of 12000-14000 mPa·s, a hardness of 75-80 HA, a light transmittance greater than 95%, and the height of the colloid is 1 / 2 to 2 / 3 times the height of the cup depth; S2. Baking step, Pre-bake the above inner layer encapsulation body at a constant temperature of 50°C for 15 minutes; S3. Outer layer encapsulation potting step, Dot and pour a low-refractive-index silicone rubber on the surface of the pre-baked inner layer encapsulation body. The low-refractive-index silicone rubber is a mixture of two groups of glue in a ratio of 1:1, with a viscosity of 15000-18000 mPa·s and a light transmittance greater than 96%, forming a curved lens outer layer encapsulation body; S4. Overall curing and baking step, Place the light-emitting cup mouth vertically downward, and heat and cure the above inner and outer layer encapsulation bodies by a multi-stage heating method, including: Gradually heat up and heat at 70-100°C for 15-30 minutes; Keep warm at 110-130°C for 30-50 minutes; Keep warm continuously at 140-170°C for 3-4 hours.

2. The high-brightness ultraviolet LED packaging method with high anti-sulfuration characteristics according to claim 1, wherein In the inner layer encapsulation potting step, the height of the high-refractive-index silicone rubber is between 1 / 2 and 2 / 3 times the height of the cup depth.

3. The high-brightness ultraviolet LED packaging method with high anti-sulfuration characteristics according to claim 1, characterized in that In the outer layer encapsulation potting step, the inner and outer layer encapsulation bodies are heated and cured together at a temperature of 150°C, and the duration is kept at 3h.

4. The high-brightness ultraviolet LED packaging method with high anti-sulfuration characteristics according to claim 1, wherein, The light-emitting cup is a cup body device with a bowl-shaped structure, and a bracket is provided at one end of the bowl-shaped cup body structure.

5. The high-brightness ultraviolet LED packaging method with high anti-sulfuration characteristics according to claim 1, wherein, In the inner layer encapsulation potting step, after the high-refractive-index silicone rubber is poured into the light-emitting cup, it is left standing at room temperature for 5-10 min.

6. The high-brightness ultraviolet LED packaging method with high anti-sulfuration characteristics according to claim 1, wherein In the overall curing and baking step, after the light-emitting cup mouth is placed vertically downward, it is left standing at room temperature for 5-10 min.

7. The high-brightness ultraviolet LED packaging method with high anti-sulfuration characteristics according to claim 1, characterized in that In the outer layer encapsulation potting step, the low-refractive-index silicone rubber is a silicone rubber with a refractive index greater than 1.4, and after the two groups of glue are mixed in a ratio of 1:1, it is a two-component low-refractive-index silicone rubber with a viscosity of 15000-18000 mpa.s, a hardness of 70-75 HA, and a light transmittance greater than 96%.

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