Constant-voltage double-color COB packaging technology

Abstract

The invention relates to the technical field of COB packaging, in particular to a constant-voltage double-color COB packaging technology. According to the preparation method, 1H, 1H, 2H, 2H-perfluorodecyl trimethoxy silane is used for carrying out hydrophobic modification on the heat-conducting filler, and the modified heat-conducting filler is obtained. And then preparing the organic silicon copolymer by taking polymethylhydrosiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate and glycidyl methacrylate as raw materials. And finally, bisphenol A epoxy resin, an organosilicon copolymer, a modified heat-conducting filler, a curing agent, a flame retardant and a flexibilizer are added to obtain the packaging adhesive with good heat-conducting property and hydrophobic and moisture-proof properties. A chip and a circuit are uniformly coated with the packaging adhesive, and a packaging structure is formed through constant-temperature curing. Therefore, the chip has a wide application prospect in the technical field of COB packaging.

Description

Technical Field

[0001] The present invention relates to the technical field of COB packaging, and specifically to a constant voltage dual-color COB packaging process. Background Art

[0002] In the field of modern electronic manufacturing, the COB (Chip on Board) packaging technology has become a key process due to its many advantages. As the core material of COB packaging, the encapsulating adhesive has important modern value. The encapsulating adhesive provides a stable physical protection and electrical insulation environment for the chip. It can effectively resist external mechanical shocks, vibrations, and temperature changes, avoiding damage to the chip due to external factors, thereby ensuring the stability and reliability of the operation of electronic devices. However, the chip generates heat continuously during operation. If the heat cannot be dissipated in time, the chip temperature will continue to rise. High temperature will seriously affect the performance of the chip, resulting in a slower operating speed, decreased stability, and even possible situations such as crashing and damage. Therefore, it is necessary to prepare an encapsulating adhesive with good thermal conductivity to quickly conduct the heat generated by the chip and maintain the chip working in a suitable temperature environment to ensure the stable performance of the chip. In addition, when water vapor invades the chip and the circuit, it is very likely to cause a short circuit in the circuit, making the electronic device unable to work properly. A humid environment may also cause corrosion of the chip and the circuit, damaging its electrical performance and mechanical structure. The hydrophobic and moisture-proof characteristics of the encapsulating adhesive can isolate external moisture, reduce the contact between the chip and moisture and corrosive substances, thereby preventing the chip from being corroded and improving the reliability and stability of the chip.

[0003] In order to overcome the defects of the prior art, the present invention provides a constant voltage dual-color COB packaging process. Summary of the Invention

[0004] The purpose of the present invention is to provide a constant voltage dual-color COB packaging process to solve the problems raised in the prior art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] An encapsulating adhesive for a constant voltage dual-color COB packaging process, and the content of each component of the encapsulating adhesive is as follows: by mass parts, 90 - 110 parts of bisphenol A epoxy resin, 35 - 45 parts of silicone copolymer, 30 - 40 parts of modified thermal conductive filler, 20 - 30 parts of curing agent, 15 - 25 parts of flame retardant, 10 - 20 parts of toughening agent; the curing agent is m-phenylenediamine, and the flame retardant is aluminum hydroxide flame retardant.

[0007] A preparation process of an encapsulating adhesive for a constant voltage dual-color COB packaging process, comprising the following steps:

[0008] Step S1: Under a nitrogen environment, mix the modified silicon carbide filler and the modified boron nitride filler, and ball mill them at a rotation speed of 150 - 250 rpm for 3 - 5 h to obtain a thermal conductive filler; then dissolve the thermal conductive filler in a mixed solvent, stir evenly, heat it up to 40 - 50 °C, and add 1H,1H,2H,2H - perfluorodecyltrimethoxysilane to react for 25 - 30 h. After the reaction, centrifuge, wash, and dry to obtain a modified thermal conductive filler;

[0009] Step S2: Mix polymethylhydrosiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and a Kastredt catalyst, and stir at 25 - 30 °C for 3 - 5 min to obtain an organosilicon copolymer;

[0010] Step S3: Pre - mix bisphenol A epoxy resin and the organosilicon copolymer, stir and react at 80 - 90 °C for 3 - 5 min, then add the modified thermal conductive filler, curing agent, flame retardant, and toughening agent, and continue to stir for 5 - 8 min to obtain an encapsulating adhesive.

[0011] Preferably, in step S1, the ball - to - material ratio for ball milling is (5 - 7):1; the mixed solvent consists of absolute ethanol and water, and the volume ratio is (10 - 12):1; the reaction mass ratio of the thermal conductive filler to 1H,1H,2H,2H - perfluorodecyltrimethoxysilane is 0.5:(1.3 - 1.5).

[0012] Preferably, in step S1, the preparation process of the modified silicon carbide filler is as follows: lay the silicon carbide filler evenly, heat it up at a heating rate of 5 °C / min to 700 - 750 °C and keep it warm for 2.5 - 3.0 h, 900 - 950 °C and keep it warm for 2.5 - 3.0 h, 1100 - 1200 °C and keep it warm for 1.5 - 2.0 h to obtain the modified silicon carbide filler.

[0013] Preferably, in step S1, the preparation process of the modified boron nitride filler is as follows: mix absolute ethanol, ammonia water, and deionized water, stir evenly to obtain a mixed solution, then add the boron nitride filler, continue to stir for 30 - 40 min, slowly dropwise add tetraethyl orthosilicate, and continue to stir and react for 2 - 3 h after the addition. After the reaction, centrifuge, wash, and dry to obtain the modified boron nitride filler.

[0014] Preferably, the reaction mass ratio of absolute ethanol, ammonia water, deionized water, boron nitride filler, and tetraethyl orthosilicate is 100:4:3:0.25:(1.2 - 2.0).

[0015] Preferably, in step S2, the reaction mass ratio of polymethylhydrosiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and Kastredt catalyst is 15:(3 - 4):1:(1.7 - 2.0):0.1.

[0016] A constant - pressure two - color COB packaging process, prepared using the said encapsulating adhesive, includes the following steps: First, take a single - sided FPC board as the packaging substrate, then weld the two - color LED wafers at the designated positions on the FPC printed circuit board. After silver paste curing and black glue secondary curing, perform circuit connection and preliminary detection to obtain a COB packaging module; evenly coat the encapsulating adhesive onto the chips and circuits, and after constant - temperature curing, form an encapsulating structure.

[0017] Preferably, the silver paste curing parameters are: curing at 120 - 130 °C for 50 - 60 min; the black glue secondary curing parameters are: curing at 150 - 180 °C for 30 - 50 min; the constant - temperature curing parameters are: curing at 130 - 150 °C for 40 - 50 min.

[0018] The beneficial effects of the present invention:

[0019] The characteristics of the present invention are that in step S1, by performing staged high - temperature oxidation on the silicon carbide filler, a modified silicon carbide filler coated with silica is obtained; by adding anhydrous ethanol, ammonia water, deionized water, and tetraethyl orthosilicate to perform surface modification on the boron nitride filler, a modified boron nitride filler coated with silica is obtained. Coating the silica layer on the surfaces of the two thermal conductive fillers can, on the one hand, improve the agglomeration of the fillers, and on the other hand, enhance the hydrophobic properties of the two thermal conductive fillers. Further, the modified silicon carbide filler and the modified boron nitride filler are ball - milled and mixed to obtain a uniformly dispersed thermal conductive filler. Through the ball - milling process, a uniformly dispersed thermal conductive filler is obtained, and the two fillers can be interconnected and intertwined in the encapsulating adhesive matrix to form a more complete and efficient thermal conductive network, enabling heat to be transferred more smoothly between the fillers, reducing the obstacles and scattering during the heat transfer process, thereby significantly improving the overall thermal conductivity efficiency of the encapsulating adhesive and more effectively dissipating the heat generated by the chip.

[0020] Then, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is used to hydrophobically modify the thermal conductive filler to obtain a modified thermal conductive filler. The 1H,1H,2H,2H-perfluorodecyltrimethoxysilane molecule contains a long-chain fluorocarbon group, and the fluorocarbon chain has an extremely low surface energy. When it modifies the thermal conductive filler, a fluorocarbon coating with strong water repellency will be formed on the surface of the filler. This makes it difficult for water molecules to spread and adsorb on the surface of the filler, greatly improving the hydrophobic performance of the thermal conductive filler. In a humid environment, it can effectively prevent the intrusion of moisture, prevent the agglomeration, oxidation of the filler caused by moisture, and the negative impact on the performance of the encapsulant, ensuring the stable operation of electronic components in a humid environment.

[0021] The feature of the present invention is that in step S2, polymethylhydrogensiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and a Kastredt catalyst are mixed and stirred evenly to obtain a silicone copolymer. In this step, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, and glycidyl methacrylate can undergo a hydrosilylation reaction with polymethylhydrogensiloxane under the action of a catalyst to obtain a silicone copolymer; by setting the reaction mass ratio of dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, and glycidyl methacrylate to (3-4):1:(1.7-2.0) in this step, a waterproof fluorine group, a curable amino group, and an epoxy group can be introduced simultaneously, and finally a silicone copolymer with excellent hydrophobic performance is obtained. In addition, the silicone copolymer obtained in this step has an epoxy group similar to that of bisphenol A epoxy resin, so it has good compatibility with epoxy resin. The curable amino group contained in the silicone copolymer also plays a key role in the curing and crosslinking process of the encapsulant. Specifically, the amino group can undergo a chemical crosslinking reaction with the epoxy group in the epoxy resin, forming a large number of chemical bond connections between bisphenol A epoxy resin, the silicone copolymer, and the curing agent, and constructing a dense crosslinked network. This crosslinked network structure is tight and has strong intermolecular forces, which can effectively prevent the diffusion and penetration of water molecules and further enhance the moisture-proof performance of the encapsulant.

[0022] In step S3, by adding bisphenol A epoxy resin, a silicone copolymer, a modified thermal conductive filler, a curing agent, a flame retardant, and a toughening agent, an encapsulant with good thermal conductivity and hydrophobic and moisture-proof performance is obtained, so it has a broad application prospect in the field of COB packaging technology. Specific embodiments

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] Source of raw materials:

[0025] Silicon carbide filler, provided by Henan Sicheng Grinding Technology Co., Ltd., with a particle size of 320 mesh; boron nitride filler, provided by Dongguan Dongchao New Materials Technology Co., Ltd., with a particle size of 500 mesh; polymethylhydrogensiloxane, provided by Zhonglan Chenguang Research Institute of Chemical Industry, with a hydrogen content of 1.5%; bisphenol A epoxy resin, provided by Guangzhou Kaixin New Materials Technology Co., Ltd., model E-44; toughening agent, provided by Jinan Baijin Chemical Technology Co., Ltd., model 552; by mass fraction, one part is 1 g.

[0026] Example 1: Step S1: Spread the silicon carbide filler evenly and heat it to 750 °C at a heating rate of 5 °C / min for 3.0 h, 950 °C for 3.0 h, and 1200 °C for 2.0 h to obtain modified silicon carbide filler;

[0027] Mix anhydrous ethanol, ammonia water, and deionized water, stir evenly to obtain a mixed solution, then add boron nitride filler, continue to stir for 40 min, and then slowly dropwise add tetraethyl orthosilicate. After the addition is completed, continue to stir and react for 3 h. After the reaction is completed, centrifuge, wash, and dry to obtain modified boron nitride filler; the reaction mass ratio of anhydrous ethanol, ammonia water, deionized water, boron nitride filler, and tetraethyl orthosilicate is 100:4:3:0.25:1.5;

[0028] In a nitrogen environment, mix the modified silicon carbide filler and the modified boron nitride filler, and ball mill at a speed of 250 rpm / min for 5 h to obtain a thermal conductive filler; then dissolve the thermal conductive filler in a mixed solvent, stir evenly and heat to 50 °C, and then add 1H,1H,2H,2H-perfluorodecyltrimethoxysilane and react for 30 h. After the reaction is completed, centrifuge, wash, and dry to obtain a modified thermal conductive filler; the ball-to-material ratio of ball milling is 6:1; the mixed solvent consists of anhydrous ethanol and water, with a volume ratio of 11:1; the reaction mass ratio of the thermal conductive filler and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is 0.5:1.4;

[0029] Step S2: Mix polymethylhydrosiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and Kastredt catalyst, and stir at 30°C for 5 min to obtain an organosilicon copolymer; the reaction mass ratio of polymethylhydrosiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and Kastredt catalyst is 15:3.5:1:1.8:0.1;

[0030] Step S3: Pre-mix 110 g of bisphenol A epoxy resin and 45 g of organosilicon copolymer, stir and react at 90°C for 5 min, then add 40 g of modified thermal conductive filler, 30 g of m-phenylenediamine, 25 g of aluminum hydroxide flame retardant, and 20 g of toughening agent, and continue to stir for 8 min to obtain an encapsulating adhesive;

[0031] Step S4: First, take a single-sided FPC board as the encapsulation substrate, then weld the dual-color LED chips at the specified positions on the FPC printed circuit board, cure with silver paste, and perform secondary curing with black glue, followed by circuit connection and preliminary testing to obtain a COB encapsulation module; uniformly coat the encapsulating adhesive onto the chips and circuits, and cure at a constant temperature to form an encapsulation structure; Silver paste curing parameters: Cure at 130°C for 60 min; Black glue secondary curing parameters: Cure at 180°C for 50 min; Constant temperature curing parameters: Cure at 150°C for 50 min.

[0032] Example 2: Step S1: Spread the silicon carbide filler evenly and heat it to 725°C at a heating rate of 5°C / min for 2.7 h, 925°C for 2.7 h, and 1150°C for 1.7 h to obtain modified silicon carbide filler;

[0033] Mix absolute ethanol, ammonia water, and deionized water, stir evenly to obtain a mixed solution, then add boron nitride filler, continue to stir for 35 min, and then slowly dropwise add tetraethyl orthosilicate. After the addition is completed, continue to stir and react for 2.5 h. After the reaction is completed, perform centrifugation, washing, and drying to obtain modified boron nitride filler; the reaction mass ratio of absolute ethanol, ammonia water, deionized water, boron nitride filler, and tetraethyl orthosilicate is 100:4:3:0.25:1.5;

[0034] Under a nitrogen atmosphere, the modified silicon carbide filler and the modified boron nitride filler are mixed and ball-milled at a rotation speed of 200 rpm for 4 h to obtain a thermal conductive filler; then the thermal conductive filler is dissolved in a mixed solvent, stirred evenly, heated to 45 °C, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is added and reacted for 27 h. After the reaction is completed, it is centrifuged, washed, and dried to obtain a modified thermal conductive filler; the ball-to-material ratio of the ball milling is 6:1; the mixed solvent consists of absolute ethanol and water, and the volume ratio is 11:1; the reaction mass ratio of the thermal conductive filler and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is 0.5:1.4;

[0035] Step S2: Mix polymethylhydrosiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and Kastredt catalyst, and stir at 27 °C for 4 min to obtain an organosilicon copolymer; the reaction mass ratio of polymethylhydrosiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and Kastredt catalyst is 15:3.5:1:1.8:0.1;

[0036] Step S3: Pre-mix 110 g of bisphenol A epoxy resin and 45 g of the organosilicon copolymer, stir and react at 85 °C for 4 min, then add 40 g of the modified thermal conductive filler, 30 g of m-phenylenediamine, 25 g of aluminum hydroxide flame retardant, and 20 g of toughening agent, and continue to stir for 6 min to obtain an encapsulating adhesive;

[0037] Step S4: First, take a single-sided FPC board as the encapsulation substrate, then weld the dual-color LED chips at the specified positions on the FPC printed circuit board, cure with silver paste, and perform secondary curing with black glue, followed by circuit connection and preliminary testing to obtain a COB encapsulation module; uniformly coat the encapsulating adhesive onto the chips and circuits, and cure at a constant temperature to form an encapsulation structure; the silver paste curing parameters: cure at 125 °C for 55 min; the black glue secondary curing parameters: cure at 160 °C for 40 min; the constant temperature curing parameters: cure at 140 °C for 45 min.

[0038] Example 3: Step S1: Spread the silicon carbide filler evenly and heat it to 700 °C at a heating rate of 5 °C / min for 2.5 h, 900 °C for 2.5 h, and 1100 °C for 1.5 h to obtain a modified silicon carbide filler;

[0039] Mix absolute ethanol, ammonia water, and deionized water, stir evenly to obtain a mixed solution, then add boron nitride filler, continue to stir for 30 min, and slowly dropwise add tetraethyl orthosilicate. After the dropping is completed, continue to stir and react for 2 h. After the reaction is completed, it is centrifuged, washed, and dried to obtain a modified boron nitride filler; the reaction mass ratio of absolute ethanol, ammonia water, deionized water, boron nitride filler, and tetraethyl orthosilicate is 100:4:3:0.25:1.5;

[0040] Under a nitrogen atmosphere, the modified silicon carbide filler and the modified boron nitride filler are mixed and ball-milled at a rotation speed of 150 rpm for 3 h to obtain a thermal conductive filler; then the thermal conductive filler is dissolved in a mixed solvent, stirred evenly, heated to 40 °C, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is added for reaction for 25 h. After the reaction is completed, it is centrifuged, washed, and dried to obtain a modified thermal conductive filler; the ball-to-material ratio of the ball milling is 6:1; the mixed solvent is composed of absolute ethanol and water, and the volume ratio is 11:1; the reaction mass ratio of the thermal conductive filler to 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is 0.5:1.4;

[0041] Step S2: Mix polymethylhydrogensiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and Kastredt catalyst, and stir at 25 °C for 3 min to obtain an organosilicon copolymer; wherein the reaction mass ratio of polymethylhydrogensiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and Kastredt catalyst is 15:3.5:1:1.8:0.1;

[0042] Step S3: Pre-mix 110 g of bisphenol A epoxy resin and 45 g of organosilicon copolymer, stir and react at 80 °C for 3 min, then add 40 g of modified thermal conductive filler, 30 g of m-phenylenediamine, 25 g of aluminum hydroxide flame retardant, and 20 g of toughening agent, and continue to stir for 5 min to obtain an encapsulating adhesive;

[0043] Step S4: First, take a single-sided FPC board as the encapsulation substrate, then weld the dual-color LED chip at the specified position on the FPC printed circuit board, cure with silver paste, and perform secondary curing with black glue, followed by circuit connection and preliminary detection to obtain a COB encapsulation module; uniformly coat the encapsulating adhesive onto the chip and the circuit, and cure at a constant temperature to form an encapsulation structure; Silver paste curing parameters: Cure at 120 °C for 50 min; Black glue secondary curing parameters: Cure at 150 °C for 30 min; Constant temperature curing parameters: Cure at 130 °C for 40 min.

[0044] Comparative Example 1: Replace the modified thermal conductive filler with silicon carbide filler, and the rest is the same as in Example 1. The specific steps are as follows: Step S1: Mix polymethylhydrogensiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and Kastredt catalyst, and stir at 30 °C for 5 min to obtain an organosilicon copolymer; wherein the reaction mass ratio of polymethylhydrogensiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and Kastredt catalyst is 15:3.5:1:1.8:0.1;

[0045] Step S2: Pre-mix 110 g of bisphenol A epoxy resin and 45 g of silicone copolymer, stir and react at 90 °C for 5 min, then add 40 g of silicon carbide filler, 30 g of m-phenylenediamine, 25 g of aluminum hydroxide flame retardant, and 20 g of toughening agent, and continue to stir for 8 min to obtain the encapsulation adhesive;

[0046] Step S3: First, take a single-sided FPC board as the encapsulation substrate, then weld the dual-color LED chips at the designated positions on the FPC printed circuit board, cure with silver paste, and perform circuit connection and preliminary detection after secondary curing with black glue to obtain the COB encapsulation module; uniformly coat the encapsulation adhesive onto the chips and circuits, and form an encapsulation structure after curing at a constant temperature; Silver paste curing parameters: Cure at 130 °C for 60 min; Black glue secondary curing parameters: Cure at 180 °C for 50 min; Constant temperature curing parameters: Cure at 150 °C for 50 min.

[0047] Comparative Example 2: Remove the silicone copolymer, and the rest is the same as in Example 1. The specific steps are as follows: Step S1: Spread the silicon carbide filler evenly and heat it to 750 °C at a heating rate of 5 °C / min for 3.0 h, 950 °C for 3.0 h, and 1200 °C for 2.0 h to obtain the modified silicon carbide filler;

[0048] Mix anhydrous ethanol, ammonia water, and deionized water, stir evenly to obtain a mixed solution, then add boron nitride filler, continue to stir for 40 min, and then slowly dropwise add tetraethyl orthosilicate. After the addition is complete, continue to stir and react for 3 h. After the reaction is completed, perform centrifugation, washing, and drying to obtain the modified boron nitride filler; The reaction mass ratio of anhydrous ethanol, ammonia water, deionized water, boron nitride filler, and tetraethyl orthosilicate is 100:4:3:0.25:1.5;

[0049] Under a nitrogen atmosphere, mix the modified silicon carbide filler and the modified boron nitride filler, and ball mill at a speed of 250 rpm for 5 h to obtain the thermal conductive filler; then dissolve the thermal conductive filler in the mixed solvent, stir evenly, heat to 50 °C, and then add 1H,1H,2H,2H-perfluorodecyltrimethoxysilane and react for 30 h. After the reaction is completed, perform centrifugation, washing, and drying to obtain the modified thermal conductive filler; The ball-to-powder ratio for ball milling is 6:1; The mixed solvent consists of anhydrous ethanol and water, and the volume ratio is 11:1; The reaction mass ratio of the thermal conductive filler and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is 0.5:1.4;

[0050] Step S2: Pre-stir 110 g of bisphenol A epoxy resin at 90 °C for 5 min, then add 40 g of the modified thermal conductive filler, 30 g of m-phenylenediamine, 25 g of aluminum hydroxide flame retardant, and 20 g of toughening agent, and continue to stir for 8 min to obtain the encapsulation adhesive;

[0051] Step S3: First, take a single-sided FPC board as the encapsulation substrate, then solder the dual-color LED wafers at the specified positions on the FPC printed circuit board. After curing with silver paste and secondary curing with black glue, perform circuit connection and preliminary testing to obtain a COB encapsulation module; uniformly coat the encapsulation glue onto the chips and circuits, and cure at a constant temperature to form an encapsulation structure; Silver paste curing parameters: Cure at 130°C for 60 min; Black glue secondary curing parameters: Cure at 180°C for 50 min; Constant temperature curing parameters: Cure at 150°C for 50 min.

[0052] Comparative Example 3: Adjust the reaction mass ratio of dodecafluorooctyl methacrylate, diethylaminoethyl methacrylate, and glycidyl methacrylate from (3 - 4):1:(1.7 - 2.0) to 1:1:1, and the rest is the same as in Example 1. The specific steps are as follows: Step S1: Spread the silicon carbide filler evenly and heat it to 750°C at a heating rate of 5°C / min for 3.0 h, 950°C for 3.0 h, and 1200°C for 2.0 h to obtain modified silicon carbide filler;

[0053] Mix anhydrous ethanol, ammonia water, and deionized water, stir evenly to obtain a mixed solution, then add boron nitride filler, continue to stir for 40 min, and then slowly dropwise add tetraethyl orthosilicate. After the addition is complete, continue to stir and react for 3 h. After the reaction is completed, perform centrifugation, washing, and drying to obtain modified boron nitride filler; The reaction mass ratio of anhydrous ethanol, ammonia water, deionized water, boron nitride filler, and tetraethyl orthosilicate is 100:4:3:0.25:1.5;

[0054] Under a nitrogen atmosphere, mix the modified silicon carbide filler and the modified boron nitride filler, and ball mill at a speed of 250 rpm for 5 h to obtain a thermal conductive filler; Then dissolve the thermal conductive filler in the mixed solvent, stir evenly, heat to 50°C, and then add 1H,1H,2H,2H - perfluorodecyltrimethoxysilane and react for 30 h. After the reaction is completed, perform centrifugation, washing, and drying to obtain modified thermal conductive filler; The ball - to - material ratio for ball milling is 6:1; The mixed solvent consists of anhydrous ethanol and water, and the volume ratio is 11:1; The reaction mass ratio of the thermal conductive filler and 1H,1H,2H,2H - perfluorodecyltrimethoxysilane is 0.5:1.4;

[0055] Step S2: Mix polymethylhydrosiloxane, dodecafluorooctyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and Kastredt catalyst, and stir at 30°C for 5 min to obtain an organosilicon copolymer; The reaction mass ratio of polymethylhydrosiloxane, dodecafluorooctyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and Kastredt catalyst is 15:1:1:1:0.1;

[0056] Step S3: Pre-mix 110 g of bisphenol A epoxy resin and 45 g of silicone copolymer, stir and react at 90 °C for 5 min, then add 40 g of modified thermal conductive filler, 30 g of m-phenylenediamine, 25 g of aluminum hydroxide flame retardant, and 20 g of toughening agent, and continue stirring for 8 min to obtain the encapsulation adhesive;

[0057] Step S4: First, take a single-sided FPC board as the encapsulation substrate, then weld the dual-color LED chips at the specified positions on the FPC printed circuit board, cure with silver paste, and perform circuit connection and preliminary testing after secondary curing with black glue to obtain the COB encapsulation module; evenly coat the encapsulation adhesive on the chips and circuits, and cure at a constant temperature to form the encapsulation structure; Silver paste curing parameters: Cure at 130 °C for 60 min; Black glue secondary curing parameters: Cure at 180 °C for 50 min; Constant temperature curing parameters: Cure at 150 °C for 50 min.

[0058] Detection test:

[0059] Thermal conductivity test: Put the encapsulation adhesive into a mold and cure at 150 °C for 50 min to obtain a specimen with dimensions of 50×40×3 mm. Use a TC3000 thermal conductivity meter produced by XATECH Company of China to test the specimen, and take the average value after repeating the thermal conductivity test 5 times.

[0060] Water absorption test: Put the encapsulation adhesive into a mold and cure at 150 °C for 50 min to obtain a specimen with dimensions of 50×40×3 mm. Immerse the specimen in distilled water at 25 °C for 50 h, weigh the mass of the specimen before and after immersion respectively, and then substitute the data into the formula to obtain the water absorption rate. The results are shown in the following table:

[0061]

[0062] Conclusion: The dosages in Examples 1 - 3 remain unchanged, only some reaction parameters are modified. From the experimental data, it can be seen that the various properties of the specimens do not show obvious fluctuations.

[0063] Comparative Example 1: Replace the modified thermal conductive filler with silicon carbide filler, and the rest is the same as in Example 1. From the experimental data, it can be seen that compared with Example 1, the thermal conductivity is reduced to 1.08 W / (m·K), and the water absorption rate is increased to 0.093%. The reason for the analysis is as follows: In the present invention, through coating, ball milling, and modification of silicon carbide filler and boron nitride filler, a modified thermal conductive filler with good dispersibility is obtained. Therefore, after replacing it with a conventional silicon carbide filler, the dispersibility becomes poor, the thermal conductivity decreases, and the hydrophobic and moisture-proof properties also become poor.

[0064] Comparative Example 2: The silicone copolymer was removed, and the rest was the same as in Example 1. From the experimental data, it can be seen that compared with Example 1, the water absorption rate increased to 0.121%. The reason is as follows: The silicon skeleton and fluorine groups in the silicone copolymer can significantly improve the hydrophobicity of the material, and the introduction of epoxy groups and amino groups can promote the subsequent curing and crosslinking of the material, effectively preventing the diffusion and penetration of water molecules and enhancing the moisture-proof performance of the encapsulating adhesive; therefore, after removing the silicone copolymer, the water absorption rate increased.

[0065] Comparative Example 3: The reaction mass ratio of dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, and glycidyl methacrylate was adjusted from (3 - 4):1:(1.7 - 2.0) to 1:1:1, and the rest was the same as in Example 1. From the experimental data, it can be seen that compared with Example 1, the water absorption rate increased to 0.076%. The reason is as follows: Adjusting the amounts of dodecafluoroheptyl methacrylate and glycidyl methacrylate to be smaller will result in a reduction in hydrophobic fluorine groups and a decrease in the degree of molecular crosslinking, so the moisture-proof performance of the encapsulating adhesive decreases and the water absorption rate increases.

[0066] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0067] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An encapsulating adhesive for a constant - voltage two - color COB encapsulation process, characterized in that: The content of each component of the encapsulating adhesive is as follows: in terms of parts by mass, 90-110 parts of bisphenol A epoxy resin, 35-45 parts of silicone copolymer, 30-40 parts of modified thermal conductive filler, 20-30 parts of curing agent, 15-25 parts of flame retardant, and 10-20 parts of toughening agent; the curing agent is m-phenylenediamine, and the flame retardant is aluminum hydroxide flame retardant.

2. The preparation process of the encapsulating glue for a constant-pressure two-color COB encapsulation process according to claim 1, characterized in that: It includes the following steps: Step S1: Under a nitrogen environment, mix the modified silicon carbide filler and the modified boron nitride filler, and ball mill at a speed of 150-250 rpm / min for 3-5 h to obtain a thermal conductive filler; then dissolve the thermal conductive filler in a mixed solvent, stir evenly, heat up to 40-50 °C, and then add 1H,1H,2H,2H-perfluorodecyltrimethoxysilane and react for 25-30 h. After the reaction, centrifuge, wash, and dry to obtain the modified thermal conductive filler; Step S2: Mix polymethylhydrosiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and Kastredt catalyst, and stir at 25-30 °C for 3-5 min to obtain a silicone copolymer; Step S3: Pre-mix bisphenol A epoxy resin and the silicone copolymer, stir and react at 80-90 °C for 3-5 min, then add the modified thermal conductive filler, curing agent, flame retardant, and toughening agent, and continue to stir for 5-8 min to obtain the encapsulating adhesive.

3. The preparation process of the encapsulation adhesive for a constant-pressure two-color COB encapsulation process according to claim 2, characterized in that: In step S1, the ball-to-material ratio of ball milling is (5-7):1; the mixed solvent is composed of absolute ethanol and water, and the volume ratio is (10-12):1; the reaction mass ratio of the thermal conductive filler and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is 0.5:(1.3-1.5).

4. The preparation process of the encapsulation adhesive for a constant-voltage two-color COB encapsulation process according to claim 2, characterized in that: In step S1, the preparation process of the modified silicon carbide filler is as follows: lay the silicon carbide filler evenly and heat it up to 700-750 °C at a heating rate of 5 °C / min and keep it warm for 2.5-3.0 h, 900-950 °C and keep it warm for 2.5-3.0 h, 1100-1200 °C and keep it warm for 1.5-2.0 h to obtain the modified silicon carbide filler.

5. The preparation process of the encapsulation adhesive for a constant-voltage two-color COB encapsulation process according to claim 2, wherein: In step S1, the preparation process of the modified boron nitride filler is as follows: mix absolute ethanol, ammonia water, and deionized water, stir evenly to obtain a mixed solution, then add the boron nitride filler, continue to stir for 30-40 min, and then slowly dropwise add tetraethyl orthosilicate. After the dropping is completed, continue to stir and react for 2-3 h. After the reaction, centrifuge, wash, and dry to obtain the modified boron nitride filler.

6. The preparation process of the encapsulation adhesive for the constant-pressure two-color COB encapsulation process according to claim 5, characterized in that: The reaction mass ratio of absolute ethanol, ammonia water, deionized water, boron nitride filler, and tetraethyl orthosilicate is 100:4:3:0.25:(1.2-2.0).

7. The preparation process of the encapsulation adhesive for a constant-pressure two-color COB encapsulation process according to claim 2, characterized in that: In step S2, the reaction mass ratio of polymethylhydrosiloxane, dodecafluoroheptyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, and Kastredt catalyst is 15:(3-4):1:(1.7-2.0):0.

1.

8. A constant-voltage dual-color COB packaging process, characterized in that: Prepared by using the encapsulation adhesive described in claim 1, including the following steps: First, take a single-sided FPC board as the encapsulation substrate, then weld the two-color LED wafers at the specified positions on the FPC printed circuit board, cure with silver paste, and after secondary curing of the black glue, perform circuit connection and preliminary detection to obtain a COB encapsulation module; uniformly coat the encapsulation adhesive onto the chips and circuits, and cure at a constant temperature to form an encapsulation structure.

9. A constant voltage two-color COB packaging process according to claim 8, characterized in that: Silver paste curing parameters: Cure at 120 - 130 °C for 50 - 60 min; Black glue secondary curing parameters: Cure at 150 - 180 °C for 30 - 50 min; Constant temperature curing parameters: Cure at 130 - 150 °C for 40 - 50 min.

Images