LED packaging process with anti-reflection cup to avoid glue overflow

Abstract

This invention provides an LED packaging process with a built-in reflector to avoid the effects of adhesive overflow, comprising the following steps: Step S1: Prepare a carrier substrate and dehumidify it to remove surface moisture. Step S2: Apply die-bonding material to the surface of the carrier substrate, place the LED chip on the die-bonding material surface, and bake to cure, thus connecting the LED chip to the carrier substrate. Step S3: Use a wire bonding machine to wire bond the LED chip electrodes to the pads of the carrier substrate to form positive and negative electrode leads. Step S4: Place the carrier substrate with die bonding and wire bonding completed into an injection mold. The injection mold has cavities at the positions corresponding to the LED chip and the wire bonding. Injection molding material is injected into the injection cavity of the injection mold using an injection molding machine. Step S5: The injection molding material cools and cures in the injection mold, forming a reflector structure to obtain a semi-finished LED product. Step S6: Perform secondary adhesive dispensing and encapsulation in the inner cavity of the reflector. After dispensing, bake to cure, forming a protective layer for the LED chip.

Description

Technical Field

[0001] This invention relates to the field of LED semiconductor packaging technology, and in particular to an LED packaging process with a built-in reflector to avoid the effects of excess adhesive. Background Technology

[0002] Existing LED brackets with integrated reflectors utilize thermosetting epoxy resin or thermoplastic plastics with excellent flowability to make the reflectors. A drawback of this technology is that the high injection pressure easily causes significant glue overflow or glue vapor contamination at the die-bonding and wire bonding locations on the inner pads or PCB pads of the LED reflector bracket during injection molding. After injection molding, the LED bracket with integrated reflectors needs to be cleaned again to remove the overflow or glue vapor. However, when using chemical cleaning, some areas may not be thoroughly cleaned, or chemical residue may remain inside the LED reflector. This contamination at the die-bonding and wire bonding locations on the inner pads or PCB pads of the LED reflector bracket is a significant problem. There may still be a small amount of glue overflow or glue gas contamination. At the same time, the cleaning solution will cause secondary damage to the reflectivity or surface smoothness of the reflector cup. (During the quality inspection process, it is difficult to detect the small amount of glue gas contamination on the LED bracket pads and the residual solution inside the LED reflector cup. At the same time, it is also difficult to detect the secondary damage to the reflectivity or surface smoothness of the reflector cup caused by the cleaning solution.) There is a large risk of quality defects. When delivered to downstream LED packaging manufacturers, these defects may not be detected in time during incoming material inspection. As a result, downstream manufacturers are very likely to cause poor die bonding, poor wire bonding, poor reflector cup smoothness and other quality abnormalities in the die bonding and wire bonding processes. This quality problem will cause great economic losses. Summary of the Invention

[0003] To overcome the above problems, this invention provides an LED packaging process with a built-in reflector to avoid the effects of adhesive overflow. The specific technical solution is as follows:

[0004] The LED packaging process with its built-in reflector to prevent excess adhesive from affecting the process includes the following steps:

[0005] Step S1, Substrate Pretreatment: Prepare the substrate and dehumidify it;

[0006] Step S2, die bonding: Apply die bonding material to the surface of the carrier substrate, place the LED chip on the surface of the die bonding material and bake to cure, thereby achieving the connection between the LED chip and the carrier substrate;

[0007] Step S3, Injection Molding: The carrier substrate after die bonding is placed into the injection mold, so that the area to be injected on the carrier substrate is in close contact with the injection cavity. A cavity is provided on the injection mold corresponding to the position of the LED chip. The LED chip is housed in the cavity. The injection molding machine injects the injection material into the injection cavity, and the injection is carried out until the injection material is in close contact with the area to be injected on the carrier substrate.

[0008] Step S4, Curing: The injection molding material is heated and cured in the injection mold, forming a reflector cup in the injection area of ​​the substrate, thus obtaining a semi-finished LED product;

[0009] Step S5, Secondary dispensing: Secondary dispensing and encapsulation are performed inside the reflector cup cavity. After dispensing, the LED is baked and cured to form a protective layer for the LED chip, resulting in the finished LED product.

[0010] In some embodiments, a hollow boss is provided inside the injection molding cavity, and the interior of the hollow boss is formed as a cavity to prevent air leakage.

[0011] When the mold is closed, the carrier substrate abuts against the top end face of the injection mold. The area to be injected on the carrier substrate corresponds to the injection cavity. The LED chip is housed in the cavity, and the LED chip does not contact the inner wall of the cavity.

[0012] In some embodiments, the injection molding material is a thermosetting epoxy resin, a thermoplastic, or silicone.

[0013] In some embodiments, the carrier substrate in step S1 is a planar LED bracket or a planar PCB board.

[0014] In some embodiments, when the LED chip in step S2 is a positively mounted chip, the die bonding material is insulating adhesive, conductive adhesive, or solder paste.

[0015] The bottom of the positive-mounted wafer is mounted on the pads of the carrier substrate by a die bonding material, and the positive and negative electrodes at the top are connected to the positive and negative electrode pads of the carrier substrate by bonding wires, respectively.

[0016] During injection molding, the cavity of the injection mold is designed to accommodate the wafer, bonding wire, and die bonder. The injection material is isolated from the wafer and bonding wire by the outer wall of the hollow boss, so that the injection material does not come into contact with the wafer and bonding wire.

[0017] In some embodiments, the wire used in the wire bonding machine is copper wire or alloy wire.

[0018] In some embodiments, when the LED chip in step S2 is a flip chip, the die bonding material is conductive adhesive or solder paste, and the process steps are executed sequentially from step S1 to step S5 to complete the packaging process.

[0019] The positive and negative electrodes of the flip chip are connected to the positive electrode pad and the negative electrode pad respectively through die bonding material;

[0020] The cavity of the injection mold is designed to accommodate flip chips, conductive adhesive, or solder paste. During injection molding, the injection material is isolated from the flip chip and die bond material by the outer wall of the hollow boss, so that the injection material does not come into contact with the flip chip and die bond material.

[0021] In some embodiments, in step S5, the adhesive material for the secondary dispensing is liquid epoxy resin, liquid epoxy resin mixed with fluorescent powder, or silicone.

[0022] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention adopts a process of die bonding followed by injection molding, or die bonding followed by wire bonding followed by injection molding. Even if there is slight glue overflow inside the LED bracket light-emitting cup or on the inner surface of the PCB pad after injection molding, it will not be affected at all, and there is no secondary damage to the surface finish of the reflector. This structural design and production method effectively solves the problems of glue overflow, glue gas contamination, rough reflector, and unclean surface that are prone to occur in the production process of existing LED brackets or PCBs. It avoids problems such as poor die bonding, poor wire bonding, and poor insulation caused by contamination from the source, and significantly improves product consistency, stability and service life. At the same time, it simplifies the production process, eliminates the need for secondary cleaning and complex testing, effectively reduces production costs and improves production efficiency, and is more suitable for large-scale automated production, with strong practicality and market competitiveness. Attached Figure Description

[0023] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0024] Figure 1 This is a schematic diagram of the structure of the carrier substrate at a first angle provided in an embodiment of this application.

[0025] Figure 2 This is a schematic diagram of the second angle of the carrier substrate provided in an embodiment of this application.

[0026] Figure 3 This is a schematic diagram of the connection between the mounted wafer and the carrier substrate provided in an embodiment of this application.

[0027] Figure 4 This is a schematic diagram of a first angle showing the connection between a positively mounted wafer and a substrate pad via bonding wires, as provided in an embodiment of this application.

[0028] Figure 5 This is a schematic diagram of a second angle showing the structure of a positively mounted wafer connected to the substrate pads via bonding wires, as provided in an embodiment of this application.

[0029] Figure 6 A schematic diagram of the structure of an injection mold provided for an embodiment of this application.

[0030] Figure 7 A schematic diagram of the structure of an LED semi-finished product mounted on an injection mold, provided for an embodiment of this application.

[0031] Figure 8 for Figure 6 Cross-sectional view at point BB.

[0032] Figure 9 A schematic diagram of the structure of the injection-molded reflector on the carrier substrate provided in the embodiments of this application.

[0033] Figure 10 for Figure 9 Cross-sectional view at point CC.

[0034] Figure 11 A schematic diagram of the secondary adhesive injection structure inside the reflector cup is provided for the embodiments of this application.

[0035] Figure 12 for Figure 11 Cross-sectional view at point DD.

[0036] Figure 13 This is a schematic diagram of the first angle at which the flip chip is connected to the carrier substrate, as provided in an embodiment of this application.

[0037] Figure 14 This is a schematic diagram of the second angle of connection between the flip chip and the carrier substrate, provided for an embodiment of this application.

[0038] The attached figures are labeled as follows:

[0039] 1. Supporting substrate; 11. Positive electrode pad; 12. Negative electrode pad;

[0040] 2. LED chip; 21. LED chip positive electrode; 22. LED chip negative electrode;

[0041] 3. Wire bonding;

[0042] 4. Injection mold; 41. Boss; 411. Cavity; 42. Injection cavity.

[0043] 5. Reflector cup; 51. Reflector cup cavity;

[0044] 6. Adhesive liquid. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Of course, the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0046] The embodiments of this application provide an LED packaging process with a built-in reflector to avoid the influence of excess adhesive, including the following steps:

[0047] Before introducing the process of this application, it should be noted that the LED chip 2 includes: a standard chip and a flip chip.

[0048] Please see Figure 1 , Figure 2 , Figure 1 This is a schematic diagram of the structure of the carrier substrate 1 at a first angle provided in an embodiment of this application. Figure 2 A schematic diagram of the structure of the carrier substrate 1 at a second angle provided in an embodiment of this application.

[0049] When LED chip 2 is a standard-mount chip, the packaging process includes the following steps:

[0050] Step S1, Substrate Pretreatment: Prepare the carrier substrate 1 and dehumidify it to remove surface moisture. Specifically, select a planar LED bracket or a planar PCB board as the carrier substrate 1, and dehumidify it to remove moisture adhering to its surface. This prevents moisture from affecting the subsequent bonding strength and ensures the reliability of the connection between the LED chip 2 and the carrier substrate 1.

[0051] The dehumidification treatment method can be any of the following: the substrate 1 can be placed in a constant temperature oven at 120℃-150℃ and baked for 10-60 minutes, or treated in a vacuum dehumidification chamber with a vacuum degree of -0.08Mpa--0.1MPa for 5-15 minutes. Both methods can achieve sufficient drying of the substrate 1 and meet the requirements of subsequent processes.

[0052] Please see Figure 3 , Figure 3 This is a schematic diagram of the connection between the mounted wafer and the carrier substrate 1 provided in an embodiment of this application.

[0053] Step S2, Die Bonding: A die bonding material is applied to the surface of the carrier substrate 1. The LED chip 2 is placed on the surface of the die bonding material and baked to cure, thereby achieving a fixed connection between the LED chip 2 and the carrier substrate 1. Specifically, a die bonding material is uniformly applied to the surface of the pads on the carrier substrate 1 using a fully automatic die bonding machine. The die bonding material can be conductive adhesive, insulating adhesive, or solder paste. The LED chip 2 is precisely placed on the surface of the die bonding material, and then the carrier substrate 1 is sent to a baking device for baking and curing according to the conventional LED packaging process conditions (baking temperature 80℃~150℃, holding time 5~20min), so that the LED chip 2 and the carrier substrate 1 form a stable and reliable fixed bond.

[0054] Please see Figure 4 and Figure 5 , Figure 4 This is a schematic diagram of the structure of the upright wafer connected to the pads of the carrier substrate 1 via bonding wire 3, according to an embodiment of this application, at a first angle. Figure 5 This is a schematic diagram of the structure of the upright wafer provided in the embodiment of this application, which is connected to the pad of the carrier substrate 1 by the bonding wire 3 at a second angle.

[0055] When LED chip 2 is a standard chip, after step S2 is completed, wire bonding operation is also required. The die bonding material is insulating glue, conductive glue or solder paste.

[0056] Wire bonding: The two ends of the wire bonding 3 are bonded to the electrodes of the wafer and the pads of the substrate 1 respectively by the wire bonding machine; when the mold is closed, the cavity 411 of the injection mold 4 is set to correspond to the wafer and the wire bonding 3; during injection molding, the injection material is isolated from the wafer and the wire bonding 3 by the outer wall of the hollow boss 41, so that the injection material does not come into contact with the wafer and the wire bonding 3.

[0057] For example, the wire 3 used in the wire bonding machine is copper wire or alloy wire.

[0058] Specifically, a high-precision wire bonding machine is used to complete electrode bonding, forming a complete conductive circuit and achieving a stable electrical connection between the LED chip 2 and the carrier substrate 1. The wire bonding machine uses copper wire or alloy wire as the bonding wire to ensure low impedance and high stability of the conductive circuit after bonding. The positive electrode 21 and negative electrode 22 of the upright chip are bonded to the positive electrode pad 11 and negative electrode pad 12 of the carrier substrate 1 respectively through the wire bonding 3. The method of independent bonding of positive and negative electrodes can effectively avoid the risk of short circuit between positive and negative electrodes, improve the bonding yield of the wire bonding 3 and the electrical safety performance of the product, and avoid failure problems such as poor soldering or detachment of the wire bonding 3 during long-term use of the product.

[0059] Please see Figure 6 , Figure 7 as well as Figure 8 , Figure 6 This is a schematic diagram of the structure of the injection mold 4 provided in the embodiments of this application. Figure 7 This is a schematic diagram of the structure of the LED semi-finished product installed on the injection mold 4 according to an embodiment of this application, and Figure 7 It shows Figure 6 Cross-sectional view at point AA. Figure 8 for Figure 6 Cross-sectional view at point BB.

[0060] Step S3, Injection Molding: The carrier substrate 1, after die bonding and wire bonding, is placed into the injection mold 4, so that the area to be injected on the carrier substrate 1 corresponds to and fits into the injection cavity 42. The injection mold 4 is provided with a cavity 411 corresponding to the position of the LED chip 2. The LED chip 2 and the wire bonding 3 are housed in the cavity 411. The injection molding machine injects injection molding material into the injection cavity 42 until the injection molding material completely fills the injection cavity 42 and fits tightly against the area to be injected on the carrier substrate 1.

[0061] The injection mold 4 has an injection cavity 42, within which a hollow boss 41 with a hollow structure is provided, forming a recessed cavity 411. During mold closing, the LED chip 2 and the bonding wire 3 are respectively housed within the recessed cavity 411. During injection molding, the injection material does not come into contact with the LED chip 2 or the bonding wire 3, preventing the injection mold 4 from damaging the LED chip 2 or the bonding wire 3 during mold closing. Simultaneously, it completely eliminates the problem of molten injection material eroding the bonding wire 3 and overflowing adhesive contaminating the LED chip 2 during injection molding. This provides a reliable structural guarantee for achieving the core objective of ensuring that overflowing adhesive does not affect product quality, effectively improving the stability and production yield of the injection molding process.

[0062] The injection molding material can be thermosetting epoxy resin or thermoplastic plastic. Using an injection molding machine and a sealing press extrusion rod, the injection molding material is extruded into the injection cavity 42 through the mold inlet and runner. After being heated and becoming semi-liquid, the injection molding material fills the entire injection cavity 42 of the injection mold 4 under the pressure of the extrusion rod, thus forming the reflector cup 5 and the reflector cup cavity 51 inside the reflector cup 5. Thermosetting epoxy resin or thermoplastic plastic possesses excellent molding precision, structural stability, and light reflection efficiency. It is compatible with mainstream injection molding equipment in the industry, and the integrated molding of the reflector cup 5 can be achieved without the need for additional dedicated production line equipment. The cured reflector cup 5 has high dimensional accuracy and stable reflective performance, effectively improving the light output efficiency and optical consistency of LED products.

[0063] Please see Figure 9 and Figure 10 , Figure 9 This is a schematic diagram of the structure of the reflector 5 injection-molded on the carrier substrate 1 provided in the embodiments of this application. Figure 10 for Figure 9 Cross-sectional view at point CC.

[0064] Step S4, Curing: The injection molding material is heated or cooled and cured in the injection mold 4 to form an integrated reflector cup 5, thus obtaining an LED semi-finished product. Specifically, the filled injection molding material is kept at a constant temperature and pressure in the injection mold 4 for several minutes and then completely cured, forming an integrated reflector cup 5 on the carrier substrate 1, thus obtaining an LED semi-finished product with a built-in reflector cup.

[0065] When LED chip 2 is a flip chip, the packaging process is as follows:

[0066] Please see Figure 13 and Figure 14 Combined Figure 3 , Figure 13 This is a schematic diagram of the structure at the first angle of connection between the flip chip and the carrier substrate 1, as provided in an embodiment of this application. Figure 14 This is a schematic diagram of the second angle of connection between the flip-chip and the carrier substrate 1, as provided in an embodiment of this application.

[0067] When the LED chip 2 is a flip chip, the positive and negative electrodes of the flip chip are directly integrated on the bottom of the LED chip 2, and can be directly bonded and fixed to the corresponding pads of the carrier substrate 1 to form an electrical connection. Therefore, the flip chip does not require wire bonding. By sequentially executing steps S1 to S5, the encapsulation can be completed. The process provided in this application embodiment has excellent compatibility with both standard and flip-chip LED chips 2, which are the two mainstream types in the industry. For the structural characteristics of the two types of chips, only the wire bonding process needs to be adjusted to complete the adaptation. There is no need to change the process flow, injection mold and production equipment, which greatly reduces the time and material costs of production line changeover, improves production flexibility, and covers the chip types of most LED products with built-in reflectors in the industry, which greatly broadens the application scope and industrialization value of this process.

[0068] The packaging process steps for flip chips are as follows:

[0069] Step S1, Substrate pretreatment: Prepare the carrier substrate 1 and dehumidify it;

[0070] Step S2, die bonding: Apply die bonding material to the surface of the carrier substrate 1, place the LED chip 2 on the surface of the die bonding material and bake to cure, thereby achieving the connection between the LED chip 2 and the carrier substrate 1.

[0071] Step S3, Injection Molding: The carrier substrate 1 after die bonding is placed into the injection mold 4, so that the area to be injected on the carrier substrate 1 is in contact with the injection cavity 42. The injection mold 4 is provided with a cavity 411 corresponding to the position of the LED chip 2. The LED chip 2 is housed in the cavity 411. The injection molding machine injects injection material into the injection cavity 42 until the injection material completely fills the injection cavity 42 and is in close contact with the area to be injected on the carrier substrate 1.

[0072] Step S4, Curing: The injection molding material is heated or cooled and cured in the injection mold 4, forming a reflector cup 5 in the injection area of ​​the supporting substrate 1, thus obtaining an LED semi-finished product;

[0073] Step S5, Secondary dispensing: Secondary dispensing and encapsulation are performed inside the reflector cup cavity 51. After dispensing, the material is baked and cured to form a protective layer covering the LED chip 2, thus obtaining the finished LED product.

[0074] The process provided in this application, through an integrated process flow, ensures that even if excessive injection pressure leads to overflow or glue spillage during production, it has no impact on LED packaging. This eliminates the problem of glue contamination in the die-bonding and wire-bonding areas from the source, improving product yield and production stability. Furthermore, it eliminates the need for secondary chemical cleaning of the LED bracket or PCB board pads, avoiding problems such as pad oxidation, reflector damage, and increased surface roughness caused by incomplete or excessive chemical cleaning, thus reducing batch defect rates and the risk of latent failures. The glue-free and contamination-free LED bracket structure effectively ensures that the die-bonding and wire-bonding areas are clean, flat, and free of insulating layers, resulting in higher and more stable die-bonding bond strength and a higher success rate in achieving wire bonding pull strength targets, significantly improving the reliability and lifespan of LED packaged products. It simplifies the complex cleaning, inspection, and rework processes of existing technologies, shortens the production cycle, reduces production costs, minimizes economic losses due to contamination, and is more suitable for large-scale automated mass production. The manufactured LED brackets or PCBs are free of residual colloids and hidden contaminants. When they flow into the downstream packaging stage, no additional complex incoming material inspection procedures are required, significantly reducing the inspection costs and production risks for downstream manufacturers and improving the overall stability and economic efficiency of the supply chain. The integrated anti-overflow injection molding structure makes the LED brackets or PCBs more stable, with more consistent reflective performance and more reliable electrical connections. Compared to existing LED brackets that are easily contaminated and difficult to clean, they are more practical and have higher market competitiveness.

[0075] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An LED packaging process with a built-in reflector to avoid the effects of excess adhesive, characterized in that, Includes the following steps: Step S1, Substrate pretreatment: Prepare the carrier substrate (1) and dehumidify it; Step S2, die bonding: Apply die bonding material to the surface of the carrier substrate (1), place the LED chip (2) on the surface of the die bonding material and bake to cure, thereby achieving the connection between the LED chip (2) and the carrier substrate (1); Step S3, Injection Molding: The carrier substrate (1) after die bonding is placed into the injection mold (4), so that the area to be injected on the carrier substrate (1) is in contact with the injection cavity (42). The injection mold (4) is provided with a cavity (411) corresponding to the position of the LED chip (2). The LED chip (2) is housed in the cavity (411). The injection molding machine injects the injection molding material into the injection cavity (42) until the injection molding material is in close contact with the area to be injected on the carrier substrate (1). Step S4, Curing: The injection material is heated and cured in the injection mold (4), forming a reflector cup (5) in the injection area of ​​the substrate (1) to be injected, thus obtaining an LED semi-finished product; Step S5, Secondary dispensing: Secondary dispensing and encapsulation are performed in the reflector cup cavity (51). After dispensing, baking and curing are performed to form a protective layer for the LED chip (2) and obtain the LED finished product.

2. The LED packaging process with a built-in reflector to avoid the influence of excess adhesive as described in claim 1, characterized in that, A hollow boss (41) is provided inside the injection molding cavity (42), and the hollow boss (41) forms the cavity (411) inside. When the mold is closed, the carrier substrate (1) abuts against the top end face of the injection mold (4), the injection area of ​​the carrier substrate (1) corresponds to the injection cavity (42), the LED chip (2) is housed in the cavity (411), and the LED chip (2) does not contact the inner wall of the cavity (411).

3. The LED packaging process with a built-in reflector to avoid the influence of excess adhesive as described in claim 2, characterized in that, The injection molding material is a thermosetting epoxy resin, thermoplastic plastic, or silicone.

4. The LED packaging process with a built-in reflector to avoid the influence of excess adhesive, as described in claim 1, is characterized in that... The carrier substrate (1) in step S1 is a planar LED bracket or a planar PCB board.

5. The LED packaging process with a built-in reflector to avoid the influence of excess adhesive as described in claim 1, characterized in that, When the LED chip (2) in step S2 is a standard-mounted chip, the die bonding material is insulating adhesive, conductive adhesive or solder paste; The bottom of the positive-mounted wafer is mounted on the pads of the carrier substrate (1) by a die bonding material, and the positive electrode (21) and negative electrode (22) at the top are connected to the positive electrode pad (11) and negative electrode pad (12) of the carrier substrate (1) by bonding wires (3), respectively. During injection molding, the cavity (411) of the injection mold (4) is set to correspond to the wafer, the bonding wire (3) and the die bonding material. The injection material is isolated from the wafer and the bonding wire (3) by the outer wall of the hollow boss (41), so that the injection material does not come into contact with the wafer and the bonding wire (3).

6. The LED packaging process with a built-in reflector to avoid the influence of excess adhesive as described in claim 5, characterized in that, The wire (3) of the wire bonding machine is a copper wire or an alloy wire.

7. The LED packaging process with a built-in reflector to avoid the influence of excess adhesive as described in claim 1, characterized in that, When the LED chip (2) in step S2 is a flip chip, the die bonding material is conductive adhesive or solder paste, and the process steps are executed sequentially from step S1 to step S5 to complete the packaging process. The positive and negative electrodes at the bottom of the flip chip are connected to the positive electrode pad (11) and the negative electrode pad (12) respectively through die bonding material. The cavity (411) of the injection mold (4) is set to correspond to the flip chip and the die bond material. During injection molding, the injection material is isolated from the flip chip and the die bond material by the outer wall of the hollow boss (41), so that the injection material and the flip chip and the die bond material do not come into contact with each other.

8. The LED packaging process with a built-in reflector to avoid the influence of excess adhesive, as described in any one of claims 1 to 7, is characterized in that... In step S5, the adhesive liquid (6) used for secondary dispensing is made of liquid epoxy resin, liquid epoxy resin mixed with fluorescent powder, or silicone.

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