Inverted LED lamp bead preparation process

Abstract

The inverted LED lamp bead preparation process comprises the steps of bowl-shaped base preparation, metal substrate pretreatment, support assembly, die bonding, glue sealing and the like, the mechanical strength and stability of a metal substrate and the binding force between the metal substrate and primer are enhanced through metal substrate pretreatment, and therefore the fracture resistance of the whole LED lamp bead structure is improved; the risk that the support is separated or damaged due to external stress is reduced through the support assembly design, the external force applied to the LED lamp bead is effectively dispersed through control of the die bonding process, local stress concentration is reduced, the flexibility and the external impact resistance of the whole structure of the LED lamp bead are improved through glue sealing treatment, and the service life of the LED lamp bead is prolonged. Therefore, a plurality of improvements are carried out on the structure and the process to achieve the purpose of remarkably improving the anti-fracture performance of the LED lamp bead.

Description

Technical Field

[0001] The present invention relates to the technical field of LED packaging, and specifically to a preparation process for flip-chip LED lamp beads. Background Art

[0002] With the development of LED technology, flip-chip LED lamp beads are widely used due to their advantages such as high efficiency and high brightness. An LED lamp bead includes an LED chip and an LED lamp bead bracket. The LED lamp bead bracket is the bottom base of the LED lamp bead before encapsulation. Based on the LED lamp bead bracket, the LED chip is fixed in, positive and negative electrodes are soldered, and then a one-time encapsulation is carried out through encapsulation glue to form the final LED lamp bead product. However, in the encapsulation process of existing flip-chip LED lamp beads, problems such as breakage and cracks are likely to occur in the lamp beads due to reasons such as thermal stress, external impact, or uneven glue layer, affecting their service life and reliability. Although there are various improvement methods in the prior art, most of them focus on the optimization of optical performance while neglecting the improvement of structural strength. Summary of the Invention

[0003] To solve the above problems, the present invention provides a preparation process for flip-chip LED lamp beads, including the following steps:

[0004] Preparing a bowl-shaped base: A bowl-shaped base is obtained through an injection molding process. The bowl-shaped base is made of epoxy resin or polyurethane resin. The bowl-shaped base is provided with a first stepped groove and a second stepped groove arranged in parallel along its length direction. A partition strip is provided between the first stepped groove and the second stepped groove of the bowl-shaped base. The partition strip can not only isolate electricity, share part of the external force, and disperse stress concentration points, but also limit the relative movement of the L-shaped first substrate and the L-shaped second substrate, avoiding bracket fracture caused by vibration or impact, and further improving the stability of the LED lamp bead; The connection between the partition strip and the bowl-shaped base adopts a smooth transition design, which can further reduce stress concentration points and better resist external force impact; Reinforcing ribs are provided around the first stepped groove and the second stepped groove inside the bowl-shaped base. By setting the reinforcing ribs, the external force can be effectively dispersed and local stress concentration can be reduced; The bowl-shaped base is provided with a first positioning convex block and a second positioning convex block along the first stepped groove, and a third positioning convex block and a fourth positioning convex block along the second stepped groove. A layer of thermal conductive silicone gasket is provided at the bottom of the bowl-shaped base. Adding the thermal conductive silicone gasket can, on the one hand, improve the heat dissipation efficiency of the bracket to prevent structural damage caused by local overheating, and on the other hand, provide a buffering effect when the bracket is subjected to external force impact, reducing the direct impact force; Limiting protrusions are provided at both ends of the bottom of the bowl-shaped base, and a silver-plated reflective cup is formed on the surface of the inner cavity of the bowl-shaped base; The silver-plated reflective cup has both high reflectivity and surface smoothness, reducing stress concentration points caused by defects in colloid filling.

[0005] Pretreatment of the metal substrate: The metal substrate is cut and polished to obtain L-shaped first substrates and L-shaped second substrates with the same shape. The metal substrate is made of any one of gold, silver, and copper. Using highly conductive and ductile metals such as gold, silver, or copper to prepare the L-shaped first substrates and L-shaped second substrates is beneficial for the LED lamp bead bracket to provide sufficient mechanical strength while ensuring electrical performance. There are limiting through holes on both the L-shaped first substrates and the L-shaped second substrates. The L-shaped first substrates are provided with first steps, first positioning grooves, and second positioning grooves. The L-shaped second substrates are provided with second steps, third positioning grooves, and fourth positioning grooves. The L-shaped first substrates and the L-shaped second substrates are electroless nickel-plated to form a nickel-plated layer on the surfaces of the L-shaped first substrates and the L-shaped second substrates. The nickel-plated layer can improve the surface hardness and corrosion resistance of the metal substrate. Then, the L-shaped first substrates and the L-shaped second substrates are successively cleaned, pickled, alkali-washed, and chemically activated to improve the adhesion of the bottom glue and ensure a strong bond between the metal substrate and the bottom glue, reducing the risk of delamination. The bottom glue is coated and heat-cured for standby;

[0006] Bracket assembly: Place the bowl-shaped base on the metal substrate. The L-shaped first substrate is fixed by the cooperation of the first step and the first stepped groove. The L-shaped second substrate is fixed by the cooperation of the second step and the second stepped groove. The first positioning bump cooperates with the first positioning groove. The second positioning bump cooperates with the second positioning groove. The third positioning bump cooperates with the third positioning groove. The fourth positioning bump cooperates with the fourth positioning groove. The limiting protrusion cooperates with the limiting through hole for fixation. In this way, the mechanical interlock enhances the bonding force between the metal substrate and the base, enabling the substrate to be firmly fixed on the bowl-shaped base and not easily displaced or detached even when subjected to external impacts, increasing the stability and fracture resistance of the entire assembly;

[0007] Die bonding: A solder paste film layer is coated on the die bonding area of the metal substrate. The flip-chip LED chip is placed, and the flip-chip accuracy is controlled within ±10 μm. It is fixedly connected to the metal substrate by reflow soldering in a nitrogen protection atmosphere. After reflow soldering, the cooling rate is controlled ≤ 3 °C / s. High-precision solder paste coating combined with nitrogen protection reflow soldering ensures uniform welding of the flip-chip and the metal substrate, reduces voids and false soldering, and improves the mechanical strength of the solder joints. Controlling the cooling rate avoids the increase in solder joint brittleness caused by rapid cooling and reduces the risk of microcracks in the bracket caused by thermal stress.

[0008] Encapsulation: Fill the reflector cup with quantum dot glue and perform primary curing. After cooling to 20 - 40 °C, then fill with silica gel and perform secondary curing to obtain the finished product. Using high-viscosity quantum dot glue can ensure that the colloid fits tightly with the reflector cup during primary curing, reducing interface voids; then using silica gel for secondary filling to form a buffer layer to absorb external impact energy.

[0009] Preferably, during the pretreatment of the metal substrate, first use isopropyl alcohol to ultrasonically clean the L-shaped first substrate and the L-shaped second substrate for 10 to 15 minutes, then perform pickling with 3 to 7 wt% dilute hydrochloric acid, and the soaking time is 5 to 10 minutes. Then perform alkali washing with 3 to 7 wt% sodium hydroxide solution, and the soaking time is 10 to 15 minutes. Then perform chemical activation with a mixed solution of sulfuric acid and hydrogen peroxide with a volume ratio of 2 to 4:1, and then use deionized water to rinse to completely remove the activation solution.

[0010] Preferably, during the pretreatment of the metal substrate, the underfill is selected from epoxy resin or polyurethane resin, and the coating thickness of the underfill is 10 to 20 μm. Place the metal substrate coated with the underfill in an oven for thermal curing treatment, the thermal curing temperature is 110 to 130 °C, and the time is 20 to 40 minutes.

[0011] Preferably, during the die bonding process, the coating thickness of the solder paste film layer is 80 to 100 μm, and the thickness error of the solder paste film layer is controlled within ±3 μm.

[0012] Preferably, during the die bonding process, the reflow soldering temperature is 260 to 290 °C and the time is 30 to 60 s.

[0013] Preferably, during the encapsulation process, use a quantum dot glue with a viscosity of 4000 to 6000 mPa·s (25 °C) to fill the reflector cup.

[0014] Preferably, during the encapsulation process, use a silica gel with a viscosity of 3000 to 5000 mPa·s (25 °C) to fill the reflector cup.

[0015] Preferably, during the encapsulation process, the primary curing temperature is 50 to 100 °C, and the temperature is increased step by step from 50 °C to 75 - 85 °C and then to 100 °C, and each stage is kept warm for 5 to 10 min. Using stepwise temperature increase during primary curing can gradually release the curing shrinkage stress of the quantum dot glue.

[0016] Preferably, during the encapsulation process, the secondary curing temperature is 100 to 120 °C, and the temperature is increased step by step from 100 °C to 105 - 115 °C and then to 120 °C, and each stage is kept warm for 5 to 10 min. Using stepwise temperature increase during secondary curing can optimize the crosslinking density of the silica gel to form a buffer layer, form a rigid and tough gradient structure with the quantum dot glue layer, and effectively resist bending and fracture.

[0017] The beneficial effects are that the present application significantly improves the anti-breaking performance of the LED lamp beads through the following aspects working together, including:

[0018] Metal Substrate Pretreatment: The L-shaped first substrate and the second substrate are electroless nickel-plated and then undergo a series of cleaning, pickling, alkali washing, and chemical activation processes. This not only enhances the corrosion resistance of the metal substrate surface but also improves the bonding strength with other materials (such as the bottom glue) in subsequent processes. In addition, applying the bottom glue and performing heat curing treatment further enhances the mechanical strength and stability of the metal substrate, contributing to improving the anti-breaking ability of the entire structure.

[0019] Bracket Assembly Design: Through the precise design of the fit between the first step, the second step, and the stepped groove, as well as the fixing method of the limiting protrusion and the limiting through-hole, a firm and stable connection between the bowl-shaped base and the metal substrate is ensured. This design reduces the risk of bracket separation or damage due to external stress, thereby indirectly improving the anti-breaking performance.

[0020] Die Bonding Process Control: During the die bonding process, the flip-chip accuracy (within ±10μm) and the thickness and error of the solder paste film layer (80 - 100μm, with the error controlled within ±3μm) are strictly controlled, ensuring good contact and welding quality between the chip and the metal substrate, effectively dispersing the external force applied to the LED lamp beads, reducing local stress concentration, and thus enhancing the overall anti-breaking ability.

[0021] Encapsulation Treatment: Quantum dot glue and silica gel are used to fill the reflector cup step by step, and the primary and secondary curing are carried out in a stepped heating manner. This encapsulation method not only provides good optical performance but also effectively protects the internal structure from the external environment. At the same time, it provides an additional buffer protection layer for the chip, increasing the flexibility of the overall structure and the ability to resist external impacts. Description of the Drawings

[0022] The drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. In the drawings:

[0023] Figure 1 is a schematic structural diagram of the first perspective of the present invention;

[0024] Figure 2 is a schematic structural diagram of the second perspective of the present invention;

[0025] Figure 3 is an exploded structural diagram of the present invention;

[0026] In the figure:

[0027] 1. Bowl-shaped base; 11. First stepped groove; 12. Second stepped groove; 13. Partition strip; 14. Limiting protrusion; 15. First positioning convex block; 16. Second positioning convex block; 17. Third positioning convex block; 18. Fourth positioning convex block;

[0028] 2. Metal substrate; 21. L-shaped first substrate; 211. First step; 212. First positioning groove; 213. Second positioning groove; 22. L-shaped second substrate; 221. Second step; 222. Third positioning groove; 223. Fourth positioning groove; 23. Limit through hole. Detailed implementation manners

[0029] The present invention will be further described in detail below in conjunction with specific embodiments, so that those skilled in the art can understand the present invention more clearly.

[0030] The following embodiments are only used to illustrate the present invention, but not to limit the scope of the present invention. Based on the specific embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the protection scope of the present invention.

[0031] In the embodiments of the present invention, unless otherwise specified, all raw material components are commercially available products well-known to those skilled in the art; in the embodiments of the present invention, unless specifically specified, the technical means used are all conventional means well-known to those skilled in the art.

[0032] Embodiment 1

[0033] As Figures 1 to 3 shown, Figure 1 is the first perspective structural schematic diagram of the present invention, Figure 2 is the second perspective structural schematic diagram of the present invention, Figure 3 is the exploded structural schematic diagram of the present invention. This embodiment provides a preparation process for flip-chip LED lamp beads, including the following steps:

[0034] Prepare the bowl-shaped base 1: Obtain the bowl-shaped base 1 through an injection molding process. The bowl-shaped base 1 is made of epoxy resin or polyurethane resin. The bowl-shaped base 1 is provided with a first stepped groove 11 and a second stepped groove 12 arranged in parallel along its length direction. The bowl-shaped base 1 is provided with a partition strip 13 between the first stepped groove 11 and the second stepped groove 12; the connection between the partition strip 13 and the bowl-shaped base 1 adopts a smooth transition design; the inside of the bowl-shaped base 1 is provided with reinforcing ribs around the first stepped groove 11 and the second stepped groove 12; the bowl-shaped base 1 is provided with a first positioning protrusion 15 and a second positioning protrusion 16 along the first stepped groove 11, and the bowl-shaped base 1 is provided with a third positioning protrusion 17 and a fourth positioning protrusion 18 along the second stepped groove 12. A layer of thermal conductive silicone gasket is provided at the bottom of the bowl-shaped base 1; limit protrusions 14 are provided at both ends of the bottom of the bowl-shaped base 1, and a reflective cup is formed by plating silver on the surface of the inner cavity of the bowl-shaped base 1;

[0035] Pretreatment of the metal substrate: The metal substrate 2 is cut and polished to obtain the L-shaped first substrate 21 and the L-shaped second substrate 22 with the same shape. The metal substrate 2 is made of any one of gold, silver, and copper. Limiting through holes 23 are provided on both the L-shaped first substrate 21 and the L-shaped second substrate 22. A first step 211, a first positioning groove 212, and a second positioning groove 213 are provided on the L-shaped first substrate 21. A second step 221, a third positioning groove 222, and a fourth positioning groove 223 are provided on the L-shaped second substrate 22. The L-shaped first substrate 21 and the L-shaped second substrate 22 are electroless nickel-plated to form a nickel-plated layer on the surfaces of the L-shaped first substrate 21 and the L-shaped second substrate 22. Then, the L-shaped first substrate 21 and the L-shaped second substrate 22 are successively subjected to cleaning, pickling, alkali washing, and chemical activation treatment, coated with a bottom adhesive, and heat-cured for standby. Specifically: First, the L-shaped first substrate 21 and the L-shaped second substrate 22 are ultrasonically cleaned with isopropyl alcohol for 10 minutes, then pickled with 3wt% dilute hydrochloric acid for 5 minutes, then alkali-washed with 3wt% sodium hydroxide solution for 10 minutes, then chemically activated with a mixed solution of sulfuric acid and hydrogen peroxide with a volume ratio of 2:1, and then rinsed with deionized water to completely remove the activation solution. The bottom adhesive is selected from epoxy resin or polyurethane resin, and the coating thickness of the bottom adhesive is 10μm. The metal substrate 2 coated with the bottom adhesive is placed in an oven for heat-curing treatment. The heat-curing temperature is 110°C and the time is 20 minutes.

[0036] Bracket assembly: Place the bowl-shaped base 1 on the metal substrate 2. The L-shaped first substrate 21 is fixed by fitting the first step 211 with the first stepped groove 11. The L-shaped second substrate 22 is fixed by fitting the second step 221 with the second stepped groove 12. The first positioning bump 15 is fitted with the first positioning groove 212. The second positioning bump 16 is fitted with the second positioning groove 213. The third positioning bump 17 is fitted with the third positioning groove 222. The fourth positioning bump 18 is fitted with the fourth positioning groove 223. The limiting protrusion 14 is fitted and fixed with the limiting through hole 23.

[0037] Die bonding: A solder paste film layer is coated on the die bonding area of the metal substrate 2. The coating thickness of the solder paste film layer is 80μm, and the thickness error of the solder paste film layer is controlled within ±3μm. The flip-chip LED chip is placed, and the flip-chip accuracy is controlled within ±10μm. It is fixedly connected to the metal substrate 2 by reflow soldering in a nitrogen protection atmosphere. The reflow soldering temperature is 260°C and the time is 30s. After reflow soldering, the cooling rate is controlled ≤3°C / s.

[0038] Potting: Fill the reflecting cup with quantum dot glue having a viscosity of 4000 mPa·s (25 °C) and perform primary curing. The primary curing temperature is 50 to 100 °C. Use stepwise heating to rise from 50 °C to 75 °C and then to 100 °C, with each stage maintained for 5 minutes. After cooling to 20 °C, fill with silicone glue having a viscosity of 3000 mPa·s (25 °C) and perform secondary curing. The secondary curing temperature is 100 to 120 °C. Use stepwise heating to rise from 100 °C to 105 °C and then to 120 °C, with each stage maintained for 5 minutes to obtain the finished product.

[0039] Example 2

[0040] As Figures 1 to 3 shown, Figure 1 is a schematic structural diagram of the first perspective of the present invention, Figure 2 is a schematic structural diagram of the second perspective of the present invention, Figure 3 is an exploded structural diagram of the present invention. This embodiment provides a preparation process for a flip-chip LED lamp bead, including the following steps:

[0041] Prepare the bowl-shaped base 1: Obtain the bowl-shaped base 1 through an injection molding process. The bowl-shaped base 1 is made of epoxy resin or polyurethane resin. The bowl-shaped base 1 is provided with a first stepped groove 11 and a second stepped groove 12 arranged in parallel along its length direction. The bowl-shaped base 1 is provided with a partition strip 13 between the first stepped groove 11 and the second stepped groove 12; the connection between the partition strip 13 and the bowl-shaped base 1 adopts a smooth transition design; the inside of the bowl-shaped base 1 is provided with reinforcing ribs around the first stepped groove 11 and the second stepped groove 12; the bowl-shaped base 1 is provided with a first positioning protrusion 15 and a second positioning protrusion 16 along the first stepped groove 11, and the bowl-shaped base 1 is provided with a third positioning protrusion 17 and a fourth positioning protrusion 18 along the second stepped groove 12. The bottom of the bowl-shaped base 1 is provided with a layer of thermal conductive silicone gasket; both ends of the bottom of the bowl-shaped base 1 are provided with limiting protrusions 14, and a reflecting cup is formed by plating silver on the surface of the inner cavity of the bowl-shaped base 1;

[0042] Pretreatment of the metal substrate: The metal substrate 2 is cut and polished to obtain the L-shaped first substrate 21 and the L-shaped second substrate 22 with the same shape. The metal substrate 2 is made of any one of gold, silver, and copper. Limiting through holes 23 are provided on both the L-shaped first substrate 21 and the L-shaped second substrate 22. A first step 211, a first positioning groove 212, and a second positioning groove 213 are provided on the L-shaped first substrate. A second step 221, a third positioning groove 222, and a fourth positioning groove 223 are provided on the L-shaped second substrate. Electroless nickel plating is performed on the L-shaped first substrate 21 and the L-shaped second substrate 22 to form a nickel plating layer on the surfaces of the L-shaped first substrate 21 and the L-shaped second substrate 22. Then, the L-shaped first substrate 21 and the L-shaped second substrate 22 are successively subjected to cleaning, pickling, alkali washing, and chemical activation treatment, coated with a bottom glue, and heat-cured for standby. Specifically: First, the L-shaped first substrate 21 and the L-shaped second substrate 22 are ultrasonically cleaned with isopropyl alcohol for 12 minutes, then pickled with 5wt% dilute hydrochloric acid for 7 minutes, then alkali-washed with 5wt% sodium hydroxide solution for 13 minutes, then chemically activated with a mixed solution of sulfuric acid and hydrogen peroxide with a volume ratio of 3:1, and then rinsed with deionized water to completely remove the activation solution. The bottom glue is selected from epoxy resin or polyurethane resin, and the coating thickness of the bottom glue is 15μm. The metal substrate 2 coated with the bottom glue is placed in an oven for heat-curing treatment. The heat-curing temperature is 120°C and the time is 30 minutes;

[0043] Bracket assembly: Place the bowl-shaped base 1 on the metal substrate 2. The L-shaped first substrate 21 is fixed by fitting the first step 211 with the first stepped groove 11. The L-shaped second substrate 22 is fixed by fitting the second step 221 with the second stepped groove 12. The first positioning bump 15 is fitted with the first positioning groove 212, the second positioning bump 16 is fitted with the second positioning groove 213, the third positioning bump 17 is fitted with the third positioning groove 222, the fourth positioning bump 18 is fitted with the fourth positioning groove 223, and the limiting protrusion 14 is fitted with the limiting through hole 23 for fixation;

[0044] Die bonding: A solder paste film layer is coated on the die bonding area of the metal substrate 2. The coating thickness of the solder paste film layer is 90μm, and the thickness error of the solder paste film layer is controlled within ±3μm. The flip-chip LED chip is placed, and the flip-chip accuracy is controlled within ±10μm. It is fixedly connected to the metal substrate 2 by reflow soldering in a nitrogen protection atmosphere. The reflow soldering temperature is 275°C and the time is 45s. After reflow soldering, the cooling rate is controlled ≤3°C / s;

[0045] Sealing: Fill the quantum dot glue with a viscosity of 5000 mPa·s (25°C) into the reflector cup and perform primary curing. The primary curing temperature is 50 - 100°C, and the temperature is increased step by step from 50°C to 80°C and then to 100°C, with each stage being kept warm for 7 minutes. After cooling to 30°C, fill the silica gel with a viscosity of 3000 mPa·s (25°C) and perform secondary curing. The secondary curing temperature is 100 - 120°C, and the temperature is increased step by step from 100°C to 110°C and then to 120°C, with each stage being kept warm for 7 minutes. Thus, the finished product is obtained.

[0046] Example 3

[0047] As Figures 1 to 3 shown, Figure 1 it is the structural schematic diagram of the first perspective of the present invention, Figure 2 it is the structural schematic diagram of the second perspective of the present invention, Figure 3 it is the exploded structural schematic diagram of the present invention. This example provides a preparation process for a flip-chip LED lamp bead, including the following steps:

[0048] Prepare the bowl-shaped base 1: Obtain the bowl-shaped base 1 through an injection molding process. The bowl-shaped base 1 is made of epoxy resin or polyurethane resin. The bowl-shaped base 1 is provided with a first stepped groove 11 and a second stepped groove 12 arranged in parallel along its length direction. The bowl-shaped base 1 is provided with a partition strip 13 between the first stepped groove 11 and the second stepped groove 12; the connection parts of the partition strip 13 and the bowl-shaped base 1 are all designed with smooth transitions; the inside of the bowl-shaped base 1 is provided with reinforcing ribs around the first stepped groove 11 and the second stepped groove 12; the bowl-shaped base 1 is provided with a first positioning convex block 15 and a second positioning convex block 16 along the first stepped groove 11, the bowl-shaped base 1 is provided with a third positioning convex block 17 and a fourth positioning convex block 18 along the second stepped groove 12, the bottom of the bowl-shaped base 1 is provided with a layer of heat-conducting silica gel gasket; the two ends of the bottom of the bowl-shaped base 1 are provided with limiting protrusions 14, and a reflector cup is formed by plating silver on the surface of the inner cavity of the bowl-shaped base 1;

[0049] Pretreatment of the metal substrate: The metal substrate 2 is cut and polished to obtain the L-shaped first substrate 21 and the L-shaped second substrate 22 with the same shape. The metal substrate 2 is made of any one of gold, silver, and copper. Limiting through holes 23 are provided on both the L-shaped first substrate 21 and the L-shaped second substrate 22. A first step 211, a first positioning groove 212, and a second positioning groove 213 are provided on the L-shaped first substrate. A second step 221, a third positioning groove 222, and a fourth positioning groove 223 are provided on the L-shaped second substrate. Electroless nickel plating is performed on the L-shaped first substrate 21 and the L-shaped second substrate 22 to form a nickel plating layer on the surfaces of the L-shaped first substrate 21 and the L-shaped second substrate 22. Then, the L-shaped first substrate 21 and the L-shaped second substrate 22 are successively subjected to cleaning, pickling, alkali washing, and chemical activation treatments, coated with a bottom glue, and heat-cured for standby. Specifically: First, the L-shaped first substrate 21 and the L-shaped second substrate 22 are ultrasonically cleaned with isopropyl alcohol for 15 minutes, then pickled with 7wt% dilute hydrochloric acid for 15 minutes of immersion time, then alkali-washed with 7wt% sodium hydroxide solution for 15 minutes of immersion time, then chemically activated with a mixed solution of sulfuric acid and hydrogen peroxide with a volume ratio of 4:1, and then rinsed with deionized water to completely remove the activation solution. The bottom glue is selected from epoxy resin or polyurethane resin, and the coating thickness of the bottom glue is 20μm. The metal substrate 2 coated with the bottom glue is placed in an oven for heat-curing treatment. The heat-curing temperature is 130°C and the time is 40 minutes.

[0050] Bracket assembly: Place the bowl-shaped base 1 on the metal substrate 2. The L-shaped first substrate 21 is fixed by fitting the first step 211 with the first stepped groove 11. The L-shaped second substrate 22 is fixed by fitting the second step 221 with the second stepped groove 12. The first positioning protrusion 15 is fitted with the first positioning groove 212. The second positioning protrusion 16 is fitted with the second positioning groove 213. The third positioning protrusion 17 is fitted with the third positioning groove 222. The fourth positioning protrusion 18 is fitted with the fourth positioning groove 223. The limiting protrusion 14 is fitted and fixed with the limiting through hole 23.

[0051] Die bonding: A solder paste film layer is coated on the die bonding area of the metal substrate 2. The coating thickness of the solder paste film layer is 100μm, and the thickness error of the solder paste film layer is controlled within ±3μm. The flip-chip LED chip is placed, and the flip-chip accuracy is controlled within ±10μm. It is fixedly connected to the metal substrate 2 by reflow soldering in a nitrogen protection atmosphere. The reflow soldering temperature is 290°C and the time is 60s. After reflow soldering, the cooling rate is controlled ≤3°C / s.

[0052] Sealing: Fill the quantum dot glue with a viscosity of 6000 mPa·s (25 °C) into the reflector cup and conduct primary curing. The primary curing temperature is 100 °C, and the temperature is increased step by step from 50 °C to 85 °C and then to 100 °C, with each stage maintained for 10 minutes. After cooling to 40 °C, fill the silica gel with a viscosity of 5000 mPa·s (25 °C) and conduct secondary curing. The secondary curing temperature is 120 °C, and the temperature is increased step by step from 100 °C to 115 °C and then to 120 °C, with each stage maintained for 10 minutes, thus obtaining the finished product.

[0053] Testing method:

[0054] Randomly select 10 flip-chip LED lamp beads prepared in each embodiment of this application and conduct tests using the three-point bending test method. The temperature during the test is 25 ± 2 °C, and the humidity is 50 ± 5% RH. Use 10 existing flip-chip LED lamp beads (model full color, purchased from Suzhou Xin Jingding Electronics Co., Ltd.) as the control group. The test results are shown in Table 1:

[0055] Table 1 Test results of various performance of LED lamp beads

[0056]

[0057]

[0058] Note: The letter a indicates a highly significant difference (P < 0.01), and the letter b indicates no significant difference (P > 0.05).

[0059] The above results show that the test indexes of various performances of the flip-chip LED lamp beads prepared in Examples 1 - 3 of this application are all significantly better than those of the existing flip-chip LED lamp beads. Among them, the maximum load lifting amplitude exceeds 40%. This may be because the nickel plating layer enhances the anti-deformation ability of the metal substrate surface, and through the precise design of the cooperation between the first step, the second step and the stepped groove, as well as the fixing method of the limiting protrusion and the limiting through hole, it ensures a firm and stable connection between the bowl-shaped base and the metal substrate, reduces the risk of bracket separation or damage caused by external stress, improves the anti-breaking performance of the bracket, and enables the lamp bead to withstand higher external force impacts; the fracture deflection lifting amplitude reaches 75%, the bending strength lifting amplitude exceeds 50%, and the fracture energy lifting amplitude exceeds 80%. This may be because during the die bonding process, the flip-chip accuracy, the thickness of the solder paste film layer and its error are strictly controlled to ensure good contact and welding quality between the chip and the substrate, effectively disperse the external force applied to the LED lamp bead, reduce local stress concentration, and then improve the overall anti-breaking ability. Secondly, the buffer layer of the secondary silica gel encapsulation can also absorb deformation energy, the stepped curing process reduces the internal stress in the glue, delays the crack propagation, and the synergistic encapsulation of the quantum dot glue and the silica gel forms a gradient mechanical structure, making the overall anti-fatigue performance of the lamp bead significantly enhanced, showing higher toughness during bending and avoiding brittle fracture;

[0060] In summary, through improvements in multiple aspects such as the pretreatment of the metal substrate, the design of the bracket assembly, the control of the die bonding process, and the encapsulation treatment, the present application has significantly improved the anti-breaking performance of the LED lamp beads through their combined action.

[0061] The above are only embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A process for preparing an inverted LED lamp bead, characterized in that: The following steps are involved: Preparation of a bowl-cup-shaped base: The bowl-cup-shaped base is obtained by an injection molding process, wherein the bowl-cup-shaped base is provided with a first step groove and a second step groove in parallel along its length direction, and a baffle strip is provided between the first step groove and the second step groove; limiting protrusions are provided at both ends of the bottom of the bowl-cup-shaped base, and a reflective cup is formed by silver plating the surface of the inner cavity of the bowl-cup-shaped base; Pretreatment of the metal substrate: cutting and grinding the metal substrate to obtain an L-shaped first substrate and an L-shaped second substrate of the same shape, the L-shaped first substrate and the L-shaped second substrate are both provided with limiting through holes, the L-shaped first substrate is provided with a first step, and the L-shaped second substrate is provided with a second step, the L-shaped first substrate and the L-shaped second substrate are chemically nickel-plated to form a nickel-plated layer on the surface of the L-shaped first substrate and the L-shaped second substrate, and then the L-shaped first substrate and the L-shaped second substrate are sequentially cleaned, pickled, alkali-washed and chemically activated, coated with a primer and subjected to thermal curing for standby use; Bracket assembly: Place the bowl-shaped base on the metal base plate, the L-shaped first base plate is fixed by the first step and the first step groove, the L-shaped second base plate is fixed by the second step and the second step groove, and the limiting protrusion is fixed by the limiting through hole; Die bonding: Coat a solder paste film layer on the die bonding area of ​​the metal substrate, flip-chip the LED chip, and control the flip-chip accuracy within ±10μm. Fix it to the metal substrate through reflow soldering in a nitrogen protective atmosphere, and control the cooling rate after reflow soldering to ≤3℃ / s; Sealing glue: fill the reflector cup with quantum dot glue and perform primary curing, cool to 20-40°C, then fill with silica gel and perform secondary curing to obtain the finished product.

2. The process for preparing flip-chip LED lamp beads according to claim 1, characterized in that: In the process of pre-treating the metal substrate, the L-shaped first substrate and the L-shaped second substrate are first ultrasonically cleaned with isopropyl alcohol for 10 to 15 minutes, then pickled with 3 to 7 wt % dilute hydrochloric acid for 5 to 10 minutes, then alkaline washed with 3 to 7 wt % sodium hydroxide solution for 10 to 15 minutes, then chemically activated with a mixed solution of sulfuric acid and hydrogen peroxide in a volume ratio of 2 to 4:1, and then rinsed with deionized water to completely remove the activation solution.

3. The process for preparing flip-chip LED lamp beads according to claim 1, characterized in that: During the pretreatment of the metal substrate, the primer is epoxy resin or polyurethane resin, and the primer coating thickness is 10 to 20 μm. The metal substrate coated with the primer is placed in an oven for heat curing treatment at a temperature of 110 to 130° C. for 20 to 40 minutes.

4. The process for preparing flip-chip LED lamp beads according to claim 1, characterized in that: During the solid crystal process, the coating thickness of the solder paste film layer is 80-100 μm, and the thickness error of the solder paste film layer is controlled within ±3 μm.

5. The process for preparing flip-chip LED lamp beads according to claim 1, characterized in that: During the solid crystal process, the reflow temperature is 260-290° C. and the time is 30-60 seconds.

6. The process for preparing a flip-chip LED lamp bead according to claim 1, characterized in that: During the sealing process, quantum dot glue with a viscosity of 4000-6000 mPa·s (25° C.) is used to fill the reflective cup.

7. The process for preparing a flip-chip LED lamp bead according to claim 1, characterized in that: During the sealing process, silica gel with a viscosity of 3000-5000 mPa·s (25° C.) is used to fill the reflective cup.

8. The process for preparing flip-chip LED lamp beads according to claim 1, characterized in that: The initial curing temperature during the sealing process is 50-100° C., and the temperature is increased in steps from 50° C. to 75-85° C. and then to 100° C., with each stage being kept warm for 5-10 minutes.

9. The process for preparing flip-chip LED lamp beads according to claim 1, characterized in that: The secondary curing temperature during the sealing process is 100-120° C., and the temperature is increased in steps from 100° C. to 105-115° C. and then to 120° C., with each stage being kept warm for 5-10 minutes.

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