A SMT and COB hybrid packaging method, packaging structure and LED screen

Abstract

The present invention relates to a SMT and COB hybrid packaging method, packaging structure and LED screen, including: preparing an adapter plate; obtaining a substrate, dividing the substrate into a plurality of SMT lamp bead preparation areas and a plurality of COB chip preparation areas, firstly solidifying the adapter plate and welding it to the COB chip preparation area, then solidifying the adapter plate to form a self-luminous unit, and welding the stimulated light-emitting unit to the SMT lamp bead preparation area, raising the self-luminous unit by the adapter plate, so that the height of the self-luminous unit relative to the substrate and the height of the top of the stimulated light-emitting unit relative to the substrate are consistent or nearly consistent; the self-luminous unit and the stimulated light-emitting unit are packaged as a whole, and the upper surface of the package is flattened. The present invention raises the self-luminous unit to reduce interference with the light emission of the stimulated light-emitting unit, solves the problem of mixed light of the self-luminous unit and the stimulated light-emitting unit, and can better retain the light-emitting effect of the entire screen.

Description

Technical Field

[0001] The present invention relates to the technical field of LED packaging, and in particular to a SMT and COB hybrid packaging method, a packaging structure and an LED screen. Background Art

[0002] In the field of LED display, LED screens include two types of assembly methods: SMT (surface mount technology) to mount LED lamp beads and COB (chip on board) to directly fix LED chips. From the display effect point of view, for SMT LED screens, each lamp bead can be regarded as a separate point light source, and each pixel has a clear boundary. After COB packaging, the uniform diffusion powder makes the COB LED screen mix light more evenly, and the light output is similar to a surface light source, and the appearance is similar to LCD / OLED and other TV products. The two types of LED screens are generally used in different scenarios. SMT-assembled LED screens, including early R, G, B monochrome lamp beads, to the current mainstream RGB integrated lamp beads, are generally used in ultra-large display fields, including outdoor advertising screens, indoor movie screens, etc.; while COB-assembled LED screens are generally used in close-range viewing areas such as large monitoring screens to obtain a viewing experience similar to that of a TV screen.

[0003] In some special use areas, such as large outdoor advertising vehicles, station dynamic billboards and other fields, if a large LED screen is used for display, the LED screen is required to have both high brightness and high contrast, and can be viewed by customers at close range; SMD display screens can meet the high brightness requirements, but the light is concentrated, and long-term viewing can easily cause eye fatigue; COB screens have softer and more uniform light and color, but because COB directly fixes the chip on the PCB substrate, the distance between the two pads corresponding to each chip on the PCB substrate is very close; if the chip's light brightness is simply increased, then at a current that meets the outdoor brightness, the extremely close pad spacing, coupled with the more demanding outdoor use environment than indoors, will easily lead to metal migration between pads, ultimately causing short circuits, dead lights or string lights, and other defects.

[0004] RGBW technology is a common pixel control method that achieves high brightness and high contrast by sacrificing a small amount of color gamut. It can obtain a relatively large peak brightness of the entire screen under a relatively small current. This technology has been used in many display technologies, including LCD, OLED, SMT LED, etc. In addition, MiniLED partition backlight technology can also be roughly understood as another form of RGBW display technology: according to the actual product design, a group of MiniLED partitions controls the brightness of dozens to hundreds of LCD pixels, and ultimately obtains better peak brightness and contrast.

[0005] In the field of LED, monochromatic white light is generally realized by phosphors. The mainstream methods include blue light chips stimulating yellow phosphors, or ultraviolet light chips stimulating three-color phosphors, or using similar quantum dot phosphor technology. In order to avoid the problem of cross-light caused by the additional excitation of W light by RGB when W and RGB are used together, affecting the display effect, a retaining wall is generally built between RGB and W, such as Figure 1 As shown, RGB and W are isolated in different areas respectively; but in actual use, the retaining wall will actually affect the RGBW light output; at the same time, the retaining wall is generally made of white dam glue, which has a certain luminous effect and can concentrate light, resulting in the soft light output effect of the COB LED itself being affected; at the same time, because white light in RGBW generally carries a relatively higher current, directly using COB packaging with a narrow pad spacing is also prone to quality risks.

[0006] In order to realize both RGBW high-brightness display technology and COB soft light, there is another solution, such as Figure 2 As shown, RGB three-color chips and packaged white light lamp beads that have a certain degree of resistance to cross-talk interference are assembled at the same time; however, if the white light lamp beads and RGB chips are simply assembled on the same board at the same time, the RGB light-emitting effect will also be affected due to the large size difference between the white light lamp beads and the RGB chips. In addition, since the overall luminous height of the RGB is still lower than the height of the phosphor in the white light lamp beads, there is still a risk of cross-talk caused by RGB exciting the phosphor. Summary of the invention

[0007] To this end, the technical problem to be solved by the present invention is to overcome the problem in the prior art that when the self-luminous unit and the stimulated light-emitting unit are packaged in the same module, the actual light output is affected and there is a risk of cross-light. A SMT and COB hybrid packaging method, packaging structure and LED screen are provided to raise the self-luminous unit so that its top height is almost consistent with that of the stimulated light-emitting unit, thereby solving the problem of mixed light of the self-luminous unit and the stimulated light-emitting unit, and better retaining the light output effect of the entire screen.

[0008] In order to solve the above technical problems, the present invention provides a SMT and COB hybrid packaging method, comprising the following steps:

[0009] S1. Prepare an adapter plate for raising the self-luminous unit;

[0010] S2. Obtain a substrate, divide the substrate into multiple SMT lamp bead preparation areas and multiple COB chip preparation areas, first fix the die on the adapter plate and weld it to the COB chip preparation area, then fix the die on the adapter plate to form a self-luminous unit, and weld the stimulated light-emitting unit to the SMT lamp bead preparation area, and raise the self-luminous unit by the adapter plate so that the height of the self-luminous unit relative to the substrate and the height of the top of the stimulated light-emitting unit relative to the substrate are consistent or nearly consistent;

[0011] S3. The self-luminous unit and the stimulated luminous unit are packaged as a whole, and the upper surface of the package is flattened.

[0012] In one embodiment of the present invention, in step S1, preparing the adapter plate includes the following steps:

[0013] S1-1, welding to form a double-layer PCB carrier;

[0014] S1-2, a carrier array is designed on the upper surface of the PCB carrier, and the side with the array is attached to the carrier film of the dicing machine by UV adhesive tape, and cutting is performed along the edge of the array;

[0015] S1-3, attach the solid crystal blue film to the PCB carrier, and irradiate it with UV light to transfer the cut PCB carrier as a whole to the blue film.

[0016] In one embodiment of the present invention, in step S2, the bonding sequence is to bond the adapter board and weld it to the COB chip preparation area, weld the stimulated light-emitting unit to the SMT lamp bead preparation area, and then bond the self-luminous unit to the adapter board.

[0017] In one embodiment of the present invention, the self-luminous unit is an RGB chip, and the stimulated luminous unit is a white light lamp bead.

[0018] In one embodiment of the present invention, the self-luminous unit is a GB chip, and the stimulated luminous unit is a red light bead.

[0019] In one embodiment of the present invention, the chip in the self-luminous unit is a face-up chip or a flip-chip. If a face-up chip is used, the chip can be directly bonded to the adapter board by soldering; if a flip-chip is used, the chip can be bonded to the adapter board by using silver glue, solder paste, flux paste or mass transfer bonding technology.

[0020] In one embodiment of the present invention, multiple SMT lamp bead preparation areas and multiple COB chip preparation areas are divided on the substrate, and the number of SMT lamp bead preparation areas and multiple COB chip preparation areas are set to correspond, or one SMT lamp bead preparation area is set to correspond to multiple COB chip preparation areas.

[0021] In one embodiment of the present invention, in step S3, the following steps are included:

[0022] S3-1, using the method of primer dispensing or dam overall potting, the substrate is filled with glue and cured, the height of the glue is higher than the height of the top of the self-luminous unit and the stimulated light-emitting unit, and the self-luminous unit and the stimulated light-emitting unit are encapsulated in the glue;

[0023] S3-2. Use glue pouring, film pasting or molding to level the top surface of the glue.

[0024] In order to solve the above technical problems, the present invention also provides a SMT and COB hybrid packaging structure, comprising:

[0025] A substrate, wherein the substrate is divided into a plurality of SMT lamp bead preparation areas and a plurality of COB chip preparation areas;

[0026] The adapter plate is die-bonded and welded on the COB chip preparation area of ​​the substrate;

[0027] Self-luminous unit, die-bonded on the adapter board;

[0028] The stimulated light emitting unit is welded on the SMT lamp bead preparation area of ​​the substrate;

[0029] Wherein: the adapter plate raises the self-luminous unit so that the height of the self-luminous unit relative to the substrate is consistent or nearly consistent with the height of the top of the stimulated light-emitting unit relative to the substrate.

[0030] In order to solve the above technical problems, the present invention also provides an LED screen assembled using the SMT and COB hybrid packaging structure.

[0031] The above technical solution of the present invention has the following advantages compared with the prior art:

[0032] The SMT and COB hybrid packaging method and packaging structure described in the present invention integrate the self-luminous unit and the stimulated light emitting unit into a package on the same substrate, and set an adapter plate to raise the self-luminous unit so that the height of the self-luminous unit is consistent or nearly consistent with the top height of the stimulated light emitting unit. On the one hand, it can solve the problem of mixing light of the self-luminous unit and the stimulated light emitting unit, and can better retain the effect of whole-screen light output. On the other hand, setting the self-luminous unit and the stimulated light emitting unit to be height-matched can more conveniently confirm the flatness of the surface after the overall packaging, thereby improving the effect and quality of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein

[0034] Figure 1It is a schematic diagram of the packaging structure of prior art 1;

[0035] Figure 2 It is a schematic diagram of the packaging structure of prior art 2;

[0036] Figure 3 It is a schematic diagram of the SMT and COB hybrid packaging structure of the present invention;

[0037] Figure 4 It is a step diagram of the SMT and COB hybrid packaging method of the present invention;

[0038] Figure 5 is a flow chart of preparing an adapter plate of the present invention;

[0039] Figure 6 It is a flow chart of chip mounting and die bonding on a substrate of the present invention;

[0040] Figure 7 is a flow chart of the overall package of the present invention;

[0041] Figure 8 The present invention divides the SMT lamp bead preparation area and the COB chip preparation area into various different forms of division methods on the substrate;

[0042] Fig. 9 It is a schematic diagram of the distribution structure of another embodiment of the self-luminous unit and the stimulated luminous unit of the present invention.

[0043] Explanation of the reference numerals in the specification: 1. substrate; 2. adapter plate; 3. self-luminous unit; 4. stimulated luminescent unit. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0045] As mentioned above, in order to improve the luminous quality of the LED screen, the prior art attempts to integrate the self-luminous unit and the stimulated light-emitting unit into the same module using COB technology and SMT technology respectively. However, in actual use, the actual light output of the self-luminous unit and the stimulated light-emitting unit will affect each other, and there is a risk of cross-light. In order to solve this technical problem, the present invention raises the self-luminous unit to make it almost the same height as the top of the stimulated light-emitting unit, thereby solving the problem of light mixing between the self-luminous unit and the stimulated light-emitting unit, and can better retain the light output effect of the entire screen. The technical scheme and technical effects of the present invention are further explained below in conjunction with specific embodiments.

[0046] Example 1

[0047] Reference Figure 3As shown, the present invention discloses a SMT and COB hybrid packaging structure, including: a substrate 1, an adapter board 2, a self-luminous unit 3 and a stimulated light unit 4, wherein: the packaging processes of the self-luminous unit 3 and the stimulated light unit 4 on the substrate 1 are different, therefore, according to actual needs, the substrate 1 is divided into a plurality of SMT lamp bead preparation areas and a plurality of COB chip preparation areas, if the self-luminous unit 3 and the stimulated light unit 4 are directly packaged in the COB chip preparation area and the SMT lamp bead preparation area correspondingly, due to the different heights of the self-luminous unit 3 and the stimulated light unit 4, the height of the stimulated light unit 4 is significantly higher than the self-luminous unit 3, and the light emission of the stimulated light unit 4 will affect the self-luminous unit 3;

[0048] In this embodiment, when packaging the self-luminous unit 3, the adapter plate 2 is first set to be die-bonded and welded on the COB chip preparation area of ​​the substrate 1, and then the self-luminous unit 3 is die-bonded on the adapter plate 2. When packaging the stimulated light-emitting unit 4, the stimulated light-emitting unit 4 is directly welded to the SMT lamp bead preparation area of ​​the substrate 1. At this time, the self-luminous unit 3 is padded by the adapter plate 2 to reduce the height difference between the self-luminous unit 3 and the stimulated light-emitting unit 4, so that the height of the self-luminous unit 3 relative to the substrate 1 and the height of the top of the stimulated light-emitting unit 4 relative to the substrate 1 are consistent or nearly consistent. When packaging, the height is controlled to be the same as much as possible. Due to the influence of the process, there may be a small height difference;

[0049] When the top heights of the self-luminous unit 3 and the stimulated luminous unit 4 are consistent or nearly consistent, the self-luminous unit 3 will not excite the phosphor in the stimulated luminous unit 4. The luminous penetration of the phosphor stimulated by the stimulated luminous unit 4 is limited and the pad of the self-luminous unit 3 blocks the light, avoiding the risk of cross-light.

[0050] Example 2

[0051] In order to realize the packaging structure of the above-mentioned embodiment 1, refer to Figure 4 As shown, in this embodiment, a packaging method is provided, comprising the following steps:

[0052] S1, preparing an adapter plate 2 for raising the self-luminous unit 3;

[0053] The adapter plate 2 in this embodiment actually serves to raise the self-luminous unit 3, but it needs to meet the function of conducting the self-luminous unit 3 and the substrate 1. Therefore, the adapter plate 2 needs to meet two conditions: first, the adapter plate 2 can be solid-bonded on the substrate 1, and second, the self-luminous unit 3 can be solid-bonded on the adapter plate 2. Figure 5 As shown, in this embodiment, the steps of preparing the adapter plate 2 are:

[0054] S1-1, welding to form a double-layer PCB carrier;

[0055] S1-2, a carrier array is designed on the upper surface of the PCB carrier, and the side with the array is attached to the carrier film of the dicing machine by UV adhesive tape, and cutting is performed along the edge of the array;

[0056] S1-3, attaching the solid crystal blue film to the PCB carrier, and irradiating it with UV light to transfer the cut PCB carrier as a whole to the blue film;

[0057] In the present embodiment, a double-layer PCB carrier is provided to be able to bond with the substrate 1 and the self-luminous unit 3 respectively. The PCB carrier can be a double-sided aluminum substrate or a thick copper substrate, or other common PCB substrates such as an FR4 board and a BT board. The design thickness of the double-layer PCB carrier is designed according to the height difference between the self-luminous unit 3 and the stimulated light-emitting unit 4. For example, taking the common RGBW technology as an example, that is, the flip-chip RGB chip and the white light lamp bead as an example, the height of the flip-chip RGB chip is generally 0.08-0.1mm, the height of the white light lamp bead is generally 0.3-0.5mm, and the height of the substrate 1 is generally 1-2mm. The position of the phosphor is close to the chip end or close to the outside according to the specific product design. If the phosphor distribution close to the chip end is used, the light output height of the lamp bead is about 0.2mm. Therefore, as long as the overall height of the flip-chip RGB chip is raised by 0.3mm, the interference of the light penetration can be completely avoided. Therefore, the thickness of the adapter plate 2 can be set to 0.3mm.

[0058] S2. Obtain a substrate 1, divide the substrate 1 into a plurality of SMT lamp bead preparation areas and a plurality of COB chip preparation areas, firstly bond the adapter plate 2 and weld it to the COB chip preparation area, then bond the self-luminous unit 3 to the adapter plate 2, and weld the stimulated light-emitting unit 4 to the SMT lamp bead preparation area, raise the self-luminous unit 3 by the adapter plate 2, reduce the height difference between the self-luminous unit 3 and the stimulated light-emitting unit 4, and make the height of the self-luminous unit 3 relative to the substrate 1 and the height of the top of the stimulated light-emitting unit 4 relative to the substrate 1 consistent or nearly consistent;

[0059] Specifically, in the actual process of patch and die bonding, the first solder paste is applied, and at the same time, the adapter board 2 is bonded and welded to the COB chip preparation area, and the stimulated light-emitting unit 4 is welded to the SMT lamp bead preparation area. Then, the second solder paste is applied using a stepped steel mesh, and then the self-luminous unit 3 is bonded to the adapter board 2.

[0060] Specifically, in this embodiment, the self-luminous unit 3 is set to be an RGB chip, and the stimulated light-emitting unit 4 is a white light lamp bead, wherein: the chip in the self-luminous unit 3 is a face-up chip or a flip-chip. If a face-up chip is used, the chip can be directly die-bonded on the adapter board 2; if a flip-chip is used, the chip can be die-bonded on the adapter board 2 using silver glue, solder paste, flux paste, and mass transfer die-bonding technology.

[0061] S3, encapsulating the self-luminous unit 3 and the stimulated luminous unit 4 as a whole, and leveling the upper surface of the encapsulation;

[0062] After the self-luminous unit 3 and the stimulated light-emitting unit 4 are bonded and bonded, the height difference between the self-luminous unit 3 and the stimulated light-emitting unit 4 is reduced, which can more conveniently confirm the flatness of the surface after the overall packaging, thereby improving the effect and quality of the product. Figure 7 As shown, the packaging steps include:

[0063] S3-1, using the method of primer dispensing or dam overall potting, the substrate 1 is filled with glue and cured, the height of the glue is higher than the height of the top of the self-luminous unit 3 and the stimulated light-emitting unit 4, and the self-luminous unit 3 and the stimulated light-emitting unit 4 are encapsulated in the glue;

[0064] S3-2. Use glue pouring, film pasting or molding to level the top surface of the glue.

[0065] As mentioned above, according to the actual use requirements, multiple SMT lamp bead preparation areas and multiple COB chip preparation areas are divided on the substrate 1. Figure 8 As shown, there are several distributions of multiple SMT lamp bead preparation areas and multiple COB chip preparation areas:

[0066] 1. Set the number of SMT lamp bead preparation areas and multiple COB chip preparation areas to correspond, refer to Figure 8 As shown in (a), a set of RGB chips is set to correspond to one white light lamp bead;

[0067] 2. Set up one SMT lamp bead preparation area to correspond to multiple COB chip preparation areas, refer to Figure 8 As shown in (b), (c), (d), and (e), multiple groups of RGB chips are set to correspond to one white light lamp bead, where: Figure 8 (b), (c), and (d) are the regular distribution of RGB chips and white light beads. That is, the white light beads are arranged in a rectangular array, and the RGB chips are arranged on the outside. Figure 8 (b), (c), and (d) have different layouts. Figure 8 (e) is the irregular distribution of RGB chips and white light lamp beads, that is, the white light lamp beads are set to a special-shaped structure, and the RGB chips are distributed accordingly according to the special-shaped structure.

[0068] Example 3

[0069] In the above-mentioned embodiments 1 and 2, RGBW display technology is adopted. The packaging method and packaging structure of the present invention are not limited to RGBW display technology. Fig. 9 As shown, if the flip-chip red light chip in the RGB display is replaced with a flip-chip blue light chip + quantum dot red ink, which has a relatively lower cost and greatly improved color performance, that is, a QuantumR lamp bead is formed, the packaging method and packaging structure of the present invention can also be used. In this structure, the GB chip is a self-luminous unit 3, and the Quantum R lamp bead is a stimulated light-emitting unit 4. The GB chip is raised by the adapter plate 2 so that the height of the GB chip and the Quantum R lamp bead are consistent or nearly consistent.

[0070] Example 4

[0071] The present invention also discloses an LED screen, characterized in that: it is assembled using the SMT and COB hybrid packaging structure described in the above-mentioned embodiment 1 or 3, and the SMT and COB hybrid packaging structure is prepared using the method of the above-mentioned embodiment 2.

[0072] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A SMT and COB hybrid packaging method, characterized in that: The following steps are involved: S1. Prepare an adapter plate for raising the self-luminous unit, including: S1-1, welding to form a double-layer PCB carrier; S1-2, a carrier array is designed on the upper surface of the PCB carrier, and the side with the array is attached to the carrier film of the dicing machine by UV adhesive tape, and cutting is performed along the edge of the array; S1-3, attaching the solid crystal blue film to the PCB carrier, and irradiating it with UV light to transfer the cut PCB carrier as a whole to the blue film; S2. Obtain a substrate, divide the substrate into multiple SMT lamp bead preparation areas and multiple COB chip preparation areas, first fix the die on the adapter plate and weld it to the COB chip preparation area, then fix the die on the adapter plate to form a self-luminous unit, and weld the stimulated light-emitting unit to the SMT lamp bead preparation area, and raise the self-luminous unit by the adapter plate so that the height of the self-luminous unit relative to the substrate and the height of the top of the stimulated light-emitting unit relative to the substrate are consistent or nearly consistent; S3. The self-luminous unit and the stimulated luminous unit are packaged as a whole, and the upper surface of the package is flattened.

2. The SMT and COB hybrid packaging method according to claim 1, characterized in that: In step S2, the die bonding sequence is to first bond the adapter board and weld it to the COB chip preparation area, weld the stimulated light-emitting unit to the SMT lamp bead preparation area, and then bond the self-luminous unit to the adapter board.

3. The SMT and COB hybrid packaging method according to claim 2, characterized in that: The self-luminous unit is an RGB chip, and the stimulated luminous unit is a white light lamp bead.

4. The SMT and COB hybrid packaging method according to claim 2, characterized in that: The self-luminous unit is a GB chip, and the stimulated luminous unit is a red light bead.

5. The SMT and COB hybrid packaging method according to claim 3 or 4, characterized in that: The chip in the self-luminous unit is a face-up chip or a flip-chip. If a face-up chip is used, the chip is directly bonded to the adapter board; if a flip-chip is used, the chip is bonded to the adapter board using silver glue, solder paste, flux paste or mass transfer bonding technology.

6. The SMT and COB hybrid packaging method according to claim 1, characterized in that: Divide the substrate into multiple SMT lamp bead preparation areas and multiple COB chip preparation areas, set the number of SMT lamp bead preparation areas and multiple COB chip preparation areas to correspond, or set one SMT lamp bead preparation area to correspond to multiple COB chip preparation areas.

7. The SMT and COB hybrid packaging method according to claim 1, characterized in that: In step S3, the following steps are included: S3-1, using the method of primer dispensing or dam overall potting, the substrate is filled with glue and cured, the height of the glue is higher than the height of the top of the self-luminous unit and the stimulated light-emitting unit, and the self-luminous unit and the stimulated light-emitting unit are encapsulated in the glue; S3-2. Use glue pouring, film pasting or molding to level the top surface of the glue.

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