A method for spot laser co-bonding of three-color Micro LED chips

Abstract

The present application belongs to the technical field of three-color LED chip processing, and particularly relates to a three-color Micro LED chip point laser co-bonding method, comprising the following steps: step 1, preparing a transfer glass plate, processing an attached adhesive layer, a PET material layer and a crystal arranging adhesive layer, and setting an air inflation device comprising a sealed air filling space; step 2, preparing a PCB substrate; step 3, arranging a plurality of three-color Micro LED chips on the bottom surface of the crystal arranging adhesive layer; step 4, moving the transfer glass plate and the three-color Micro LED chips thereon to above the corresponding pads; step 5, starting the air inflation device to fill air pressure in the sealed air filling space to cause slight deformation of the transfer glass plate; and step 6, selecting red light laser parameters to perform laser welding on R chips; compared with the prior art, the present application only needs to clean the transfer glass plate once, paste a transfer film once and perform one-time alignment and compression bonding; the material loss is reduced, the process route is simplified, and the production efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of tri-color LED chip processing technology, specifically to a tri-color Micro LED chip spot laser co-welding method. Background Technology

[0002] Tri-color LED chips, specifically RGB LED chips corresponding to red, green, and blue. Currently, mini LED chips all suffer from inconsistent thicknesses for red and blue-green light chips; the red light chip is 20-40µm thinner than the blue-green chip. Figure 1 As shown, this prevents the simultaneous welding of three laser colors in point laser welding (the three colors cannot be welded together in one operation). Therefore, all current point laser welding processes use single-color crystal arrangement and single-color welding processes, such as... Figure 2 As shown, the existing MINILED dot laser packaging process route is: transfer glass cleaning -> transfer film attachment -> red chip alignment -> red chip laser welding -> transfer glass cleaning -> transfer film attachment -> blue chip alignment -> blue chip laser welding -> transfer glass cleaning -> transfer film attachment -> green chip alignment -> green chip laser welding. This solution requires three transfer glasses, three cleaning processes, three transfer films, and three alignment and pressing welds. This process route has low production efficiency, high labor costs, high material costs, and is complex. The traditional transfer film thickness is 110um: PET thickness is 50um, and the adhesive layer thickness on both the glass attachment surface and the chip alignment surface is 30um. With a transfer film of this thickness, the red chip cannot contact the pads on the PCB substrate. Moreover, the non-air-expansion pressing process cannot apply pressure to the transfer glass after alignment to slightly deform it and drive the red chip closer to the pads. Therefore, the risk of poor soldering of the red chip is extremely high. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for laser co-welding of three-color Micro LED chips.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is: a method for spot laser co-welding of three-color Micro LED chips, comprising the following steps: Step 1: Prepare a transfer glass plate, and process the adhesive layer, PET material layer and crystal-removing adhesive layer in sequence on the bottom surface of the transfer glass plate. Set an air expansion device including a sealed air-filled space on the upper surface of the transfer glass plate. Step 2: Prepare a PCB substrate and process several pads on it for soldering to the red-emitting R chip, the green-emitting G chip, and the blue-emitting B chip. Step 3: Arrange several identical tri-color Micro LED chips on the bottom surface of the die-attachment layer. The number of tri-color Micro LED chips is the same as the number of pads. Step 4: Move the transfer glass plate and the three-color Micro LED chips on it to the corresponding pads, so that the R chip is suspended above the pads or in contact with the pads, and the G and B chips are in contact with the surface of the corresponding pads and the die adhesive layer is squeezed. Step 5: Activate the air expansion device to inflate the sealed air space, causing slight deformation of the transfer glass plate. The adhesive layer, PET material layer and crystal sizing adhesive layer will deform accordingly, ensuring that the R chip is in contact with the corresponding pad. At this time, the G chip and B chip are under overpressure relative to the pad. Step 6: Select red laser parameters to perform laser welding on the R chip; after welding is completed, turn off the air pressure and separate to complete the pressure welding.

[0005] Preferably, the thickness of the processing adhesive layer is 50 μm, the thickness of the PET material layer is 50 μm, and the thickness of the crystal-clear adhesive layer is 80 μm.

[0006] Preferably, the air pressure in the sealed inflatable space is 20 kPa; the deformation of the transfer glass plate forces the R chip to press downward until the R chip contacts the PCB substrate, and the transfer glass plate deforms downward by 20-40 μm.

[0007] Preferably, the method further includes step 7: shutting down the gas expansion device, releasing the gas in the sealed inflation space, so that both the G chip and the B chip return to their natural state of contact with the corresponding pad surface and compression of the die-attach adhesive layer; then selecting green laser parameters to perform laser welding on the G chip or selecting blue laser parameters to perform laser welding on the B chip.

[0008] Preferably, green laser parameters are selected for laser welding of the G chip.

[0009] Preferably, in step 8, blue laser parameters are selected to perform laser welding on chip B.

[0010] Beneficial technical effects: The transfer film, composed of an adhesive layer, a PET material layer, and a crystal-aligning adhesive layer, increases the thickness of the transfer film compared to existing technologies. This compensates for the thickness difference between the red-emitting R chip and the other two colors of chips. After compensation, the distance between the R chip and the corresponding pad is significantly reduced or even eliminated. To eliminate the potential for non-contact between the R chip and the corresponding pad, an air expansion device is added. During R chip welding, air is inflated in a sealed air-filled space to cause slight deformation of the transfer glass plate, ensuring contact between the R chip and the corresponding pad. Compared to existing technologies, this invention only requires cleaning the transfer glass plate once, using one transfer film and applying the transfer film only once, and performing alignment and pressing welding once. This reduces material consumption, simplifies the process route, and improves production efficiency. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the prior art welding process corresponding to an embodiment of the present invention; Figure 2 This is a schematic diagram of a prior art monochromatic crystal arrangement corresponding to an embodiment of the present invention; Figure 3 This is a schematic diagram of the unprocessed state in an embodiment of the present invention; Figure 4 This is a schematic diagram of the air expansion device being started and processing according to an embodiment of the present invention. Detailed Implementation

[0012] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0013] like Figures 3-4 As shown, this embodiment of the invention provides a method for point laser co-soldering of three-color Micro LED chips, including the following steps: Step 1: Prepare a transfer glass plate 1, and process the adhesive layer 2, PET material layer 3 and crystal-removing adhesive layer 4 sequentially on the bottom surface of the transfer glass plate. Set an air expansion device 5 including a sealed air-filled space on the upper surface of the transfer glass plate. Step 2: Prepare a PCB substrate 6 and process several pads on it for soldering to the red-emitting R chip, the green-emitting G chip, and the blue-emitting B chip (not shown). Step 3: Arrange several identical tri-color Micro LED chips on the bottom surface of the die-attachment layer. The number of tri-color Micro LED chips is the same as the number of pads. Step 4: Move the transfer glass plate 1 and the three-color Micro LED chips on it to the corresponding pads, so that the R chip is suspended above the pads or in contact with the pads, and the G chip and B chip are in contact with the surface of the corresponding pads and the die-attach adhesive layer is squeezed. Step 5: Activate the air expansion device to inflate the sealed air space, causing slight deformation of the transfer glass plate. The adhesive layer, PET material layer and crystal sizing adhesive layer will deform accordingly, ensuring that the R chip is in contact with the corresponding pad. At this time, the G chip and B chip are under overpressure relative to the pad. Step 6: Select red laser parameters to perform laser welding on the R chip.

[0014] In step 6, the laser welding method used is existing technology; the adhesive layer / PET material layer / chip packing adhesive layer are integrated to form a transfer film, which is a purchased double-sided adhesive film material, the purpose of which is to transfer the chip. The thickened transfer film is a film material improved by the supplier; in step 4, the R chip is either suspended above the pad or in contact with the pad. If it is suspended, the distance between the R chip and the pad is very small. The R chip can be made to contact the pad by driving the air expansion device; during the welding of the R chip, the height (thickness) of the G chip and the B chip is greater than that of the R chip. When the R chip contacts the pad, the G chip and the B chip squeeze the chip packing adhesive layer 4 and deform the chip packing adhesive layer. When the transfer glass plate 1 is not deformed, the R chip is 20-40µm lower than the G and B chips. After filling with air pressure, the G and B chips are supported by the PCB substrate 6, while the R chip is not supported by the PCB substrate. The deformation of the transfer glass plate forces the R chip to press downwards until it contacts the PCB substrate. The slight deformation of the transfer glass plate mentioned here refers to a downward deformation of 20-40µm, which just compensates for the height difference between the R chip and the G and B chips. In this embodiment, the air pressure in the sealed inflation space is 20 kPa; the deformation of the transfer glass plate forces the R chip to press downwards until it contacts the PCB substrate, and the transfer glass plate deforms downwards by 20-40µm. The air expansion device 5 here includes an alloy frame 501, a quartz glass 502 disposed at the top of the alloy frame, and the transfer glass plate 1 disposed at the bottom of the alloy frame 501.

[0015] In this embodiment, the thickness of the processing adhesive layer 2 is 50 μm, the thickness of the PET material layer 3 is 50 μm, and the thickness of the crystal-coated adhesive layer 4 is 80 μm.

[0016] The transfer film consists of an adhesive layer, a PET material layer, and a crystal-aligning adhesive layer. Compared to existing transfer films, this invention increases the thickness of the transfer film; for example... Figures 1-2 As shown, due to the small thickness of the transfer film, the R chip cannot contact the pads, so the three-color chips cannot be soldered simultaneously; moreover, the existing technology does not have an air expansion device, and after pressing the transfer glass plate, without other external force, the R chip cannot contact the pads, resulting in an extremely high risk of poor soldering.

[0017] Existing technology uses a fixed gap pressing method for pressing, and only one gap adjustment is performed after alignment. That is, only one gap adjustment can be made for the thickness of the red light chip or the blue and green light chip. If the red light is pressed in place, the blue and green light will have overpressure, and the solder paste will be squeezed out of the pad, resulting in defects such as low thrust and poor reliability. If the blue and green light is pressed in place, the red light will not be pressed in place, resulting in a cold solder joint for the red light.

[0018] This invention employs a variable height bonding method: First, the bonding height is adjusted to the bonding height of chip R, and red laser parameters are selected for red light welding. At this time, chips G and B are in an over-pressure state. After the R chip is welded, the bonding height is adjusted to the bonding height of chips B and G, and blue and green laser welding parameters are selected to weld chips B and G respectively. At this time, the R chip has been welded, and the welding of chips B and G will not affect the R chip. At the same time, when the solder paste melts on the bottom pads of chips B and G, the solder paste bulges, forming a good welding effect.

[0019] After the R chip is soldered, step 7 is also included: turning off the gas expansion device, releasing the gas in the sealed gas-filled space, so that both the G chip and the B chip return to their natural state of contact with the corresponding pad surface and extrusion of the die-packing adhesive layer; and selecting green laser parameters to perform laser soldering on the G chip.

[0020] After completing the G chip welding, step 8 is also included, which involves selecting blue laser parameters to perform laser welding on the B chip.

[0021] Thus, the three-color chips can be soldered through a single crystal arrangement.

[0022] Obviously, there are no special requirements when choosing the soldering order of the G chip and the B chip. You can solder the G chip first and then the B chip, or you can solder the B chip first and then the G chip. The effect is the same.

[0023] In the above description, it should be noted that the terms "installation", "connection", "connection" and other such terms should be interpreted broadly. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components.

[0024] Obviously, the embodiments described above are merely some, not all, embodiments of the present invention. The accompanying drawings show preferred embodiments of the present invention, but do not limit the scope of the patent. The present invention can be implemented in many different forms; rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention. Any equivalent structures made using the description and drawings of the present invention, whether directly or indirectly applied to other related technical fields, are similarly within the scope of protection of this patent.

Claims

1. A method for spot laser co-soldering of three-color Micro LED chips, characterized in that, Includes the following steps: Step 1: Prepare a transfer glass plate, and process the adhesive layer, PET material layer and crystal-removing adhesive layer in sequence on the bottom surface of the transfer glass plate. Set an air expansion device including a sealed air-filled space on the upper surface of the transfer glass plate. Step 2: Prepare a PCB substrate and process several pads on it for soldering to the red-emitting R chip, the green-emitting G chip, and the blue-emitting B chip. Step 3: Arrange several identical tri-color Micro LED chips on the bottom surface of the die-attach layer. The number of tri-color Micro LED chips is the same as the number of the pads. Step 4: Move the transfer glass plate and the three-color Micro LED chips on it to the corresponding pads, so that the R chip is suspended above the pads or in contact with the pads, and the G and B chips are in contact with the surface of the corresponding pads and the die adhesive layer is squeezed. Step 5: Activate the air expansion device to fill the sealed air space with air pressure, causing the transfer glass plate to deform slightly. The adhesive layer, PET material layer and crystal sizing adhesive layer will deform accordingly, ensuring that the R chip is in contact with the corresponding pad. At this time, the G chip and B chip are in an overpressure state relative to the pad. Step 6: Select red laser parameters to perform laser welding on the R chip; after welding is completed, turn off the air pressure and separate to complete the pressure welding.

2. The method for spot laser co-soldering of three-color Micro LED chips as described in claim 1, characterized in that, The thickness of the processing adhesive layer is 50 μm, the thickness of the PET material layer is 50 μm, and the thickness of the crystal-coated adhesive layer is 80 μm.

3. The method for spot laser co-welding of three-color Micro LED chips as described in claim 2, characterized in that, The sealed inflatable space is filled with an air pressure of 20 kPa; the deformation of the transfer glass plate forces the R chip to press downward until the R chip contacts the PCB substrate, and the transfer glass plate deforms downward by 20-40 μm.

4. The method for spot laser co-soldering of three-color Micro LED chips as described in claim 2, characterized in that, Step 7: Turn off the air expansion device and release the gas in the sealed inflation space, so that both the G chip and the B chip return to their natural state of contact with the corresponding pad surface and compression of the die-attach adhesive layer; then select green laser parameters to perform laser welding on the G chip or select blue laser parameters to perform laser welding on the B chip.

5. The method for spot laser co-soldering of three-color Micro LED chips as described in claim 4, characterized in that, Green laser parameters were selected for laser welding of the G chip.

6. The method for point laser co-soldering of three-color Micro LED chips as described in claim 5, characterized in that, Step 8: Select blue laser parameters to perform laser welding on chip B.

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