Display module and manufacturing method thereof

Abstract

The application provides a display module and a manufacturing method thereof. The manufacturing method comprises the following steps: flip-chip bonding a plurality of LED chips on a circuit board in an array; first injecting a filling material between the LED chips and the circuit board to form a filling layer; second injecting the filling material on the circuit board at a position different from the filling layer to expand the filling layer to cover the circuit board; and curing the filling layer. The application improves the stability and reliability of the connection between the LED chips and the circuit board and between each of the LED chips, reduces the occurrence of dead light, improves the product yield, and is simple in process, high in production efficiency, and low in overall production cost.

Description

Technical Field

[0001] This invention relates to the field of display device technology, and in particular to a display module and its manufacturing method. Background Technology

[0002] The manufacturing methods for small-pitch display modules include discrete device (SMD), integrated Mini LED (IMD), and chip onboard (COB). Currently, large-size LED displays can be seamlessly spliced ​​together from a number of small-size display modules. Smaller pixel pitch results in a clearer image. However, when the pixel pitch is smaller than a certain size, neither SMD nor IMD methods can meet the requirements; only the COB method can produce LED displays with even smaller pixel pitches.

[0003] In the current process of manufacturing small-pitch LED display modules using the COB method, the lamination process is very prone to causing dead LEDs, leading to a decrease in production yield. Furthermore, repair after lamination requires several high-precision positioning processes such as adhesive removal, die removal, and solder paste removal, which are complex, difficult to produce, and inefficient, thus increasing the overall equipment cost. Summary of the Invention

[0004] The main objective of this invention is to provide a display module and its manufacturing method, aiming to solve the technical problems of complex processes, low efficiency, and high costs in the manufacturing of small-pitch LED display modules in the prior art.

[0005] To achieve the above objectives, the present invention proposes a method for manufacturing a display module, the method comprising:

[0006] Multiple LED chips are flip-chip soldered in an array onto a circuit board.

[0007] A filler material is injected between the LED chip and the circuit board for the first time to form a filler layer;

[0008] The filler material is injected a second time at a location on the circuit board other than the filler layer, so as to expand the filler layer to cover the circuit board;

[0009] The filler layer is then cured.

[0010] Optionally, the step of flip-chip bonding multiple LED chips in an array onto a circuit board includes:

[0011] A solder layer is deposited on the surface of each LED chip;

[0012] Multiple LED chips are flip-chip mounted in an array on the circuit board, with the solder layer located between the LED chips and the circuit board;

[0013] The LED chip is soldered onto the circuit board by heating the solder layer.

[0014] Optionally, the step of injecting the filler material a second time at a location on the circuit board different from the filler layer to expand the filler layer to cover the circuit board includes:

[0015] In the direction from the first column of LED chips to the last column of LED chips, the filling material is injected for the second time along an "S" shaped path from the top of the first column of LED chips, passing through the gaps between adjacent columns of LED chips, until the bottom of the last column of LED chips.

[0016] Allow the filling material to flow and cover the circuit board.

[0017] Optionally, the height of the filler layer is flush with the height of the LED chip. After the step of curing the filler layer, the method further includes:

[0018] A protective film is applied to the LED chip and the filler layer.

[0019] Optionally, the step of covering the LED chip and the filler layer with a protective film includes:

[0020] An adhesive layer is printed on the filler layer and the LED chip;

[0021] The protective film is then applied to the adhesive layer.

[0022] Optionally, the light transmittance of the protective film is 25% to 85%.

[0023] Optionally, the adhesive layer is a pressure-sensitive adhesive material, the solid content of the adhesive layer is 50-70%, the viscosity of the adhesive layer is 4000-80000 cp, and the specific gravity of the adhesive layer is 0.85-0.98.

[0024] Optionally, the height of the filler layer is higher than the height of the LED chip. After the step of curing the filler layer, the method further includes:

[0025] The filler layer is sandblasted and / or ground and / or polished to make the height of the filler layer flush with the height of the LED chip;

[0026] A protective film is applied to the LED chip and the filler layer.

[0027] Optionally, the filler layer is an epoxy resin with added toner or black dye, or the filler layer is a silicone resin with added toner or black dye.

[0028] Optionally, the surface roughness of the filling layer is 0.01 μm to 5 μm, and the thickness of the filling layer is less than or equal to 500 μm.

[0029] In addition, to solve the above problems, the present invention also proposes a display module, which is manufactured by the display module manufacturing method described above. The display module includes a circuit board and a filling layer. Multiple LED chips are arranged in an array on the circuit board. The filling layer fills the space between the LED chips and the circuit board and covers the circuit board.

[0030] The present invention uses a flip-chip method to improve the stability and reliability of the connection between the LED chip and the circuit board, as well as between each LED chip, by injecting a filler layer between the LED chip and the circuit board and on the circuit board after the LED chip is soldered onto the circuit board. This reduces the occurrence of dead LEDs, improves product yield, and has a simple process, high production efficiency, and low overall production cost. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0032] Figure 1 This is a flowchart illustrating the first embodiment of the display module manufacturing method of the present invention;

[0033] Figure 2 This is a flowchart illustrating the second embodiment of the display module manufacturing method of the present invention;

[0034] Figure 3 This is a flowchart illustrating the third embodiment of the display module manufacturing method of the present invention;

[0035] Figure 4 This is a flowchart illustrating the fourth embodiment of the display module manufacturing method of the present invention;

[0036] Figure 5 This is a top view of the display module of the present invention;

[0037] Figure 6 This is a side view of an embodiment of the display module of the present invention;

[0038] Figure 7 This is a top view of another embodiment of the display module of the present invention.

[0039] Explanation of icon numbers:

[0040] label name label name 10 circuit board 20 LED chips 30 Protective film 40 Fill layer

[0041] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0044] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0045] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0047] This invention provides a display module and its manufacturing method. Please refer to [link / reference]. Figure 1 , Figure 1This is a flowchart illustrating the first embodiment of the display module manufacturing method of the present invention. The display module manufacturing method includes the following steps:

[0048] Step S10: Flip-chip solder multiple LED chips in an array onto circuit board 10;

[0049] Step S20: A filler material is injected between the LED chip and the circuit board 10 for the first time to form a filler layer 40;

[0050] Step S30: Inject the filler material a second time at a location on the circuit board 10 different from the filler layer 40, so as to expand the filler layer 40 to cover the circuit board 10;

[0051] Step S40: Curing the filler layer 40.

[0052] The circuit board 10 has two sides. One side is provided with electrodes or pads, on which multiple LED chips are flip-mounted in an array and soldered to the electrodes or pads on the circuit board 10. The other side is used to connect and fix with an external driver chip. The circuit board 10 can have a size of less than or equal to 150μm*300μm.

[0053] The LED chips are red, green, and blue LED chips, which are arranged in a preset order to form a pixel unit, such as a line arrangement. Multiple pixel units are then flip-mounted onto the circuit board 10 in a matrix configuration. Finally, the LED chips are soldered onto the electrodes or pads of the circuit board 10 using reflow soldering or laser soldering.

[0054] After the LED chip is soldered, there is a gap between the bottom of the LED chip and the surface of the circuit board 10. In this embodiment, a filler material can be injected between the LED chip and the circuit board 10 using a syringe to form the filler layer 40. Simultaneously, the filler material is also injected into the portion of the circuit board 10 that is different from the filler layer 40 using the syringe. It should be noted that the portion different from the filler layer 40 refers to the edge portion of the circuit board 10 and the gap between any two adjacent LED chips, thus covering the entire circuit board 10. After injecting the filler material, the filler layer 40 is cured. The function of the filler layer 40 is to fill the gap between the LED chip and the circuit board 10, fill the gap between any two adjacent LED chips, and wrap around the outermost LED chip, thereby improving the connection between the LED chip and the circuit board 10, increasing stability, and improving the stability of the connection between adjacent LED chips.

[0055] It should be noted that in this embodiment, the filler material can be cured by UV curing or by heat curing. During the curing process, step S10 specifically includes:

[0056] Step S11: A solder layer is deposited on the surface of each of the LED chips;

[0057] Step S12: A plurality of LED chips are flip-chip mounted in an array on the circuit board 10, with the solder layer located between the LED chips and the circuit board 10;

[0058] Step S13: Heat the solder layer to solder the LED chip onto the circuit board 10.

[0059] The solder layer is pre-plated on the surface of each LED chip, and the chips are then mounted onto the circuit board 10 using a flip-chip mounting method. The electrodes or pads on the circuit board 10 are metal components. Because the solder layer is pre-plated on the LED chips, problems such as poor soldering or insufficient soldering area caused by air bubbles after the solder layer connects to the electrodes or pads on the circuit board 10 can be avoided. This also prevents the LED chips from detaching from the electrodes or pads on the circuit board 10 due to the expansion and contraction of the filler material during curing.

[0060] The present invention improves the stability and reliability of the connection between the LED chip and the circuit board 10 and between each LED chip by flip-chip bonding after the LED chip is soldered onto the circuit board 10, and by injecting the filler layer 40 between the LED chip and the circuit board 10 and onto the circuit board 10. This reduces the occurrence of dead LEDs, improves product yield, and has a simple process, high production efficiency, and low overall production cost.

[0061] Further, please refer to Figure 2 , Figure 2 This is a flowchart illustrating the second embodiment of the display module manufacturing method of the present invention. Step S30 includes:

[0062] Step S31: In the direction from the first column of LED chips to the last column of LED chips, the filling material is injected for the second time along an "S" shaped path from the top of the first column of LED chips, passing through the gaps between adjacent columns of LED chips, until the bottom of the last column of LED chips.

[0063] Step S32: Allow the filling material to flow and cover the circuit board 10.

[0064] In this embodiment, please refer to Figure 5 The first column of LED chips is defined as the row of LED chips closest to the edge, and the corresponding row of LED chips to the opposite edge is defined as the last column of LED chips. It can be understood that the top of the first column of LED chips is the side facing away from the last column of LED chips, and the bottom of the last column of LED chips is the side facing away from the first column of LED chips.

[0065] The filler material is injected starting from one end of the first column of LED chips. After reaching the other end of the first column of LED chips, it moves towards the last column of LED chips, until it reaches the gap between the first and second columns of LED chips. It then moves back along the gap between the first and second columns of LED chips. This process is repeated sequentially down to the gap between the second and third columns of LED chips, forming an "S"-shaped path. The filler material is fluid before it solidifies, so after injection, it flows between adjacent LED chips in the same column, thus covering the entire area of ​​the circuit board 10 where no LED chips are installed. In this embodiment, the injection of filler material onto the entire circuit board 10 can be completed with only one movement of the syringe, further improving production efficiency.

[0066] Further, please refer to Figure 3, Figure 3 This is a flowchart illustrating the third embodiment of the display module manufacturing method of the present invention. The height of the filling layer 40 is flush with the height of the LED chip. After step S40, the following steps are also included:

[0067] Step S50: Cover the LED chip and the filling layer 40 with a protective film 30.

[0068] Please refer to Figure 6 The filler layer 40 comprises either an opaque thermosetting material or a UV-curable material. Specifically, the opaque thermosetting material can be silicone resin doped with carbon powder, epoxy resin doped with carbon powder, silicone resin doped with black dye, or epoxy resin doped with black dye, etc., with a light transmittance ranging from 0% to 49%. This provides the black background required by the display module, resulting in high black color consistency. It also prevents light interference between the LED chips.

[0069] As one embodiment, by maintaining a constant flow rate of filler material from the syringe and injecting the filler material according to the preset time, the injection volume or weight of the filler material can be controlled. The preset time can be adjusted according to different models and sizes of products.

[0070] In this embodiment, the filling material injected according to the preset time is flush with the height of the LED chip, and the filling layer 40 formed after curing is also flush with the height of the LED chip. Then, the protective film 30 is covered on the surfaces of the filling layer 40 and the LED chip. The protective film 30 protects the LED chip, smooths the surface of the entire display module, and provides light diffusion for the LED chip.

[0071] In the above process, the curing method of the filler material can be adjusted according to the material of the filler material. For example, it can be cured by heating in an oven or by ultraviolet irradiation with a UV lamp. After the filler layer 40 is cured, a portion of the adhesive material of the filler layer 40 can be removed by grinding and polishing processes to achieve a corresponding thickness, which can be less than or equal to 500 μm. The surface is roughened by grinding and polishing processes to reduce light reflection on the surface of the protective film 30 and increase the viewing angle of the display module. The roughness Ra value can be set in the range of 0.01 μm to 5 μm.

[0072] It should be noted that, in this embodiment, step S50 specifically includes:

[0073] Step S51: Print an adhesive layer on the filler layer 40 and the LED chip;

[0074] Step S52: Cover the adhesive layer with the protective film 30.

[0075] The protective film 30 is black, with a light transmittance adjusted to between 25% and 85%, and a heat resistance of 180 degrees Celsius. It is made of materials such as PET, PC, and FPC. First, the adhesive layer is printed on the filler layer 40 and the LED chip. The adhesive layer material includes transparent resins, such as silicone resin and epoxy resin, which are pressure-sensitive adhesives that can completely adhere to the LED chip and effectively fill small gaps. It has a solid content of 50-70%, a viscosity of 4000-80000 cp, a specific gravity of 0.85-0.98, and an adjustable thickness. It can be removed using solvents including ethanol, acetone, and isopropanol. The adhesive layer is a pressure-sensitive adhesive with a solid content of 50-70%, a viscosity of 4000-80000 cp, and a specific gravity of 0.85-0.98.

[0076] In this embodiment, the protective film 30 can be detachably connected to the filler layer 40 and the LED chip through the adhesive layer, thereby avoiding damage or open circuit (dead LED) of the LED chip during the manufacturing process and the subsequent repair problems.

[0077] Further, please refer to Figure 4 , Figure 4 This is a flowchart illustrating the fourth embodiment of the display module manufacturing method of the present invention. The height of the filling layer 40 is higher than the height of the LED chip. After step S40, the following steps are also included:

[0078] Step S60: Sandblast and / or grind and / or polish the filling layer 40 so that the height of the filling layer 40 is flush with the height of the LED chip;

[0079] Step S70: Cover the LED chip and the filling layer 40 with a protective film 30.

[0080] As another embodiment, please refer to Figure 7In this embodiment, during the injection of filler material onto the circuit board 10, the filler material can be directly injected using a syringe until it covers the LED chip. The curing method of the filler material can be adjusted according to its material composition, such as curing by heating in an oven or by UV irradiation. After the filler layer 40 is cured, the portion submerged in the LED chip can be removed by grinding and polishing processes to achieve the appropriate thickness, which can be less than or equal to 500 μm. The surface is roughened by grinding and polishing processes to reduce light reflection from the surface of the protective film 30 and increase the viewing angle of the display module. The roughness Ra value can be set in the range of 0.01 μm to 5 μm, and the thickness of the filler layer is less than or equal to 500 μm. The filler material includes silicone resin or epoxy resin doped with carbon powder or dye and with the ink color adjusted to a transmittance of 25% to 49%.

[0081] In addition, to solve the above problems, the present invention also proposes a display module, which is manufactured by the display module manufacturing method described above. The display module includes a circuit board 10, on which a plurality of LED chips are arranged in an array. A fill layer 40 is provided between the LED chips and the circuit board 10 at a position different from that of the LED chips.

[0082] The circuit board 10 has two sides. One side is provided with electrodes or pads, on which multiple LED chips are flip-mounted in an array and soldered to the electrodes or pads on the circuit board 10. The other side is used to connect and fix with an external driver chip. The circuit board 10 can have a size of less than or equal to 150μm*300μm.

[0083] The LED chips are red, green, and blue LED chips, which are arranged in a preset order to form a pixel unit, such as a line arrangement. Multiple pixel units are then flip-mounted onto the circuit board 10 in a matrix configuration. Finally, the LED chips are soldered onto the electrodes or pads of the circuit board 10 using reflow soldering or laser soldering.

[0084] After the LED chip is soldered, there is a gap between the bottom of the LED chip and the surface of the circuit board 10. In this embodiment, a filler material can be injected into the gap between the LED chip and the circuit board 10 using a syringe. Simultaneously, the filler material is also injected into the portion of the circuit board 10 that is different from the LED chip using the syringe. It should be noted that the portion different from the LED chip refers to the edge of the circuit board 10 and the gap between any two adjacent LED chips. After injecting the filler material, the filler material is cured to form the filler layer 40. The function of the filler layer 40 is to fill the gap between the LED chip and the circuit board 10, fill the gap between any two adjacent LED chips, and wrap around the outermost LED chip, thereby improving the connection between the LED chip and the circuit board 10, increasing stability, and improving the stability of the connection between adjacent LED chips.

[0085] It should be noted that in this embodiment, the filler material can be cured by UV curing or heat curing. During the curing process, the solder layer is pre-plated on the surface of the LED chip and then mounted onto the circuit board 10 using a flip-chip mounting method. Since the electrodes or pads on the circuit board 10 are metal parts, the pre-plating of the solder layer on the LED chip avoids problems such as poor soldering or insufficient soldering area caused by air bubbles after the solder layer connects to the electrodes or pads on the circuit board 10. This also prevents the LED chip from detaching from the electrodes or pads on the circuit board 10 due to the expansion and contraction of the filler material during the curing process.

[0086] The present invention improves the stability and reliability of the connection between the LED chip and the circuit board 10 and between each LED chip by flip-chip bonding after the LED chip is soldered onto the circuit board 10, and by injecting the filler layer 40 between the LED chip and the circuit board 10 and onto the circuit board 10. This reduces the occurrence of dead LEDs, improves product yield, and has a simple process, high production efficiency, and low overall production cost.

[0087] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for manufacturing a display module, characterized in that, The method for manufacturing the display module includes: Multiple LED chips are flip-chip soldered in an array onto a circuit board. A filler material is injected for the first time into the gap between the LED chip and the circuit board to form a filler layer; The filler material is injected a second time at a location on the circuit board other than the filler layer, so as to expand the filler layer to cover the circuit board; The filler layer is cured; The portion different from the filling layer refers to the edge portion of the circuit board and the gap between any two adjacent LED chips; The steps of flip-chip bonding multiple LED chips in an array onto a circuit board include: A solder layer is deposited on the surface of each LED chip; Multiple LED chips are flip-chip mounted in an array on the circuit board, with the solder layer located between the LED chips and the circuit board; The LED chip is soldered onto the circuit board by heating the solder layer.

2. The method for manufacturing a display module according to claim 1, characterized in that, The step of injecting the filler material a second time at a location on the circuit board different from the filler layer to expand the filler layer to cover the circuit board includes: In the direction from the first column of LED chips to the last column of LED chips, the filling material is injected in an "S" shaped path from the top of the first column of LED chips, passing through the gaps between adjacent columns of LED chips, until the bottom of the last column of LED chips. Allow the filling material to flow and cover the circuit board.

3. The method for manufacturing a display module according to claim 1, characterized in that, The height of the filler layer is flush with the height of the LED chip. After the step of curing the filler layer, the method further includes: A protective film is applied to the LED chip and the filler layer.

4. The method for manufacturing a display module according to claim 3, characterized in that, The step of covering the LED chip and the filler layer with a protective film includes: An adhesive layer is printed on the filler layer and the LED chip; The protective film is then applied to the adhesive layer.

5. The method for manufacturing a display module according to claim 4, characterized in that, The light transmittance of the protective film is 25%~85%.

6. The method for manufacturing a display module according to claim 5, characterized in that, The adhesive layer is a pressure-sensitive adhesive material, the solid content of the adhesive layer is 50-70%, the viscosity of the adhesive layer is 4000-80000 cp, and the specific gravity of the adhesive layer is 0.85-0.

98.

7. The method for manufacturing a display module according to claim 1, characterized in that, The height of the filler layer is higher than the height of the LED chip. After the step of curing the filler layer, the method further includes: The filler layer is sandblasted and / or ground and / or polished to make the height of the filler layer flush with the height of the LED chip; A protective film is applied to the LED chip and the filler layer.

8. The method for manufacturing a display module according to any one of claims 1 to 7, characterized in that, The filler layer is an epoxy resin with added toner or black dye, or the filler layer is a silicone resin with added toner or black dye.

9. The method for manufacturing a display module according to any one of claims 1 to 7, characterized in that, The surface roughness of the filling layer is 0.01μm to 5μm, and the thickness of the filling layer is less than or equal to 500μm.

10. A display module, characterized in that, The display module is manufactured using the display module manufacturing method as described in any one of claims 1 to 9. The display module includes a circuit board and a filling layer. A plurality of LED chips are arranged in an array on the circuit board. The filling layer fills the space between the LED chips and the circuit board and covers the circuit board.

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