A manufacturing method of MIP-RGB lamp beads

Abstract

The application discloses a kind of manufacturing methods of MIP-RGB lamp bead, comprising the following steps: S1, paste adhesive film on steel plate;S2, RGB three color chips are arranged on the adhesive film according to predetermined pattern, wherein R chip is vertical structure positive chip, P electrode faces down, N electrode faces up;G chip and B chip are positive chip, P electrode and N electrode are all located on the front of chip, and are placed in face-down mode;S3, molding encapsulation is carried out on the chip after arranging, and dark packaging glue is filled;S4, aperture is carried out on the encapsulation body after molding, and chip electrode is exposed;S5, front circuit layer and back circuit layer are respectively made;S6, optical adhesive is attached on the light emitting surface of encapsulation body;S7, encapsulation panel is cut into independent MIP-RGB lamp bead.The application adopts the mode of molding encapsulation and then making circuit, realizes the hybrid encapsulation of vertical structure R chip and positive G, B chip, and solves the compatibility problem of different chip electrode direction.

Description

Technical Field

[0001] This invention relates to the field of LED packaging technology, and specifically to a method for manufacturing MIP-RGB LED chips. Background Technology

[0002] Traditional RGB LED chip packaging mainly employs two mainstream methods: the first involves mounting the LED chips onto a metal frame, followed by processes such as die bonding, wire bonding, and encapsulation; the second involves tinning the substrate, followed by processes such as die bonding, reflow soldering, and encapsulation. Both of these traditional packaging methods suffer from the following problems: 1) Low production efficiency, with limited capacity per packaging unit; 2) High packaging costs and significant material waste; 3) Difficulty in ensuring chip alignment accuracy, affecting light emission uniformity; 4) Inability to adapt to the trend of miniaturization packaging, making high-density integration difficult; and 5) Inability to achieve miniaturized packaging of standard LED chipsets, a process already considered mature.

[0003] In recent years, as LED display technology has developed towards smaller pitch, Mini LED, and Micro LED, higher requirements have been placed on packaging processes. MIP (Micro Integrated Package) packaging technology has emerged to meet this need, but traditional MIP packaging processes still suffer from problems such as process complexity, low yield, and high cost. In particular, existing processes are difficult to make compatible when miniaturizing vertically structured chips and upright chips. Summary of the Invention

[0004] The present invention aims to provide a method for manufacturing MIP-RGB LED beads to solve the problems of low production efficiency, high packaging cost, and poor compatibility of different chip structures in existing RGB LED bead packaging processes.

[0005] The technical solution adopted by this invention to solve its technical problem is: A method for manufacturing a MIP-RGB LED chip includes the following steps: S1. Steel plate film application: Applying adhesive film to a steel plate; S2, Arrangement: Arrange the RGB three-color chips on the adhesive film according to a predetermined pattern. The R chip is a vertically mounted chip with the P electrode facing down and the N electrode facing up. The G and B chips are also mounted chips with the P and N electrodes located on the front of the chip and placed face down. S3, Molding Package: Molding package is performed on the chips after they are laid out, and dark-colored encapsulating glue is filled in. S4. Opening: Opening holes in the molded package to expose the electrodes of the RGB three-color chip; S5. Front and back circuit fabrication: A front circuit layer and a back circuit layer are fabricated on the package, respectively. The front circuit layer is connected to the P electrode of the R chip, the P and N electrodes of the G chip, and the P and N electrodes of the B chip. The back circuit layer is connected to the N electrode of the R chip. S6. Apply optical adhesive: Apply optical adhesive to the light-emitting surface of the package; S7. Cutting and Separating: Cut the packaged panel into independent MIP-RGB LED beads.

[0006] As a further improvement to the above technical solution, the adhesive film in step S1 adheres to the steel plate and can stick the chip, and the steel plate has a size of 300-650mm × 300-650mm.

[0007] As a further improvement to the above technical solution, in step S2, the R chip has a size of 89×89μm and a thickness of 152μm, the G chip and B chip have a size of 85μm×135μm and a thickness of 85±15μm, and the P electrode and N electrode both have a size of 45±5μm.

[0008] As a further improvement to the above technical solution, the RGB chip arrangement in step S2 is as follows: each group of RGB chips is arranged in a triangle or parallel and centered in the package, with the chip spacing within the group being 80 to 120 μm and the distance between groups being 400 to 2000 μm.

[0009] As a further improvement to the above technical solution, the dark-colored encapsulating adhesive mentioned in step S3 has a light-shielding rate of ≥70% and an encapsulating adhesive thickness of 150~300μm.

[0010] As a further improvement to the above technical solution, the opening in step S4 can be achieved by laser opening or plasma cleaning to remove adhesive and open the hole, thus exposing the electrode.

[0011] As a further improvement to the above technical solution, the fabrication of the front circuit in step S5 includes: coating photoresist or applying dry film, sputtering a seed layer or chemical copper plating, electroplating a copper layer, removing the photoresist or dry film, and etching the seed layer; the fabrication of the back circuit includes: coating photoresist, sputtering a seed layer or chemical copper plating, electroplating a copper layer, and fabricating pads.

[0012] As a further improvement to the above technical solution, the optical adhesive in step S6 has a light transmittance of ≥70% and a thickness of 50-150μm.

[0013] The beneficial effects of this invention are: 1. This invention uses a post-molding packaging process to expose the chip electrodes and then fabricate the circuit, thereby achieving hybrid packaging of vertical R-chips and upright G / B-chips, solving the compatibility problem of different chip electrode orientations.

[0014] 2. This invention adopts a mixed arrangement of vertical red light chip and upright green and blue chip, which can give full play to the characteristics of vertical chip such as good heat dissipation, high current density and high light efficiency. By setting the front circuit and the back circuit, the upper and lower electrodes of the vertical chip can be brought out at the same time, which simplifies the external connection and facilitates subsequent surface mount application.

[0015] 3. This invention adopts panel-level packaging (PLP) technology, which can simultaneously package tens of thousands of chips on a 600mm×600mm or 300mm×300mm steel plate, increasing production efficiency by 5 to 10 times and reducing packaging costs by 30 to 50%. The overall process is short, low-cost, and has a high yield, making it suitable for large-scale industrial production.

[0016] 4. This invention uses a dark-colored encapsulating adhesive in combination with a transparent encapsulating film to effectively prevent light leakage and improve display contrast. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Fig. 1 This is a flowchart of a method for manufacturing a MIP-RGB LED bead according to the present invention; Fig. 2 This is a schematic diagram of the structure of the MIP-RGB LED bead in Embodiment 1 of the present invention; Fig. 3 This is a top view of the MIP-RGB LED bead in Embodiment 1 of the present invention; Fig. 4 This is a bottom view of the MIP-RGB LED bead in Embodiment 1 of the present invention. Detailed Implementation

[0019] The following will clearly and completely describe the concept, specific structure, and technical effects of the present invention in conjunction with embodiments and accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention. The various technical features in the present invention can be combined interactively without contradicting each other.

[0020] Reference Figs. 1-4 A basic embodiment of the present invention provides a method for manufacturing MIP-RGB LED beads, including the following steps: Step S1, Steel plate film application: Apply adhesive film to the steel plate. The adhesive film adheres to the steel plate and can hold the chip. The size of the steel plate is 300-650×300-650mm.

[0021] S2. Chip Arrangement: Use a high-precision chip mounter to arrange the RGB three-color chips on the adhesive film according to a predetermined pattern. Each group of RGB chips is arranged in a triangle or a straight line. The chip spacing within a group is 80-120μm, and the distance between groups is 400-2000μm. The R chip is a vertically mounted chip with the P electrode facing down and the N electrode facing up. The R chip has a size of 89×89μm and a thickness of 152μm. The G chip and B chip are upright chips, with the P electrode and N electrode both located on the front of the chip and placed face down. The dimensions of the G chip and B chip are both 85μm×135μm and the thickness is 85±15μm. The dimensions of the P electrode and N electrode are both 45±5μm. S3. Molding Encapsulation: Molding encapsulation is performed on the chips after they are laid out. The thickness of the encapsulating adhesive is 150-300μm. Specifically, dark-colored encapsulating adhesive is used for molding encapsulation. The molding temperature is 120-180℃, the pressure is 5-15MPa, and the time is 3-10 minutes. The dark-colored encapsulating adhesive is a high light-blocking material with a light-blocking rate ≥70%. Black thermosetting epoxy resin or semi-cured epoxy resin can be used. S4. Opening: Laser drilling or plasma cleaning (plasma cleaning) to remove adhesive and open holes on the molded package to expose the electrodes of the RGB three-color chip; S5. Front and back circuit fabrication: A front circuit layer and a back circuit layer are fabricated on the package, respectively. The front circuit layer is connected to the P electrode of the R chip, the P and N electrodes of the G chip, and the P and N electrodes of the B chip. The back circuit layer is connected to the N electrode of the R chip. S6. Applying optical adhesive: Applying optical adhesive to the light-emitting surface of the encapsulation. The optical adhesive has a light transmittance of ≥70% and a thickness of 50-150μm. The optical adhesive is made of high-transmittance silicone or optical-grade epoxy resin with a refractive index of 1.41-1.53. S7. Cutting and Separation: The packaged panel is cut into individual MIP-RGB LED beads using a 355nm ultraviolet laser or diamond blade. The cutting accuracy is ±5μm, the cutting width is 20-40μm, and the size of a single LED bead is 1.0mm×1.0mm or 0.65mm×0.65mm, etc.

[0022] In this embodiment, a front circuit is first fabricated on the front side of the package. The fabrication steps for the front circuit are as follows: A. Remove the adhesive film to expose the front of the chip; B. Sputter seed layer, electroplat copper layer, to form front circuit; C. Apply photoresist or dry film, expose and develop to form circuit patterns; D. Electroplated copper layer, with a thickness of 10-25μm and a line width of 8-50μm.

[0023] A back-side circuit is fabricated on the back side of the package. The steps for fabricating the back-side circuit are as follows: E. Sputtered seed layer, wherein the seed layer is a Cr / Cu bilayer structure with a thickness of 50-100 nm; F. Coat the back of the package with photoresist or apply a dry film, then expose and develop to form a circuit pattern; G. Remove the photoresist or apply the dry film, etch the seed layer, and form the back circuit pattern; H. Electroplated copper layer, with a thickness of 10-25μm and a line width of 8-50μm; I. Fabricate pads, namely COM- pad, R+ pad, B+ pad, and G+ pad. The P electrode of the R chip is connected to the R+ pad, the P electrode of the G chip is connected to the G+ pad, the P electrode of the B chip is connected to the B+ pad, and the N electrodes of the R chip, the G chip, and the B chip are all connected to the COM- pad.

[0024] Based on the basic embodiments, the present invention also provides the following specific embodiments: Example 1: A method for manufacturing a MIP-RGB LED chip, the specific steps of which are as follows: Step S1: Apply a transparent adhesive film to a 600mm×600mm 304 stainless steel plate. The film thickness is 50μm and the light transmittance is 98%.

[0025] Step S2: Arrange the wafers using a high-precision pick-and-place machine, wherein: R chip: Vertical structure, P side down, N side up, chip size 89×89×152μm; G chip: upright structure, face down, chip size 85×135×85μm; B chip: upright structure, face down, chip size 85×135×85μm; Each group of RGB chips is arranged in a straight line, with a spacing of 100μm within each group and a spacing of 650μm between groups.

[0026] Step S3: Use a hot molding machine for encapsulation. The encapsulating adhesive is dark epoxy resin. The molding temperature is 150℃, the pressure is 10MPa, the time is 5 minutes, and the thickness of the encapsulating adhesive is 200μm.

[0027] Step S4: Use a 355nm ultraviolet laser to create an opening and remove the adhesive layer on the electrode.

[0028] Step S5: Constructing the circuit on both sides: - Front circuit layer: Cr / Cu seed layer thickness 80nm, electroplated copper layer thickness 15μm, line width and line spacing 8 / 8μm; - Backside circuit layer: Pad size 200μm×200μm, plating thickness 10μm.

[0029] Step S6: Apply optical adhesive. The optical adhesive is a high-transmittance silicone with a thickness of 100μm, a light transmittance of 92%, and a refractive index of 1.47.

[0030] Step S7: Use 355nm ultraviolet laser for cutting, with a single lamp bead size of 1.0mm×1.0mm×0.35mm and a cutting accuracy of ±3μm.

[0031] Tests showed that the MIP-RGB LED chips produced by this process have a 15% higher luminous efficacy, a 40% lower manufacturing cost, and a yield of 98.5%.

[0032] Example 2: The difference from Example 1 is that the spacing between the RGB chip groups in step S2 is 400μm, which is suitable for higher density Mini-LED display applications. Other process parameters are the same, and the fabricated MIP-RGB LED beads have a size of 0.4mm×0.4mm×0.3mm, a luminous efficacy improvement of 12%, and a yield of 97.8%.

[0033] Example 3: The difference from Example 1 is that step S3 uses a segmented molding process. First, a 100μm black encapsulating adhesive is molded, and after curing, a 100μm transparent encapsulating adhesive is molded to form a double-layer structure, which ensures both light-shielding properties and improves light extraction efficiency. Other process parameters are the same, and the prepared MIP RGB LED beads have a 20% improvement in luminous efficacy and a 30% improvement in contrast.

[0034] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A method for manufacturing a MIP-RGB LED bead, characterized in that, Includes the following steps: S1. Steel plate film application: Applying adhesive film to a steel plate; S2, Arrangement: Arrange the RGB three-color chips on the adhesive film according to a predetermined pattern. The R chip is a vertically mounted chip with the P electrode facing down and the N electrode facing up. The G and B chips are also mounted chips with the P and N electrodes located on the front of the chip and placed face down. S3, Molding packaging: Molding packaging is performed on the chips after they are laid out, and dark-colored encapsulating glue is filled in; S4. Opening: Opening holes in the molded package to expose the electrodes of the RGB three-color chip; S5. Front and back circuit fabrication: A front circuit layer and a back circuit layer are fabricated on the package, respectively. The front circuit layer is connected to the P electrode of the R chip, the P and N electrodes of the G chip, and the P and N electrodes of the B chip. The back circuit layer is connected to the N electrode of the R chip. S6. Apply optical adhesive: Apply optical adhesive to the light-emitting surface of the package; S7. Cutting and Separating: Cut the package into individual MIP-RGB LED beads.

2. The manufacturing method of a MIP-RGB LED bead according to claim 1, characterized in that, The adhesive film described in step S1 adheres to the steel plate and can hold the chip. The steel plate has a size of 300-650mm × 300-650mm.

3. The manufacturing method of a MIP-RGB LED bead according to claim 1, characterized in that, In step S2, the R chip has a size of 89×89μm and a thickness of 152μm, the G chip and B chip have a size of 85μm×135μm and a thickness of 85±15μm, and the P electrode and N electrode both have a size of 45±5μm.

4. The manufacturing method of a MIP-RGB LED bead according to claim 1, characterized in that, In step S2, the RGB chips are arranged as follows: each group of RGB chips is arranged in a triangle or parallel pattern and centered in the package. The chip spacing within a group is 80-120 μm, and the distance between groups is 400-2000 μm.

5. The manufacturing method of a MIP-RGB LED bead according to claim 1, characterized in that, The dark-colored encapsulating adhesive mentioned in step S3 has a light-blocking rate of ≥70% and an encapsulating adhesive thickness of 150~300μm.

6. The manufacturing method of a MIP-RGB LED bead according to claim 1, characterized in that, In step S4, the opening can be achieved by laser drilling or plasma cleaning to remove the adhesive and expose the electrode.

7. The manufacturing method of a MIP-RGB LED bead according to claim 1, characterized in that, Step S5 includes the following steps for fabricating the front circuit: applying photoresist or applying a dry film, sputtering a seed layer or electroless copper plating, electroplating a copper layer, removing the photoresist or dry film, and etching the seed layer; the following steps include the following steps for fabricating the back circuit: applying photoresist, sputtering a seed layer or electroless copper plating, electroplating a copper layer, and fabricating pads.

8. The manufacturing method of a MIP-RGB LED bead according to claim 1, characterized in that, The optical adhesive described in step S6 has a light transmittance of ≥70% and a thickness of 50–150 μm.

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