Common cathode structure of vertical LED pixel package

Abstract

A common cathode structure of a vertical light-emitting diode (LED) pixel package, comprising a package substrate, a plurality of vertical LED dies, a conductive pillar, an insulating isolation support, and a common cathode metal film layer. The plurality of vertical LED dies are arranged above the package substrate; the package substrate is provided with a plurality of anodes penetrating through the body of the package substrate and a common cathode as external contact points of electrodes below; the plurality of anodes are respectively and electrically connected to P electrodes of the plurality of vertical LED dies; the conductive pillar is electrically connected to the common cathode and N electrodes of the plurality of vertical LED dies; the common cathode metal film layer is formed on the plurality of vertical LED dies, the conductive pillar, and the insulating isolation support and electrically conducts the conductive pillar and the plurality of N electrodes. In this way, the plurality of anodes and the common cathode are in the same plane, and the requirements of small-spacing LED display modules for SMT application are met.

Description

Common cathode electrode structure of vertical LED pixel package Technical Field

[0001] The present invention relates to a package element structure using vertical light emitting diode chips, and more particularly to a common cathode electrode structure of a vertical LED pixel package. Background Art

[0002] LED chips can be mainly divided into three types based on their appearance, electrode arrangement, and the direction of current in the semiconductor layer: 1. horizontal type (horizontal) 2. vertical type (vertical) 3. flip-chip type (flip-chip).

[0003] Horizontal and vertical LED dies are the simplest die types, but both require a wire bonding process to electrically connect their electrodes to the package carrier. See Figures 1A and 1B for a top view and a side cross-sectional view of the wire bonding structure of a vertical LED. The die comprises a package carrier 1 on which are disposed a blue LED die 2, a green LED die 3, and a red LED die 4. The N electrodes 5 of the blue, green, and red LED dies 2, 3, and 4 are each electrically connected to a common cathode pad 7 via a metal bonding wire 6. This structure has low process efficiency and presents reliability issues, with the risk of wafer damage due to the wire bonding process.

[0004] To avoid the aforementioned bonding issues, current LED displays primarily use flip-chip LED chips that do not require bonding.

[0005] The flip-chip LED die and package substrate are electrically connected using a bottom-bonded conductive method for both the P and N electrodes, eliminating the need for wire bonding above the light-emitting surface. Instead, the N and P electrodes (P / N electrodes) underneath the die are conductively bonded to the package substrate via electrode pads, avoiding the drawbacks of wire bonding.

[0006] LED displays with finer pixel pitches (e.g., pixel pitches less than 0.75mm) require smaller red, green, and blue LED die (e.g., die less than 125μm x 125μm) for their pixel packages. Small flip-chip LED die are susceptible to the risk of bottom short circuits. This is because both the N and P electrodes on the bottom of the die are conductively bonded to the package substrate, typically using conductive solder paste. As die size decreases, the P and N electrodes on the same plane at the bottom of the flip-chip LED die become increasingly close, making it more susceptible to diffusion of conductive material during the precision metal bonding process, potentially causing an immediate short circuit or long-term reliability failure.

[0007] Summary of the Invention

[0008] Therefore, the primary objective of the present invention is to disclose a common cathode electrode structure for a vertical LED pixel package. This structure electrically connects the vertical LED die to the package substrate without the need for metal bonding. This avoids the current disadvantage of mainstream small-sized flip-chip LED die during the packaging process, where the electrodes on the same plane are too close together and prone to short circuits. This facilitates the mass production of highly reliable, high-contrast, and high-definition MiniLED dipslays.

[0009] The present invention is a common cathode electrode structure of a vertical light emitting diode pixel package, which includes a packaging loading plate, a plurality of vertical light emitting diode crystal grains, a conductive column, an insulating isolation support and a common cathode metal film layer.

[0010] The package carrier has a plurality of anodes and a common cathode, and the anodes and the common cathode respectively penetrate the package carrier. The plurality of vertical LED dies are disposed on the package carrier, and each of the plurality of vertical LED dies comprises a conductive carrier, a vertical LED structure, an N-electrode, and a P-electrode. The vertical LED structure is fixed to the conductive carrier, the N-electrode is electrically connected to the top of the vertical LED structure, the P-electrode is electrically connected to the bottom of the conductive carrier, and the plurality of anodes correspond to and are electrically connected to the P-electrodes of the plurality of vertical LED dies.

[0011] The conductive column is disposed on the package carrier and electrically connected to the common cathode, and the N electrodes of the plurality of vertical light emitting diode chips and an upper contact surface of the conductive column have a common plane.

[0012] The insulating isolation support is disposed on the package carrier and fills the space between the conductive pillars and the plurality of vertical LED dies, filling the space until it is flush with the common plane. The insulating isolation support also covers a sidewall of the plurality of vertical LED dies. The common cathode metal film layer is formed on the N-electrodes of the plurality of vertical LED dies, the conductive pillars, and the insulating isolation support, and the common cathode metal film layer electrically connects the conductive pillars and the N-electrodes of the plurality of vertical LED dies.

[0013] Accordingly, the present invention, by providing the common cathode metal film layer and the conductive pillar, allows the multiple N electrodes to be electrically connected to the common cathode of the package carrier, and the multiple P electrodes to be electrically connected to the multiple anodes of the package carrier, respectively. The multiple anodes and the common cathode are coplanar. With the common cathode design of the present invention, when the red, green, and blue vertical LED chips constitute a single pixel, the luminous intensity of each of the red, green, and blue vertical LED chips within the single pixel can be controlled through the independent circuits of each of the red, green, and blue vertical LED chips, thereby achieving full-color pixel requirements and being applicable to LED displays. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG1A is a top view schematic diagram of a conventional vertical LED bonding structure;

[0015] FIG1B is a schematic side cross-sectional view of a conventional vertical LED bonding structure;

[0016] FIG2A is a schematic cross-sectional view of the structure of a vertical light-emitting diode die according to the present invention;

[0017] FIG2B is a schematic top view of the structure of a vertical light emitting diode die according to the present invention;

[0018] FIG3A is a schematic top view of the structure of the present invention;

[0019] FIG3B is a schematic cross-sectional view of the structure of the present invention;

[0020] FIG4 is a schematic diagram of the blackening of the surface structure of the present invention;

[0021] 5A to 5D are structural cross-sectional views of the manufacturing process of the present invention;

[0022] FIG6A is a schematic diagram of the present invention; FIG6A is a schematic diagram of the present invention;

[0023] FIG6B is a second schematic diagram of the present invention;

[0024] 7-10 are schematic diagrams showing the relative positions of the vertical light-emitting diode die and the conductive pillars of the present invention. DETAILED DESCRIPTION

[0025] In order to have a deeper understanding and recognition of the features, objectives and effects of the present invention, a preferred embodiment is listed below with reference to the accompanying drawings:

[0026] Please refer to "Figures 2A" and "2B," which are schematic cross-sectional and top-down views of the structure of a vertical LED die 10 according to the present invention. In one embodiment, the vertical LED die 10 according to the present invention includes a conductive carrier 11, a vertical LED structure 12, an N-electrode 13, and a P-electrode 14. The vertical LED structure 12 is fixed to the conductive carrier 11. The N-electrode 13 is electrically connected to the top of the vertical LED structure 12, and the P-electrode 14 is electrically connected to the bottom of the conductive carrier 11. In one embodiment, the conductive carrier 11 includes a surrogate substrate 111 and an adhesive layer 112 stacked in sequence. The surrogate substrate 111 is made of a material with high thermal conductivity and electrical conductivity, such as a silicon substrate. The vertical LED structure 12 includes a structural metal layer 121, a conductive reflective layer 122, a P-type semiconductor layer 123, a light-emitting layer 124, and an N-type semiconductor layer 125 stacked in sequence. The adhesive layer 112 bonds the structural metal layer 121 to fix the vertical light-emitting diode structure 12 on the conductive carrier 11. The N-electrode 13 is electrically connected to the N-type semiconductor layer 125 in an ohmic contact, while the P-electrode 14 is electrically connected to the alternative substrate 111 to be conductive with the P-type semiconductor layer 123. Accordingly, applying a voltage to the N-electrode 13 and the P-electrode 14 can form a voltage difference between the P-type semiconductor layer 123 and the N-type semiconductor layer 125 to drive the light-emitting layer 124 to emit light. And by changing the epitaxial material used for the light-emitting layer 124, the light-emitting layer 124 can emit red light, green light, and blue light. Preferably, the N-electrode 13 of the vertical light-emitting diode chip 10 of the present invention is placed on the side of the vertical light-emitting diode chip 10.

[0027] Please refer to "Figure 3A" and "Figure 3B" again. The present invention is a common cathode electrode structure of a vertical light-emitting diode pixel package, which includes a plurality of vertical light-emitting diode chips 10, a conductive column 20, an insulating isolation support body 30, a common cathode metal film layer 40 and a sealing loading plate 50.

[0028] The package carrier 50 has a plurality of anodes 51 and a common cathode 52, and the plurality of anodes 51 and the common cathode 52 respectively penetrate the package carrier 50. The plurality of vertical light-emitting diode dies 10 are disposed on the package carrier 50, and the plurality of anodes 51 respectively correspond to and are electrically connected to the P electrodes 14 of the plurality of vertical light-emitting diode dies 10. In one embodiment, the package carrier 50 is rectangular and has an area between 0.04 mm 2 to 1.96mm 2 (square millimeters). If it is a square, the side length is 0.20mm*0.20mm to 1.4mm*1.4mm (millimeters).

[0029] The conductive pillars 20 are disposed on the package carrier 50 and electrically connected to the common cathode 52. The N-electrodes 13 of the plurality of vertical LED dies 10 and an upper contact surface 21 of the conductive pillars 20 share a common plane 211. The conductive pillars 20 are preferably made of tin, copper, gold, aluminum, or the like. Highly conductive semiconductor materials such as N-type semiconductors, P-type semiconductors, or ITO may also be used.

[0030] The insulating support 30 is disposed on the package carrier 50 and fills the space between the conductive pillars 20 and the plurality of vertical LED dies 10 until it is flush with the common plane 211 (as shown in FIG. 3B ). Furthermore, the insulating support 30 covers a sidewall 101 of the plurality of vertical LED dies 10. Preferably, the insulating support 30 further surrounds the conductive pillars 20 and the plurality of vertical LED dies 10 to form a structure 31, thereby increasing the overall structural strength. The insulating support 30 can be made of a material selected from epoxy, silicon, and the like.

[0031] The common cathode metal film layer 40 is formed on the N electrodes 13 of the plurality of vertical LED dies 10, the conductive pillars 20, and the insulating support 30, and electrically connects the conductive pillars 20 to the N electrodes 13 of the plurality of vertical LED dies 10. In one embodiment, the common cathode metal film layer 40 is formed by any of screen printing, dispensing, or vapor deposition, and has a thickness of at least 3 microns. Screen printing involves printing a conductive colloid, which is a mixture of a colloid and a highly conductive metal, such as tin, copper, silver, or gold.

[0032] Please refer to "Figure 3A" and "Figure 4" again. In one embodiment, the insulating isolation support body 30 is made of a black material. In one embodiment, a black insulating material 60 is screen-printed on the top of the insulating isolation support body 30 to cover the common cathode metal film layer 40, the N electrode 13 and the conductive column 20 and expose a light-emitting area 102 of the multiple vertical light-emitting diode chips 10. More specifically, only the light-emitting area 102 of the multiple vertical light-emitting diode chips 10 is not covered by the black insulating material 60. Therefore, unnecessary metal reflections can be avoided and the contrast can be improved. In one embodiment, the use of a black material for the insulating isolation support body 30 and the screen printing of the black insulating material 60 can be implemented simultaneously to achieve the best contrast.

[0033] Please refer to Figures 5A to 5D . In one embodiment, the manufacturing process begins by affixing the plurality of vertical LED dies 10 and the conductive pillars 20 to the package carrier 50. The anodes 51 are electrically connected to the corresponding P-electrodes 14, and the common cathode 52 is electrically connected to the conductive pillars 20. Next, as shown in Figure 5B , the insulating support 30 is placed between the conductive pillars 20 and the plurality of vertical LED dies 10 until it aligns with the common plane 211. The insulating support 30 is fabricated by any of a variety of methods, including dispensing, spraying, or vacuum infusion. Next, as shown in FIG5C , a common cathode metal film layer 40 is formed on the plurality of vertical LED dies 10, the conductive pillars 20, and the insulating isolation support 30. The common cathode metal film layer 40 is electrically conductive between the conductive pillars 20 and the N electrodes 13 of the plurality of vertical LED dies 10. Finally, as shown in FIG5D , a black insulating material 60 is screen-printed above the common cathode metal film layer 40, the N electrodes 13, the conductive pillars 20, and the insulating isolation support 30, exposing the light-emitting region 102.

[0034] Please refer to "Figure 6A" and "Figure 6B" together. In one embodiment, the structure described in the present invention can meet the needs of mass production. Multiple groups of vertical LED chips 10 and conductive pillars 20 can be first arranged on a large packaging carrier 50A. The large packaging carrier 50A is an aggregate of multiple packaging carriers 50. After the process of screen printing the black insulating material 60 is completed (see "Figure 5D"), the large packaging carrier 50A is cut along the cutting line 53 to break it into multiple packaging carriers 50.

[0035] Referring again to FIG. 7 , in one embodiment, the package carrier 50 includes three vertical LED dies 10 that are rectangular in shape when viewed from above. The conductive pillars 20 are also rectangular in shape when viewed from above. The three vertical LED dies 10 emit red, green, and blue light, respectively. The three vertical LED dies 10 are arranged side by side with their long sides close together. The long sides of the conductive pillars 20 are close to the short sides of the three vertical LED dies 10. Furthermore, the common cathode metal film layer 40 electrically connects the conductive pillars 20 and the multiple vertical LED dies 10.

[0036] Please refer to "Figure 8" again. In one embodiment, the plurality of vertical LED chips 10 on the package carrier 50 are three and have a rectangular shape when viewed from above. The conductive pillars 20 are also rectangular when viewed from above. The three vertical LED chips 10 respectively emit red light, green light, and blue light. The three vertical LED chips 10 and the conductive pillars 20 are arranged side by side with their long sides close together. The common cathode metal film layer 40 electrically connects the conductive pillars 20 and the plurality of vertical LED chips 10.

[0037] Please refer to "Figure 9" again. In one embodiment, the plurality of vertical LED chips 10 on the package carrier 50 are three and rectangular in shape when viewed from above, and the conductive pillars 20 are also rectangular in shape when viewed from above. The three vertical LED chips 10 respectively emit red light, green light, and blue light, and the three vertical LED chips 10 and the conductive pillars 20 are arranged in a 2*2 rectangle. The common cathode metal film layer 40 electrically connects the conductive pillars 20 and the plurality of vertical LED chips 10.

[0038] Please refer to "Figure 10" again. To simplify subsequent manufacturing processes and increase the speed of mass production, in practice, multiple pixels 70 can be disposed on the same pixel carrier 50B. More specifically, the pixel carrier 50B is a combination of multiple package carriers 50, without any subdivision. In one embodiment, the conductive pillars 20 and the common cathode metal film layer 40 are provided in multiple configurations, each of which is paired with three vertical light-emitting diode dies 10 (emitting red, green, and blue light, respectively) to form the pixel 70. Multiple pixels 70 are disposed on the same pixel carrier 50B.

[0039] As described above, the features of the present invention include at least:

[0040] 1. The present invention, by providing the common cathode metal film layer and the conductive pillar, allows the multiple N electrodes to be electrically connected to the common cathode of the package carrier, and the multiple P electrodes to be electrically connected to the multiple anodes of the package carrier. The multiple anodes and the common cathode are coplanar, which can meet the requirements of mainstream SMT packaging technology.

[0041] 2. The present invention has a common cathode design. When the red, green, and blue vertical LED chips form a single pixel, the luminous intensity of each red, green, and blue vertical LED chip can be controlled through independent circuits within the single pixel to achieve full-color pixel requirements. This can be applied to LED displays.

[0042] 3. The vertical light-emitting diode die of the present invention is a vertical LED die, which avoids the reliability risk of short circuits in conventional flip-chip LED die. At the same time, the present invention does not require a wire bonding process and can be combined with a surface blackening treatment, which can meet the mass production requirements of high-quality and high-contrast MiniLED Dipslay.

[0043] 4. The structure of the present invention allows multiple groups of vertical LED dies and the conductive pillars to be first placed on the large package carrier. After the process of printing the black insulating material is completed, the dicing process is then carried out. This provides the option of one pixel per carrier or multiple pixels per carrier, meeting the needs of mass production and simplifying subsequent processes.

Claims

1. A common cathode electrode structure of a vertical light emitting diode pixel package, characterized in that Include: A packaging carrier, the packaging carrier having a plurality of anodes and a common cathode, and the plurality of anodes and the common cathode respectively penetrate the packaging carrier; A plurality of vertical light-emitting diode dies, the plurality of vertical light-emitting diode dies are disposed on the package carrier, and the plurality of vertical light-emitting diode dies respectively comprise a conductive carrier, a vertical light-emitting diode structure fixed on the conductive carrier, an N electrode electrically connected to the upper part of the vertical light-emitting diode structure, and a P electrode electrically connected to the lower part of the conductive carrier, the plurality of anodes respectively correspond to and are electrically connected to the P electrodes of the plurality of vertical light-emitting diode dies; A conductive column, which is disposed on the package carrier and electrically connected to the common cathode, and the N electrodes of the plurality of vertical light-emitting diode chips and an upper contact surface of the conductive column have a common plane; An insulating isolation support body is disposed on the package carrier and filled between the conductive column and the plurality of vertical light emitting diode dies and filled to be flush with the common plane, and the insulating isolation support body covers a side wall of the plurality of vertical light emitting diode dies; as well as A common cathode metal film layer is formed on the N electrodes of the plurality of vertical light emitting diode grains, the conductive column and the insulating isolation support and electrically connects the conductive column and the N electrodes of the plurality of vertical light emitting diode grains.

2. The common cathode electrode structure according to claim 1, characterized in that: The insulating isolation support body is made of black material.

3. The common cathode electrode structure according to claim 1, characterized in that: A black insulating material is screen-printed on the insulating isolation support body to cover the common cathode metal film layer, the N electrode and the conductive column and expose a light emitting area of ​​the plurality of vertical light emitting diode crystal grains.

4. The common cathode electrode structure according to claim 1, characterized in that: The insulating isolation support body is made of black material, and a black insulating material is screen-printed on the insulating isolation support body to cover the common cathode metal film layer, the N electrode and the conductive column and expose a light emitting area of ​​the plurality of vertical light emitting diode grains.

5. The common cathode electrode structure according to claim 1, characterized in that: The plurality of vertical light-emitting diode chips have three and are rectangular in shape when viewed from above, and the conductive column is also rectangular in shape when viewed from above. The three vertical light-emitting diode chips emit red light, green light and blue light respectively, and the three vertical light-emitting diode chips are arranged side by side with their long sides close to each other, and the long side of the conductive column is close to the short sides of the three vertical light-emitting diode chips.

6. The common cathode electrode structure according to claim 1, characterized in that: The plurality of vertical LED chips have three and are rectangular in top view, and the conductive column is also rectangular in top view. The three vertical LED chips emit red light, green light and blue light respectively, and the three vertical LED chips and the conductive column are arranged in parallel with their long sides close to each other.

7. The common cathode electrode structure according to claim 1, characterized in that: The plurality of vertical LED chips have three and are rectangular in top view, and the conductive column is also rectangular in top view. The three vertical LED chips emit red light, green light and blue light respectively, and the three vertical LED chips and the conductive column are arranged in a 2*2 rectangle.

8. The common cathode electrode structure according to claim 1, characterized in that: The conductive column and the common cathode metal film layer have a plurality of them, and the plurality of the conductive columns and the plurality of the common cathode metal film layers are arranged one to one and are respectively matched with three vertical light emitting diode grains that emit red light, green light, and blue light to form a pixel, and the package carrier is configured with a plurality of the pixels.

9. The common cathode electrode structure according to claim 1, characterized in that: The package carrier is rectangular and has an area ranging from 0.04 square millimeters to 1.96 square millimeters.

10. The common cathode electrode structure according to claim 1, characterized in that: The common cathode metal film layer is made by any method of screen printing, dispensing and evaporation.

11. The common cathode electrode structure according to claim 1, characterized in that: The thickness of the common cathode metal film layer is at least 3 microns.

12. The common cathode electrode structure according to claim 1, characterized in that: The insulating isolation support body is made by any method of dispensing, spraying or vacuum infusion.

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