A small-pitch LED with ESD protection function

Abstract

The application relates to a small-pitch LED with an ESD protection function, which comprises a substrate, a light-emitting chip, an ESD protection chip and a light-transmitting layer. The middle part of the substrate is provided with a groove, and the top surface of the substrate is respectively provided with an inner positive electrode pad and an inner negative electrode pad, which extend to the two sides of the bottom end of the groove on the adjacent side. The ESD protection chip is arranged in the groove, and the positive electrode and the negative electrode of the ESD protection chip are electrically connected with the inner positive electrode pad and the inner negative electrode pad respectively. The light-emitting chip is arranged on the substrate and covers the top of the groove, and the positive electrode and the negative electrode on the two sides of the bottom of the light-emitting chip are electrically connected with the inner positive electrode pad and the inner negative electrode pad on the top surface of the substrate respectively, so that the light-emitting chip and the ESD protection chip are vertically stacked, the ESD protection chip is built-in in the groove of the substrate and is vertically layered with the light-emitting chip, the substrate area is not occupied, the overall size of the product can be close to the size of the light-emitting chip, and smaller point spacing application is realized.

Description

Technical Field

[0001] This invention relates to the field of LED light source technology, and in particular to a small-pitch LED with ESD protection function. Background Technology

[0002] Fine-pitch LED display technology is a rapidly developing LED display technology in recent years. By reducing the pixel pitch and increasing pixel density, it can achieve higher display resolution and clearer picture quality. Fine-pitch LED technology mainly achieves higher pixel density by closely arranging LED beads in a small area. Compared with traditional LED displays with larger pixel pitch and difficulty in displaying image details, fine-pitch LED can present more delicate images and more realistic colors.

[0003] To achieve higher pixel density, the LED chip size of fine-pitch LEDs is typically equal to or slightly larger than the LED chip size. This requires the substrate size to be as close as possible to the LED chip size. However, LED chips generally have weak electrostatic discharge (ESD) immunity and are prone to failure due to ESD damage during use. Therefore, ESD protection devices need to be added to the circuit design to improve the LED's ESD immunity. These protective devices occupy PCB layout space, which in turn restricts the improvement of pixel density, becoming a limiting factor for the further development of fine-pitch LEDs towards higher density. Summary of the Invention

[0004] To address the aforementioned problems, this invention discloses a small-pitch LED with ESD protection. By placing the light-emitting chip and the ESD protection chip on different planes, the anti-static function is achieved without increasing the substrate area, thus solving the problem of ESD protection devices affecting pixel density in the prior art.

[0005] The specific technical solution is as follows: A small-pitch LED with ESD protection includes a substrate, a light-emitting chip, an ESD protection chip, and a light-transmitting layer. The substrate has a groove in the middle, and inner positive and inner negative pads are respectively provided on both sides of the top surface of the substrate. Both the inner positive and inner negative pads have a stepped structure, and their adjacent sides extend to both sides of the bottom end of the groove. The ESD protection chip is disposed in the groove, and the positive and negative electrodes on both sides of the bottom end of the ESD protection chip are electrically connected to the inner positive and inner negative pads on the bottom surface of the groove, respectively. The light-emitting chip is disposed on the substrate and covers the groove. The positive and negative electrodes on both sides of the bottom of the light-emitting chip are electrically connected to the inner positive and inner negative electrode pads on the top surface of the substrate, respectively, so that the light-emitting chip and the ESD protection chip are vertically stacked. The light-transmitting layer covers the light-emitting chip on the top surface of the substrate, and the lower end of the light-transmitting layer fills the groove and covers the ESD protection chip. The substrate has an outer positive electrode pad and an outer negative electrode pad on its bottom sides, and through holes are opened on both sides of the substrate. A positive electrode connection part and a negative electrode connection part are embedded in the two through holes, respectively. The two ends of the positive electrode connection part are electrically connected to the outer positive electrode pad and the inner positive electrode pad, respectively, and the two ends of the negative electrode connection part are electrically connected to the outer negative electrode pad and the inner negative electrode pad, respectively.

[0006] Furthermore, both the light-emitting chip and the ESD protection chip are flip-chips, with the electrodes of both chips located at their bottom.

[0007] Furthermore, the bottom electrode material of the light-emitting chip and the ESD protection chip is one or more of gold, silver, and tin.

[0008] Furthermore, the light-emitting chip and the ESD protection chip are respectively connected and fixed to the inner positive electrode pad and the inner negative electrode pad through a eutectic process or a solder paste reflow curing process.

[0009] Furthermore, the height of the top surface of the ESD protection chip does not exceed the height of the top surface of the substrate.

[0010] Furthermore, the Zener voltage of the ESD protection chip is higher than the maximum rated voltage of the light-emitting chip, but lower than the maximum withstand voltage of the light-emitting chip.

[0011] Furthermore, the positive electrode connection and the negative electrode connection are copper conductive pillars, and the diameter of the copper conductive pillars is adapted to the diameter of the through hole.

[0012] Furthermore, fluorescent powder or dispersant is added inside the light-transmitting layer, and the light-transmitting layer is formed by dispensing curing or mold top process.

[0013] Furthermore, the light-transmitting layer is the same size as the substrate.

[0014] Furthermore, the material of the light-transmitting layer is one or more of silicone and epoxy resin.

[0015] The beneficial effects of this invention are reflected in: (1) The present invention embeds the ESD protection chip in the substrate groove and arranges it vertically in layers with the light-emitting chip. It does not require additional space on the substrate plane and does not increase the substrate area. The overall size of the device is determined only by the size of the light-emitting chip and is not related to the specifications of the ESD protection chip. The LED beads can be compressed to a size close to that of the light-emitting chip, supporting display designs with smaller pixel pitch.

[0016] (2) Compared with the solution of setting separate anti-static devices on the PCB, the present invention integrates the ESD protection function into a single LED, which can simplify the circuit layout of the display PCB, save board space, increase the number of pixels per unit area, achieve higher pixel density, and reduce the assembly complexity of the module. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the small-pitch LED of the present invention.

[0018] Figure 2 This is a top view of the small-pitch LED of the present invention.

[0019] Figure 3 This is a bottom structural view of the small-pitch LED of the present invention.

[0020] Explanation of reference numerals in the attached drawings: 1. Substrate; 2. Light-emitting chip; 3. ESD protection chip; 4. Transmitting layer; 5. Inner positive electrode pad; 6. Inner negative electrode pad; 7. Positive electrode connection part; 8. Negative electrode connection part; 9. Outer positive electrode pad; 10. Outer negative electrode pad; 11. Groove. Detailed Implementation

[0021] To make the technical solution of the present invention clearer and more explicit, the present invention will be further described below with reference to the accompanying drawings. Any solution derived by equivalent substitution and conventional reasoning of the technical features of the present invention falls within the protection scope of the present invention.

[0022] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0023] Please see the appendix Figure 1-3 This embodiment provides a small-pitch LED with ESD protection function, which is applied to a high-density LED display module. It can enhance the device's anti-static breakdown capability while avoiding the protective device occupying the planar layout space of the substrate 1, thereby achieving a smaller pixel pitch and a higher display pixel density.

[0024] Small-pitch LEDs include a substrate 1, a light-emitting chip 2, an ESD protection chip 3, and a light-transmitting layer 4. The substrate 1 is made of an insulating material. A rectangular groove 11 is formed in the middle of the substrate 1, with both ends of the groove 11 flush with the ends of the substrate. Inner positive electrode pads 5 and inner negative electrode pads 6 are respectively provided on both sides of the top surface of the substrate 1. Both inner positive electrode pads 5 and inner negative electrode pads 6 have a stepped structure, with their adjacent sides extending to both sides of the bottom end of the groove 11, thus simultaneously distributed on both the top surface of the substrate 1 and the bottom surface of the groove 11. The stepped pads can simultaneously provide electrical connection points for two types of chips of different heights, allowing the light-emitting chip 2 and the ESD protection chip 3 to share the same set of positive and negative electrode pads to form a parallel circuit, eliminating the need for additional layered wiring and simplifying the internal circuit design of the substrate 1. The surface metal layer of the inner positive electrode pads 5 and inner negative electrode pads 6 can be one or more metals such as gold, silver, nickel, palladium, and tin.

[0025] An ESD protection chip 3 is disposed inside the recess 11, and a light-emitting chip 2 is disposed on the substrate 1 and covers the recess 11. The positive and negative terminals on both sides of the bottom of the ESD protection chip 3 are electrically connected to the inner positive pad 5 and inner negative pad 6 on the bottom surface of the recess 11, respectively. The top surface of the ESD protection chip 3 does not exceed the top surface of the substrate 1 to avoid interference with the mounting of the light-emitting chip 2 above. The Zener voltage of the ESD protection chip is higher than the maximum rated voltage of the light-emitting chip but lower than the maximum withstand voltage of the light-emitting chip 2. Under normal operating conditions, the ESD protection chip 3 is in the off state and does not affect the normal operation of the light-emitting chip 2; when an electrostatic pulse occurs in the circuit or the voltage exceeds the safety threshold, the ESD protection chip 3 quickly conducts to discharge electrostatic energy, preventing the light-emitting chip 2 from being electrostatically damaged, effectively improving the operational reliability and service life of the device.

[0026] The positive and negative electrodes on both sides of the bottom of the light-emitting chip 2 are electrically connected to the inner positive electrode pad 5 and inner negative electrode pad 6 on the top surface of the substrate 1, respectively, so that the light-emitting chip 2 and the ESD protection chip 3 form a vertically stacked layout. In this layout, the planar projections of the two types of chips overlap each other, and the ESD protection chip 3 does not occupy additional horizontal layout space of the substrate 1. The overall size of the device is determined only by the size of the light-emitting chip 2 and is independent of the size of the ESD protection chip 3. The shape of the LED can be compressed to be close to the size of the light-emitting chip 2, supporting display designs with smaller pixel pitch.

[0027] In this embodiment, both the light-emitting chip 2 and the ESD protection chip 3 adopt a flip-chip structure, with their electrodes located at the bottom of the chip. They are connected and fixed to the corresponding inner pads through a eutectic bonding process or a solder paste reflow curing process. When using the eutectic bonding process, the bottom electrode material of the light-emitting chip 2 and the ESD protection chip 3 is preferably a gold-tin alloy, and the surface material of the corresponding inner positive pad 5 and inner negative pad 6 is preferably nickel-gold. When using the solder paste reflow curing process, the bottom electrode material of the light-emitting chip 2 and the ESD protection chip 3 is preferably tin, and the surface material of the corresponding inner positive pad 5 and inner negative pad 6 is preferably tin. The eutectic bonding interface has high bonding strength and low contact resistance, which can improve the electrical stability of long-term operation; the solder paste reflow curing process is suitable for mass production line operations, resulting in higher assembly efficiency and more controllable material costs.

[0028] A light-transmitting layer 4 is disposed on the top of the substrate 1, covering the light-emitting chip 2 on the top surface of the substrate 1. The lower end of the light-transmitting layer 4 fills the groove 11 and covers the ESD protection chip 3. The overall size of the light-transmitting layer 4 is consistent with that of the substrate 1. The material of the light-transmitting layer 4 can be one or more of silicone and epoxy resin. Phosphor or dispersant can be added inside, and it is formed by dispensing curing or molding process. The light-transmitting layer 4 has high light transmittance, which can ensure the light emission efficiency of the light-emitting chip 2. Adding phosphor can realize wavelength conversion, and adding dispersant can homogenize the light emission angle, eliminate local bright spots, and improve the uniformity of the display image. At the same time, the structure of the light-transmitting layer 4 filling the groove 11 forms a complete cover for the ESD protection chip 3.

[0029] The substrate 1 has an outer positive pad 9 and an outer negative pad 10 on its bottom sides for interfacing with external display module circuits. Through-holes are formed on both sides of the substrate 1, with a positive connection portion 7 and a negative connection portion 8 respectively disposed within each through-hole. The two ends of the positive connection portion 7 are electrically connected to the outer positive pad 9 and the inner positive pad 5, respectively, while the two ends of the negative connection portion 8 are electrically connected to the outer negative pad 10 and the inner negative pad 6, respectively. In this embodiment, the positive connection portion 7 and the negative connection portion 8 adopt a copper conductive pillar structure, with the diameter of the copper conductive pillar matching the diameter of the through-hole and filling the interior of the through-hole. The copper conductive pillar has excellent conductivity and strong structural stability, enabling reliable vertical interconnection of the upper and lower pads of the substrate 1, while also possessing a certain heat dissipation capacity, helping to conduct heat from inside the device outwards, thus meeting the heat dissipation requirements of high-density packaging.

[0030] Compared to the solution of adding separate anti-static devices on the display module PCB, this embodiment integrates ESD protection into a single LED device. The display PCB does not need to reserve a separate mounting position and wiring path for the protection device for each pixel, which simplifies the PCB layout, saves available board space, increases the number of pixels per unit area, and reduces the assembly process and material costs of the module, thus adapting to the high-density and integrated development trend of small-pitch LED display technology.

[0031] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A small-pitch LED with ESD protection, characterized in that, The device includes a substrate, a light-emitting chip, an ESD protection chip, and a light-transmitting layer. The substrate has a groove in the middle, and inner positive and inner negative pads are respectively provided on both sides of the top surface of the substrate. Both the inner positive and inner negative pads have a stepped structure, and their adjacent sides extend to both sides of the bottom end of the groove. The ESD protection chip is placed in the groove, and the positive and negative electrodes on both sides of the bottom end of the ESD protection chip are electrically connected to the inner positive and inner negative pads on the bottom surface of the groove, respectively. The light-emitting chip is disposed on the substrate and covers the groove. The positive and negative electrodes on both sides of the bottom of the light-emitting chip are electrically connected to the inner positive and inner negative electrode pads on the top surface of the substrate, respectively, so that the light-emitting chip and the ESD protection chip are vertically stacked. The light-transmitting layer covers the light-emitting chip on the top surface of the substrate, and the lower end of the light-transmitting layer fills the groove and covers the ESD protection chip. The substrate has an outer positive electrode pad and an outer negative electrode pad on its bottom sides, and through holes are opened on both sides of the substrate. A positive electrode connection part and a negative electrode connection part are embedded in the two through holes, respectively. The two ends of the positive electrode connection part are electrically connected to the outer positive electrode pad and the inner positive electrode pad, respectively, and the two ends of the negative electrode connection part are electrically connected to the outer negative electrode pad and the inner negative electrode pad, respectively.

2. A small-pitch LED with ESD protection function according to claim 1, characterized in that, Both the light-emitting chip and the ESD protection chip are flip-chips, with their electrodes located at their bottom.

3. A small-pitch LED with ESD protection function according to claim 2, characterized in that, The bottom electrode material of the light-emitting chip and the ESD protection chip is one or more of gold, silver, and tin.

4. A small-pitch LED with ESD protection function according to claim 2, characterized in that, The light-emitting chip and the ESD protection chip are respectively connected and fixed to the inner positive electrode pad and the inner negative electrode pad through a eutectic process or a solder paste reflow curing process.

5. A small-pitch LED with ESD protection function according to claim 1, characterized in that, The height of the top surface of the ESD protection chip does not exceed the height of the top surface of the substrate.

6. A small-pitch LED with ESD protection function according to claim 1, characterized in that, The Zener voltage of the ESD protection chip is higher than the maximum rated voltage of the light-emitting chip, but lower than the maximum withstand voltage of the light-emitting chip.

7. A small-pitch LED with ESD protection function according to claim 1, characterized in that, The positive electrode connection and the negative electrode connection are copper conductive pillars, and the diameter of the copper conductive pillars is adapted to the diameter of the through hole.

8. A small-pitch LED with ESD protection function according to claim 1, characterized in that, The light-transmitting layer contains fluorescent powder or dispersant, and is formed by dispensing curing or mold top process.

9. A small-pitch LED with ESD protection function according to claim 8, characterized in that, The light-transmitting layer is the same size as the substrate.

10. A small-pitch LED with ESD protection function according to claim 8, characterized in that, The material of the light-transmitting layer is one or more of silicone and epoxy resin.

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