Recently, National Star Optoelectronics stated that its Mini LED chips have been mass-produced, and the company will implement expansion plans based on market conditions. National Star Optoelectronics actively cooperates with well-known international display manufacturers, and has become the first certified supplier of an international manufacturer to enter the Mini LED ultra-high-definition display field.
Mini LED refers to LEDs with a size of 50-200μm, also known as sub-millimeter light-emitting diodes. Mini LED is the main force in the development of LED technology in recent years, and is widely used in backlighting, VR screens, small display screens of mobile phones and other fields. However, due to its small light-emitting angle, it is difficult to apply to larger screens.
For this reason, National Star Optoelectronics applied for an invention patent entitled "Large luminous angle flip-chip Mini-LED chip and its preparation method" on May 15, 2020 (application number: 202010413988.X), the applicant is Foshan City National Star Semiconductor Technology Co., Ltd.
The picture is a schematic diagram of the structure of a flip-chip Mini-LED chip with a large light-emitting angle, including a flip-chip LED chip body 1 and a refraction layer 2. Among them, the flip-chip LED chip body 1 further includes a substrate 11 and a light-emitting structure. The light-emitting structure is located on the front surface of the substrate 11 and the refractive layer 2 is located on the back surface of the substrate 11. The refraction layer 2 is composed of a plurality of prism frustums 21 and/or a plurality of frustum frustums 22, and the bottom surfaces of the prism frustum 21 and the frustum frustum 22 are connected to the substrate 11. After the light generated by the light emitting structure is emitted from the substrate 11, it is emitted through the side surface and the top surface of the prism 21/frustum 22. This prism/frustum structure makes the light originally emitted from the flat back surface of the substrate to be emitted from the side and top surface of the prism/frustum, effectively widening the light-emitting angle of the Mini-LED chip.
Take the refractive layer 2 consisting of a plurality of prisms 21 as an example. The ridge 21 is formed by a dry etching process or a wet etching process, and the plurality of ridges 21 are evenly spaced apart, and the distance between adjacent ridges is 0.5-2 μm. The shape of the pyramid 21 is generally a quadrangular pyramid or a hexagonal pyramid, and its shape is related to the material of the substrate 11 and the etching process. When a sapphire substrate is used, a hexagonal pyramid is formed after wet etching; when a silicon lining is used At the bottom, after wet etching, a quadrangular pyramid is formed. Hexagonal prisms are generally preferred. The number of sides of such prisms is large, which helps to broaden the light-emitting angle of Mini-LEDs.
When the width of the ridge 21 is greater than 10 μm, the number of ridges is small, and the light emitting angle cannot be effectively increased; when the width is less than 3 μm, the etching process is difficult. Therefore, the width of the ridge 21 is generally 3 to 10 μm, preferably 5 to 8 μm. Among them, when the number of edges on the bottom surface of the edge platform 21 is less than or equal to 4, the width of the edge platform 21 is the width of the longest side; when the number of edges on the bottom surface is more than or equal to 5, the width is the width of the line segment between the two endpoints farthest away. . When the height of the prism 21 is greater than 2μm, the bottom angle of the prism 21 is too large to effectively increase the light emitting angle. When the height is less than 0.5μm, the bottom angle of the prism is too small, and the light is totally reflected because it cannot be refracted through the side of the prism. , That is, it cannot play the role of increasing the light-emitting angle, so the height of the prism 21 is 0.5～2μm
In order to further increase the light-emitting angle of the flip-chip Mini-LED chip, a shielding layer is also provided above the refractive layer 2. The shielding layer is located on the top surface of the prism 21/frustum 22, which can effectively prevent light from being emitted from the top surface of the prism 21 and/or the frustum 22, and ensure that the light is only emitted from the side of the prism 21 and/or the frustum 22, Effectively improve the light-emitting angle of Mini-LED chips.
In short, the Mini-LED chip patent of National Star Optoelectronics, through the prism structure design, can effectively increase the light-emitting angle of the Mini-LED, which makes the Mini-LED widely used on large-format screens.
