Three Led Packages: Smd, Cob, Imd Difference

1. LED packaging process enters a new cycle

The surface treatment process of the package is different, and there is a difference in light color between pixels, which easily leads to inconsistent light mixing and high difficulty in correction, which in turn affects the display effect. Since the development of the LED display (mainly small pitch) industry, in addition to the traditional in-line process, a variety of packaging processes including SMD, COB, and IMD have been formed.

2. Mini/Micro LED is gaining momentum

LEDs can be used as LCD backlights for large-size displays, smart phones, automotive panels, notebooks, and other products, as well as RGB three-color LED chips to achieve self-luminous display; Micro LEDs have extremely small pitch, high contrast and high refresh rate. , suitable for smart wearable devices for close-up viewing such as smart watches, AR, and VR. The application of Mini LED backlight has entered the stage of mass production. In the future, the solution of mass transfer technology will definitely promote the commercialization process of MicroLED, and MicroLED is ready to go.

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1 Small-pitch market mainstream packaging-SMD process

SMD is the abbreviation of Surface Mounted Devices. The LED packaging factory using the SMD process fixes the bare chip on the bracket, electrically connects the two with gold wires, and finally protects it with epoxy resin. The lamp beads after SMD packaging are handed over to the display manufacturer, and the solder joints are connected to the PCB through reflow soldering, and a module is formed for assembly. Small-pitch products in SMD package generally expose the LED lamp beads, or use a mask. SMD uses surface mount technology (SMT), which has a relatively high degree of automation, and has the advantages of small size, large scattering angle, good luminous uniformity, and high reliability.

2 Effectively solve high-density packaging-COB process

COB stands for Chip on Board. Unlike SMD, which solders the lamp beads to the PCB, the COB process first covers the placement point of the silicon chip with thermally conductive epoxy resin (silver-doped epoxy resin) on the surface of the substrate, and then uses adhesive or solder to connect the LED chip with conductive or The non-conductive glue is adhered to the interconnect substrate, and finally the electrical interconnection between the chip and the PCB board is realized by wire (gold wire) bonding. The LED crystal element is fixed on the front surface of the display substrate, and the film is pasted on the front surface of the display substrate. The LED crystal element is an ordinary red, green, and blue LED light-emitting chip to realize integrated packaging.

3 Combination of economy and technology - IMD process

At present, the surface mount process is still used in the IMD process, which combines the advantages of SMD and COB. From the perspective of pixel structure, the traditional SMD package is basically a pixel; COB package is to directly package the LED chip on the module substrate, and then mold each large unit as a whole. One package structure has hundreds or thousands of pixels. ; And IMD "four-in-one" means that there are four basic pixel structures in one package structure, which is still essentially four "lamp beads" synthesized by 12 RGB-LED chips. "Four-in-one" LED modules use formal chips. As packaging manufacturers make more requirements for chips, "six-in-one" and even "N-in-one" solutions may be introduced later.

COB and IMD technologies have their own advantages. Although COB has a high packaging cost, it reduces the traditional die-bonding process, reduces the weight, and can be developed in the direction of thinning. However, to enter the COB field, it is necessary to re-purchase equipment, production lines, etc., requiring companies to have deep financial strength. The IMD technology can continue to use SMD's equipment, production lines and personnel experience.

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