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Comparison of COB packaging technology and SMD packaging technology
Industry News 2019-3-16

With the rapid development of display technology, recently, COB packaging products have become a hot new favorite in the mid-to-high-end display market, and have become a trend of future display. What is COB? Let me introduce you in detail today:

LED display technology

At present, there are two main packaging technology forms for full-color small pitch LED display screens, one is SMD surface mount component technology, and the other is the COB integrated packaging technology. Surface-mount components were introduced about twenty years ago, from passive components to active components and integrated circuits, and eventually became surface-mount devices (SMD) and can be assembled by pick and place equipment. COB is a brand-new packaging technology that has only been widely used in full-color LED screens in recent years.

SMD packaging technology

SMD: It is the abbreviation of Surface Mounted Devices, meaning: surface mount device, it is one of SMT (Surface Mount Technology) components. At present, indoor full-color LED screens mainly use surface-mount three-in-one SMD, which refers to the packaging technology of encapsulating SMT lamps with three different colors of RGB LED chips in the same gel at a certain interval to form a display module.

The main process is to encapsulate the LED light-emitting chip in the bracket to form a lamp bead (SMD surface mount), and the lamp bead is pasted on the PCB board through solder. Then put the surface mount and PCB board in a high-temperature oven for sintering and solidification (reflow soldering), then solder the LED by pressure welding technology, and finally use epoxy resin to dispense the bracket to form the display module. The modules are then spliced into units.



The core material of SMD process:

Bracket: Conduction, support and heat dissipation are mostly formed by the plating of the bracket material, which is composed of five layers of material, copper, nickel, copper and silver from the inside to the outside.

LED chip: The chip is the main component of LED Lamp, which is a light-emitting semiconductor material.

Conductive wire: connect the chip PAD (pad) to the bracket and make it conductive.

Epoxy resin: protects the internal structure of the lamp beads, and can slightly change the luminous color, brightness and angle of the lamp beads;

COB packaging technology

COB: It is the abbreviation of Chip On Board. Means: Chip-on-board packaging technology; a semiconductor packaging process in which the chip is adhered to the interconnect substrate with conductive or non-conductive adhesive, and then wire-bonded to realize its electrical connection. Simply put, the light-emitting chip is directly mounted on the PCB board, without the need for brackets and solder legs. Compared with the traditional SMD approach, COB packaging omits the two major processes of making LED chips into lamp beads and reflow soldering. The chip is directly assembled to the PCB. Basically, there is no limitation on the size of the packaged device, and a smaller dot pitch arrangement can be achieved. At present, Micro LEDs all use COB technology.


The process of COB technology is much simplified compared to other packaging technology steps, relatively simple, as shown below:


Features of LED video wall screen of COB packaging technology:

1. Super "stability": almost no faults, no dead spots.

2. No "glare": adopt surface light sources instead of "glare" point light sources and other environmental protection technologies. The brightness is soft and protects the human eye.

3. No "delicateness": don't be afraid of bumps, you can wipe with water, protection grade IP66.

4. No "splicing": it can "customize" precision display screens of different sizes.

5. "Long life": 24 hours and 365 days of continuous use for more than 8 years (theoretical 10 years).

6. "It is the future": It will replace DLP, LCD, plasma, projection, movie screen, SMD LED display and other display products.


In the future, the mainstream display technology, micro-pitch Micro-LED, in theory, the micro-pitch can be infinitely small. It is a micro-pitch display technology based on COB packaging.


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