Technical Difference of GOB, SMD and COB
A. SMD Technology
LED products encapsulated by SMD technology is led display units with different pixel pitch, that mount led lamps by high speed SMT machine and solder by high temperature reflow soldering machine, their led lamps are encapsulated lamp cup, bracket, chips, wires and epoxy resin together and made as different specifications. Normally, small pixel pitch led display are made by naked led lamps or led lamps with plastic masks. Because of mature and stable technology, low production cost, good heat dissipation and easy maintenance, small pixel pitch SMD led displays have big market share. However, due to its serious defect, it cannot meet market requirements gradually .
1. Low Protection Level: do not have the function of moisture proof, waterproof, dustproof, anti-impact and collision, anti-static, antioxidation, good lamp heat dissipation, anti-blue radiation, anti-UV etc., Due to led lamps of SMD products do not adhere with PCB board seamlessly, stress would easily concentrate on one single lamp when collision occurred. As it is known, LED displays cannot avoid impaction and shaking during shipping and installation, however, these factors are all very easy to hurt led lamps. In other hand, SMD led displays are easily to have large batch of blind lamps when work in damp environment; especially small pixel pitch led displays, besides moisture proof, it still has other big protection problems, such as waterproof, dustproof, anti-static, antioxidation etc.,
2. Heat Dissipation: Heat dissipation is the key point of led display’s stability and reliability. Heat conduction during led display working is very important indicator for quality inspection, the smaller pixel pitch SMD led display is, the smaller led chips with high consumption used. However, traditional SMD led displays adhere with PCB boards via SMT technology, there should be a gap between led lamps and PCBs, it would cause disfunction of heat conduction during LED lamps working.
3. Harmful for eyes: Eyes would feel dazzling and tired after long time watching at SMD led displays, eyes could not be protected well. In addition, SMD led display has blue ray, as LED blue light wave length is short and frequency is high, people directly watch led displays in a long time period, retinopathy would be caused by blue ray easily.
4. Short LED lamps life time: LED lamp life time would be hardly shortened because of working environment; at the same time. PCB board would occur copper ion migration, then cause micro short circuit.
5. Mask: Working in high temperature, masks of small pixel pitch led displays would muster very easy, it is harmful for display effect. Also, after used for a period, masks can not be cleaned, and color would have very big change, both outlook and display effect would become very bad.
B、COB（ Chips on Board) Technology
COB is named chip encapsulation on board; it was aimed at solving problem of led display heat dissipation. Compared with DIP and SMD, COB technology saves space, simplifies encapsulation job, has efficient thermal management method. It is adopting conductive or non-conductive glue to mount naked led chips on PCB board, then doing wire bonding to achieve electric connection. In case naked led chips are exposed in the air, they would be to polluted or artificially damaged very easy, then led chips would lose functions. That is why encapsulate led chips and bonded wire with glue. This encapsulation method is also called soft encapsulation. Its advantages are in production efficiency, low thermal resistance, light quality, application and production cost. However, as new technology, COB does not have enough experience, detailed technique need be improved, main products in market has a disadvantage in cost, and some other problems too. For example:
1. Low consistency: As no lamp selection operation, COB led display cannot do light separation; it causes problem of low consistency
2. Serious Modularity: Whole COB led displays are assembled by many small units; that is the reason COB led display has disadvantage of different surface color and serious modularity.
3. Bad surface flatness: As encapsulating led lamps one by one, display surface flatness is bad, and has obvious granular sense.
4. Difficult maintenance: Need professional equipment to do maintenance, not easy to do and cost is high; normally products need be sent back to factory to do maintenance.
5. High production cost: Defective rate is high during production; production cost is much higher than SMD small pixel pitch led display.
C、GOB（ Glue On Board） Technology
By filling High factor optics thermal conduction Nano glue on product surface, led lamps and PCB broad are highly bonded together; so that a hard protection cover is formed, then great ultra-protective performance is achieved. As LED display surface is covered by high factor optics thermal conduction Nano glue, led lamps are no naked foot, screen surface is smooth and no gap; led lamps are isolated from outside, display avoids all damages from outside probably, so that led displays have much better protection performance. GOB technology makes led display pixel failure rate improved from current industrial standard 100~300PPM to 2~5PPM, this improvement could be a revolutionary leap in led display industry.
GOB technology achieves the transformation of led display from point light source to surface light source; illumination is much more uniform, display effect becomes clearer, viewing angle is highly improved (both vertical and horizontal viewing angle are very close to 180 degrees), moiré has been mostly reduced. Matte effect of GOB led displays highly improves their contrast, reduces glare and visual fatigue, and effectively protects audience’s safety and healthy.
GOB LED display products which did surface optical processing have flatter screen surface, and there is no glitch on each section after it was processed by high precision equipment; what’s more, splicing accuracy of led display can reach ≤0.02mm.
GOB technology adopts material with high thermal conduction function and does full packing for led displays. It probably fills gaps in SMD led displays, makes working led lamps can have efficient heat dissipation. Because of this, led display gets a whole screen area for heat dissipation. This technique is beneficial to longer service life and higher stability of led displays.
GOB led display product is easy to do maintenance, and low maintenance cost, low defective rate; production cost is much lower than COB led display. Also, GOB technology resolved problems that COB technology can not do, such as cannot mix led lamps and do light separation, serious modularity, bad flatness and so on.
