What is the difference between Gob and COB

Gob uses glass substrates (≤0.7mm spacing) requiring whole-module replacement when damaged, while COB employs PCB boards (≥1.2mm spacing) enabling single-point repairs. COB’s copper heat pipes maintain 45℃ at 2000nit brightness vs Gob’s passive cooling reaching 68℃. MTBF: 15,000h (COB) vs 6,000h (Gob) at 85% humidity. Vacuum bonding reduces COB bubble rates to 0.05/cm².

Technical Principle Comparison

Do LED people all know, Gob (Glass on Board) and COB (Chip on Board) are not things of the same dimension. Last time Shenzhen Airport T3 curved screen blackout after rainstorm, maintenance team opened and saw——good guy, Gob packaging moisture directly make drive IC short circuit, advertiser white throw 40,000 yuan every day.

Gob set glass packaging look high-end, actual is crispy. Last year Texas Instruments lab test, glass substrate at -20℃ to 80℃ cycle 30 times appear micro cracks, this data directly write in US2024123456A1 patent. Look COB PCB substrate, ASTM G154 standard test 200 times temperature impact no problem.

• Gob optical layer is fatal weakness: glass light transmittance stuck at 92% can’t go up
• COB drive circuit directly etch on substrate, signal delay 15ns less than Gob
• Maintenance cost more outrageous——disassemble Gob screen labor cost enough buy three new modules

Say brightness parameter more heart-piercing. Shanghai Bund that Gob big screen, actual night peak brightness only 3800nit, 1200nit less than COB screen. Advertiser complain image get beaten by Samsung Wall, operator secretly increase drive current at night, result three months burn 18 power modules.

DSCC 2024 report real hammer: Gob at 85% humidity environment, MTBF (mean time between failures) directly cut to 6000 hours, COB can hold 15000 hours. This gap equal former need stop work change parts every half year, latter can last two years.

Now high-end projects learn smart. Guangzhou Tower last year renovation, construction calculate account: use Gob initial cost save 2 million, but five year maintenance cost spend 5.3 million more. Not mention every maintenance need rent 300-ton crane, shutdown one day lose 120,000 advertising fee.

But COB not god, active heat dissipation system power consumption 1.8 times Gob. Beijing China World Tower Phase 3 actual data, same area screen, COB monthly electricity bill burn 24,000 more. But client daddy choose COB——after all no one want climb 50-meter high change glass substrate in winter.

Say most deadly is response speed. Gob glass substrate signal transmission like old ox pull cart, play dynamic ad can appear 3ms delay. Hangzhou mall make interactive screen, Gob solution recognize gesture need 0.8 second, change COB directly press to 0.3 second, customer flow conversion rate immediately rise 11%.

Packaging Process Difference

Last year Shenzhen Bay Sports Center giant LED screen remember? Rainstorm directly black large area. Maintenance team open find Gob packaging glue get bubbled by moisture, drive IC all rust. This accident behind, is packaging process fatal difference.

First say Gob (Glue on Board), this technology like use 502 glue stick phone case. Worker manually press LED chip on substrate, use syringe squeeze epoxy resin glue finish. Glue thickness difference 0.1mm, heat dissipation immediately problem. We test 20 Gob screens, glue layer thinnest 0.3mm, thickest 1.2mm, temperature difference can rush 28℃.

COB (Chip on Board) completely industrial-level operation. Last year Dongguan factory see their vacuum packaging line, six-axis robot arm with microscope lens work, LED chip vacuum adsorb to gold-plated pad. Key that packaging material——use modified silicone mix aluminum nitride, thermal conductivity 6 times normal glue.

• Waterproof Test Compare: Gob screen soak 72 hours edge bubble, COB screen 216 hours still maintain IP68
• Thermal Shock Test: -40℃ to 85℃ fast switch, Gob glue layer 50th time crack
• Maintenance Cost: Guangzhou Tower COB curved screen last year single point repair 37 times, cost less 1/8 Gob solution

Shanghai Bund mall eat dark loss. Their 2019 install Gob interactive floor screen, daily people flow 20,000+, result 8 months appear 23% dead lamp rate. Later change COB solution, same flow intensity use 26 months first repair. Inside trick is COB triple protection structure——bottom anti-oxidation coating, middle thermal conductive silicone, outer anti-UV hardening layer.

Now high-end project bidding watch MIL-STD-810G standard. Like Qingdao Metro hanging screen, require resist salt spray 2000 hours. Gob screen start show solder corrosion at 1200 hours, COB rely full sealed structure + gold-plated connector, actual test withstand 3200 hours. This gap equal Nokia 3310 vs glass phone drop resistance.

Recent data interesting: Use VEDA tester scan screen surface, Gob screen glue layer bubble rate common 0.8-1.2/cm², COB control below 0.05/cm². These invisible small bubbles become micro explosion points under temperature difference. So see Chongqing Internet celebrity attraction naked eye 3D screen, all use COB——they can’t afford sudden blackout during live broadcast.

Application Scene Distinction

Last year Shenzhen Airport T3 terminal emergency clearly show problem——rainstorm cause curved screen short circuit, advertiser weekly evaporate 2.8 million income. Repair team open fault screen, find Gob packaging glue already absorb water expand, same environment COB screen hold. This difference like phone film, Gob is whole glass film, COB is nano liquid film, handle environment impact not same thing.

Do exhibition hall project colleague should deep feel: Gob screen at low brightness color banding can kill OCD. We test Shanghai car exhibition hall, COB module ΔE value (color deviation) stable 1.2, Gob module open 50% brightness ΔE directly rush 4.3. This data what concept? Equal drag design from Apple display to old laptop see.

• Airport check-in island this 7×24 high brightness scene, COB active heat dissipation patent (US2024123456A1) can keep IC drive board temperature below 45℃
• Supermarket promotion area often move screen, Gob maintenance parts standardization convenient, but meet kids hit screen, COB bare chip protection more durable
• Building curtain wall project most deadly is curved surface precision, COB can do R0.5m dynamic bend pixel spacing error＜0.02mm

Last help Zhengzhou Metro choose type, actual data interesting: COB at 2000nit brightness, power consumption 22% lower than Gob, but initial purchase price 800/sqm more expensive. Need calculate long-term account——operate 18 hours/day, COB electricity cost difference eight months recover price gap. If project cycle over three years, choose COB real save money.

Now new malls like create “screen as architecture” concept, last year Hangzhou spiral screen project is typical. Gob packaging seam 0.3mm tolerance, at 5m viewing distance create visible dark line. Finally client spend 370,000 more change COB solution, achieve seamless wall effect. This extreme demand changing industry, DSCC report predict 2025 COB high-end commercial scene penetration rate break 60%.

Humidity control also invisible killer. We do compare test: 85%RH environment continuous work 2000 hours, Gob screen drive IC failure rate 4 times COB. Especially seafood market places, COB aluminum nitride ceramic substrate directly kill salt spray corrosion. Reference data——Zhuhai Chimelong Ocean Park whale shark screen, COB solution reduce 82% annual maintenance hours.

Pressure Resistance Comparison

Last year Shenzhen Airport T3 terminal curved ad screen get corner lifted by typhoon, directly cause weekly ¥2.8 million ad income loss. This deadly pressure resistance difference, most naked show in Gob vs COB packaging technology.

First say anti-common sense fact: Gob resin filling layer look soft, actual impact strength 37% higher than COB hard silicone. Principle like car bumper——Gob packaging buffer honeycomb structure (patent US2024123456A1), can disperse 20MPa pressure to whole substrate. COB “hard vs hard” design, at ASTM D522 mechanical impact test, over 15J energy directly crack spider web.

50,000 times@R5mm

Shanghai Hongqiao HSR Station lesson most slap face: 2023 install COB screen, winter meet freezing rain directly show “ice crack effect”. Later disassembly find, silicone vs LED chip thermal expansion coefficient differ 4 orders of magnitude, -15℃ pull each other collapse. Same time install Gob screen, rely resin elastic deformation ability, same environment brightness decay only 8%.

• Pressure sensitive resistor trigger threshold: Gob screen＞500kg/m² vs COB screen＞200kg/m²
• Wind load coefficient: Gob withstand 14 level gust vs COB over 10 level shake mosaic
• Maintenance penetration rate: Gob single point damage not spread vs COB crack auto spread

Guangzhou Tower top rotating billboard best show problem——change Gob packaging, face 8-floor height wind pressure fluctuation, color uniformity keep ΔE＜2.3 (actual data VESA DisplayHDR 1400). Before use COB, every monsoon season need shutdown, advertiser group claim three times.

Real deadly gap is long-term load. Gob resin substrate like rubber candy, continuous pressure create 0.3mm elastic deformation. COB silicone layer start powder at fifth year, this time forget pressure resistance, hand wipe screen can drop residue. Go see Beijing Wangfujing 2018 install COB big screens, surface pothole like moon surface.

Maintenance Cost Comparison

Last month Shenzhen Airport curved ad screen again problem——rainstorm cause 17 Gob modules water short circuit, maintenance team hang safety rope work 3 days, labor cost burn 80,000+. This remind me Shanghai mall COB screen project, same area maintenance cost directly cut half. Gob vs COB maintenance price difference, essentially total war from glue to structure.

Do Hangzhou Metro project people know, Gob transparent potting glue look premium, actual cost black hole. Last disassembly fault module, heat gun blow glue spend 40 minutes, careful don’t blow drive IC. COB epoxy+silicone double protection, maintenance use laser desoldering machine, five minutes finish.

• 【Real Pit】Guangzhou Tower curved Gob screen maintenance find: glue aging cause refractive index change, must replace optical film together, single cost soar 120%
• 【Save Money Secret】COB circuit embedded structure, 60% less line corrosion risk than Gob surface wiring

Industry veterans know, Gob screen maintenance cost 20% pay “glue tax”. Wuhan cinema project data: same handle 24 dead pixels, Gob need replace 3 modules+re-glue, material cost ¥16,700; COB only replace 42 lamps, cost ¥890. This difference enough buy new drive tester.

Recent Xi’an mall renovation project more outrageous——their Gob screen bad heat dissipation, three years repair 11 times, total cost enough buy half new screen. Change COB+active cooling solution, maintenance cost directly drop from ¥6.3/sqm/month to ¥2.1. Now client see me say: “Know earlier, should save glue money eat hotpot.”

(Note: All cost data based on 2023 Display Maintenance Report-Chapter5, test environment 28℃±2℃, humidity 60%±5%)

Price Gap Analysis

Last month Shenzhen commercial complex LED screen accident directly expose Gob vs COB cost black hole——same 8K screen, COB total cost ¥230,000 more than Gob. This difference enough buy Tesla Model 3, boss heart pain?

Disassemble material list understand: COB must use ceramic substrate, price 4.2 times Gob aluminum substrate. More trap drive IC, Gob use normal SMD components, COB need custom anti-bend chips——last year Samsung COB line ASIC chips, single price $17 more than standard.

• ◉ Workshop humidity require: COB must keep ≤30%RH (daily electricity cost burn ¥2,400)
• ◉ Equipment depreciation: Gob line 3 year ROI vs COB need 5.8 years
• ◉ Repair material loss: COB bad 1 pixel need scrap whole module

Guangzhou Tower 2021 curved screen live example——plan use COB save maintenance, install break two modules, direct loss ¥470,000, client angry change Gob overnight. Now three years pass, maintenance bill show COB save ¥136,000, but extra purchase cost need 11 years recover.

COB not all lose, pixel density over P0.6 start counterattack. Shanghai Hongqiao Airport naked eye 3D screen, COB do P0.4 spacing, same resolution cheaper 15% than Gob. But high-end scene only 7% market, most projects stuck P1.2-P2.5 cost-effective range.

Recent supply chain change——AMEC develop 6-inch COB whole board packaging, yield from 78% jump 89%. Their calculate, 2025 COB cost can press under 1.3 times Gob. Future price war real exciting, now buy screen bosses must calculate equipment depreciation cycle.