What Is Chip on Board LED?
What is cob?
Chip on board can heat dissipation when embed on substrate of high powered LED die. This cob technology is able to connect unpackaged circuit board to ceramic PCB , realizing a highly miniaturized design for manufacturing and assembly. It has become commonly in MCM application. Typically, the absence of first-level packaging reduces process complexity and supports more compact integration. Compared with surface-mount and through-hole designs, chip-on-board (COB) packaging technology makes more efficient use of circuit board area, enabling shorter interconnections, higher operating speeds, and smaller package sizes. cob led technology show remarkable merits lumen output, thermal control, and luminary integration. By using these advantages, building contribution for general lighting, architecture market, design and emergency lighting and son on. With the time passing by, led cob led more flexible in products variation and functions. Which covered a wide range of industries like automotive LED lights, medical sensors, visible light communication.
What Is chip on board led?
Led on chip is a method to attach a silicon due on substrate material without any treatment like package and flip, afterwards, the complete assembly is encapsulated using epoxy glob-top resin, followed by curing to create a protective barrier. However, different from traditional technology that packaging as a whole set, connecting directly between microchip or die and circuit board.
COB LED structure
The circuit board led lights with an aluminum substrate via a thermal interface material such as red adhesive. To reduce influence of thermal stress, adding a silicon intermediate layer can alleviate CTE mismatch issue. it also enables a more compact interconnection scheme without external leads. Standard red adhesive is retained for bonding, and Al or Cu wires are used for electrical connection. In addition, aluminum or copper wire provide electrical connections. Two adjacent chips use a common die pad to enhance integration density. A silica gel lens is employed for both optical focusing and encapsulation protection. These structure promote led chip series with multiple merits include long life time span, eco- friendly, response speed, low power consumption, so widely accept by the public.
How COB LED Technology Works
Direct Chip Mounting Process
A vision-based robotic system was used for automated COB LED chip mounting on PCB substrates. The LED on chip was detected and tracked on a conveyor using dual cameras and controlled lighting[2]. After localization, the chip was picked up by a vacuum gripper and transferred to the assembly position. A six-axis robotic arm simultaneously positioned the PCB beneath the chip. Visual feedback was then applied to align the LED pins with the ceramic PCB holes through three-dimensional adjustment. After successful insertion, the assembled ceramic PCB was moved to the output tray. The chip mounting process can be divided into two steps, chip localization on the conveyor and subsequent alignment of the LED pins with the PCB holes.
Importance of Thermal Management in chip on board led
Thermal management is a key factor for LED lighting system. Since the working temperature during process increased, the light output declines more quickly, which consequently reduces the useful lifetime of the device. Most of the thermal energy generated by high power LEDs is removed through backside heat conduction, transferred by heat dissipation to the air through convection and radiation at the heat sink. Therefore, the back side of led cob light should equipped with excellent ability of heat dissipation. The tolerance of LED chip is 130–140 ℃, Consequently, optimized thermal dissipation is critical to making energy efficient led light bulbs and improving device reliability.With increase of surface area of heat sink, the junction temperature of high-power LED decreases linearly, accompanied by a similar decrease in thermal resistance[1]. The heat sink thickness can reduce LED temperature junction. LED junction temperature depends on the package material and heat flow path, whereas heat dissipation efficiency is determined by material geometry and thermal conductivity.
Ceramic Substrate in COB LED
There are no thermal vias and bottom copper layer on ceramic PCB. Which can tolerance high resistance and electricity to the revise side of the ceramic substrate. Heat is distributed more uniformly and is no longer restricted to localized metallic spreading regions[4]. Ceramic substrates such as alumina substrate and AlN substrate provide good electrical insulation and relatively uniform heat spreading, but their moderate thermal conductivity limits heat extraction in high-power applications. The thermal expansion ratio of al2o3 is 235Wm-1K-1. To improved thermal performance, LEDs are mounted directly on the metal substrate without a dielectric layer. The thermal test evaluated a 60-die LED module directly bonded to a metal substrate without a dielectric layer. Operating at a total power of 24 W resulted in only a 14.2 °C increase in junction temperature, indicating efficient heat dissipation. Structure function analysis further revealed a very low junction-to-case thermal resistance of 0.165 K/W. The results demonstrate that direct metallic bonding significantly improves thermal performance, making the external heat sink the primary factor affecting the final junction temperature. For applications mainly requiring even temperature distribution rather than extremely high thermal conductivity, Al₂O₃ ceramic substrates are suitable. Where metal substrates are more suitable for high-power COB LEDs.
COB LED vs SMD LED
Electrical Connections and Power Supply
SMT circuit board typically use die-attach epoxy to secure semiconductor die, such as LEDs and ICs, onto SMD packages. Afterwards, pins of SMD package are bonded on the substrate. Therefore, thermal dissipated by the devices is conducted to the PCB through the epoxy layer, package structure, and pins. By contrast, cob led lights produce heat via led sink link to the substrate directly from the semiconductor dies to the PCB via the epoxy layer. Chip on board Led combine various LED chips together, rather than place LED lights on the surface. Which is conductive to COB light, making them lighter than SMD bulbs[3]. However, led power supply produce brighter cob lighting, while SMD LEDs support color variation.
Applications of COB LEDs
COB technology is widely used in led headlights because it provides high brightness, low energy consumption, and longer lifespan. It also improves visibility and driving safety, especially in low light and poor weather condition. Laser lighting technology used in automotive headlights. High beans are suit for long distance road. Whereas low beam are used to improve visibility in the vehicles
Commercial and Industrial Lighting
Lighting consumes about one-third of electricity in commercial buildings and more than half in retail and lodging environments. Large and complex industrial facilities often require different lighting conditions across various operational areas. In commercial spaces, cob lighting offers uniform illumination and energy efficiency. Many businesses choose led lamp led lamp, led light bulbs, and led light bulb products for warehouses, offices, and factories.
LED Strip Lighting
Modern led strip lights use COB technology for smoother and brighter lighting effects. led strip leds, led strip light lights, and chip on board led strip products are popular in decorative and architectural lighting. It consists of multiple diodes. As the result of same performance, which can be regarded as a linear light source. Every single LED strips are divided into sections, connecting in series[5]. This system operates on a low-voltage DC supply and driven by a 12 V or 24 V low-voltage DC source.