When we step into the field of LED PCB, some basic definition is frequently used but hard for green hand to distinguish. The text will introduce what is LED, LED Chip, COB LED Chip. A direct comparison and pictures are added at the end of the text for easy identification.
What is LED?
The full name of LED is Light Emitting Diode. After introducing its full name, I believe it will be easy for you to tell what is LED. It is a two-way diode that lights by current going through. It is widely used as an indicator light for radio recorders and other electronic equipment.
What is LED chip?
Though it sounds not different between the name “LED” and “LED chip”, their light resources are totally different. LED is lighted by the diode, while LED chip is lighted by the semiconductor.
The core semiconductor is attached to the substrate whose two ends is the positive electrode and negative electrode respectively. The whole chip is coated with epoxy resin.
The P-N conjunction, made of mono-crystalline silicon, is a fundamental part of an LED chip. As its name, it is made up of a P-shape semi-conductor and an N-shape semi-conductor. P-shape semiconductor is empty chamber, while the N-shape semiconductor is filled with electron. When current go es through this P-N conjunction, the electron in N chamber was pushed to P chamber, triggering to recombination and then lighting in the form of photon.
When it comes to the package of LED Chip, it greatly differs electronic chip since protection and light transmitting are both important consideration. There are mainly three package types for LED Chip, including SMD SMT, DIP and COB.
SMD(Surface Mount Device) is about mounting chip on the surface of the board, while DIP( Dual In-line Package) is about inserting the chip through PCB. Differing from the above traditional package methods, COB, a modern package technology, focus on soldering a group of LED chip on the board. It enjoys great popularity in the market so we are going take a close look at it.
What is COB LED chip?
COB LED Chip is also named chip on board. It could be in the shape of strip, tetragonum and circle.
The construction of COB LED chip is not so difficult to understand. The wafer placement point on the substrate surface of COB LED is covered by thermal conductive epoxy resin doped with silver particles. Then the wafer is directly placed on the substrate surface. Heat treatment should be applied until the wafer is firmly fixed on the substrate. Finally, the electrical connection is directly established between the silicon wafer and the substrate by wire welding technology.
MCOB(Multiple Chips on Board) is another variants. It means multiple chips are generally integrated in LED bulbs or LED tubes.
MCCOB(Multiple Chips and Cups on Board)is a packaging approach that places the chip directly inside an optical cup. You can also make multiple cups at the same time. It’s based on a simple principle. To let more light energy run out according to reflection principle, you need to design a lot of corners in the cup since LED chip light is concentrated at the bottom of the cup. In this way, the light utilization rate increase a lot. They can be applied for high bay and floodlights.
What is the Benefit of COB LED Chip?
For applications to LED board, COB chips are cheaper and more convenient. First, it’s electrically stable. The circuit design, optical design and heat dissipation design are scientific and reasonable. Second, it carries good heat sink process technology to ensure the thermal lumen retention rate of LED. Third, it improves the quality of lighting. It has the characteristics of high color rendering, uniform luminescence, no spot, health and environmental protection. Fourth, it is Reduce the difficulty of lamp board design and subsequent maintenance costs.
Differences Between LED And COB LED Chip
- They have different definitions and uses. LED refers to a surface-mounted light-emitting diode with a large luminous Angle. Compared with the early plug-in package, it has the advantages of high efficiency, good precision, low welding rate, light weight and small volume. It often used In indicator light of device. In contrast, COB chip refers thatchip is directly bound on the entire substrate. It is a good solution for low-power chip to realize high-power LED lights. It can disperse the heat dissipation of the chip, improve the light efficiency, and improve the glare effect of LED lights. COB has high luminous flux density, less glare and soft light, and emits a uniform distribution of light. Therefore, it is also commonly used in the lamp with eye protection function.
- Their light emitting principle is LED is based on diode, while COB is the LED chip directly affixed to the substrate. This technology needs no plating, no reflow, no patch process, so the labor and cost is saved a lot.