Led package sizes include pin-type (direct insertion), SMD, chip on board direct assembly (COB) and other packaging dimensions, and its technology has gradually matured. Following are three kinds of LED packaging dimensions.
(1) Lamp LED package
LED pin-type packaging uses lead frame as the pin of various packaging exterior, which is the first packaging structure successfully developed and put into the market. Commonly used 3-10mm packaging structure, generally used for low current (5-20mA), low power (less than 0.1W) LED packaging.
(2) SMD LED package
SMD LED is the packaging structure with the highest market share of LED at present. The LED packaging structure wraps the metal lead frame in PPA plastic by injection moulding process and forms a reflecting cup with a specific shape. The metal lead frame extends from the bottom of the reflector cup to the side of the device, forming the device pin by flattening outward or bending inward. The improved SMD LED structure is accompanied by white LED lighting technology. In order to increase the use power of a single LED device to improve the brightness of the device, engineers began to find ways to reduce the thermal resistance of SMD LED, and introduced the concept of heat sink. This improved structure reduces the height of the original SMD LED structure. The metal lead frame is placed directly at the bottom of the LED device. The reflecting cup is formed by injecting plastic around the metal frame. The chip is placed on the metal frame. The metal frame is directly welded on the circuit board through solder paste to form a vertical heat dissipation channel. Due to the development of material technology, SMD packaging technology has overcome the early problems of heat dissipation and service life, and can be used to package 1-3W high-power white LED chips.
(3) COB-LED package
COB package can directly encapsulate multiple chips in metal-based printed circuit board MCPCB. Direct heat dissipation through the substrate not only reduces the manufacturing process and cost of the support, but also has the advantage of reducing heat resistance. PCB boards can be FR-4 materials with low cost (glass fiber reinforced epoxy resin) or metal-based or ceramic-based composites with high thermal conductivity (such as aluminium or copper-clad ceramic substrates). The wire bonding can be made by thermosonic bonding (gold wire ball welding) at high temperature and ultrasonic bonding (aluminum splitter welding) at room temperature. COB technology is mainly used in high-power multi-chip array LED packaging. Compared with SMD, it not only greatly improves the package power density, but also reduces the package thermal resistance (generally 6-12W/m.K).
The above three kinds of LED packaging sizes
have their own advantages, customers should choose and purchase according to actual needs.