LED packaging technology are mostly in discrete device packaging technology based on the development and evolved, but there are a lot of particularity. Under normal circumstances, the discrete devices of the tube core is sealed in the package body, the package main function is to protect the die and complete the electrical interconnection. LED package is complete output electrical signal protection die normal work output: visible light function, both electrical parameters, another optical parameters design and technical requirements, and can not simply be discrete devices package for LED.

The core of the LED light emitting part is a tube core constituted by the p-type and n-type semiconductor, a pn junction, when the minority carriers injected into the pn junction with the majority carrier recombination, will emit visible light, ultraviolet light or near infrared light. But the pn junction area of photons emitted non-directional, i.e. every direction emission has the same probability, therefore, all of the light generated by the not die can be released, which depends primarily on the quality of semiconductor material, the structure and geometry of the die , encapsulation the internal structure of the encapsulating material, the application requirements to improve the LED the inner and external quantum efficiency. The conventional Φ5mm type LED package is the edge length of 0.25mm square die bonding or sintering of the lead frame, the tube core of the positive electrode through the ball contact point and Watkins, the bonded inner lead and a pin connected to the negative electrode through reflection Cup and another pin connected to the lead frame, and then top with epoxy resin coating. The role of the reflection cup is a side surface of the collection tube core, the interface of the light emitted, the emission angle within a desired direction. Encapsulated with epoxy resin at the top is made of a certain shape, there are several effects: protect the die without external erosion; using different shapes and material properties (doped or not doped bulk toner), from the lens or a diffusing lens function, the angle of divergence of the control light; the refractive index of the tube core and the refractive index of air is too large, resulting in the tube core inside the total reflection critical angle is small, the light generated by the active layer, only a small portion is removed, most easily in the tube core internal is absorbed by multiple reflections and easy total reflection occurs resulting in excessive loss of light, the choice of the corresponding refractive index of the epoxy resin to make the transition, improving the light emission efficiency of the tube core. The epoxy resin used for constituting the shell and tube must have a moisture resistance and insulation properties, mechanical strength, and on the tube core refractive index and a high transmittance of light emitted. Select packaging materials of different refractive indices, the impact of the package geometry on the photon escape efficiency is different, and the angular distribution of the luminescence intensity is used with the die structure, the light output, the package lens material and shape. Marquise resin lens, the light can concentrate in the axial direction of the LED, corresponding Perspective smaller; if the top of the resin lens is a circular or flat-type, and its corresponding angle will increase.

Under normal circumstances, the emission wavelength of the LED changes with temperature to 0.2 nm / ° C, the spectrum width increases, affect the color vividness. Maintain color, when forward current through the pn junction, fever, loss of the junction area temperature rise at near room temperature, and the temperature is increased by 1 ° C, LED luminous intensity corresponding to a decrease of 1%, package heat dissipation; The purity and the luminous intensity is very important, the past to use to reduce the approach of its drive current, reducing the junction temperature, the majority of the LED drive current is limited to around 20mA. However, the light output of the LED increases with increasing current, at present, a lot of power type LED drive current up to 70mA, 100mA or even 1A level, the need to improve the package structure, new LED packaging design concept and low thermal resistance package structure and technology, to improve the thermal properties. Example, using flip-chip structure of a large area, the selection of the good thermal conductivity silver glue, increasing the surface area of the metal stent, the solder bump silicon carrier is mounted directly on the heat sink upper method. In addition, application design, PCB circuit board thermal design, thermal performance is also very important.

Into the 21st century, the LED high efficiency, ultra-high brightness, full color continuous development of innovative, red, orange LED light efficiency to reach 100Im / W green LED to 501m / W, single LED luminous flux reached tens Im. LED chip and package is no longer along the Gong traditional design and manufacturing mode, increase the light output of the chip, the R & D is not limited to change the number of impurities in the material, lattice defects and dislocations to improve internal efficiency, at the same time, how to improve die and the package of the internal structure, enhanced LED interior to produce photons emitted chance to improve light efficiency, solve the heat, take the light and heat sink optimization design, improved optical performance, and accelerate the process of surface mount technology SMD the mainstream industry R & D direction .