LED plant light packaging technology is mostly developed and evolved on the basis of discrete device packaging technology, but it also has its unique characteristics. Under normal circumstances, the die of the discrete device is sealed in the package, and the main function of the package is to maintain the die and complete electrical interconnection. The LED plant light package is to complete the output of electrical signals, maintain the normal operation of the die, and output: the function of visible light, which has both electrical and optical parameters. The design and technical requirements of the discrete device cannot be simply used for the LED. Plant light.
The core light-emitting part of the LED plant light is a pn junction die composed of p-type and n-type semiconductors. When the minority carriers injected into the pn junction are combined with the majority carriers, it will emit visible light, ultraviolet light or near-infrared light. . However, the photons emitted by the pn junction region are non-directional, that is, they have the same probability of being emitted in all directions. Therefore, not all the light generated by the die can be released, which mainly depends on the quality of the semiconductor material, the structure of the die, and the geometry. , Package internal structure and encapsulation materials, application requirements to improve the internal and external quantum efficiency of the LED.
The conventional Φ5mm type LED plant light package is to bond or sinter a square die with a side length of 0.25mm on the lead frame. The positive electrode of the die is connected to a gold wire through a spherical contact point, and the inner lead is connected to a pin, and the negative electrode is bonded. Connect to the other pin of the lead frame through the reflector cup, and then encapsulate the top with epoxy resin. The function of the plant lamp reflector is to collect the light emitted from the side and interface of the tube core and emit it in the desired direction angle. The epoxy resin encapsulated on the top is made into a positive shape, which has several functions: to protect the die from external corrosion; to adopt different shapes and material properties to function as a lens or a diffuser lens to control the divergence angle of light; The core refractive index is too much related to the air refractive index, resulting in a small total reflection critical angle inside the die. Only a small part of the light generated by the active layer is taken out, and most of it is easily absorbed by multiple reflections inside the die. , The total reflection is prone to cause excessive light loss, and the epoxy resin with the corresponding refractive index is selected as the transition to improve the light emission efficiency of the die. The epoxy resin used to form the tube shell must have moisture resistance, insulation, mechanical strength, high refractive index and high transmittance to the light emitted by the tube core.
When packaging materials with different refractive indices are selected, the packaging geometry has different effects on the photon escape efficiency. The angular distribution of luminous intensity is also related to the die structure, light output method, and the material and shape of the packaging lens. If a sharp resin lens is adopted, the light can be concentrated in the axis direction of the LED plant light, and the corresponding viewing angle will be smaller; if the top resin lens is round or flat, its corresponding viewing angle will increase.
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