Talking about LED epoxy resin (Epoxy) packaging technology

The epoxy resin (Epoxy) used in the LED production process is one of the key points in the LED industry. Epoxy resin is an organic polymer compound which generally contains two or more epoxy groups in the molecule, and their relative molecular mass is not high except for a few. The molecular structure of the epoxy resin is characterized by the presence of an active epoxy group in the molecular chain, and the epoxy group may be located at the end, in the middle or in a ring structure of the molecular chain. Since the molecular structure contains an active epoxy group, they can be cross-linked with various types of curing agents to form an insoluble, infusible polymer having a three-dimensional network structure.

In order to maintain its own airtightness, the LED IC protects the die from external corrosion, prevents moisture from entering the outside, and mechanically supports the wires, effectively discharges the heat generated inside and prevents the electronic components from being mechanically vibrated. The impact is broken and the characteristics of the component are changed. The use of different shapes and material properties (with or without colorants), functioning as a lens or diffusing lens, provides a form that can be held by hand.

First, the hardening temperature and time of the sealing resin for LED

1. The hardener for general LED sealing resin is acid anhydride, and its hardening temperature is about 120~130 °C.
2. The hardening time is shortened after the addition of the accelerator.

Second, the hardening time and the phenomenon of sputum and hardening rate
1. The thermal conductivity of the resin is small, and the internal hardening heat accumulates to affect the hardening rate. (reaction rate)
2. Inside (hardened heat) outside (oven) high heat Disply case Easy to deform.

Third, the compounding ratio and characteristics of resin and hardener
1. The amount of hardener used depends on the desired properties.
2. When the compounding ratio of the general hardener is small, the hardness of the cured product is hard and yellow.
3. When the compounding ratio of the hardener is large, the hardened material becomes brittle and the coloring is small.

Fourth, Tg (glass transfer point) and HDT (heat distortion temperature)
1. Test method: TMA, DSC.b: The temperature difference between the two is 2~3 °C.
2. The Tg becomes high after the addition of the filler.
3. The electrical properties of the epoxy resin (insulation resistance and the loss rate of the induced body loss) are consistent with the heat distortion temperature.
The epoxy resin used to form the envelope must have moisture resistance, insulation, mechanical strength, and high refractive index and transmittance for light emitted from the LED. The choice of packaging materials with different refractive indices, the influence of package geometry on photon escape efficiency is different, and the angular distribution of luminous intensity is also related to the structure of the die, the way of light output, and the material and shape of the package lens. If a pointed resin lens is used, the light can be concentrated in the axial direction of the LED, and the corresponding viewing angle is small; if the resin lens at the top is circular or planar, the corresponding viewing angle will increase.

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