The quality of the LED display is that the use is packaging technology, and the key to the packaging technology, besides the advanced and reliable technology, has a direct relationship with the technology management and control of the packaging chip material and packaging. With the rapid development of the media industry, advertising, business exhibition and wedding industry, the quality of the display screen is very rapid. As the volume increases, the requirements for LED components become higher and higher.
The materials used in LED package include chip, crystal glue, bracket, encapsulation glue, bonding wire and so on. The following is a brief introduction of the basic development of domestic packaging materials.
1. Chip
As the core of LED device, LED chip determines the life span and luminous performance of the whole LED display. As the cost of LED chips decreases, the size of LED chips cut smaller and smaller, which brings a series of performance problems.
Two, glue
There are two kinds of packaging glue: silicone and epoxy resin.
(1) organosilicon. Silicone has high cost performance, excellent insulation, dielectric and adhesion. Its disadvantage is easy to absorb moisture and weak gas tightness. It is rarely used in the packaging applications of LED devices.
(2) epoxy resin. Epoxy resin is easy to be aged and has poor heat resistance. It is susceptible to wet, short wavelength light and easy to discoloration at high temperature. Epoxy resin has certain toxicity. LED thermal stress matching degree is not high, which greatly affects the performance and life of LED.
Three, LED stents
(1) the structural improvement design of the support. The PLCC stent is physically bound by the combination of PPA and metal, and the gap becomes larger after a high temperature reflux furnace, which leads to the water vapor entering the device easily along the metal channel to affect the reliability.
(2) the role of the scaffold. PLCC (Plastic Leaded Chip Carrier) bracket is the carrier of SMD LED device, which plays a key role in the reliability and light generation of LED.
(3) the production process of the scaffold. PLCC stent production process mainly includes metal belt punching, electroplating, PPA (polyphenyl two amide) injection molding, bending, five dimensional three-dimensional inkjet and other processes. Among them, electroplating, metal substrates, plastic materials occupy the main cost of scaffolds.
Four, bond line
Commonly used bonding wires for LED devices include gold wire, copper wire, palladium plated copper wire and alloy wire.
(1) plating palladium copper wire. Palladium plated copper wire is also called "palladium bond copper wire" palladium copper wire to prevent copper wire oxidation. Palladium copper wire has advantages of good welding, high mechanical strength and moderate hardness. It is commonly used in high density and multi pin integrated circuit packaging.
(2) gold line. Gold wire is the most widely used and the most mature technology, but the price is high, resulting in the high cost of LED encapsulation.
(3) copper wire. Copper wire has advantages of low cost, good heat dissipation and slow growth of intermetallic compound in the process of wire bonding. Disadvantages are easy to oxidize, high hardness and high strain strength. In particular, copper is very easy to oxidize under the bonding process of copper bonding, and the formation of the oxide film reduces the bonding performance, which puts forward higher requirements for the process control in the actual production process.
The better the material used for encapsulation, the better the packaging technology, the better the quality of the display. At the same time, China's packaging technology needs more communication with the world to be further innovated. I believe China's LED industry will be better in the near future.