What Is LED Packaging?

In the lighting industry, LED refers to the LED package, not an LED chip. The LED package is a combination of one or more LED chips with mechanical supports, optical elements, electrical connections and thermal conduction paths.

The LED chip is very susceptible to physical and chemical damage. The purpose of the LED package is to prevent damage to the LED chip, to make the electrical and thermal connection between the LED and the printed circuit board, to adjust the color through phosphor conversion, and to ensure that the light is ejected in the most efficient way.

A typical LED package contains a carrier substrate that provides mechanical support to the LED chips and thermally bonds them. The negative and positive ends of the LED chip are connected to the lead frame or electrodes of the carrier layer by wire bonding or die bonding. The binding wire used in the LED package is usually made of gold material due to its high electrical and thermal conductivity. There is also the use of copper and silver due to their relatively low cost. This entire structure is protected by a plastic enclosure.

The LED package has a coating to cover the LED chip and convert the light emitted by the LED. The coating is a kind of mixture containing phosphorus and organic polymer. Most LEDs use silicon polymers for phosphor coating due to their high thermal stability, high optical transparency, high refractive index and good adhesion. The coating is distributed over the LED chip and through curing (curing of the polymer material) a transparent solid layer that protects the LED is obtained. An optical element such as a hemispherical lens can be mounted on the phosphor coating to control the light distribution.

LED packaging is a critical process that affects the thermal performance, optical efficiency, color quality and lumen depreciation. The LED package is used to protect the LED chip and connections from the outside environment. Packaging can make up 50 to 60 percent of an LED’s total cost.