LED packaging is used for informational applications, such as indicator and status lights and for some illumination applications as well. it is also successfully used for adhesive and aerospace application. The innovation of solid state lamp or light emitting diode (LED) marks a real breakthrough in the lighting industry. This device is highly versatile in its applications and is distinguished by its high reliability, long life and fast switching speed.

An LED is a semiconductor device wherein electrical energy is directly converted into optical energy, within a very narrow wavelength range. The light output of an LED is proportional to the forward current and the forward current is the function of forward voltage applied. The LED transits from a non-conductive mode to breakdown mode.

After the production of high lumen output LEDs operating at high current, the development of packaging technology was required to remove heat from the LEDs. High power LED packaging places new demands on chip design, die attach, submount design, encapsulation and lead frame design.

Packaging Design
Packaging design of LED semiconductors is a key contributor to producing better discrete component designs that perform more efficiently in a wide variety of operational and environmental conditions with higher performance and higher brightness applications. Current packaging performance efficiencies clearly shows that most conventional packages existing to date are inadequate for the demands of many current and future applications. Most LED package styles are designed for conducting substrate LEDs bottom of the LED, as opposed to planar circuit LEDs on insulating substrates.

LED packaging materials must enhance the light transmission, reliability and longevity of a device. Silicon delivers thermal stability to LED packaging. Silicon materials have higher coefficient of thermal expansion values, so they work well in encapsulation applications. Another factor to consider is the stress that expanding or contracting materials exert on wires in packaged assemblies. Stresses associated with high modulus values can break these wires or compromise the wire bond. However, silicon has a relatively low modulus value compared, eliminating this problem.

Technological Improvements
The industrial roadmap for LED identifies three areas of technological improvements in packaging. The three areas are:

• Materials that increase the extraction efficiency of the light from the LED die
• Optics that improve the extraction of light from the final package
• Thermal management of the LED die and lighting system.

The ultra-high lumen LED arrays has been hindered by the inability of the LED packaging to wick away the heat and keep the LEDs cool, causing them to fail. A multi-layer ceramic-on-metal packaging has solved the problem. Designated as low temperature co-fired ceramic-on-metal, it is a breakthrough technological development providing an unmatched combination of thermal performance and interconnectivity between individual light-emitting diodes, resulting in lower mechanical stress, greatly lengthened LED life and reliability.