Refractory Metals for the LED Industry

Light-emitting diodes, commonly known as LEDs, are semiconductor light sources which come in a variety of color, and have a number of key applications, with use in fields as diverse as aviation, traffic signals, advertising, automotive divisions, and general lighting.

The practicality and adaptability of LEDs has led to the development of ground-breaking video and text displays, in addition to the ability to control electronic items, including televisions, remotely. Moreover, it can be argued that LEDs are more environmentally friendly than standard filament lights.

From 2015 onwards, LED sales are predicted to be equal more than 230 billion per year. As a result, it is clear that LEDs are a product of the future, and their construction of these pioneering materials is made possible only through the use of high-quality, load resistant components.

Due to their unique physical properties, these component elements are frequently made from refractory metals. This article details the production of these components, in which PLANSEE plays an instrumental role.

The Role of Crucibles in LED Production

Sapphire is a required material for the production of LEDs. Sapphire is typically grown at highly-elevated temperatures of approximately 2000˚C and above, in pressed-sintered or formed crucibles made from molybdenum and tungsten. As a result of their resistance to the extreme temperatures required in this process, and the lack of risk of contamination of the sapphires, these refractory metals are ideal for the production of crucibles.

PLANSEE also offers the appropriate hot zones, shield packs, heaters and a broad range of spare furnace parts for sapphire crystal growth. What is more, PLANSEE designs the ‘hot zone’ to respond to consumer requirements even before production.

It is incredible to note that the sapphire material from a single PLANSEE crucible can aid in the production of 3,000,000 high-performance LEDs.

Following the creation of the sapphire crystal, an epitaxial process is carried out to apply semiconductor layers that produce light in LEDs to the substrate. The fine sapphire wafers, which measure around one square millimeter, act as a perfect substrate materials.

Components for Epitaxial Processes

The sapphire wafer is applied alongside the semiconductor layers in an LED, using the MBE (Molecular Beam Epitaxy) process or MOCVD (Metal Organic Chemical Vapor Deposition) process. PLANSEE can offer components made of tungsten, molybdenum and special alloys for the coating reactors which are resistant to extreme temperatures.

Further to this, PLANSEE works closely with their clients to ensure that the components are thoroughly tested in simulation conditions. In order to answer a broad range of vital questions, such as ‘How would temperature distribution appear during furnace operation?’, model based calculations are carried out.

Boats and Coils

A reflector layer is frequently deposited on semiconductors, and acts to guide the dispersed light in the direction required. Throughout the coating process, evaporation boats and coils made from tantalum, molybdenum, tungsten and their alloys usually heat up the material for evaporation. PLANSEE’s evaporation boats and coils are electrically conductive, and offer low vapor pressures alongside high melting points.

Carrier Plates Made of Molybdenum and MoCu

LEDs are three times more efficient in comparison to conventional lighting, however, LED chips do generate heat. Making use of MoCu and molybdenum discs, PLANSEE can offer materials with an ideal coefficient of thermal expansion (CTE) appropriate for the CTE of the semiconductor material. It is possible to merge the carrier plates provided by PLANSEE to the semiconductor to ensure that heat is dissipated consistently.

Phosphor Products for the LED Industry

In a technique which is inexpensive but reliable, a coating of phosphor can be applied to the LED to transform blue or UV light into a different color, as required. The phosphor is stimulated by the LED’s light to produce a yellow-tinged light, and the yellow light from the phosphor can therefore be combined with the light of a blue LED to generate attractive color temperatures.

The US associate of the PLANSEE Group, GTP, is making ground-breaking developments in the field of production of phosphor materials for the LED industry. Additionally, in order to prolong the useful lifespan of phosphor materials, GTP has developed novel coatings.

Heat Spreaders for High-Performance LEDs

PLANSEE’s heat spreaders aid in cooling down components in instances where high-performance LEDs become heated. These heat spreaders are constructed from tungsten, molybdenum, Cu-MoCu-Cu, WCu and MoCu laminates.

Precision Optics

To assist in protection of the semiconductor, as well as to ensure that bundled light disperses in the appropriate direction, the LED is housed in a glass lens. The forming tools used to produce these precision lenses are developed by tool specialists at CERATIZIT.

This information has been sourced, reviewed and adapted from materials provided by PLANSEE.

For more information on this source, please visit PLANSEE.