Optimum Encapsulation - Wacker Chemie AG

Optimum Encapsulation

Developed in South Korea

Display screens at the Hong Kong stock exchange: the selective use of semiconductor materials and doping enables LEDs to glow in a great many different colors.

WACKER has responded to growing demand for suitable encapsulants – especially for bright and highly efficient white LEDs – by developing a portfolio of high-quality silicone encapsulants at the Center of Electronics Excellence (COEE) in Seoul. This portfolio comprises four new products: LUMISIL® 590, LUMISIL® 591, LUMISIL® 740 and LUMISIL® 770, which are tailored to the different designs, applications and operating conditions of modern LEDs.

Molded Packaging

An LED – by this is meant the electronic component suitable for installation in a circuit, the so-called LED package – consists of the semiconductor chip along with all the electrical, mechanical, thermal and optical interfaces to the surroundings. There are currently several different processes used for mounting chips in packages. but the key step in all of them is the encapsulation of the sensitive chip.

R&D experts at WACKER’s Center of Electronics Excellence in Seoul develop encapsulation materials tailored to LEDs.

LEDs become hot during operation and develop more and more heat the higher their electrical power consumption. The heat released can raise the temperature of the encapsulant significantly. At the same time, the encapsulant is also exposed to the light emitted by the chip. Heat and light age the encapsulating material, with the rate and extent of the damage largely determined by the type of material. The encapsulant can gradually become brittle. It then loses its protective function, becomes increasingly less transparent and discolors. All this degrades the luminous efficiency. If the LED is to achieve a long service life, the encapsulant must withstand these stresses in the long term.

Silicones are known for their resistance to heat, changes in temperature, light, UV radiation and many chemical effects. “In this respect, they are far superior to the epoxy resins that are widely used for encapsulating LED chips,” says Dr. Hyun-Kwan Yang, who is a developer at COEE. Because of their compliance, silicone elastomers are also capable of damping vibrations and absorbing thermomechanical stresses. They can also be made highly transparent and their flow properties adjusted as needed. “For all these reasons,” adds Dr. Yang, “silicones’ share of the LED-encapsulant market has grown significantly in recent years.”