WACKER launches new silicone rubber for LED packaging, high temperature resistance, radiation, and curing

Munich-based Wacker Chemie AG has successfully developed two new materials for LED packaging. These two silicone encapsulants, LUMISIL740 and LUMISIL770, cure into highly transparent silicone elastomers and withstand extremely high operating temperatures and intense light radiation without yellowing or embrittlement, especially for Efficient LEDs for packaging.

Figure: WACKER's new LUMISIL740 and LUMISIL770 normal refractive index (NRI) packaging materials

The two new LED packaging materials, LUMISIL740 and LUMISIL770, are two-component formulations that can be crosslinked by a platinum-catalyzed addition reaction at room temperature. The vulcanizate can achieve a typical 1.41 refractive index of polydimethylsiloxane. The rate is "Normal Refractive Index Encapsulant". They can effectively protect LED-sensitive semiconductor chips from environmental influences, and can also be used as a carrier for fluorescent dyes to specifically change the color of LED light.

The LUMISIL740 and LUMISIL770 are unique in that they are extremely resistant to high temperatures, light and temperature changes. An aging test can be confirmed here: after the test sample made of LUMISIL740 is stored at 245 ° C for 500 hours, there is no yellowing and embrittlement, and even after 1000 hours, the vulcanizate hardly changes. . LUMISIL740 has proven to be particularly resistant to the combined loads of temperature and light. In the temperature change test from 125 degrees Celsius to minus 45 degrees Celsius, both package materials have withstood more than 1000 test cycles, so they can also well balance the thermal tension caused by different thermal expansion of materials used in LEDs. .

These new silicones are durable and are especially suitable for packaging LEDs that heat up quickly and have intense light radiation. The main difference between the two products is the hardness of the vulcanizate. LUMISIL740 can be crosslinked into a material with a Shore A50 hardness, and LUMISIL770 is slightly harder, up to Shore A70. The overall performance of the LUMISIL740 is tailored to the package of multi-chip LEDs; this LED has no housing and is densely mounted directly on the board in chip-on-board (COB) technology. LUMISIL770 is the ideal choice for single-chip LED packages.

The viscosity of the two encapsulating materials allows it to be applied by a dispensing process without difficulty. The self-adhesive formulation of LUMISIL 740 and LUMISIL 770 enables the product to attach itself to semiconductor chips and common reflective films and housing substrates without the need for pretreatment.