Choices for LED Encapsulants

As the LED, or light emitting diodes, lighting market continues to grow at an increasingly robust pace, the demand for LED encapsulants and underfill materials is predicted to grow accordingly. In fact, lighting, not TV backlight units, is now the key driver of the LED encapsulant market. LED-use silicone encapsulants are categorized into phenyl and methyl types. Phenyl types are used in BLU, and methyl type silicone encapsulants are used in mobile phones, monitors, and tablet PC’s, among other uses.

Silicone Encapsulants

When considering a silicone encapsulant, there are many factors to take into consideration, aside from the use of the LED and its longevity. For example, what is the silicone encapsulant’s permeability and refractive index, or RI? Because all silicones are polymers, they can be synthesized to varying degrees of polymerization, which dictates various properties like molecular weight, which in turn dictates viscosity. One benefit of silicone encapsulants, is that the silicone can be formulated for specific applications: it can have a viscosity close to water, or it can be a solid.

Not All Silicone Encapsulants are Equal

Some silicones are simply higher quality than others. There are several factors to consider and to ask of any silicone industry provider. First, does the silicone yellow? Is it heat resistant, and up to what temperature? How is its transparency into high frequency ranges? Is it a pure silicone? Ionic impurity can cause major problems with reliability. What is their refractive index? How does it hold up to exposure to harsh conditions? As with all underfill materials, it is essential to ask the right questions for the application in question. For example, if higher refractive index silicones are required, then the manufacturer has to consider what’s attached to the LED assembly. Are there thermally conductive interfaces? Are there heat sinks? The more heat that’s generated, the greater the need and size of heat sink. Thermal management techniques will end up increasing the cost of the LED.

Encapsulants and Underfill Materials Continue to Evolve

The relationship between the packager and the material provider is essential.Whenever industry works with LEDs, of course, there is the issue of durability versus reliability, making the choices at play when it comes to silicone LED encapsulants and underfill materials, essentially a game of compromise. As a relatively new lighting source, industry is continuously refining its approach.