There are many problems that can occur when silicone encapsulants that have a high gas permeability are used as a barrier coating for applications having to do with LEDs, especially HBLEDs, or high brightness light emitting Diodes. With high gas permeability silicone encapsulants, it is easy for gases to permeate the barrier coat. When oxygen permeates the encapsulant, for example, oxidation and sulferation can occur and this in turn can begin to degrade the light intensity, which is the opposite of what engineers who work on LED technologies are aiming for. Corrosion of any kind is quite destructive to devices implementing LED technologies and manufacturers strive to eradicate this potential problem.
Desirable Properties of Silicone Encapsulants
Luckily, there are quality low gas permeability silicone encapsulants on the market. These are usually phenyl group silicone materials, which are formulated specifically to have low gas permeability. Another characteristic that is desirable in silicone encapsulating materials is that of superior heat resistance. Methyl group silicones are specially formulated for having superior heat resistance. Ideally, packaging materials for LED applications like the ubiquitous HBLEDs, have both low gas permeability and heat resistance, as well as long term reliability. Some packaging now offers both in one encapsulant product.
A Market for Silicone Encapsulants
Such silicone encapsulants are being developed and widely used in the electronics market, particularly for applications like notebook PCs and mobile phones. Cell phones are now the largest sector of the electronics systems market, making up 18 percent of total electronic systems sales in 2013. This trend is predicted to continue with the projected compounded annual growth rate of 6.3 percent, at least through the year 2017. Because of this increased demand, electronics companies who work within the semiconductor industry must increase demand for certain products that are used in and continually improve the quality of mobile devices. Low gas permeable silicone encapsulants, barrier coatings, quartz wafers, substrates,conductive grease and other products fall into this category.
Of course, the correct barrier coating has to be used with any photoresist layer. There are barrier coats of varying thicknesses and composition. Barrier coats are thin transparent polymer films which function to minimize interaction between two resist layers. Barrier coats are essential for using CEMs or contrast enhancement materials, which are integral pieces in the semiconductor lithography process.