Beside LED going for a more or less a standard footprint of 3mmx3mm, more lens is going to use liquid Silicone moulding process.
The reason is that the Silicone has the following Characteristics:
Provide high power light emission for continuous operation
Thermal stability at -115 ~260°C
Low shrinkage: <1%>95% transmission at 400 nm
Refractive index: 1.38 to 1.61
High heat resistance until 180˚C
Excellent UV resistance up to 300nm
Low impurity content
Good discoloration resistance
Major equipment supplier is ASM and Towa.
Refer to ASM official web site for more technical infomation or contact your local ASM office for further assistance.
Web site: www.asmpacific.com