Polymer dispensing and embossing technology for the lens type LED packaging

Abstract

This study presents a ring-type micro-structure design on the substrate and its corresponding micro fabrication processes for a lens-type light-emitting diode (LED) package. The dome-type or crater-type silicone lenses are achieved by a dispensing and embossing process rather than a molding process. Silicone with a high viscosity and thixotropy index is used as the encapsulant material. The ring-type micro structure is adopted to confine the dispensed silicone encapsulant so as to form the packaged lens. With the architecture and process described, this LED package technology herein has three merits: (1) the flexibility of lens-type LED package designs is enhanced; (2) a dome-type package design is used to enhance the intensity; (3) a crater-type package design is used to enhance the view angle. Measurement results show the ratio between the lens height and lens radius can vary from 0.4 to 1 by changing the volume of dispensed silicone. The view angles of dome-type and crater-type packages can reach 155° ± 5° and 175° ± 5°, respectively. As compared with the commercial plastic leaded chip carrier-type package, the luminous flux of a monochromatic blue light LED is improved by 15% by the dome-type package (improved by 7% by the crater-type package) and the luminous flux of a white light LED is improved by 25% by the dome-type package (improved by 13% by the crater-type package). The luminous flux of monochromatic blue light LED and white light LED are respectively improved by 8% and 12% by the dome-type package as compare with the crater-type package.

Silk-hydrogel Lenses for Light-emitting Diodes

“…We measured the radiation pattern of a LED die without a lens as the reference LED emission, and generated an identical LED die emission profile in the simulation. To understand the effect of lenses on light distribution profile, crater- and dome-type lenses 4 were simulated on top of the LED die (Fig. 2a ).…”

“…The invention of efficient blue light-emitting diodes (LEDs) has opened up a new way toward bright and energy-saving solid-state lighting (SSL) 3 , which has a very important potential to replace conventional light sources because of its energy saving, long lifetime and compactness 4 , 5 . For example, SSL can generate 50% reduction in electricity consumption and therefore decrease carbon emissions by 28 million tons per year, if the targeted LED performance levels are reached 6 .…”

“…Biocompatible material based hydrogels are widely used in tissue engineering as scaffolds 11 , 12 . Silk fibroin protein obtained from Bombyx-mori cocoons has been tested for various biomedical applications 4 , 13 – 15 , and a new type of hydrogel made of silk fibroin was recently demonstrated, which was used for microfluidic systems, multiphoton micromachining and tissue engineering 16 – 21 . Even though liquids have been used for various optoelectronics device applications, such as liquid crystals displays (LCDs), fluidic adaptive focusing and colour conversion layers 22 , 23 , silk hydrogel lenses have not been investigated for LED applications.…”

Novel UV-transparent 2-component polyurethane resin for chip-on-board LED micro lenses

“…Current requirements and the market volume of light emitting diodes (LEDs) and miniaturized CMOS image sensors have led to an increasing demand for low-cost optics and a notable growth of production capabilities [1][2][3][4]. LEDs are regarded as highly efficient light sources that offer a long service life, a wide range of colors and design options.…”

“…Polyurethane (PU) materials are also candidates for the encapsulation of LEDs and organic LEDs (OLEDs) in particular due to their excellent properties for lens formation by evaporative polymer droplet deposition and imprint processes [13,14]. Furthermore, silicone [4,15,16] and silicone hybrid materials, like epoxy-silicone resins [17][18][19][20] and sol-gel based siloxane [21][22][23][24] are widely used. The disadvantages of most conventional polymers are that they are hard and brittle because they have rigid cross-linked networks and decompose under the influence of radiation and high temperature, which leads to chain splitting and discoloration [6][7][8]10,17].…”