Gas-assisted UV Imprinting of Lens Array for LED Encapsulation and Optical Application
Date Issued
2015
Date
2015
Author(s)
Shu, To-Chung
Abstract
Wafer level LED packaging with lens structure can enhance the efficiency of packaging by integrating lens profile on the package and increasing the covered LED numbers in one operation. The packaging technique needs to be developed. On the other field, the lenses for the image acquisition system in smart wearable devices demand thin dimension and high performance. Lens array with various concave/convex surfaces can achieve such requirements. The fabrication technique has to be efficient. This study is devoted to the development of UV imprinting technique to fabricate lens array for those two applications: LED wafer level package and lens array with double-sided convex/concave profiles. The first part of this study is devoted to LED wafer level packaging by gas-assisted UV imprinting. PDMS mold is made by casting PDMS on electroplated Ni mold with micro-lens array. Spin-coating and doctor blade method were used to coat UV-curable resin onto the PDMS mold. It was found the doctor blade method could coat UV resin perfectly with the blade moving at a velocity of 0.17 mm/s. The gas-assisted UV imprinting process was then employed for packaging 25×25 lens array on a 4"" wafer. The results showed that homogeneous lens array with 98.9% height replication can be achieved with a gas pressure of 2.5 psi. The UV imprinting is used to fabricate double-sided micro lens array in the second part of this study. Lenses with convex surfaces on both sides, concave surfaces on both sides, and convex on one surface / concave on the other surface were fabricated. Homogeneous lens shape with 92.3% height replication were successfully fabricated with this process. This study proves that UV imprinting can be used for LED wafer level package and double-sided micro lens array fabrication.
Subjects
UV curing
wafer-level package
gas-assisted
double side structure
Type
thesis
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