scholarly journals Large-area fabrication of microlens arrays by using self-pinning effects during the thermal reflow process

2019 ◽  
Vol 27 (3) ◽  
pp. 3439 ◽  
Author(s):  
S. G. Heo ◽  
D. Jang ◽  
H.-J. Koo ◽  
H. Yoon
Keyword(s):  
Reflow Process ◽  
Large Area ◽  
Microlens Arrays ◽  
Thermal Reflow

Thermal Reflow Process for Glass Microlens Manufacturing

2008 ◽  
Author(s):  
Yang Chen ◽  
Allen Y. Yi ◽  
Donggan Yao ◽  
Fritz Klocke ◽  
Guido Pongs
Keyword(s):  
Numerical Simulation ◽  
Glassy Carbon ◽  
Glass Substrate ◽  
Simulation Method ◽  
Compression Molding ◽  
Fabrication Process ◽  
Holding Time ◽  
Reflow Process ◽  
Microlens Arrays ◽  
Thermal Reflow

This fabrication process includes three major steps, i.e., fabrication of glassy carbon molds with arrays of micro size holes, glass compression molding to create micro cylinders on glass substrate, and reheating to form microlens arrays. As compared to traditional polymer microlens arrays, glass microlens arrays are more reliable and therefore could be used in more critical applications. In this research, microlens arrays with different surface geometries were successfully fabricated on P-SK57 (Tg = 493 °C) glass substrate using a combination of compression molding and thermal reflow process. The major parameters that influence the final lens shape, including reheating temperature and holding time, were studied to establish a suitable fabrication process. A numerical simulation method was developed to evaluate the fabrication process.

A Microlens Array on Curved Substrates by 3D Micro Projection and Reflow Process

2012 ◽  
Author(s):  
Hao Zhang ◽  
Lei Li ◽  
David L. McCray ◽  
Donggang Yao ◽  
Allen Y. Yi
Keyword(s):  
Thick Layer ◽  
Microlens Array ◽  
Heating Time ◽  
Thickness Variation ◽  
Width Ratio ◽  
Reflow Process ◽  
Microlens Arrays ◽  
Exposure System ◽  
Planar Substrates ◽  
Thermal Reflow

Microlens arrays are becoming increasingly important because of their widespread applications in optical, electronic, and energy fields. Currently, microlens array fabrication processes are mainly developed on planar substrates. For nonplanar substrates, existing fabrication methods suffer from various disadvantages. This is largely due to the inherent technical complexity of 3D microstructure fabrication processes. In this work, an innovative 3D fabrication method for microlens arrays on curved surfaces is introduced. To fabricate the microlens array, a PMMA microlens array on a curved surface was used as the projection microlens array. A thick layer of positive tone photoresist SPR 220 was spin coated on a curved, titanium-coated aluminum substrate. A pre-designed pattern was projected onto the photoresist by using a home built exposure system. The development process resulted in micro cylinders on the curved substrate. A thermal reflow process was then performed on the cylinder array, forming a microlens array. Experiments were conducted to evaluate the factors that affect the shapes of the microlenses. These factors include film thickness variation, exposure and development variation, slope of the substrate, height to width ratio and heating time in thermal reflow process. Finally microlenses were tested by using a Twyman-Green interferometer.

Highly uniform manufacturing method for large-area microlens arrays

2017 ◽  
Vol 95 (1-4) ◽  
pp. 99-108 ◽  
Author(s):  
Xiaodong Zhang ◽  
Lihua Li ◽  
Zexiao Li ◽  
Changyuen Chan ◽  
Linlin Zhu ◽  
...  
Keyword(s):  
Large Area ◽  
Microlens Arrays ◽  
Manufacturing Method ◽  
Highly Uniform

An Investigation on the Profile of Microlens by the Thermal Reflow Process Due to Surface Tension and Gravity

2008 ◽  
Author(s):  
Jhy-Cherng Tsai ◽  
Yong-Sung Hsu
Keyword(s):  
Surface Tension ◽  
Critical Radius ◽  
Critical Size ◽  
Liquid Droplet ◽  
Bond Number ◽  
Diameter Ratio ◽  
Experimental Result ◽  
Critical Number ◽  
Reflow Process ◽  
Thermal Reflow

Microlens and its mold fabricated by thermal reflow using photoresist have been widely used for forming patterns in different scales. When the photoresist solidifies from melting condition, for example by the reflow process, its profile is formed based on the balance between surface tension and gravity. This research is aimed to investigate the influence of surface tension and gravity on the profile of microlens in thermal reflow process. Theoretical analysis based on the interaction between surface tension and gravity of liquid droplet is first investigated. The result showed that the height to diameter ratio (h/D), or the sag ratio, of the liquid droplet is affected by the Bond number (Bo), a number defined as the ratio of gravity to surface tension. The sag ratio is not sensitive to Bo when Bo is small but the ratio decreases as Bo increases if Bo is over the critical number. Based on the analysis, the critical number for the AZ4620 photoresist on a silicon substrate is 1, corresponding to the critical radius of droplet R = 2,500μm. When the size of the droplet is less then the critical size, the profile is mainly controlled by the surface tension and thus the sag ratio is about the same regardless the size. The profile, in contrast, is highly affected by the gravity if the size of the droplet is larger then the critical size. The sag ratio decreases exponentially with respect to Bo in this case. Experiments are also designed and conducted to verify the analysis. Experimental result showed that the sag ratio of the photoresist reduces to 0.065 from 0.095 when Bo increases from 0.0048 to 0.192. The results showed that the trend is consistent to the theoretical model.

Tilted Microlens Fabrication Using Nano-Magnetic Particles

2015 ◽  
Vol 1105 ◽  
pp. 259-263
Author(s):  
Shih Yu Hung ◽  
Yu Ting Hung ◽  
Ming Ho Shen
Keyword(s):  
Magnetic Field ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Magnetic Particles ◽  
Lower Layer ◽  
Glassy State ◽  
Reflow Process ◽  
Photoresist Layer ◽  
Thermal Reflow

Double-layer heterogeneous photoresist method will be used firstly to obtain the round photoresist column with two layers of different photoresists. Since both photoresists are the positive-type, the exposure is only required once. During the thermal reflow processing, the upper photoresist layer (AZ-4620 and nanomagnetic powder mixture) reaches the glass transition temperature, which is transformed from a glassy state into a rubbery state. Since the glass transition temperature of the lower photoresist layer (AZ-5214E) is higher than the temperature of thermal reflow, the lower photoresist layer is still able to maintain its solid state. The lower layer creates a round base during the thermal reflow process, and then subjected to an appropriate magnetic field. The base can not only restrict the bottom shape of the liquid photoresist to a round shape but also prevent the sliding of liquid photoresist during the thermal reflow process, so the tilted microlens array can be obtained. We can vary the strength of magnetic field to control the oblique angle of the tilted microlens.

Polymer elastic bump formation through photodefinable thermal reflow process for system in foil package

2018 ◽  
Vol 28 (11) ◽  
pp. 115008
Author(s):  
Chung Woo Lee ◽  
Jae Hak Lee ◽  
Jun Yeob Song ◽  
Seung Man Kim ◽  
Yong Jin Kim ◽  
...  
Keyword(s):  
Reflow Process ◽  
Thermal Reflow

scholarly journals High–Thick Thermal Reflow Process Using Vacuum-assisted Micromolding for Submillimeter Microvalves

2021 ◽  
Vol 33 (12) ◽  
pp. 4441
Author(s):  
Takaaki Abe ◽  
Shunya Okamoto ◽  
Yoshiaki Ukita
Keyword(s):  
Reflow Process ◽  
Thermal Reflow

LARGE AREA PARALLEL SURFACE NANOSTRUCTURING WITH LASER IRRADIATION THROUGH MICROLENS ARRAYS

2010 ◽  
Vol 17 (03) ◽  
pp. 383-387
Author(s):  
C. S. LIM ◽  
M. H. HONG ◽  
Y. LIN ◽  
L. S. TAN ◽  
A. SENTHIL KUMAR ◽  
...  
Keyword(s):  
Substrate Surface ◽  
Microlens Array ◽  
Laser Pulses ◽  
Polymer Materials ◽  
Direct Writing ◽  
Large Area ◽  
Microlens Arrays ◽  
Force Microscopy ◽  
Surface Nanostructuring ◽  
Parallel Surface

In the past decade, the development of nanoelectronics and nano-optics has attracted much interest in surface nanostructuring of semiconductor materials. The irradiation of a microlens array by a laser beam generates many focused light spots, which can act as a direct writing tool on photo-polymer materials. This maskless surface nanostructuring technique enables thousands to millions of identical nano-features to be patterned in a couple of laser pulses. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images show that nano-features were patterned uniformly on the substrate surface, which suggests a versatile way of parallel surface nanostructuring over a large area. The simulation results of the energy flux distribution at the focal plane of the microlens arrays will also be discussed.

Analysis of Thermal Reflow Process for Polymer Microlens Fabrication

2018 ◽  
Vol 35 (3) ◽  
pp. 319-325 ◽  
Author(s):  
Ji Hoon Lee ◽  
Sang Hyuk Yum ◽  
Seung Mo Kim
Keyword(s):  
Reflow Process ◽  
Thermal Reflow
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