NEPCON JAPAN 2017-46th/Electronics R&D and Manufacturing Technology Expo
Demo of screen-printing becomes to be active

January 18 - 20, NEPCON JAPAN 2017-46th/Electronics R&D and Manufacturing Technology Expo were held in TOKYO BIG SIGHT. Main topics in these exhibitions are picked up.

Firstly, with respect to the screen-printing field, NBC Meshtec has appealed a new type screen-mesh cloth “V-SCREEN NEXT”, which was announced at the last minute by press announcement. It's a mesh cloth with Toray's liquid crystal polymer. Diameter of this polymer is 20 μm at minimum. Also, it's possible to increase mesh number same as 420 per inch in this mesh cloth. As you know, in the existing V-SCREEN with Kuraray's polymer, diameter of wire and mesh number are limited to 23 μm and 380 per inch respectively. For this reason, V-SCREEN NEXT is suitable for fine printing needs.

Dimension accuracy and durability of V-SCREEN NEXT are same as that of V-SCREEN. Figure 1 Shows shift length of 100 shot printing and 3000 shot printing. It's suppressed by ± 10 μm. The company will supply this mesh cloth as an original fabric at April, 2017. By the way, in the booth, solar cell and touch-panel with printed Ag electrode (line width 40 μm) by use of this mesh screen mask.

Productivity is improved by the rotary screen-printing

Picture 2. Printed samples

Picture 1. Inside of the rotary screen-printing machine

On the other hand, Newlong Seimitsu Kogyo has appealed the rotary screen-printing technology, which is high productivity printing method. In the booth, the company exhibited some printed samples with comb-shaped electrode (0.2 �o line pitch), which is formed by the rotary screen-printing method. Printing speed is 20 m/sec at maximum, which is 5 - 10 times compared to that of the conventional flat screen-printing. On another front, printing accuracy and resolution of the rotary screen-printing is lower than that of the conventional screen-printing. Thus, it is suitable for low cost production use of low resolution device.

In the rotary screen-printing, high accuracy screen-mask is absolutely necessary. For this reason, Sonocom has developed a specific screen mask for the rotary screen printing. In this screen mask, Ni film is deposited on the conventional SUS mesh by the electroforming method, in order to increase strength and prevent crack. This flat screen mask is wrapped on the rotary unit of the printing machine. It's seam is 10 �o and under.

Quartz glass is directly fabricated by dry-etching

Picture 3. SEM image of fabricated quartz substrate by dry-etching

As regards fine process technology, Koshibu Precision has introduced that quartz glass substrate was directly fabricated by the dry-etching method. First of all, photoresist is coated on the substrate, and then, photoresist film is patterned at 3D shape by original 3D patterning technology (gray-scale mask). The next, the substrate is dry-etched by making use of this masking pattern. As you know, in case of the wet-etching, it's difficult to gain same shape as that of masking pattern because of occurrence of side-etching. On the other hand, in case of the dry-etching, it's possible to form same shape as that of masking pattern because of superior straight property of etching gas flow.

This time, the company pilot-produced microlens pattern (100 μm diameter, 15 μm height), and also, disclosed SEM image on the PC monitor as picture 3. By the way, O2 gas was used as an etching gas in this time; however, CF4 gas will be used in the future.