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37th INTERNEPCON JAPAN
New proposals of printing manufacturing process were actively introduced
for flexible device inclusive of 3D structure
January 25-27, 37th NEPCON JAPAN was held in Tokyo Big Site. In this here,
main topics about electronics are picked up.
Toray appealed mount patterning process of RGB-LED chips for Micro-LED
Pic.1 Pilot-produced Green-Micro-LED |
First of all, with respect to Micro-LED, Toray appealed its materials and used manufacturing process. Concretely, bonding bump material, insulation material, wiring material for the edge, and the laser lift-off system (Toray Engineering) and manufacturing process were introduced.
Figure 1 shows recommended mount patterning process of RGB-LED chips. Firstly, LED substrate and a release plate are assembled, and then, sapphire substrate is removed from the LED substrate. The next, LED-chip is transferred to a catch plate by direct laser irradiation of 355 nm wavelength at parallel scanning. Its flow is repeated by 3 times (R, G, B). As a result, RGB pixel pattern is regularly completed on the catch plate. Finally, this pixel array is transferred to a display substrate. In this laser lift-off process, dust and remains don't occur. As you can image, its productivity is 180 times of that of the pick & place method, is a initially physical process. For this reason, it's useful for mass production. In the booth, a small G-LED sample composed of 4500 G-LED chips (20×30μm).
Fig 1. Process flow of Micro-LED
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New transfer process is effective for curved structure device by use of PET/PVA film
Aicello introduced PET/PVA 2 layer film "SO sheet" for transfer process of curved structure inclusive of 3D structure. New manufacturing process is realized by effective making use of property of soluble PVA (Polyvinyl Alcohol) in this sheet.
Pic.2 Patterned transfer samples |
Concretely, first of all, various conductive materials are patterned on PVA in SO sheet by the existing methods, such as the photoetching method and various printing methods. The next, PET film is released from SO sheet, and then, SO sheet is laminated to an original substrate by use of adhesive. As a result, electrode pattern is transferred to the substrate. Finally, PVA film is removed by water washing. Final resolution and accuracy of patterning is almost same as that of above 1st patterning. In short, process repeatability is superior.
As you image easily, it's effective for curved structure inclusive of 3D structure because of superior following against curved shape in the transfer process. As picture 2, various samples were exhibited in the booth. Furthermore, Ag, Au, CNT (Carbon Nano tube), PEDOT/PSS, and hydrophobic polymer (CYTOP) could be transferred in the pilot-production. In a word, its's possible to correspond to wide range of patterning methods and materials.
High conductive Cu film is obtained by flexo printed and light annealed Nano Cu ink
In printing process, new materials and systems were proposed one after another. Ishihara Chemical appealed originally conductive Nano Cu inks, were reported in the past. If this Cu ink is used, highly conductive Cu electrode is obtained at ultra-high speed by light anneal using Xe flash lamp. Various models for the screen printing, flexo printing, gravure printing, and ink-jet printing, are released. In this time, the flexo printing ink "F-03B" was mainly introduced because of most practical potential.
Pic.3 Flexo printed sample |
Average diameter of Cu grain is 80 nm, and density of ink is 65 - 75 %. After flexo printing, it's dried at 80 ℃, and then, annealed instantaneously by Xe flash lamp. As a result, low resistance same as 4 - 5 μΩ･cm is obtained. Of course, damage against the substrate don't occur because of anneal mechanism. In short, it's possible to easily correspond to low thermal resistance substrates, such as various plastic films and paper.
In the booth, RFID sample using paper was exhibited. Furthermore, this printed sample was annealed in actuality by real lamp anneal system.
Printing process of Cu electrode is further speeded up by LED dry and light anneal
On the other hand, Micro-Tec introduced a new Cu2O paste, was developed by Nippon Chemical Industrial, and also, announced
to jointly develop a new dry system for dry process.
Pic.4 Printed samples and LED dry system |
Its paste is composed of Cu2O grain (diameter:100 - 200 nm) solvent, and so on. It can be annealed
at ultra-high speed and atmosphere environment by light anneal. In light
anneal process, O2 is removed, as a result, it's reduced. After anneal, high conductive Cu
electrode (20μΩ･cm) is completed. Of course, it's adhered to various plastic
films and papers at high sticking force.
In this time, the both companies have developed a new dry system "META-FLASH" using a LED lamp, in order to further reduce process time. If this system is used in dry process, it can be dries at mere 10 seconds because of use of line scanning of linear LED lamp. Of course, above light anneal time is 1 second and under. In short, total productivity is great high.
Ultra-high speed printing is realized by new concept "electric printing"
Pic.5 3D samples with wire electrode by electric printing and electroforming
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As regards same printing process, Okuno Chemical Industries introduced new concept printing method "electric printing", which was originally developed by Research Laboratory of Electric Printing. Its flow is the following：①Circuit is formed by CAD design, and then, a printing mask is manufactured by laser fabrication, ②The printing mask is put on a plastic film (substrate), and then, an "electricity" is printed by static electricity using voltage charge, ③This circuit is developed by an original toner. As a result, invisible printed circuit is completed.
The next, a catalyst is adhered to printed pattern at self-aligning, and then, Cu film is deposited, and grown on catalyst by non-electrolytic plating method. In short, Cu electrode is completed by general non-electrolytic plating process.
Its printing speed is mere 1/100 second. Fine line same as line width 10 μm order can be patterned because of mechanism using static electricity. Of course, printed mask can be easily manufactured by the desktop environment. Furthermore, in case of curved structure substrate, breaking does not occur in Cu wiring because of plating Cu film after curved deforming of plastic film. On the other hand, it's easy to occur in the conventional non-electrolytic plating method by curved fabrication because of Cu deposition at curved state.
As picture 5, 3D wiring samples on concave film and convex film were exhibited in the booth.
Self-repaired resin has greatly potential
As concerns material, Resinous-Kasei exhibited a self-repaired resin "SH-001". It's a bisphenol A epoxy resin. Its bulk liquid becomes to be cured by anneal at 100 ℃ for 30 min. And also, defect such as void is repaired at self by anneal at 120 ℃, which is same as Tg. Furthermore, it changes to thermal plasticity by anneal at 150 ℃, and also, returns to initial liquid by anneal at 200 ℃. In short, state changes by reversible nature, which is given by original reversible nature unit.
In the demonstration, solid resin was repaired at self by anneal using the laminator system. Its application is not clear, but is considered to be useful for colorant, interior decorating of automobile, and cover film of smartphone, and so on.
New applications will be developed by structured color film
Mitsubishi Chemical proposed a structured color film. It's a feigned film of biostructure, such as butterfly, buprestid, and tropical fish, and also, color obtained by fine surface structure. This phenomenon is caused by only interaction such as interference, scattering in between air and fine structure. By the way, fine structure is colorless. However, selective wavelength is reflected by fine structure is seen for human's eye.
Pic.6 Structure color film |
Pic.7 Coated plastic samples by use of structure color material |
In this artificial structure film, optical interference effect is generated by regularly arrangement of Nano size transparent grain at self-aligning. Color is controlled by grain size. For example, green is emitted by use of grain with 220 nm diameter. In a word, reflective wavelength is determined by grain size. However, in artificial structure film, visible color is changed by view angle. Its phenomenon is advantageous or disadvantageous. It's not useful for display use, which is required to be wide view angle.
Picture 7 shows a plastic mold sample for interior decorating of automobile. Structure color was realized by coating bulk liquid on plastic mold. As you see, it's possible to give structure color to curved structure. In the near future, the company will try to pattern by the IJ printing method.
HighChem appealed Spiro-MeOTA as a hole transporting material of perovskite solar cell
With respect to perovskite solar cell, HighChem appealed Spiro-MeOTAD as hole transport material. It's a popular material as HT material of perovskite solar cell. The company makes assurances high purity product same as 99.5 % and over, and also, supply not only just powder but also coating liquid inclusive organic solvent and so on. |
