NEPCON JAPAN 2019/36th ELECTROTEST JAPAN/20th IC & Sensor Packaging Technology EXPO/20th ELECTRONIC COMPONENTS & MATERIALS EXPO/PWB EXPO/20th Printed Wiring Boards Expo/9th FINE PROCESS TECHNOLOGY EXPO
New proposals in substrate with metal film were easy to notice

Picture 1. Demonstration of flexible OLED

January 16-18, NEPCON JAPAN 2019/36th ELECTROTEST JAPAN/20th IC & Sensor Packaging Technology EXPO/20th ELECTRONIC COMPONENTS & MATERIALS EXPO/PWB EXPO/20th Printed Wiring Boards Expo/9th FINE PROCESS TECHNOLOGY EXPO were held in Tokyo Big Site. In this here, main topics are picked up.

Yamagata University demonstrated a full flexible OLED

As concerns device, Yamagata University exhibited several OLEDs for lighting device, and appealed its superiority. Main exhibition was a full-flexible device. As picture 1, it can be bended not only vertically but also horizontally. It was encapsulated by 2 PEN films (0.1 �o thickness), and was covered with a desiccant film on whole area of device. By the way, there were a lot of dark spot defects in this sample.

Possible to use a polymer instead of ITO as an anode by use of Al electrode mesh

As regards material, demonstrations of film with metal electrode were easy to notice in this time. First of all, Toyo Aluminum appealed an Al mesh electrode for OLED lighting device and organic solar cell. Figure 1 shows its structure. Firstly, an Al foil is patterned by the wet-etching process, as a result, Al mesh is formed. It is implanted into resin layer by an original process.

Its surface flatness is Ra = 10 nm class, and low sheet resistance same as 1 Ω/□ and under is obtained. Therefore, if it's used as auxiliary electrode of anode, a conductive polymer such as PEDOT/PSS instead of ITO can be used as anode. Furthermore, it's possible to form main mesh electrode and connecting wiring in circuit of device at the same time. In this case, it may be possible to directly connect Al electrode and IC chip without ACF (Anisotropic Conductive Film). Of course, a device can become to be easily flexible by making use of a plastic film substrate because of existence of thin Al film.

Picture 2. OLED with Al mesh electrode

Figure 1. Structure of Al mesh electrode

The company will supply this 3 layers film. In the booth, as picture 2, an OLED lighting device was exhibited. It was pilot-produced by Yamagata University. In this sample, PEDO/PSS was used as an anode. By the way, its sales price is expected to be inexpensive compared to that of the conventional film with ITO.

Ag Nano wire film with high stability has been developed
　
By contrast, Showa Denko exhibited a transparent conductive film with high weather resistance and light resistance for touch-panel of in-vehicle system. In this film, an original Ag Nanosize wire is used as main component. Its sheet resistance is 35 - 40 Ω/□, optical transmittance is 90 %, and haze is 0.9 %. In short, basic specification is almost same as that of the competing product.

Picture 3. Ag Nano wire transparent conductive film

Figure 2. Stability in high-temperature and high-humidity environment

On the other hand, its durability is expected to be superior compared to that of the competing product because of using original resins, which were doped as a binder of conductive layer and overcoat layer. Figure 2 shows stability in high-temperature and high-humidity environment (85 ℃/85 ％RH). Sheet resistance of this conductive film was not almost increased, on the other hand, that of competing reference was greatly increased. By the way, Ag layer can be patterned by the conventional manufacturing processes such as the photolithography + wet-etching method or the laser direct etching method.

Ultra-flat film can be deposited by use of a novel sputtering

With respect to manufacturing system, Canon Anelva appealed a new sputtering deposition, which is called as the energy treatment sputtering method. It's useful for ultra-flatness application, for example, interlayer of semiconductor, anode of OLED, and so on. In this method, a functional film is deposited by the sputtering method and a certain assist treatment, such as ion implantation. In short, deposited film grows not at column shape but at film shape. In other words, deposition is done at suppression of grain grow. In fact, SiO2 film was deposited at 700 nm thickness on Al film (200 nm), as a result, flatness of deposited film using this method was Ra ＝ 0.24 nm, on the other hand, that of deposited film using conventional sputtering method was Ra ＝ 3.73 nm. Furthermore, if film became to be thicker, there are not almost crucks in film.

By the way, deposition ratio is lower than that of the conventional sputtering method. However, deposition process is devised, for example, firstly a film is deposited for boundary of under layer by strong assist treatment condition, and then, it is deposited by weak assist treatment condition, decrease of deposition ratio can be minimized.

The screen printing can be adopted to curved shape

Picture 4. Printing sample on curved structure

Micro-tec announced to release a screen printing system for curved substrate “MTV-850s”. It has processed stage and R guide at concave or convex shape. It's possible to print continuously at same attack angle (for example 75°) every time. For this reason, high uniform thickness is obtained same as that of flat screen printing process. Picture 4 shows a printed sample on plastic film for in-vehicle application.