Overview of the Development of the Flexible Printed Electronics Industry (Part 1) — Review

Flexible printed electronics technology is an electronic manufacturing technology based on printing principles. Silicon-based semiconductor microelectronics technology once held an absolute dominant position in electronic technology for a long time. However, due to the increasing complexity of silicon-based integrated circuit manufacturing technology and the enormous investment required, its manufacturing is completely monopolized by a handful of major companies worldwide. Therefore, over the past decade, research and development of solution-based organic and inorganic semiconductor materials has spurred exploration of manufacturing various electronic devices using traditional printing techniques.

According to survey data, printed electronics technology and the industry cover a wide range, including organic, inorganic, or synthetic materials that can print circuits or electronic components, as well as transistors, displays, sensors, phototubes, batteries, lighting devices, conductors, semiconductors, and other devices, as well as processes and products for interconnecting circuits. Although printing processing itself does not have the high resolution and high integration of traditional micro-nano processing, its advantages of equal area, flexibility, and low cost are enough to enable printed electronics to play a role in many new application fields.

A decade in review

Regarding the printed electronics market, British market research firm IDTechEx began tracking it as early as ten years ago. The company publishes annual reports on the development of the printed electronics industry, including market assessments and forecasts. Figure 157 shows IDTechEX's assessment of the prospects for printed electronics development in 2008. At that time, he was very optimistic about the prospects of printed electronics, comparing the next 20 years of printed electronics development to the development of silicon semiconductors and microelectronics back then.

It has been 10 years since the prediction was made back then. Looking back at the development of printed electronics in 2018, the market did not reach the level predicted back then. In 2015, the president of Samsung Electronics presented at the Korean Flexible Printed Electronics Conference a comparison of the actual development level of the printed electronics market with early forecasts from different market research firms (Chart 158). Clearly, the actual market performance is far from earlier forecasts. A more detailed analysis of published market data reveals that although the market appears large on the surface, most of its share actually comes from traditional mature products and markets.

Chart 158: Comparison of Print Electronics Market Performance and Forecast (2015)

Chart 159 shows the market share breakdown of printed electronics published by IDTechEx in 2016. The total $24.2 billion market is not only printed electronics but also includes organic and flexible electronics. The latter two types of products may not necessarily be manufactured through printing.

For example, the $16 billion OLED display market does not fall under the printed electronics category and still uses vacuum vapor deposition manufacturing processes. The $6.5 billion sensor market consists mainly of blood glucose test strip products, which were mature products even before 2008. The $1.3 billion market for conductive inks is mainly focused on conductive pastes for printed crystalline silicon solar cell electrodes and printed touch screen edge electrodes, rather than the emerging low-temperature sintered nano conductive ink market.

Over the past decade, some early, well-known printed electronics companies have experienced dramatic ups and downs. For example, in 2008, the American company Kovio released a product for preparing thin-film transistors and RFID using printed nanosilicon ink, pioneering printed inorganic nanomaterials and becoming a product pioneer. At that time, the industry generally believed that Kovio's fully printed RFID was likely to replace the mainstream silicon integrated circuit chip RFID.

Konarka Company in the United States was founded in 2001 and announced in 2008 the construction of a 1GW printed organic solar cell production line, becoming a star enterprise in the industrialization of printed electronics at that time. However, both companies later disappeared one after another due to their products failing to break into the market. Another example is Germany's PolyIC, which was among the first internationally to launch printed organic electronic labels and metal mesh grid transparent conductive films, but since its products failed to open up market sales, they turned to developing other technologies.

In the field of transparent conductive films, besides PolyIC, there are also many companies adopting coated nano-silver wires or carbon nanotubes that advocate printed electronics technology. Some of these companies have survived for over 10 years, but due to fierce market competition—especially the sharp price cuts of traditional ITO materials and their struggle to hold onto their original markets—most of these companies have seen lukewarm market performance, and some have completely withdrawn from the market, such as Carestream, an early company that strongly promoted nano silver wire transparent conductive films, and Cima, a self-assembled nano silver ink company Nanotech companies, among others.

Challenge

The concept of printed electronics is very appealing. When printing is mentioned, people naturally think of printed newspapers and magazines, and the advantages of mass-producing electronic products at low cost. However, to truly achieve printed electronics like newspapers, there are still many technical, industrial, and market-oriented challenges. First, printed electronics technology itself has limitations:

(1) The graphic resolution of printed processing is far lower than that of traditional micro-nano processing. Currently, the finest lines achievable by printing are about 1 micron, while the pattern sizes processed by integrated circuits have reached the 10-nanometer range.

(2) The prerequisite for printed electronics is the availability of printable electronic ink materials, but currently the types of such materials are limited and generally have lower performance than their solid counterparts. The printed electronic devices also perform lower than those produced by traditional micro-nano processing.

(3) Electronic devices usually require multilayer structures. Multilayer printing structures are limited by registration accuracy. The printing registration accuracy is usually far lower than the multilayer alignment accuracy of micro-nano processing.

(4) To restore the original material properties of printed electronic ink, curing and sintering processes are required. For some materials, the sintering temperature may be very high, limiting the selection range of substrate materials. Additionally, the properties of the sintered and cured material are usually difficult to restore to the original properties of the solid material, such as conductivity.

(5) Due to differences between printed electronic devices and traditional microelectronic devices, existing microelectronic design methods and software cannot be directly applied to printed electronics design.

The belief that traditional printing companies can directly switch to printed electronics, or that circuit boards can be manufactured using printing methods (note: traditional printed circuit boards and PCBs are not made by printing), are all misconceptions about printed electronics in traditional industries. The printing technology required for printed electronics is much more complex than that for newspapers, including the compatibility of electronic ink and the registration precision of multilayer electronic ink printing. Currently, the conductivity and precision of printed conductive inks have not yet reached the requirements of traditional PCBs.

The most attractive application of printed electronics, namely printed transistors, is still far from practical application. Currently, some products are developed using organic or inorganic semiconductor inks to prepare transistors, but most still rely on traditional processes such as lithography to achieve graphical transistor structures, and are not truly fully printed transistors. There are still many technical issues to resolve regarding stability and packaging for printed solar cell products.

Second, printed electronics must compete with traditional electronics in the market. Printed electronic products have their own product forms (flexible, plastic-based, paper-based), but they also have performance disadvantages. Take RFID tags as an example: traditional RFID chips are less than a millimeter square and can integrate tens of thousands of transistors. Printed RFID, apart from the printed antenna, can only print about a thousand transistors on a limited label area, so its performance naturally falls far short of RFID chips integrated with tens of thousands of transistors. Moreover, RFID chips as small as sesame seeds can also be installed on flexible RFID antennas to achieve flexible RFID tags. Therefore, the challenge facing the commercialization of printed electronics is how to create differentiated products that offer users new user experiences that can complement existing microelectronics technologies.

Printed electronics only gain an advantage in market competition by creating a revolutionary and unprecedented product or a cost-effective product. A successful case is the mixed-printed nano-silver metal grid transparent conductive film mass-produced by Nanchang OFILM. Because this new transparent conductive film for touchscreens is more conductive and sensitive than ITO transparent conductive film, and the manufacturing cost is lower, it can quickly open up the market. But this is only in the market for large touchscreens. In the mobile phone touchscreen field, due to the small screen size, the drawbacks of ITO high impedance are not obvious. Moreover, ITO suppliers face competition from non-ITO materials and have adopted significant price reduction strategies, making it extremely difficult for metal grid transparent conductive films to enter the mobile phone touchscreen market. It should be noted that the low-cost characteristic of printed electronics can only be realized through mass production. Printed electronics produced in small batches cannot achieve low cost. Therefore, if you don't produce in bulk, you may not have an advantage in market competition.