What's the Alternative to Screen Printing for Printed Electronics

The term printed electronics consists of several different electronic devices or applications with different characteristics, such as thickness and resolution. Therefore, it is not possible that just one single printing technology could replace all printed electronic devices and applications.

Since screen printing is the most popular technique for manufacturing printed electronics, specifying and analyzing screen printed characteristics in more detail could reduce the number of alternatives to this method. After assigning special characteristics to a typical screen printing application manufactured in large quantities, the number of alternative print techniques gets even smaller.

This question, however, can only be answered after thoroughly analyzing the content of the printed electronics collection. To start, we must examine the nature and function of printed electronics.

Printed electronics are a collection of different electronic applications, with each application or device manufactured using its optimal print technique. Printed electronics belong to the group of functionally printed electronic devices, which are part of the current industrial screen printing group.

Industrial Screen Printing

Industrial screen printed applications or products are mostly functional applications with screen printing being an essential part or technology of the overall production process. These print companies are hard to find since screen printing is only used to manufacture a product’s technical function.  In most cases, the printer’s name does not appear on the company’s façade.

In contrast to decorative applications, which are only confirmed visually, a functional application’s function is controllable and measurable (e.g., an on/off switch, reaction time, voltage, magnetization, security effect).

Printed Electronics Characteristics

The characteristics of printed electronics manufactured by screen printing are resolution, scalability, versatility, measurability and uniqueness.

Uniqueness

With the ability to deposit an average wet ink deposit of 10-30 microns at a reasonable speed, screen printing is unlike any other imaging technique.

Controllability

Repeatability is a critical factor in screen printing’s growth in industrial applications. Manufacturers can control various parameters for consistent results and test the printed deposit to monitor quality and build the statistical process control data that is often a requirement in this field.

In its market research, IDTechEx projected a global forecast of approximately $50 billion for printed electronic applications for 2020. In other words, this randomly determined application is a more than lucrative market.

Resolution

According to 2014 IDTechEx market research, screen printing allows for printing under production conditions with a commercial line width of approximately 40 microns, and 30 microns line width under laboratory conditions (approximately 2%). Therefore, screen printing was predominantly used for printed electronic applications (approximately 98%) while inkjet was partly used for commercial purposes. At that time, gravure was a serious subject for development and offset was apparently too slow to print comparable deposits at a reasonable speed.

Measurability

Immediately following printing and drying, the characteristics of the printed deposit can be measured to obtain a clear impression of the performance, such as electrical conductivity, resistivity, voltage, magnetization or peel strength of two adhered materials.

Scalability

This characteristic means that screen printing allows for manufacturing large quantities of the printed electronics product against an interesting cost price. Scalability is an important characteristic in any manufacturing environment for decreasing the cost per unit for the required output.

Together, these characteristics represent screen printing’s unique selling propositions in the field of functional industrial applications. It also makes screen printing the perfect match for manufacturing printed electronics as forecasts predict the market’s potential, which will be almost twice the current size by the year 2026 ($70 billion).

Printed electronics forecast by print technology. Information courtesy of IDTechEx.

Versatility

Screen printing can easily be adapted for many requirements and needs. Production setups range from manual to fully automatic. Devices can be screen printed with traditional inks, such as UV-curable, solvent- or water-based, in addition to different types of adhesives and pastes.

The availability of substrates is almost unlimited.

Comparing Alternatives

The possible alternatives to screen printed electronics may be manufactured using different print technologies. Each print technology (inkjet, flexo, offset and gravure) features its own characteristics, advantages and disadvantages.

Printed electronics is a collection of different electronic applications. Offset, flexo, gravure and screen printing belong to the conventional print group, which means they all require a print master or a print form.

Screen Printing

As previously noted, screen printing is an established technology for printed electronic applications and currently dominates this market. The ink deposit, printed with a screen, is rather thick (10-20 microns), but the resolution is low.

Inkjet

Since 2014, inkjet solutions for printed electronics have been in development. Inkjet is a digital process that propels droplets of ink on a substrate and produces prints without needing the preparation of a print master. In one pass, it’s possible to produce thin layers with a moderate resolution (50 microns).

The most common inkjet technologies are drop on demand (DOD) and continuous. DOD can be further classified as piezo, thermal or electrostatic inkjet. Thermal inkjet, however, can lead to degradation of functional materials, and is not sufficient for printed electronics.

Inkjet printing has been successful in printing passive components and OLEDS, and its inks are commercially available.

Flexo

Though it produces sufficient resolution, flexo is rather slow. However, the efficient and fast roll-to-roll print technique has accelerated flexo’s use for printed electronics.

Gravure

In this method, the image is applied to the substrate by a metal plate mounted on a cylinder. The inked image is transferred by depressing the metal plate by etching it into the metal surface. Gravure printing produces high quality and high resolution (20 microns) with high speed.

When it comes to smaller production jobs, however, the cost per item is significantly higher than other printing methods.

Slowly transitioning from the research and development to the pilot phase, there is a strong focus on high-volume flexo and high-volume gravure.

Offset

In offset printing, the image is transferred from a plate via a rubber blanket to the substrate.

Though the image quality is inferior, offset has a high speed, high resolution  (≤ 20 microns) and a thin deposit. Low costs are associated with press setup and preparing print plates.

The special inks required for offset contain electronic materials, such as nanomaterials and conductive, resistive and dielectric materials.

Conclusion

To summarize:

• Printed electronics is a collection of electronic applications that are manufactured under different conditions. No single method can replace screen printing; alternatives depend on the characteristics, requirements and costs.
• For now, through the near future, screen printing dominates the printed electronics market.
• 2014 saw the development of electronic devices printed by inkjet. Without a print master, this technology has serious opportunities to replace screen printing. It may become commercial over the next two years.
• Gravure and flexo could also simultaneously join the printed electronics market, but their development started later than inkjet due to a small backlog. With their characteristics, gravure and flexo are perfect alternatives for inkjet printing to replace the screen. Depending on the cost development, these methods are major competitors for mass-production runs.