Printed Electronics a Technology of the Past and Future

Printed electronics (PE) is a new, rapidly growing interconnect business. It has its origin in printed-flexible keyboards for appliances and for the expanding technologies in fancy magazines and literature. The irony of PE is that the technology was probably the first employed during WWII and all printed circuits owes it origin to PE.

APPLICATIONS

The most exciting thing about PE is all the new applications and markets that it will open. In Figure 1 is just ten of the markets currently being pursued by PE developers. For a majority of these market, the applications are short lived and the actual PE substrates may be disposable. Some applications have been established like flexible keyboards, printed glucose sensors and printed RFID tags. Others like cosmetic wrinkle-cream masks powered by printed batteries and electrophoretic electrolytes are not even on this list.

MATERIALS

Materials continues to be the major challenge to PE developers. Since many PE applications are cost sensitive, the current conductive inks of silver and insulators of polyimide films are to expensive for their applications. The current insulators as candidates are seen in Table 1 and conductors in Table 2.

Research seems to favor nano-technologies of glass, plasticized-paper and PET as substrates and copper, graphite/graphene and carbon nano-tubes (CNT) as conductors.

TABLE 2: Conductive materials and inks suitable for PE

MANUFACTURING PROCESSES

Printed Electronics harkens to low-cost printing like magazines. That technology is one of our oldest and most automated. But other printing technologies are shown in Figure 2.

The various methods of printing inks are characterized as a function of its resolution (in microns) and throughput in square meters per second.          

A more detailed table of printing is shown in Table 3. It lists speed, resolution, film thickness (in microns) and viscosity of inks it can use.

DESIGN TOOLS

If you have upgraded to Altium Designer^® 19, you may have noticed that it has the capability of designing Printed Electronics. This is fortunate, because a lot of ideas and innovative electronics may take the form of a printed electronic substrate. 3D printing can now make printed electronics using silver pastes and various insulators, resistive and capacitive inks. Soon will be available semiconductor  (P & N type) inks as well as OLED pastes. As the technology becomes more popular, other special inks will be developed as well as improved substrates similar to paper.

For a comprehensive and thorough explanation of printed electronics, download and read my Chapter 11: Printed Electronics, pp. 380-444 in Joseph Fjelstad’s eBook: Flexible Circuit Technology-Fourth Edition at www.iconnect007.com

FIGURE 2. Nine methods of high speed printing as a function of their resolution

TABLE 3. More details on the characteristics of high-speed printing available today with indication of the viscosity range of inks that it can employ

REFERENCES:

1. Organic and Printed Electronics Association, OPE journal, 1-2007, www.ope-journal.com