Flexible hybrid electronics (FHE) is a novel approach to electronic circuit manufacturing that aims to combine the best of printed and conventional electronics. FHE is today considered as the future of flexible printed electronics.
Conventional electronics manufacturing
Conventional electronic manufacturing consists of silicone micromachining by lithography methods such as micro-contact printing[1], laminar flow patterning[2], nano-imprint lithography[3], dip-pen lithography[4]. Lithography implies many steps such as chemical treatment, growth of silicone oxide across the tape surface, application of photoresist by spin coating, photo-exposure, negative development, and baking. Lithography is an expensive, complex, and time-consuming process. The process is limited by tape size and does not allow the use of different substrates. In addition, the conventional process causes environmental problems because of acid use, heavy metal wastes and adding of dangerous solvents in photoresist developers. Very thin films, 0.1–2.0 µm thickness, can be deposited by lithography. This is an advantage in microelectronic applications due to the miniaturization tendency[5],[6]. Laser direct writing processes were introduced as an alternative to lithography methods. These processes allow direct transfer of material from a source film to a substrate by laser induction. Extremely high resolution, 1–3 µm, may be reached by these methods[7],[8].
Printed electronics
Printing processes are known since the 1950s as an alternative method to deposit conductive tracks on flexible or rigid substrates. They were established as a cost-effective way for creating thin and thick conductor films (0.2–20.0 µm). Using printing techniques to manufacture electronic devices has many advantages[9]:
Performance latitude and reliability,
Fast methods,
Low cost,
Possibility of high and low volume production,
Less waste and environmentally friendly,
Adaptation to different types of substrates depending on the printing process (rigid or flexible tapes),
Multilayer applications,
Accurate registration,
Manufacturing of hybrid electronic circuits containing resistors, dielectrics, and conductors, mainly with multilayer technologies,
Open to a large panel of electronic applications such as organic light emitting diodes (OLED), photovoltaic, radio frequency identification tags (RFID), display, conductive transparent electrodes, sensors, batteries, and microwave components.
For more information on Printed Electronics, check our post about this topic here.
Flexible Hybrid Electronics (FHE)
While printed electronics show multiple advantages, the use of conventional electronics is still a must thanks to its high processibility, and high achieved resolutions (sub-1 µm range) compared to printed electronics.
Flexible hybrid electronics (FHE) is a novel approach to electronic circuit manufacturing that aims to combine the best of printed and conventional electronics. FHE is today considered as the future of flexible printed electronics.
On one side, conductive interconnect, and as many additional components as possible, are printed onto a flexible substrate (using functional inks). On the other side, integrated circuit (IC) are produced with conventional methods such as photolithography and then mounted/placed.
This hybrid component provides the flexibility associated with printed electronics, but with the processing capability of a conventional integrated circuit[10].
In FHE, sensors, circuits, RFID, and displays can be processed by printed electronics. And, amplifiers, digital converters and signal processing systems are usually processed by conventional methods.
Flexible Hybrid Electronics (FHE) advantages
As mentioned above, FHE combines traditional integrated circuits with flexible printed electronics. On one hand, traditional manufacturing (such as silicon integrated circuits) succeeds at producing high-performance electronics. However, creating flexible and large-area electronics using silicon technologies remains a challenge. On the other hand, flexible and printed electronics use flexible materials (polymers, papers, etc.) and printing techniques to manufacture large-area electronics. However, printed electronics lack of performance compared to silicon-based electronics[11].
That is why, FHE brings the best of both technologies and offers to the electronics of today multiple advantages such as[12]:
Eco-friendly manufacturing methods thanks to the use - whenever possible - of additive printing technologies generating less wastes compared to conventional technologies,
High throughput and fast prototyping/manufacturing,
High-performance,
Production of large-area electronic system,
Manufacturing electronic on flexible and/or stretchable substrates thus allowing the production of flexible and conformable electronics,
Lightweight electronics,
And cost effectiveness.
Flexible Hybrid Electronics (FHE) applications
FHE is adapted for various types of applications where flexibility, stretchability and fast/high scalability are needed [11],[13]:
Wearable applications for health monitoring: monitoring of glucose, enzymes, hormones, blood pressure, temperature, etc.
Industrial and environment monitoring: temperature, humidity, gases and volatile organic components (VOCs), oxygen, ammonia, etc.
Sensors integrated in automotive and aerospace applications: corrosion, wind, strain, temperature, etc.
Large area energy harvester.
Communication: large-dimension antennas and inductors.
Conclusion
To conclude, FHE is a novel approach to electronic manufacturing allowing to benefit from the advantages of both printed and conventional electronics. It combines flexibility, ease of large area manufacturing with high performance and precision electronics.
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References
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[2] L. Gonzalez-Macia, A. Morrin, M.R. Smyth, A.J. Killard, Royal Society of Chemistry – Analyst 135 (2010) 845–867
[3]S.Y. Chou, P.R. Krauss, P.J. Renstrom, Applied Physics Letters 67 (1998) 3114–3116
[4]R.D. Piner, J. Zhu, F. Xu, S. Hong, C.A. Mirkin, Science 283 (1999) 661–663
[5]A. Karwa, Printing studies with conductive inks and exploration of new conducting polymer compositions, PhD Thesis, Rochester Institute of Technology, New York, 2006
[6] The future of flexography and lithography in printed electronics NanoMarkets LC © 2007, 804-360-22967, www.nanomarkets.net
[7]C.B. Arnold, P. Serra, A. Piqué, MRS Bulletin 32 (2007) 23–31
[8]N.R. Schiele, D.T. Corr, Y. Huang, N. Abdul Raof, Y. Xie, D.B. Chrisey, Biofabrication 2 (2010) 1–14
[9]R. Faddoul et al. / Materials Science and Engineering B 177 (2012) 1053– 1066
[10]https://www.idtechex.com/en/research-article/flexible-hybrid-electronics-future-of-flexible-printed-circuit-boards/20603
[11] Y. Khan, A. Thielens, S. Muin, J. Ting, C. Baumbauer, and A. C. Arias. Adv. Mater. 2019, 1905279
[12] Z. Li, S. Chang, S. Khuje, and S. Ren. ACS Nano 2021, 15, 4, 6211–6232, 2021
[13] G. Tong, Z. Jia, and J. chang. IEEE International Symposium on Circuits and Systems (ISCAS). pp. 1-5, 2018.