Printing and vacuum technologies competing for market share in the flexible electronics sector
Printing technologies have been the dominant force in the growing flexible electronics market, but vacuum technologies are becoming more cost-effective and have some distinct advantages.
Flexible electronic devices are starting to experience significant proliferation, with more and more devices with innovative form factors being brought to market, from small components such as disposable sensors to flexible smart phones by consumer electronics giants like Samsung and LG.
While printing technologies enable lower manufacturing costs and superior performance in many applications, vacuum deposition still claims significant market share in flexible electronics. In some cases, a combination of printing technologies and vacuum deposition can be the ideal combination.
From test strips to OLEDs
Glucose test strips are an example of the prevalence of both printed and vacuum deposited devices. Over ten billion test strips are being manufactured worldwide, in order to cater for the needs of the ever-increasing number of people living with diabetes. Although each manufacturer/brand has its own technology and design, the following cross-section shows the key parts of a test strip. Manufacturers follow both thick film (screen printing) and thin film (sputtering) techniques for depositing the circuit in test strips.
Screen printing technology involves printing patterns of conductors and insulators onto the surface of planar solid (plastic or ceramic) substrates based on pressing the corresponding inks through a patterned mask. Each strip contains printed working and reference electrodes with the working one coated with the necessary reagents and membranes, with the reagents commonly dispensed by ink jet printing technology and deposited in the dry form. With thin film deposited electrodes, sputtering or laser ablation is commonly utilized.
Along with the very specialized organic materials utilized in assays in the actively sensing part of the test strips, advanced devices integrating thin film technology utilize gold nanoparticles and mesoporous Pt electrodes, and even the use of carbon nanotubes and graphene has been demonstrated in certain designs.
Organic light-emitting diode (OLED) displays are a good example where the advent of printing techniques is meant to bring about much larger displays that are manufactured at lower costs. For the time being, however, the OLED industry makes displays that are almost exclusively vacuum evaporated because they perform better. Most of these companies are active in making more than just the active OLED layers and are providing equipment for thin-film transitor (TFT) deposition, encapsulation, etc.
The opportunity here is significant: The OLED market is projected to reach over $50 billion in the next decade, with flexible and rigid plastic OLED displays alone surpassing $16 billion by 2020.
Flexible encapsulation & thin film PV
Encapsulating flexible versions of OLED displays is set to become an exciting market: flexible barrier films—whether utilizing chemical vapor disposition (CVD) or physical vapor disposition (PVD) processes or even in cases when atomic layer disposition (ALD) is utilized to make high quality, defect free layers—are benefiting from vacuum deposition techniques. These companies have created encapsulation materials that are designed to reach the water vapor transmission rates required to allow flexible OLED displays the necessary lifetimes required to become commercially viable. Encapsulation for flexible OLED devices is a market that is expected to reach almost $340m by 2022 according to IDTechEx Research in the report "Barrier Layers for Flexible Electronics 2016-2026: Technologies, Markets, Forecasts."
Flexible versions of thin film photovoltaics also require stringent encapsulation, but thin films have had harsh competition from low cost crystalline silicon cells from China, that have significantly reduced their market share in recent years. Just over 7% of the overall market for PV this year is expected to be thin-film based, according to research from SPV Research.
Manufacturing of all thin films for solar cell applications is vacuum-based: PECVD for amorphous silicon platforms, sputtering or co-evaporation tends to be the preferred deposition techniques for CIGS technologies while CdTe leader First Solar has developed and optimized its own unique vacuum deposition technique, high rate vapor transport deposition (HRVTD).
Commercializing flexible or printed electronics will invariably require a deeper understanding of vacuum deposition technologies. Printing techniques are not the only manufacturing option that can allow for the freedom in design that the advent of flexibility in form factor is ushering in. In fact, vacuum deposition technologies are currently enabling the proliferation of a wide range of components and devices, from encapsulation films to thin flexible batteries to transparent conductive films and backplane elements. In many cases, having reached economies of scale, vacuum deposited devices have reached attractive cost structures that make it harder for printed versions to compete.
– Dr. Harry Zervos is principal analyst, IDTechEx. Edited by Chris Vavra, production editor, Control Engineering, CFE Media, firstname.lastname@example.org.
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