We are publishing a series of four articles over the next three weeks, highlighting the depth and breadth of innovation as well as existing and emerging applications in the field. This article includes more 65 individual images and charts showcasing various innovations, techniques, and products. You can see the table of content for this article below.
Table of Contents:
All the innovations highlighted in these articles are from companies presenting or exhibiting at our upcoming event on 11-12 May 2021 on Printed, Hybrid, Structural, and 3D Electronics. For a given trend, we often highlight just one or two firms, but our past (now available on-demand) and future (LIVE, online) events feature all the key players worldwide.
At TechBlick, each year we offer more than 350 hand-picked talks on emerging technologies including (1) printed, hybrid, and structural electronics and (2) advanced materials.
With a single annual pass, you can participate in all our LIVE events online, truly mingle and network with the community online, and participate in our masterclasses. See how our networking and virtual mingling works here.
We have assembled the best speaker line-up yet for our next LIVE conference on 11-12 May 2021, covering Printed, Hybrid, Structural, and 3D Electronics. Our programme features 65 speakers and and panelists including Coca Cola, P&G, Boeing, Airbus, HP, Signify, Texas Instruments, Panasonic, Parsons, ARM, Identiv, Wuerth, Phillips 66, US Army, Agfa and many more...
This programme is co-located with our LIVE (online) conference focusing on "Quantum Dots: Material Innovations & Commercial Applications". Here, the speakers include Shoie Electronic Materials, Emberion, IMEC, SWIR Systems, Avantama, UbiQD, etc.
You can see the full agenda here You can buy your annual pass for just 450 Euros per year using the 10% discount code 10%DiscountAA until 1 May 2021.
You can meet all our exhibitors at our show LIVE (see exhibitors below). They will be at their interactive virtual booths waiting for you to pop in. You can also hear all our speakers present and then follow up with them- as you would in a physical world- in highly-interactive networking lounge.
The Role of Printed Electronics
A hot trend in the display industry is micro-LEDs. These displays are fantastic, but they are difficult to manufacture. Mirco-LEDs come in a variety of forms (see below) and can be used in different types of displays, ranging from small sized and micro displays all the way to very large-sized displays.
The transfer process, as we shall see, is a major technical challenge and thus deservedly receive all the attention. One point that is often neglected though is how to metalize the actual substrates to connect the transferred micro LEDs?
PVD is often used. This approach is tried-and-test but is subtractive. Furthermore, a via needs to be drilled through the mother glass substrate and filled to create a front-to-back connection. Companies are now proposing the use of screen printing. A great example from Applied Materials is shown below. Here, the connection lines can be screen printed using silver pastes.
More importantly, the substrate can be robotically rotated so that the front-to-back conductive lines can also be printed on the edge of the substrate, thereby eliminating the need to drill and fill vias. Applied Materials is currently achieving a L/S (linewidth to spacing ratio) of 60/40 µm.
The transfer process in microLED display is a major challenge. This is partly because microLEDs are very small. The image below highlights this point, comparing the size of microLEDs against all manners of items.
To appreciate the scale of the transfer challenge, consider the chart below on the right. For an RGB microLED displays with three differently-colored LEDs, the main chart shows the number of failed dies for a given display resolution (number of transferred items) and transfer yield (example: a 4K display has 8,294,400 pixels and each pixel has 3 microLEDs thus the total LED number is some 24.8 Million).
As shown in the inset, we need yields exceeding 99.99% otherwise the display is compromised. This is of course extremely hard to achieve, especially on aggregate yield across the whole process including metallization, transfer, bonding and so on and so forth.
Digital Printing on 3D Surfaces With µ-Sized Features
Achieving such stringent targets likely require some precision post-transfer repair mechanism. Digital ultra-precision printing on 3D (or non-smooth) surfaces can offer a promising repair tool.
An example is shown below, by XTPL (Poland). They can digitally print few micrometer feature sizes using their own viscous silver nanoparticle ink. As can be seen in the image, in one example, they print 3.2 µm line with a spacing of just 0.7 µm. In the bottom right image, the printer is being applied to enable open defect repair in high resolution displays. This technology has an interesting performance positioning w.r.t to other additive printing processes such as inkjet, aerosol, electrohydrodynamic, and so on. In general, it exceeds the current resolution limits of inkjet and aerosol, and matches that of electrohydrodynamic but with a more viscous ink. This tool can be used in many applications including security printing, prototyping of redistribution layers, electronic packages, and many other applications.
The theme of ultrahigh-resolution printing is strongly covered in our upcoming conference on 11-12 May 2021. The past and confirmed upcoming presenters on this topic include Kodak, Optomec, Enjet, XTPL, Applied Materials, NanoOps, IDS, etc. With an Annual Pass you can of course access past content from all our previous conferences
Large-Area LED Lighting & Printed Alectronics
Printed electronics can play a role in large-area LED lighting in multiple ways. First consider the example on the left below (by Kundisch GmbH). Here, printed circuitry or metallization is used to power the LEDs. The primary advantage of printed LEDs is that one can create customized patterns, thus granting a high degree of design freedom. Note that the printing can also take place on flexible PET substrates. The soldering is likely done manually unless one of the below-described emerging technologies is deployed.
Furthermore, one can roll-to-roll (R2R) print the metallization and the component attach materials, and also R2R assemble the LEDs onto a flexible and conformable PET-like substrate. This can be an excellent production process for creating flexible conformable LED foils.
This process has been around for several years, but is now gathering steam and momentum. A good example is the R2R metallized and assembled LED lighting foil by Holst Centre shown below. Here, all the functional layers are R2R printed and the LEDs are R2R transferred.
Low Temperature Soldering for Flexible Hybrid Electronics
Flexible Hybrid Electronics (FHE) requires low temperature soldering. There are two primary and important motivations: (1) to be able to solder SMD or dies onto PET substrates, enabling a transition from expensive PI in FPBCS to low-cost PET, and (2) to enable automated soldering on PET substrates (currently soldering on PET is often done manually to accurately control temperature profile).
Multiple approaches have emerged, or are emerging, to enable this transition. NovaCentrix is proposing photo-sintering. Here, the joints are exposed to a short millisecond pulse of wide spectrum light to cause the solder to reflow. You can various examples of applications or close-ups of photo-sintered solders below.
In this arrangement, the printed thin films on the surface of the substrate experience elevated temperatures, but not the substrate itself, enabling soldering on PET and similar substrates. If the sintering profile is optimized, this process can take place in a matter of milliseconds, potentially making it compatible with R2R high-throughput processes, thus removing one of the major bottlenecks of R2R printed FHE production.
Several companies are also offering and/or developing low-temperature solders. Safi-Tech has developed SAC305 microcapsule solders that can be applied onto PET at just 120C. An example is shown below and the schematic on the bottom right describes the microcapsule concept. The great feature of solder – vs conductive adhesives- is the automatic self-alignment which lowers the burden of precision pick-and-place. Safi-Tech is a spin off from Iowa State University, which was the birthplace of SAC305.
Alpha Assembly is another great example. They have developed a sub-150C solder compatible with heat-stabilized PET. The chemistry is not disclosed, but it is likely SnIn based. The images below show an example of a circuit assembly on a flexible white PET substrate. The reflow temperature remains below 145C in this case. The project was a collaboration between Alpha Assembly, Sheldahl, and DuPont Teijin Films, and clearly highlights the possibilities that this technologies offers.
Of course, conductive adhesives remain a strong choice. The filler is often the main cost driver. We highlight one innovation here by CondAlign that can drive down filler content whilst not compromising performance such as z-axis conductivity. Here, CondAlign deploys electric fields to vertically align the particles to create anisotropic conductive films. The process is shown below in two snapshots taken during a real filler alignment process. CondAlign has now made production process R2R (see their machine below), whilst retaining sub-10 µm pitches in a wide range of film thickness (from a few to some hundreds of µm).
The theme of flexible hybrid electronics is strongly covered in our upcoming conference on 11-12 May 2021. The past and confirmed upcoming presenters on the topic include ARM, Identiv, Parsons, Smooth&Sharp, GE Research, Jabil, American Semiconductor, Texas Instruments, Panasonic, DuPoint Teijin Films, NovaCentrix, Alpha Assembly, CondAlign, Safi-Tech, CPI, Sheldahl, CEA, and more
3D Printed Electronics:Bringing Intelligence to 3D Surfaces
3D Printed Electronics is a very active area. One can divide it into two-sub areas: (1) electronics add to or near the surface of a 3D object, and (2) true 3D printed electronics combining classical 3D printing with printed electronics.
The top row below shows examples of the first approach. Here, we can see 3D shaped antennas, heaters, lighting and HMIs, and even a medical device. The second row shows examples of the second approach. Here, the conductive lines as well as the SMD are embedded within the 3D structure of a complex 3D shape which is built up layer-by-layer using classical 3D printing.
This approach allows one to really bring intelligence to 3D printing. Thus, instead of just creating dump mechanical objects, one could integrate also the electronics inside the 3D printed object. If one puts in place a seamless design-to-production process, it could open many fantastic opportunities.
This is a major theme of our upcoming conference on Printed, Hybrid, Structural, and 3D Electronics conference on 11-12 May 2021. The past (now available on-demand) and upcoming speakers on this topic include HP, Signify, Wuerth, Neotech, NanoDimension, LPKF, and others.
3D Smart Surfaces
3D shaped smart surfaces are on exciting theme. The applications range from metallization of 3D surfaces at antenna or electronic package level to large-sized interior or exterior automotive parts. In the image below, we highlight various examples of large-sized 3D-shaped smart surfaces aimed at vehicle interiors. The underlying technologies highlighted below are diverse, including stretchable sensors, electronic textiles, transfer molding, and in-mold electronics.
Of particular interest are the in-mold electronics (IME) technique and other similar technologies. These technologies typically have a functional layer composed of multiple printed layers. The functional film then somehow 3D formed and in some cases overmolded.
Here you can see two examples of InMold Electronics (or structural electronics) which I wish to highlight. The one on the left is a prototype by Greely. Here, the seat adjustor is transitioned from a classical to an IME design, reducing parts from 45 to 1, tools to 20 to 2, weight from 185g to 25g, and thickness from 38mm to 3mm. The latter is an important figure-of-merit because it opens space for other functionalities.
The image on the right is an example from Suunto. Here, the smart connector is made using IME. The process steps are shown below. The design passed design verification requirements including -20-to-60C operating temperature, 50 machine cycles @40C, 5000 30-degree twists and 90-degree flexes, heat press, and so on.
The smart layer here was simple including only a simple memory and a resistance plus various conducive lines. However, the complexity of IME technology will in time rise. Of particular interest will be the integration of lighting components.
This is a major theme of our upcoming conference on Printed, Hybrid, Structural, and 3D Electronics conference on 11-12 May 2021. The past (now available on-demand) and upcoming speakers on this topic include Geely, FIAT, Suunto, LightWorks GmbH, Arburg, DuPont, PolyIC, TactoTek, Kimoto, etc.
Skin Patches & Medical Electronics
A hot area in printed flexible electronics is in medical electrodes and there are many applications.
Electronic skin patches for continuous health care monitoring has become extremely hot as we transition from a standard blood-based glucose sampling to continuous glucose monitoring and to all types of continuous vital signs monitoring, e.g., heart rate monitoring etc. Continuous vital signs monitoring is a multi-billion-dollar market already.
Printing can really play a role here. The example I want to highlight here is the development by Holst Center who have developed a full solution. This is a clinical grade disposable patch with reusable electronics, with a dry electrode, etc. The dry electrode includes printed metallization allowing one to measure EKG, respiration, and temperature.
Another highlighted example (right image below) is from Screentec Oy. Here one can see a medical electrode with integrated SMTs on the top. And the bottom right picture is an example of a screen printed sensor which can detect skeletal muscle activities.
You can also see an example by Jabil, one of the largest contract manufacturers worldwide. Here, the actual measurement electronics can be printed using Ag/AgCl electrodes on the back side of the PCB. Printing allows one more freedom in where the electrodes are placed.
Medical Electrodes: R2R Volume Screen Printing
Printing of medical electronics is in fact already a major business. The example below is from Mekprint (Denmark). The example you see on the right below is a R2R screen printed ECG electrode. And this application has a volume sale of more than one hundred million units per year.
Another highlighted example on the left below is an incontinence sensor. It is again R2R screen printed. Interestingly, here conductive cable lines are actually R2R printed on a stretchable non-woven material. This too is a commercial application. Here too, the printed sensor is part of a full solution, including the rigid electronics, the communications and so on and so forth.
In general, printed electronics is playing a major role in electronic skin patches, medical electrodes, and similar fields. It is already a success story.
Stretchable Conductive Inks for E-Textiles
The overlap between electronic textiles and the printed electronics is often the printing of the interconnects or the printing of the stretch sensors.
In the early days, maybe four or five years ago, companies started to bring out the first generation of conductive stretchable inks. There has been much progress since on improving the performance of these inks.
Today, companies are not just offering stretchable conductive inks, but they are offering the full portfolio of stretchable inks needed to create an electronic textiles. This includes the stretchable silver inks, the carbon inks, the dielectric ink, the conductive adhesive, and so on.
The highlighted example in this newsletter is from Nagase. Here, the silver ink can be stretched by 100 percent. The chat in the middle shows the properties of the stretchable conductive adhesive, which can be stretched up to 30 percent with very little hysteresis. The adhesive can be cured at 180C.
The chart on the bottom right shows that a full stack is needed to improve washability. Here, the resistivity of a line made out of printed Ag alone is lower, but the stacked version (silver + carbon + dielectric) offer more washability. Here, the stacked version experiences little performance changes after 100 washing cycles- an important milestone for e-textiles.
We have a full conference dedicated to Skin Patches, E-Textiles, and Stretchable Electronics in early Sept as part of the TechBlick series. We will bring you all the key end users, manufacturers, and material innovators. If you sign up for an Annual Pass you will also have access to that upcoming events.