This article delves into the fundamentals of EMI gaskets, types, and their critical role in protecting electronic devices and ensuring optimal performance in various engineering applications.

EMI Gaskets: The Unsung Heroes of Electromagnetic Interference Shielding

This article delves into the various types of printed circuit boards, their fundamental concepts, structures, manufacturing processes, and advanced PCB technologies, highlighting their advantages, limitations, and typical applications.

Types of Printed Circuit Boards: A Comprehensive Guide

Is there anything better than a good cup of coffee? It's devine when it's hot, and deliciously refreshing when it's iced.&nbsp;…But room-temperature coffee? Not so great.&nbsp;For most adults around the world, brewing a hot cup of coffee is an established part of our morning routine. But when you have a busy day, it’s easy to get preoccupied and neglect your coffee until it cools to an unpleasant temperature.Duru Uluk, a Voltera test engineering intern, set out to find a solution to this problem. Her goal was to create an induction mug heater using in-mold electronics (also known as in-mold structural electronics).In-mold electronics (IME) processes involve printing conductive inks on moldable plastic films, which are then formed into a desired 3D shape. In the full IME process, after thermoforming, the part is passed along to injection molding, where it is molded in plastic and the electronics become part of the entire structure.&nbsp;In IME, the electronics are printed using a standard process of screen-printing traces onto thermoformable plastics, but new innovative materials — like specially formulated functional inks optimized for high single-stretch operation — allow the traces to stretch into the new thermoformed shape and maintain conductivity.&nbsp;This technology is particularly exciting for automotive and aerospace applications, where thousands of feet of copper wire could be replaced with conductive traces integrated directly into the vehicle’s panels to reduce the vehicle’s weight and improve efficiency. Incorporating IME into vehicle construction also presents opportunities for new design concepts, features, and functionality — like the ability to incorporate strain sensors directly into panels to monitor for damage, interactive surfaces in the interior vehicle panels, or to heat and de-ice the wing of an airplane during flight.&nbsp;In the image below, all the red components identify the wire in a vehicle:<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1712283732859-63b49367152a021e60088642_3ZoHWv-Zic4V11X_3xOkWv831wmyc-hbLHIuslxurYTiXj6bsTy7zNxC97dVW-rYkGLgtJeYYhR5KCm91dpma-EpW2wOgcFG4d_InqrlcJFlFDp3zdS57GulmRe_iM-7DsUkP7ZUhs4RA1FXQ5HbMhmn9_Hgoqkd0BlsUhtZOuHgArS5v-Nn0GG6gaZX3.png" style="width: 100%px;" class="fr-fic fr-dib"><ul id="isPasted"><li>One vehicle has 5000 feet of wires = 50 lbs of copper.</li><li>Transporting 50 lbs burns 12 L of gas per year.</li><li>70,000,000 new cars produced per year.</li><li>840,000,000 L of gas is burned to transport copper cables per year.</li></ul>‍In addition to this example of copper wire, IME offers plenty of other opportunities to reduce the mass of many vehicle components, like the headlight assembly, dashboard, center console, and more.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1712283763549-63b49367f5596f24c741daec_4ZpHDUtkWx5wmeYtb6X6YjGlsuiVxdPXJ3H64MFHHtiDpTG1Bil6Mat9evncEvLP-DsCX7T2TC63nZtB5DzKQI8Vs98V-vE0R6e3Xbh6oy2iLiPHV6t7InCwE-C3-Mv_9XaLvGjKOrAfnppvIszjmAkMSYyGpSKIKpmn1A621NCHPe04dRGFy75i-Om81.png" style="width: 100%px;" class="fr-fic fr-dib"><a href="https://www.idtechex.com/en/research-article/what-does-2023-hold-for-printed-flexible-electronics/28172" target="_blank" id="isPasted">IDTechEx</a> anticipates the mainstream adoption of in-mold electronics in automotive interiors to begin in 2023, and is forecasting that electronics will be printed onto 3D surfaces, like door panels, in 2026.&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1712283778550-63b49367684ec45971bc70ac_9Gf654z1WMdopCZ5ZMfeK0mO-ZCYnQ1bpkpRVMCY4A4crd2KzqLzh6pao8OoT3ACsO7xnDTdqSfhdTUkRLs-flCOWGlTTjWUHQElpJ__YKFBoiHltw43eQPxsSzSt6DFJUnZ7ONaolf9Fv32CugpbDAMtWnRMf7bRfl-XDBMCBhXX--1QKBBwFR8jUAWd.png" style="width: 100%px;" class="fr-fic fr-dib">Roadmap for selected emerging printed/flexible electronics technologies. Source: IDTechExBut let’s get back to Duru’s coffee conundrum.&nbsp;Using&nbsp;<a href="http://voltera.io/nova" target="_blank">NOVA</a>, a&nbsp;<a href="https://mayku.me/formbox" target="_blank">Mayku Formbox</a>, and a&nbsp;<a href="https://formlabs.com/3d-printers/form-2/" target="_blank">Formlabs 3D printer</a>, Duru designed and built a mug heater with in-mold electronics technology.&nbsp;“During my co-op term at Voltera, Matt (Ewertowski, Product Manager) was my supervisor and also just a super cool person to talk to. We had conversations about different applications of NOVA and how flexible substrates open doors to a lot of different project ideas,” Duru recalled. “He suggested the idea of using the Mayku Formbox alongside NOVA for an in-mold electronics project. I did some research about making molds, molded electronic applications, and coil heaters — and from there it seemed feasible enough to continue with a demo.”&nbsp;So, Duru got to work. First, she used the Formlabs Form 2 3D printer to create a resin mold, and then used NOVA to print traces onto the Mayku Formbox substrates. Finding the optimal baking temperature for the Mayku substrates was a bit of a challenge, since they aren’t intended for IME, but with some experimentation and a bit of help from Mayku, she eventually found the right temperature and baking time to avoid substrate deformation. Once the curing temperature was refined, Duru encountered trace breakage during the forming process. Through some trial and error, Duru refined the design of the mold and the traces until she was successful in creating a design that could be thermoformed and maintain conductivity.&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1712283802120-63b49367bedfeccaa9cf2122_18Qk-iwOjIp00g_snsqEE-x33qu6yTIyGZgI7LuwCgRcaZM_MqpFYbKCYiJuFZBouwEXx12yQES8yTL8EyCsHTZdx9tJe3hHoxa_25BT4I0v1AKIbJnATzxzcMlx7Sax3lK_uGQrK_F9idp-Fxa-5rsh0MAJA5HS_IV8y-YJOUrY7bGJacjQY-0kMgNi_.png" style="width: 100%px;" class="fr-fic fr-dib">“It took several iterations to achieve a design that ensured a fully conductive trace with no breaks. When the baked print goes into the Mayku Formbox, the substrate is being heated and deformed,” she explained. “There are so many factors to consider. Will the conductive ink be damaged? Will the substrate be damaged? That required a lot of correspondence with people to get information about melting points and what not, including <a href="https://insulectro.com/" target="_blank" id="isPasted">Insulectro</a>, who supplied us with the ink — they really helped out. But the biggest issue was of course the sharp angle of the mold, causing the trace to be deformed to a point where it is no longer conductive. And that’s why I had to gradually reduce that angle and on the trace edges.”&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1712283815611-63b493679710e828f9389688_waXyaVYzojKJhCnZk3L-4449I7fgizrTBOeX5J_OFFrewsSraWdgajH_SZWHidk2TmHiCQQyixG-GXwRC5MjWiTqBm1HuSU0SPIVCTu_nf4hCdQgQfHpeLhQ5nWupJ7h9OA6rmDnQfC3-dykkJzPrYl_hx-uljy8UhHay90NQDdw1DOL--90k-rxEUl0.jpeg" style="width: 100%px;" class="fr-fic fr-dib">Despite the challenges of the project, Duru loved working with <a href="https://www.youtube.com/watch?v=T62cUY8uj8M" target="_blank" id="isPasted">NOVA</a>. “Everyday I was excited to use the NOVA just because of how cool it is. The user interface is super easy to use, the modular design and the way everything magnetically clicked into place, the sounds, the lights, etc.” she noted. “I also love NOVA’s ability to work with various substrates. I worked a lot with flexible substrates during my time at Voltera, so the vacuum feature was being used frequently.”<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1712283834936-63b4936799db03ad4a1aacaf_ZS6BCi4fHe5wPMhX5X845YVFQK8foJ0C90XCCX2Q0EIZFQ_TL2AX2fVH2gvyMzbL3mfu1mFjlED5rciLDX-kYKeIIYwMn4lQYjsoLvpLbzf2P3dVsHL8YTW0Qjss0gFxsrC5DuwivgbeDPpdGys4vfyDzQ2fmShgr4FPqtWeknJUgW3gxonzz5EeLXoV.jpeg" style="width: 100%px;" class="fr-fic fr-dib">In Duru’s eyes, there are so many exciting applications for the technology. “In biomedical applications, for example, you could use in-mold electronics to build medical tools or prosthetics that are ergonomic and accessible, with electronic components integrated through in-mold processes — to easily incorporate electronics into things that have awkward shapes, or have been challenging to design using traditional methods. And in cases like these, being able to use NOVA to build electronics that fit a specific, custom shape may be a great advantage.”&nbsp;The experience of working with NOVA was inspiring for Duru, and piqued her interest in electronics innovation. “During my time working with NOVA I gained a big interest in additive electronics and learned a foundation of knowledge (about conductive inks, substrates, rheology) that I still bring up at every chance I get,” she said. “I also got inspired to tinker more. Having access to benchtop tools like the NOVA would enable people to tinker freely and try new things — which is beneficial to the engineering iteration process.”&nbsp;Working at Voltera also impacted Duru’s career aspirations. “Many of my co-op placements have been R&amp;D specific. During my future career I think I’d like to work in spaces where I have access to tools like NOVA while doing R&amp;D work and product development. My perspective has shifted to appreciate the potential of additive electronics in&nbsp;<a href="https://www.researchgate.net/publication/361717600_Inkjet_and_Extrusion_Printed_Silver_Biomedical_Tattoo_Electrodes" target="_blank">biomedical applications</a> — for example the&nbsp;<a href="https://uploads-ssl.webflow.com/6334888a34bfac03b46aa715/633c55566e5bffe8db61ba27_NOVA-0082%20-%20Insole%20Case%20Study_v2.pdf" target="_blank" data-lf-fd-inspected-kn9eq4roawkarlvp="true">in-sole pressure sensor</a> project I did, or things like wearable biomarker sensors.”And now, thanks to her in-mold mug heater, Duru can iterate for hours and never have to worry about her coffee getting cold.&nbsp;

Duru Uluk, a Voltera test engineering intern, created an induction mug heater using in-mold electronics (also known as in-mold structural electronics).

Warming Your Coffee with In-Mold Structural Electronics

Mike Simmons, Matthew Kleyn, Joseph Vlach, Liz Josephson; Intellivation LLCThe demand for high-performance devices with enhanced functionalities continues to grow. Materials, such as graphene and MoS2, exhibit unique electrical and mechanical properties making them ideal for flexible electronic applications. To meet the rising demand and requirements for flexible 2D microelectronics devices manufactured using Roll to Roll technology, we use innovative manufacturing techniques including vacuum coatings in combination with laser technology. Laser patterning of sputtered coatings provides the ability to achieve high-volume production with precision, functionality and efficiency for a wide range of flexible applications.Sputter deposition is a widely used technique for depositing thin films onto substrates. For flexible 2D microelectronics, sputtered coatings serve as the foundation for building functional devices. Sputtering involves bombarding a target material with ions to eject atoms or molecules, which then deposit onto a substrate to form a thin film. This process allows for precise control over the thickness and composition of the deposited film, making it a preferred method for creating uniform and reproducible coatings. &nbsp;Sputtered layers were deposited using Intellivation’s R2R Lab system. Sputtering provides an excellent method for depositing coatings uniformly over large areas, while laser patterning can create discrete devices, circuits, and other types of discontinuous features required for manufacturing. &nbsp;Using these two techniques in combination provides unique capabilities, particular during product development. &nbsp; Photolithography requires multiple steps and is time consuming, it also requires geometric commitment of features at early stage of design. &nbsp;Laser patterning offers a direct and efficient way to create and define patterns on sputtered coatings including changes in geometry while providing consistent feature size and edge quality.Laser patterning uses a laser beam to selectively remove or modify specific areas of deposited films enabling the generation of intricate patterns with submicron-level precision. &nbsp;Control and precision of the laser is critical and the non-contact nature of laser patterning reduces the risk of contamination and damage to the underlying substrate, ideal for delicate 2D materials. &nbsp;This technique provides the ability to develop and then validate a design and process in small volumes and then easily transfer to large area roll-to-roll production without changes to the laser processing equipment.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzEyMTYwNzI0ODg3LVNjcmVlbnNob3QgMjAyNC0wNC0wMyAxNTQwMzkuanBnIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 100%px;" class="fr-fic fr-dib"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1712209387228-Boston-2024-email.jpg" style="width: 100%px;" class="fr-fic fr-dib">Join us and Intellivation at TechBlick's Future of Electronics RESHAPED conference and exhibition in Boston | June 2024 https://www.techblick.com/electronicsreshapedusaDeposition of the conductive material onto the substrate was done with Intellivation’s R2R thin film vacuum deposition Lab coater , it is then laser patterned or the laser is used to isolate regions to crystallize them for interfacing with subsequent layers. Once the substrate, layer stacks and laser variables are optimized, the next phase is to scale these devices to large area R2R processing. <img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzEyMTYxMDkyODYyLVNjcmVlbnNob3QgMjAyNC0wNC0wMyAxNTQzMzAuanBnIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 100%px;" class="fr-fic fr-dib">The combination of laser patterning and sputtered coatings has unlocked new possibilities in the high-volume production of flexible 2D microelectronics. This innovative approach addresses the demand for devices with enhanced performance, precision, and scalability. A roll-to-roll approach offers several significant advantages in terms of efficiency, cost and adaptability.&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1712209445705-660d896c5506c37659840c4f.jpg" style="width: 768px;" class="fr-fic fr-dib">Intellivation will be exhibiting at TechBlick's Future of Electronics RESHAPED conference and exhibition in Boston | June 2024 https://www.techblick.com/electronicsreshapedusa

R2R Sputtering + Direct Laser Patterning is a great way to create large-area circuits on flexible circuits, even with materials such as graphene or MoS2.  The technology R2R produces high-quality uniform films on large substrates whilst the laser forms precision circuit patterns without photolith.

Flexible Microelectronic Devices produced with Sputtered Coatings and Laser Patterning

This comprehensive series delves into the fundamentals of PCB design, including design workflow, signal integrity, manufacturing, testing and debugging, advanced design techniques, and the latest software and tools available for PCB design.

PCB Design: A Comprehensive Guide to Printed Circuit Board Design - Part 2

Author: Masoud Mahjouri-Samani, PhD |&nbsp;NanoPrintek | <a rel="noopener noreferrer" href="mailto:info@nanoprintek.com" target="_blank">info@nanoprintek.com</a>Modern technology and the move toward the Internet of Things have escalated the demand for innovative and efficient printing techniques, particularly in electronics and functional devices. Traditional ink-based printing methods have long been the standard, but now NanoPrintek’s dry multimaterial printing technology has emerged as a disruptive alternative, offering numerous advantages over its ink-based counterparts. The technology’s on-demand and in-situ nanoparticle generation and real-time sintering capability allow the printing of various electronics and functional devices with pure, multifunctional, hybrid materials printing. This thus opens the path to electronics printing and other applications ranging from energy and health to sensing devices.&nbsp;<figure><div contenteditable="false"><button data-test-resize-image-button="true">Minimize image</button><button data-test-edit-image-button="true">Edit image</button><button data-test-delete-image-button="true">Delete image</button><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1711519983710-1711519983710.png" alt="" class="fr-fic fr-dii"></div><figcaption>Figure 1: Dry printing process. &nbsp;On-demand/ in-situ nanoparticle generation and real-time laser sintering that enables the printing of various electronics and functional materials and devices</figcaption></figure>Unveiling a Universe of Materials Beyond the Limitations of Ink: Traditional inks can be restrictive regarding the materials they can accommodate. Dry printing, on the other hand, opens doors to a wider range of possibilities. From semiconductors and conductors to insulators and nanocomposites, dry printing can handle a broader spectrum of functional materials rapidly, enabling the creation of more advanced and innovative functional devices.<figure><div contenteditable="false"><button data-test-resize-image-button="true">Minimize image</button><button data-test-edit-image-button="true">Edit image</button><button data-test-delete-image-button="true">Delete image</button><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1711519984882-1711519984882.png" alt="" class="fr-fic fr-dii"></div><figcaption>Figure 2.&nbsp;The ability to directly print a wide spectrum of materials</figcaption></figure><figure><div contenteditable="false"><button data-test-resize-image-button="true">Minimize image</button><button data-test-edit-image-button="true">Edit image</button><button data-test-delete-image-button="true">Delete image</button><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1711519982775-1711519982775.jpeg" alt="" class="fr-fic fr-dii"></div><figcaption>I will &nbsp;present at the Future of Electronics RESHAPED USA in Boston 12-13 June 2024 --&gt;&nbsp;<a rel="noopener noreferrer" href="https://www.techblick.com/electronicsreshapedusa" target="_blank">https://www.techblick.com/electronicsreshapedusa</a></figcaption></figure>Environmental Friendliness: Ink-based printing often necessitates complex ink formulations, storage, disposal, and cleaning procedures. Solvents and other hazardous materials can pose environmental and health risks. Dry printing, however, bypasses these concerns entirely. By utilizing solid targets as a source for on-demand and in-situ pure nanoparticle generation, dry printing eliminates the need for harmful solvents and additives, leading to a cleaner, more sustainable, and environmentally sustainable manufacturing process.<figure><div contenteditable="false"><button data-test-resize-image-button="true">Minimize image</button><button data-test-edit-image-button="true">Edit image</button><button data-test-delete-image-button="true">Delete image</button><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1711519984450-1711519984450.png" alt="" class="fr-fic fr-dii"></div><figcaption>Figure 3.&nbsp;The game-changing advantages of NanoPrintek’s dry printing technology</figcaption></figure>Cost Efficiency: Dry printing technology significantly reduces production costs compared to traditional ink-based techniques. By eliminating the need for timely and costly ink formulation processes as well as consumables like inks and solvents and minimizing waste and downtime associated with cleaning, dry printing offers a more economical solution, leading to tens of thousands of dollars in savings per year.Potential Precision and Resolution Enhancement: Due to the nanoscale size and purity of the dry nanoparticles, dry printing enables higher precision and resolution in the deposition of electronic materials. This opens the possibility of creating intricate circuit patterns and fine features, leading to improved performance and reliability of electronic devices.<figure><div contenteditable="false"><button data-test-resize-image-button="true">Minimize image</button><button data-test-edit-image-button="true">Edit image</button><button data-test-delete-image-button="true">Delete image</button><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1711519984815-1711519984815.png" alt="" class="fr-fic fr-dii"></div><figcaption>Figure 4.&nbsp;Example of dry printed lines without sintering (a) and with real-time sintering (b, c).&nbsp;</figcaption></figure>Compatibility with Diverse Substrates: Unlike ink-based printing, which may have limitations in terms of substrate compatibility, dry printing offers greater flexibility. It can be used on a wide range of substrates, including flexible materials like plastics and paper, as well as rigid surfaces like glass, ceramics, and even FR4 substrates, expanding the possibilities for product design and innovation.<figure><div contenteditable="false"><button data-test-resize-image-button="true">Minimize image</button><button data-test-edit-image-button="true">Edit image</button><button data-test-delete-image-button="true">Delete image</button><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1711519984945-1711519984945.png" alt="" class="fr-fic fr-dii"></div><figcaption>Figure 5.&nbsp;Enabling the printing on a wide spectrum of substrates c).&nbsp;</figcaption></figure>Improved Durability and Longevity: The materials deposited through dry printing electronics often exhibit superior durability and longevity compared to those applied using ink-based methods. This is due to the lack of surfactant and contaminations during the real-time sintering process, which allows better particle-particle fusion and a cleaner interface with the substrate. This results in electronic devices that are more resistant to wear and environmental factors, prolonging their lifespan and enhancing overall performance.Versatility in Applications: Dry printing electronics offers versatility in its applications across various industries, including consumer electronics, automotive, healthcare, and beyond. Whether manufacturing flexible electronics, RFID tags, sensors, energy devices, or smart packaging, this technology can adapt to diverse needs and requirements.In conclusion, the advantages of dry printing electronics over ink-based techniques are indisputable. From cost efficiency and environmental friendliness to enhanced precision and versatility, this disruptive technology is reshaping the landscape of functional devices and electronic manufacturing. As advancements continue to propel the field forward, NanoPrintek's dry printing technology promises to unlock new possibilities and drive innovation across industries.<a target="_blank" rel="noopener noreferrer" href="https://www.techblick.com/electronicsreshapedusa">We are Exhibiting at the Future of Electronics RESHAPED event in Boston (12 &amp; 13 June 2024) :&nbsp;</a><a rel="noopener noreferrer" href="https://www.techblick.com/electronicsreshapedusa" target="_blank">https://www.techblick.com/electronicsreshapedusa</a><figure><div contenteditable="false"><button data-test-resize-image-button="true">Minimize image</button><button data-test-edit-image-button="true">Edit image</button><button data-test-delete-image-button="true">Delete image</button><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1711519982835-1711519982835.png" alt="" class="fr-fic fr-dii"></div><figcaption data-placeholder="Add caption for image (optional)"> </figcaption></figure>

Multi-material printing without inks? The technology’s on-demand and in-situ nanoparticle generation and real-time sintering capability allow the printing of various electronics and functional devices with pure, multifunctional, hybrid materials printing - without inks and with bulk properties!

Dry Multimaterial Printing Technology: Unraveling New Realm of Possibilities in Printed Electronics

It is easy to take for granted actual scales when zoomed in on modern high-res flat-screens, but in reality, the surfaces of PCB boards are not two-dimensional with precisely defined edges. The layers of copper, solder mask, silkscreen and non-planar surface finishes are raised and allowing for solder mask expansion and dams can reduce space between elements even further.Allowing for sufficient component clearances is something PCB designers know all about, but many inexperienced and experienced designers still end up digging their own graves to avoid a little bit of extra rerouting.&nbsp;As careful engineer Xiao Peng learned, the perfect layout depends not only on one’s experience but also on one’s toolbox. Various tools are freely available to provide a systematic and automated approach to detecting such issues and improving the layout overall.&nbsp;Xiao Peng is a PCB layout engineer with over a decade of industrial experience under his belt from layout to production. But his recent experience caused him to doubt his abilities.As per his standard workflow, Xiao Peng’s pre-production checks consist of meticulous design review covering signal integrity, functionality and performance, design for manufacture (DFM) and design for assembly (DFA). However, for this particular batch undergoing wave soldering, the incidence of cold solder joints and insufficient through-hole barrel fill defects was unusually high. Consequently, the batch failed to meet IPC Class 2 standards.IPC Class 2 standards define strict requirements for solder joints. For through-hole joints, the barrel must have a minimum solder fill ratio of 75%, with 25% sinking allowed.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzExMDE3OTcwNzA3LVdlaXhpbiBJbWFnZV8yMDI0MDMyMTE0MTIyNi5wbmciLCJlZGl0cyI6eyJyZXNpemUiOnsid2lkdGgiOjk1MCwiZml0IjoiY292ZXIifX19" style="width: 478px;" class="fr-fic fr-dib">Xiao Peng suspected that the nearby surface mount resistor could be the culprit and upon inspection, found that the distance between the pads was only 0.2mm. This spacing was more than enough for solder mask dams to form and prevent solder bridges, however, the effect on the through-hole joint was not clear. After consulting the assembly technicians, it was found that the board was suffering from shadowing effects.&nbsp;PCB shadowing is the phenomenon whereby taller parts cast shadows on other lower neighboring parts which can have consequences on soldering, thermal management and signal integrity. For wave soldering, the nearby components can physically block molten solder from reaching certain areas of the PCB, in this case, the through-hole barrels.&nbsp;To remedy the issue, the technicians recommended a clearance of 3mm to mitigate the effects of shadowing, and even more for taller components.&nbsp;<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzExMDE4MDY4OTU1LUhRREZNIENvbXBvbmVudCBzcGFjaW5nLnBuZyIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width: 100%px;" class="fr-fic fr-dib">With wave soldering, components can affect neighboring solder joints even with the presence of a solder mask dam.At the same time, HQDFM, the PCB design analysis software from HQ Electronics was recommended to Xiao Peng, which claims to be able to detect PCB shadowing issues and many other DFM issues. HQDFM indeed highlighted the spacing issue among other errors. After following the suggestions, the new design effectively eliminated cold solder and barrel filling defects.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzExMDE4MTIxNjM1LUhRREZNIENoaW5lc2UgVmVyc2lvbiBTY3JlZW5zaG90IG9mIGNvbXBvbmVudCBzcGFjaW5nIHZpb2xhdGlvbi5qcGciLCJlZGl0cyI6eyJyZXNpemUiOnsid2lkdGgiOjk1MCwiZml0IjoiY292ZXIifX19" style="width: 100%px;" class="fr-fic fr-dib">Tight component spacing detected in HQDFM software (Chinese Version)As Xiao Peng discovered, even the most experienced engineers could do with extra assistance here and then. Unlike in China, where engineers can freely contact their manufacturers and expertise is common, overseas designers outsourcing overseas will have time differences, language barriers and limited resources to contend with.<blockquote>“I am deeply aware of the close relationship between quality and design. A good design can not only improve product performance and quality but also reduce production costs and difficulty. Inbuilt DRCs are one way of detecting issues, but they are often limited and are based on black-and-white values you have to feed in yourself. HQDFM on the other hand is powerful, informative and explicit in its goals to reduce manufacturing issues and improve reliability even if you don’t use HQ for production.&nbsp;</blockquote><blockquote>I especially liked the fact that HQDFM is free yet powerful. HQDFM looks at everything from bare board spacings to component heights and the impact on wave soldering and gives specific recommendations and figures. There aren’t many tools outside of EDA programs that can be considered essential in the designer’s toolbox but HQDFM is one of them and I will be using it extensively from now on.”&nbsp;- Xiao Peng</blockquote><h2>Common spacing pitfalls and guidelines</h2>Knowing what to look out for and the potential impact is the first step for PCB designers to improve their DFM evaluation skills which can then be incorporated at the earliest stage of design. The second is the ability to quickly detect issues, which can be accomplished with tools like HQDFM. HQDFM helps to achieve both of these goals through education and detection. Some of the component spacing issues covered by HQDFM include:<h3>Through-hole to Surface Mount Pad Spacing</h3>In Xiao Peng’s case, the close proximity of the through-hole and surface mount pads resulted in the through-hole being inadequately filled during wave soldering. For reflow soldering, insufficient spacing between through-holes, opened vias, test points, metallic mounting holes, and surface mount pads can result in solder being pulled away from the surface mount pad, resulting in poor wetting and making solder defects such as tombstones more likely.&nbsp; If spacing is limited, consider putting vias on pads, but these should be plugged and capped to prevent solder from leaking through the via. Be aware that via plugging and capping require specialist machinery and come at an additional cost.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzExMDE4NDk4MTE0LUhRREZNIHZpYS1pbi1wYWQgc3BhY2luZy5wbmciLCJlZGl0cyI6eyJyZXNpemUiOnsid2lkdGgiOjk1MCwiZml0IjoiY292ZXIifX19" style="width: 426px;" class="fr-fic fr-dib">Via on SMD pad illustration - HQDFM<h3 id="isPasted">Solder Mask Dams</h3>Any two objects that are so close together that they do not leave room for solder mask dams are at risk of solder bridges. Solder mask, or also accurately named solder&nbsp;resist, is your best friend in both SMT and wave soldering as it helps to prevent solder from building up where it is not wanted. For fine-pitch components, especially chips with underside pads, dams can be a lifesaver. For a single reflow, you can probably get away with suitably sized stencil openings, but when it comes to rework and manual soldering, the lack of dams will require greater skill and patienceharder. Pro-tip: most PCB manufacturers have their own solder mask expansion values and will not necessarily follow the lengths in your Gerber files. So a more accurate way of determining if the spacing is large enough for dams to form is to follow pad-to-pad (copper to copper) spacing from manufacturers. Also, remember that values typically vary according to solder mask color. If color is not important, sticking with regular green will produce the best results. If you need to push the limits further, use ENIG plating for a planar pad surface.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzExMDE4NTM2NTYyLUhRREZNIHNvbGRlciBtYXNrIGRhbS5wbmciLCJlZGl0cyI6eyJyZXNpemUiOnsid2lkdGgiOjk1MCwiZml0IjoiY292ZXIifX19" style="width: 400px;" class="fr-fic fr-dib">SMD Pad Spacing illustration - HQDFM<h3 id="isPasted">Solder Mask Opening to Trace Spacing</h3>Traces positioned too close to pads may inadvertently be exposed as a result of solder mask expansion and be at risk of shorting. Ensure traces are sufficiently covered to protect the trace and ensure it remains sealed by the solder mask film.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzExMDE4NjIyNDk4LUhRREZNIFNvbGRlciBtYXNrLXRvLXRyYWNlIHNwYWNpbmcucG5nIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 410px;" class="fr-fic fr-dib">Solder mask-to-trace spacing illustration - HQDFM<h3 id="isPasted">Through-hole Spacing</h3>Whether soldered manually or automated, through-hole leads need to be reachable, be it by a soldering iron, wave, lead clippers, etc. Therefore the area around them must be void of obstacles such as tall components and other leads. Insufficient adjacent and overhead clearance could result in tricky soldering positions and accidental melting of other components or oneself.&nbsp;Lower on the ground, leads of adjacent through-hole parts should be far enough to prevent solder bridges. For through-hole parts, solder mask dams are a must, which can be achieved by reducing the diameter of pads or shaving material off the edges.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzExMDE4NjU2MTE0LUhRREZNIFNwYWNpbmctaGVpZ2h0IHJhdGlvLnBuZyIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width: 399px;" class="fr-fic fr-dib">Spacing/height ratio - HQDFM<h3 id="isPasted">Wave Soldering Considerations</h3>Wave soldering’s main advantage is the ability to solder through-hole parts in volume but comes at a cost. Layout engineers have a whole host of extra restrictions to compete with, limiting placement options and possibly ruling out higher-density designs. In addition to leaving extra space between parts, engineers have to constantly consider the direction of the incoming wave, shadowing effects and the use of glue or fixtures for mixed assembly.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzExMDIxNTkxMzU1LVdhdmUgc29sZGVyaW5nIHBhbGxldCBhbmQgYm9hcmQgd2l0aCByZWQgZ2x1ZSBkb3RzLnBuZyIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width: 768px;" class="fr-fic fr-dib">Wave soldering fixture with gaps for through-hole leads and mixed assembly board with red glue dotsAs we have explored, the consequences of something as simple as component spacing can have grave consequences, but as the DFM mantra goes, it’s better to be safe than sorry. Experienced layout engineers and beginners should make it part of their workflow to pay special attention to spacings and use tools such as HQDFM to accelerate mundane tasks and act as a safety net.HQDFM is a free PCB design analysis software covering bare board and populated PCB analysis. With over 200 inspection items under 30 DFM and DFA categories including trace, solder mask and drill clearances, pads dimensions, shorts/opens, drill hole sizes and solder mask dams. HQDFM also provides tools for the designing and manufacturing PCBs including an impedance calculator, panelization tool, footprint, BOM and centroid file checker.Transform your workflow and swiftly integrate DFM methodologies into your product development with the <a href="https://www.nextpcb.com/free-online-gerber-viewer.html" target="_blank" rel="noopener noreferrer">HQDFM</a> desktop suite from HQ Electronics (NextPCB).<h2>References</h2><ol><li><a href="https://www.nextpcb.com/blog/consequences-of-insufficient-spacing-between-components-for-surface-mount-assembly" target="_blank" id="isPasted">Consequences of insufficient spacing between components for surface mount assembly (nextpcb.com)</a></li><li><a href="https://www.nextpcb.com/blog/what-is-dfa-in-design-for-manufacturing-and-assembly" target="_blank" id="isPasted">What is DFA in Design for Manufacturing and Assembly? (nextpcb.com)</a></li></ol>

Adequate component spacing is typically not high on the PCB designer's list of priorities, but oversights can be frustrating and could demand substantial re-work. Here we look at an example, give general guidelines and look at how tools can be used to educate designers and save time.

Consequences of Insufficient Component Spacing in PCB Design: A Case Study

PCB with a green solder mask and high-density interconnects

A microvia connects layers in HDI substrates and PCBs, enabling high input/output density in advanced packages.  This article delves into the role and significance of microvias in modern electronics, exploring their impact on device miniaturization and functionality.

Microvias: Pioneering the Future of PCB Design and Electronics Miniaturization

This article delves into the world of RF PCBs, exploring the design considerations that ensure signal integrity, the materials that minimize signal loss, and the intricate processes that bring these high-performance boards to life.

RF PCB: Design, Materials, and Manufacturing Processes

Close-up of a Rigid-Flex PCB featuring a microchip and miniature electronic components

Understanding the need for Rigid Flex PCB technology, capturing its manufacturing process and applications, and the innovations it has brought in modern electronics design and industrial manufacturing. 

Rigid Flex PCB: Revolutionizing Modern Electronics Design

Author: FERNANDO ZICARELLI (Printed Electronics Product Manager) |&nbsp;<a target="_self" href="mailto:f.zicarelli@e2ip.com" data-test-app-aware-link="">f.zicarelli@e2ip.com</a><a href="https://www.linkedin.com/company/e2ip-technologies/" data-test-app-aware-link="" target="_blank">E2IP TECHNOLOGIES</a> manufactures Flexible Heaters using Screen Printing Technology. We use flexible and conformable inks for the manufacturing of our heaters. Printed heaters can be manufactured in high volumes using print processes such as flatbed, rotary, and roll-to-roll presses. The size of the order and complexity of the device determines the equipment that we would use.Typical applications are Airplane/Automotive interiors, Battery and fuel cell heating, Hand tools, De-icing, Defogging, Medical, Display panels or touchscreens, Food and drink tempering, Heating for trains, mobile homes, and caravans.<figure><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1710066396502-1710066396501.png" alt="" class="fr-fic fr-dii"></figure><figure><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1710066396285-1710066396285.png" alt="" class="fr-fic fr-dii"><figcaption>Join us and the global industry in Boston on 12 &amp; 13 June 2024. Register before early bird expires on 22 March 2024. Explore program here&nbsp;</figcaption></figure>Thermal Management Solutions is a hot topic of discussion in recent months; we at E2IP Technologies have multiple solutions for every application. We currently make 4 types of heaters: Serpentine (left picture), Resistive, PTC (right picture) and Transparent heaters (see below).Each type has its advantages and disadvantages which are highlighted below:&nbsp;A. &nbsp; &nbsp; &nbsp;Serpentine heaters are made with metallic pastes which are screen printed with materials such as silver, copper, silver/carbon, graphene, and our own Silver Salt Minks. &nbsp;They are a very cost-effective solution since most of the time you only need one single printed layer of a serpentine pattern (as electricity flows through the conductive traces by applying specific voltage levels will cause the metal to heat up). &nbsp;These types of heaters are usually printed on PI, PC, PET, Kapton and TPUs.&nbsp;B. Fixed Resistance heaters combined a layer of silver paste with a resistive paste to obtain the desired value. Mixing of the resistor inks is one of the most important steps in the manufacturing of these heaters. They normally require only 2 printing steps, but a dielectric layer is sometimes added to protect from physical damage. They can be printed on PI, PC, PET, Kapton and TPUs as well.&nbsp;C. PTC heaters are made with conductive inks and a specialty formulated carbon inks (for temperature output) which are arrayed in parallel as resistors tiles. As electricity flows through the conductive traces to the carbon tiles, the temperature increases in the tiles (and so does the resistance). Both the temperature and the resistance will continue to rise until the resistance is too high for electricity to flow through (this is called the Shut-off point). Afterwards, the tiles begin to cool down until the resistance is low enough for the electricity to begin flowing again. PTC heaters normally require only 2 printing steps, but a dielectric layer is sometimes added to protect from physical damage. They can be printed on PI, PC, PET, Kapton and TPUs as well.&nbsp;D. Transparent Heaters are new to the industry and are becoming essential for LiDAR (Light Detection and Ranging) and other applications. The technology sends beams of light towards and object and then it measures the time it takes for the reflections to be detected by the sensor. These heaters are printed grids of silver with different levels of line widths and pitch distances. 90-100% transparency is not needed for applications where defrosting and defogging is needed, but in the case of cameras and sensors, it is absolutely required. Very specific substrates are used for this technology as the surface tension is extremely important to be able to produce fine line patterns.<figure><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1710066397327-1710066397327.png" alt="" class="fr-fic fr-dii"></figure> Flexible printed heaters rely on a range of conductive, resistive, and dielectric pastes which are deposited on flexible substrates, such as thermoplastic polyurethanes (TPU), polyester (PET) and Kapton. Through specific patterns and deposition levels, our engineers tailor flexible heaters to meet specified operating parameters based on the application. Printed heaters typically have a good bend radius which is a function of the materials used and heater thickness. A good rule of thumb for a flexible printed heater is to have a minimum bend radius of 0.4 in. (1 cm). We recommend that power supplied to the heater to be constant for the temperature to remain constant.For a Typical PTC Heater, the selection of the correct ink is essential to obtaining the desired; below you can see the temperature range and electrical specifications: <ul><li>Input voltage: 5 to 250 V (AC or DC)</li><li>Drive current: at startup less than 2 A</li><li>PTC inks available: 40°-115°C</li></ul> Thermal Management Solutions are different in most cases, we would like to encourage anyone to contact our Technical Team to discuss your application.Author: FERNANDO ZICARELLI (Printed Electronics Product Manager) |&nbsp;<a target="_self" href="mailto:f.zicarelli@e2ip.com" data-test-app-aware-link="">f.zicarelli@e2ip.com</a>Join the global industry in Boston and Berlin and let us RESHAPE the Future of Electronics.&nbsp;<a target="_self" href="https://www.techblick.com/registration" data-test-app-aware-link="">Register before 22 March 2024 for early bird rates</a><figure><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1710066397129-1710066397129.png" alt="" class="fr-fic fr-dii"></figure>

E2IP Technologies manufactures Flexible Heaters using Screen Printing Technology. This is one of the most important segments of printed and additive electronics with applications in cars, homes, and industrial settings. 

Thermal and Heating Solutions for Printed Electronics

This article provides an in-depth exploration of the evolution, fundamental concepts, diverse types, operating principles, and practical applications of ASICs.

What is an ASIC: A Comprehensive Guide to Understanding Application-Specific Integrated Circuits

This detailed guide will cover the fundamentals of SMT vs SMD, and THT, exploring their working principle, advantages and disadvantages, comparative analysis, and choosing the right one for electronics assembly.

SMT VS SMD (VS THT): A Comprehensive Guide to Electronics Assembly Techniques

Surface energy is a fundamental topic with implications in nearly every field of engineering, and frankly, it can be a bit mind-boggling. In the world of printed electronics, surface energy often comes up around the interactions of materials, specifically when we’re printing conductive inks onto various surfaces (substrates). While there are several factors that determine if an ink and a substrate will work together, surface energy plays its own very specific role. Let’s dig a bit deeper into how surface energy works, and more importantly, how it can impact&nbsp;your&nbsp;work.&nbsp;If you use&nbsp;<a href="https://www.voltera.io/blog/introduction-inkjet-technology" target="_blank">inkjet</a> technology, then the surface energy rating of your materials is a key determinant in whether or not an ink will be compatible with a substrate. Due to their low viscosity, inkjet inks are significantly impacted by surface energy. But, when you read the surface tension rating on your ink, how does it translate into the compatibility of your materials?&nbsp;If you’re using low-viscosity inkjet inks, then read on, because surface energy has a big impact on your materials' compatibility.&nbsp;If you’re using high-viscosity screen-printable inks, surface energy isn’t really a concern for you, but there are several other factors to consider when you’re trying to figure out whether an ink and substrate are compatible. Stay tuned for a future blog post covering this!<h3>Sci-Snack</h3><a href="https://www.voltera.io/blog/what-is-viscosity" target="_blank">Viscosity</a>&nbsp;is the measure of a fluid’s resistance to flow, due to the internal friction of the fluid. Low-viscosity inks, like inkjet inks, have very little friction between the molecules of the ink, so the match or mismatch of surface energy has a significant impact on how your ink and substrate interact.&nbsp;High-viscosity screen-printable inks have a lot of friction between the molecules in the ink. Molecular friction helps these inks hold their shape and stay where you put them, regardless of the surface energy of the substrate to which they are applied.&nbsp;<h2>What is surface energy and how does it work?</h2>Surface area&nbsp;is the measure of the total area that the surface of the object or liquid occupies.Surface energy&nbsp;is the amount of energy required to increase the surface area of a material. It applies to liquids and solids.In other words, it’s the energy required to increase the space between the molecules. The surface energy of your ink and the surface energy of your substrate — and how those two energies interact — will dictate if your ink spreads out on the substrate, forms nice contained traces, or beads up like water on a non-stick pan.&nbsp;Surface energy manifests itself in&nbsp;surface tension&nbsp;— when a liquid minimizes its surface area due to the cohesive forces between the molecules. Surface tension occurs in liquids only, never gasses or solids. Surface tension is calculated by measuring the surface energy over a surface area.&nbsp;This concept might seem complex, but if you look around, you’ll see examples of it everywhere in your day-to-day life. Right now, there’s a viral trend all over TikTok that demonstrates the cohesive forces between water molecules. You’d recognize it as “<a href="https://twitter.com/overtime/status/1509659771993042949?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E1509659771993042949%7Ctwgr%5E9eaf2411d9aaf80dbe5a8f8d579d14cedd5f5df6%7Ctwcon%5Es1_c10&ref_url=https%3A%2F%2Fkotaku.com%2Fembed%2Finset%2Fiframe%3Fid%3Dtwitter-1509659771993042949autosize%3D1" target="_blank">The Water Cup Challenge</a>”.&nbsp;In the water cup challenge, players take turns adding drops of water to a full cup. The objective is to gradually add water to the cup, and reach the threshold of surface tension without the water overflowing. The literal tension of the players builds as the surface tension of the water reaches its threshold, mushrooming above the rim of the cup, yet miraculously holding itself together. Eventually the water overflows, and the loser who poured that critical last drop gets thrown into a swimming pool. Fun times.<h3>Sci-Snack</h3><ul><li>Surface area&nbsp;is the measurement of the total area that the surface of the object or liquid occupies.</li><li>Surface energy&nbsp;is the amount of energy required to increase the surface area of a material. It applies to liquids and solids.‍</li><li>Surface tension&nbsp;is when a liquid minimizes its surface area due to the cohesive forces between the molecules. Surface tension occurs in liquids only, never gasses or solids.</li></ul>To demonstrate the concept of surface tension at the molecular level, we’re going to take a look at penguins. When it’s really cold out, penguins form a huddle to share body heat. Think of any material as a penguin huddle and the penguins are molecules. The penguins on the outer edge of the huddle — the ones at the surface — are very tightly packed together, trying to preserve heat. You can imagine that these surface penguins would be pretty difficult to remove or push around. The desire of the penguins to stay close together is like the surface tension or surface energy between molecules or atoms.&nbsp;If it’s a warm day, the penguins spread out, increasing the surface area they occupy.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzA3MjEwMzUzODU5LTYzNzNiZDI2YWYwZjkxZjQ2MjUwMDMzY19zN3d6T3ktcDltZHJTTlptTEcxa0l2OFFhRU9FOWVPVnc4ZWprOVpUejZYR21Ia0VEQk5DQnN1LUduNGFPMm81WEZIUUFWellHb2sxTS00QjV2M0IybzZSSmxKSDZCMVZGSWtPWS1ZRVNTaDRQRnpLNERMc2s2c01UcHYtTGpNQ3FzY1Q4NXJ0ejBGeE5TV1RlRjVDX1hpX0xCeVFfRmZMdUxENzMyTE5YTENGSlZDekVQbVRpbXA2Y05TZi5qcGVnIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 300px;" class="fr-fic fr-dib">If it’s cold outside, the penguins huddle together tightly to share body heat, reducing the surface area they occupy.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzA3MjEwMzcxNjQ2LTYzNzNiZDNmNjM5YTUyMjI3ZTc5MjYxOV9mUFVDZTdWLUdObE9MeHY1X3gzV1FkVi1aQlBuaGhzeDJFSDFiRHhyNjFtdXlvUHlfNVRqUXNYUDd6VkNyZldkWTg0d0R2R1lqWFVsblRqYVgydHFLa0hueWZZSlNsTXJ2WFdtLU9EcFlmNllUZGV3Q0JxMjlKdjh0VDNlTl9QLTIzME14NHdyNXZ5RE9qNGYtbTB6REJFTDVmQS14bmY1cmtRNlhZQWlqdmc3aFJaanNodm9McmlDbDhnQS5qcGVnIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 300px;" class="fr-fic fr-dib"><h3 id="isPasted">Sci-Snack</h3>If a material has&nbsp;high surface energy, that means it’s going to take a lot of energy to change the surface area of the material, so it’s going to be resistant to change. Materials with high surface energy include glass, ceramic, and most metals (and cold penguins).If a material has&nbsp;low surface energy, that means it will change its surface area relatively easily. Materials with low surface energy include soft low-density plastics like vinyl, polystyrene, and polyethylene.&nbsp;Liquid mercury, as another example, has incredibly high surface tension. When poured onto a surface, the liquid mercury pulls itself together into a perfect sphere. A sphere is the easiest way for a substance to minimize its surface area.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzA3MjEwMzg2ODY2LTYzNzNiZDU3YTQyMTdmMmEwMTNjZTNiMV8tUTFkNUw3NFhCdlBCdWlYWmZmZlZMYTNLNzJWUXFLTmJGS1RLTDNhdW1aaXFCY29QaUxoRXowd2x5amxySDE4U0RSWjY5UTdNbEdsYXNuS1pHSXhZMEVjcC1PYXEzWWs1eGJRMGU1SkpWb2hlWDZCX0t4RDQyQ0pRYTRRdUpuMTgzc3B1RUNaSEkyRDdBME9iZ1VZRU9HZDdVc0QyQm9HNFZ0cVV4UHpobGZXT2lCa2kxQnhkR3RmNzV3aHYucG5nIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 300px;" class="fr-fic fr-dib">In the iconic film Terminator 2, the terminator is smashed to pieces, and then liquifies into molten metal and pulls back together into the shape of a man. This is a great science-fiction demonstration of surface tension.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1707210457655-ezgif-3-db889fabbf.gif" style="width: 300px;" class="fr-fic fr-dib">Each material has its own surface energy rating based on the chemical makeup of the material. This applies to liquids (inks) as well as solids (substrates).When you deposit ink onto a substrate, the interaction between the ink and the substrate’s respective surface energies can result in changes to the shape of your traces. This is where you’ll see your ink do one of three things — become very runny and flat, contain itself properly, or bead up.You can determine the difference in surface energies between an ink and a substrate by measuring the contact angle — the angle of the ink droplet relative to the substrate. This angle determines if a liquid is spreading, wetting well, or not wetting at all.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzA3MjEwNTAxMDAwLTYzNzNiZDdhNDM1MzkxNWUwY2JkNjI2Nl81a1h4TFExRkZsUEhkQjU2UndUVUNkUWh1cXFIWUFKZ0JjTGZiQ2pnZTIyaGV1UFJoblNlYzZsZ0hlSkNOVUUyMmEweW5UdW1talFYbzcwM0ZVUTBjSzVLcHpacGNlQ0lpZGs2NEF1T29UTVhRQW9UVzJ1LVdPcDNaeDF3TFZEa1QwLUs2Um1leXdvbEJ1ZzRSR3hMSUN4WEh4SldTbkMwQVVOTFJBVDRFRXBDcWVDNVF3aFdQOWRXc1RVMi5qcGVnIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 300px;" class="fr-fic fr-dib"><h2 id="isPasted">Matching the surface energies of your ink and substrate</h2>The shape-quality of your traces depends on how well you’ve matched the surface energy of your ink and substrate. If the surface energies of these materials are relatively similar, then the ink and substrate will interact compatibly. You’ll get nice traces that contain themselves and stay where you put them.&nbsp;If the surface energies of your ink and substrate are quite different, they are incompatibly matched. Surface energy forces are going to change the shape of the ink and you’ll end up with traces that either bead up, or spread out too much.<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzA3MjEwNTM2NTIxLTYzNzNiZGE2YzZlOGEzZDBjMjBhNDY5N19FNi0wRVJXd09Eb01yUzh6UXhRNGRhZmVTendxSnl3bWNyNXBBcG9leGJxdXczTVFpRzVqZzhTSXVyMl9oSzJETy1RVHlZbUZ5bEs4WVYzaU1sRG10ZWFlM1I4Vl81ZlVYM294elhNNGVhSHlxZzd4OHExZzVPQlhJclBvNFRjVHpPRU8wc2hpM1ZVYzRHWWVKdXBabTFoc01mWjlFd2NLZDlxLXhCYlotcnoySk55WjhDQjExbXhQRmZ3Y0oucG5nIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 300px;" class="fr-fic fr-dib">Inks have different surface tension ratings, and substrates have different surface energy ratings, which influence how these materials interact. The objective is to find a match between the surface energy of the substrate and the surface tension of the ink, resulting in traces that make a nice domed shape and hold together properly: &nbsp;Take a look at how inks with surface tension ratings of 30 and 60 interact with different substrates.&nbsp;First, let’s take a look at different inks on polyimide. The ink on the left has a low surface tension rating of 30, and it wets and spreads out a bit too much. The ink on the right has a high surface tension rating of 60, and it beads. Based on how the inks perform, we can deduce that the surface energy of the polyimide substrate is somewhere in between 30 and 60.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1707210551204-6373c500a4217f28973d6f3a_Polyimide+Viscosity_optimized.gif" style="width: 300px;" class="fr-fic fr-dib">In this example, the same inks are applied to a sheet of PET with silica flakes to promote adhesion. The ink with a surface tension of 30 wets out significantly, flooding the substrate. The ink with a surface tension of 60 still beads a bit, but it’s closer to the kind of match you’d want for traces.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1707210574950-6373c54100a60421a99cdfa6_PET+Viscosity_optimized.gif" style="width: 300px;" class="fr-fic fr-dib">Now look at how these inks perform on the same PET, but without the adhesion promoter. The ink with a surface tension of 30 wets out a bit. The ink with a surface tension of 60 beads significantly.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1707210597173-6373c58100a60485769ce6c4_PET+Adhesion+Promoter+Viscosity_optimized.gif" style="width: 300px;" class="fr-fic fr-dib">Next, we tried an ink with a surface tension rating of 44, in between our bookends of 30 and 60. Check out how this one interacts with the three different substrates:<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1707210784581-ezgif-3-e49a46355c.gif" style="width: 300px;" class="fr-fic fr-dib"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1707210832807-ezgif-3-68b99b268c.gif" style="width: 300px;" class="fr-fic fr-dib"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1707210877485-ezgif-3-c854dd3a7b.gif" style="width: 300px;" class="fr-fic fr-dib">Based on the way the 44 dyne pen behaves, what does this tell you about the surface energy of each of the substrates? &nbsp;<h2>So what does this mean for choosing an inkjet ink?</h2>If your surface energies don’t match, it can be very challenging to get a good quality print. Unfortunately, every substrate is different, so prepare yourself for a lot of trial and error. There are some options to modify the surface energy of your substrate, if you’re willing to roll up your sleeves and do some lab work. We consulted with a friend, <a href="https://uwaterloo.ca/sensors-integrated-microsystems-lab/people-profiles/krishna-iyer" target="_blank">Krishna Iyer</a>, Optical Systems Engineer at University of Waterloo's <a href="https://uwaterloo.ca/sensors-integrated-microsystems-lab/" target="_blank">Sensors and Integrated Microsystems Laboratory</a>, to learn more about surface energy modification:<ul><li>Surface treatments&nbsp;— substrates can be treated to help match the surface energy of the ink. Surface treatments include surfactants (anionic, cationic, zwitterionic, or amphoteric), as well as plasma, corona, or acid/alkaline surface treatments.&nbsp;</li><li>Temperature —&nbsp;temperature doesn’t directly affect surface energy, but it does affect viscosity. By controlling the processing temperature, you can have a significant impact on the coverage of your ink or coating material.&nbsp;</li><li>Surface coatings —&nbsp;you can add coatings to affect the surface energy of your substrate while still preserving the mechanical properties. For example, coating PET with an adhesion promoter, or coating a surface with Teflon.&nbsp;</li><li>Surface preparation —&nbsp;there are inexpensive, accessible, non-chemical approaches to making a surface more favorable for wetting. For example, a surface with higher roughness increases the surface area and improves wetting without affecting the surface energy, but this can have the opposite effect if roughness is too high (see <a href="https://www.youtube.com/watch?v=54lDqR6LU8E" target="_blank">Wenzel effects</a>).&nbsp;</li></ul>With higher viscosity screen printing inks, like those used with <a href="http://voltera.io/nova" target="_blank">NOVA</a>, the internal friction of the ink makes it less impacted by surface energy effects. This enables you to print on a much wider variety of materials without changing your formulation, so you may want to consider switching technologies to avoid the headache.&nbsp;

In the world of printed electronics, surface energy often comes up around the interactions of materials, specifically when we’re printing conductive inks onto various surfaces (substrates).

What is Surface Energy?

The adoption of healthcare monitoring devices that are both flexible and conform to the wearer have gained traction1. Spurred on by the need for remote care during the COVID-19 pandemic and technological advances in sensor accuracy, wearable health monitoring devices have become more ubiquitous in many areas of healthcare. In particular, there has been a rise in the development of wearable sensing and monitoring devices for telemedicine operations. Telemedicine has grown significantly in the last few years—and even more so during the COVID-19 pandemic when doctor-patient contact was limited—to remotely monitor patients in their own homes so hospitals could free up much-needed beds. While wearable technologies can be used in clinical environments to provide an analysis, much of their potential is in remote health monitoring.These wearable sensing devices typically make use of flexible materials, such as polymers, thin films, 2D materials and other nanomaterials. Health monitoring devices often consist of a flexible material that conforms to the wearer and is integrated with electronic components, including sensors, a power source—be it a battery, solar cell, or some other type of energy harvester like a nanogenerator—communication technologies if it transmits data to a central processing system, and any relevant circuitry.Building electronic components that are small and flexible enough to be used in wearable technologies is not that straightforward, and is why different nanomaterials—especially 2D materials—are often used to create the components because they fit the bill and can be easily integrated. But another approach is gathering interest: printing sensors—the most crucial aspects of a monitoring system—directly onto the wearable device.These printed sensors are sometimes made of 2D materials and other nanomaterials, but other materials can also be used as well. The ability to print sensors onto wearable health monitoring devices could pave a way to a much simpler and easier route to commercializing more wearable monitoring devices—especially if conventional, inexpensive, or easy-to-use printing technologies are used to print the sensor.<h2>Why Printed Sensors?</h2>While a range of advanced deposition and nanodeposition methods exist that can fabricate thin-film sensors on the substrate for wearable devices—often a soft polymer due to their flexibility and conformability—a number of biomedical sensors can be printed using screen printing techniques. Other techniques, such as inkjet and transfer printing, can be used as well, but screen printing is seen as the best option for printing sensors.Screen printing equipment is widely available, has a relatively low cost, and is easier to use than more advanced deposition methods, so it offers a much more scalable and commercially feasible route for using printed sensors in healthcare monitoring devices. Screen printing can also be used with many materials—from polymer solutions to conductive nanomaterial inks—so it is a versatile platform for printing a number of sensors.So, why print sensors instead of creating them through other manufacturing routes? Screen printing is a simple, fast, and efficient printing technique that can produce a large number of identical patterns in a single print. For large-scale operations and commercialization potential, screen printing can easily be adapted for mass production at a lower cost than other methods.From a performance perspective, screen printing provides high-resolution patterning and can print over large areas. The ability of screen printing to deposit material on demand in a given location also helps to reduce waste—especially on large scales—compared to traditional manufacturing methods because it is all done in a single step.There are, therefore, a number of manufacturing benefits with using printing methods. Beyond that, a greater design capability exists for health wearables because printing methods enable the production of sensors that are not only very thin but also provide the ability to print on the surface of the device. This approach is much simpler than trying to integrate devices into the material matrix of the wearable. You can also create a more customized sensor because you can print on demand, and the printing process can be changed to make a different sensor much easier than a typical manufacturing line.In terms of the materials compatible with screen printing, the scope is vast. Depending on the type of sensor being created, a whole host of materials can be used. On the one hand, a range of metals can be made into printable conductive inks to build the sensor. Common metals for wearable health sensors include gold, copper, platinum, nickel, aluminum, and silver. Beyond metals, a range of nanomaterial composites (graphene, carbon nanotubes composites), functional nanomaterial inks, and silver composites have all been used as the active sensing surface in printed health wearable sensors.The sensors also need a platform to be printed on. This often takes the form of a conductive polymer so that the sensor can better interact with the skin and the other components to provide higher sensitivity and reliability. PEDOT:PSS is the polymer platform that is most widely used for printed sensors, but other polymer materials include polyacetylene, polypyrrol, polyphenylene, poly (p-phenylene vinylene), and polythiophene polyaniline.<h2>The Printed Sensors of Interest in Healthcare Monitoring Applications</h2>Just as many materials can be used to create printed health sensors, many different types of printable sensors are used in health monitoring devices. Take, for example, strain-based sensors. Strain-based sensors measure a form of movement, and these wearable sensors are used in human-physiological signal monitoring and human-joint motion monitoring approaches.Another healthcare specialty measures different biomolecules and human signals. Non-strain-based sensors detect the biomolecule of interest directly or by directly measuring a physiological parameter that the patient exhibits. From a molecule-sensing perspective, a number of biomolecules in the blood can be detected, with glucose levels being a common one as well as the presence of sweat on a person’s skin. From a signal detection perspective, printed sensors can now detect respiration and heartbeat levels in a patient and provide remote electrocardiogram (ECG) monitoring.Another class of printed sensors for wearables is sensor arrays. In sensor arrays, multiple sensors work together to detect more complex issues or issues that require analysis from several stimuli angles. Sensor arrays are helpful in monitoring gait during walking, monitoring the sitting posture of wheelchair users, and monitoring the skin.Finally, there’s been advances in the development of printed temperature sensors for wearable health devices. Thermal sensing is a key area in disease detection because the body suffers thermal stresses when there is a disease present, and the rise in both skin and deep body temperature can be a primary indicator of a serious disease. Using printed temperature sensors, health wearables can detect a range of chronic diseases, such as cardiovascular, diabetic, and pulmonological diseases, as well as cancer.<h2>Conclusion</h2>Health monitoring wearables are gaining acceptance as an effective way to remotely measure many health factors of a patient. The most important aspect of these wearables is the sensing system that provides the analysis on the patient. For patients to be willing to wear the health monitoring device over an extended amount of time, the sensors and other components need to flex with the wearable component. While integrating flexible sensors is possible—for example, by using thin nanomaterials—printing sensors on the device’s surface is much easier, requires less material, and is much more scalable.A variety of printed health wearables are already in existence (commercially and academically. The printing methods discussed offer a route to achieve widespread distribution of health wearables. While many options are available, screen printing is the leading printing technology because it is highly versatile and can be used with many materials to create sensors that monitor different aspects of a person’s health—from heart rate to detecting a chance of a disease, to the different biomolecules in their blood, and many more in between.

The COVID-19 pandemic and advancements in sensor technology have led to the widespread adoption of wearable health monitoring devices, particularly for telemedicine, to facilitate remote patient monitoring.

Printable Sensors: A Key Technology for Health Wearables?

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