Silicon photovoltaics (PV) are one of the most important markets globally for printed electronics. This is because each wafer carriers a small of fired screen printed silver paste. Indeed, this could be the largest market worldwide. The chart below- from the indistry roadmap ITRPV 2022- shows the amount of Ag metallization utilized per wafer (both front and back metallization) per watt depending on the type of silicon photovoltaic (monofacial p-type, TOPCon n-type, HJT n-type, etc). It shows that today something around 25-30 tonnes is used per GW of solar for HJT n-type PV and around 12-14 tonnes for monofacial and bifacial types. Considering the size of the PV market, this translates into a 100+ tpa market! As shown in the charts below, screen printing remains the prevelant technology for metallization, despite long-term attempts by other technologies to make even a small dent into this space. In the long term future, other technologies such as plating on seed layer or stencil printing are expected to obtain a small foothold, although we have heard this story too many times already. There are various screen printing techniques. Single print and dual print (finger and bus bar printed seperately in two seperate steps) are the most common techniques. Double printing (print a second layer on an already screen printed already for better aspect ratio) is also popular. The advantage of dual print is that different paste types could be used for fingers and bus bars, giving optima...

(AME/PE) Speaker: Chris Booher | Company: ChemCubed | Date: 10-11 March 2021 | Full Presentation ChemCubed, a U.S. based manufacturer of materials and printing solutions for 3D printing / Additive Manufacturing, will present their ElectroJet brand solutions for AME/PE covering the offerings of materials (silver conductive and dielectric insulating inks), equipment (electroUV3D inkjet printer for electronics), and processes. The multi-faceted portfolio will be highlighted for differentiation in performance, economics, flexibility, compatibility and benefits to key applications and market segments. ChemCubed will also present examples of the ElectroJet brand’s resulting solutions to date by application, further understandings of unmet needs within the industry and emerging technology to address the needs in the future developments of materials and equipment. Christopher Booher Chief Marketing Officer @ ChemCubed Bio Chris Booher holds a BBA in marketing with over 25 years of business experience in the packaging and materials industry and is committed to growing ChemCubed’s leading technologies position in the 3D printing materials market. He has worked with multiple companies from privately owned expansions to Fortune 500s headquartered in the USA and Europe. His experience ranges from full P&L general management, sales and business development for application-specific technologies in paper, films, adhesives, specialty coatings and printing inks. Chris is focused on partnering ...

Impulse Printing- unveiled and presented recently at TechBlick- seems to be an exciting technology. The technology details are not yet fully disclosed, and the development is still at a laboratory stage, but the disclosed results and claimed performance levels are incredible. As you can see below, the technology can digitally print tracks with resolutions as low as 2um and as high as one millimeter. It can print materials with an extremely wide viscousity range, from 0.1 to 10,000 Pa.S, meaning that it can print copper and silver inks as well as solder and epoxy(!) based conductive adhesives! The technique prints over 3D surfaces, able to print over gaps as short as 1um and as tall as 10mm. This digital printing technique can print sequential as well as simultaneous patterns at high speeds. The diversity in all paramters (resolution, print gap, viscosity of ink or pastes, etc) is very unique for any digital pritning process. Indeed, as shown in the chart belows, each technology occupies a given position in terms of resolution/feature size, viscosity, print gap, etc). Perhaps, as this technology inches towards scale-up, trade-offs will become clear, and not all the reported performance benefits will be satisfied at the same time. The technology is still young and in development. Today, the print area is a small (1x10mm2) but there is a roadmap to scale the tool to be able to print first at 20x20mm2 and then 96x96mm2. Watch this space as the technology will soon be spun out int...

Flexible Hybrid Electronics (FHE) brings together the best of printed and flexible electronics with rigid Si-based electronics. A critical and often limiting bottleneck is the interconnect between printed (often wide) and Si ICs (often narrow pitches). Normal solder can not easily be used because (1) substrate such as TPU (stretchable electronics) and PET (flexible electrodes) impose severe temperature limitation, often even below bismuth-based low-T solders, and (2) some inks, specially Ag inks, dissolve in solder. Furthermore, these interconnects need not only support the pitch sizes of the ICs, but also survive flexibling as well as stretching, and be compatible with standard industry processes. One option is to deploy particle filled (often Ag particle) epoxies to form the interconnects. Here, unless it is anisotrophic, then the pitch sizes will be limited. Furthermore, particle loadings are often high to achieve high conductivity, adding to cost. Sunray has developed a novel solution: they disperse ferromagnetic particles within a two-part epoxy system. Under an external magnetic field, the particle align vertically, forming z-axis conductive paths. Here, the pitch can be down to 100um. The curing temperature can be as low as 80C, making compatible with TPU and PET. The material can sustain extreme repeated stretching. Furthermore, the process is, as shown below, compatible with standard SMT process. The material can be stencil printed or dispensed. Once the component i...

Rolling nanolithography can take the linewith resolution of R2R lighography even below 1um. This technology, by Meta Inc (Meta Materials Inc) includes a roller around which a mask is wraped and within which a UV light sits. The wrap-aroud mask itself it manufactured using electron beam lithography, giving it very fine features. Therefore, the mask can support, like nanoimprint technology, nano-meter scale features. However, the UV exposure itself may limit feature size to 500nm or 1um range. The current web size is 300mm although Meta is developing technology to scale this to 1200mm webwidths. Here, a step-and-repeat process can be used to create larger rolling masks (note: there might be some 100um wide discontinuities and thus may not be fully seamless, although they are workarounds for this). To achieve single-layer ultrafine line metallizaiton, first a photoresist is deposted and then patterned using the rolling UV mask. Next, a thin metal layer is R2R evaporated (AI or Ag, for example) before creating the final pattern in a R2R lift-off process. Ultra fine features with excellent aspect ratio (300nm/100nm) can be achieved. This is a wide web industrial R2R or R2S process that can print few micron or even sub-micron features on 1.2m wide webs at lenghts of 6 km and at print speeds around 2-10 m/min speeds. The embedded slides show examples of products. On slide 2, you can see the examples of fine feature sizes achieved, putting the technology in the same feature size ra...

A major challenge in printed electronics is the inability to solder directly on Ag paste (the most common ink and paste material) because no intermetallic layer is formed. With Cu, this can be different. Here, Copprint is showing results, demonstrating that one can directly solder onto their Cu pastes with good shear test results, even if sometimes the wetting is not the best. It also shows how a strong intermetallic layer is formed during the solder, for example, with the standard SAC305 solder on an FR4 substrate. This is an important advancement of the art because it makes printed electronics more compatible with standard SMT processes. Furthermore, the Cu ink is compatible with low-T solders too, enabling one to solder components directly onto a PET substrate with printed Cu lines. In general, Cu inks have had issues in the past. The conductivity has not been high enough, meaning more material is needed thereby eroding their $/Kg advantage vs. Ag. They have also required novel sintering steps with a new learning curve and with new equipment. The data from Copprint suggests that their ink can be sintered very fast and achieve conductivity levels outperforming those of classic Ag suppliers....

Printed electronics technology is evolving. A development direction is ultrafine line printing, increasingly allowing the technology to encroach into the realm of photolithography. The example here, developed by VTT, demonstrate a process for sub-micron printing. The process is reverse offset printing. Here, the PDMS roller is first coated with the ink. The ink semi-dries on the roller, partially through absorption into the PDMS. This semi-dried state allows one to overcome wetting-related issues when inks are in liquid state. The inked PDMS roller is brought into contact with a Cliche, or relief plate, removing parts of the inks. The patterned semi-dried inks on the PDMS roller are then transferred onto the final substrate. In this example VTT achieves 1µm direct printing of silver nanoparticle inks. The desktop RO printer was used to print a metal mesh on PET with 1µm linewidths. The reported sheet resisitivty is not very low (100Ohm/sqr), probably because the lines are very thin. In general, note that ROP can enable minimum resolutions between 0.5-5µm, printed thickness lines around 20-1000nm, overlay accuracy <2um, and printing speeds of 50mm/s (3m/min)....

To scale up microLED displays to large areas, smaller displays can be titled. Because microLEDs can be truely edge-less devices, the tiling can function, yielding a seemless look. Each title should house the microLEDs, backplane, as well as driver electrodes. The microLEDs and the backplane sit on the front side of the glass substrate whilst the driver electrodes are tucked away at the back. Interconnects are needed to connect the two. Wrap-around electrodes (interconnects wraping around the edge to connect front and back) is an elegent solution which bypasses the need for a drilled and filled through-glass via. The wrap around electrodes can be printed or PVD deposited (both prefer chamfered glass) . The latter can yield better feature sizes and thin and conductive lines, whilst the former can increase productivity. The below images demonstrate various technologies. Screen printing is a robust solution with low TACT time. Applied Materials has demonstrated that it can screen print very narrow (30um) linewidths over narrow spacings (50um). These are excellent results. Note, by way of reference, that state-of-the-practice/production and state-of-the-art in screen printing of conductive paste on silicon solar PVs are 35um and 20um, respectively. In the process, first the top and botton electrodes are printed before the substrate is rotated (with excellent alignment) to print the electrodes over the edge. This technologies requires excellent machines. Applied Materials has lau...