The use of printing technology for industrial production processes in microproduction has long been considered the holy grail of 3D printing. Companies have certainly tried, but existing technologies such as traditional inkjet printing have not been able to provide the ultra-high resolution and accuracy of placement needed to be efficient and affordable.
Keep going today and there is a wide range of new technologies on the horizon that have the potential to transform many markets, most notably the semiconductor and display industries. It is clear that we have entered an era in which digital printing has successfully expanded from graphic to 3D printing of geometric objects and is now on track to make the next quantum leap, enabling functional printing of microelectronic products.
Limitations of traditional inkjet printing
As micro-manufacturing industries, such as the display market, begin to realize the benefits of additive manufacturing, printing machine manufacturers are required to provide printing technology that can produce 100 times finer detail than conventional graphic printing. . In the case of inkjet printing, the left diagram below illustrates how conventional technology works: The liquid is squeezed from inside the fine nozzles, creating small ink droplets.
Figure 1 The image above highlights the performance parameters and the differences between conventional piezo-based inkjet printing and new electrostatic technology. Source: Scrona AG
The problem with the traditional actuation process is that it only allows the disposal of thin inks, which are then leveled on the substrate due to their high fluid content. Triggered droplets are not smaller than the size of the nozzle from which they are ejected. This conventional push concept physically limits the size of the nozzles to a few tens of micrometers and thus makes it difficult to achieve the ultra-high resolution required for microproduction.
A new and alternative approach is to use an electrostatic force that pulls the liquid out of the nozzle, forming a pointed cone and focusing all the energy to the top of that cone. It is from this small peak that small droplets are ejected, accelerated and directed downwards. Due to the effect of focusing the force, the droplets are no longer limited to the size of the nozzle, but can actually be reduced more than 10 times.
Since it is not necessary to direct force to the nozzle outlet from the inside of the nozzle, the technology becomes essentially agnostic to the thickness of the ink, allowing both thin and thick liquids to be processed almost equally. Small droplets can be placed directly on the substrate and small volumes dry quickly and form into 3D projects smaller than 1 µm.
Because the principle of electrostatic discharge is more or less independent of ink, it opens the door to the use of a wide variety of inks. These inks can be at least 100 times more viscous than the inks used in today’s conventional inkjet printheads. In theory, it is even possible to print with honey. This ability to print with many types of liquids expands the use of nanoparticles in addition to typical metal inks in a wide range of materials, such as:
- Molecules and saline solutions
- Microparticles and proteins
- Melts, waxes and epoxies
Through this new process, expensive ink treatments to make their rheology compatible with inkjet printheads are becoming obsolete. While a single nozzle already demonstrates unprecedented performance for microproduction, economic use becomes viable only by reproducing these nozzles 1000 times with the help of a micro-fabricated MEMS chip.
This allows the digital microproduction of functional elements printed from multiple materials in a resolution invisible to the naked eye. This in turn allows the development of products that we only imagined. One example is the invisible touch screen, which can be printed as quickly and economically as printing an image on a typical office printer today. This capability has the potential to revolutionize the production of semiconductors, displays and many other similar products.
Implications for semiconductor manufacturing
The ability to print on any material, on a scale, can improve the speed, accuracy and cost of producing innovative products for today and tomorrow. Semiconductor and display industries are ideal targets for additive manufacturing to reduce their complexity, high cost, and high water and energy consumption, while providing the required high resolution.
As shown in the graphs below, this can reduce the production steps of certain semiconductor components for the rear end by 10 times, while significantly reducing material, energy and water consumption. With many steps – more than 20 required for one component of a semiconductor device – production can take up to 15 weeks, with 11-13 weeks being the industry average. In addition, a semiconductor plant can use between 2 and 4 million gallons of ultrapure water (UPW) each day, which is roughly equivalent to the water consumption of 40,000 households.
Figure 2 Functional additive manufacturing printing can reduce the manufacturing steps of certain rear-end semiconductor components – such as micro-manufacturing redistributive layers (RDL) – by 10 times.
Other markets can also be transformed through this type of technology. For example, as yet unprecedented resolution and layer thickness control can allow the printing of RGB color filters with quantum dots for high-brightness, full-color micro-LED displays in augmented reality glasses for gaming and metauniverse applications. It can also be used for printed circuit boards / printed electronics, MEMS and sensors, life sciences and security printing.
Using the principles of electrostatic discharge, it is possible to achieve simultaneous printing from a large set of nozzles, with the following advantages over conventional inkjet:
- Ultra high resolution printing with 100x higher resolution
- High speed printing with 10 times higher ejection frequency
- Smaller droplets not only for higher precision, but also for quick drying
- 3D printing with aspect ratio> 10: 1 is possible together with nanometer layer thickness control
- Customize the MEMS printhead, dynamically and fully programmable
- Prevent nozzle clogging with its own environmental control system (ECS)
The unique combination of high resolution and high productivity has the potential to rediscover micro-production for mass production, accelerating the invention of the product in an economical and environmentally friendly way. This is a quantum leap for a wide range of industries from semiconductors to molecular printing in biotechnology.
Walter Brown is the Chief Operating Officer of Scrona AG.