Manufacturing next-generation electronics like they are T-Shirts
Since its inception screen printing has been transforming the world by producing art, posters, and colorful patterns on textiles. New developments in the realm of material sciences will propel this technology to the center of next-generation electronics.
Screen printing, as the name suggests, is a printing technique based on a patterned screen. The screen is made up of threads with small openings through which ink can be passed onto a substrate. Patterning is achieved by using a light-sensitive emulsion to block the openings where no ink is supposed to flow. To know more about screen printing check out this superb tutorial by Applied Science on YouTube.
Multiple copies of the same pattern can be printed quickly, and this makes screen printing ideal for large-scale production or even producing small batches of customized solutions. Nearly all customized logo apparel is made with screen printing. So, can this technique be employed to manufacture next-generation electronics? The answer is yes!
Currently, electronics are mainly produced by subtractive processes like PCB etching which are unsustainable. Screen printing, being an additive process, saves materials and energy can make manufacturing sustainable. This technology is highly developed and is behind most of the printed textiles in the market today.
Screen printing electronics has been known for quite some time. Membrane switches and RFIDs are manufactured using conductive silver ink. But recent advances in material sciences have resulted in commercially feasible inks with copper, carbon, conductive polymers, and many more. Combined with large-scale manufacturing, this technique can replace conventionally manufactured PCB-based sensors and small electronic devices.
PCB Fabrication using Screen-Printing
The most obvious application of screen printing is to print copper directly onto FR-4 PCB substrates. Such inks can be sourced easily via Copprint or Novacentrix to name a few. The best part of using these inks that they are directly solderable, so need for silver epoxy or likes. The YouTube video below shows the application of Copprint’s copper ink onto FR-4.
Cost and electrical performance of screen printing inks
Of course, one needs to consider the economic and technical feasibility of new innovative techniques. Let us consider a regular double-sided Arduino UNO board with dimensions 68.6 mm x 53.4 mm. Assume that we need to cover 100% of both sides, which means we need to print 0.00733 square meters of ink. Consider the thickness of the dry layer is chosen to be 25 microns because the datasheets normalize the sheet resistance to this thickness.
One of the thinnest traces on the Arduino board has a width of about 11 mils. So let’s consider a trace of that width and having a length of twice the board length, i.e., 2 x 68.6 mm. The following table lists the cost of coating a double-sided Arduino UNO PCB (including a 20% ink loss) and the resistance of the above-defined ‘thin trace’. This table does not include Novacentrix inks because their datasheets do not state the theoretical coverage of the ink.
An Arduino UNO board screen printed with conductive inks has a cost of about $1.19 to $1.89. The thinnest trace on the PCB will exhibit electrical resistance between 1.08 ohms to 6.37 ohms. Copper inks are more economical and offer better electrical performance. However, for applications that require biocompatibility, silver inks from Dycotec Materials and others are more suitable.
So what else can you make with conductive screen-printing inks?
Electrochromic Displays
Ynvisible’s Electrochromic Ink Kit is ideal if you want to build displays instead of just PCBs. Electrochromic displays change their color in response to an electric impulse. You could include these low-power displays in your next IoT project.
Electroluminescent Devices
Want to build something bright? Then follow this tutorial by the Zurich University of Arts to screenprint electroluminescent devices. These devices emit light in response to an electrical signal.
Do you want to go large-scale?
The beauty of screen printing electronics lies in its scalability. You can use a screen printer to print several thousands of devices in a single day. One can even print disposable eco-friendly RFIDs on paper! Or mass produces health sensors using roll-to-roll screen printing like Mekoprint. This revolution in the electronics industry is just getting started.
So what are you planning to make with a screen printer? Comment below if you have any questions or suggestions. You can message me on LinkedIn if you want to discuss the new opportunities made possible by screen printing.
