Paper circuit board substrates have better characteristics than polyimide materials.
Design teams can achieve more creativity through the use of paper circuit boards.
New technologies have increased the stability and reliability of paper circuit boards.
Paper circuit boards are an environmentally friendly PCB design solution
As a young boy, I loved paper airplanes. Later in my studies, I was delighted to learn that paper airplanes obey the same laws of aerodynamics that dictate the performance of a supersonic jet. Although paper airplanes can only work as models of aerodynamic performance, paper circuit boards have come to be seen as a realistic, environmentally friendly printed circuit board (PCB) design solution.
Advances in Paper Circuit Board Research
Research during the past several years has uncovered advances in paper circuit boards through the production of transparent cellulose nanopaper that works as a flexible PCB substrate. Researchers were able to create a plasma metallization process that transforms paper into solderable PCBs. Paper-based technologies have also allowed researchers to print memory devices on a wrapper paper substrate, enabling the printing of electronic components on cellulose composites.
Paper Circuit Boards Emphasize Design for Environment Principles
Each of these steps into the future of electronics allows us a glimpse into the future of electronic product design. Now, manufacturers can develop lightweight, flexible products that include printed intelligence. Additionally, the entrance of paper PCBs into the marketplace allows design teams to emphasize Design for Environment (DfE) principles within one-time use electronics.
DfE principles push designers to consider the impact of a product on human health and the environment. Bringing the principles from concept to reality includes an assessment of the chemicals used in products and the impact of releasing chemicals when a product reaches end-of-life. DfE principles also encourage companies to use practices and technologies that do not harm the environment. Researchers have shown that the manufacturing of paper-based multi-layer PCBs has a lower environmental impact than the manufacturing of organic PCBs. Life-cycle assessments of paper PCBs show improvements in reducing or eliminating the release of toxic chemicals that harm life, deplete the Ozone layer, and increase global warming.
Paper Characteristics of Paper Circuit Boards
In the past, the normal characteristics of paper led to problems with conductive inks penetrating the pores of paper substrates and becoming segmented. Sintering processes also harmed the stability of the substrate.
One research team changed the characteristics of paper available from any store so that the paper would work as a PCB substrate. The change in characteristics occurred by applying physical vapor deposition in each fabrication step to stack an electrically conductive structure within the paper without damaging the substrate.
Physical Vapor Deposition
Physical vapor deposition (PVD) changes materials from a condensed phase to a vapor phase and back to a thin film condensed phase at the atomic level. In most instances, the process converts the material to vapor by using either a high-temperature vacuum or gaseous plasma. Then, the PVD process uses pressure differences to transport the vapor from its low-pressure source to the substrate. A final step within the PVD process allows the vapor to condense on the substrate and form a thin-film coating.
The process covers a surface—such as the paper substrate—with solid conductive material. Design teams use several types of conductive materials, including aluminum oxide, to build the vertical stack of conductive materials for memory devices. Coating the substrate with a conductive thin film yields memory devices with excellent electrical characteristics, reproducibility, and stability.
Along with producing a substrate that meets Design for Environment principles, the use of a paper substrate also provides a highly flexible substrate that has little degradation.
Another process called plasma metallization offers promising results, allowing paper to work as a printed circuit board. Plasma metallization involves the use of a plasma spray head to high-pressure spray a powdered conductive metal onto a silver paste-coated base material. Once the conductive metal coats the base material, a hot plasma jet melts the conductive metal so that it combines with a silver base to form a highly conductive substrate.
Initial tests with plasma metallization have allowed the limited production of flexible printed circuits. The lightweight coated paper substrate costs less than the standard polyimide substrate while providing good strength and excellent load-bearing capacity. The use of a flexible base material opens the door to more creativity for design teams. As an example, researchers point to plasma metallization as opening the door to the possibility of electronic postcards, posters, and packaging.
Along with physical vapor deposition and plasma metallization, teams have used a copper phthalocyanine (CuPc) organic thin film as a buffer interlayer in aluminum tracks printed on paper. The use of the CuPC buffer interlayer and the aluminum tracks increases the reliability and the DfE qualities of the flexible paper PCBs.
Paper Circuit Boards May Lead to New Applications in the Future
Research on the production of paper PCB technologies continues, as researchers work on how to use this technology for larger-scale production. The possibility of producing printed circuit boards that can fold, become trimmed with scissors, or form three-dimensional structures may have military and medical applications. In industry, the capability to produce very lightweight, biodegradable PCBs can lead to micro-sized electromechanical devices that include conductive inks, inkjet-printed RFID tags and sensors, printed integrated waveguides, and other embedded or printed electronic components.
Without a doubt, paper circuit boards are changing the future of PCB design. To view the latest research on PCB design, visit the PCB Design and Analysis Software page. Allegro PCB Editor keeps you up to date with industry trends, ensuring excellence for your next design.
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