Lyo-Gold in PCB fabrication concerns for mmWave Circuits in the next generation of space telecommunications

Printed circuit boards (PCBs) are integral parts of satellite technology and contribute to almost every aspect of satellite functionality - this includes signal processing and communication, data handling and power processing and distribution. Satellites are one of the most important parts of the global communications infrastructure, which means that any problem, error and degradation in the signal can have a significant negative impact. Since PCBs have to operate in harsh environments and have to meet strict space and weight requirements, the design of a satellite PCB has to be made with special materials. The materials used in PCBs for space applications have to withstand extremely low and high temperatures, pressure, vacuum, gravity, vibration, mechanical deformation, etc. High performance substrates, such as ceramic or polyimide are often used, which are able to withstand extremely harsh conditions. Lyo-Gold (gold nanoparticles) can potentially be used on satellite PCBs because they are highly corrosion resistant and have high conductivity. Their properties, such as a crystal structure like bulk Au, high ionisation energy and quantum nature, could be suitable for use in space applications, and may represent a new high-engineering material for specific applications such as satellite communication systems. High-speed radio frequency (RF) signal transmission is needed increasingly in PCBs for mass data processing in electronic systems. The transmission speed of signals propagating within the system is also increasing. The key is the RF signal loss, i.e. the insertion loss, which is the degradation of signal strength resulting from the insertion of a device into a transmission line or optical fibre. The insertion loss is made up of different types of losses: conductor, dielectric, radiation and leakage. Most PCB materials do not have issues with leakage loss due to high volume resistivity. Radiation loss is dependent specific of design, while dielectric and conductor losses are dependent on material properties. Expressed in decibels (dB), insertion loss becomes significant on PCBs at higher GHz frequencies. Insertion loss can cause degradation of signals at the rising edge, higher speed bit errors and other problems. It is known that the high-speed RF signal in printed circuit boards is transmitted exclusively through the upper surface with a thickness of a several μm, so this phenomenon is known as the "skin effect". Therefore, the key requirement in the preparation/production of such printed circuits is to achieve the lowest possible level of roughness of the upper surface, as high roughness represents higher losses the high-speed RF signal. Reducing signal loss and preventing errors is a key challenge in the application of high-pass RF filters. The use of a new material such as Lyo-Gold can be crucial, as it is expected to achieve a significantly lower roughness (lower as 2.8 μm) resulting in a reduced skin effect and reduced signal loss, which represents a major advantage over existing materials.

The proposed work using Lyo-Gold for screen printing and subsequent post-deposition curing of mmWave Circuits is anticipated to reduce insertion losses for high-pass radio-frequency filters. This work, starting from a basic TRL 1 towards an experimental proof-of-concept TRL 3, represents the first stage of developing Lyo-Gold screen printing suspension appliable for other mmWave Circuits with low signal losses. Communication Technology Standards increase their data transmission rates on a regular basis, where low insertion loss mmWave Circuits can make a considerable contribution in signal quality. Upon successful implementation of Lyo-Gold thick films, the next stage of the development plan is to use thick-film technology in preparing Circuits and components for low-volume space telecommunications RF systems, for use in LEO (Low Earth Orbit), MEO (Medium Earth Orbit) and GEO (Geostationary Earth Orbit) satellites. Initially, this technology can be used in the market for telecommunication RF systems for micro satellites, with promising opportunities for expanding into other 13 / 28 space sector areas. The technology has the potential for expanding into other wireless communication technologies for increasingly higher transmission rates, with the required high signal quality and stability. With additional development activities, it would, later, also be able to be used in mobile telecommunications, such as 5G and, later, 6G. The development of this technology benefits the involved institutions and companies from Slovenia directly with initial steps of a product development for Space, with potential for use on future ESA missions or commercial missions. The work allows for the advancement of technical know-how and expertise for all involved in the individual components of preparing the low signal noise mmWave Circuits with Lyo-Gold. This includes Lyo-Gold production, preparation of pastes, screen printing, characterisation, and the use of such Circuits for space telecommunications RF systems.