Racing into Space
Durability in the heavens can lead to sustainability on Earth.
We are increasingly reliant on satellite-borne services, as evidenced by the huge increase in launches in the past few years. The United Nations Office for Outer Space Affairs (UNOOSA) has recorded over 5,500 launches between 2020 and 2022 in its Register of Objects Launched into Outer Space. This contrasts with typically 100 to 200 per year from the early 1960s until 2016.
The vast majority of satellites in operation today support communication applications such as Internet services. Of the 6,718 operational satellites at the start of 2023, 4,823 are communication satellites. While their number has increased more than 50% since 2022, there are also over 1,200 Earth observation satellites, up by more than 13%. Others are used for technical development, navigation and positioning, and space observation.
We need the services these space vehicles provide. The Starlink constellation, delivering high-speed Internet services, operates in a low earth orbit at an altitude of about 550km. It can boast much lower latency than typical Internet satellites in higher, geostationary orbits needed to support streaming services and video calls. This enables high-quality services to reach areas where installing ground-based Internet infrastructure is not cost-effective or practicable.
Highly accurate position, navigation, and timing (PNT) data from GNSS constellations are, of course, another valuable service provided from space. Potential benefits are many, including improvements in oceanography that can protect the marine environment, precision farming for more efficient food production and better supply chain management resulting in lower emissions and accurate tracking of goods in transit to reduce losses. A recent study calculated that drivers in the US alone have traveled more than 1 trillion fewer miles between 2007 and 2017 thanks to the effects of satellite navigation, saving billions of gallons of fuel and the associated emissions.
Space is arguably the most demanding environment for high-reliability systems. Whereas automotive or military systems can have redundant circuitry, the size and weight constraints for launching often mean there is no such luxury for satellites. With little or no opportunity to make any physical repairs, however, each unit must operate without maintenance its entire lifetime. This could be up to 15 years, although smaller, lower-cost satellites can allow shorter lives. Satellites also need to be controllable beyond their operational lifetime to permit deorbiting and responsible disposal, avoiding the accumulation of space junk.
As far as commercialization of space is concerned, increased reliability is critical to ensure services can be affordable as well as environmentally sustainable. In general, improving the reliability of electronics systems demands action on design, materials and processes. Where PCB manufacturing is concerned, pressure from the space industry, and the European Space Agency (ESA) in particular, has driven development of IPC-4101E Appendix A on contamination in substrate base materials. This provides supplemental inspection requirements for base materials used in high-reliability PCBs for critical applications, with particular reference to the prevention and detection of foreign material inclusions (FOD) early in the supply chain, effectively ensuring insulation performance comes within a narrower window than needed for typical terrestrial electronics applications. The support of the industry’s leading materials suppliers, including Ventec, helped ensure adoption of ESA’s proposals. Most materials suppliers have been obliged to improve their processes and invest significantly in automation and measures to mitigate contamination and be able to deliver materials that meet the higher specification. It’s important for buyers to specify Appendix A when purchasing materials for space applications.
Of course, many more aspects go into designing and building reliable systems to operate reliably in space. Stresses experienced due to vibrations during launching are among the greatest threats to the integrity of electronics assemblies. In addition, when deployed on-orbit, the absence of atmospheric pressure encourages outgassing if any compounds that can become volatilized are present within the substrate. These can then recondense on the surface of the assembly and adversely affect insulation performance. Thermal cycling is another hazard as the satellite can experience extremely low temperatures when obscured from the sun, rising significantly above 100°C when exposed. With glass temperature (Tg) typically in the range of 200°-250°C, polyimide-based formulas have served the space industry well in this respect for many decades. As system performance demands continue to rise, future generations of these materials must improve on parameters such as dissipation factor (Df) to reduce signal-power losses at high frequencies.
Although mission-critical, enshrining reliability has arguably slowed the adoption of innovative technologies and techniques. The explosion in demand for satellite-based services, however, could accelerate the pace of adoption in the future. On the other hand, the industry rightly continues to evaluate new technologies carefully. Wide-bandgap semiconductors are one example. Gallium nitride (GaN) power transistors have already shown how much smaller, more lightweight, more efficient and cooler running power-conversion circuits can be in numerous applications here on Earth. Those benefits would be keenly felt in space by making future generations of satellites easier to package, launch, maneuver and operate.
Wide-bandgap devices are known to be inherently more radiation-hardened than silicon in some respects, such as total dose and threshold energy. They can be vulnerable to single-event effects (SEE) like single-event burnout and single-event gate rupture, however. Researchers continue to investigate the effects and approaches to mitigate the problems. The NASA Electronic Parts and Packaging working group has published several body of knowledge documents on the radiation capabilities and general performance of wide-bandgap semiconductors for use in space.
While the opportunities are exciting and services hosted from space can help improve quality of life and sustainability here on earth, we would do well to ensure responsible development using durable – not disposable – equipment. The PCB industry can take a major role in ensuring future generations of satellites deliver the required performance and longevity.