Boards/Backplanes

Flex PCBs in satellite designs and applications

3rd December 2021
Beatrice O'Flaherty

In the emerging tech world, most high-end electronics devices are relying on Flex PCBs (flexible printed circuit boards) for their performance. Ken G. from Technotronix discusses flex PCBs, especially in the context of both their application and designs in satellites.

Flex PCBs have very thin substrates with high physical flexibility and tensile strength. They are extensively used in medical devices, aerospace, and satellite applications.

Flex PCBs can be single-sided, double-sided, or multilayer circuit boards. When the design requires specific impedance, high component density, or extra shielding then multilayer Flex PCB provides an effective solution. The substrate material of a flex PCB can be very thin but capable of consistent etching.

This removes the need for traditional wiring with connectors. Flex PCBs display many design advantages like excellent bending, resistance to vibrations, compact design, and so on. During PCB manufacturing, flex PCBs are good at heat dissipation and airflow.

The technology reduces the assembly cost by removing the need for complex connectors in the design. Thus, Flex PCBs are important in advanced electronics applications like healthcare equipment, military, and satellite designs.

The next sections cover the basic elements of a satellite communication system to understand the importance of Flex PCBs in such a system. A satellite system includes a transmitter, a satellite, and a receiver. ‘Uplink’ is the communication between the transmitter on the earth with a satellite, while ‘downlink’ is the communication between a satellite and a receiver on the earth.

Satellites are now the mode of communication used in TV transmission, weather forecasting, telecommunication, emergency risk management, etc. All these applications demand high precision and reliable PCB assembly to be used in a satellite design.

Flex PCBs are the best choice in a satellite design due to several apt features like:

  • Lightweight and less space consumption. A rocket has to take off with a satellite against Earth’s gravity demanding a massive power to thrust. Flex PCB with reduced weight and smaller size is surely an advantage in such an application. The thin substrate used in multiple layers of a Flex PCB decreases the overall board weight significantly.
  • The adaptability of this circuit board is an essential requirement in a Satellite design. Flex PCBs’ versatility assists in bending the equipment to fit in any small area of a spacecraft and are often used in expendable space equipment.
  • Consistency in operation at extreme conditions is possible in a Flex PCB circuit. Satellites are exposed to high pressure and vibrations during take-off and also while orbiting in space. So, the circuits may get damaged due to these tremendous vibrations. Flex PCBs are built to twist and bend while working in severe conditions. This greatly reduces the failure rate of the satellite equipment.

Flex PCBs are best suited for satellite applications yet certain considerations are required while designing for an optimised performance such as:

  • The material selection that can operate in very high temperatures (more than 120°C) is critical while designing a satellite circuitry. Though the PCB may not be directly exposed to the outside space conditions, the circuit board undergoes a lot of vibration and pressure. Thus, choosing the right Flex PCB material is highly recommended.
  • The selected material needs to have an optimal thermal resistance to avoid outgassing. This effect happens when trapped gas is released from the PCB when exposed to extreme heat or vacuum conditions, much similar to the space environment.
  • The tensile strength of a Flex PCB is an important feature to be considered as the satellite circuitry is prone to bombardments while orbiting in space. The bendability of the PCB has to be thoroughly tested before designing the final product to be sent into the space.

With so many advantages of Flex PCBs suitable for satellite applications, the cost will be higher than the rigid PCBs available in the market. We can reduce the overall cost of flex PCBs by following certain suggestions like keeping the PCB layer count to the least required, efficiently designing the panel that includes multiple individual PCBs, using stiffeners of uniform thickness, limiting the number of vias, and so on.

One of the major concerns in satellite application is the extreme operating condition that results in the turbulent vibration of the PCB assembly. This can end up with failures such as track damage, broken joints, damaged components, and the delamination of the PCB. This in turn causes performance issues.

There are certain suggested design guidelines to reduce the vibration effects in a satellite PCB assembly such as the following:

  • Choosing copper-clad laminate with better peel strength
  • Avoiding solder mask on PCB that may compromise on performance due to outgassing.
  • Providing conformal coating on the external component layer to avoid electrostatic discharge during satellite launch.
  • Copper balance and symmetrical component placement to avoid mechanical distortions like warp, twists, and Bows.
  • To avoid heat effects, it is recommended to use the critical components at derated values. The current transmission through traces should also be lowered accordingly to avoid extreme heat damages.

By following all these suggestions along with the inherent advantages that are already discussed, Flex PCBs are proving to be the undisputed choice for all Satellite applications. It is evident that the Flex PCB materials like Kapton offer lightweight and resistant to vibrations. Most Flex PCB materials display features like flexibility and tensile strength that are appropriate for harsh operating conditions of a satellite application.

The PCB design is expected to work precisely with an extensive lifespan, as fixing or replacing a faulty circuit is not feasible in satellite applications. So, the importance of Flex PCBs is obvious! Satellite technology is now becoming a growing opportunity for many PCB Manufacturers. Bringing out a compact and reliable Flex PCB design for a Satellite application can be simpler by collaborating with an experienced PCB assembly provider.

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