The aerospace industry requires printed circuits with high reliability in extreme conditions, such as satellite PCBs that must perform in space or circuits on a commercial passenger jet.
High temperature laminates, copper and aluminum substrates can perform very well in these challenging environments.
THE FOLLOWING REPRESENTS A FEW OF OUR AEROSPACE APPLICATIONS:
• Radio communication systems
• Radar installations
• Power converters
• Power supplies
• LED lighting systems
• Control tower systems
• Temperature sensors
• Audio interface applications
• AMRAAM (Advanced Medium Range Air to Air Missiles)
• APU (Auxiliary Power Units)
• ASRAAM (Advanced Short Range Air to Air Missiles)
Aerospace PCBs must be designed and manufactured to the highest quality standards incorporating specialized features as required.
GUIDELINES MUST BE FOLLOWING IN AEROSPACE PCB:
Select high quality materials:
In the aerospace sector, reliability and durability are two requirements that cannot be ignored. In this type of applications, the circuits must operate continuously and without incurring malfunctions for long periods of time (generally from a minimum of 5 years up to 15 years or more), considering that maintenance interventions are not possible or have exorbitant costs. The general rule is to use high quality materials and components, which remain available on the market for long periods of time.
A very common alternative to copper is represented by anodized aluminum, capable of solving many of the problems related to heat dissipation. In fact, anodized aluminum offers a thermal conductivity from 5 to 10 times higher than traditional materials such as FR-4, with a thickness of ten times less. Furthermore, it is able to transfer heat in a exponentially more efficient way than a conventional PCB and minimizes the effects of heat-induced oxidation.
Use heavy copper technology:
Heavy copper technology, with copper thicknesses ranging from 2 to 6 oz/ft2 (or more), allows heat dissipation in a natural way, without requiring additional cooling systems even in the presence of high intensity currents. Many manufacturers suggest combining heavy copper solutions with the inclusion of numerous thermal vias to further improve heat dissipation. Figure 1 shows the detail of a multilayer PCB with heavy copper layer.
Provide an excellent thermal management:
As mentioned above, aerospace PCBs must ensure excellent heat dissipation, without requiring the use of external heatsinks. In addition to heavy copper technology and the extensive use of thermal vias, special solutions based on materials such as Pyralux AP, FR408, and other metal materials and components can be used. Compared to traditional PCBs, it is also preferable to increase the distance separating the components, which can thus have a greater volume of space for heat dissipation.
Use conformal coating:
PCB finishing materials should be chosen to withstand the extreme operating conditions under the harshest operating conditions. The main conformal coating techniques include electrolytic nickel gold, ENIG (Electroless Nickel with Immersion Gold Coating), chemical silver, HASL (Hot Air Solder Leveling) and lead-free HASL. The application of the conformal coating provides protection against heat, humidity, water and vibrations, all conditions that can be encountered in aerospace applications. Conformal coating should also be followed by the application of acrylic-based spray in order to protect the final printed circuit from contamination or accidental short circuits. Figure 2 shows the detail of a PCB with HASL conformal coating.
AEROSPACE APPLICATIONS MOSTLY USE OF FLEX AND RIGID-FLEX PCBS:
Very common in satellite and avionics systems are flexible and rigid-flexible printed circuit boards, with the difference that, compared to industrial or automotive applications, they are mainly manufactured with polyamide instead of FR-4. This material has the characteristic of easily adapting to small spaces, it is very light and resistant to heat and chemical agents and guarantees a high durability.
Flex and rigid-flex PCBs are widely used in the aerospace industry by virtue of their ability to adapt to small spaces, high resistance to vibrations, shocks, temperature and external agents, excellent mechanical and electrical connection, low weight. Rigid-flex PCBs are composed of a combination of rigid and flexible printed circuit boards, permanently connected to each other. The correct use of flex and rigid-flex PCBs offers an optimal solution for difficult and limited space applications. This technology offers a secure connection between the various parts of the circuit, ensuring both polarity and contact stability and reducing the number of connectors.