The highest level of reliability, as well as the smallest possible error margin, is required for Aircraft PCB. While the majority of circuit boards out there are made to withstand standard operating circumstances, aircraft can expose PCBs to hazardous situations such high heat, extended operation, chemicals, radiation, and more. Therefore, restrictions on the circuit boards are particularly wise in order to safeguard the objectives of space travel, aircraft, satellites, as well as the national defense.
Quality assurance also plays an essential role while designing the circuit boards for the aircraft. Three most crucial factors for designing the circuit board for aircraft are covered in our article.
Aircraft PCB Industry Standards
IPC Class 3 Standards as well as AS9100D Certification for Aircraft PCBs
Any industry standard which directs the design, the development, as well as the manufacturing of products within defense, space, and aircraft, like it is prepared by the AircraftQuality Group is referred to as AS9100D certification.
It plays an important role throughout all PCB requirements for aircraft, comprising fabrication as well as assembly, even though it directs procedures at every level of the whole process.
The AS9100D certification provides guidance for five essential aircraft as well as aircraft processes:
- Quality control procedures
- Management duties
- Resource management
- Realization of the product
- Improvement measures
The most recent iteration incorporates other success criteria in along with the original AS9100 certification, like product safety, human error, risk-based thinking, as well as preventing fake parts.
Although it is not needed by law, AS9100D certification can be regarded by many as a vital procedure in circuit board for aircraft since it guarantees stringent testing as well as the best caliber circuit boards. In order to fulfill their goals, businesses in the aircraft industry must exclusively work with recognized manufacturers to get the best possible results.
It is quite similar to the ISO9001 standards but has extra PCB requirements that are unique to aircraft. For technology created for life-threatening situations, like military use as well as aircraft, the highest possible tolerances as well as life spans are essential. This classification does not accept any errors, not even visible ones.
Naturally, owing to inspection as well as precision, both AS9100D certifications as well as Class 3 IPC standard necessitates substantially slower manufacturing schedules. This results in lengthier production times and higher costs, but it also produces the best outcomes.
Thermal Management in Aircraft PCB
Because of the harsh settings they operate in, aircraft printed circuit boards must perform under special circumstances. For these boards to function, high temperature circuit board techniques are necessary.
The temperature for glass transition must be over 170°C for high temperature printed circuit boards to function, with the constant heat load being 25°C just below temperature of transition. Heat distribution, as well as materials designed for the thermal conductivity, are necessary for this.
Conduction and convection are the two methods used to distribute heat. These could be controlled using heat sinks, which channel heat through large-surface-area corrugated structures, including copper- or aluminum-backed heat sinks.
By increasing its current-carrying capacity, lowering the amount of heat generated, and improving heat dissipation, materials like heavy copper become suited to handle extreme temperatures.
Furthermore, materials including FR-4 have characteristics like reduced ash or smoke generation, chemical resistance, and flame resistance.
Design Guidelines for Aircraft PCB
These systems share many characteristics with Printed circuit boards for RF high-frequency applications since radio communication present in the higher band forms an essential part of them.
Due to the increased risk of the radiation exposure when operating at a high altitude, PCBs as well as other types of electronic components should be designed to withstand levels of high radiation for lengthy time periods without experiencing any harm.
Utilize heavy copper tech
Even with the availability of the high-intensity currents, the heavy copper tech, which has copper thicknesses of at least 2 to 6 oz/ft2, allows heat to dissipate naturally without requiring additional cooling systems. Many manufacturers suggest combining the solutions of heavy copper with the installation of numerous thermal vias to further improve heat dissipation.
Choose high-quality materials
Inside the aircraft sector, there are two requirements that need to be met: dependability and durability. Given that these kinds of applications make maintenance interventions very expensive, the circuits should indeed operate continuously and faultlessly for lengthy time periods (often 5 years minimum to about 15 years).
The standard practice is to use high-quality components and materials that have been widely accessible on the marketplace for a long time.
Implement conformal coating
These materials for PCB finishing must to be chosen to withstand the most difficult working conditions. Some popular conformal coating techniques are ENIG, electrolytic nickel gold, chemical silver, lead-free HASL and HASL.
Characteristics of Aircraft PCBs
PCBs for aircraft come with several exceptional features.
Resist extreme temperatures
PCB makers utilize high temperature aluminum, copper, as well as aluminum laminates and substrates to make PCBs that can withstand the harsh temperatures that electronics are subjected to in space. Thermal compounds were additionally employed to prevent heat from spreading to other electrical components.
In order to promote the thermal dispersion of heat, space is often utilized.
Shock absorption
Mechanisms for a shock absorption include using thermal compounds that lessen the effects of fluctuations and using designs that keep components in place.
Radiation
Radiation risk is reduced through the utilization of some materials as well as by making the components smaller.
Radio frequency
Transmission lines are made as short as feasible and shielding is strategically placed on the Circuit board to guarantee that these signals are transferred without deterioration. For communication to take place in our aviation sector, radio waves were necessary. No matter the circumstance or surroundings, these signals must be sent.
Adhere to the rules and regulations for aircraft
These standards must be taken into consideration by the aviation PCB manufacturer. These standards were divided into groups according to the different Circuit board manufacturing procedures that they prioritize.
Aircraft Layout and PCB Design
Aircraft PCBs must take a number of important layout and design factors into account in order to become more durable. The proper mil-spec components must be used. Among other crucial elements, also present is the necessity to design additional cushioning for such currents.
Therefore, increasing the current inside the PCB’s circuitry should be the initial step. Design the Circuit board to carry an additional amp to help out if the remaining two fail.
For drilling the other, use aspect ratio for managing the ratio in-between the empty boards and the vias. The appropriate ratio is 1:10. Increase this to, let’s say 1:15, and reliability is likely to suffer. Make sure to keep the ground and power planes apart in the design. The high-frequency as well as low-frequency ones must be kept separately.
Higher frequency oscillating components are more likely to produce waveforms when used. These could have an impact on lower frequency components. Protect all clock signals and make sure they are in good condition. Utilizing aluminum as well as other materials with properties similar to aluminum allows for this.
The impedance calculations are then verified. Pre-layout simulations will also be necessary because it is nearly impossible to evaluate aircraft applications within typical settings. To make it feasible, you should incorporate simulation software. This will enable you to get suggestions about potential changes. Thus, it aids in ensuring that the PCB performs at its best.
Steps Involved in Aircraft PCB Assembly
Application of solder paste
The board is covered with solder paste. To make a variety of sizes and shapes, stencils are employed. This guarantees that application of this solder paste correctly.
Arrangement of the parts
This procedure is automated. It makes it possible to position components where they are needed on the board. Robotic machines come handy here and are employed in the assembly of PCBs. They are precise because they use design software.
Solder paste needs to be properly placed and solidified once the components have been assembled. The elements can adhere onto the board. The PCB for aircraft is passed via the conveyor belt. The belt travels within the reflow oven. This oven should be up to commercial standards. This extra solder paste melts more quickly as a result.
Insertion of through-hole components
Components for aircraft PCBs require through-hole insertion. Now, t his is because the vast majority of PCBs utilized in this sector are multilayered. Signals can pass through one of the sides of the circuit board onto the other thanks to the usage of thru-hole technology.
Final examination
Functionality as well as electrical properties are examined at this level. These include checking the current and the voltage. Additionally, its signal output must be examined. This is significant in light of the dangers that airplanes face. There may be catastrophic flaws.
Conclusion
Circuits used in aircraft applications must have the ability of withstanding as well as absorbing significant vibrations and shocks in addition to being exposed to extremely high temperatures. They also share a lot of characteristics with PCBs that serve high-frequency applications.
