If you asked my father, he would probably say that I rarely listened to the advice that he constantly gave me and my siblings as we traversed the minefield from childhood to adulthood. That is not true, of course. I actually used his words of wisdom as a constant guide. One saying, in particular, has always been a source of motivation for me. That is to “always strive to be the best at whatever you do.” I do not know if there is any better advice that you can give anyone, as you should always try to optimize whatever activity you are engaged in.
Man escaping the boundaries of the earth
Similar motivation has certainly been a foundation for the creation of the orbital and spaceflight systems that have allowed us to break the boundaries of the earth. This includes the development of PCBs that drive the electronics and typically control mechanical and pneumatic operations. Space poses specific challenges for PCB manufacturing that must be overcome to ensure that aerospace systems can safely and reliably accomplish their missions. For board fabrication, these are primarily related to maintaining structural integrity for varying environmental conditions. PCB assembly is not as obvious. However, after defining the development obstacles, we will be able to define a regimen for optimization of aerospace PCB assembly that meets the challenges of space.
The Challenges of Aerospace Systems Development
Space is a challenging environment. It can seem serene, but it can also be quite dangerous. Temperatures can range from over one thousand degrees Fahrenheit to -455°F, which places tremendous mechanical stress on space vehicles. Additionally, there is the possibility of collisions from various sized space debris. These and other hazards can be classified as external challenges for orbital platforms and spaceflight vehicles. There are also obstacles that threaten the internal systems that must be contended with for aerospace systems development, as listed below.
Radiation is a concern for all vehicles and systems in space. This is more due to its disruptive potential for wireless communications than for excessive concentration, which can be a biological problem.
RF radiation can also be a significant concern. At atmospheric levels within the ionosphere, this hazard is the greatest.
Vibration and mechanical shock
Research and development (R&D) into reusable rockets for space travel that will greatly reduce the vibratory effects of launch and landing are in the works. Even with these advances, the energy required for launch will probably remain a source of substantial mechanical stress on the space vehicle, as well as a source of vibration for internal devices and systems for some time to come.
As space is typically limited within space vehicles and requires temperature and pressure control, there are fewer options for heat dissipation than is typically the case for earthbound systems.
Although extreme temperatures are typically associated with external obstacles to aerospace system deployment, this can also be a concern for internal devices. For example, temperatures near the engine, which is typically monitored and controlled by electronic devices, can be several thousands of degrees Fahrenheit.
The above hazards must be overcome for the successful deployment of space vehicles. For board fabrication, this can be addressed by selecting the right materials that will ensure safe operation in the thermal, electrical, and mechanical environmental conditions. PCBA can also be addressed as discussed below.
Optimizing Aerospace PCB Assembly to Meet the Challenges of Space
It is always important that your design incorporates good DFM guidelines. The benefits to PCB development cannot be overstated. However, the quality and reliability mandated for aerospace applications are much higher than most commercial applications. This is due to the regulatory requirements that are generally applicable to all aerospace development, as well as challenges that are specific to your space system and its deployment. These mandates demand that you select a qualified contract manufacturer (CM), apply DFM targeted at aerospace PCB development, employ design for assembly (DFA) to meet or exceed IPC class 3 standards for electronic assembly, and ensure solder joints and component locations remain intact in space.
One of the greatest challenges that your boards will encounter onboard a spaceflight vehicle involves radiation. Whether ionic or RF, radiation can wreak havoc on boards by introducing electromagnetic interference (EMI) that can distort signal quality, change impedance, and introduce crosstalk on traces. Therefore, your design should be optimized for power integrity, incorporate special considerations for signal integrity, and ensure that only high-performance components are used. To facilitate this process, you should employ risk analysis that conforms to AS9100, includes monitoring and traceability of the supply chain, and incorporates appropriate add-ons during assembly, such as shielding.
The best means of combating vibrational or mechanical stress impacts that may impact your board are by your material choices; however, if your board is flex or rigid-flex, these impacts may be profound and could result in your board exceeding its bending limits or components dislodging. Making sure that your PCB layout only has planar component placement or requesting that supports be added can aid assembly in assuring that good solder joints are made and components are well-secured. For heavy components or when planarity is not possible, it may be necessary to have your CM use stiffeners or add extra adhesion to your flex-type boards during assembly.
All matter has a temperature at which it will lose its form or shape. This not only applies to board materials but components and solder joints as well. Under normal circumstances, this should not be an issue. Just the same, it is probably best to opt for components that have made it onto the NASA Parts Selection List (NPSL). If commercial-off-the-shelf (COTS) components are utilized, you may need to perform an AS9102B test to ensure the component meets aerospace industry standard.
Designing circuit boards for aerospace applications is not the same as for most other commercial applications. First, there are the industry standards that must be satisfied. Then, there are specific requirements based on the type of space platform and whether it is orbital or for space flight. Likewise, PCBA is not the same. In order to optimize your aerospace PCB assembly, you need a qualified and certified CM like Tempo Automation.
|Tempo‘s Custom Avionics for PCB Manufacturing Service|
Our experience in PCB manufacturing for aerospace applications is known in the industry and our commitment to creating high-quality quality boards that fully incorporate your design intent is unmatched, as is our speed for quotes and turnaround time.
To help you get started on the best path, we furnish information for your DFM checks and enable you to easily view and download DRC files. If you’re an Altium user, you can simply add these files to your PCB design software.