What Makes Aerospace and Defense Electronics Different from Regular PCBs?By ZM Peterson • Nov 3, 2020
Every industrialized country has a responsibility to maintain its own aerospace and defense electronics manufacturing capabilities. For countries like the US, this particular industry is a huge growth driver for many local PCB manufacturers, design firms, and engineers. One The commercial space revolution will continue to push growth for domestic electronics as the size of the space industry is expected to increase by 8x during the next 30 years.
Aerospace and defense electronics systems carry strict reliability and lifetime requirements that put consumer electronics to shame. So what brings about this level of reliability in military products? Is it the design or manufacturing? In reality, there are elements of both that help make aerospace and defense electronics so rugged. Let’s look at some of the specific differences that make aerospace and defense electronics so tough.
Military PCB Design Standards
PCBs designed for defense and aerospace systems, as well as components used in those PCBs, must meet strict reliability and lifetime standards. Some of these standards go beyond the IPC standards, with one exception being the IPC-6012 Class 3A. Unlike the ISO AS9100 standard, which is a quality management standard for aerospace systems, MIL-SPEC standards on defense electronics systems specify performance and testing requirements. Here are some of the important MIL standards:Performance Standards
- MIL-PRF-31032. This set of standards applies to PCBs for defense systems.
- MIL-PRF-38535 and MIL-PRF-19500. These standards specify performance requirements on integrated circuits and microcircuits used in aerospace and defense electronics.
- MIL-PRF-55342, MIL-PRF-123, and MIL-PRF-55681. Both of these standards specify general requirements on resistors and capacitors, respectively.
In addition to performance and reliability standards, the following standards specify test methods for evaluating reliability.Testing Standards
- MIL-STD-202G: testing procedures for standard electronic and electrical components.
- MIL-STD-750-2: testing procedures for semiconductor devices.
- MIL-STD-883: testing procedures for microcircuits.
Obviously, the MIL-SPEC standards are broad and cover much more than just PCBs. Once you’ve identified the relevant standard for your design, you’ll have to drill down to how it affects your particular system.
Because the MIL-PRF standards are performance-based, they necessarily don’t specify limits on design choices. As long as your design can meet the performance requirements, then it can be put into service. With this in mind, let’s look deeper at what you can expect from a MIL-SPEC compliant design.
Design Points for Aerospace and Defense Electronics
The design points presented here are all about ensuring mechanical and electrical reliability, and these points can be found from MIL-PRF standards (primarily MIL-PRF-31032). A board designed to these standards is generally also designed to IPC Class 3A, which is the highest highest IPC reliability standard. We stick to the following parameters:
Some other important points that help ensure signal integrity include:
- Isolate high and low frequency circuit blocks and components, just as you would isolate signals in an RF PCB layout.
- Use best practices to prevent crosstalk.
- Isolate clock signals from external interference within the board.
- Use thermal compounds to aid heat dissipation from high power components.
- Use acrylic-based sprays for conformal coatings, which will help prevent contamination, accidental shorts, or other problems.
Use a Compliant Design Firm and Manufacturer
The specifications listed above are just a summary of important performance requirements for aerospace and defense electronics systems. For more information on standards that may be applicable to your design or organization, you should refer to the Defense Standardization Program.
The one aspect we haven’t touched on in this article is the matter of compliance, simply because it’s a deep enough topic to deserve several of its own blogs. Anyone is free to design anything they like on paper, but the moment you try to manufacture it, assemble it, share it, sell it, or import/export it, you might fall under the purview of a set of regulations. Principle among these are:
- Defense Federal Acquisition Regulations (DFARS)
- International Traffic and Arms Regulations (ITAR)
- Export Administration Regulations (EAR)
Even if you’re not a registered defense contractor or regularly supply DoD contractors, you may need to obey ITAR regulations for electronics design and manufacturing certain activities. Note that it is not the responsibility of your manufacturer to make that determination; you or your contract design firm should determine whether ITAR registration with DDTC is required.
Whether you’re a prime vendor for the US military or you’re a small company that might need to design export-controlled equipment, the right design firm can help you navigate these regulations. For PCB manufacturing and assembly of aerospace and defense electronics, not all design firms or manufacturers are compliant with ITAR regulations. When you need to design or manufacture your next PCB, be sure you use a design firm that can help you stay compliant with these important regulations.
The experienced PCB design and layout team at NWES has a track record of working with aerospace and defense electronics companies. We’ve designed advanced RF systems, high speed backplanes, power systems, IoT devices, and much more. We’ve also partnered directly with EDA companies and multiple ITAR-compliant manufacturers, and we can help our clients get through the PCB manufacturing process with ease. Contact NWES for a consultation.