If you bring up the topic of remote sensing, you are likely to get some curious responses. For example, that device used for channel surfing may come up. Or you may get some reference to seeing things in other locations through mental targeting. Although these are somewhere in the ballpark, they are not correct. Remote sensing, which can be traced back to the mid-nineteenth century, is more accurately described as the practice of looking at an object from a distance to gather data and information for its analysis. Today, this activity is a primary function of many aerospace vehicles, especially satellites.
The ability to “sense” or gather information about an object, without direct physical contact is performed by specialized devices known as sensors. Just as with other components used for aerospace applications, there are restrictions and requirements on what sensors can be used. These constraints are due to the unique space environment in which aerospace vehicles operate that place high expectations on the quality and reliability of PCB sensors. In order to devise a plan of design optimization to meet these objectives, it is necessary that we understand how PCB sensors for aerospace are utilized.
How Are Sensors Used in Space?
The most common sensor functionality is to produce an image of an object. And, undoubtedly, the ability to look down at the earth from space is fantastic and forms the basis for well-known and readily available satellite services, including satellite TV and GPS. Yet, there are many other uses for PCB sensors in aerospace applications. As every mission is different, the types of sensors and their applications can vary greatly. However, we can categorize some common PCB sensor functions based on environmental conditions, as is done below.
Interior PCB Sensors
The internal environment of an aerospace vehicle or platform will to a great degree depend upon who and what is aboard. For example, for satellites and other unmanned spacecraft, life support systems, including maintaining room temperature, are not required. However, internal equipment, especially computers, peripherals, and communications systems, need to be protected from the environment. And for rockets, most of the space is taken up by fuel, which can reach extremely high temperatures and its pressure must be monitored. Throughout this diverse internal area, sensors are installed to monitor the spacecraft’s systems and operations. Common sensors used include the list below:
Common sensor functions:
Pressure monitoring of auxiliary power units (APUs)
Flight controls force measurements
Position and orientation measurement
External PCB Sensors
The exterior environment for space vehicles may not be as diverse; however, it is much harsher. Not only is the hull exposed to extreme temperatures and strain, but also various types of radiation. Radiation effects and atmospheric conditions depend on where in the atmosphere the PCB sensor is located. For orbital vehicles, such as satellite technology, temperatures can range from extreme cold to hot and atmosphere from dense with high weather activity to gaseous. Typical external sensors perform the following functions.
Common sensor functions:
Optical capture (still or video)
Mechanical stress measurements
The sensor functions above are not exhaustive; however, they do represent functions that sensors will likely perform on space vehicles. Whether internal or external, the high standards of performance placed on PCB sensors for aerospace require special design considerations as discussed below.
PCBA Manufacturing for Extreme Environments - Part 1
How to Optimize PCB Sensors for Aerospace Systems
Whether on or in aerospace systems, PCB sensors are called upon to measure a wide range of parameters. However, in making meaningful usage of the acquired data most PCBs require signals in voltage, current or temperature format. This commonality allows us to define a set of design optimization techniques, listed below, that are broadly applicable.
- Know and follow applicable standards for PCB Design
The aerospace industry is heavily regulated and staying on top of all the standards is indeed challenging. For example, it is common for boards to have to adhere to the requirements for IPC class 3, 3A and above. Failing to do so will undoubtedly lead to long development cycles, issues with getting your PCBAs and devices approved and unnecessary and possibly quite significant ROI losses.
- Design for the environmental conditions
The environment in which your board may need to operate should be a primary design consideration as it will directly impact many design decisions. For example, materials, component requirements, board flexibility, and other parameters can be impacted by extreme temperature cycling. Whether mounted internally or externally PCB sensors are susceptible to radiation. Therefore, you should always consider radiation-hardened electronics for all aerospace applications. Additionally, low gas off sensors should be used.
- Select the best components
Component selection is one of the hardest tasks for aerospace engineers. One reason for this is the current transition from the more traditional rigidness over acceptable components to the more flexible COTS solution. For sensors, a good option may be to choose Automotive Grade (AEC-Q100) parts since they are higher in quality than standard COTS parts, and avoid packages with fine pitches, such as BGAs tighter than 0.25 to 0.5mm, to withstand the harsh environmental conditions of space. Older components that have been proven is also a good option.
- Employ radiation hardening
- Institute DFM for Aerospace Technology
Following the DFM rules and guidelines of your contract manufacturer (CM) leads to the most efficient PCB manufacturing process and best-built boards. For aerospace PCBAs, including sensor boards, this is more critical as there are additional regulatory requirements, the highest quality mandates, and tighter reliability control.
|Tempo‘s Custom Avionics for PCB Manufacturing Service
One of the most important electronics devices on or in aerospace platforms are PCB sensors. These boards assist in virtually all system operations. Therefore, they must be designed and manufactured to exhibit the highest level of performance and consistency. At Tempo Automation, we are experienced in building PCB sensor boards for the most challenging missions undertaken by man. And we will work with you to ensure that your boards are space-ready.
And 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 Designer or Cadence Allegro user, you can simply add these files to your PCB design software. For Mentor Pads or other design packages, we furnish DRC information in other CAD formats and Excel.