Space is vast. How vast is it? Well, that remains an unanswered question. Perhaps we simply don’t have the means to measure it yet, or we have not sent probes out far enough. However, it is more likely that measuring the size of the universe may be akin to trying to pinpoint the location of a particle, while also gauging its momentum. This is due to the fact that the universe appears to be expanding and doing so at an increasingly faster rate. The latest calculated expansion rate or Hubble constant is approximately 46.0 miles (74.03 km) per second per megaparsec.
In contrast to the universe, the space within the craft we design and build to traverse it is at a premium. This is true for all compartments and especially areas of dense electronics, such as control panels. In fact, optimizing the size, weight, and power or SWaP of electronics, PCBAs and components is a major thrust in aerospace systems development. The pursuit of this goal has led to the increased preference for and usage of optical electronics and monolithic microwave integrated circuits (MMICs) as opposed to discrete circuits. Let’s explore these devices in more depth; in particular when and why they should be used aboard spacecraft.
What Are Monolithic Microwave Integrated Circuits (MMICs)?
As with many of the advances in electronics, the military and government were the catalysts for early research to develop processes for building ICs that operated in the microwave frequency range (300MHz to 300GHz). At the time, during the mid-1970s, manual placement of discrete components was predominant. The propensity for human error and lack of precision of this technique was a major contributing factor for the interest in MMICs.
MMICs are highly dense component packages that utilize and process microwave signals internally. Typical materials used to construct these components (which is done by machine and not manually) are GaAs, InP, GaN, and SiGe. The many advantages of these components, as listed below, illustrate why they are preferred for many aerospace electronics roles.
The Advantages of MMICs
- High component density
- Small package size
- Highly accurate internal component placement
- Fast signal propagation
- Low overall cost for large quantities
- High-reliability wire-bonding
The list above clearly shows how the use of MMICs contributes to the push for SWaP optimization for aerospace systems development. Now, there are also disadvantages to the utilization of MMICs that must also be considered. These are listed below.
The Disadvantages of MMICs
- Power capabilities are low
- Fabrication can be costly for small quantities
- Design changes cannot be made during manufacturing
- Custom PCB footprints are usually required, which makes assembly more challenging.
- Rework is not possible.
- Trimming, which is used to compensate for manufacturer variations that affect component parameters, is a problem for MMICs. It is very difficult or impossible to implement.
As this list indicates, opting to use MMICs does come with some baggage, much of which affects the building of your boards by your contract manufacturer(CM). Armed with the key advantages and disadvantages of MMICs, we can determine when they should be deployed for our aerospace applications development and why this is done.
Using MMICs for Aerospace Applications
When developing a PCBA or electronics device for an aerospace entity, the use of optics and microwave components may be requested or preferred. In other cases, the design criteria may not extend to the component or packages and the choice of whether to use MMICs will lie with you. Before opting to do so, you should be clear about whether that is the best choice. The table below, which defines situations in which MMICs should be used and why they can assist you with the decision.
If one or more of the “When to Use” entries above is true for your design, then the usage of MMICs is probably the best choice for your aerospace electronics development. However, you need to work closely with your CM to ensure that your custom design can be built as desired. In some cases, you may have to make trade-offs to utilize these devices.
|Tempo's Custom Avionics for PCB Manufacturing Service
For most aerospace electronics development projects, optimization of the SWaP parameters is a primary objective. In those cases, MMICs are usually the best choice for signal processing. At Tempo Automation, we employ a smart factory and advanced manufacturing processes and control to build boards that meet or exceed the high standards for products intended for space flight.
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.
If you are ready to have your design manufactured, try our quote tool to upload your CAD and BOM files. If you want more information on using monolithic microwave integrated circuits (MMICs) for your aerospace PCBA development, contact us.