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Board Layout

Scope and Description

This topic page covers board layout of printed circuit boards (PCBs) for spacecraft electronics. This task is where the physical implementation of a schematic circuit design is developed. This typically involves capturing all component package footprints, importing the schematic design/netlist, defining the PCB outline and mechanical interface features, designing the PCB stackup, defining design rules, placing the components, routing the traces, and generating design files for manufacturing. Board layout errors are usually identified in manufacturing and test, which makes detecting them before flight relatively likely; however, the schedule impact of these errors can be substantial - making good design practices an important consideration for smallsat teams on tight schedules.

Resources under this topic area are primarily design guides and CAD tools for PCB layout.

Best Practices and Lessons Learned

  • Prototype challenging sub-circuits early with "breadboard" PCBs. Circuits that are high in speed, power, noise sensitivity, manufacturing complexity, or density should be laid out on a simplified PCB with ample test points to enable early evaluation. This will allow you to ensure manufacturability and performance before investing the time and money in manufacturing and test of the complete system. The root cause of any layout issues will be much more challenging to isolate and debug when integrated with the rest of the system on a higher density PCB.
  • Conduct a rough density study very early in the design process. Build out a bill of materials (package type and quantity) for each sub-circuit, populate the layout without traces, and work with your mechanical design team to collaboratively optimize the board outline, mechanical/thermal interfaces, and stackup thickness.
  • Minimize use of microvias, buried vias, and non-standard stackups as much as possible. These design elements will result in significantly more expensive and long-lead PCBs.
  • Avoid being over-zealous about choosing or adhering to the most stringent board specifications, especially for boards with dense part populations or high-density parts, such as reconfigurable FPGAs. This can lead to significant increases in cost and risky features such as additional board layers and microvias.

Resources

Software Tool
KiCad

This free, open-source electronic design automation (EDA) suite can be used for schematic capture, printed ... circuit board (PCB) layout, and 3D modeling of the completed PCB. This suite includes add-on design tools for developing engineering drawings, calculating various component metrics, and plugins for integration with third-party tools.

Software Tool
Altium

Altium Designer is a software tool that encompasses the entire PCB development process - from schematic ... capture to assembly. Altium is a powerful tool that is appropriate for complex designs and includes features comparable to Cadence's offerings (OrCAD and Allegro) for electronics design.

Software Tool
Autodesk

Autodesk Eagle is a software tool for performing electronic design and layout. Refer to their website ... for more information or a free download for hobbyists.

Software Tool
LibrePCB

This is a free, open source software tool for schematic capture and board layout. Compared to other free ... tools, LibrePCB focuses on easy component library management and version control. However, it is less powerful and therefore not as appropriate for complicated designs.

White Paper
NASA

This site provides a high-level overview of NASA guidance, recommendations, and assurance methodology ... related to printed circuit boards (PCBs). This web page references other useful resources, including industry standards for PCB schematic capture, design, and board layout.

Software Tool
Cadence

Allegro is a powerful software tool for PCB design and analysis that is appropriate for complex and high-reliability ... designs. This tool is offered as part of an electronics design suite from Cadence which includes OrCAD for schematic capture and PSpice for circuit analysis.

White Paper
Texas Instruments

This two-part document first provides a theoretical overview of the challenges of high-speed board design ... and then concisely presents design guidelines to mitigate these problems.

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