Aerospace PCBs are carefully manufactured
to withstand harsh environment in space. How these circuit boards are
assembled? In this article, you are going to read how aerospace PCBs are
incorporated in vital systems on aircraft, spacecraft and satellites. They
control navigation, and communication along with managing engine functions and
instrumentation which are irreplaceable.
The aerospace & defense PCB market is
predicted to garner $1.38 billion by 2024, according to a report published by
The Business Research Company.
Aerospace harsh environment demands a
unique approach to PCB design and manufacturing. The high temperatures in
proximity with jet engine exhaust, radiation exposure significantly impact
aerospace applications.
By quality and safety standards for these
assemblies I mean, because a failure can end up with catastrophic results. You
will also read some of the most relevant industry standards and certifications
such as IPC Class 3 (highest level of reliability for electronic assemblies)
and AS/EN 9100.
Why
High Reliability is Essential in Aerospace PCB Assembly?
There is no room for error when it comes to
aerospace applications. While a defective part in, say, a commercial product
may only cause inconvenience to the user; if an aerospace PCB assembly fails it
can have devastating results. That is why having the highest degree of
reliability in this specific area becomes ever more essential.
Let’s look at the reasons:
Safety of Life and Property:
Aerospace systems, from passenger jets to
military aircraft and spacecraft, carry precious human cargo and represent
billions of dollars in investment. A single PCB failure can trigger a cascade
of events leading to:
1. A critical system shutdown
2. Loss of control
3. Structural failure.
For instance, a malfunction in a flight
control system's PCB can result in a plane crash. Subsequently, a minor failure
in a spacecraft's navigation PCB can make the safety of astronauts vulnerable.
Statistics from the Aviation Safety Network https://asn.flightsafety.org/database/ reveal that in 2022 alone, there were 42 accidents involving commercial
passenger aircraft, highlighting the potential consequences of even rare
failures.
Extreme Environmental Conditions
Aerospace PCB assemblies must endure in harsh environment. Reliability aspects of
key challenges come into a few different categories:
-
Temperature Extremes: Whether it
be the blistering heat (over 300°C) or cold (-260°C), aerospace PCBs must
operate within an enormous temperature spectrum. Such extremes of
expansion and contraction result in stress on components lead to fatigue
failure caused by vehicle vibration stresses over time or bad solder
joints due to thermal cycling. Therewithal, High temperatures serve to
hasten the breakdown component and thus speed up its end-of-life of PCB.
-
-
Intense Vibrations: Spacecraft
systems are subjected to very high levels of vibration, often greater
than 15G, which can stress solder joints and connectors so much that they
crack or fracture.
-
-
Radiation Exposure: On orbit
individual high-energy radiation particles zap electronics. This
radiation can change the electrical behavior of individual components or
trigger permanent damage and lead to data errors.
-
-
Vast Pressure Changes: A rapid
pressure change can challenge the bond of air trapped within a PCB
laminate and lead to delamination (fiberglass layers not sticking
together).
Cost of Failure:
In an aerospace application, the costs of
failure are far higher than simply replacing a faulty PCB. A single PCB failure
in a spacecrafts critical system can spell the end of a multi-billion dollar
mission.
If a PCB inside an airplane is failing, it
will cause airlines to fail financially with multiple flights being canceled
and delayed. For the most part a filed PCB failure would cause all to seek and
possibly have costly search tasks.
Manufacturing Steps in Aerospace
PCB Assembly
Material
Selection: Minimize stress from temperature swings
with the substrate to the component's CTE matching. Polyimide, as a candidate
for high-stability advanced materials
Inspection
of Component: Composition verified with the help of
XRF. Crystallographic structure and purity have been supported by XRD.
Measurements of Surface Outgassing, and SEL susceptibility testing in
components. Solderability is optimized and corrosion is reduced with
specialized lead finishes.
DI
Water Rinse (optional) — Resistivity > 18
MOhms/cm for low ionic contamination. The only difference is that it results in
ultra-pure DI water after filtration. A multi-stage nitrogen rinse guarantees a
full clean vacuum.
Stencil
Printing: Accurate +-10 micron laser-cut stencil
apertures to place paste accurately Pressure profiling to optimized
Wafer-to-Paste contact and thereby consistent paste transfer. Print settings
for solder paste viscosity
Pick-n-Place: Fine pitch component placement accurate to +/- 25 microns with the
use of high-resolution vision systems. Maintains constant temperature/humidity
that reduces the shifting in placements.
Reflow
Soldering: An atmosphere of less than 200 ppm
oxygen in nitrogen can help avoid any solder oxidation. Controlled ramp rates
and time-in-liquids form joints ideal for a precise reflow profile.
X-ray
Inspection - Cone Beam technology provides 2.5D
synthesis for a drastically improved visualization of the actual solder joints
in real, physical space. Void and coverage-insufficient detection use
automation, as well as identical IMC layer variations.
3D
AOI: Components and joints inspect using
multi-angle illumination. Sophisticated algorithms detect pulled leads and the
slightest pin-short failures.
Aerospace PCB Design Standards
Substrate: High performance CTE controlled FR-4 Extreme temperature pure
polyimide or metal core. High current, heat sink; larger copper traces.
Components: Space materials for temperature, radiation vibration and shock
Preferred TH for extra strength, SMT optionally allowed.
Rigid-Flex
and Multilayer Stackup: Advanced signal integrity
analysis. Controlled impedance traces, careful power/ground plane placement.
Extra levels of insulation (higher voltages)
Layout: Place components strategically so that routes are short; avoid
noise coupling. Vias used for signal integrity and 4. Decoupling caps, decaps
everywhere
This includes running Automated Design Rule
Checks (DRCs) and Electrical Rule Checks (ERCs) to look for nasty manufacturing
defects or electrical problems. Validate UX matches fab capabilities and
electric characteristics
Documentation: Clearly drawn schematics, BOMs and the stack-up of
each layer. Design data linked for perfect specification match
There is no room for errors and failures in
aerospace PCB assemblies. The short answer is yes, but the long answer. To
ensure the highest level of reliability and safety possible these assemblies
need to meet strict quality regulations.
What Standards and Certifications
Are Required for Aerospace PCB Assembly?
IPC Standards:
IPC-A-610
Class 3: This is an industry-wide standard accepted
as the benchmark across electronics assembly acceptance requirements. Class 3:
This is the top-of-line inspection. Furthermore, it demands in addition to
having no less than high soldering criteria.
Other IPC standards, such as:
· IPC-6012 (Qualification and
Performance Requirements for Rigid Printed Boards)
· IPC-WHMA-A-620 (Requirements
for Acceptance of Electronic Assemblies)
These standards are good to check specific
areas in PCB fabrication that are relevant to assembly.
Standards for a Quality Management
System
AS/EN 9100 (or FAA AC-00-56): Derived from
ISO 9001, this is a complex quality management standard that was drafted
especially for the aerospace industry. 1st: in every manufacturing life cycle
it preaches a culture of continuous improvement (kaizen), risk mitigation and
stringent process control.
Nadcap (National Aerospace and Defense
Contractors Accreditation Program): This industry-led program offers
accreditation to suppliers performing various specific processes, PCB assembly
included. The Nadcap audits determine if manufacturers have the breadth of
knowledge, specialized equipment and stringent quality controls they need to
meet the exacting demands of suppliers in aviation.
Aerospace PCB Applications
Flight
Control: The PCB will interpret signals from the
pilot, data from sensors (accelerometers and / or gyros) and affect a stable
flight by moving the aircraft controls (ailerons & flaps(speed),
rudders(yaw steering)).
Navigation
- PCBs can calculate position and orientation
precisely enough to be able to travel safely, using sensors such as GPS (Global
Positioning System) or inertial.
Communication: This is how well the data sharing, mission control and clear voice
chat between airplanes or spacecraft go on!
Avionics: Hundreds of PCBs power instruments, engine controls and displays
in the cockpit providing pilots with an instantaneous snapshot of flight data.
Satellites/Spacecraft: PCBs handle power (generation, distribution and control),
communications with ground stations/between spacecraft in constellation as well
as all failure detection diagnostics.
Launch
Vehicles: PCBs ensure ignition of the engines
equipped, proper utilization of instruments and data for a safe liftoff.
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Assembly Manufacturer
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We provide following PCB manufacturing for aerospace
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Surface Mount Pcb Assembly(SMT)
Through Hole Pcb Assembly
Flex Pcb Assembly
Conclusion
Thus, aerospace PCB assemblies are not just
pieces of printed circuit boards. Everything from the selection of raw
materials to manufacturing of the final product and meeting very high-quality
standards go through these assemblies. Moreover, they are highly reliable in
the very harsh environment of space and aviation. Their applications cover the
whole range of an aerospace vehicle’s mission, working quietly in the
background to provide such vital services as navigation, communication, and
control.
