November 4, 2019

Cosmic Mishaps: How Cosmic Rays Can Disrupt Your Design


Your electronic design is haunted by intergalactic gremlins.  The Earth is constantly bombarded by high-energy particles from stars all throughout the galaxy.  These charged particles consist of subatomic particles, such as neutrons, electrons and muons, and fully-ionized atomic nuclei traveling at relativistic speeds.   When these cosmic rays strike the oxygen and nitrogen molecules in our atmosphere, they leave a shower of high-energy photons and elementary particles in their wake.

A portion of those high energy particles can make it all the way through the atmosphere to the surface of the Earth.  If a cosmic ray, or one of its byproducts, passes through your printed circuit board, it can either damage PN-junctions, temporarily change the logic-level thresholds of digital inputs and digital outputs, and temporarily or permanently flip bits and entire words of memory in your microprocessor or microcontroller.

While the events are rare on the surface of the Earth, the consequences of a Cosmic Ray strike can be deadly.  Cosmic Rays are thought to be responsible for lightning strikes, airplane accidents, runaway automobiles, and perhaps even erroneous election results.

So, just how susceptible is your design to a cosmic-ray event?  Well, absent two-meters of leaded-concrete shielding, a high-energy cosmic ray that is headed for your design will hit it.  But not all cosmic rays are that energetic — so luckily, there are some design elements that can attenuate the frequency of impacts.  But cosmic rays cannot be completely stopped by any sort of commercially available enclosure or shielding.

Unfortunately, statistics and luck determine whether or not your design will be struck by a primary or secondary cosmic ray, and your component choice and circuit design skills will determine whether or not your device will malfunction or survive the event.

Cosmic Ray Incidence

Cosmic rays are charged and uncharged particles that pass through the Earth’s magnetic fields.   The magnetic fields that surround Earth capture and redirect charged particles into pseudo-toroidal regions high above the surface of the Earth.  While in these “Van-Allen-Belt” toroids, the particles are accelerated to relativistic speeds.  Trapping particles is great news for the health of terrestrial-based electronic designs.  But it is quite obviously bad news for spacecraft and astronauts that might have to operate through these regions of space.

The cosmic ray flux on the Earth’s surface is influenced by a variety of factors, including the 11-year solar cycle, solar flares, and extra-solar events such as supernovae, pulsars, and gamma-ray bursts.

Without the Earth’s atmosphere to absorb cosmic rays, satellites and interplanetary probes are perpetually bombarded by high-energy, charged particles.  This harsh-environmental condition requires specially engineered integrated circuits.  Fortunately, a great deal of hard-won experience has taught us what to expect in space, and that information can be generalized for experiences closer to the surface of the Earth.

Spacecraft electronics will see the greatest number of impact events, followed by airplanes, and high-altitude and high-latitude installations.  No part of the Earth is so remote that impacts do not happen.  Only by burying your circuit board assembly deep underground can you gain enough shielding to avoid Cosmic Rays.  As electronic packages shrink, the chances of an impact decrease.  But as operating voltages decrease, the chance of a failure caused by a cosmic ray increase.

In our next blog post, we will look at how cosmic rays might impact your next aerospace or high-altitude electronic circuit board assembly.

Get a Quote