Defense Speak Interpreted: Rad-Hard Electronics

Have you ever seen electronics described as “rad-hard,” or radiation-hardened, and wondered what that meant and how that was done? Did you like me just assume that “rad-hard” and “expensive” were synonymous? Did you think that this was a Defense Department term since they deal with nuclear weapons?

What part of electronics needs to be protected from radiation—chips, packaging, boards, assemblies? What kinds of radiation harm electronics? How is radiation protection accomplished for each type of radiation?

What I thought was a pretty simple technology to keep electronics working in space turns out to be a highly complex problem with multiple causes, intensities, results, and solutions. And that is for electronics not considering radiation damage to humans or terrestrial organisms. I was aware of occasional news about sunspot activity, but I had little idea that this was a sudden increase in solar radiation that would affect satellite/radio communications and reportedly included ATM machines.

The concept of radiation only dates back about 125 years to the discovery of radioactive elements and the imaging properties of radiation that evolved into X-rays. The critical step in the process was that radiation activated phosphors, which emitted visible light and, in turn, exposed silver films or screens. Radiation recognition included:

  1. Broken bone X-rays by linking electronic “tube” radiation sources to recording film
  2. Massive radiation injuries from the atomic bombs in WW2
  3. Scary devices as foot X-rays to show shoe size/fit in the 1950s

This all preceded any recognition of radiation problems for electronics later in the 1960s. By the time electronics shrunk to semiconductor size in the late 1960s, we were ready to add outer space radiation damage effects to the problem list for electronics—especially for orbiting satellites and long-range missiles. Some of the first space missions were to map the intensity of radiation in the Van Allen radiation belt around the earth to prepare for further radiation-hardening and human space flights.

What is the spectrum of radiation that can cause damage to electronics? We need to look at radiation in terms of electron volts in orders of magnitude (Figures 1 and 2).

Fritz_fig1_1020.jpg
Figure 1: Relative particle energies and rates of cosmic rays [1].

Fritz_fig2_1020.jpg
Figure 2: Electromagnetic spectrum [2].

This is a huge range with X-rays starting at 10 to 5th power to cosmic rays at 10 to 15th power, causing damage to electronics. And worse, the effects of radiation cause different types of damage to electronics—some of which is permanent. Imagine in billiards how the cue ball scatters the rack of 15 balls all around the table upon impact. The scattered balls can be recovered (re-racked) by checking to see if they are replaced properly in the rack.

But imagine a sonic speed cue ball hitting the rack of balls and breaking some while causing others to fly through the walls or ceiling. That is the higher energy collision of gamma or cosmic rays with electronics. The electronics survivability is to allow for this damage is with redundant electronics.

According to one research article [3], there are seven sources and damage impacts of radiation that have to be considered in electronics design:

  1. Cosmic rays: They consist of approximately 85% protons, 14% alpha particles, and 1% heavy ions with X-ray radiation.” The atmosphere filters most of them, so they are mainly considered for spacecraft and high-altitude aircraft.
  2. Solar particle events: They come from the sun and consist of a large flux of high-energy protons and heavy ions accompanied by X-ray radiation.” Worse, this varies with solar flares and sunspot activity
  3. Van Allen radiation belts: They include electrons and protons trapped in the earth geomagnetic field. They mainly affect satellites.”
  4. Secondary particles: They result from the interaction of other kinds of radiation with structures around the electronic devices.”
  5. Nuclear reactors: They produce gamma radiation and neutron radiation, which can affect sensor and control circuits in nuclear power plants.”
  6. Nuclear explosions: They produce a short and extremely intense surge through the entire spectrum of electromagnetic radiation, an electromagnetic pulse (EMP), neutron radiation, and a flux of both primary and secondary charged particles.” Remember the “neutron bomb,” which kills all people but leaves infrastructure intact.
  7. “Chip packaging materials: They are a kind of insidious source of radiation that was found to cause soft errors in new DRAM chips in the 1970s. Traces of radioactive elements in the chip packaging will produce alpha particles, which discharge occasionally some of the capacitors used to store the DRAM data bits.” Have you heard of “low alpha” lead for assembly?

There are two kinds of radiation damage electronics: electromagnetic emissions and particles. Don’t get me started on whether electrons are actually energy or are “particles.” Just protect electronics from a very energetic electron bombardment. We can see that radiation damage occurs in many places: space (Van Allen belt), nuclear reactors, particle accelerators, radiation weapon systems, isotopes in packaging materials (give up particles), on earth from penetrating cosmic radiation, nuclear radiation weapon systems (neutron bomb).

Radiation-hardening protects electronics through (1) a specialty design, (2) radiation shielding enclosure, and (3) error-correction algorithms that “restore the pool balls to the rack.” Design starts with the utilization of known good chip designs and then beefs them up with more tolerant materials of construction. Since rad-hard electronics needs proven designs, rad-hard chips are seldom leading edge, and once proven in use, rad-hard designs tend to use these workhorse chips over and over. For instance, bipolar ICs are less sensitive to similar doses of radiation damage than CMOS. Total ionization dose (TID) is the term for accumulated damage from relatively constant radiation bombardment and factors into the choice of materials.

Different damage occurs from single events like nuclear explosions. These transient dose events can both completely throw off the function of the semiconductor and permanently damage (fry) the device if radiation intensity is large enough. The damage caused by a high energy single cosmic ray impact is somewhat similar to the transient of a nuclear explosion. The damage topic quickly gets into the functions of semiconductor sources, drains, gates, and other specific terms way beyond my capability to present here.

As sensors are frequently made with semiconductor techniques, they also need to also be rad-hard. And with the promotion of such ideas as the “Space Force,” radiation-hardening is forecast to see greatly increased use.

Again, what can be done (that a layperson can understand) to defeat radiation damage? Shielding with radiation-absorbing metal comes to mind. Semiconductors on insulator (SOI), like silicon oxide structures, are not as sensitive as pure silicon. And newer materials, like silicon carbide or gallium nitride, are coming down in price and promise even better radiation tolerance. Some good choices may come from using S-RAM (static) versus D-RAM (dynamic) memory. Also, error-correcting logic can be incorporated into the chip at the expense of making each die larger and more expensive.

Since you see X-rays on the damage chart, you may ask, “Does X-ray inspection of electronics cause permanent damage”? This is a known factor, and vendors of electronics X-ray inspection equipment limit dose and exposure time to minimize any radiation damage. Electronics damage is the product of both exposure dose and the time exposed to the source. But don’t fear; instead, continue to evaluate solder joints with X-ray. Unless you leave the assembly being exposed over the weekend, you will be okay.

Finally, the U.S. is not the only country work on rad-hard. Here is a recent tidbit I picked up [4]:

“Researchers at Peking University, the Chinese Academy of Sciences, and Shanghai Tech University have recently fabricated a radiation-hardened and repairable integrated circuit (IC) based on carbon nanotube transistors with ion gel gates. This IC, first presented in a paper pre-published in Nature Electronics, could be used to build new electronic devices that are more resistant to high-energy radiation.”

You can either be a trained radiation-hardening expert with lifetime employment, or you can trust the rad-hard engineers to do their job and use their electronics in confidence in your designs.

References

  1. Cosmic Ray,” Wikipedia.
  2. Horst Frank, “Electromagnetic Spectrum,” Wikimedia Commons.
  3. Fa-Xin Yu, Jia-Rui Liu, Zheng-Liang Huang, Hao Luo, and Zhe-Ming Lu, “Overview of Radiation Hardening Techniques for IC Design,” Information Technology Journal, 9: 1068-1080, 2010.
  4. Ingrid Fadelli, “Radiation-immune and repairable chips to fabricate durable electronics,” Tech Xplore, October 2, 2020.

Dennis Fritz was a 20-year direct employee of MacDermid Inc. and is retired after 12 years as a senior engineer at (SAIC) supporting the Naval Surface Warfare Center in Crane, Indiana. He was elected to the IPC Hall of Fame in 2012.

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2020

Defense Speak Interpreted: Rad-Hard Electronics

10-13-2020

Have you ever seen electronics described as “rad-hard,” or radiation-hardened, and wondered what that meant and how that was done? Did you like me just assume that “rad-hard” and “expensive” were synonymous? Did you think that this was a Defense Department term since they deal with nuclear weapons? Denny Fritz explores this and more.

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Defense Speak Interpreted: The Defense Innovation Unit

09-22-2020

Many of Denny Fritz's columns are about new defense technologies and innovations, but what about an organization with “innovation” in its name? Here, he describes the history and purpose of the Defense Innovation Unit (DIU), as well as some of its programs.

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Defense Speak Interpreted: Unpacking the NDAA

08-25-2020

What is this NDAA stuff you keep hearing on the national news all the time, and why is it important to PCBs? Denny Fritz explains what is going on with the National Defense Authorization Act, which authorizes programs and lays out the priorities and policies for the U.S. Department of Defense (DoD).

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Defense Speak Interpreted: DMEA

07-14-2020

A June 17 article announced a supply chain award of $10.7 billion to eight defense companies for semiconductors. Dennis Fritz explains how the Defense Microelectronics Agency (DMEA) administers this contract and keeps the technology secure.

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Defense Speak Interpreted: C4ISR

06-16-2020

Only the U.S. Defense Department would lump together seven concepts—command, control, communications, computers, intelligence, surveillance, and reconnaissance—into a single acronym: C4ISR. Denny Fritz explains how C4ISR has been called the “nervous system” of the military.

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Defense Speak Interpreted: What’s an RCV, and What Do Electronics Have to Do With It?

05-12-2020

In "Defense Speak," RCV does not stand for ranked-choice voting, a remote control vehicle, a riot control vehicle, or a refuse collection vehicle, although the second one is close; it stands for a remote combat vehicle. Denny Fritz explores this concept and its defense applications.

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Defense Speak Interpreted: Why Is Defense Hyper Over Hypersonics?

04-14-2020

Perhaps you have noticed that the term “hypersonics” is now a buzz phrase in a big part of the Department of Defense research effort. What does hypersonic mean, and why is so much work needed in this weapons field? Dennis Fritz explains.

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Defense Speak Interpreted: Be Prepared for CMMC

03-24-2020

If you are a current or future Defense Department contractor or subcontractor, you need to be prepared for the next cybersecurity requirements coming online during 2020. This is the Cybersecurity Maturity Model Certification, or CMMC, in Defense speak. Dennis Fritz explains how there will be five levels of cybersecurity requirements for various amounts of Controlled Unclassified Information (CUI) you handle, with increasing requirements from one (least) to five (most).

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Defense Speak Interpreted: The Missile Defense Agency

02-25-2020

The Missile Defense Agency (MDA) has its roots in the Strategic Defense Initiative (SDI), known as 'Star Wars' in the 1980s as proposed by President Ronald Reagan. In this column, Denny Fritz provides an overview of how the MDA operates and describes types of missiles and phases.

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Defense Speak Interpreted: What in the World Is MINSEC?

01-14-2020

The Defense program designated MINSEC (Microelectronics Innovation for National Security and Economic Competitiveness) is probably one that you have never heard of but will likely gather more headlines in the future. Dennis Fritz explains.

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2019

Defense Speak Interpreted: The Continuing Resolution

12-10-2019

The topic of the continuing resolution (CR) has been sneaking past other hot Washington topics, such as impeachment, candidate debates, and why the Redskins are so bad. Dennis Fritz provides an update concerning a CR and the 2020 fiscal year.

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Defense Speak Interpreted: Executive Agent

11-12-2019

After reading my previous column, you may have realized that electronics packaging technology development came from the Naval Surface Warfare Center in Crane, Indiana. One of its core responsibilities is the assignment of “executive agent” for PCBs and electronic interconnects. But what is this “executive agent” thing, frequently shortened to EA? Dennis Fritz explains.

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Defense Speak Interpreted: PCB-related OTAs from NAVSEA Crane

10-29-2019

In my previous column, I described how Other Transaction Authority (OTA) projects were speeding up the development of new technology for the Defense Department. Much of this improvement has to do with the speed of contracting and the less restrictive selection and payment process involved. Specifically, I would like to call out projects under the National Security Technology Accelerator (NSTXL).

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Defense Speak Interpreted: Other Transaction Authority

09-19-2019

DIU grants contracts under a joint OTA and a parallel process called commercial solutions opening. Most of the five DIU focus areas depend on electronics: artificial intelligence (AI), autonomy, cyber, human systems, and space. At the end of 2018, DIU had funded 104 contracts with a total value of $354 million and brought in 87 non-traditional DoD vendors, including 43 contracting with DoD for the first time.

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Defense Speak Interpreted: DARPA ERI

01-29-2019

DARPA ERI stands for the Defense Advanced Research Projects Agency and the Electronics Resurgence Initiative. This tongue-twisting acronym is the latest Department of Defense (DoD) effort to catch up and surpass world semiconductor technology for the secure IC chips needed by advanced defense electronics systems.

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2018

Defense Speak Interpreted: PERM—Pb-free Electronics Risk Management

12-18-2018

In this column, we explore PERM—the Pb-free Electronics Risk Management Consortium. No, the group members do not all have curly hair! The name was chosen around 2008 by a group of engineers from aerospace, defense, and harsh environment (ADHE) organizations.

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Defense Speak Interpreted: Defense Electronic Supply Chain Issues

10-18-2018

On October 5, 2018, the Department of Defense (DoD) highlighted issues with the release of the 146-page report “Assessing and Strengthening the Manufacturing and Defense Industrial Base and Supply Chain Resiliency of the United States” from President Donald J. Trump

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