Whether it’s from naturally occurring sources or induced by modern human ingenuity, electronic components, like everything else, are subject to regular exposure to radiation. It is vital to understand the various sources of radiation exposure as well as their likely effects on today’s microelectronics and the devices they make possible. This is especially true of components that support products demanding high reliability, like those in medical devices, automobiles, and the airplane I’m flying on while writing this.
As a manufacturer of industrial X-ray inspection systems, it’s a familiar question: “Is radiation from the X-ray machine going to harm the electronic components in my widget?” Not to be coy, but the answer is a familiar refrain as well: “It depends.” The more useful answer is actually, “It is highly unlikely.” But again, for high reliability products, the answer has to be precise, and quantified to the best degree possible. I can’t say to the maker of a potentially lifesaving medical device, “X-raying this probably won’t hurt anything.” So, let’s take a look at common sources of radiation exposure, and the potential effects it may have on electronic components, so we can better understand the risks.
First, radiation is inescapable. Background radiation from the things that surround us varies widely. The bulk of it come from trace amounts of naturally occurring radionuclides like uranium. Building materials, like cement, for example, can have higher concentrations of such elements, and thus give off higher levels of background radiation. Cosmic radiation is another inescapable source of naturally occurring radiation. Italy’s Gran Sasso National Laboratory is a renowned playground for particle physicists because of its relative absence of cosmic-ray noise. Everything, including our electronic devices, is subject to this radiation exposure. Cosmic radiation can be responsible for one of the more interesting forms of damage to electronics in what is known as single event upsets (SEU), in which bits stored in electronic circuitry can be flipped. The damage, while temporary, can be very disruptive and sometimes dangerous. “Can radiation damage electronic components?” Yes, it can.
In addition, there are a number of manmade sources of radiation exposure. From nuclear devices to medical and dental X-rays, there are many products of modernity that contribute to background radiation or common radiation exposure. The flight I’m on right now is increasing my relative exposure to cosmic radiation, probably to the tune of about 3.5 millirem (mrem), a similar dose to my last chest X-ray. The laptop computer I’m working on is getting the same dose. This same laptop also got an extra dose when it went through airport security. Likewise, it probably experienced a number of radiation exposures, some quite high, as part of a shipment from its manufacturer to distributor, as virtually all cargo are subject to X-ray inspection by customs agencies and commercial parcel services. Per the National Council on Radiation Protection and Measurements (NCRP), the typical yearly radiation dose per person in the U.S. is 620 mrem (6.2 millisieverts), but for many of the products we use, that number can be much higher.
It is true that the vast majority of electronic components and the consumer electronics are unaffected by common sources of radiation exposure. Even those subjected to modern cargo inspection system, with X-ray source power as high as 9MeV, come out unscathed. It’s one reason we are usually comfortable saying, when asked about our industrial inspection system (these rarely have source power higher that 130kV), “Nothing to worry about.” But with something as demanding as a medical device, or an engine control module, then that answer may not suffice. For a definitive answer we just need to know some of the parameters of any desired inspection. What’s critical in calculating the dose a sample will receive during inspection are the energy and volume of the X-ray photons, the duration of the inspection, as well as the distance between the sample being inspected and the X-ray source. Because industrial systems typically operate at relatively low energy for inspection of electronics, and inspection time is less than a second in many cases (especially for automated systems), a typical total dose is about 35mR, exceedingly far below that which could potentially harm even the most sensitive electronic devices. But if inspection required significantly higher power, and far longer duration to complete evaluation, we can and should calculate the total dose to understand its potential to damage sensitive parts.
It isn’t exactly rocket science, brain surgery, or even rocket surgery, but it is physics. And the good news is that radiation exposure of electronic components can be calculated, planned for, and kept to an absolute minimum based on specific need. When it comes to typical industrial X-ray inspection and the question of radiation exposure, I’m most often tempted to say, “It’s so low, it’s irrelevant.” But, like our ever-evolving microelectronics, it’s actually more complicated than that, and absolutely worth considering and even quantifying. I hope this has helped. Oh, and just for fun (especially with kids), if you want to witness cosmic radiation for yourself, try building a simple cloud chamber.
Dr. Bill Cardoso is CEO of Creative Electron.