The news says "automotive chips". What makes them different?

The news often talks about "car chip shortages", "automotive-grade chips" and chips that "passed automotive qualification". Automotive chips are simply the chips inside a car. They are made in the same fabs as the chips in your phone. What's different is what's asked of them: they have to survive more cold, more heat and constant vibration, last well over a decade, and some of them, if they go wrong, could get someone hurt. Chips that have passed the car industry's standards for all this are called automotive grade.

Which chips are in a car, and what do they do?

A newer car has dozens of small computers, sometimes over a hundred, called electronic control units (ECUs), each running one job. Counted one way or another, the whole car can hold more than a thousand chips. Roughly, they fall into a few groups:

• Engine, motor and battery: in a gasoline car, how much fuel to inject and when to fire the spark; in an electric car, how much power goes to the motor, and the voltage and temperature of every cell in the battery. There are many power-handling switches here, and some are made of silicon carbide (The news says "wide-bandgap semiconductors". What are SiC and GaN?).
• Brakes and airbags: when a wheel is about to lock, the brakes are released and reapplied very quickly so the car can still steer; in a crash, the chips measure how hard the car is slowing down and decide, in less than the blink of an eye, whether to fire the airbag.
• Sensors: cameras, radar, ultrasonic parking sensors and tire pressure sensors turn what's around the car, and the state of the car itself, into signals.
• Entertainment and navigation: the dashboard screen, navigation and audio. These are the most like the chips in a phone.

Why are the requirements stricter than for a phone?

• A wider temperature range: a car sits outside in winter and in the sun in summer, and it's hotter still near the engine. A common grade for everyday electronics is guaranteed to work from about 0 to 70°C; a common automotive grade has to work from −40°C to 125°C.
• Constant vibration: rough roads, a running engine. The chip, the fine wires inside it and the joints that solder it to the circuit board all have to hold up. Add moisture, voltage that jumps up and down, and interference from other electrical equipment nearby.
• Well over a decade of use: a phone gets replaced after a few years, but a car is often driven for over ten; a common rule of thumb is to design for 15 years.
• A failure can be a safety problem: when a phone freezes, you restart it. When a brake or airbag chip goes wrong, someone could get hurt. So the failure rate is often counted as "how many bad chips per million", and the goal is to get as close to zero as possible.

To get close to zero, one method is to also pull chips that are within spec but very different from the rest of their batch. Picture a class where everyone scores around 80, and one student scores exactly 60: it's a pass, but you take a second look. Yield drops a little (What does "yield" mean in chip news?), but fewer bad chips end up in cars. Testing is stricter too, for example some final tests are run at both cold and hot temperatures (How are chips tested?), and some chips are even "burned in" one by one before shipping (What is burn-in?).

Which standards do the checking?

AEC-Q100: "will it fail?"

The Automotive Electronics Council (AEC) is an industry association founded in the 1990s so that everyone could qualify car parts against one common set of standards. AEC-Q100 is the one for chips (integrated circuits); single components such as transistors and diodes use Q101, and resistors and capacitors use Q200.

The idea is to list, one by one, the ways a chip can fail, and set an accelerated test for each, so that what would take many years to happen happens in weeks or months. For example:

• Running at high temperature and voltage for 1,000 hours straight (HTOL): three lots of 77 chips each, and not one may fail.
• Taking several hundred chips and running them powered at high temperature for a short time, to see how many early-life failures (chips that fail soon after they start being used) turn up.
• Going back and forth between very cold and very hot many times, or sitting somewhere hot and humid.
• Pulling and pushing on the fine wires inside the chip to see whether they're attached firmly (pull test).
• Zapping it with static electricity to see whether it breaks.

It also sorts chips into grades by the temperatures they can take: the common Grade 1 is −40°C to 125°C, and the top grade, Grade 0, goes up to 150°C.

ISO 26262: "what if something goes wrong?"

No amount of testing guarantees a chip will never fail. Another international standard, ISO 26262, covers "functional safety" for road vehicles: if an electronic system goes wrong, the danger still has to be kept low enough.

It starts by asking how dangerous each function's failure would be: how badly people could be hurt, how often you're in that driving situation, and whether the driver could still keep control. From those three, it sets four levels, ASIL A to D, with D the strictest. A function like braking, where a failure is very dangerous, gets a high level, and the higher the level, the more each step requires. The 2018 edition has a part devoted to how the standard applies to chips.

Chips often carry extra circuits that check themselves, too. For example, memory stores a few extra check bits with every piece of data, so most errors can be caught and corrected; or two identical cores work on the same thing and compare answers, and if they don't match, the system goes into a safe state.

Why do many car chips use mature nodes?

Many car chips don't need the most switches. They need to handle heat and high voltage, stay stable, and stay on sale for many years. Older generations have been made for years, the ways they fail are mostly well understood, and there is plenty of reliability data, so many car chips use mature nodes (The news says "mature nodes". Why do older chips still matter? explains more). The few chips that do heavy computing, such as driver assistance making sense of camera images, don't necessarily use older processes.

Why does qualification take so long, and why is it hard to switch suppliers?

A chip has to pass several stages before it goes into a car. First the chip itself goes through tests like AEC-Q100, and HTOL alone runs about six weeks. Then it's tested inside the part it goes into, and again in the whole car. All together, it often takes many months, and sometimes over a year.

And what was qualified is "this chip, made this way". Changing a material, changing the process or moving production to another plant, whenever it could affect function, quality or reliability, means choosing tests from the standard and qualifying again, and telling customers first. So during the years a car model is on sale, it mostly keeps the same chips and rarely switches to another source.

Next time you see it in the news

• "Automotive-grade chip", "passed automotive qualification": the chip went through a round of reliability tests under the car industry's standards (such as AEC-Q100), passed them all, and can be used in cars.
• "Car chip shortage": not enough of the chips that cars need are being made. Without one small chip, a whole car can't be finished, and qualified sources are hard to switch, so a shortage is hard to fill quickly.
• "Meets functional safety ASIL D": designed to the strictest level of the functional safety standard, for places like the brakes where a failure is very dangerous.

In fab24hr

There are no automotive chips in the game. Glowmere, the chip the main story The life of a chip follows, is a small company's hearing-aid chip: what matters most for it is leaking as little power as possible on standby (Why do chips use power?), and it's made with a mature process generation.

But the checks that car standards care most about are in the game. In chapter 4 of the main story, "Two Weeks Early", you are the R&D integration engineer on the R&D line, waiting on HTOL: three lots of 77 chips each. In chapter 11, "The Ball Lifted", you are the assembly process engineer, two wires in the pull test came out low, and you decide whether to stop the wire bonder. In chapter 12, "The Night Before Shipping", you are the customer liaison at a test-and-assembly house, and Fang in the reliability lab says he can take a few hundred chips and run them powered at high temperature for two days to check for early-life failures; whether the whole batch ships a week late is up to you.

Tap "Clock in", choose "A day in the fab", tap "Test-and-assembly house" on the "Your role today" card and swipe to the customer liaison: the evening shift is chapter 12. The companies, chips and people in the game are fictional; the parts about automotive chips and standards come from public, general sources. For other jargon, see Chip fab jargon in plain English.