Why Are Automotive Chips Still In Short Supply?

By now almost everyone knows that the auto industry is still short semiconductor chips, although the situation seems to be improving. While it’s pretty much a given that electric vehicles use more semiconductors, why do gasoline-powered internal combustion engine (ICE) vehicles use so many chips? And do these chips have attributes that make it harder to crank up the manufacturing capacity when they are in short supply? That’s what this article will try to explain.

Why are so many semiconductor chips used in cars?

The New York TimesNYT
said that a modern vehicle can use as many as 3,000 semiconductor chips, while another source said over 1000. I’m sure that depends on what you are counting, but as recently as the 1960s electronics in vehicles were pretty much limited to the car radio. How did a product that was almost entirely mechanical not that long ago end up with so many chips? The answer has several parts, and it reflects the general rise of chip usage in a vast range of consumer and industrial products: performance, cost, and the migration of functionality from hardware to software.

For automobiles, the huge push for improvements in fuel economy after the 1973 oil crisis led to the rapid increase in the use of electronics in engine controls. While electronic ignitions had started to appear in the late 1960s, the use of microcontroller chips for engine controls demonstrated what was possible with a digital approach. Using sensors to monitor things like temperature, crankshaft position, mass air flow, throttle position, and concentration of oxygen in the exhaust gases, automakers were able to dramatically improve the fuel economy and emissions profiles of their vehicles. The controller chips did on-the-fly calculations to optimize engine performance, something that was impossible to do with mechanical sensors and linkages.

This highlights one of the big drivers behind growth in the use of semiconductor chips: the implementation of many functions using software that might have been hard to do (or even impossible) with hardware alone. Calculating the optimal rate to feed the fuel injectors might involve solving complex equations in real-time or looking up numbers in tables. That’s readily (and inexpensively done) with computer chips and some software. This is also how we got more sophisticated automatic transmissions, using software to implement sophisticated control schemes like downshifting when going downhill. A controller chip attached to speed sensors sends signals to semiconductor power switches that control the transmission solenoids. This highlights the role of power semiconductors, devices that switch power under digital control, which are widely used throughout a vehicle. If you count these devices as “chips” as well (as the New York Times probably did), the semiconductor device count in a vehicle goes way up.

Automotive grade semiconductor chips and the associated switches and devices they control are more reliable than their mechanical counterparts. I remember when I was a lot younger, a friend showed me the sequential turn signals in the trunk of their 1968 Mercury Cougar. The red turn lights were apparently connected to a little motor-driven rotating switch that “sounded like a washing machine.” Once the contacts got worn or corroded, that thing was a mess. Going to semiconductor switches and a simple timer circuit made mechanisms like that far more reliable.

Another example – several years ago, I rented a Volkswagen Beetle, and as I hopped into the car and closed the door, the window on the driver’s side rolled down a little just as the door was about to shut and then it rolled back up. That equalized the pressure inside the passenger compartment, so your ears wouldn’t pop. That kind of functionality would have been really challenging to do purely mechanically, but with a microchip it was probably only a few lines of code. A vehicle’s body electronics – the power windows, door locks, side-view mirrors are typically connected to a body control module (BCM) chip. The BCM also communicates with other electronic units throughout the car – things like the instrument cluster and lots of sensors. And of course, infotainment systems use a large number of chips.

One additional thing about implementing things in software instead of hardware: you can modify the product after you ship it. We see that all the time in our computer and phone software – it seems every tenth Zoom meeting I’m getting a new software update. But hardware? Tesla has shown the power of “over the air updates,” which modify features on the car. I recall GE Aviation also did a software fix to temporarily correct a problem with high altitude icing on its GEnx turbofan engines used on BoeingBA
787s and 747-8s. With software? Wow, that was impressive!

What’s unique about how automotive chips are designed and manufactured?

There are several standout features of automotive chips. The first is that they must operate for a long time over wide temperature extremes while subject to lots of shocks and vibrations. Automakers expect an operating lifetime of 15 years and tolerate a failure rate of zero parts per billion during that time. They also want replacement parts to be available for 30 years. Most consumer electronic devices (like your phone) have failure rates measured in parts per million and would be considered obsolete after five years. If your PC encounters an error, reboot and give it another whirl. If your engine controller suddenly fails, you don’t pull over to the side of the road and reboot (although I have heard of something like this happening with an electric vehicle’s infotainment system). The Automotive Electronics Council (established by the Detroit Big Three) maintains a range of qualification standards for chips. For operating temperature, it defines Grades 0, 1, 2, and 3 operating ranges, with Grade 1 covering -40ºC to +125ºC and Grade 2 from -40ºC to +105ºC. That has a high-end limit hotter than the temperature of boiling water, by the way. This is a considerably more challenging range than most consumer chips will ever see. The chips need to be reliable, so they must be designed and tested to have a sufficient operating life under extreme conditions.

The second requirement is they must be designed with safety in mind. A lot of this is covered by ISO 26262 – Functional Safety Standards, which covers a range of things beginning with how they are designed to how failures are handled.

Finally the processes for making chips at semiconductor fabs have to be “qualified,” which typically takes six months. The fabs also need to have modifications to their process design kits for high temperature device models, thicker interconnects, and other things that enhance reliability. After that the chips must be extensively tested before they can get built into vehicles. That means accelerated life testing at elevated temperatures and harsh conditions to simulate many years of service. Mainstream automakers have taken as long as 3-5 years to design, test, and validate new chips.

I pointed out earlier that many automotive microcontrollers use 90 nm technology, and it has been difficult to add capacity. The shortages over the past two years have prompted some automotive chip vendors to migrate to 65/55nm nodes, and some have even jumped to 40 nm. But DigiTimes says it will take as much as five years for the new chips built with 40nm processes to clear validation processes and get put into new vehicles, which means the existing technology will be in use for some time to come. And that’s why the auto chip shortage is talking longer than most to alleviate.