From consumer grade to aerospace grade, what is the difference between chips?

The grade division of chips is actually the division of the harshness of the chip application environment. Our common chips are usually divided into four categories, civilian grade (consumer grade), industrial grade, automotive grade and military grade (aerospace grade). At present, the highest specification chip we can access is the car specification chip. Compared with consumer-grade chips, automotive-grade chips can withstand more extreme temperatures and usage environments.

Since military-grade and car-grade chips are so powerful, wouldn’t it be enough to make all chips meet the standards of high-grade chips as much as possible?

Chip grading is not that simple. It actually involves the entire process of circuit design, manufacturing process, and final packaging and testing of chips. High-standard chips may not be suitable for other levels of environments. First of all, chips with higher specifications often mean higher prices, and paying for impossible application scenarios will reduce the cost-effectiveness of chips. Moreover, it is not that the higher the chip level, the faster the processing speed. Sometimes the chip will sacrifice part of the performance in order not to crash in the face of special application scenarios.

Simply speaking, redundancy design is to increase the reliability of the chip in exchange for increasing resource investment.

The existence of redundant circuits in the chip is not a waste, because the chip needs to be fully prepared when facing unknown tasks to reduce the possibility of downtime under special circumstances. Chip design experts explain the redundant circuitry: "We can tailor the system to have enough buffering between the processor and the memory so that even if the memory is loaded to the maximum and there is maximum transaction flow between the processor and the memory latency, then the processor can cover many transactional issues". Certain redundant caches can prevent crashes when memory overflows when processing large-scale parallel tasks. In addition, the same effect can also be achieved for memory redundancy design.

Of course, designing redundant circuits is not a simple copy and paste. For example, the chip factory can increase the processing capacity margin in some processing processes, such as the redundant memory and cache mentioned above, which can allow the chip to deal with buffer timing issues and possible changes in a timely manner; redundancy can also be optional A mature IP core, although it is not necessarily the fastest computing speed, can maximize reliability; redundancy can also allow the processor to adopt a stable strategy rather than an efficient strategy when computing certain algorithms, as much as possible Avoid the harm caused by calculation errors.

In general, redundancy is not redundant. Engineers in the field of autonomous driving in the industry have pointed out: "Many aspects of the design are rules of thumb. They may ask for a 30% margin to provide a timing buffer. This can handle abnormal conditions encountered in the physical design. This This margin is by no means a waste, more like insurance for physical design or process critical issues.”

Before a piece of monocrystalline silicon finally becomes a chip for us to use, it has to go through design, manufacturing, packaging, testing and other links. One of the main purposes of packaging is to protect the fragile die inside from the external environment.

Take aerospace-grade chips as an example. Ordinary consumer-grade chips can achieve sufficient protection by using plastic packages, while aerospace-grade chips are often packaged in ceramics or metals, and the package is also plated with a layer of brass to isolate cosmic rays and high-temperature environments. In order to reduce the secondary effects caused by radiation, a special gas is also filled during packaging.

At present, the car specification level is the highest specification chip that consumers can see. Judging from the requirements of vehicle regulations, its operating temperature is required to reach -40°C to 125°C, and it also needs to be lightning-proof, moisture-proof, and shock-proof. Therefore, car-grade chips often have to consider heat dissipation and sealing issues when packaging. At present, most automotive chips are packaged in SIP. Most of the modules that require high computing stability are integrated together for packaging protection. At the same time, the communication distance between different modules is reduced, and the possibility of being affected during data transmission is reduced.

In fact, whether it is an industrial-grade, automotive-grade or military aerospace-grade chip, after multiple rounds of preparation in the early stage, strict selection and testing must be carried out at the end. Chips of each grade are not produced by chip manufacturers and are self-sealed, and the grades need to be determined after approval by relevant domestic departments.

At present, chips are roughly divided into four grades, consumer grade, industrial grade, automotive grade and military (aerospace) grade. Chips of different grades and specifications have different requirements from design to packaging and testing stages, and the usage scenarios are also quite different. In general, the higher the specifications of the chip, the more chip redundancy design, the tighter the package, and the more complicated and strict the testing process.