Why is the CPU not round but square? Almost all friends who know something about hardware will know that the CPU is a square thick metal chip, and of course there are rectangular versions. The upper surface is flat and smooth, while the lower surface has metal contacts or pins. Although our default CPU shape is rectangular, I wonder if any of you have thought about why the CPU is not round?
1. The CPU we see is not a real CPU
Before answering this question, we need to popularize science to everyone. What we can see with our eyes and touch with our hands is not the CPU itself, but its package. The CPU body chip is firmly installed in the center of the package. It is no coincidence that the shape of the CPU chip is also rectangular, so let's talk about why the real CPU chip is this shape.
2. Starting from manufacturing
Maybe many students know that CPU chips are made of sand. I don't know whether this knowledge has the scientific merit that Mr. Lei wants to sell mobile phone chips as sand. The sand is composed of silicon dioxide, from which we extract silicon to make a thick and long single crystal silicon rod, and then cut it into thin and round silicon slices, which is more known as "wafer". Until now, the wafer is still round, which is the origin of its name. After a series of complex processing, including ion implantation, electroplating, lithography, etc., many small CPU rudiments appeared on this wafer. Then the wafer is divided, and the CPU chips are separated from each other, and the unqualified parts are removed. The rest is the qualified CPU chips. Then put the CPU chip on a PCB, cover it with an aluminum cover, and connect it with brazing or silicone grease in the middle. The CPU we can see is ready. (Of course, it's not that simple. It's too long here.)
3. Why is it square?
Some students may be confused. Is there any inevitable relationship between the CPU production process and why it is square? In fact, we know that the CPU cube is cut from a huge round cake. In order to reduce costs, the more copies of this cake, the better. If you cut many circular areas from a plane, the remaining gaps between the circles will be completely wasted. If you cut many small squares, there will be no gaps at all, leaving only a few wasted areas at the edge of the wafer. The densest circle will still waste a lot of area. At the same time, consider the difficulty of cutting. Of course, linear cutting is many times simpler than curve cutting. In this case, the process is simpler and the yield of CPU can be improved to a certain extent. In fact, the answer to this question is not complicated. The CPU is square, but simply because square is easier to cut and has higher utilization, it is least wasteful. Cutting into squares can save wafers, and the process is simpler. Although cost control is an inevitable result of the enterprise's pursuit of profits, therefore, we can only spend thousands or hundreds of yuan to buy one of the highest crystallization of human technology. Look at the CPU in the front of the host, can you feel the beauty of the wisdom condensation.
Finally, let's sum up:
1. If it is made into a round shape, it will waste more materials, increase consumables and increase the cost of CPU when cutting chips.
2. The square pins are arranged neatly, saving space and improving usability.
3. CPU chip is made of silicon, so it is related to the properties of silicon crystal. When a chip is made on a silicon chip, it is cut and then packaged. The cutting direction of natural silicon is 90 degrees vertical, which is suitable for cutting, but it is difficult to cut into a circle.
4. The square packaging of CPU is much better than the round packaging, and also conforms to the industry standard.
5. The square chip is installed on the PCB; The circular chip cannot cover the plane without leaving a gap, and the PCB area of the circular chip will be much larger than that of the square chip.
