Back in 1978, I was admitted to Northwestern Polytechnical University.

Chapter 126 Four-layer printed circuit board, have you ever seen one?
A few days later.

"Such a small chip, such a small computer, can actually perform 800,000 calculations per second!" Fan Tongyu said with emotion as he looked at the computer that had been coordinated from Northwestern Polytechnical University.

In 1971, the Capital Cable Factory produced the 320 machine, which could perform one million calculations per second. It consisted of multiple cabinets and required a minimum of 150 square meters of computer room to house it. The machine in front of us can now be placed on a table!
"This is the progress of technology!" Fan Tongxue said from the side. "Keyboard input and monitor output are said to be the mainstream computer input and output devices abroad. If we disassemble this prototype and replicate it, the product will definitely be a bestseller nationwide!"

The two are twin brothers who went to school together, graduated and started working together. Now they are both key engineers in the factory. After Fan Tongyu took on this task, Fan Tongxue came to help.

“That’s right, let’s disassemble and replicate it now! The factory has already purchased a batch of chips from abroad through relevant departments. We’ll assemble them using the imported chips first, and once Factory 4433 produces the same chips, we’ll use the domestic ones to replace them!” Fan Tongyu said, picking up a screwdriver and starting to disassemble the main unit.

"This circuit board is so beautiful!" Looking at the lush green circuit board with its fine copper-clad circuitry that looked as if it had been printed on, Fan Tongyu couldn't help but exclaim in admiration.

Early vacuum tube circuits did not require circuit boards. Various components were mounted on a rack, and wires were soldered directly onto it. Later, with the advent of transistors, printed circuit boards were developed, using copper foil as conductors on a brown phenolic resin paper substrate to transmit signals. Transistor radios, televisions, and even computers produced by the Capital Cable Factory all used this type of circuit board.

They had never seen this kind of green circuit board before! The circuit lines on it were only one millimeter wide, and the lines were neatly arranged together, giving it a modern, industrial aesthetic!
“Our factory’s most sophisticated circuit boards have a line width of at least three millimeters. I’m afraid we… can’t produce this kind of circuit!” Fan Tongxue frowned.

"It's okay, we can just scale it up proportionally and put the circuit board into our rack. Anyway, the rack is ready." Fan Tongyu said, unscrewing the screws on the circuit board. After flipping the entire circuit board over, everyone saw the same dense printed circuits on the back of the circuit board, which looked like a spider web.

This is double-sided!

"Northwestern Polytechnical University's circuit board technology is really advanced! With such narrow line widths, it's not easy to align the top and bottom and drill holes accurately!" Fan Tongxue gasped.

"Hmph, just trying to attract attention. Let's make it wider; that way it'll be more reliable!"

Northwestern Polytechnical University, Computer Science Department, Internship Workshop.

"Qin Liang, we've already received orders for over three hundred computers, and we still need your help coordinating the chip supply!" Director Meng's eyes were full of anticipation.

"No problem." Qin Liang nodded. "When I have some free time, I'll ask my foreign friends to coordinate a batch to come back. But... we still need to urge Factory 4433 to quickly make our own knock-off chips. Buying them with foreign exchange is never the right way."

"Yes, we'll keep urging them, but..." Director Meng took a deep breath: "I heard that Factory 738 and Factory 4433 are in negotiations. They want to take all the chips made by Factory 4433. Qin Liang, you were right after all!"

Qin Liang smiled. This wasn't hard to guess; it was just the inherent flaw of some companies.

Qin Liang's gaze fell upon the circuit board being manufactured. The copper foil substrate underwent cutting, pretreatment, lamination, exposure, and development, almost indistinguishable from chip manufacturing. Through such precise manufacturing, a spiderweb-like circuit was formed on the substrate. Then... several substrates would be accurately stacked together and pressed together under high temperature and pressure to form... a four-layer PCB board!
In the 1970s, with the rapid development of integrated circuits and driven by Moore's Law, multilayer circuit boards also developed rapidly, featuring high precision, high density, fine lines and small holes, high reliability, low cost, and, most importantly, automated continuous production.

The current production is still done manually, but it is definitely the most advanced technology in the East at present!
"Thanks to the foreign books you brought, one of which is specifically about multilayer printed circuit boards. Together with the Department of Electronic Engineering, we've been researching the manufacturing process for these circuit boards. Right now, we can only produce them in small batches. Once we start making money, we'll build a department-run factory and set up an automated production line..."

Speaking of the future, Director Meng is full of confidence.

It looks like a printed circuit board from the outside, which is also high technology! In the distant capital, a group of engineers never dreamed that this beautiful circuit board in front of them was actually four layers. In addition to the two circuits visible on the outside, there are two more layers inside!

They worked quickly and efficiently, and within three days they had successfully replicated it. Although the circuit board area had tripled, making it fit only in a floor-standing cabinet, they were still very proud of their computer!
On the front of the server rack, the lettering "DJS060" is particularly eye-catching.

"Good, not bad, the technical strength of our big factory is really strong!" Di Weichao, the head of the technical department, looked at the computer in front of him with great satisfaction: "The factory has already spread the word that many units are very interested in our factory's 8086 microcomputer. If it weren't for the fact that purchasing chips from outside would cost foreign exchange, we would have received a large number of orders by now! Let's start small-scale production first! By the way, start the machine up and let me take a look!"

“Okay, this machine has a general operating system installed. We’ve already copied it to a floppy disk, so we can boot directly from the floppy disk!” Fan Tongyu said, inserting a large 5.25-inch floppy disk into the floppy drive and then pressing the start switch.

The fan started spinning, and the buzzing sound coming from inside the machine gave everyone the illusion that the machine had already been started.

But... the screen remained black!

Three seconds, five seconds, one minute...

Fan Tongyu frowned: "It must be that the monitor cable isn't connected properly. Hmph, this computer doesn't need a monitor at all. Just input the program directly. Northwestern Polytechnical University, they just know how to show off. We..."

As he spoke, he inspected the cables, but... when he got closer to the chassis, he smelled a faint burnt odor.

Oh no, the circuit board is burned out!

When the server rack was disassembled, part of the circuit board inside had changed color, and in particular, there were chips—precious imported chips!
"What happened?" Di Weichao frowned. Had the imitation failed?
"It must be a problem with the wiring, let's check it immediately!" Cold sweat poured down Fan Tongyu's forehead.

After a day and a night of examination, many people were filled with despair.

“No problem. Although the area has increased, the circuitry is exactly based on the computer circuit board from Northwestern Polytechnical University!” Fan Tongxue frowned. “Could it be that scaling up is not working and we can only maintain the original proportions?”

"How could that be? After we enlarged it, the circuit is thicker and can carry more current. It should work better!" Fan Tongyu shook his head: "There must be a problem somewhere... It might be a cold solder joint. We'll build another one. This time, we'll check it more carefully. We absolutely cannot overlook anything!"

A week later, the second computer was replicated. Learning from the previous experience, the cabinet lid was not closed, and Fan Tongxue pressed the power button with trembling hands.

A few seconds later, the circuit board visibly began to smoke!

No, it still doesn't work, damn it!
　PS: The first picture is of an early circuit board, and the second picture is of a circuit board used in the modern microelectronics field.

　　
　
(End of this chapter)