PCB Technical - What to pay attention to when engaged in pcb

The PCB is the printed circuit board, which is the carrier of the electronic circuit. In modern electronic products, PCBs are almost always used.

PCB design is the last link of circuit design, and it is also the redesign of the primary circuit. Some new engineers often underestimate the importance of PCB design, and leave this tedious and troublesome work to technicians to complete. Here I first tell a story about PCB design. Because it involves the privacy of the company, the real location and company name are hidden.

The company involved in the story is a company that produces telephones. Ordinary push-button telephones are actually not a high-tech product. Compared with the early dial-type electronic telephones, it adds a dual tone/pulse dial control integrated circuit to the circuit, and some products also add free With the call function, when the user uses the phone, if he presses the hands-free button, he can answer or call out without having to pick up the phone. Those who are familiar with the basic principles of telephone circuits know that the hands-free circuit is composed of "automatic receiving/transmitting control circuit" and "audio power amplifier circuit". These circuits are implemented by ready-made dedicated ICs, and there is no need for innovative design. The place.

In the early stages of reform and opening up, some enterprises that were quick to make the first move made a fortune by producing telephones. The company I’m talking about sent the company’s latest products to the head of Beijing for a trial. This kind of push-button phone with hands-free function is indeed much easier to use than the dial phone used at the time. After a period of trial, the chief was very satisfied and agreed to recommend the product to the relevant departments.

But at this critical moment, late one night, the phone suddenly buzzed!

No special event, no one would dare to call the chief's home phone late at night. What's even stranger is that no one answered when the phone was picked up. After a while, the phone continued to beep continuously. The chief urgently called the security personnel, and the security personnel called the telecommunications personnel overnight. Finally, they figured out that the hands-free function of the phone was triggered by mistake by itself, causing a false alarm. The chief is furious!

The sales plan of the phone, so the accident was delayed for many years. Afterwards, it was found that the original cause of the hands-free false triggering was poor circuit PCB design. Later, the company’s phone products and hands-free buttons were all required to be changed to mechanical buttons, which obtained the telecom’s network access permit. This incident caused direct economic losses to enterprises as high as tens of millions of yuan.

Some designers think that PCB design is simple labor, and can be completed by using PROTEL or other software tools through automatic layout and automatic routing. If a single panel fails to connect, use a double panel. If it doesn't work, use a multilayer board or set a jumper. If a short jumper doesn't work, use a long jumper. If it doesn't work, use a jumper. Finally, you can always connect.

And I know an old engineer who did not use a computer when designing the PCB in the early years, but they could still complete the circuit PCB design with hundreds or thousands of components. Moreover, the PCB they designed is quite neat in PCB layout and wiring, with very few jumpers and crossovers, and the arrangement of the highland components is neat and reasonable, and meets the requirements of process specifications. The early domestic black-and-white TV PCBs we saw belonged to the masterpieces of engineers of their time.

Although I used a computer a long time ago when I designed the PCB. But I still feel that these old engineers must have some tricks to learn from in PCB design. Our young engineers now can hardly imagine how they used pencils and graph paper to complete complex PCB designs. Indeed, I have also gained a lot of experience from him, such as: how to arrange the components for easy wiring, how to make the most effective use of the board space under the dual in-line IC, and how to plan as much as possible before wiring. Layout and more.

PCB design is not only technology, but also art. Art involves many subjective factors, so engineers should also pay attention to improving their self-cultivation.

The tool helps us to complete a lot of complicated work, but what it does automatically is not optimally applied to every product. Because what it helps us to complete is the universal and universal aspect of product design, rather than automatically completing the best optimized surface design of the product. For example, using PROTEL or other software tools, through automatic layout and automatic routing, what can be done is just The usual connection method, from a certain aspect, is just to connect the devices to be connected together. Therefore, to really design a product's PCB, it is more about the designer's understanding and analysis of the specific situation of the product, so as to complete a unique design. I have studied PCB design for the system, but due to the primary reason to design, I used PROTEL to design a PCI board (currently studied by PROTEL). I deeply feel the complexity of PCB design (the chip used is up to 160 cited Corner double-panel wiring, without using automatic network wiring, the result is: can connect them together, minimize high-frequency interference and follow the chip’s wiring length requirements to design it has been a big headache), because of the radio Hobby, so I have a certain understanding of Yuanxian's black and white TV sets. Therefore, I deeply respect the hard work and wisdom of the older generation of PCB designers. Hope to have the opportunity to truly learn the essence of PCB design. Ho Ho, talking a lot of nonsense.

Many PCB manufacturers share the same feeling. PCB design is not a simple connection on electrical appliances. It is necessary to understand the circuit knowledge, the production process and the beauty of the design. She is indeed an art. If you want to save costs, the boss must Value this work.

A very complete original plan, due to the unreasonable wiring, is not a good product. Unreasonable wiring does cause many unexpected problems: such as circuit self-excitation, poor signal-to-noise ratio, poor separation, and high-power amplifier circuits are easy to burn. The consequences are really unimaginable.