PCB News - Circuit board knowledge in PCBA processing service

Circuit board knowledge in PCBA processing service
1. Printed circuit board (PCB)
PCB is the abbreviation for Printed Circuit Board. Also known as printed circuit board, printed circuit board, because it is made by electronic printing, it is called "printed" circuit board. The printed circuit board is a substrate for assembling electronic parts. It is a printed board that connects dots and prints components on a common base material according to a predetermined design. The main function of this product is to make various electronic components form a predetermined circuit connection, which plays the role of relay transmission. It is the key electronic interconnection of electronic products and is known as the "mother of electronic products". PCB is used as a substrate and key interconnection for electronic parts, and any electronic equipment or product needs to be equipped.
Second, the manufacturing principle of PCBA processing
When we open the keyboard of a general-purpose computer, we can see a piece of soft film (flexible insulating substrate), printed with silver-white (silver paste) conductive patterns and healthy bit patterns. Because the general screen printing method obtains this kind of pattern, we call this kind of printed circuit board a flexible silver paste printed circuit board. The printed circuit boards on the various computer motherboards, graphics cards, network cards, modems, sound cards and household appliances that we saw in the Computer City were different. The substrate used in it is made of paper base (usually used for single-sided) or glass cloth base (usually used for double-sided and multilayer), pre-impregnated with phenolic or epoxy resin, and the surface layer is laminated with copper-clad film on one or both sides and then laminated to cure Become. This kind of circuit board copper clad sheet material, we call it rigid board. And then make a printed circuit board, we call it a rigid printed circuit board. We call single-sided printed circuit boards with printed circuit patterns on one side, and printed circuit boards on both sides with printed circuit patterns on both sides. The printed circuit boards formed by double-sided interconnection through hole metallization are called double-sided boards. If one double-sided as the inner layer, two single-sided as the outer layer, or two double-sided as the inner layer and two single-sided as the outer layer of the printed circuit board, the positioning system and the insulating bonding material alternate together and The printed circuit board with the conductive pattern interconnected according to the design requirements becomes a four-layer or six-layer printed circuit board, also called a multilayer printed circuit board. There are now more than 100 layers of practical printed circuit boards.
Third, the production process of PCB
The production process of PCBA processing is relatively complex, and it involves a wide range of processes, from simple mechanical processing to complex mechanical processing, common chemical reactions, photochemical, electrochemical, thermochemical and other processes, computer-aided design CAM, and many other aspects. knowledge. Moreover, there are many process problems in the production process and new problems will be encountered from time to time. Some of the problems disappear without finding out the cause. Because the production process is a non-continuous assembly line form, any problem in any link will cause the entire line to stop production. Or as a result of a large number of scraps, if printed circuit boards are scrapped, they cannot be recycled and reused. The work pressure of process engineers is relatively high, so many engineers have left the industry and turned to printed circuit board equipment or material vendors to do sales and technical services. .
The base plate of the board itself is made of materials that are insulated and not easy to bend. The small circuit material that can be seen on the surface is copper foil. The copper foil was originally covered on the entire board, but part of it was etched away during the manufacturing process, and the remaining part became a network of small lines. . These lines are called conductor patterns or wiring, and are used to provide circuit connections for parts on the PCB.

In order to fix the parts on the PCB, we solder their pins directly on the wiring. On the most basic PCB (single panel), the parts are concentrated on one side, and the wires are concentrated on the other side. In this way, we need to make holes in the board so that the pins can pass through the board to the other side, so the pins of the parts are welded to the other side. Because of this, the front and back sides of the PCB are called Component Side and Solder Side respectively.
If there are some parts on the PCB that need to be removed or reinstalled after the production is completed, then the socket will be used when installing the part. Since the socket is directly welded to the board, the parts can be disassembled and assembled at will.
If you want to connect two PCBs to each other, we generally use an edge connector commonly known as "golden finger". There are many exposed copper pads on the golden fingers, which are actually part of the PCB wiring. Usually when connecting, we insert the golden finger on one PCB into the appropriate slot on the other PCB (generally called the expansion slot Slot). In computers, display cards, sound cards or other similar interface cards are connected to the motherboard by golden fingers.
The green or brown on the PCB is the color of the solder mask. This layer is an insulating protective layer, which can protect the copper wire and prevent the parts from being welded to the wrong place. Another layer of silk screen will be printed on the solder mask. Usually words and symbols (mostly white) are printed on this to mark the position of each part on the board. The screen printing surface is also called the icon surface (legend).
The printed circuit board etches the complex circuit copper wires between parts and parts on a board after careful and neat planning, and provides the main support for the installation and interconnection of electronic components. It is indispensable for all electronic products. The basic parts.
The printed circuit board is a flat plate made of non-conductive materials. The flat plate is usually designed with pre-drilled holes to install chips and other electronic components. The holes of the PCBA processing components help to electronically connect the pre-defined metal paths printed on the board surface. After the pins of the electronic components are passed through the PCB, they are formed by attaching conductive metal welding rods to the PCB. Circuit.