PCB is the abbreviation of printed circuit board. A conductive pattern formed on a dielectric material in a predetermined design to form a printed circuit, a printed component, or a combination of the two is generally referred to as a printed circuit. A conductive pattern that provides an electrical connection between components on an insulating substrate is referred to as a printed circuit. Thus, the finished board of printed circuit or printed circuit is called printed circuit board, also known as printed board or printed circuit board.
PCBs are almost indispensable to the electronic devices we can see. From electronic watches,calculators,general-purpose computers, computers, communication electronic devices, military weapon systems, as long as there are electronic devices such as integrated circuits. The PCBs are used for electrical interconnections.
It provides mechanical support for fixed assembly of various electronic components such as integrated circuits, realizes wiring and electrical connection or electrical insulation between various electronic components such as integrated circuits, and provides required electrical characteristics such as characteristic impedance. At the same time, it provides solder resist pattern for automatic soldering; it provides identification characters and graphics for component insertion, inspection and maintenance.
PCB production process is more complicated, it involves a wide range of processes, from simple machining to complex machining, common chemical reactions and photochemical electrochemical thermo chemistry, computer-aided design CAM and other aspects of knowledge . Moreover, there are many technical problems in the production process and new problems will be encountered from time to time.
Some problems will disappear if the cause is not found out. Because the production process is a non-continuous pipeline form, any problem will cause the whole line to be discontinued. Or the consequences of a large number of scraps, printed circuit boards can not be recycled if they are scrapped, process engineers have a lot of work pressure, so many engineers left the industry to switch to printed circuit board equipment or materials manufacturers to do sales and technical services.
Our common computer board is basically an epoxy resin glass cloth base double-sided printed circuit board, one of which is the inserting component on the other side and the component foot soldering surface. It can be seen that the solder joints are very regular. The component foot is separated from the solder joint and we call it the pad.
Why are other copper wire patterns not tinned? Because the surface of the remaining portion has a solder mask that is resistant to wave soldering except for the solder pad. The surface solder mask is mostly green, and a few are yellow, black, blue, etc., so the solder resist oil is often called green oil in the PCB industry. Its function is to prevent bridging during wave soldering, improve soldering quality and save solder.
For printed boards, there is also a permanent protective layer that protects against moisture, mechanical abrasion and mildew. Once we look from outside, we can see the surface is smooth with bright green solder mask oil ,The oil is a photo-curing green one for the film, In this way, the appearance look better, and the pad has a higher accuracy ,which improves the reliability of the solder joint.
Normally for the computer board there are three ways to install components. A plug-in mounting process for a drive that inserts electronic components into the vias of a printed circuit board.
Thus, it is easy to see that the through holes of the double-sided printed circuit board are as follows: one is a simple component insertion hole; the other is a component insertion and a double-sided interconnection via; and the third is a simple double-sided guide. The through hole; the fourth is the substrate mounting and positioning hole.
The other two installation methods are surface mounting and direct chip mounting. In fact, the direct mounting technology of the chip can be considered as a branch of the surface mounting technology. It is to directly bond the chip to the printed board, and then interconnected by wire bonding or carrier tape method, flip chip method, beam lead method and other packaging technologies. On the board. Its welding surface is on the component surface.
Surface mount technology has the following advantages:
1. Since the printed board largely eliminates the large via or buried via interconnection technology, the wiring density on the printed board is increased, and the printed board area is reduced (generally one of the three steps of the plug-in installation), It also reduces the number of layers and cost of the printed board.
2. Reduced weight and improved seismic performance. Glued solder and new welding technology are used to improve product quality and reliability.
3. To improve the electrical parameters of the PCBs, the wiring density will increase, and the lead length and parasitic capacitance will be shortened.
4. It is easier to automate than plug-in installation, increasing installation speed and labor productivity, and correspondingly reducing assembly costs.
It can be seen from the above surface security technology that the improvement of the circuit board technology is improved with the improvement of the packaging technology and surface mounting technology of the chip.
Nowadays, the surface sticking rate of the computer boards we are watching is constantly rising. In fact, such a circuit board reuse transmission screen printing circuit graphics can not meet the technical requirements. Therefore, the ordinary high-precision circuit board, the line pattern and the solder resist pattern basically adopt the photosensitive line and the photosensitive green oil manufacturing process.
With the development trend of high density of circuit boards, the production requirements of circuit boards are getting higher and higher, and more and more new technologies are applied to the production of circuit boards, such as laser technology, photosensitive resins and the like.
The above is just a superficial introduction to some surfaces. There are still many things in the production of circuit boards that are not specified due to space limitations, such as blind buried holes, wound plates, Teflon plates, lithography and so on. If you want to conduct in-depth research, you need to work hard.