Our common computer boards and cards are basically epoxy resin glass cloth based double-sided printed circuit boards. One side is the plug-in components, and the other side is the welding surface of the component feet. It can be seen that the welding points are very regular. The discrete welding surface of the component feet of these welding points is called pad. Why can't other copper conductor patterns be tin. Because there is a layer of wave soldering resistant solder resist film on the surface of other parts except the pads that need soldering. Most of its surface solder resist films are green, and a few adopt yellow, black, blue, etc., so solder resist oil is often called green oil in PCB industry. Its function is to prevent bridging during wave welding, improve welding quality and save solder. It is also a permanent of printed boards The long-lasting protective layer can prevent moisture, corrosion, mildew and mechanical abrasion. Viewed from the outside, the green solder resist film with smooth and bright surface is a photosensitive heat curing green oil for film pair plate. Not only the appearance is good-looking, but also the accuracy of the pad is high, which improves the reliability of the solder joint.
We can see from the computer board that there are three ways to install components. The utility model relates to a plug-in installation process for transmission, in which electronic components are inserted into the through hole of a printed circuit board. In this way, it is easy to see that the through holes of double-sided printed circuit board are as follows: first, simple component insertion holes; Second, component insertion and double-sided interconnection through holes; Third, simple double-sided through holes; The fourth is the base plate installation and positioning hole. The other two installation methods are surface installation and chip direct installation. In fact, chip direct installation technology can be regarded as a branch of surface installation technology. It is to stick the chip directly to the printed board, and then interconnect it to the printed board with wire welding method, tape carrying method, flip chip method, beam lead method and other packaging technologies. The welding surface is on the element surface.
Surface mount technology has the following advantages:
1. Because the printed board largely eliminates the interconnection technology of large through holes or buried holes, it improves the wiring density on the printed board, reduces the area of the printed board (generally one-third of that of plug-in installation), and reduces the number of design layers and cost of the printed board.
2. The weight is reduced, the seismic performance is improved, and the colloidal solder and new welding technology are adopted to improve the product quality and reliability.
3. As the wiring density is increased and the lead length is shortened, the parasitic capacitance and parasitic inductance are reduced, which is more conducive to improve the electrical parameters of the printed board.
4. Compared with the plug-in installation, it is easier to realize automation, improve the installation speed and labor productivity, and reduce the assembly cost accordingly.
From the above surface mount technology, we can see that the improvement of circuit board technology is improved with the improvement of chip packaging technology and surface mount technology. Now we see that the surface adhesion rate of computer boards and cards is rising. In fact, this kind of circuit board can't meet the technical requirements of screen printing circuit graphics with transmission. Therefore, for ordinary high-precision circuit board, its circuit pattern and solder resist pattern are basically made of photosensitive circuit and photosensitive green oil.
With the development trend of high density of circuit board, the production requirements of circuit board are higher and higher. More and more new technologies are applied to the production of circuit board, such as laser technology, photosensitive resin and so on. The above is only a superficial introduction. There are still many things not explained in the production of circuit board due to space limitations, such as blind buried hole, wound board, Teflon board, lithography technology and so on
