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Power supply circuit board

Power supply circuit board


A printed circuit board is a plate where a layer with conductive paths is formed. The electronic components that are installed on the board are connected by their terminals to the elements of the master pattern by soldering, or, much less commonly, welding, resulting in an electronic module.

Any electronic device is a set of tens, hundreds, or even thousands of components. Each of them has its own purpose and a clearly defined place in the scheme. All of them are connected by a network of wires into a single structure.

Interesting to know
At the beginning of the development of the field of electrical devices, the electrical components were large, and the device circuits were quite simple. Details were placed on contact pads or screwed to the body, they were interconnected using ordinary wires. This method is called - mounted mounting.

The assembly and repair of such devices was carried out exclusively by hand, which caused many difficulties and increased the cost of production. These were the days of electromagnetic relays and vacuum tubes, by today's enormous standards. But progress did not stand still and scientists learned to use semiconductors.

Miniature transistors and microcircuits came to replace the lamps. They revolutionized the world of electronics. Every year, devices became more complex and more compact. Instead of cumbersome mounting, printed circuit boards appeared. They took a dominant position in the production of electronic devices in the 50s of the last century.

The idea of ​​placing components on a dielectric plate was not new, but the previously used methods of gluing, spraying, and chemical deposition of conductive paths had drawbacks, and the engineers borrowed the sutractive technology from the printing house. Therefore, boards made in this way were called printed.

Production technology for power supply printed circuit boards
It all starts from a blank - an insulating plate coated with copper foil. A light-sensitive coating, a photoresist, are applied to its surface, and irradiated with ultraviolet light through a stencil with a pattern of future tracks. Photoresist covers the entire surface of the workpiece, and the stencil darkens those places where there should be no metallization. Under the influence of ultraviolet radiation, the properties of the photoresist change and the pattern is transferred to the workpiece. The unlit photoresist is easily washed off in the developing solution. The one that has been exposed becomes completely insoluble and is firmly fixed to the metal surface. After that, the workpiece is placed in an etching solution. A chemical reaction begins: the open metal dissolves easily, but there is no reaction under the photoresist layer, since the foil is protected and remains unharmed.

After removing the photoresist, copper tracks become visible, they firmly hold on the insulating base, and will connect and hold electronic components. To connect the tracks in different layers, a hole is drilled and electrochemically metallized.

To protect the tracks from environmental influences and facilitate soldering, the board is coated with a special varnish. It forms a solder mask. Most often they use green, but some manufacturers prefer to use other colors. Such a liquid mask is applied to the entire surface of the board and, like a photoresist, is irradiated through a stencil. The illuminated varnish hardens, and the shaded stencil remains liquid and is easily washed off, leaving contact pads. That is, places to which components will be soldered.

Printed circuit boards are divided into:

  • unilateral;
  • bilateral;
  • multilayer.

The most popular are double-sided printed circuit boards. With their help, you can make more complex schemes. Such boards on a metal base have greater resistance to temperature differences, so the linear expansion coefficients of the substrate material and the special hole are approximately equal.

Multilayer printed circuit boards consist of layers of insulating material and a leading pattern that alternate. There are several types of such boards, distinguishing them in the design and technological parameters.

In addition, printed circuit boards can be divided into:

  • hard;
  • flexible.

More popular in the production of power supplies, today, are flexible printed circuit boards. They are used for electrical connection of nodes, the design of which eliminates the use of rigid boards. Advantages of flexible boards are that they have an elastic base and are usually made double-sided with special holes and places for soldering attachments.

A feature of printed circuit boards of power supplies is that they must perform the functions of a voltage converter, turn standard 220V household electrical outlets into voltages necessary for the operation of a computer or other electrical appliances. PC components are powered by strictly defined voltage ratings, any deviation from which can cause incorrect operation, malfunction, or simply failure of voltage-sensitive components. The power supply must ensure the stability of six voltages: 12V, + 5V, + 3.3V, -5 V, -12 V and +5 V standby mode (with an error of 5% for positive and 10% for negative; -5 V, -12 In rarely used for nutrition).

The power of modern power supplies is 350-400 watts. And processors have increased power consumption, so this figure should be high. In addition to providing the computer with the necessary voltage, the power supply board is also required to protect the PC from too high a voltage (220 V).

The issue of electrical safety is very strictly regulated by both international and existing standards in the Russian Federation.

The power supply is the most complex and important part of the electrical appliance and you need to treat it accordingly, it is individually designed, depending on the electronic circuit and types of parts housings. For their development, there is special software that allows you to create circuit drawings, choose the best placement of electronic components (to achieve the shortest length of conductive tracks, balance signal lines, reduce the number of jumpers or track layers, etc.), generate photo templates and instructions for manufacturing of printed circuit boards on CNC machines. The manufacture of printed circuit boards is carried out by chemical, electrochemical or combined methods, and recently the additive method has also gained distribution.

The materials used for the manufacture of printed circuit boards of the power supply must have high electrical insulating properties and sufficient mechanical strength. For the manufacture of printed circuit boards apply foil and non-foil sheet dielectric materials. But the most popular are foil dielectrics.

Formation of the pattern of printed circuit boards of power supplies is carried out using silk-screen printing, offset printing or photochemical method.

Our experts are engaged in the design of printed circuit boards of varying complexity. All of them comply with international standards of the IPC Association and GOST of the Russian Federation. Years of experience in the manufacture of boards allows us to easily understand the needs of customers and offer them the most optimal solutions.