PCB Technical - Four specifications for PCB board classification

In fact, the printed PCB circuit boards used in electronic equipment are different, and the printed PCB circuit boards have different classifications according to different specifications. 1. Classification according to the distribution of printed circuits. According to the distribution of printed circuits, the circuit boards can be divided into three types: single-sided aluminum substrate, double-sided board, and multi-layer high-level board. Single-sided aluminum substrate single-sided aluminum substrate is 0.2-5mm in thickness Only one surface layer can be covered with copper foil on the insulating base steel plate, and a printed circuit is produced on the base steel plate according to the printing and etching methods. Simple manufacturing of single-sided aluminum substrate

In fact, the printed PCB circuit boards used in electronic equipment are different, and the printed PCB circuit boards have different classifications according to different specifications.

1. Classified according to the distribution of printed circuits

According to the printed circuit, the circuit board can be divided into three types: single-sided aluminum substrate, double-sided board, and multi-layer high-level board.

• Single-sided aluminum substrate

The single-sided aluminum substrate is an insulating base steel plate with a thickness of 0.2-5mm, and only one surface can be covered with copper foil, and a printed circuit is produced on the base steel plate according to the printing and etching methods. The single-sided aluminum substrate is easy to PCB produce and PCB manufacture, and the assembly line is convenient. It is suitable for charging and discharging circuit regulations, such as tape recorders, TVs, etc.; discomfort is used to specify places with high assembly relative density or complicated power circuits.

• Double panel

The double-sided board is to print the circuit on both sides of the insulating layer base steel plate with a thickness of 0.2-5mm. It applies to electronic equipment generally specified, such as computers, instruments and dashboards. Because the relative density of double-sided printed circuits is higher than that of single-sided aluminum substrates, the volume of machinery and equipment can be reduced.

Printed circuit boards with about 3 layers of printed circuits printed on the insulating base steel plate are called solid wood multilayer boards. This is composed of multiple thin single-sided aluminum substrates or double-sided panels, and its thickness is generally 1.2-2.5mm. In order to find the power circuit sandwiched in the middle of the insulating base steel plate, the holes for mounting components on the solid wood multilayer board must be metalized, that is, the surface layer of the small round hole is coated with a layer of metal material, so that it is sandwiched between the insulating layer. The printed circuit in the middle of the base steel plate is connected.

The following figure is a plan view of the solid wood multilayer board structure. The commonly used components of solid wood multilayer board are mostly SMD components, and their characteristics are:

1. Cooperating with integrated circuit chips can make the entire equipment practical and reduce the net weight of the entire equipment;

2. Improve the relative density of traces, reduce the interval of electronic devices, and reduce the transmission path of data signals;

3. Reduced the solder joints of electronic devices and reduced the repair rate;

4. The shielding layer is added to reduce the frame loss of the data signal of the power circuit;

5. The heat pipe heat dissipation layer of the grounding device is introduced, which can reduce some over-temperature conditions and improve the credibility of the entire equipment in operation;

Second, classified according to the characteristics of the board

According to the characteristics of the board, the circuit board can be divided into rigidity and softness.

Rigid printed circuit board

The rigid printed circuit board has a certain impact toughness, and the components dressed up with it have a leveling condition. Generally, rigid printed circuit boards are used in general electronic equipment.

Flexible printed circuit board

The flexible printed circuit board should be made of soft mylonite plastic or other soft plastic insulating layer materials. The components made of it can be bent and telescopic, and can be bent according to the installation regulations during application. Flexible printed circuit boards are generally used in unique places. For example, the display of some digital multimeters can be rotated, and flexible printed circuit boards are usually used inside; displays, function keys, etc. on mobile phones.

The following picture shows the flexible printed circuit board on the mobile phone. The board is made of polyimide, and the surface layer has been rust-removed. The minimum graphic boundary line distance is set to 0.1mm. The protruding characteristic of the flexible printed circuit board is that it can be bent, rolled, stretched, and can be connected to rigid printed circuit boards and thematic movable components, and then can be three-dimensionally routed to maintain three-dimensional spatial interconnection. It is light in weight and very Lightweight and convenient assembly line, it is suitable for electronic equipment with small indoor space and relatively high assembly density.

3. Classified by application field

According to the application field, the circuit board can be divided into two types: high-frequency and high-frequency circuit boards.

The high frequency of electronic products is the development trend, especially in today's wifi network and satellite communications are developing trends, information content products are moving towards high speed and high frequency, and communication products are moving towards larger and faster wireless data transmission. Standardization of video, voice, video and statistical data. Therefore, the new generation of products in the development trend must be high-frequency printed circuit boards, and the foil-clad plates can be made of raw materials with low dielectric loss and dielectric constant such as polytetrane ethylene, high ethylene, polyethylene, polytetrafluoroethylene laminated glass cloth, etc. composition.

4, the type of unique printed circuit board

At this stage, some unique printed circuit boards such as metal core printed circuit boards, surface mounted printed circuit boards, and carbon film printed circuit boards have also appeared.

Metal material core printed circuit board

The metal material core printed circuit board is to replace the epoxy laminated glass cloth board with a thin and very thick metal sheet. After a unique solution, the electrical conductor power circuit on both sides of the gold board is connected to each other, and part of the metal material is high. Width ratio insulating layer. The advantage of the metal core printed circuit board is that the heat pipe has good heat dissipation and specification reliability. This is due to the shielding effect of magnetic materials such as aluminum and iron, which can avoid mutual interference.

Surface mounted printed circuit board

The surface-mounted PCB is a printed board that can meet the "light, thin, short, and small" requirements of electronic equipment, and is developed and designed to cooperate with the relative density of pins and the installation and processing technology of low-cost surface patch components. The printed circuit board has the characteristics of small diameter, small pattern boundaries and intervals, high precision, and base steel plate.

Carbon film PCB

The carbon film PCB is a printed circuit board on which the electrical conductor pattern is made on the copper-plated board, and then a layer of carbon film is printed to produce contact points or jumpers (resistance meets the requirements). Its characteristics are simple production process, low cost, short cycle time, excellent wear resistance, electrical conductivity, can maintain the density of single-sided aluminum substrate, commercialization, light weight, suitable for TV, telephone, hard disk video recorder and Products such as electronic organs.