Single-sided printed circuit boards were developed in the United States with the emergence of transistors in the early 1950s. At that time, the main production method was the direct etching of copper foil. From 1953 to 1955, Japan used imported copper foil to make paper phenolic copper foil substrate for the first time, and it was widely used in radios. In 1956, after the emergence of a professional Japanese circuit board manufacturer, the manufacturing technology of single-sided panels developed rapidly.
In terms of materials, paper-based phenolic copper foil substrates were mainly used in the early days. However, due to factors such as low electrical insulation, poor soldering heat resistance, and distortion of phenolic materials, paper-based atmospheric resins, glass fiber epoxy resins, etc. Developed, the single-sided panels required by current consumer electronic machines almost use paper phenolic substrates.
Features of single panel:
The single-sided board is on the most basic PCB, the parts are concentrated on one side, and the wires are concentrated on the other side. Because the wires only appear on one side, we call this kind of PCB a single-sided (Single-sided). Because single-sided boards have many strict restrictions on the design of the circuit (because there is only one side, the wiring cannot cross and must be around a separate path), only early circuits use this type of board;
Single-panel wiring diagrams are mainly screen printing, that is, a resist is printed on the copper surface, and after etching, the mark is printed with a solder mask, and finally the part guide hole and the part are completed by punching. shape. In addition, some products that are produced in small quantities and diversified use photoresist to form patterns.
Double-sided circuit board
There are wiring on both sides of Double-Sided Boards. However, to use wires on both sides, there must be a proper circuit connection between the two sides. The "bridge" between such circuits is called a via. A via is a small hole filled or coated with metal on the PCB, which can be connected to the wires on both sides. Because the area of the double-sided board is twice as large as that of the single-sided board, and because the wiring can be interleaved (it can be wound to the other side), it is more suitable for use in circuits that are more complicated than the single-sided board.
Strictly speaking, the double-sided board is a very important PCB board in the circuit board. Its use is very large. It is also very simple to see whether a PCB board is a double-sided board. I believe that friends can understand the single-sided board. If you are sure, the double-sided board is an extension of the single-sided board, which means that the circuit of the single-sided board is not enough to turn to the reverse side. The important feature of the double-sided board is the through hole. Simply put, it is double-sided routing, with lines on both sides! One sentence is: a double-sided wiring board is a double-sided board! Some friends will ask, for example, a board with double-sided wiring, but only one side has electronic components. Is this board a double-sided or a single-sided board? The answer is obvious. Such a board is a double-sided board. It is just that parts are installed on the double-sided board.
Simple distinction between multilayer circuit boards
Circuit boards determine the process difficulty and processing price according to the number of wiring surfaces. Common circuit boards are divided into single-sided wiring and double-sided wiring, commonly known as single-sided and double-sided. However, high-end electronic products are restricted by product space design factors. In addition to the surface wiring, multiple layers of circuits can be superimposed inside. During the production process, after each layer of wiring is made, it is positioned and pressed by optical equipment, so that the multilayer circuits are superimposed on a circuit board. Commonly known as multilayer circuit boards. Any circuit board with more than or equal to 2 layers can be called a multilayer circuit board. Multilayer circuit boards can be divided into multilayer rigid circuit boards, multilayer soft and hard circuit boards, and multilayer soft and hard circuit boards.
The birth of multilayer circuit boards
The increase in the packaging density of integrated circuits has resulted in a high concentration of interconnect lines, which necessitates the use of multiple substrates. In the layout of the printed circuit, unforeseen design problems such as noise, stray capacitance, and crosstalk have appeared. Therefore, the printed circuit board design must focus on minimizing the length of signal lines and avoiding parallel routes. Obviously, in single-panel, or even double-panel, these requirements cannot be satisfactorily answered due to the limited number of crossovers that can be achieved. In the case of a large number of interconnection and crossover requirements, to achieve a satisfactory performance of the circuit board, the board layer must be expanded to more than two layers, thus a multilayer circuit board has appeared. Therefore, the original intention of manufacturing multi-layer circuit boards is to provide more freedom for selecting appropriate wiring paths for complex and/or noise-sensitive electronic circuits. Multilayer circuit boards have at least three conductive layers, two of which are on the outer surface, and the remaining layer is integrated into the insulating board. The electrical connection between them is usually achieved through plated through holes on the cross section of the circuit board. Unless otherwise specified, multi-layer printed circuit boards, like double-sided boards, are generally plated through holes.
Multilayer boards are made by stacking two or more circuits on top of each other, and they have reliable pre-set interconnections. Since drilling and plating have been completed before all the layers are rolled together, this technique violates the traditional manufacturing process from the beginning. The two innermost layers are composed of traditional double panels, while the outer layers are different, they are composed of independent single panels. Before rolling, the inner plate will be drilled, through-hole plating, pattern transfer, development and etching. The outer layer to be drilled is the signal layer, which is plated through in such a way that a balanced copper ring is formed on the inner edge of the through hole. The layers are then rolled together to form a multi-substrate, which can be connected to each other (between components) using wave soldering.
Rolling may be done in a hydraulic press or in an overpressure chamber (autoclave). In the hydraulic press, the prepared material (for pressure stacking) is placed under cold or preheated pressure (the material with high glass transition temperature is placed at a temperature of 170-180°C). The glass transition temperature is the temperature at which an amorphous polymer (resin) or part of the amorphous region of a crystalline polymer changes from a hard, rather brittle state to a viscous, rubbery state.
Multilayer boards are put into use in professional electronic equipment (computers, military equipment), especially when the weight and volume are overloaded. However, this can only be achieved by increasing the cost of the multilayer board in exchange for an increase in space and a reduction in weight. In high-speed circuits, multi-layer boards are also very useful. They can provide designers of printed circuit boards with more than two layers of board surface to lay wires and provide large grounding and power supply areas.