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Composition factors of printed circuit board

Composition factors of printed circuit board

(1) CCL. Copper Clad Laminate (full name copper clad laminate, CCL for short) is made of wood pulp paper or fiberglass cloth, immersed in resin, coated with copper foil on one or both sides, and hot pressed. A product, as shown in Figure 1. CCL is a basic material for the electronics industry. It is mainly used in the manufacture of printed circuit boards and is widely used in electronic products such as televisions, radios, computers, and mobile communications.


(2) Copper foil wire. The substrate of the PCB itself is made of a copper clad laminate that is insulated and insulated and is not easily bent. The thin circuit material that can be seen on the surface is copper foil. The original copper foil is covered on the whole board, and part of the manufacturing process is etched away, and the remaining part becomes a mesh-like small line, such as Figure 2 shows. These lines are called wires or wires and are used to provide electrical connections to the parts on the PCB board and are an important part of the PCB board. The main attribute of the wire is the width, which depends on the amount of current carried and the thickness of the copper foil.

On printed circuit boards, copper foil has a certain impact on the electrical performance of electronic products. Copper foil can be divided into two types: rolled copper foil and electrolytic copper foil according to the manufacturing method. Calendered copper foil requires copper purity ≥99.9%, which is represented by the letter W. Its copper foil has good elasticity and good solderability, and is suitable for high-performance PCB. Electrolytic copper foil requires copper purity equal to 99.8%, which is represented by the letter E, which can be soldered. Slightly poor, suitable for ordinary PCB.

Common copper foil thickness is 9um, 12um, 18um. 35um, 70um, etc., of which 35um is used more. The thinner the copper foil, the worse the temperature resistance, and the leaching will penetrate the copper foil; if the copper foil is too thick, it will fall off easily.

(3) Pad. The pads are used to solder the components for electrical connection and at the same time function as a fixed component. The basic properties of the pad are shape, layer, outer diameter and aperture. Both the double-layer and multi-layer pads are metallized through the walls of the holes.

(4) Via holes. Vias are used to achieve electrical connections between different working layers, and the inner walls of the vias are also metallized. Vias only provide electrical connections between the different layers, regardless of soldering and fixing of the component leads.



There are three types of vias. The through-holes or through-holes from the top layer to the bottom layer; the vias that only connect the top layer or the bottom layer to the middle layer are called blind holes, which reduces the depth of the holes; only the intermediate layer connection is achieved without wearing The vias that penetrate the top or bottom layer are called buried vias, which further reduce the depth of the holes. The three types of holes are shown in Figure 3. Although blind holes and buried holes are difficult to fabricate, they greatly improve the reliability of SMB manufacturing. Through the SMB light board test, it can be judged whether the line network is connected, and there is no need to worry about the metallized hole being broken due to external unknown factors during the use of the product.

(5) Other supporting explanation information. In order to read the PCB or assembly, debugging and other needs, you can add some auxiliary information, including graphics or text. The graphical symbol of the component reflects the shape and size of the outline of the component and, together with the pin layout of the component, forms the package of the component. The purpose of the graphic symbol of the printed component is to display the layout information of the component on the PCB, which is convenient for assembly, debugging and maintenance.