PCB Basics Knowledge

First, PCB materials:


1. CCL: COPPER CLAD LAMINATE, referred to as CCL, or plate

a) Tg: GlassTransition Temperature, the glass transition temperature, which is the temperature at which a glassy substance converts between a glassy state and a highly elastic state (usually softened). In the PCB industry, this glassy substance generally refers to a resin. Or a dielectric layer composed of a resin and a fiberglass cloth. Our common TG sheet Tg requirements are greater than 135 ° C, medium Tg requirements greater than 150 ° C, high TG requirements greater than 170 ° C. The higher the Tg value, the better the heat resistance and dimensional stability.


b) CTI:Comparative Tracking lndex, relative leakage index (or compared to leakage index, leakage tracking index). The highest voltage value of the surface of the material that can withstand 50 drops of electrolyte (0.1% aqueous ammonium chloride solution) without forming traces of leakage, in V.


c) CTE: Coefficient of thermal expansion, which is a measure of the linear expansion coefficient of a PCB sheet. It is defined as the ratio of the increase in length per unit temperature to the original length, such as Z-CTE. The lower the CTE value, the better the dimensional stability, and vice versa.


d) TD: thermal decomposition temperature refers to the temperature at which the base resin is subjected to heat loss by 5%, which is a sign that the substrate of the printed board is heated and causes delamination and performance degradation.


e) CAF: ion migration resistance, ion migration of printed boards is the phenomenon of electrochemical insulation breakdown on an insulating substrate, which refers to the application of a voltage on a circuit that is close to each other on a printed board, under the action of an electric field. The state of dendritic metal is precipitated between the wires, or metal ion migration (CAF) occurs along the surface of the glass fiber of the substrate, thereby reducing the insulation between the wires.


f) T288: It is a technical index reflecting the soldering condition of the printed board substrate. It refers to the longest time that the substrate of the printed board is subjected to soldering high temperature at 288 °C without causing decomposition phenomena such as foaming and delamination. The more time this is, the better the welding.


g) DK: dielectric constant, dielectric constant, often called dielectric constant.


h) DF: dissipation factor, the dielectric loss factor, refers to the energy that has been lost in the insulating sheet in the signal line, and the ratio of energy in the line.


i) OZ: oz is the abbreviation of the symbol ounce, the Chinese called "ounce" (Hong Kong is translated as oz) is an English unit of measurement, also known as the British two as a weight unit; 1OZ means that the weight of 1OZ of copper is evenly tiled in 1 The thickness achieved over an area of square feet (FT2), which is the weight per unit area used to represent the average thickness of the copper foil. Expressed by the formula, 1OZ = 28.35g / FT2.


2. Copper foil: COPPER FOIL

a) ED copper foil: electrolytic copper foil, PCB commonly used copper foil, the price is cheap


b) RA copper foil: rolled copper foil, FPC common copper foil


c) Drum Side: smooth surface, smooth surface of electrolytic copper foil


d) Matt side: rough surface, rough surface of electrolytic copper foil


e) Copper: Elemental symbol Cu, atomic weight 63.5, density 8.89 g/cm 3 , Cu2+ electrochemical equivalent weight 1.186 g/ampere hour.