In a circuit withresistance, inductance and capacitance, the resistance to alternating currentis called impedance. Impedance is usually represented by Z, which is a complexnumber. The real part is called resistance and the imaginary part is calledreactance. The blocking effect of capacitance on AC in the circuit is calledcapacitive reactance, the blocking effect of inductance on AC in the circuit iscalled inductive reactance, and the blocking effect of capacitance andinductance on AC in the circuit is called reactance. The unit of impedance isOhm.
PCB circuit boardimpedance refers to the parameters of resistance and reactance, which hinderthe AC. Impedance treatment is essential in PCB production. The reasons are asfollows:
<span lang="EN-US" style=""font-size:12.0pt;line-height:150%;font-family:"Times New Roman",serif;">1. ThePCB circuit (bottom of the board) should consider inserting and installingelectronic components. After inserting, the problems such as conductivity andsignal transmission performance should be considered. Therefore, the lower theimpedance, the better, and the resistivity should be lower than 1 &times per square centimeter; Below 10-6.
<span lang="EN-US" style=""font-size:12.0pt;line-height:150%;font-family:"Times New Roman",serif;">2. Inthe production process, PCB circuit board shall go through copper deposition,electro tin plating (or electroless plating, or thermal tin spraying),connector soldering and other process manufacturing links, and the materialsused in these links must ensure the bottom resistivity, so as to ensure thatthe overall impedance of the circuit board is low, meet the product qualityrequirements and operate normally
3. The tinning ofPCB is the most likely problem in the whole PCB manufacturing, and it is thekey link affecting the impedance. The biggest defects of electroless tinplating layer are easy to change color (easy oxidation or deliquescence) andpoor brazing, which will lead to difficult welding of circuit board, highimpedance, poor conductivity or unstable performance of the whole board.