What is the significance of impedance in PCB circuit boards, and why is impedance required in PCB circuit boards? This article first introduces what impedance is and the types of impedance, followed by an explanation...

Why PCBs Need Impedance: An Explanation of the Significance of Impedance in PCB Circuit Boards, follow the editor to learn more.

What is Impedance?

In circuits with resistance, inductance, and capacitance, the opposition to alternating current is called impedance. Impedance is commonly represented by the letter Z and is a complex number, with the real part being the resistance.

The imaginary part is called reactance, where the capacitive opposition to AC in a circuit is known as capacitive reactance, and the inductive opposition to AC in a circuit is known as inductive reactance.

Reactance, capacitance, and inductance are collectively referred to as electrical reactance for their resistive effects on AC current in a circuit. The unit of impedance is the ohm.

Two: Solder Mask Type

Characteristic impedance, in electronic products such as computers and wireless communications, refers to the energy transmitted through PCB lines, which is a square waveform composed of voltage and time.

Square wave signal, also known as a pulse, encounters resistance called characteristic impedance.

Two identical signal waveforms with opposite polarities at the differential impedance drive input are transmitted via two separate differential lines. At the receiving end, these differential signals are subtracted. Differential impedance...

Zdif is the impedance between the two lines.

(3) The Zo impedance between the two lines and the ground in the Qimode is consistent across both lines.

(4) The impedance Zcom when two identical signal waveforms with the same input polarity on the偶模 impedance drive terminal are connected together.

(5) Common-mode impedance between one wire and ground in a two-wire setup, Zoe, the impedance values of the two wires are consistent, and it is typically higher than differential-mode impedance.

Why PCB Circuit Boards Require Impedance

PCB impedance refers to the parameters of resistance and reactance, which act as a hindrance to alternating current. Impedance management is an indispensable part of PCB manufacturing.

Due to the following:

1. PCB routing (bottom layer) must consider the installation of electronic components, and after installation, factors such as conductivity and signal transmission performance need to be taken into account, thus requiring lower impedance.

Good, the resistivity must be lower than 1 x 10^-6 ohm-cm.

2. During the manufacturing process of PCB circuit boards, they must undergo several production stages, including copper immersion, tin electroplating (or chemical plating, or hot spray soldering), and connector soldering, among others.

Materials must ensure a low resistivity to guarantee the overall impedance of the printed circuit board is low, meeting product quality requirements and enabling normal operation.

3. Tin plating on PCB circuit boards is a place where problems often arise during the entire manufacturing process, and it's a crucial factor affecting impedance. One significant defect of electroless tin plating layers is...

Easily discolorable (due to oxidation or hygroscopic), poor solderability can lead to difficulty in焊接 PCBs, excessive impedance causing poor conductivity or inconsistent performance of the entire board.

4. Conductors within PCBs carry various signals. When it is necessary to increase the transmission speed by raising the frequency, the lines themselves may suffer due to etching or lamination thickness...

Differences in factors such as wire width will cause variations in impedance values, leading to signal distortion and a decrease in the performance of the printed circuit board. Therefore, controlling the impedance value is necessary.

Within a certain scope.

The Significance of Impedance in PCB Design

For the electronics industry, according to industry surveys, the critical flaw of electroless nickel plating is its tendency to discolor (both oxidize or delaminate easily), poor solderability leading to difficulty in welding, and excessively high impedance.

Poor conductivity or unstable performance of the entire board, prone to excessive solder whiskers leading to PCB线路short circuits, resulting in burns or fires.