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What's Impedance Controlled Printed Circuit Board?

作者： 浏览：1816 时间：2015-06-16 11:50:36

In practical application, electronic PCB designers
need to design the **impedance ****controlled**** ****printed circuit board** to reach some special purposes. The are 2 kinds of impedance control PCB, including **single-ened impedance PCB** and **differential pairs impedance PCB**. **Season Multilayer** can make this
kind PCB with min 5ohms +/- 5%, which makes us apart from most **controlled
impedance PCB** manufacturers. Of course, we will make simulation before manufacturing. If need modification, we also will feedback to the customers how to modify and why need to modify so for meeting the impedance requirements.

**What
is Impedance?**

Working under high frequency, impedance is the combination of the capacitance and inductance of a circuit. The value unit in Ohms, which is somewhat different than resistance, a DC characteristic. Impedance is an AC characteristic, that's to say it is related to frequency, but resistance is not.

**What
is Controlled Impedance?**

Unless you have carefully designed the trace and its environment, impedance is typically "uncontrolled", meaning that impedance will vary in value from point to point along the trace, and maybe different from the designed value if the lamination thickness is changed or the finished board thickness is different from the stack-up. So we need to test the impedance value when the impedance pcb are finished manufacturing.

PCB traces at high frequencies perform not the same as the simple connections, controlled impedance helps ensuring that signals are not degraded as they route around a PCB. What important is that controlled impedance is the matching of substrate material properties with trace dimensions and locations to ensure the impedance of a trace's signal is within a certain percentage of a specific value. Controlled impedance boards provide repeatable high frequency performance.

**When
Need to Use Controlled Impedance in PCB board?**

For some special function requirement and a signal must have particular impedance, we should adopt using the controlled impedance. In high frequency applications matching the impedance of PCB traces is important in maintaining data integrity and signal clarity. If the impedance of the PCB trace connecting two components does not match the components' characteristic impedance, there may be increased switching times within the device or the circuit. There may also be random errors.

**What Factors Determine the Controlled Impedance**

The characteristic impedance of a PCB trace is typically determined by its inductive and capacitive, reactance, resistance, and conductance. These factors are a function of the physical dimensions of the trace, the dielectric constant of the PCB substrate material, and dielectric thickness. Typically PCB trace impedance can range from 25 to 125 ohms. The impedance value generated from the PCB structure will be determined by the following factors:

· width and thickness of the copper signal trace (top and bottom)

· thickness of the core or prepreg (PP) material on either side of the copper trace

· dielectric constant of the core and prepreg material

· distance from other copper features

**Controlled Impedance Applications **

Controlled Impedance should be considered for PCBs used in fast digital applications such as:

· Telecommunications

· Computing 100MHz and above

· High Quality Analog Video

· Signal Processing

· RF Communication

**What's Heros PCB's Experience with Controlled Impedance?**

Heros Electronics uses impedance modeling software and impedance testing hardware to meet your controlled impedance requirements. Polar Instrument “SpeedStack” and “CITS” testing. This robust toolset incorporates both a high quality field solver and a comprehensive material library to ensure that you design is executed correctly the first time.

Any Demand of Controlled Impedance PCB, Please Contact Heros Electronics or Click **Here** to Get Quick
Quote.