Impedance is the sum total of the inductance and capacitance of the circuit board at high frequency. The term is used to describe the frequency of the circuit board. Generally, impedance values vary in a printed circuit board, unless the trace values are taken into account while designing. Controlled impedance refers to the value of impedance that remains constant throughout the point along the trace. This factor contributes to high frequency performance. Twisted Traces manufactures and supplies printed circuit boards with controlled impedance.
Our Approach to Controlled Impedance PCBs
Various factors are taken into account while designing controlled impedance PCBs. These include inductance, capacitive resistance, and conductance. We also take the following factors into account, while deciding the controlled impedance of the printed circuit board.
- Width of the Copper Signal Trace: This includes width of the copper trace at the top and bottom. Generally, we provide copper signal traces in the range of 0.5oz: 4/4mil to 6oz/ 15/12mil for its inner layers, with its width varying from 1/3oz – H 0.5oz, and 4/4mil to 6oz: 15/12mil for its outer layers.
- Thickness of the Prepreg Material Used on Both Sides of the Printed Circuit Board: A prepeg is used to hold all cores together in a printed circuit board. While designing an impedance controlled circuit board, the thickness of the prepeg material should be same on the either sides.
- Dielectric Constant of the Core and Prepreg Material: Impedance will vary, if the dielectric constant of the core and prepeg material differs. Hence, we take care to keep both dielectric constants the same.
Applications of Controlled Impedance PCBs
Controlled impedance PCBs are used in various fast digital applications. These include:
- High-quality analog videos
- Signal processing applications
- RF communication