FPC impedance characteristics and impedance control

According to the signal transmission theory, the signal is a function of time and distance variable, so the signal on the attachment of each part are likely to change. So sure the attachment of ac Impedance, namely the ratio of the change of the change of the voltage and current for the Characteristic Impedance of the transmission line (Characteristic Impedance) : the Characteristic Impedance of a transmission line is only associated with the characteristics of signal connection itself. In the actual circuit, wire itself and the distribution of resistance value is less than the system impedance, especially in high frequency circuit, the characteristic impedance mainly depends on attachment of unit distributed capacitance and inductance of distribution impedance. Ideal transmission line characteristic impedance depends only on the attachment distribution of unit distributed capacitance and inductance.

Circuit board in the conductor will have all kinds of signals, when the transmission rate and to raise its must raise its frequency, if the line itself due to factors such as etching, laminated thickness, wire width is different, will cause resistance to change, make the signal distortion. In high-speed circuit board on the conductor, the impedance value should be controlled within a certain range, known as "impedance control". The influencing factors of FPC impedance board walk line impedance mainly have the width of the copper wire, copper wire thickness, the thickness of the dielectric constant and dielectric medium, the thickness of the bonding pad, the path of the ground, line the perimeter of the walk the line. So when designing FPC impedance board must to control board walk line impedance, and to avoid possible signal reflection and other electromagnetic interference and signal integrity problems, can guarantee the stability of the actual use of FPC impedance board.