Flexible circuit board

Abstract

The invention discloses a flexible circuit board comprising an upper-layer substrate and a lower-layer substrate; a difference pair including two transmission lines is distributed on the upper-layer substrate; grounding conductive materials are distributed on a part on the lower-layer substrate, which is vertically opposite to a region between the two transmission lines; the difference pair comprises a plurality of subsection groups, each subsection group includes two subsections symmetrically distributed on the two transmission lines, and the line widths of every two adjacent subsections on each transmission line are different, wherein the line widths of the two subsections in each subsection group and the widths of the parts of the grounding conductive materials, respectively corresponding to each subsection group, are determined according to a special characteristic impedance of each subsection group. The flexible circuit board can be used for transmitting high-speed signals and has a same frequency response with a low-pass filter.

Description

technical field [0001] The invention relates to a printed circuit board, in particular to a flexible circuit board. Background technique [0002] Flexible circuit boards are printed circuit boards made of flexible insulating substrates, which have many advantages that rigid printed circuit boards do not have. For example, the thickness of the flexible circuit board is relatively thin, and it can be bent, wound, and folded freely, and can be arranged arbitrarily according to the requirements of the space layout, and can be moved and stretched arbitrarily in the three-dimensional space, so as to achieve the integration of component assembly and wire connection. The use of flexible circuit boards can greatly reduce the size of electronic products, and is suitable for the development of electronic products in the direction of high density, miniaturization, and high reliability. Therefore, flexible circuit boards have been widely used in aerospace, military, mobile communication...

AI Technical Summary

Problems solved by technology

[0003] Because the thickness of the flexible circuit board is extremely thin, the distance between the transmission line on the upper layer circuit board and the ground plane of the lower layer is too close, which makes the flexible circuit board unable to transmit high-speed differential signals. On the flexible circuit board, even if The thinnest transmission line width that can be achieved by general manufacturing processes, such as 4 mils (1 mil = 0.0254 mm), is also difficult to meet the impedance requirements of high-speed signal transmission lines

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