Double-sided flexible circuit board

A double-sided flexible circuit board comprising:

• a flexible substrate including a top surface, a bottom surface, a plurality of through holes and a cutting line, the plurality of through holes are configured to communicate the top and bottom surfaces, an area enclosed by the cutting line is defined as a working area, and an area outside the cutting line is defined as a nonworking area, the flexible substrate is configured to be cut along the cutting line during a cutting process, the working area is configured to be separated from the flexible substrate as an integrated circuit;
• a plurality of through circuit lines each located in one of the plurality of through holes, a first connection end of each of the plurality of through circuit lines is visible on the top surface, and a second connection end of each of the plurality of through circuit lines is visible on the bottom surface;
• a plurality of first circuit lines formed on the top surface and each including a first segment, a bent segment and a second segment, the first segment and the bent segment are located on the working area, the second segment is located both on the working area and the nonworking area, one end of the first segment of each of the plurality of first circuit lines is connected to the first connection end of one of the plurality of through circuit lines, the other end of the first segment of each of the plurality of first circuit lines is connected to one end of the bent segment of one of the plurality of through circuit lines, the other end of the bent segment is connected to one end of the second segment, the other end of the second segment is located on the nonworking area, wherein there is a first distance between the first segment of the two adjacent first circuit lines and a second distance between the second segment of the two adjacent first circuit lines, the second distance is greater than the first distance;
• and
• a plurality of second circuit lines formed on the bottom surface and located on the working area, each of the plurality of second circuit lines is connected to the second connection end of one of the plurality of through circuit lines;
• wherein the first distance is greater than or equal to 18 μm and less than 50 μm, and wherein the second distance is between 22 μm and 50 μm.