Flexible circuit board and manufacturing method therefor

A manufacturing method for a high-aspect-ratio flexible circuit board, comprising the following steps:

• providing a plastic substrate, having a first surface and a second surface opposite to each other;
• forming a first patterned groove in the first surface of the plastic substrate and/or forming a second patterned groove in the second surface of the plastic substrate by way of laser, wherein an upper limit of a sum value of a total depth of the first patterned groove and a total depth of the second patterned groove equals a thickness of the plastic substrate minus 5 μm;
• forming a metal seed layer on the first surface and/or the second surface by way of electroless plating or sputtering;
• forming a thin copper layer on the metal seed layer by way of plating;
• and
• forming a copper trace layer on the thin copper layer on the first surface and/or the second surface by way of semi-additive process, the copper trace layer being partially embedded in the plastic substrate, wherein the copper trace layer comprises an exposed trace portion exposed outside the plastic substrate and an embedded trace portion embedded in the plastic substrate, a height of the exposed trace portion is not more than 45 μm, and a width of the exposed trace portion is greater than or equal to a width of the first patterned groove or a width of the second patterned groove;
• and a height/width ratio of the copper trace layer ranges from 1.5 to 3.75.