Flexible circuit board having rough solder resist layer and manufacturing method thereof

The invention provides a flexible circuit board for carrying a chip. The manufacturing method thereof comprises the following steps: (a) providing a conductive copper layer having a wiring pattern on an insulating substrate; (b) forming a first solder resist layer partially covering the wiring pattern; (c) forming a first tin layer on the conductive copper layer using the first solder resist layer as a mask; (d) forming a second tin layer on the conductive copper layer using the first solder resist layer as a mask; (e) forming a second solder resist layer partially covering the second tin layer and at least partially covering the first solder resist layer; and (f) roughing the second solder resist layer to allow a rough surface formed with the second solder resist layer.