Patent ID: 9468101
Filing Date: 2016-10-11
CPC Classification: H05K

Claim Text:
1. A microvia structure of a flexible circuit board having a dielectric layer, a first conductive layer, and a second conductive layer, wherein the first conductive layer and the second conductive layer are respectively formed on a first surface and a second surface of the dielectric layer, comprising: a first through hole formed in the first conductive layer which has a bottom surface and defines a first exposed zone on a surface that is opposite to the bottom surface in a circumferential area adjacent to the first through hole; a second through hole formed in the second conductive layer which has a top surface and defines a second exposed zone on the top surface in a circumferential area adjacent to the second through hole, the second through hole corresponding to the first through hole of the first conductive layer and the second through hole having a diameter greater than a diameter of the first through hole; a dielectric layer through hole formed in the dielectric layer, corresponding to the second through hole of the second conductive layer so as to expose the first exposed zone of the first conductive layer; a conductive paste layer filled in the second through hole of the second conductive layer, the dielectric layer through hole of the dielectric layer, and the first through hole of the first conductive layer in such a way that the conductive paste layer covers and electrically contacts the first exposed zone of the first conductive layer, the second exposed zone of the second conductive layer, and a third exposed zone defined on the bottom surface of the first conductive layer about the first through hole; and a first insulation layer set on and covering the bottom surface of the first conductive layer, wherein a lower protective layer is interposed between the bottom surface of the first conductive layer and the first insulation layer.