Photosensitive and via-forming circuit board
A photosensitive and via-forming circuit board comprising a laminate unit, a conductor unit, and a cover layer unit is provided. The laminate unit includes an insulating layer, a first conductive wiring layer and a second conductive wiring layer formed at two opposite sides of the insulating layer, respectively, and at least one through-hole surface defining a through hole extending from the upper surface of the first conductive wiring layer through the insulating layer to the lower surface of the second conductive wiring layer. The conductor unit is formed on the at least one through-hole surface. The cover layer unit is formed from a photosensitive composition comprising an epoxy group-containing compound and a photosensitive polyimide capable of reacting with the epoxy group of the epoxy group-containing compound, and includes a first cover layer formed on the first conductive wiring layer and extending into and filling the through hole.
1. A photosensitive and via-forming circuit board, comprising:
a laminate unit including an insulating layer, a first conductive wiring layer and a second conductive wiring layer formed at two opposite sides of the insulating layer, respectively, and a through-hole surface defining a through hole extending from the upper surface of the first conductive wiring layer through the insulating layer to the lower surface of the second conductive wiring layer;
a conductor unit formed on the through-hole surface and electrically connecting the first conductive wiring layer and the second conductive wiring layer; and
a cover layer unit including a first cover layer and a second cover layer formed on the first conductive wiring layer and the second conductive wiring layer of the laminate unit, respectively, and extending into and together completely filling the through hole, wherein the cover layer unit is formed from a photosensitive composition, and the photosensitive composition comprises an epoxy group-containing compound and a photosensitive polyimide capable of reacting with the epoxy group of the epoxy group-containing compound,
wherein the photosensitive polyimide is a photosensitive polyimide having the structure of formula (I);
R 1 , R 2 and R 3 are each a tetravalent group;
X 1 is a divalent group;
X 2 is a divalent group having a carboxylic acid group;
X 3 is a divalent group having (2-hydroxyl-3-acrylate)propyl group or a divalent group having (2-hydroxyl-3-methacrylate)propyl group;
m is a positive integer from 30 to 70, n is a positive integer from 10 to 45, and o is a positive integer from 10 to 35, based on 100 of the sum of m+n+o;
wherein the plural R 1 s are the same or different, the plural X 1 s are the same or different, the plural R 2 s are the same or different, the plural X 2 s are the same or different, the plural R 3 s are the same or different, and the plural X 3 s are the same or different.
2. The photosensitive and via-forming circuit board of claim 1 , wherein the content of the epoxy group-containing compound ranges from 10 wt % to 70 wt %, based on 100 wt % of the photosensitive polyimide.
3. The photosensitive and via-forming circuit board of claim 1 , wherein the divalent group having the carboxylic acid group is
4. The photosensitive and via-forming circuit board of claim 1 , wherein the divalent group is
wherein p is from 1 to 20,
5. The photosensitive and via-forming circuit board of claim 1 , wherein the epoxy group-containing compound is selected from neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, diglycidyl 1,2-cyclohexanedicarboxylate, bisphenol A diglycidyl ether, 1,2-propanediol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerol propoxylate triglycidyl ether, resorcinol diglycidyl ether, dimer acid diglycidyl ester represented by formula (1), and a combination thereof
6. The photosensitive and via-forming circuit board of claim 1 , wherein the hole diameter of the through hole ranges from greater than 0 mm to 0.25 mm.
7. The photosensitive and via-forming circuit board of claim 1 , wherein the insulating layer is a flexible insulating layer.
8. The photosensitive and via-forming circuit board of claim 1 , wherein the material of the conductor unit is selected from a conductive metal, a conductive polymer, and a combination thereof.