Printed circuit board
A chip capacitor 20 is provided in a core substrate 30 of a printed circuit board 10 . This makes it possible to shorten a distance between an IC chip 90 and the chip capacitor 20 and to reduce loop inductance. Since the core substrate 30 id constituted by provided a first resin substrate 30 a , a second resin substrate 30 b and a third resin substrate 30 c in a multilayer manner, the core substrate 30 can obtain sufficient strength.
1. A printed circuit board comprising:
a core substrate comprising a first resin substrate, a second resin substrate and a third resin substrate, the second resin substrate having an opening and positioned between the first resin substrate and the third resin substrate, the core substrate having an upper surface and a lower surface on an opposite side of the upper surface;
a first capacitor formed in the opening of the second resin substrate and having a first electrode having a portion facing to the upper surface of the core substrate and a second electrode having a portion facing to the lower surface of the core substrate;
an upper insulating layer formed over the upper surface of the core substrate and having a conductive circuit layer formed over the upper insulating layer, the upper insulating layer having a via hole electrically connecting the portion of the first electrode of the first capacitor and the conductive circuit layer of the upper insulating layer; and
a lower insulating layer formed over the lower surface of the core substrate and having a conductive circuit layer formed over the lower insulating layer, the lower insulating layer having a via hole electrically connecting the portion of the second electrode of the first capacitor and the conductive circuit layer of the lower insulating layer.
2. A printed circuit board according to claim 1 , wherein the core substrate further comprises a plurality of bonding plates, each of the bonding plates has a core impregnated with a thermosetting resin.
3. A printed circuit board according to claim 1 , wherein each of the first, second and third resin substrates has a core impregnated with a resin.
4. A printed circuit board according to claim 1 , wherein the second resin substrate has a plurality of openings, and a plurality of capacitors are provided in the openings, respectively.
5. A printed circuit board according to claim 1 , further comprising conductor circuits formed on the second resin substrate.
6. A printed circuit board according to claim 1 , further comprising a second capacitor mounted on an outer surface of the printed circuit board.
7. A printed circuit board according to claim 1 , further comprising a plated metal film formed on at least one of the first and second electrodes of the first capacitor.
8. A printed circuit board according to claim 1 , further comprising a coating layer formed on a surface of at least one of the first and second electrodes of the first capacitor, wherein the at least one of the first and second electrodes of the first capacitor has a portion which is exposed from the coating layer, and the potion is electrically connected to a respective one of the via holes.
9. A printed circuit board according to claim 1 , wherein the first capacitor is a chip capacitor, the first electrode is formed inside of an outer edge of the opening.
10. A printed circuit board according to claim 1 , wherein at least one of the first and second electrodes of the first capacitor is formed in a matrix.
11. A printed circuit board according to claim 1 , further comprising an insulating bonding agent coupling the first resin substrate and the first capacitor, the insulating bonding agent being lower in a coefficient of thermal expansion than the first resin substrate.
12. A printed circuit board according to claim 6 , wherein the second capacitor has a capacitance which is equal to or higher than a capacitance of a first capacitor.
13. A printed circuit board according to claim 6 , wherein the second capacitor has an inductance which is equal to or higher than an inductance of the first capacitor.
14. A printed circuit board according to claim 7 , wherein the plated metal film comprises copper.