Circuit board

Abstract

A circuit board includes an inner circuit substrate and an outer circuit substrate electrically connected to the inner circuit substrate. The outer circuit substrate includes an outer dielectric layer and an outer circuit layer facing the inner circuit substrate embedded in the outer dielectric layer. A portion of the outer circuit layer facing away from the inner circuit substrate protruding from the outer dielectric layer. The circuit board can increase contact area between the outer circuit layer and the outer dielectric layer, improving adhesion between the outer circuit layer and the outer dielectric layer, and reducing a thickness of the outer circuit substrate, thereby reducing the overall thickness of the circuit board.

What is claimed is: 
     
         1 . A circuit board, comprising:
 an inner circuit substrate; and   an outer circuit substrate electrically connected to the inner circuit substrate, and the outer circuit substrate comprising:
 an outer dielectric layer; and 
 an outer circuit layer facing the inner circuit substrate embedded in the outer dielectric layer, a portion of the outer circuit layer facing away from the inner circuit substrate protruding from the outer dielectric layer. 
   
     
     
         2 . The circuit board of  claim 1 , further comprising a solder mask, wherein the solder mask is disposed on the outer circuit substrate away from the inner circuit substrate; the solder mask comprises an opening, the outer circuit layer comprises a solder pad exposed from the opening. 
     
     
         3 . The circuit board of  claim 2 , wherein a surface of the solder pad exposed from the opening is not on a same plane. 
     
     
         4 . The circuit board of  claim 3 , wherein the surface of the solder pad is step-shaped or have grooves at various depths. 
     
     
         5 . The circuit board of  claim 1 , wherein the inner circuit substrate comprises an inner dielectric layer and a first conductive pillar, and the first conductive pillar penetrates the inner dielectric layer; the outer circuit substrate further comprises a second conductive pillar electrically connected to the outer circuit layer; the second conductive pillar is connected to the first conductive pillar.