Functional element built-in substrate and wiring substrate

Abstract

An object of the present invention is to propose a functional element built-in substrate which enables an electrode terminal of a functional element to be well connected to the back surface on the side opposite to the electrode terminal of the functional element, and which can be miniaturized. According to the present invention, there is provided a functional element built-in substrate including a functional element provided with an electrode terminal on one surface side of the functional element, and a wiring substrate including a laminated structure in which the functional element is embedded so that the electrode terminal of the functional element faces the front surface side of the structure, and which is formed at least in a side surface region of the functional element by laminating a plurality of wiring insulating layers each including a wiring, the functional element built-in substrate being featured in that the electrode terminal and the back surface side of the wiring substrate are electrically connected to each other through the wiring of the laminated structure, and in that, in a pair of the wiring insulating layers included in the laminated structure and that are in contact with each other, the cross-sectional shape of the wiring in each of the wiring insulating layers, which cross-sectional shape is taken along the plane perpendicular to the extension direction of the wiring in the wiring insulating layer, has a relationship that the cross-sectional area of the wiring in the back surface side wiring insulating layer is larger than the cross-sectional area of the wiring in the front surface side wiring insulating layer.

What is claimed: 
     
         1 . A wiring substrate including,
 an opening section for embedding a functional element, and   a laminated structure which is formed at least in a side surface region of the opening section by laminating a plurality of wiring insulating layers each including a wiring,   wherein the front surface side and the back surface side of the wiring substrate are electrically connected at least through the wiring, and   wherein, in a pair of the wiring insulating layers included in the laminated structure and that are in contact with each other, the cross-sectional shape of the wiring in each of the wiring insulating layers, which cross-sectional shape is taken along the plane perpendicular to the extension direction of the wiring, has a relationship that the cross-sectional area of the wiring in the back surface side wiring insulating layer is larger than the cross-sectional area of the wiring in the front surface side wiring insulating layer.   
     
     
         2 . The wiring substrate according to  claim 1 , wherein, in any pair of the wiring insulating layers included in the laminated structure and that are in contact with each other, the cross-sectional shape of the wiring in each of the wiring insulating layers has a relationship that the cross-sectional area of the wiring in the back surface side wiring insulating layer is larger than the cross-sectional area of the wiring in the front surface side wiring insulating layer. 
     
     
         3 . The wiring substrate according to  claim 1 , wherein the wiring insulating layer includes one layer of the wiring. 
     
     
         4 . The wiring substrate according to  claim 1 , wherein at least one of the plurality of wiring insulating layers includes two or more wiring layers each including a wiring having the equivalent cross-sectional area. 
     
     
         5 . The wiring substrate according to  claim 1 , wherein, in the relationship between a pair of the wiring insulating layers included in the laminated structure and that are in contact with each other, the width of the cross-sectional shape of the back surface side wiring insulating layer is larger than the width of the cross-sectional shape of the front surface side wiring insulating layer. 
     
     
         6 . The wiring substrate according to  claim 1 , wherein, in the relationship between a pair of the wiring insulating layers included in the laminated structure and that are in contact with each other, the height of the cross-sectional shape of the back surface side wiring insulating layer is larger than the height of the cross-sectional shape of the front surface side wiring insulating layer. 
     
     
         7 . The wiring substrate according to  claim 1 , wherein the wiring insulating layer in the laminated structure further includes a via in contact with the wiring. 
     
     
         8 . The wiring substrate according to  claim 7 , wherein, in the relationship between a pair of the wiring insulating layers included in the laminated structure and that are in contact with each other, the horizontal cross-sectional shape of the via in each of the wiring insulating layers is configured such that the cross-sectional area of the via in the back surface side wiring insulating layer is larger than the cross-sectional area of the via in the front surface side wiring insulating layer. 
     
     
         9 . The wiring substrate according to  claim 7 , wherein the via in the laminated structure is configured such that the via diameter on the back surface side of the wiring substrate is larger than the via diameter on the front surface side of the wiring substrate. 
     
     
         10 . The wiring substrate according to  claim 1 , wherein, in the relationship between a pair of the wiring insulating layers included in the laminated structure and that are in contact with each other, the thickness of the back surface side wiring insulating layer is larger than the thickness of the front surface side wiring insulating layer.