Abstract:
A laminated substrate includes: a core portion; a first wiring portion configured to be stacked on the core portion and to include a first exposed surface formed by exposing at least part of a surface of the first wiring portion; and a second wiring portion configured to be stacked on the first wiring portion, to include a second exposed surface formed by exposing at least part of a surface of the second wiring portion, and to have higher wiring density of conductor than the first wiring portion has, wherein the first exposed surface and the second exposed surface are provided respectively with a first pad and a second pad which are to be connected to electrodes of one semiconductor chip to be mounted on both the first exposed surface and the second exposed surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2014-218136, filed on Oct. 27, 2014, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments discussed herein are related to, for example, a laminated substrate and a method for manufacturing the laminated substrate. 
       BACKGROUND 
       [0003]    With an increase in speed and capacity of electronic devices, there is increasing demand for high-density packaging technique which achieves high-density connection among logic chips and memory chips. As one of this type of high-density packaging technique, there is known a 2.5-dimensional packaging structure in which a silicon interposer manufactured by a silicon process is mounted on a core substrate, and logic chips and memory chips are planarly mounted on the silicon interposer. In the 2.5-dimensional packaging structure, the memory chip is sometimes mounted on the silicon interposer via a through-silicon via (TSV). International Publication Pamphlet No. WO 2009/141927, Japanese Laid-open Patent Publication No. 11-317582, and Japanese Laid-open Patent Publication No. 2000-165007 may be given as examples of the related art. 
       SUMMARY 
       [0004]    In accordance with an aspect of the embodiments, a laminated substrate includes: a core portion; a first wiring portion configured to be stacked on the core portion and to include a first exposed surface formed by exposing at least part of a surface of the first wiring portion; and a second wiring portion configured to be stacked on the first wiring portion, to include a second exposed surface formed by exposing at least part of a surface of the second wiring portion, and to have higher wiring density of conductor than the first wiring portion has, wherein the first exposed surface and the second exposed surface are provided respectively with a first pad and a second pad which are to be connected to electrodes of one semiconductor chip to be mounted on both the first exposed surface and the second exposed surface. 
         [0005]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0006]    These and/or other aspects and advantages will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawing of which: 
           [0007]      FIG. 1  is a view illustrating a plan view of a semiconductor package in embodiment 1; 
           [0008]      FIG. 2  is a view illustrating a cross-sectional structure of the semiconductor package in embodiment 1; 
           [0009]      FIG. 3  is a view illustrating a core portion, a first wiring portion, and second wiring portions in embodiment 1; 
           [0010]      FIG. 4  is a view illustrating adhesive sheets in embodiment 1; 
           [0011]      FIG. 5  is a view illustrating temporarily bonding of a first adhesive sheet and a second adhesive sheet in embodiment 1; 
           [0012]      FIG. 6  is a view illustrating filling of a conductive paste into through holes of the first adhesive sheet and the second adhesive sheet in embodiment 1; 
           [0013]      FIG. 7  is a view illustrating stacking of the first wiring portion and the second wiring portion in embodiment 1; 
           [0014]      FIG. 8  is a cross-sectional view of a partially-high-density laminated substrate in embodiment 2; and 
           [0015]      FIG. 9  is a cross-sectional view of a partially-high-density laminated substrate in embodiment 3. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0016]    Hereafter, embodiments of this disclosure are described with reference to the drawings. 
       Embodiment 1 
       [0017]      FIG. 1  is a view illustrating a plan view of a semiconductor package  1  in embodiment 1.  FIG. 2  is a view illustrating a cross-sectional structure of the semiconductor package  1  in embodiment 1. The semiconductor package  1  includes a partially-high-density laminated substrate  100 , a logic chip  210 , and multiple memory chips  220 , the logic chip  210 , and the memory chips  220  being mounted on the partially-high-density laminated substrate  100 . In this description, the logic chip  210  and the memory chips  220  are collectively referred to as semiconductor chips. 
         [0018]    In the example depicted in  FIG. 1 , the logic chip  210  is arranged at the center of an upper surface  100   a  of the partially-high-density laminated substrate  100  and the multiple memory chips  220  are arranged to surround the logic chip  210 . 
         [0019]      FIG. 2  schematically depicts a cross section taken along the line A-A′ in  FIG. 1  as viewed in the direction of the arrows. The partially-high-density laminated substrate  100  has a core portion (also referred to as core substrate)  110 , a first wiring portion  120  stacked on the core portion  110 , second wiring portions  130  stacked on the first wiring portion  120 , and the like. 
         [0020]      FIG. 3  is a view illustrating the core portion  110  of the partially-high-density laminated substrate  100  in embodiment 1. The core portion  110  is a printed wiring board having a core board  111  and through hole vias  112  penetrating the core board  111  in a thickness direction. Lands  113  and  114  are formed on an upper surface  110   a  and a lower surface  110   b  of the core portion  110 . The lands  113  formed on the upper surface  110   a  of the core portion  110  and the lands  114  formed on the lower surface  110   b  of the core portion  110  are electrically connected to one another via the through hole vias  112 . For example, a glass epoxy resin substrate may be used as the core board  111  in the core portion  110 . Moreover, the through hole vias  112  are formed by making through holes in the core board  111  by laser processing, drilling, punching, or the like and plating inner surfaces of the through holes with metal. The lands  113  and  114  are formed around the through hole vias  112  on the upper surface  110   a  and the lower surface  110   b  of the core portion  110 , and the lands  113  on the upper surface  110   a  and the lands  114  on the lower surface  110   b  are electrically connected to one another via the through hole vias  112 . 
         [0021]      FIG. 3  is a view illustrating the first wiring portion  120  and the second wiring portions  130  of the partially-high-density laminated substrate  100  in embodiment 1. The first wiring portion  120  and the second wiring portions  130  are each multiple wiring layers fabricated by a publicly-known build-up method. The first wiring portion  120  has the same shape and size as the core portion  110  to cover the entire surface of the core portion  110 , and is formed by stacking multiple wiring layers. Interlayer connection between wiring patterns in the respective wiring layers of the first wiring portion  120  is achieved by vias  126 . 
         [0022]    An upper surface of the first wiring portion  120  includes an exposed upper surface  120   a  located in a center portion of the first wiring portion  120  in a planar direction and covered upper surfaces  120   b  located in end portions of the first wiring portion  120  and covered with the second wiring portions  130  stacked on the covered upper surfaces  120   b . In the center portion of the first wiring portion  120 , that is a region corresponding to the exposed upper surface  120   a , the structure of the wiring layers is a five-layer structure. Meanwhile, in the end portions of the first wiring portion  120 , that is regions corresponding to the covered upper surfaces  120   b , the structure of the wiring layers is a two-layer structure. Recess portions  127  are formed in the end portions of the first wiring portion  120  by setting the number of stacked wiring layers in the end portions of the first wiring portion  120  smaller than that in the center portion of the first wiring portion  120 . The recess portions  127  of the first wiring portion  120  are recess portions which house the second wiring portions  130  as described in detail later. 
         [0023]    Pads  128   a  which are electrodes to be soldered to bumps (electrodes)  211  formed in the logic chip  210  are formed on the exposed upper surface  120   a  of the first wiring portion  120 . Moreover, pads  128   b  which are electrodes for external connection are formed on the covered upper surfaces  120   b  (also corresponding to bottom surfaces of the recess portions  127 ) of the first wiring portion  120 . Furthermore, pads  129  which are electrodes for external connection are formed on a lower surface  120   c  of the first wiring portion  120 . The pads  129  in the first wiring portion  120  are formed at such positions that the pads  129  face (vertically overlap) the lands  113  of the core portion  110  when the first wiring portion  120  is stacked on the core portion  110 . 
         [0024]    Meanwhile, the second wiring portions  130  are each formed by stacking multiple wiring layers, and interlayer connection between wiring patterns in the wiring layers stacked one on top of another is achieved by vias. The second wiring portions  130  are housed (accommodated) in the recess portions  127  formed in the first wiring portion  120 . Pads  136   a  which are electrodes to be soldered to the bumps  211  formed on the bottom surface of the logic chip  210  are formed in regions of upper surfaces  130   a  of the second wiring portions  130  which are close to the exposed upper surface  120   a  of the first wiring portion  120 . Moreover, pads  136   b  which are electrodes to be soldered to bumps  221  formed on bottom surfaces of the memory chips  220  are formed in regions of the upper surfaces  130   a  of the second wiring portions  130  which are outside the regions where the pads  136   a  are arranged. Furthermore, pads  137  which are electrodes for external connection are formed on lower surfaces  130   b  of the second wiring portions  130 . 
         [0025]    In the partially-high-density laminated substrate  100  in embodiment 1, the wiring density of the wiring patterns (conductor) in the wiring layers of the second wiring portions  130  is higher than the wiring density of the wiring patterns (conductor) in the wiring layers of the first wiring portion  120 . In other words, in the second wiring portions  130 , wiring which is finer and higher in density than wiring in the first wiring portion  120  is achieved. For example, in the wiring patterns in the wiring layers of the first wiring portion  120 , line (line width L)/space (distance S between lines) is set to about 15 μm/15 μm. Meanwhile, in the wiring patterns in the wiring layers of the second wiring portions  130 , the line/space (L/S) is set to about 2 μm/2 μm. Note that the aforementioned wiring densities are given as examples. Moreover, in the partially-high-density laminated substrate  100 , the wiring density of the wiring patterns (conductor) in the wiring layers of the first wiring portion  120  is higher than the wiring density of the wiring patterns (conductor) in the wiring layers of the core portion  110 . 
         [0026]    Moreover, pad intervals of the pads  128   a  in the first wiring portion  120  and the pads  136   a  in the second wiring portions  130  are equal to intervals of the bumps  211  in the logic chip  210 . Due to this, the logic chip  210  which is one semiconductor chip may be mounted on both the exposed upper surface  120   a  of the first wiring portion  120  and the upper surfaces  130   a  of the second wiring portions  130 . For example, the pad intervals of the exposed upper surface pads  128   a  and the upper surface pads  136   a  and the intervals of the bumps  211  in the logic chip  210  may be set to about 150 μm. Hereafter, the regions of the upper surfaces  130   a  of the second wiring portions  130  where the pads  136   a  are formed and the exposed upper surface  120   a  of the first wiring portion  120  are collectively referred to as “logic chip mounting region A 1 ”. Moreover, the regions of the upper surfaces  130   a  of the second wiring portions  130  where the pads  136   b  are formed are referred to as “memory chip mounting regions A 2 ”. 
         [0027]    Furthermore, the intervals of the pads  136   b  in the memory chip mounting regions A 2  of the second wiring portions  130  are smaller than the intervals of the pads  128   a  and the pads  136   a  in the logic chip mounting region A 1 , and are equal to the intervals of the bumps  221  of the memory chips  220 . In embodiment 1, the intervals of the pads  136   b  in the memory chip mounting regions A 2  are set to, for example, about 40 μm. In the mounting of the memory chips  220 , the bumps  221  formed on the bottom surfaces of the memory chips  220  are soldered to the pads  136   b  formed in the memory chip mounting regions A 2  of the second wiring portions  130 . The memory chips  220  are thereby mounted face down on the partially-high-density laminated substrate  100  like the logic chip  210 . 
         [0028]    The first wiring portion  120  and the second wiring portions  130  may be fabricated by a publicly-known build-up method. An example of a method of manufacturing the first wiring portion  120  and the second wiring portions  130  is described. A prepreg obtained by impregnating a nonwoven fabric of aramid fiber with an epoxy resin is prepared, and through holes are formed in the prepreg by laser processing or the like. Then, the through holes of the prepreg are filled with a conductive paste, and the prepreg is laminated with copper foil by laminating pressing. A substrate whose both surfaces are covered with the copper foil and which has vias in inner layers are thereby obtained. Next, the surface copper foil is patterned by photo-etching or the like to obtain a double-sided substrate in which wiring patterns are formed. Then, the double-sided substrate is laminated with copper foil and a prepreg having through holes filled with the conductive paste, and thereafter the surface copper foil is patterned. The first wiring portion  120  and the second wiring portions  130  may be fabricated by repeating lamination of the wiring layers a predetermined number of times as described above. 
         [0029]    Hereafter, steps of manufacturing the partially-high-density laminated substrate  100  and the semiconductor package  1  are described. The partially-high-density laminated substrate  100  is manufactured such that, as depicted in  FIG. 3 , the core portion  110 , the first wiring portion  120 , and the second wiring portions  130  are independently fabricated and are bonded to one another by adhesive sheets.  FIG. 4  is a view illustrating the adhesive sheets in embodiment 1. Reference numeral  150  in  FIG. 4  denotes a first adhesive sheet for bonding the first wiring portion  120  to the core portion  110 . Moreover, reference numeral  160  denotes second adhesive sheets for bonding the second wiring portions  130  to the first wiring portion  120 . The first adhesive sheet  150  and the second adhesive sheets  160  are, for example, b-staged glass epoxy prepregs obtained by impregnating glass fiber with an epoxy resin. 
         [0030]    The first adhesive sheet  150  has the same size as the core portion  110  and the first wiring portion  120 , and through holes  151  penetrating the first adhesive sheet  150  in a thickness direction are provided in the first adhesive sheet  150  at predetermined positions. Moreover, the second adhesive sheets  160  have the same size as the recess portions  127  of the first wiring portion  120  and the second wiring portions  130 , and through holes  161  penetrating the second adhesive sheets  160  in a thickness direction are provided in the second adhesive sheets  160  at predetermined positions. The through holes  151  of the first adhesive sheet  150  and the through holes  161  of the second adhesive sheets  160  may be formed by, for example, drilling or the like. The through holes  151  and  161  are filled with a conductive paste (conductive adhesive) when the core portion  110  and the first wiring portion  120  are bonded to each other by the first adhesive sheet  150  and when the first wiring portion  120  and the second wiring portions  130  are bonded to one another by the second adhesive sheets  160 . 
         [0031]      FIG. 5  is a view illustrating temporality bonding of the first adhesive sheet  150  and the second adhesive sheets  160 . In embodiment 1, the first adhesive sheet  150  is aligned with the upper surface  110   a  of the core portion  110  and placed thereon while being preheated. Moreover, the second adhesive sheets  160  are aligned with the recess portions  127  of the first wiring portion  120  and placed thereon while being preheated. The preheating temperature is set to a temperature lower than the curing temperature of the epoxy resin (for example, about 150° C.) and equal to or higher than the softening temperature of the epoxy resin. In embodiment 1, the preheating temperature is set to, for example, about 80° C. The first adhesive sheet  150  and the second adhesive sheets  160  are softened by being preheated. Aligning the first adhesive sheet  150  while softening the first adhesive sheet  150  enables accurate temporarily attachment (temporarily fixation) of the first adhesive sheet  150  to the core portion  110  at a correct position. Moreover, aligning the second adhesive sheets  160  while softening the second adhesive sheets  160  enables accurate temporarily attachment (temporarily fixation) of the second adhesive sheets  160  to the recess portions  127  of the first wiring portion  120  at correct positions. 
         [0032]    In embodiment 1, the positions of the lands  113  of the core portion  110  and the through holes  151  of the first adhesive sheet  150  are associated with one another such that the lands  113  and the through holes  151  are arranged to face one another (vertically overlap one another) in the state where the first adhesive sheet  150  is temporarily attached to the core portion  110 . Moreover, the positions of the pads  128   b  of the first wiring portion  120  and the through holes  161  of the second adhesive sheets  160  are associated with one another such that the pads  128   b  and the through holes  161  are arranged to face one another in the state where the second adhesive sheets  160  are temporarily attached to the first wiring portion  120 . 
         [0033]    Next, as depicted in  FIG. 6 , a conductive paste  170  is filled into the through holes  151  of the first adhesive sheet  150  temporarily attached to the core portion  110 . Moreover, the conductive paste  170  is filled into the through holes  161  of the second adhesive sheets  160  temporarily attached to the first wiring portion  120 . The conductive paste  170  is a mixture of metal particles (conductive filler) and a resin material. For example, particles of copper, gold, silver, palladium, nickel, tin, lead, or the like may be used as the metal particles, or metal particles of two or more types of metal may be used. Moreover, for example, a thermosetting resin such as an epoxy resin is used as the resin material. However, the resin material used in the conductive paste  170  is not limited to the epoxy resin, and other resins such as a polyimide resin may be used. Furthermore, a pressure-contact-type conductive paste or a melt-type conductive paste may be used as the conductive paste  170 . In the pressure-contact-type conductive paste, conductivity is obtained by thermally curing the resin with the metal particles pressed against each other. Moreover, in the melt-type conductive paste, conductivity is obtained by applying heat and pressure to the paste so that the metal particles may be melted to form an alloy. 
         [0034]    Next, as depicted in  FIG. 7 , the first wiring portion  120  is stacked on the core portion  110 , and the second wiring portions  130  are stacked on the first wiring portion  120 . In this stacking step, the first wiring portion  120  is aligned and placed on the core portion  110 , and the second wiring portions  130  are aligned and placed on the first wiring portion  120 . In embodiment 1, the positional relationships of the pads  129  arranged on the lower surface  120   c  of the first wiring portion  120  and the through holes  151  (conductive paste  170 ) of the first adhesive sheet  150  are associated such that the pads  129  are arranged to face the through holes  151 . Moreover, the positional relationships of the pads  137  arranged on the lower surfaces  130   b  of the second wiring portions  130  and the through holes  161  (conductive paste  170 ) of the second adhesive sheets  160  are associated such that the pads  137  are arranged to face the through holes  161 . 
         [0035]    Then, in the stacking step, the first adhesive sheet  150  is interposed between the core portion  110  and the first wiring portion  120 , whereas the second adhesive sheets  160  is interposed between the first wiring portion  120  and the second wiring portions  130 , and in this state, hot pressing is performed in which the stacked portions and sheets are pressed in a stacking direction while being heated. The hot pressing is performed by using, for example, a vacuum pressing device. When the hot pressing using the vacuum pressing device is started, the epoxy resin in the first adhesive sheet  150  and the second adhesive sheets  160  with which the glass fiber is impregnated and the epoxy resin included in the conductive paste  170  is melted. Then, the epoxy resin is heated to the curing temperature range while the softened first adhesive sheet  150  and second adhesive sheets  160  are compressed in the stacking direction by pressing, and the epoxy resin is thereby cured. As a result, as depicted in  FIG. 7 , the core portion  110  and the first wiring portion  120  are bonded to each other via the first adhesive sheet  150 , and the first wiring portion  120  and the second wiring portions  130  are bonded to one another via the second adhesive sheets  160 . The first wiring portion  120  is thus stacked on the core portion  110 , the second wiring portions  130  are stacked on the first wiring portion  120 , and the partially-high-density laminated substrate  100  is completed. 
         [0036]    In the partially-high-density laminated substrate  100 , vias  170 A and  170 B are formed by the conductive paste  170  in which the epoxy resin is cured in the aforementioned stacking step. The vias  170 A are arranged in the first adhesive sheet  150  and achieve electrical interlayer connection between the pads  129  of the first wiring portion  120  and the lands  113  of the core portion  110 . Meanwhile, the vias  170 B are arranged in the second adhesive sheets  160  and achieve electrical interlayer connection between the pads  137  of the second wiring portions  130  and the pads  128   b  of the first wiring portion  120 . 
         [0037]    Then, the logic chip  210  is mounted on the logic chip mounting region A 1  of the partially-high-density laminated substrate  100  fabricated as described above, and the memory chips  220  are mounted on the memory chip mounting regions A 2  of the partially-high-density laminated substrate  100 . As a result, the semiconductor package  1  depicted in  FIG. 2  is completed. Specifically, the logic chip  210  is mounted on the partially-high-density laminated substrate  100  by soldering the bumps  211  of the logic chip  210  to the pads  128   a  of the first wiring portion  120  and the pads  136   a  of the second wiring portions  130 . Moreover, the memory chips  220  are mounted on the partially-high-density laminated substrate  100  by soldering the bumps  221  formed on the bottom surfaces of the memory chips  220  to the pads  136   b  formed in the memory chip mounting regions A 2  of the second wiring portions  130 . 
         [0038]    As depicted in  FIGS. 1 to 7 , in the partially-high-density laminated substrate  100  of embodiment 1, the first wiring portion  120  is stacked on the core portion  110  such that the covered upper surfaces  120   b  are exposed. Then, the second wiring portions  130  whose wiring densities in the wiring layers are higher than that of the first wiring portion  120  are stacked on the first wiring portion  120  such that the upper surfaces  130   a  are exposed. Next, the pads  128   a  and  136   a  are provided on the covered upper surfaces  120   b  of the first wiring portion  120  and the upper surfaces  130   a  of the second wiring portions  130 , and the logic chip  210  is mounted on both the first wiring portion  120  and the second wiring portions  130 . According to this configuration, it is possible to form the second wiring portions  130  in portions where the logic chip  210  and the memory chips  220  are to be connected to one another, that is portions where high-density fine wiring is desirable, and to form the first wiring portion  120  whose wiring density is lower than that of the second wiring portions  130  in other portions. 
         [0039]    As a result, the high-density fine wiring does not have to be formed over the entire substrate, and the area of the second wiring portions  130  may be reduced. Accordingly, a decrease of manufacturing yield and an increase of manufacturing cost may be suppressed. In other words, according to the partially-high-density laminated substrate  100  of embodiment 1, it is possible to suppress the decrease of manufacturing yield and the increase of manufacturing cost in the case where multiple semiconductor chips are connected to one another via fine wiring formed in a substrate. Moreover, since the second wiring portions  130  may be freely arranged in a surface of the partially-high-density laminated substrate  100 , the degree of freedom in design may be increased. In the embodiment, the pads  128   a  formed on the covered upper surfaces  120   b  of the first wiring portion  120  are an example of a first pad. Meanwhile, the pads  136   a  formed on the upper surfaces  130   a  of the second wiring portions  130  are an example of a second pad. 
         [0040]    Moreover, in embodiment 1, the core portion  110 , the first wiring portion  120 , and the second wiring portions  130  are independently fabricated, the core portion  110  and the first wiring portion  120  are connected via the vias  170 A (conductive paste  170 ), and the first wiring portion  120  and the second wiring portions  130  are connected via the vias  170 B (conductive paste  170 ). Independently fabricating the first wiring portion  120  and the second wiring portions  130  which vary in the wiring density of the conductor in the wiring layers as described above may improve the manufacturing yield. Moreover, it is possible to perform a quality check on the independently-fabricated core portion  110 , first wiring portion  120 , and second wiring portions  130  and manufacture the partially-high-density laminated substrate  100  by using only good products. Accordingly, when there is a defect in any of the core portion  110 , the first wiring portion  120 , and the second wiring portions  130 , it is possible to replace the portion with the defect and further improve the manufacturing yield. 
         [0041]    Furthermore, in embodiment 1, the core portion  110 , the first wiring portion  120 , and the second wiring portions  130  are bonded to one another with the first adhesive sheet  150  and the second adhesive sheets  160  being temporarily fixed to the core portion  110  and the first wiring portion  120 . Accordingly, the first wiring portion  120  may be accurately aligned with the core portion  110  and stacked thereon. Moreover, the second wiring portions  130  may be accurately aligned with the first wiring portion  120  and stacked thereon. 
         [0042]    Moreover, in the partially-high-density laminated substrate  100 , the second wiring portions  130  are stacked on the first wiring portion  120  in such a manner that the second wiring portions  130  are housed in the recess portions  127  provided in the first wiring portion  120 . Specifically, the second wiring portions  130  are stacked on the first wiring portion  120  in such a manner that the second wiring portions  130  are embedded (placed) inside the recess portions  127  provided in the first wiring portion  120 . According to this configuration, it is possible to suppress formation of a step between the exposed upper surface  120   a  of the first wiring portion  120  and each of the upper surfaces  130   a  of the second wiring portions  130 . In other words, the logic chip mounting region A 1  in the partially-high-density laminated substrate  100  may be formed to be flat. Accordingly, the mounting of the logic chip  210  may be performed by using a normal chip mounter. Note that, although the second wiring portions  130  are entirely embedded (placed) inside the recess portions  127  provided in the first wiring portion  120  in embodiment 1, the second wiring portions  130  may be partially embedded in the recess portions  127 . 
       Embodiment 2 
       [0043]    Next, a partially-high-density laminated substrate  100 A in embodiment 2 is described.  FIG. 8  is a cross-sectional view of the partially-high-density laminated substrate  100 A in embodiment 2. In this section, differences from the partially-high-density laminated substrate  100  in embodiment 1 are mainly described. 
         [0044]    In the partially-high-density laminated substrate  100 A in embodiment 2, the structure of a core portion  110 A is different from the structure of the core portion  110  in embodiment 1. The core portion  110 A in embodiment 2 is provided with recess portions  115  which house first wiring portions  120 . In embodiment 2, the recess portions  115  are provided in two portions of the core portion  110 A, and the first wiring portions  120  are stacked on the core portion  110 A in such a manner that the first wiring portions  120  is embedded (placed) inside the recess portions  115 . 
         [0045]    Moreover, lands  116  are formed in a center portion of an upper surface  110   a  of the core portion  110 A, and the lands  116  and bumps  211  formed in a bottom portion of a logic chip  210  are soldered to one another. In the partially-high-density laminated substrate  100 A in embodiment 2, the bumps  211  of the logic chip  210  are soldered to the lands  116  of the core portion  110 A, pads  128   a  of the first wiring portions  120 , and pads  136   a  of second wiring portions  130 . As a result, as depicted in  FIG. 8 , the logic chip  210  is mounted on the core portion  110 A, the first wiring portions  120 , and the second wiring portions  130 . The other basic structures of the partially-high-density laminated substrate  100 A are the same as those of the partially-high-density laminated substrate  100  in embodiment 1, and detailed description of the same structures is omitted by denoting the same structures by the same reference numerals. 
       Embodiment 3 
       [0046]    Next, a partially-high-density laminated substrate  100 B in embodiment  3  is described.  FIG. 9  is a cross-sectional view of the partially-high-density laminated substrate  100 B in embodiment  3 . In this section, differences from the partially-high-density laminated substrate  100 A in embodiment 2 are mainly described. The partially-high-density laminated substrate  100 B in embodiment 3 has a core portion  110 A, first wiring portions  120 A, and second wiring portions  130 . The partially-high-density laminated substrate  100 B in embodiment 3 is different from embodiments 1 and 2 in that, as depicted in  FIG. 9 , no recess portions which house the second wiring portions  130  are formed in the first wiring portions  120 A. Moreover, second adhesive sheets  160  are disposed on covered upper surfaces  120   b  of the first wiring portions  120 A such that exposed upper surfaces  120   a  thereof are exposed, and the second wiring portions  130  are bonded to the first wiring portions  120 A via the second adhesive sheets  160 . 
         [0047]    Since no recess portions which house the second wiring portions  130  are formed in the first wiring portions  120 A as described above, a level difference (step) is formed between each of the exposed upper surfaces  120   a  of the first wiring portions  120 A and a corresponding one of the upper surfaces  130   a  of the second wiring portions  130 . In view of this, in embodiment 3, unevenness (level difference) in a logic chip mounting region A 1  of the partially-high-density laminated substrate  100 B is reduced by the height of bumps  211  of a logic chip  210 . In other words, it is possible to reduce the unevenness in the logic chip mounting region A 1  by setting the bump height of the bumps  211  soldered to the pads  128   a  of the first wiring portions  120  higher than that of the bumps  211  soldered to the pads  136   a  of the second wiring portions  130 . Due to this, the logic chip  210  may be preferably mounted even when unevenness is formed in the logic chip mounting region A 1  of the partially-high-density laminated substrate  100 B. 
         [0048]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.