DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Embodiments of the present invention will be described below with reference to the accompanying drawings. It is noted that the same reference symbols in the drawings denote the same or corresponding components.

[0020] Embodiment 1

[0021] The Embodiment 1 of the present invention will be described in detail below referring to the drawings. FIG. 1 is a sectional view of a semiconductor device according to the Embodiment 1 of the present invention. In FIG. 1, 2 is a buildup substrate, 3 is a stiffener, 5 is a second adhesive, 6 is a heat spreader, 7 is a solder ball, 11 is a signal line, 12 is a ground plane, 13 is a core through hole, 14 is a buildup via, 15 is a core insulating layer, 16 is a first core interconnecting layer, 17 is a second core interconnecting layer, 18 is a first buildup insulating layer, 19 is a second buildup insulating layer, 20 is a first buildup interconnecting layer, 21 is a second buildup interconnecting layer, 22 is a first solder resist, 23 is a second solder resist, 25 is the thickness of the first solder resist, 26 is the thickness of the first buildup insulating layer, and 27 is a conductive adhesive layer. Referring to FIGS. 1, 4 , and 5 , a conventional semiconductor device has a ball-grid-array structure (case-type BGA), in which a semiconductor chip 1 (see FIG. 4 ) is installed on a buildup substrate 2 composed of an organic material through a bump 8 as FIG. 1 shows, then the vicinity of the bottom of the semiconductor chip 1 (see FIG. 4 ) is fixed to the central portion of the buildup substrate 2 using an under-fill resin 9 (see FIG. 5 ), the semiconductor chip 1 (see FIG. 4 ) is sealed together with a metal stiffener 3 and a heat spreader 6 with a first adhesive 4 and a second adhesive 5 , and bumps 8 (see FIG. 4 ) and solder balls 7 are attached.

[0022] The buildup substrate 2 comprises core insulating members such as the core insulating layer 15 ; core conductor layers such as the core through hole 13 , the first core interconnecting layer 16 , and the second core interconnecting layer 17 ; buildup insulating layers such as the first buildup insulating layer 18 , (having the thickness 26 ), and the second buildup insulating layer 19 ; buildup conductor layers in which the buildup via 14 , the first buildup interconnecting layer 20 , and the second buildup interconnecting layer 21 are densely formed; solder resists such as the first solder resist 22 (having the thickness 25 ) and the second solder resist; and a solder resist opening. The first solder resist 22 is adhered to the stiffener with the first adhesive 4 and the second adhesive 5 , and the ground plane 12 is mainly formed on the core conductor layer and the pattern of the signal line 11 is mainly formed on the buildup conductor layer.

[0023] This embodiment is characterized in that in place of the first adhesive 4 , a conductive adhesive layer 27 consisting mainly of a conductive adhesive is used as the ground for the signal line 11 . In prior art, on the other hand, since the distance between the signal line 11 and the stiffener 3 , that is the thickness of the first solder resist 22 and the first adhesive 4 (having the thickness 24 ) is larger than the distance between the signal line 11 and the ground plane 12 , that is the thickness of the first buildup insulating layer 18 , the stiffener 3 cannot be used as the ground for the signal line 11 .

[0024] In this embodiment, since the first solder resist 22 (having the thickness 25 ) is thinner than the first buildup insulating layer 18 (having the thickness 26 ), the conductive adhesive layer 27 consisting mainly of an adhesive having an even conductivity is dominant over the ground pattern using the uneven first core interconnecting layer 16 as the ground for the signal line 11 . Although the conductive adhesive layer 27 consisting mainly of a conductive adhesive is in a floating state, the grounding effect is obtained by eddy currents, and the effect of decreasing the variation of the characteristic impedance of the signal line 11 can be obtained. Also, although crosstalk noise tends to increase because the density of the signal line 11 of the first buildup insulating layer 18 is high, the ground approaches to the signal line 11 , and the effect of decreasing the electrical coupling between signal lines 11 , and minimizing crosstalk noise can be obtained.

[0025] Embodiment 2

[0026] The Embodiment 2 of the present invention will be described in detail below referring to the drawings. FIG. 2 is a sectional view of a semiconductor device according to the Embodiment 2 of the present invention, and FIG. 3 is a plan of the semiconductor device of FIG. 2 . The same parts already described in the Embodiment 1 are indicated by the same symbols, and are not doubly described here. In FIG. 2, 28 indicates ground connecting pads. Referring to FIGS. 2 and 3 , this embodiment is characterized in that a plurality of ground connecting pads 28 as shown in FIG. 3 are provided on the first solder resist 22 and the first buildup interconnecting layer 20 , and in having a structure for connecting a conductive adhesive layer 27 consisting mainly of a conductive adhesive described in the Embodiment 1 to a plurality of ground connecting pads 28 .

[0027] As described in the Embodiment 1, the effect of the conductive adhesive layer 27 consisting mainly of a conductive adhesive to be the ground is mainly caused by the eddy current. In this embodiment, a return path of the current can be provided to the conductive adhesive layer 27 consisting mainly of a conductive adhesive by connecting the conductive adhesive layer 27 consisting mainly of a conductive adhesive to a plurality of ground connecting pads 28 . This embodiment has the advantages of reducing the variation of characteristic impedance of the signal lines 11 compared with the Embodiment 1, reducing electrical coupling between the signal lines 11 compared with the Embodiment 1, and reducing crosstalk noise compared with the Embodiment 1. Furthermore, since the number of current paths of the ground increases, the impedance of the ground can be minimized resulting in the reduction of ground bounce.

[0028] It is obvious that the present invention is not limited to the above-described embodiments, and that each of the embodiments can be altered as required within the scope of the technical concept of the present invention. Also, the number, location and shape of the above-described constituting members are not limited to those in the above embodiments, but any number, location and shape suitable for carrying out the present invention can be selected. In the drawings, the same symbols are used for indicating the same constituting members.

[0029] Since the present invention is constituted as described above, the variation of the characteristic impedance can be minimized. The reason is that since the thickness of the first solder resist (first solder-resist thickness) is smaller than the thickness of the first buildup insulating layer (first buildup-insulating-layer thickness), the ground for the signal lines of the adhesive of even conductivity (conductive adhesive layer) is more dominant than the ground pattern using the uneven first core interconnecting layer, and although the adhesive of even conductivity (conductive adhesive layer) is in the floating state, the effect of the ground is obtained by eddy currents. And an electrical coupling between signal lines can be reduced, and crosstalk noise can be minimized The reason is that although the signal lines of the first buildup insulating layer tend to increase crosstalk noise because of high density, it is minimized by arranging the ground close to the signal lines.

[0030] Finally, ground bounce can be minimized. The reason is that since the number of current paths of the ground increase, the inductance of the ground can be decreased.

[0031] In the package for accommodating electronic parts, the package may be constituted so as to fix the conductive adhesive layer at a grounding potential.

[0032] Here, the package for accommodating electronic parts may further comprise pads connected to the grounding plane, the pads being provided on the surface of the buildup substrate and being electrically connected to the conductive adhesive layer.

[0033] Here, the package for accommodating electronic parts may further comprise a plurality of ground connecting pads, the pads being provided on the buildup interconnecting layer, and the conductive adhesive layer having mainly a conductive adhesive.

[0034] In the semiconductor device, the semiconductor device may be so constituted as to fix the conductive adhesive layer in the ball grid array structure at a grounding potential.

[0035] Here, the semiconductor device may further comprise pads connected to the grounding plane in the ball grid array structure, the pads being provided on the surface of the buildup substrate and being electrically connected to the conductive adhesive layer.

[0036] Here, the semiconductor device may further comprise a plurality of ground connecting pads being provided on the buildup interconnecting layer in the ball grid array structure, and the conductive adhesive layer having mainly a conductive adhesive is connected to the plurality of ground connecting pads.

[0037] Here, the method for manufacturing a package for accommodating electronic parts may further comprise the step of fixing the conductive adhesive layer at a grounding potential.

[0038] Here, the method for manufacturing a package for accommodating electronic parts may further comprise the step of providing pads connected to the grounding plane on the surface of the buildup substrate as well as electrically connecting the pads to the conductive adhesive layer.

[0039] Here, the method for manufacturing a package for accommodating electronic parts may further comprise the steps of providing a plurality of ground connecting pads on the buildup interconnecting layer; and connecting the conductive adhesive layer having mainly a conductive adhesive to the plurality of ground connecting pads.

[0040] According to a fourth aspect of the present invention, there is provided a method for manufacturing a package for accommodating electronic parts, comprising the steps of: adhering a buildup substrate having a power source and/or a ground layer formed on a core substrate, and signal lines formed on a buildup interconnecting layer to a stiffener with a conductive adhesive layer using a conductive adhesive, forming a grounding plane using the stiffener and the buildup substrate, installing a semiconductor chip on the buildup substrate through bumps and fixing the vicinity of the bottom of the semiconductor chip on the central portion of the buildup substrate with an under-fill resin; sealing the semiconductor chip with the stiffener and the conductive adhesive layer; and forming a ball grid array structure by fixing solder balls to the bumps.

[0041] The present invention has been described in detail with respect to various embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and it is the invention, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit of the invention.

[0042] The entire disclosure of Japanese Patent Application No. 11-204930 filed on Jul. 19, 1999 including specification, claims, drawings and summary are incorporated herein by reference in its entirety.