Semiconductor device comprising a wiring substrate

Abstract: A copper sheet 6 having an aperture provided therein at a bonding area for clearing the semiconductor chip 4 and its bonding wires 5 is bonded by an adhesive 3 to a sealing side of an organic substrate 1 which has been loaded on the sealing side with a pattern of copper foil wiring 2. The copper sheet 6 is higher in the adhesivity to a sealing resin 7 than any conventional resist. A resultant semiconductor device according to the present invention will prevent detachment of the sealing resin at interface which may result from a thermal history in the sealing or reflow process and eliminate entrance of water hence minimizing declination in the resistance to moisture.

Description: The present invention relates to a semiconductor device and particularly, a structure of a plastic ball grid array package (referred to as P-BGA hereinafter). The structure of a common P-BGA is explained referring to the relevant drawings. WO-A-9740532 (Article 54(3) EPC) shows a substrate-based packaged electronic device compatible with ball grid array manufacture. Fig. 11 is a cross sectional view of the P-BGA and Fig. 12 is an enlarged view showing the region A of Fig. 11. Shown are an organic substrate 1, a copper foil wiring pattern 2, a semiconductor chip 4, bonding wires 5, a sealing resin 7, a resist 8, a grounding layer 9, and solder paste balls 12. For production of the P-BGA structure, general steps are coating the organic substrate 1 made of e.g. bismaleic triazine resin and equipped with the copper foil wiring pattern 2 having a thickness of 10 to 40 micrometers with the resist 8 for protecting most regions of the wiring pattern 2 where no bonding wires are connected, placing the semiconductor chip 4 by a conductive paste on the substrate 1, connecting electrodes of the semiconductor chip 4 by the bonding wires 5 to the wiring pattern 2 on the organic substrate 1, sealing with the sealing resin 7 one side of the substrate 1 where the semiconductor chip 4 is mounted, and applying a grid form of balls 12 on the other side of the substrate 1. The conventional P-BGA however allows the resist 8, which contains a silicon component unfavorable for adhesivity to the sealing resin 7, to cover most regions of the organic substrate 1 to be sealed with the sealing resin 7. The sealing resin 7 of a particular type may cause the resist 8 to release its silicon component as triggered by a thermal history in the sealing or reflow process during the mounting to a mother board and subsequently detach at interface from the sealing resin 7, thus declining the resistance to moisture. The present invention seeks to ameliorate this problem. According to the present invention, there is provided a semiconductor device comprising an organic substrate, a wiring pattern on one side of the organic substrate, the wiring pattern including an area for bonding thereto bonding wires, a copper sheet on the one side of the organic substrate, copper sheet having an aperture configured to allow the bonding wires to be connected to the bonding,area, a semiconductor chip mounted on the one side of the organic substrate or supported on the copper sheet and having bonding wires for connecting it to the wiring pattern and a sealing resin covering the semiconductor chip and the aperture, the sealing resin overlapping onto the copper sheet at least around the edge of the aperture. This can have the advantage of helping to prevent the sealing resin detaching from the underlying sheet during a sealing or re-flow process. This helps to eliminate the entrance of water and minimise deterioration in moisture resistance. The semiconductor device may also comprise an adhesive layer for bonding the copper sheet on the substrate. The wiring pattern may be insulated from the copper sheet by an adhesive layer. The semiconductor device may also comprise a die pad and the semiconductor chip may be mounted on the die pad. The semiconductor may also comprise another adhesive layer for bonding the semiconductor chip to the die pad. The die pad may be integrally formed with the copper sheet. This can have the advantage of conducting heat away from the semiconductor chip thereby allowing semiconductor chips with higher power consumption to be used. The copper sheet may be electrically connected to a grounding layer provided within the organic substrate through holes therein. This can have the advantage of providing a strip line structure, helping to decrease the inductance of signal lines, and minimise crosstalk. The copper sheet may be provided with a connection terminal for grounding, the connection terminals being of a spot shape and arranged around the aperture. The copper sheet may have peripheral extensions thereof mechanically folded downward and towards an opposing side of the organic substrate so as to cover a side edge of the organic substrate. The copper sheet may be electrically connected by through holes to a grounding layer provided within the organic substrate. The folded peripheral extensions of the copper sheet may be provided with connection terminals. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a cross sectional view of a P-BGA according to a first embodiment of the present invention; Fig. 2 is an enlarged view showing the region B of Fig.1; Fig. 3 is a plan view of the P-BGA of the first embodiment viewed from the substrate sealing side; Fig. 4 is a cross sectional view of a P-BGA according to a second embodiment of the present invention; Fig. 5 is a plan view of the P-BGA of the second embodiment viewed from the substrate sealing side; Fig. 6 is a cross sectional view of a P-BGA according to a third embodiment of the present invention; Fig. 7 is a plan view of the P-BGA of the third embodiment viewed from the substrate sealing side; Fig. 8 is a cross sectional view of a P-BGA according to a fourth embodiment of the present invention; Fig. 9 is a cross sectional view of a P-BGA according to a fifth embodiment of the present invention; Fig. 10 is an explanatory view showing the advantage of the P-BGA of the fifth embodiment; Fig. 11 is a cross sectional view of a conventional P-BGA; and Fig. 12 is an enlarged view showing the region A of Fig. 11. In the following, components which are substantially identical in both construction and function to each other are denoted by like numerals. Fig. 1 is a cross sectional view of a P-BGA (taken along the line A-A of Fig. 3) showing a first embodiment of the present invention. Fig. 2 is an enlarged view of the region B of Fig. 1. Fig. 3 is a plan view of the P-BGA of the first embodiment viewed from the substrate sealing side. As shown, the P-BGA is produced by applying a copper foil wiring pattern 2 on one side of an organic substrate 1 and bonding a copper sheet of 0.1 to 0.4 mm thick, which has an aperture 6A for clearing a semiconductor chip 4 and bonding wires 5, by an adhesive 3 to the sealing side of the organic substrate 1. The semiconductor chip 4 is bonded by an adhesive 4B to a die pad 4A located in a predetermined region of the organic substrate 1. The sealing side of the organic substrate 1 of the P-BGA is covered with the copper sheet 6 which is higher in the adhesivity to the sealing resin 7 than a common resist, whereby detachment of the sealing resin 7 after the reflow process will be prevented and declination in the resistance to moisture will be minimized. According to the first embodiment, the copper sheet 6 bonded on the sealing side of the organic substrate 1 is favorable for adhesion to the sealing resin 7 as compared with the common resist 8. This prevents the detachment of the sealing resin 7 which may result from the thermal history in the seating or reflow process and will permit no entrance of water hence minimizing declination in the resistance to moisture. In addition, the copper sheet 6 (of a conductive material) is located over the signal lines of the pattern thus attenuating the inductance of signals. A second embodiment of the present invention will now be described. Fig. 4 is a cross sectional view of a P-BGA (taken along the line B-B of Fig. 5) showing the second embodiment. Fig. 5 is a plan view of the P-BGA of the second embodiment viewed from the substrate sealing side. The second embodiment is distinguished from the first embodiment in which the copper sheet 6 bonded to the sealing side of the substrate 1 has the aperture 6A therein for providing a bonding area of the semiconductor chip 4 and its bonding wires 5 by the fact that apertures are made for clearing only the bonding wires 5 while a die pad 6B on which the semiconductor chip 4 is mounted is formed integral with the copper sheet 6. Since the copper sheet 6 having the die pad 6B formed integrally thereon for supporting the semiconductor chip 4 is bonded on the sealing side of the organic substrate 1 of the P-BGA, its high adhesivity to the sealing resin 7 prevents detachment from the sealing resin 7 after the sealing or reflow process and will minimize declination in the resistance to moisture. Also, the copper sheet 6 formed integral with the die pad 6B on which the semiconductor chip 4 is mounted has heat radiator passages 6C thereon for releasing heat generated by the semiconductor chip 4 hence decreasing the thermal resistance. According to the second embodiment, the copper sheet 6 bonded on the sealing side of the organic substrate 1 is favorable for adhesion to the sealing resin 7 as compared with the common resist. This prevents the detachment of the sealing resin 7 which may result from the thermal history in the seating or reflow process and will permit no entrance of water hence minimizing declination in the resistance to moisture. In addition, as the copper sheet 6 has the die pad 6B formed integrally thereon for supporting the semiconductor chip 4, the heat generated by the semiconductor chip 4 can be dissipated along the die pad 6B and the heat radiator passages 6C to the copper sheet 6 hence improving the efficiency of heat radiation and allowing a high power consumption type of the semiconductor chip 4 to be employed. Meanwhile, denoted by 2A are bonding terminals. A third embodiment of the present invention will be described. Fig. 6 is a cross sectional view of a P-BGA (taken along the line C-C of Fig. 7) showing the third embodiment. Fig. 7 is a plan view of the P-BGA of the third embodiment viewed from the substrate sealing side. As shown, the copper sheet 6 of 0.1 to 0.4 mm thick is bonded by an adhesive 3 to the sealing side of the organic substrate 1 after a pattern of signal lines 10 made from copper foil are placed on the sealing side of the organic substrate 1. Also, the copper sheet 6 is electrically connected by through holes 11 to a grounding layer 9 provided within the organic substrate 1. The sealing side of the organic substrate 1 of the P-BGA is covered with the copper sheet 6 which is higher in the adhesivity to the sealing resin 7 than a common resist 8, whereby detachment of the sealing resin 7 after the reflow process will be prevented and declination in the resistance to moisture will be minimized. Since the copper sheet 6 is electrically connected by the through holes 11 to the grounding layer 9 provided within the organic substrate 1, the signal lines 10 between the copper sheet 6 and the grounding layer 9 are subjected to a grounding potential hence enhancing the electrical characteristics. Referring to Fig. 6, denoted by 10A are bonding terminals. According to the third embodiment, the copper sheet 6 bonded on the sealing side of the organic substrate 1 is favorable for adhesion to the sealing resin 7 as compared with the common resist 8. This prevents the detachment of the sealing resin 7 which may result from the thermal history in the seating or reflow process and will permit no entrance of water hence minimizing declination in the resistance to moisture. The copper sheet 6 electrically connected by the through holes 11 to the grounding layer 9 provided within the organic substrate 1 allows the signal lines 10 between the copper sheet 6 and the grounding layer 9 to be subjected to a grounding potential (in a strip-line structure). As the result, the signal lines 10 will be decreased in the inductance, simplified for having a desired combination of characteristic impedance, and minimized in the generation of crosstalk inbetween because of the sealing effect of the grounding potential. A fourth embodiment of the present invention will be described. Fig. 8 is a cross sectional view of a P-BGA showing the fourth embodiment of the present invention. In this embodiment, the copper sheet 6 of 0.1 to 0.4 mm thick is bonded by an adhesive 3 to the sealing side of the organic substrate 1 after a pattern of copper foil wiring 2 is placed on the sealing side of the organic substrate 1. Then, the copper sheet 6 is folded at four side ends downwardly and towards the rear side of the organic substrate 1 so as to cover the side edge of the organic substrate 1. Also, the copper sheet 6 is electrically connected by through holes 11 to a grounding layer 9 provided within the organic substrate 1. Four folded ends of the copper sheet 6 at the edge of the rear side of the organic substrate 1 are plated with nickel/gold alloy and then loaded with solder paste balls 12A. According to the fourth embodiment, the copper sheet 6 bonded on the sealing side of the organic substrate 1 of the P-BGA is favorable for adhesion to the sealing resin 7 as compared with the common resist 8. This prevents the detachment of the sealing resin 7 which may result from the thermal history in the seating or reflow process and will permit no entrance of water hence minimizing declination in the resistance to moisture. The side edge of the organic substrate 1 is also covered with the copper sheet 6 and thus prevents entrance of water from side directions increasing the resistance to moisture. Also, the solder paste balls 12A are mounted on the folded ends of the copper sheet 6 which is electrically connected by the through holes 11 to the grounding layer 9 provided within the organic substrate 1 hence minimizing the number of grounding terminals at the ball mounting area as compared with the conventional semiconductor device. This permits installation of a more number of I/O terminals, whereby the use of terminals per package can be optimized. A fifth embodiment of the present invention will now be described. Fig. 9 is a cross sectional view of a P-BGA showing the fifth embodiment of the present invention and Fig. 10 is an explanatory view of the advantage on the P-BGA. In this embodiment, the copper sheet 6 bonded to the organic substrate as described in the third or fourth embodiment is plated with a nickel/gold alloy 16 at specific spots about the apertures (0.5 to 1.0 mm from the edge). The plated spots 16 serve as grounding ports and are connected by bonding wires 5 to the grounding terminals of the semiconductor chip 4. In a high-speed device, signal bonding wires 5s extend to signal bonding terminals 15 which are located outside the source bonding terminals 14 and the grounding terminals 13 (in an annular arrangement about a die pad) and will thus be increased in length, as shown in Fig. 10(a). Referring to Fig. 10(b), the fifth embodiment allows the nickel/gold plated spots 16 to be formed on the copper sheet 6 on the organic substrate 1 and serve as the grounding terminals so that source bonding terminals 14 and signal bonding terminals 15 are located inwardly. As the result, bonding wires 5s extending from the signal bonding terminals 15 will be reduced in length. According to the fifth embodiment, in addition to the advantages of the third and fourth embodiments, the signal bonding terminals 15 are located more inside as compared with any conventional semiconductor device and thus the bonding wires are minimized in the length, whereby the signal lines will be suppressed in the inductance and reduced in the generation of noise. Although the preferred embodiments of the present invention have been described in the form of a semiconductor device, they are not of limitations. It would be understood by those skilled in the art that various changes and modifications may be made. As set forth above, the present invention offers the following advantages. According to the first feature of the present invention, the copper sheet bonded to the sealing side of the organic substrate is higher in the adhesivity to the sealing resin than any conventional resist. This prevents detachment of the sealing resin at interface which may result from the thermal history in the sealing or reflow process and eliminates entrance of water thus minimizing declination in the resistance to moisture. According to the second feature of the present invention, the copper sheet on the organic substrate is formed integral with the die pad on which a semiconductor chip is mounted allowing heat generated by the semiconductor chip to dissipate at higher efficiency. As the efficiency of heat radiation is increased, a higher power consumption type of the semiconductor chip can be mounted. According to the third feature of the present invention, the copper sheet on the organic substrate is electrically connected by the through holes to the grounding layer provided within the organic substrate hence constituting a strip line structure in which the signal lines between the copper sheet and the grounding layer are subjected to a grounding potential. As the result, the signal lines will be decreased in the inductance, simplified for having a desired combination of characteristic impedance, and minimized in the generation of crosstalk inbetween because of the sealing effect of the grounding potential. According to the fourth feature of the present invention, the side edge of the organic substrate is covered with the copper sheet and thus prevents entrance of water from side directions increasing the resistance to moisture. In addition, the solder paste balls are mounted on the folded ends of the copper sheet which is electrically connected by the through holes to the grounding layer in the organic substrate hence minimizing the number of grinding terminals at the ball mounting area as compared with the conventional semiconductor device. This permits installation of a more number of I/O terminals, whereby the use of terminals per package can be optimized. According to the fifth embodiment of the present invention, the grounding terminals are formed on the folded ends of the copper sheet bonded to the organic substrate so that the signal bonding terminals are located inwardly, whereby the bonding wires will be reduced in the length. As the result, the signal lines will successfully be suppressed in the inductance and reduced in the generation of noise.

Claims: A semiconductor device comprising: an organic substrate (1); a wiring pattern (2) on one side of said the organic substrate, the wiring pattern including an area (2A) for bonding thereto bonding wires (5); a copper sheet (6) overlying the wiring pattern and having an aperture (6A) configured to allow the bonding wires to be connected to the bonding area; a semiconductor chip (4) mounted on the one side of the organic substrate or supported on the copper sheet and having bonding wires for connecting it to the wiring pattern; and a sealing resin (7) covering the semiconductor chip and the aperture, the sealing resin overlapping onto the copper sheet at least around the edge of the aperture. A semiconductor device according to claim 1, comprising an adhesive layer (3) for bonding the copper sheet (6) to the substrate (1). A semiconductor device according to claim 2, wherein the wiring pattern (2) is insulated from the copper sheet (6) by the adhesive layer (2). A semiconductor device according to any preceding claim, comprising a die pad (4A; 6B), said semiconductor chip (4) being mounted on said die pad. A semiconductor device according to claim 4, comprising another adhesive layer (4B) for bonding the semiconductor chip to the die pad (4A). A semiconductor device according to claim 4, wherein the die pad (6B) is integrally formed with said copper sheet (6). A semiconductor device according to any preceding claim, wherein the copper sheet (6) is electrically connected to a grounding layer (9) provided within the organic substrate (1) through holes therein. A semiconductor device according to claim 7, wherein the copper sheet (6) is provided with connection terminals (16) for grounding, said connection terminals being of a spot shape and arranged about the aperture. A semiconductor device according to claim 1 or 2, wherein the copper sheet (6) has peripheral extensions thereof mechanically folded downwardly and towards an opposing side of the organic substrate (1) so as to cover a side edge of the organic substrate. A semiconductor device according to claim 9, wherein the copper sheet (6) is electrically connected by through holes to a grounding layer provided within the organic substrate. A semiconductor device according to claim 10, wherein the folded peripheral extensions of the copper sheet are provided with connection terminals.

Inventors: TERUI MAKOTO, TERUI, MAKOTO
Applicants: OKI ELECTRIC IND CO LTD, OKI ELECTRIC INDUSTRY CO., LTD.
Application year: 1997
Main classification: H01L23
IPC codes: H01L21, H01L23