Method of fabricating semiconductor package

[0002] 1. Field of the Invention

[0003] The present invention relates to a method of fabricating a semiconductor package and, more particularly, to a method of fabricating a semiconductor package, which forms the semiconductor package as large as a semiconductor chip to reduce its size and make it compact, and attaches all kinds of semiconductor chips, such as a type in which a bond pad is located at the edge of the surface of semiconductor chip or a type in which the bond pad is formed at the center of the surface of semiconductor chip, in an area array form, to form the input/output ports of the semiconductor package, realizing a high-integration and high-performance semiconductor package.

[0004] 2. Discussion of Related Art

[0005] In general, semiconductor packages include a resin sealed package, TCP package, glass sealed package and metal sealed package. These semiconductor packages are divided into an insertion type and surface mount technology (SMT) type according to the packaging method. A typical insertion type includes a dual in-line package (DIP) and pin grid array (PGA), and typical SMT type includes a quad flat package (QFP), plastic leaded chip carrier (PLCC), ceramic leaded chip carrier (CLCC) and ball grid array (BGA). As electronic products become compact, the SMT-type semiconductor package rather than the insertion type is being widely used in order to increase the packing density of components of a print circuit board.

[0006] Conventional QFP and BGA are explained below with reference to FIGS. 1 and 2. FIG. 1 shows a structure of a conventional QFP, constructed of a semiconductor chip 1 in which electronic circuits are integrated, a mounting board 8ato which semiconductor chip 1 is attached by an epoxy 3, a plurality of leads 8 externally transmitting a signal of semiconductor chip 1, a wire 4 connecting semiconductor chip 1 to leads 8, and sealant 5 covering semiconductor chip 1 and other peripheral components to protect them from external oxidation and corrosion. With this QFP, a signal output from semiconductor chip 1 is transmitted to leads 8 through wire 4, to be sent to a peripheral circuit through a mother board connected to leads 8. A signal generated by the peripheral circuit is transmitted to semiconductor chip 1 through a path opposite to the above one. However, as the performance of the semiconductor chip is improved, the number of pins of the QFP increases but the distance between the pins is technically difficult to reduce below a specific size. Thus, allowing the QFP to hold a lot of pins enlarges the package.

[0007] To overcome this problem, the BGA package has been proposed, which employs a solder ball fused on one side of semiconductor package as its input/output means. Accordingly, the BGA package can process input/output signals larger than those processed by the QFP and it is fabricated smaller than the QFP. Referring to FIG. 2, the BGA is constructed of a circuit board 2 on which a circuit pattern 2ais formed and a solder mask 2bis coated to protect circuit pattern 2a, a semiconductor chip 1 which includes electronic circuits integrated therein and is attached to the center of the surface of circuit board 2, a wire 4 connecting semiconductor chip 1 to circuit pattern 2aof circuit board 2, to transmit signals, a solder ball 6 fused on circuit pattern 2aof circuit board 2 to externally transmit signals, and a sealant 5 covering semiconductor chip 1 and other peripheral components to protect them from external oxidation and corrosion.

[0008] With the BGA constructed as above, a signal output from semiconductor chip 1 is transmitted to circuit pattern 2athrough wire 4, and then sent to a mother board through solder ball 6 fused to circuit pattern 2a, to be supplied to a peripheral circuit. A signal generated by the peripheral circuit is transmitted to semiconductor chip 1 through a path opposite to the above one. However, because the BGA package is larger than the semiconductor chip included therein by several times, there is a limit to reduce the size of electronic products employing the package. Furthermore, the circuit board of the BGA package is expensive, increasing the cost of the products. Moreover, moisture may permeate the package through the circuit board, creating cracks.

[0009] Accordingly, the present invention is directed to a method of fabricating a semiconductor package that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.

[0010] An object of the present invention is to provide a method of fabricating a semiconductor package, which realizes a small-size semiconductor package without performance deterioration, to meet a tendency to miniaturization of electronic products in which semiconductor packages are mounted, such as communication apparatus and computer, provides a new type of compact multi-pin semiconductor package as large as a semiconductor chip mounted thereon, and accomplishes a semiconductor package having multi-function to minimize its mounting area on an electronic product, resulting in minimizing of the products.

[0011] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

[0012] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention:

[0013] In the drawings:

[0014] FIGS. 1 and 2 are cross-sectional views showing structures of conventional semiconductor package and BGA package;

[0015] FIGS. 3A to 3G are cross-sectional views showing a method of fabricating a semiconductor package according to the present invention;

[0016] FIG. 4 is a plan view of a circuit board sheet according to an embodiment of the present invention;

[0017] FIG. 5 is a plan view of a circuit board sheet according to another embodiment of the present invention;

[0018] FIG. 6 is a cross-sectional view showing a semiconductor package structure according to an embodiment of the present invention; and

[0019] FIG. 7 is a cross-sectional view showing a semiconductor package structure according to another embodiment of the present invention.

[0020] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

[0021] A method of fabricating a semiconductor package according to the present invention, comprises the steps of (a) providing a circuit board sheet 20 constructed in such a manner that a nonconductive material 22 is coated on at least one side of a copper sheet 21, opposite to a side on which a semiconductor chip is mounted, a plurality of repetitive same circuit patterns 23 having a plurality of bond fingers 26 and solder ball lands 25 are formed on nonconductive material 22, at least one rectangular opening 27 is formed in each of circuit patterns 23, and a solder mask 24 covers circuit patterns 23 to protect them, externally exposing bond fingers 26 and solder ball lands 25, bond fingers 26 being arranged on the surfaces of portions of circuit board sheet 20, which lie adjacent to the longer sides of rectangular opening 27; (b) attaching semiconductor chip 10 using adhesive means 30, to expose a bond pad 11 of semiconductor chip 10 through opening 27 formed in each of the plurality of repetitive circuit patterns 23 formed on circuit board sheet 20; (c) electrically connecting bond pad 11 of semiconductor chip 10 to circuit patterns 23 of circuit board sheet 20 with a wire 40; (d) dispensing a sealant 50 and hardening it, to protect bond fingers 26, wire 40 and bond pad 11 of semiconductor chip 10 from external environments; (e) fusing solder balls 60 on solder ball lands 25 formed on circuit board sheet 20 as input/output ports; and (f) cutting circuit board sheet 20 in the same size as that of semiconductor chip 10, dividing it into chip size packages.

[0022] Circuit board sheet 20 is fabricated in such a manner that prepreg 22 of a nonconductive material is located on both sides of copper sheet 21, thin copper foil 23ais laminated on prepreg 22 placed on a side where circuit patterns 23 to be formed, circuit pattern 23 is formed in copper foil 23athrough exposure and development processes using a dry film for photoresist and a photomask having a circuit pattern thereon, and solder mask 24 is coated to protect circuit pattern 23. Circuit board sheet 20 includes an opening 27 for opening a region where bond pad 11 of semiconductor chip 10 is located.

[0023] FIGS. 3A to 3G are cross-sectional views illustrating a method of fabricating a semiconductor package according to the present invention. Referring to FIG. 3A showing raw materials for fabricating circuit board sheet 20, prepreg 22 is located on both sides of copper sheet 21, and thin copper foil 23ais laminated on prepreg 22 placed on a side where circuit pattern 23 to be formed. Copper sheet 21 is formed of copper which easily emits heat. FIG. 3B shows the lamination of copper 21, prepreg 22 and copper foil 23a. The lamination uses a lamination press which is able to increase temperature above than 150° C. FIG. 3C shows that circuit pattern 23 is formed in laminated copper foil 23ato fabricate circuit board sheet 20. Referring to FIG. 3C, circuit pattern 23 is formed in such a manner that the dry film for photoresist is attached on copper foil 23a, and exposure and development processes are carried out using the photomask having a circuit pattern thereon, to form a desired circuit pattern. Then, solder mask 24 is coated thereon to protect circuit patterns 23.

[0024] Circuit pattern 23 consists of the same patterns repeated in vertical and horizontal directions. Opening 27 is formed in a region where bond pad 11 of semiconductor chip 10 is located. Portions of solder mask 24, through which solder ball 60 will be fused on circuit pattern 23 and bond pad 11 of semiconductor chip 10 will be connected to circuit pattern 23 with wire 40, are opened to form solder ball lands 25 and bond fingers 26. Solder ball lands 25 are arranged in an array form. Portions of circuit pattern 23, exposed through solder ball lands 25 and bond fingers 26, are plated with nickel or gold, to improve bonding strength in case of fusing of solder ball 60 or connection of wire 40.

[0025] FIG. 3D shows the coating of adhesive means 30 on a side of circuit board sheet 20, opposite to the one on which circuit pattern 23 is formed. Adhesive means 30 are formed in a manner that an epoxy adhesive or adhesive film is coated using a screen printer or dispenser. FIG. 3E shows the adhesion of semiconductor chip 10 on circuit board sheet 20. Referring to FIG. 3E, semiconductor chip 10 is adhered to circuit board sheet 20 on which adhesive means 30, and the epoxy adhesive or adhesive film forming adhesive means 30 is hardened at a high temperature of above 100° C. Here, bond pad 11 of semiconductor chip 10 is exposed through opening 27 of circuit board sheet 20, and each semiconductor chip 10 is attached to each of the same circuit patterns 23 repeated in vertical and horizontal directions. Furthermore, only semiconductor chip 10 judged as a good one by a test which is carried out to semiconductor chips in wafer state is selectively attached to circuit board sheet 20, preventing a poor semiconductor package.

[0026] FIG. 3F shows that circuit pattern 23 of circuit board sheet 20 is connected to bond pad 11 of semiconductor chip 10 through wire 40, a sealant 50 covers them, and solder ball 60 is fused on circuit pattern 23. Bond pad 11 of semiconductor chip 10, externally exposed through opening 27 of circuit board sheet 20, and bond finger 26 of circuit pattern 23 are connected with wire 40 using a wire bonder. In this state, a coating liquid, such as epoxy and polyimide, or epoxy type encapsulation material is coated on wire 40 and semiconductor chip 10, and then hardened, to form sealing portion 50, protecting the surfaces of wire 40 and semiconductor chip 10. Then, solder ball 60 is fused on solder ball land 25.

[0027] Sealant 50 sealing opening 27 is hardened at an oven or furnace at approximately 150° C. (the fusing point is about 175° C.). To form solder ball 60, first of all, a flux is coated on solder ball land 25, and solder ball 60 is mounted thereon. Thereafter, solder ball 60 undergoes reflow process using an oven or furnace at a high temperature of above 150° C., to be fused on solder ball land 25. After this, a cleaning process is performed to remove unnecessary remnant of the flux. Referring to FIG. 3G showing a step of cutting circuit board sheet 20, circuit board sheet 20 is cut using a sawing apparatus 70, laser or wire cutting apparatus, to divide the same circuit patterns 23 repeated in vertical and horizontal directions into each piece, obtaining the package having the same size as that of semiconductor chip 10.

[0028] FIG. 4 is a plan view showing circuit board sheet 20 in which opening 27 is formed for bond pad 11 formed on semiconductor chip 10 to use a semiconductor chip arranged at the center of the upper surface of semiconductor chip 10. FIG. 5 is a plan view showing circuit board sheet 20 in which opening 27 is formed for bond pad 11 formed on semiconductor chip 10 to use a semiconductor chip arranged at the edge of the upper surface of semiconductor chip 10. FIGS. 6 and 7 are cross-sectional views of the semiconductor package fabricated by the method of the present invention. Referring to FIGS. 6 and 7, the semiconductor package includes: semiconductor chip 10 having electronic circuits integrated thereon, on which bond pad 11 externally transmitting signals from the electronic circuits is formed; an unit circuit board 20′ which is attached on a portion of semiconductor chip 10, other than bond pad 11, with adhesive means 30, and includes copper sheet 21, the upper and lower sides of copper sheet 21 being coated with a nonconductive material, circuit pattern 23 being formed on the upper side; wire 40 for transmitting a signal between bond pad 11 of semiconductor chip 10 and circuit pattern 23; sealant 50 covering the wire bonded area to protect it from external oxidation and corrosion; and solder ball 60 fused on circuit pattern 23, to externally transmit a signal of semiconductor chip 10 sent through wire 40.

[0029] Bond pad 11 formed on semiconductor chip 10 may be arranged at the center of the upper surface of semiconductor chip 10, as shown in FIG. 6. Otherwise, as shown in FIG. 7, bond pad 11 may be arranged at the edges of the upper surface of semiconductor chip 10. The semiconductor package of the present invention is a chip size package which has the same size as that of semiconductor chip 10. With this package, a signal output from semiconductor chip 10 is transmitted to circuit pattern 23 through wire 40, and then supplied to a mother board through solder ball 60 fused on circuit pattern 23, to be sent to a peripheral device. A signal generated by the peripheral device is transmitted to semiconductor chip 10 through a transmission path opposite to the above one.

[0030] According to the present invention, only semiconductor chips judged as good ones by a test which is carried out to semiconductor chips in wafer state are selectively attached to the circuit board sheet, to fabricate the semiconductor package, thereby preventing the generation of poor semiconductor chip and realizing a compact multi-pin semiconductor package.

[0031] It will be apparent to those skilled in the art that various modifications and variations can be made in the method of fabricating a semiconductor package of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.