BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view schematically showing a conventional BGA package structure that mounted on a PCB;
FIG. 2 is a sectional view schematically showing a conventional wBGA package structure that mounted on a PCB;
FIG. 3A is a sectional view schematically showing the BGA package structure according to one embodiment of the present invention;
FIG. 3B is a bottom view schematically showing the embodiment illustrated in FIG. 3A;
FIG. 4A and FIG. 4B are sectional views schematically the fabrication process of the BGA package structure according to one embodiment of the present invention; and
FIG. 4C and FIG. 4D are sectional views schematically showing the electronic packaging structures of the BGA package structures respectively according to different embodiments of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Refer to FIG. 3A a sectional view schematically showing the BGA package structure according to one embodiment of the present invention. As shown in FIG. 3A, the BGA package structure includes: a substrate 10; a chip 11 arranged on a upper surface of the substrate 10; a plurality of through holes penetrating the substrate 10 and disposed around the perimeter of the chip 11; an encapsulant 30 covering the chip 11 and filling those through holes 13 to form a window-type bump 32 on a lower surface of the substrate 10; and a plurality of conductive balls 40 arranged on the lower surface of the substrate 10, wherein a plurality of electric contacts (not shown in the drawing) are formed on the lower surface of the substrate 10, and the chip 11 is electrically connected with those electric contacts, and those conductive balls 40 are disposed on those electric contacts. In this embodiment, the material of the substrate 10 is selected from the group consisting of polyimide, glass fiber, alumina, epoxy, beryllium oxide and elastomer. The chip 11 is electrically connected to those electric contacts with a plurality of metallic lead wires 20, such as conductive wires, via a wiring bonding process. The encapsulant 30 is essentially composed of epoxy resin and filler, and those conductive balls 40 are conductive solder balls.
Refer to FIG. 3B, a bottom view schematically showing the embodiment illustrated in FIG. 3A, wherein FIG. 3A is the sectional view along line A-A′ in FIG. 3B. As shown in FIG. 3B, those conductive balls 40 are disposed within the electric-contact region 12 on the lower surface of the substrate 11, and the window-type bump 32 simultaneously formed with the encapsulant 30 and to encircle those conductive balls 40. After the encapsulant material has been compressively filled into the mold, a curing process is undertaken, and the window-type bump 32 can enhance the strength of the substrate 10 in the curing process; thus, the window-type bump 32 can balance the mismatch of thermal expansion coefficients, reduce the thermal warpage resulting from the difference in thermal expansion coefficients of the encapsulant 30, the substrate 10, the chip and other materials. The application of the encircling bumps 32 is not limited to the BGA package structure shown in this embodiment. The encircling bump 32 may also apply to the FBGA (Fine pitch Ball Grid Array) package structure, the VFBGA (Very Fine pitch Ball Grid Array) package structure, the BGA (micro Ball Grid Array) package structure and the wBGA (window Ball Grid Array) package structure. As shown in FIG. 3B, there are a plurality of through holes 13; however, the present invention is not limit to the case shown in FIG. 3B. In cooperation with different mold designs, the encircling bump may be fabricated via a plurality of through holes or even only one through holes. The shape of the through hole 13 may be a circle, an ellipse, a polygon, a strip, or a multiple-arc shape.
Refer to FIG. 4A and FIG. 4B sectional views schematically the fabrication process of the BGA package structure according to one embodiment of the present invention, wherein FIG. 4A is a sectional view schematically showing that a chip is stuck onto a substrate, and FIG. 4B is a sectional view schematically showing that the chip and the substrate is packaged via compressively filling a packaging resin into a mold. As shown in FIG. 4A, a chip 11 is arranged on a substrate 10 firstly; next, the chip 11 and the substrate 10 are electrically interconnected with a plurality of metallic lead wires 20. Next, as shown in FIG. 4B, the chip 11 together with the substrate 10 is placed inside a mold 35; next, a encapsulant 30 is compressively filled into the mold 35 so that the encapsulant 30 can cover the chip 11, the substrate 10 and those metallic lead wires 20 and pass through those through holes 13 to completely fill the mold 35 with electric contacts (not shown in the drawing) exposed on the lower surface of the substrate 10. Next, a curing process is used to fully harden the encapsulant 30. The encapsulant 30 passing through those through holes 13 is also hardened to form the encircling bump 32. Next, as shown in FIG. 3A, a plurality of conductive balls 40 are arranged on the lower surface of the substrate 10 and respectively electrically connected to those electric contacts, and the BGA package structure is thus completed.
Refer to FIG. 4C and FIG. 4D sectional views schematically showing the electronic packaging structures of the BGA package structures respectively according to different embodiments of the present invention. As shown in FIG. 4C, the electronic packaging structure of the BGA package structure includes: a printed circuit board 50 and a BGA package structure 60. The BGA package structure 60 has a plurality of conductive balls 40 arranged on the lower surface thereof and has window-type bump 32 arranged in the perimeter of the lower surface and encircling those conductive balls 40. The printed circuit board 50 has an electric-connection region (not shown in the drawing); the BGA package structure 60 is fixed to and electrically connected to the electric-connection region of the printed circuit board 50 via those conductive balls 40. The height of the encircling bump 32 of the BGA package structure 60 is not greater than the spacing between the BGA package structure 60 and the printed circuit board 50 so that the bump will exactly touch the printed circuit board 50 or will not touch the printed circuit board 50 until external force acts on the BGA package structure 60. Thereby, the bump 32 can provide a support for the BGA package structure 60 lest the BGA package structure 60 be damaged by external force. The printed circuit board 50 further includes a plurality of conductive solder pads (not shown in the drawing), which corresponds to those conductive balls 40 and are fixed to those conductive balls 40 to form the electric connection therebetween. The description of the structure of the BGA package structure 60 has been stated above and will not repeat here. The BGA package structure 60 may also be a FBGA package structure, a VFBGA package structure, a. BGA package structure, or a wBGA package structure.
Refer to FIG. 4D a sectional view schematically showing the present invention applies to the electronic packaging structure of a wBGA package structure. Such a thin package structure is very fragile, and the chip 11 thereof is apt to be damaged by external force. In this embodiment, the encircling bump 32 may provide a support for the package structure lest the package structure be cracked by external force. When the user assembles the semiconductor module, the present invention can prevent the package structure from being damaged by external force, such as too great a force applied by the user. Thereby, the yield and lifetime of the package structure can be increased, and the economic efficiency can also be promoted.
In summary, the present invention utilizes the window-type bump to improve the package structure. Thereby, in the curing process succeeding to the resin-filling process, the warpage of the package structure can be effectively reduced. Further, after the package structure has been assembled with an SMT process, the window-type bump can also provide a support for the package structure lest the package structure be damaged by external force. Furthermore, the encircling bumps of the package structure are simultaneously formed with the encapsulant body via compressively filling the encapsulant into the mold; thus, the encircling bumps are formed in the existing packaging process, and neither extra process nor extra cost is needed. Therefore, the present invention can raise yield and reduce cost simultaneously.
Although the present invention has been explained in relation to its preferred embodiment, it is to be understood that other modifications and variation can be made without departing the spirit and scope of the invention as hereafter claimed.
Patent Application
20070246814
