Patent Application
20080099890
1. Field of the Invention
The present invention relates to a semiconductor package structure and more especially, relates to a ball grid array (BGA) package structure.
2. Description of the Prior Art
Integrated Circuit (IC) assembly process is the post-term manufacturing process of the semi-conductor industry, it can identify as die saw, die bond, wire bond, mold, mark, and package, and they are mainly to separate the die of the wafer to those chips, die bond, and configure the inner lead and the outer lead, and cover the IC. The package mainly provides an interface to allow the inner electrical signal electrically connect to the system through the molding material, and the package provides the protection against the destruction from the external force, the water, the air with rich moist, or the chemical and also increases the mechanical property of the IC.
During the package process, the mold is arranged on the substrate of the semi-conductor chip or the electronic device at the beginning, and then fills the liquid molding material into the cavity of the mold to cover the chip or the electronic device to form a package with completely airtight. Then, take of the mold after harden the package to complete the package process eventually.
However, according to the development of the thin package technology, the square measure of the thin substrate is big and the depth of the substrate is thin. Due to the different coefficient of thermal expansion between the substrate and the molding material, the temperature variation will cause different distention or contraction, thus, the warpage of the substrate occurred because of the stress to affect the following processes, such as the ball mount (B/M) process, the singulation, or the temperature cycling test. Furthermore, if the warpage of the substrate is too much, the chip of the package will be cracked or the electronic device will be damaged. According to the issue mentioned previously, how to overcome the warpage of the substrate during the package process is a very important issue.
According to the issue mentioned previously, the present invention provides a ball grid array package structure.
One of objects of this invention is to provide a strengthened bump formed by an encapsulant to improve the mechanical strength of the substrate of the ball grid array package structure.
Another object of this invention is to provide a ball grid array package structure to reduce the warpage of the substrate efficiently during the post molding cure process.
Another object of this invention is to provide a ball grid array package structure to enhance the mechanical strength of the substrate by configure a strengthened bump on the lower surface of the substrate, it can avoid the warpage of the substrate caused from the stress due to the temperature variation during the package process to affect the following processes.
Accordingly, one embodiment of the present invention provides a ball grid array package structure including a substrate, wherein the upper surface of the substrate has at least one chip bearing area, and a plurality of electrical-connecting points are configured on a lower surface; a plurality of chips are arranged on the chip bearing area and electrically connecting with those electrical-connecting points; a plurality of through holes penetrating the substrate at the edge of the chip bearing area; an encapsulant used to cover those chips and fill those through holes to form a strengthened bump surrounding the chip bearing area on the lower surface of the substrate; and a plurality of conductive balls are respectively arranged on those electrical-connecting points.
Other advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of the present invention.
The foregoing aspects and many of the accompanying advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
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In this embodiment, the substrate 10 is made of anyone of polyamide, glass, aluminum oxide, epoxy, beryllium oxide, or elastomer. And, the encapsulant 40 is mainly made of epoxy, the electrical-connecting point 30 is made of metal solder pad, and the conductive ball 32 is conductive stannum ball.
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During the molding process of the present invention, the substrate and the chip are arranged in the cavity at the beginning, then filling the encapsulant into the cavity and covering the chip and the substrate with the encapsulant. The electrical-connecting point on the lower surface of the substrate will not be covered and each through hole was filled with the encapsulant in the cavity. Next, processing the curing process to make the encapsulant harden and take it out of the cavity after hardens. At the mean time, the encapsulant in the through hole formed a strengthened bump on the lower surface of the substrate. Eventually, mounting those conductive balls on the lower surface of the substrate to electrically connect each electrical-connecting points respectively. Therefore, the BGA package process is complete.
Accordingly, the present invention provides a strengthened bump formed by the encapsulant to enhance the mechanical strength of the substrate to reduce the warpage of the substrate efficiently during the post molding cure process, and to avoid the warpage of the substrate caused from the stress due to the temperature variation during the package process to affect the following processes. The strengthened bump is formed by the encapsulant during the molding process, the strengthened bump can be made during the existed package process and no extra process or cost needed. Furthermore, it can raise the production yield and reduce the production cost.
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.
