Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-12-09
2001-12-04
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S830000, C029S831000, C029S827000, C257S707000, C257S706000
Reexamination Certificate
active
06324756
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to plastic ball grid array packages and more particularly to a method and system for sealing the edges of the substrate of the packages, thereby providing improved reliability and performance of the package.
BACKGROUND OF THE INVENTION
Conventional plastic ball grid array (“PBGA”) packages are used in a variety of semiconductor applications. Both micro-BGA and PBGA packages are currently available. Conventional micro-BGA packages are chip-scale packages. As their name suggests, conventional micro-BGA packages are significantly smaller than PBGA packages.
Conventional micro-BGA packages are formed on a tape substrate. Semiconductor dies are attached to the tape. Electrical connection is made between the dies and metal traces within the tape. The gaps between semiconductor dies are then filled with an adhesive encapsulant. The adhesive encapsulant aids in sealing and protecting the edges of the die. The tape is then cut between the dies, forming micro-BGA packages.
Conventional PBGA packages are significantly larger than conventional micro-BGA packages. Because of the difference in size, conventional PBGA packages are typically manufactured using very different processes and materials than micro-BGA packages. The conventional PBGA package includes a semiconductor die attached to a substrate. However, the substrate is similar to a printed circuit board. Typically, the substrate used is a BT (Bismaliemide Triazine) substrate. The substrate not only provides a relatively stiff surface to which the semiconductor die can be attached but also electrically couples the die to the solder balls. Consequently, the substrate includes conductive traces with insulating layers interspersed between the conductive traces.
Contacts on the semiconductor die are typically electrically coupled to the metallic traces in the substrate through wires bonded to a contact on the surface of the substrate. The semiconductor die is also typically covered in a molding compound, such as an epoxy. The molding compound aids in protecting the die from the environment and contributes to the robustness of the package. Solder balls on a side of the substrate opposite to the die can electrically connect the PBGA package to another circuit.
Typically, conventional PBGA packages are formed by attaching a number of dies to a long strip of substrate that is designed to accommodate the dies. The dies are then electrically coupled and molded to the substrate. After the PBGA packages are substantially formed, the substrate is cut to separate the conventional PBGA packages. The conventional PBGA packages may then be used in other circuits.
Although conventional PBGA packages are useful for many applications, the PBGA package may be prone to failure. For example, moisture may enter the substrate, and adversely affect the reliability of the PBGA package.
Accordingly, what is needed is a system and method for improving the reliability of the substrate in a PBGA package. The present invention addresses such a need.
SUMMARY OF THE INVENTION
The present invention comprises a system and method for providing plastic ball grid array (“PBGA”) packages. In one aspect, the method and system provide a plurality of PBGA packages. Each of the plurality of PBGA packages includes a semiconductor die and a portion of a substrate. The semiconductor die is electrically coupled to the portion of the substrate. The portion of the substrate has an edge. In this aspect, the method and system comprise forming the plurality of PBGA packages on the substrate and separating the portion of the substrate for each of the plurality of PBGA packages. The portion of the substrate for one of the plurality of PBGA packages is separated from the portion of the substrate for another of the plurality of PBGA packages by a gap. This gap may be created by a punching or cutting process. The method and system further comprise filling the gap with a moisture sealant and sawing along the center of the gap (now filled with the moisture sealant) to separate the plurality of PBGA packages. The edge of the portion of the substrate for each of the plurality of PBGA packages is substantially covered by the moisture sealant. In another aspect, the method and system comprise providing a semiconductor die, a substrate having an edge, and a moisture sealant. The semiconductor die is electrically coupled to the substrate. The substrate has an edge. The moisture sealant substantially covers the edge of the substrate.
According to the system and method disclosed herein, the present invention seals the edge of the substrate of the PBGA packages, thereby increasing reliability of the PBGA package.
REFERENCES:
patent: 4090231 (1978-05-01), Millard
patent: 5599630 (1997-02-01), Smith et al.
patent: 5717252 (1998-02-01), Nakashima et al.
patent: 5787569 (1998-08-01), Lotfi et al.
patent: 5890284 (1999-04-01), Chartrand
patent: 5892417 (1999-04-01), Johnson et al.
Gannamani Ranji
Li Xia
Advanced Micro Devices , Inc.
Sawyer Law Group LLP
Smith Sean
Young Lee
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