Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
2000-12-08
2003-02-04
Smith, Matthew (Department: 2825)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S614000, C438S616000, C438S106000, C438S118000, C438S685000, C438S975000
Reexamination Certificate
active
06514846
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to semiconductor encapsulation and, more specifically, to a method of fabricating soldering balls for semiconductor encapsulation.
Nowadays, BGA and CSP techniques have been popularly used in semiconductor encapsulation. As shown in
FIG. 1
, soldering balls are provided instead of mounting legs for soldering to the substrate. The application of soldering balls greatly reduces the dimension of the encapsulated semiconductor. However, the quality of soldering balls affects the quality of the semiconductor. Conventionally, the fabrication of soldering balls is to draw a metal wire rod into a thin wire subject to the desired thickness, and then to cut the metal wire into pieces of metal wire, and then to mold the pieces of metal wire into soldering balls. The soldering ball molding procedure is to blow each piece of metal wire through a round mold in a wind tunnel molding apparatus. This method cannot well control the quality of finished soldering balls. After blow molding, fine-protruding portions may form on finished soldering balls in direction of the movement of airflows.
SUMMARY OF THE INVENTION
The present invention provides a soldering ball fabrication method, which eliminates the aforesaid problem. It is one object of the present invention to provide a soldering ball fabrication method, which greatly saves the manufacturing cost. It is another object of the present invention to provide a soldering ball fabrication method, which greatly increases the yield. According to the present invention, a metal wire rod is drawn into the desired thickness and then cut into pieces subject to the desired length, and then the pieces of metal wire are melted and let fall through screens in a vacuum apparatus to form balls, and then the balls are selected and inspected so as to obtain qualified soldering balls.
REFERENCES:
patent: 3652259 (1972-03-01), Knopp
patent: 5653783 (1997-08-01), Ohzeki
Anya Igwe U.
Smith Matthew
Troxell Law Office PLLC
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