Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With semiconductor element forming part
Reexamination Certificate
2005-08-16
2005-08-16
Williams, Alexander Oscar (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With semiconductor element forming part
C257S796000, C257S784000, C257S786000, C257S734000, C257S737000, C257S738000, C257S691000, C257S776000, C257S775000, C257S676000, C257S675000, C257S787000
Reexamination Certificate
active
06930377
ABSTRACT:
A number of apparatus for packaging semiconductor devices using an epoxy ink or adhesive. In one embodiment, a pattern of epoxy is formed on the bottom surface of die attach pad of a leadless semiconductor package. The pattern of epoxy divides the undersurface of the die attach pad into a grid of small squares. A small amount of solder paste is then applied within each square of the grid. When the leadless package is attached to a substrate, each of the solder balls evenly reflows to the same approximate height. This enhances the attachment of the package to the substrate and reduces the need for rework. In another embodiment, a protective layer of epoxy or ink is provided around the periphery of the die after it has been attached to the die attach pad. The protective layer covers any solder material that may leach out from between the die and the die attach pad. In another embodiment, a protective layer of epoxy or ink is provided on the exposed tie bars of the lead frame after encapsulation. The protective layer of ink helps reduce burring and the formation of slivers at the cutting surface when the tie bars are cut during singulation. In another embodiment, an isolation layer of epoxy or ink may be used to cover and electrically isolate the leads of a lead frame. Finally, in yet another embodiment, a patterned layer of epoxy or ink may be used on the bottom surface of a semiconductor package. The layer of ink is patterned to include a plurality of recess regions that form a physical barrier surrounding where solder contact balls are to be formed on the package surface. The patterned layer of ink thus prevents solder ball “swimming” by confining the solder balls to within the physical barriers created by the recess regions.
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Beyer Weaver & Thomas LLP
National Semiconductor Corporation
Williams Alexander Oscar
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