Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – For plural devices
Reexamination Certificate
1999-02-11
2001-01-23
Williams, Alexander O. (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
For plural devices
C257S790000, C257S784000, C257S787000, C257S788000, C257S674000, C257S687000, C257S698000, C257S669000, C257S666000, C257S692000, C438S124000, C029S516000, C029S592100
Reexamination Certificate
active
06177726
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to packaging of semiconductor devices and, more particularly, to techniques for insulating bonding wires during assembly of an integrated-circuit package.
2. Prior Art
The trend in integrated circuit packaging is to have the spacing between bonding pads on an integrated circuit die become smaller so that the pitch of the bonding pads gets tighter. For this reason and for other reasons, such as this use of multiple bonding tiers, the length of the bonding wires in integrated circuit packages are getting longer and longer bonding wires have a tendency to electrically short-circuit together.
Various attempts have been made to electrically insulate bonding wires to avoid having adjacent wires touching each other and electrically short-circuit. One technique provides insulation on the wires prior to wire bonding. Insulating the bonding wires prior to bonding created problems such as modification of wire-bonding machines, increased costs, decreased yields, and charring of the insulation material which contaminates the integrated-circuit die.
Another technique provides for coating the bonding wires with a silicone spray after wire bonding. Using this so-called “wet” technique, the sprayed silicone material can get on the leadframe or substrate on which the die is mounted. During encapsulation of the die and bonding wires, this silicone material causes a loss of adhesion of the encapsulating material to the leadframe or substrate. This silicone spray also prevents good adhesion of plating materials on the leadframe.
Consequently, a need exists for a dry technique for electrically insulating bonding wires to prevent electrical short circuits therebetween.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a technique for providing electrical insulation to the bonding wires of an integrated-circuit package after wire-bonding and during assembly of the package to prevent electrical short circuits between adjacent bonding wires in the integrated-circuit package.
In accordance with these and other objects of the invention, a semiconductor integrated-circuit die is singulated and die-attached to a leadframe or a substrate. Wire bonds are formed between the die and the package leads using aluminum or copper bonding wires. Next, the wire-bonded ICs are subjected to a plasma-enhanced chemical vapor deposition PECVD process where silicon dioxides S
i
O
2
vapor is deposited on the bonding wires and the IC die as well as on a leadframe or substrate. An insulating PECVD S
i
O
2
layer of aluminum oxide or copper oxide on the bonding wires. The assembly is then encapsulated as either a molded plastic package, a grid-array package including a glob-top package, or a pin-grid array package. For a molded plastic package with a leadframe, the S
i
O
2
layer is then removed from the leads of a molded plastic package by a media-blasting process and the leads are plated with Pb/Sn coating.
A method is provided according to the invention for packaging a semiconductor integrated circuit with insulated bonding wires. The method includes: attaching a semiconductor die to a mounting base and wire-bonding a plurality of aluminum or copper bonding wires between respective bonding pads on the semiconductor die and respective bonding fingers at the inner ends of leads of a leadframe if a lead frame is used. After wire bonding, the bonding wires are subjected to a PECVD S
i
O
2
vapor to form a silicon dioxide layer on the package component including especially the plurality of bonding wires to thereby provide electrically-insulated bonding wires to prevent short-circuits between adjacent bonding wires of the package. For a package with a leadframe, the semiconductor die, the bonding wires, and the bonding fingers are encapsulated to expose the oxidized outer ends of the leads. The PECVD silicon dioxide on the exposed outer ends of the leads of the leadframe are removed by blasting with a media. For a grid-array package, such as a ball-grid array package or a pin-grid array package, a die is mounted to a polymer substrate and the bonding wires are attached to conductors formed on the polymer substrate. The grid-array entire assembly is then subjected to a PECVD S
i
O
2
vapor to provide an insulation layer thereupon. For a ball-grid array package, the S
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2
on the solder ball attach pads are removed using a blasting media.
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King Patrick T.
Philips Electronics North America Corporation
Williams Alexander O.
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