Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Including adhesive bonding step
Reexamination Certificate
1998-03-13
2001-07-17
Chaudhuri, Olik (Department: 2814)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Including adhesive bonding step
C257S684000, C257S707000
Reexamination Certificate
active
06261867
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a package for a microelectronic device and a method of making such a package, and in particular, a package configured to provide for a high degree of heat dissipation for a microelectronic device bonded directly to a base of the package.
A microelectronic device, such as a semiconductor device, typically includes a semiconductor chip having a series of bonding conductive pads for electrically connecting the chip to other components of an electrical circuit. Semiconductor chips are typically made with a substrate of silicon, gallium arsenide or other semiconductor material. The bonding conductive pads are electrically connected to conductive leads of a lead frame disposed adjacent to the chip. The electrical connections may be made, e.g., by wire bonding the conductive pads to the conductive leads using ultrafine lead wires.
The semiconductor device and portions of the lead frame are usually mounted in a protective package. After the electrical connections are made, the semiconductor device is encapsulated and completely sealed within the package to protect the device.
During operation of the semiconductor device, various portions of the semiconductor chip may become hot. If heat generated by the semiconductor chip during its operation is not dissipated from the package, the frequency of the operating chip may be altered from its designated operating frequency thereby adversely affecting the performance of the device. Further, excessive heat retained by the package may damage the chip itself. To avoid frequency alteration and overheating of the device during its operation, various heat removal techniques have been suggested.
SUMMARY OF THE INVENTION
In general, in one aspect, the invention features a package for a microelectronic device, including a thermally conductive base containing a metal composite including a high conductivity metal and a ferrous alloy, the base having a surface with an iron oxide deposit disposed thereon. An insulating substrate is disposed on the surface of the base, the substrate having an aperture formed therein, the aperture exposing a portion of the surface of the base for mounting the device on the base. A conductive lead has a portion thereof embedded within the insulating substrate and is adapted to be electrically connected to the device. The insulating substrate may be bonded to the iron oxide deposit disposed on the surface of the base.
Implementations of the invention may include one or more of the following features. The insulating substrate may include borosilicate glass, which may include alkali barium borosilicate with 25% alumina. The ferrous alloy may include iron, nickel and cobalt. The high conductivity metal of the metal composite may include silver. The microelectronic device may be a semiconductor device including a semiconductor chip.
The conductive lead may include an alloy containing iron, nickel and cobalt, and may also include an iron oxide deposit disposed on a surface of the lead so that the insulating substrate may be bonded to the iron oxide deposit.
The package may further include an additional substrate portion disposed on the conducting lead and sealed to the insulating substrate, and a sealing ring disposed on and sealed to the additional substrate portion.
The microelectronic device may be bonded directly to the base by a thermally conductive substance. A portion of the base under the microelectronic device may be raised with respect to the conductive lead.
In general, in another aspect, the invention features a package for a microelectronic device, including a thermally conductive base containing a metal composite including silver and a ferrous alloy, the base having a surface with an iron oxide deposit disposed thereon. An insulating substrate containing borosilicate glass is disposed on the surface of the base, the substrate having an aperture formed therein, the aperture exposing a portion of the surface of the base for mounting the device on the base. A conductive lead has a portion thereof embedded within the substrate and is adapted to be electrically connected to the device. The insulating substrate is bonded to the iron oxide deposit disposed on the surface of the base.
In general, in another aspect, the invention features a method of making a package for a microelectronic device. A thermally conductive base is provided, the base containing a metal composite including a high conductivity metal and a ferrous alloy, and having a surface with an iron oxide deposit disposed thereon. An insulating substrate having an upper surface and a lower surface is provided, the substrate having an aperture formed therein, the aperture exposing a portion of the surface of the base for mounting the device on the base. A conductive lead is also provided. The lower surface of the insulating substrate is disposed on the surface of the base and the conductive lead is disposed on a portion of the upper surface of the insulating substrate to provide an assembly. The assembly is heated to bond the iron oxide deposit disposed on the surface of the base to the lower surface of the insulating substrate and to embed the conductive lead on the portion of the upper surface of the insulating substrate.
Implementations of the invention may include one or more of the following features. The method may also include processing the conductive lead with an outgassing operation before the step of oxidizing the base, and oxidizing the conductive lead to form an iron oxide deposit on the conductive lead. The method may further include assembling the substrate, the base and the conductive lead in a fixture prior to the heating step.
The heating step may include raising the temperature to a temperature in the range of about 935° C. to about 980° C., to about 955° C., or to no more than about 980° C.
The method may also include bonding the microelectronic device directly to the base by a thermally conductive substance. The method may further include sealing the microelectronic device within the package.
An advantage of the present invention is that heat generated by a microelectronic device inside a sealed package is quickly dissipated through the base, which includes a material with high thermal dissipation properties.
An additional advantage of the present invention is that a package for a microelectronic device having high thermal dissipation properties may be manufactured simply and inexpensively.
A further advantage of the present invention is that a hermetic seal may be formed between the base and the insulating substrate forming the package simply by heating, without requiring the use of an additional substance such as an adhesive or solder.
Other features and advantages of the invention will become apparent from the detailed description, and from the claims.
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Silver (K) Heatsinks, Potese Co., San Diego, CA 1998.
Duff Raymond
Robichaud John R.
Taber Donald C.
Brown Martin Haller & McClain
Chaudhuri Olik
Stratedge Corporation
Weiss Howard
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