Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2000-06-05
2001-12-11
Picard, Leo P. (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S702000, C361S719000, C257S706000, C165S080300
Reexamination Certificate
active
06330158
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to semiconductor packaging, and specifically to an improved semiconductor package having interlocking heat sinks. This invention also relates to a method for fabricating the package, and to an electronic assembly fabricated using multiple interlocked packages.
BACKGROUND OF THE INVENTION
A conventional plastic semiconductor package includes a semiconductor die wire bonded to a lead frame, and encapsulated in a plastic body. One consideration in designing a plastic package is heat transfer from the die. Operation of the integrated circuits within the die generate heat which must be dissipated. In a conventional plastic semiconductor package, the bulk of heat transfer from the encapsulated die is through the terminal leads of the package. However, as circuit densities increase, semiconductor dice generate additional heat, and the leads of the package are not always able to efficiently dissipate the heat.
This has led to the development of semiconductor packages that include a heat sink. Typically, the heat sink comprises a metal plate embedded in the plastic body of the package. Representative heat sink packages are described in U.S. Pat. No. 5,666,003 entitled “Packaged Semiconductor Device Incorporating Heat Sink Plate”, and in U.S. Pat. No. 5,629,561 entitled “Semiconductor Package With Integral Heat Dissipator”.
One consideration in packages that incorporate a heat sink is the thermal path from the die to heat sink. In some designs the thermal path may depend on direct contact of the die with the heat sink. However, the contact areas between the die and the heat sink may have a relatively small surface area. In other designs, the heat sink may not have direct contact with the die, but rather is in contact with the lead frame. The thermal path from the die to the heat sink is thus through the lead frame. This thermal path may not be as efficient as is desirable for dissipating as much heat as possible from the die.
Another consideration in packages that incorporate a heat sink is heat transfer from the heat sink to the environment. In most electronic assemblies that incorporate heat sink semiconductor packages, heat transfer to the environment is by convection to the air. Alternately, a liquid coolant can be used to transfer heat from the individual packages or from the assembly as a whole.
It would be advantageous for a heat sink to provide efficient heat transfer not only from the die, but also from the die to the environment. The present invention is directed to a semiconductor package that includes multiple heat sink elements having efficient heat transfer paths to the die, and to the environment. In addition, the semiconductor package is constructed such that the heat sinks on adjacent packages of an electronic assembly can be interlocked to maintain physical and thermal contact therebetween.
SUMMARY OF THE INVENTION
In accordance with the present invention, an improved semiconductor package, a method for fabricating the package, and an electronic assembly fabricated using multiple packages, are provided. The package includes a semiconductor die, a lead frame and a plastic body. The lead frame forms internal signal traces, and terminal leads for the package.
The package also includes a first heat sink attached to a face of the die, and a second heat sink attached to a backside of the die. A thermally conductive adhesive directly attaches the heat sinks to the die, and provides thermal paths therebetween. The heat sinks project from opposing surfaces of the package body, and include end portions having contact surfaces configured for physical contact with contact surfaces on heat sinks of adjacent packages. In addition, the end portions of the heat sinks can comprise complimentary elements of an interlocking structure. In the electronic assembly, the contact surfaces on mating heat sinks provide a thermal path between adjacent packages, and an improved thermal path from the heat sinks to the environment. The interlocking structure of the heat sinks maintains the contact surfaces in physical contact.
An alternate embodiment semiconductor package includes a first heat sink bonded to the face of the die, and a second heat sink bonded to the backside of the die. In addition, a thermally conductive adhesive encapsulates the die, and forms a thermal path between the die and the heat sinks.
The method for fabricating the semiconductor package includes the steps of attaching the die to the lead frame, and wire bonding bond pads on the die to lead fingers on the lead frame. The heat sinks are then attached to the die using a thermally conductive adhesive. In order to facilitate attachment of the heat sinks to the die, and heat transfer from the die to the heat sinks, the heat sinks can be shaped to contact the edges, face and backside of the die. Following attachment of the heat sinks, the plastic body can be molded around the die and heat sinks.
For fabricating the electronic assembly, a substrate such as a printed circuit board, or ceramic module substrate can be provided. The external leads for the packages can then be bonded to the substrate. In addition, the external portions of the heat sinks can be interlocked to facilitate heat dissipation from the packages, and provide thermal paths between adjacent packages on the substrate.
REFERENCES:
patent: 3831067 (1974-08-01), Wislocky et al.
patent: 4000509 (1976-12-01), Jarvela
patent: 4945398 (1990-07-01), Kurita et al.
patent: 5067005 (1991-11-01), Michii et al.
patent: 5073521 (1991-12-01), Braden
patent: 5155661 (1992-10-01), Nagesh et al.
patent: 5177669 (1993-01-01), Juskey et al.
patent: 5191511 (1993-03-01), Sawaya
patent: 5239198 (1993-08-01), Lin et al.
patent: 5365107 (1994-11-01), Kuraishi et al.
patent: 5410451 (1995-04-01), Hawthorne et al.
patent: 5474957 (1995-12-01), Urushima
patent: 5550711 (1996-08-01), Burns et al.
patent: 5566051 (1996-10-01), Burns
patent: 5578869 (1996-11-01), Hoffman et al.
patent: 5581121 (1996-12-01), Burns et al.
patent: 5585668 (1996-12-01), Burns
patent: 5594282 (1997-01-01), Otsuki
patent: 5615475 (1997-04-01), Burns
patent: 5629561 (1997-05-01), Shin et al.
patent: 5663872 (1997-09-01), Gainey
patent: 5666003 (1997-09-01), Shibata et al.
patent: 5672548 (1997-09-01), Culmane et al.
patent: 5751061 (1998-05-01), Mays et al.
patent: 5790378 (1998-08-01), Chillara
patent: 5801437 (1998-09-01), Burns
patent: 5834850 (1998-11-01), Hotta et al.
patent: 5864175 (1999-01-01), Burns
patent: 6049125 (2000-04-01), Brooks et al.
patent: 6075288 (2000-06-01), Akram
Datskovsky Michael
Gratton Stephen A.
Micro)n Technology, Inc.
Picard Leo P.
LandOfFree
Semiconductor package having heat sinks and method of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor package having heat sinks and method of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor package having heat sinks and method of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2578779