Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package
Reexamination Certificate
2000-05-30
2001-07-24
Chaudhuri, Olik (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
C257S706000, C257S712000
Reexamination Certificate
active
06265767
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel semiconductor plastic package in the form in which at least one semiconductor chip is mounted on a small-sized printed wiring board, a metal plate for the above package and a method of producing a copper-clad board for the above package. It relates particularly to a semiconductor plastic package suitable for relatively high-watt, multi-terminal and high-density semiconductor plastic packages such as a microprocessor, a micro-controller, ASIC and graphic, and a method of producing the same. The semiconductor plastic package of the present invention is used for an electronic device by mounting it on a mother board wiring board with solder balls.
2. Description of Prior Art
There are conventionally known semiconductor plastic packages such as a plastic ball grid array (P-BGA) and a plastic land grid array (P-LGA), which are structured by fixing a semiconductor chip on the upper surface of a plastic printed circuit board, bonding the semiconductor chip to a conductor circuit formed on the upper surface of the printed circuit board by wire-bonding, forming a conductor pad for connection to a mother board printed circuit board on the lower surface of the printed circuit board with a solder ball, connecting front and reverse circuit conductors with a plated through-hole and encapsulating the semiconductor chip with a resin. In the above known structure, a plated heat-diffusible through-hole to connect a semiconductor-chip-fixing metal foil on the upper surface to the lower surface is formed for diffusing heat generated in the semiconductor chip to the mother board printed circuit board.
There is a risk that moisture may be absorbed through the above through hole into a silver-powder-containing resin adhesive used for fixing a semiconductor and may cause an interlayer swelling due to heating at a time of mounting the above package on the mother board or heating when a semiconductor part is removed from the mother board, and it is called a “popcorn phenomenon”. When the popcorn phenomenon takes place, the package is no longer usable in most cases, and it is required to overcome the above phenomenon to a great extent.
Further, attaining of higher functions of a semiconductor and increasing a density thereof imply an increase in the amount of heat to be generated, and the formation of only a through-hole immediately below the semiconductor chip for diffusing heat is not sufficient any more.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a semiconductor plastic package having excellent heat diffusibility and heat resistance after moisture absorption, and a method of producing the same.
It is another object of the present invention to provide a semiconductor plastic package having a novel structure which is suitable for mass-production and is improved in economic performances, and a method of producing the same.
According to the present invention, there is provided a semiconductor plastic package having a structure in which a metal sheet having a size nearly equal to the size of a printed wiring board is disposed nearly in the middle of the thickness direction of the printed wiring board, at least one semiconductor chip is fixed on one surface of the printed wiring board with a thermally conductive adhesive, the metal sheet is insulated from circuits on the front and reverse surfaces of the printed wiring board with a thermosetting resin composition, a circuit conductor formed on the surface of the printed wiring board and the semiconductor chip are connected with each other by wire bonding, a signal propagation circuit conductor on the surface of the printed wiring board and a circuit conductor formed on the reverse surface of the printed wiring board or a circuit conductor pad formed for connection to an external portion of said package with solder balls are at least connected with a through hole conductor insulated from the metal sheet with a resin composition, at least one through hole forms a direct junction with the metal sheet disposed as an inner layer, and at least the semiconductor chip, the bonding wire and the bonding pad are encapsulated,
wherein a plurality of protrusions having the form of a cone or a frustum of a cone each are formed on that portion of at least one surface of the metal sheet which is within an area where the semiconductor chip is mounted, and tops of said metal protrusions are in contact with the thermally conductive adhesive or a metal foil.
Further, according to the present invention, there is provided a semiconductor plastic package as recited above, wherein a plurality of the metal protrusions having the form of a cone each are formed on a portion where the semiconductor chip is directly mounted and the tops of said metal protrusions are in contact with the thermally conductive adhesive, a solder or a metal foil on which the semiconductor chip is mounted.
Further, according to the present invention, there is provided a semiconductor plastic package as recited above, wherein a plurality of the metal protrusions having the form of a frustum of a cone each are formed on a metal portion where the semiconductor chip is directly mounted and the tops of said metal protrusions are in contact with the thermally conductive adhesive, a solder or a metal foil on which the semiconductor chip is mounted.
Further, according to the present invention, there is provided a semiconductor plastic package as recited above, wherein a plurality of the metal protrusions having the form of a frustum of a cone each are exposed from part of the metal portion where the semiconductor chip is directly mounted, or the metal protrusions are coated with a metal plating, and the semiconductor chip is fixed on the metal protrusions having the form of a cone or a frustum of a cone and the metal foil.
Further, according to the present invention, there is provided a semiconductor plastic package as recited above, wherein a plurality of the metal protrusions having the form of a cone or a frustum of a cone are in direct contact with a metal foil to which the semiconductor chip are directly fixed, or a plurality of the metal protrusions are in contact with the metal foil through a thermally conductive adhesive, a plane which is opposite to, and corresponds nearly to, a plane to which the semiconductor chip is fixed is provided with a plurality of metal protrusions having the form of a cone or a frustum of a cone and said metal protrusions are in contact with a metal foil.
Further, according to the present invention, there is provided a semiconductor plastic package as recited above, wherein a plurality of the metal protrusions having the form of a cone or a frustum of a cone are in contact with the metal foil through a thermally conductive adhesive.
Further, according to the present invention, there is provided a semiconductor plastic package as recited above, wherein tops of a plurality of the metal protrusions are exposed independently of a front-surface metal foil to which the semiconductor chip is directly fixed and a reverse-surface metal foil to which solder ball pads are fixed, the exposed top portions of the metal protrusions are desmeared, the through hole for conduction between circuits on the front and reverse surfaces, the through hole is entirely plated with a metal, circuits are formed on the front and reverse surfaces, and at least a semiconductor-chip-mounting portion, a bonding pad portion and a solder ball pad portion are plated with noble metal.
Further, according to the present invention, there is provided a semiconductor plastic package as recited above, which may have a double-side metal-foil-clad laminate prepared by forming an elevated flat portion on one surface of the metal sheet constituting part of the printed wiring board on the semiconductor-chip-mounting side, forming the metal protrusions having the form of a cone or a frustum of a cone on the other surface opposite to the above surface, making a clearance hole or a slit for the through h
Gaku Morio
Ikeguchi Nobuyuki
Kobayashi Toshihiko
Chaudhuri Olik
Ha Nathan W.
Mitsubishi Gas Chemical Company Inc.
Wenderoth , Lind & Ponack, L.L.P.
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