Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Die bond
Reexamination Certificate
2000-03-22
2002-07-30
Clark, Sheila V. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Die bond
C257S731000, C438S119000
Reexamination Certificate
active
06426565
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to an electronic package for use in packaging semiconductors, and more particularly to such packages wherein an electronic device (e.g. semiconductor chip) is located on a substrate and coupled thereto.
BACKGROUND OF THE INVENTION
Packaging techniques for integrated circuits have developed with an emphasis on miniaturization. Improved methods enable integrating millions of transistor circuit elements into single integrated semiconductor embodied circuits or chips, and has resulted in more reliable, mass-producible packages. Forming an electronic package requires combining a plurality of circuits and integrated circuits and electrically connecting these circuits together. Once connected, other devices such as keyboards, video monitors and printers, may be connected and utilized together.
In order to establish this interconnection, conductive paths must be made available to connect the circuitry of the integrated semiconductor chip to external system electrical circuits. In one electronic package, for example in U.S. Pat. No. 5,808,873, by Celaya et al., an integrated semiconductor chip is positioned face up (die up) and secured with a quantity of adhesive to a conductive die mount pad on the surface of a substrate. The electronic package substrate includes a plurality of conductive pads, selected ones of which are electrically interconnected to a plurality of bond pads on the integrated semiconductor chip by, for example, wire bonding or other known techniques. The plurality of conductive pads in turn are connected to conductors and to electronic package pins or leads, extending from the package, that are used to connect to printed circuit boards or cards. Ball grid arrays (BGAS) can also be used for achieving a higher density of external package connections to be made as compared to packages having pins or leads extending therefrom.
In certain other electronic packages, a stiffener is joined to a substrate such as a printed circuit board or laminate circuit element, having a cavity in it for receiving an integrated semiconductor chip. In this type of package, the cavity extends completely through the substrate This type of structure can be referred to as a “cavity down” electronic package. For examples of cavity down packages see U.S. Pat. Nos. 5,798,909 and 5,724,232 both by Bhatt et al. Another type of “cavity” down electronic package can have a cavity formed in a substrate, for receiving an integrated semiconductor chip, wherein the cavity does not extend completely through the substrate. The integrated semiconductor chip is secured in the cavity by a quantity of adhesive to either the stiffener or a conductive die mount pad on the substrate. The substrates of the “cavity down” packages can also each include a plurality of conductive pads, selected ones of which are electrically interconnected to a plurality of bond pads on the respective integrated By semiconductor chips by, for example wire bonding or other known techniques.
These packages and methods of making them may exhibit a serious problem. In particular, the adhesive, either during lamination or curing, will have a tendency to bleed from under the integrated semiconductor chip. If not prevented, it may be possible for the adhesive to contact one or more of the nearby plurality of conductive pads, possibly adversely affecting the wirebondability of the conductive pads. The method of making these electronic packages is relatively difficult to control and some attempts to control the amount of bleed by in turn controlling the viscosity of the adhesive and the time and/or temperature of the lamination and cure have not been entirely successful.
The present invention is directed at overcoming the problem set forth above. It is desirable to have an electronic package and method to make the electronic package that will substantially prevent adhesive that bleeds from under an integrated semiconductor chip from contacting a plurality of conductive pads on the substrate. Electronic packages produced by this method will have increased yield, lower cost, and improved operational field life, since wire bonds made between wires and conductive pads will be made without the presence of adhesive on the conductive pads.
SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to enhance the art of packaging technology.
It is another object of this invention to provide a novel method for producing an electronic package that substantially prevents adhesive, that bleeds from under an integrated semiconductor chip, from contacting one or more of a plurality of conductive pads on the substrate of the electronic package.
It is yet another object of this invention to provide an electronic package that will be manufactured with increased yields and can be produced at relatively lower costs than many current products.
Still another object of this invention is to provide an electronic package made with wire bonds without the presence of adhesive on the conductive pads of the package that results in a package having much improved operational field life.
According to one aspect of this invention, there is provided an electronic package, comprising a substrate having a first surface and a first opening located therein, the first opening having at least one side wall and a bottom wall, the bottom wall including a second opening located therein having at least one side wall and a bottom wall, the bottom wall of the first opening further including a pedestal portion having an upper surface. A plurality of conductive pads located on the first surface of the substrate relative to the first opening is also provided. The electronic package further includes an electronic device positioned on the upper surface of the pedestal portion and secured to the upper surface by a quantity of adhesive, the electronic device being electrically coupled to selected ones of the plurality of conductive pads on the first surface of the substrate, the second opening substantially preventing the adhesive from contacting the plurality of conductive pads.
According to another aspect of this invention, there is provided an electronic package, comprising a substrate having a first surface and an opening located therein, the opening having at least one side wall and a bottom wall, the first surface of the substrate including a substantially planar first portion not having an electrical conductor or the like thereon and a second portion. The electronic package further includes a plurality of conductive pads located on the second portion of the first surface of the substrate relative to the opening. The electronic package also includes an electronic device positioned on the substantially planar first portion of the upper surface of the substrate and secured to the planar first portion by a quantity of adhesive, the electronic device electrically coupled to selected ones of the plurality of conductive pads on the second portion of the first surface of the substrate, the opening substantially preventing the adhesive from contacting the plurality of conductive pads.
According to yet another aspect of this invention, there is provided a method of making an electronic package comprising the steps of providing a substrate having a first surface and a first opening located therein, the first opening having at least one side wall and a bottom wall, the bottom wall including a pedestal portion having an upper surface, and forming a second opening in the bottom wall of the first opening, the second opening having at least one side wall and a bottom wall. The method also includes forming a plurality of conductive pads on the first surface of the substrate relative to the first opening and securing an electronic device to the upper surface by a quantity of adhesive. The method further includes electrically coupling the electronic device to selected ones of the plurality of conductive pads on the first surface of the substrate, the second opening substantially preventing the adhesive from contacting the plurality of cond
Bhatt Ashwinkumar C.
Logan Paul E.
Rai Amarjit S.
Clark Sheila V.
Fraley Lawrence R.
International Business Machines - Corporation
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