Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1999-07-12
2001-08-28
Paladini, Albert W. (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S260000, C174S256000, C361S767000, C361S768000, C361S771000, C361S807000
Reexamination Certificate
active
06281445
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device and a method for making connection between two electronic components, and more specifically to a connection device that enables easy connection to and removal from a board of an electronic component such as an LSI device, and to an associated method of connection.
2. Description of the Related Art
In recent years, dramatic advances have been made in the fields of computers and communication equipment, these advances made possible by great improvement in the performance of devices such as LSI devices and other various electronic components used in such equipment. Advances in the performance of LSI devices have played a particularly important role. The mother boards of computers, for example, contain a large number of LSI devices. An LSI chip is usually housed in a package of ceramic or the like, with connection made thereto using the wiring bonding method, the ceramic package being mounted onto a printed circuit board. However, because the package is extremely large compared to the LSI chip, it requires a large amount of space to mount on the board. This mounting method is not only disadvantageous from the standpoint of achieving compact electronic apparatus, but also results in a lengthening of circuit lengths, this preventing the achievement of efficient signal processing. Additionally, in a microprocessor that operates at a high speed, because of the large number of connection points that are required, it is not possible to meet this requirement using the wire bonding method. The flip-chip bonding method was developed to solve these problems of reducing the mounting surface area, establishing a large number of connection points, and reducing the connection lengths to shorten the signal delay.
The flip-chip bonding method is a method whereby solder bumps are formed by either plating or deposition on an LSI chip or on the connection part of the board, the LSI chip and board being connected by fusing the joint formed thereby. Once the LSI chip is mounted by this method, however, there is problem that it is extremely difficult to remove. If heat is applied, the solder can be melted, enabling removal of the LSI chip. However, part of the solder remains on the board, so that when a good LSI or an upgraded LSI chip is mounted on the board, deterioration of the old solder tends to cause a bad electrical connection. When a solder that include lead is used, alpha radiation from radioactive elements such as uranium and lithium that are included in minute amounts in the lead can cause faulty operation of a semiconductor element. In the case of using solder bumps, because of a CFC solvent used to remove a reducing agent such as flux that is used when making the connection, there is the possibility of exerting an deleterious effect on the global environment.
The previously used flip-chip method will be described with reference to FIG.
6
. As a method of connecting an LSI chip to a board, a eutectic solder bump made of tin and lead formed on the LSI chip is caused to come into contact with the board, a flux which is a reducing agent is applied, and a fusion bond is made at a temperature of approximately 200° C. (FIG.
6
(
a
)). Then, a CFC solvent is used to remove this flux. The use of the above-noted CFC solvent is not desirable from the standpoint of protecting the global environment. Additionally, within the solder bumps, which contain lead, there is a minute amount of radioactive elements, which cause the problem of faulty operation of semiconductor elements (FIG.
6
(
b
)). Additionally, when the joint is melted so as to remove the LSI chip, there is the problem that solder remaining on the board results in faulty connections. (FIG.
6
(
c
)).
As described above, the prior art flip-chip method had a large number of problems.
Accordingly, it is an object of the present invention to improve on the above-noted drawbacks of the prior art, by providing a novel connection device for facilitating the connection of an electronic component such as an LSI chip to a board and removal of an electronic component from a board, enabling repeated connection thereto and removal therefrom, while providing a stable electrical contact. It is a further object of the present invention to provide a method for making the above-noted connection.
SUMMARY OF THE INVENTION
In order to achieve the above-noted objects, the present invention adopts the following basic technical constitution.
Specifically, the first aspect of the present invention is a connection device for use in connection between a first electronic component and a second electronic component, said connection device being provided on said first electronic component, said first electronic component comprising two metal layers having mutually different coefficients of thermal expansion, and a plurality of side wall pieces provided on said metal layers so as to form a connecting space to be used for connecting said first electronic component to said second electronic component.
In the second aspect of the present invention, said two metal layers having mutually different coefficients of thermal expansion are fixed to a metal layer that is provided on said first electronic component.
In the third aspect of the present invention, the approximately center portion of said two metal layers having mutually different coefficients of thermal expansion is fixed to a metal layer that is provided on said first electronic component.
In the fourth aspect of the present invention, a gap is provided between said metal layers and a surface of said first electronic component.
In the fifth aspect of the present invention, of said two metal layers having mutually different coefficients of thermal expansion, the coefficient of thermal expansion of said metal layer provided on said side wall side is larger than the coefficient of thermal expansion of said metal layer fixed to said metal layer provided on said first electronic component, and further wherein an aperture of said connecting space formed by said side wall pieces extends when heat is applied to said connection device.
In the sixth aspect of the present invention, either of said two electronic component is a semiconductor device.
A method according to the present invention is a method for making a connection between a first electronic component and a second electronic component, wherein said first electronic component having two metal layers having mutually different coefficients of thermal expansion, and a plurality of side wall pieces that are provided on said metal layers so as to form a connecting space for said second electronic component, said method comprising; a first step of extending an aperture of said connecting space formed by said side wall pieces by applying heat to said two metal layers, a second step of inserting a connection member of said second electronic component into said connecting space, and a third step of narrowing said aperture of said connecting space by cooling said two metal layers.
In the method for connection between an electronic component and a board according to the present invention, the shape of a flip-chip bump formed on an LSI chip or on a board is made so that one end has a depression, with the other end having a pillar shape that mates with a depression. The base part of the depression shape is formed by a two-layer metal structure in which the two layers have different coefficients of thermal expansion, with the upper layer being made of a metal with a large coefficient of thermal expansion and the lower layer being made of a metal with a small coefficient of thermal expansion, so that temperature control can be used to control connection between two electronic components.
By doing the above, it is possible to achieve a flip-chip connection without the need for a fused solder connection, thereby enabling repeated connection and removal of an LSI chip without damage to the electrical connection point. Additionally, because there is no need to use a solder material that inc
Cuneo Kamand
Foley & Lardner
NEC Corporation
Paladini Albert W.
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