Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
2000-05-30
2001-12-25
Copenheaver, Blaine (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S332000, C428S457000, C257S738000, C438S612000, C438S614000, C361S773000
Reexamination Certificate
active
06333104
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the coupling of two electrical devices, and specifically to the coupling of integrated circuit chips to electronic cards using interconnections comprising conductive polymers.
Electrical components such as semiconductor devices and integrated circuit chips are, in general, mounted on a printed circuit board or “card” in order to be electrically connected with other electrical devices. The electrical connection from the first electrical component to the second electrical component is formed between external electrodes or contact pads on the first component to contact pads on the second component. The contact pads on each component are arranged to align with the matching contact pads on the other component.
Various methods for connecting the contact pads on the first component with the contact pads on the other component are known in the art, including use of ball grid arrays (BGAs), column grid arrays (CGAs), and land grid arrays (LGAs). For example, electrically conductive bonds that mechanically and electrically connect the first component and the second component at each pair of matching contact pads can be formed using solder balls. Solder balls are units of essentially sphere-shaped, solidified solder that have been applied to the contact pads of the first component. When all of the desired contact pads on the first component have had a solder ball applied, the component is said to comprise a “ball grid array,” or bump grid array. The ball grid array is placed so as to align each solder ball on the first component with the matching contact pads on the second component.
FIG. 1
a
shows an electrical component with a ball grid array aligned over the substrate of a second component generally at
10
. The first component
12
has a plurality of contact pads
14
, onto each of which is affixed a solder ball
16
. The second component substrate
18
has contact pads
20
aligned in a matching configuration to the first component contact pads
14
.
FIG. 1
b
shows the configuration of the ball grid array after the solder balls
16
in the ball grid array have been placed in contact with the contact pads
20
on the second component substrate
18
. Typically, the first component
12
is positioned in a parallel plane to the second component substrate
18
, and a slight force is applied to the first component
12
to ensure contact between the entire ball grid array and the contact pads
20
on the second component substrate
18
. The ball grid array is then heated, which causes the solder to reflow. The assembly is then allowed to cool. As shown in
FIG. 1
c
, the final assembly comprises soldered interconnections
22
between the contact pads
14
of the first component
12
and the contact pads
20
of the second component substrate
18
.
Conventional ball grid arrays, however, are not sufficiently resistant to interconnection breakage caused by differential expansion of the components. As the distance from the neutral point (where little or no interconnection stress occurs) of an interconnection increases, the reliability of that interconnection diminishes, because greater shear stresses are imparted on the interconnection.
Techniques have been developed to increase the distance between an electrical component and the substrate it is mounted on in order to provide for longer interconnections than can be achieved with a simple ball grid array. For example, multiple layers of solder balls or conductor layers can be used to increase the final distance between the component and the substrate (See, for example, U.S. Pat. No. 5,816,478 to Kaskoun and U.S. Pat. No. 5,641,113 to Somaki et al.). Although such lengthened interconnections are useful for larger substrates, the interconnections cannot be formed close enough to each other on a single substrate to allow use in many applications that require a higher density of interconnections on a component.
Interconnections formed through the various conventional techniques described above produce soldered connections that are prone to malfunction because the interconnections are relatively inflexible and therefore unable to withstand shearing forces created by the differing coefficients of thermal expansion of the materials in the components and interconnections.
What is needed in the art is an interconnection that allows for the ready incorporation of flexible and durable interconnections between the contact pads of two electrical devices.
BRIEF SUMMARY OF THE INVENTION
The above-described and other disadvantages of the prior art are overcome or alleviated by the interconnection of the present invention, which comprises a conductive polymer comprising a polymer component and a conductive component, and a first solderable cap disposed in contact with said conductive polymer.
In another embodiment, the interconnections of the present invention comprises a conductive polymer comprising a polymer component and a conductive component, a first solderable cap disposed in contact with said conductive polymer, and a second solderable cap disposed in contact with said conductive polymer opposite said first solderable cap.
The present invention is also a method for incorporating an interconnection between two electrical components comprising bonding an interconnection on a first contact pad of a first component, wherein said interconnection comprises a conductive polymer comprising a polymer component and a conductive component, and a first solderable cap disposed in contact with said conductive polymer, and then soldering said first solderable cap to a second contact pad of a second component.
The present invention is also a method for incorporating an interconnection between two electrical components comprising soldering a second solderable cap of an interconnection to a first contact pad of a first component, wherein said interconnection comprises a conductive polymer comprising a polymer component and a conductive component, a first solderable cap disposed in contact with said conductive polymer, and said second solderable cap disposed in contact with said conductive polymer opposite said first solderable cap, and then soldering said first solderable cap to a second contact pad of a second component.
The above-described and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.
REFERENCES:
patent: 4997122 (1991-03-01), Zimmer
patent: 5545465 (1996-08-01), Gaynes et al.
patent: 5641113 (1997-06-01), Somaki et al.
patent: 5747101 (1998-05-01), Booth et al.
patent: 5816478 (1998-10-01), Kaskoun et al.
patent: 5854514 (1998-12-01), Roldan et al.
patent: 5925930 (1999-07-01), Farnsworth et al.
Courtney Mark G.
Goldmann Lewis S.
Martin Gregory B.
Perry Charles H.
Cantor & Colburn LLP
Copenheaver Blaine
International Business Machines - Corporation
Paulraj Christopher
Pepper Margaret
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