Chip-mounted contact springs

Details Chip-mounted contact springs Chip-mounted contact springs

2001-11-08

2004-08-17

Zarneda, David A. (Department: 2829)

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

Reexamination Certificate

active

06777963

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the field of integrated circuit technology, and in particular to contact springs for use in an integrated circuit test probe.
2. Description of Related Art
EP 0755071 discloses a test device that comprises an integrated circuit (hereinafter a “probe IC”) with protruding “solder bumps” that are designed to contact pads on a corresponding integrated circuit that is to be tested (hereinafter a “DUT”, Device Under Test), and is incorporated by reference herein. The probe IC preferably contains circuitry to facilitate the testing of the DUT, and the bumps provide the communication of power and test signals and corresponding responses, to and from the DUT. The bumps are fabricated on the probe IC to correspond to the location of test points on the DUT. Because multiple test points must be contacted simultaneously, the protrusion of each bump must be substantially equal, to form a uniform contact plane.
An alternative to the use of solder-bumps is the use of pre-formed balls that are mounted to the planar surface of the probe IC, as illustrated in FIG.
1
. Uniformly sized balls
130
are mounted on a probe IC
120
, which is mounted on a test device substrate
110
. Connections
115
provide communication between the probe IC
120
and other test equipment (not shown), via circuitry on the substrate
110
. If the balls
130
are of uniform size, a uniform contact plane is provided, as illustrated in
FIG. 1
by the dashed line
101
. When the balls
130
are brought in contact with pads
140
on a DUT
150
, via a movement
190
of the test structure that includes the probe IC
120
toward the DUT
150
, or a movement of the DUT
150
toward the probe IC
120
, contact is established, and testing may be performed by communicating test stimuli and responses to and from the DUT
150
. The use of uniform sized balls, however, limits the pitch, or test-pad-density, that can be achieved.
FIG. 2
illustrates another alternative to the solder-bump or uniform-ball contact techniques, wherein spring levers
230
on the probe IC
120
are used to contact the pads
140
of the DUT
150
. Using thin-film microspring technology, a pitch as dense as 6 micrometers can be achieved, compared to an approximate 400 micrometer limit to the aforementioned uniform-ball contact technique. The cost and complexity of fabricating microsprings, however, limits the application of this technique for widespread use. Additionally, the extent of the spring element
230
below the probe IC
120
using microspring technology is limited, and may not provide sufficient clearance between the components of the test structure, such as the connectors
115
between the probe IC
120
and the substrate
110
, and the DUT
120
.
An alternative to the use of microsprings is the use of bonding wire that is treated to be resilient. “THE FINAL TEST REPORT”, Vol. 12, No. 9, Sep. 2001, introduces such a technique developed by FormFactor, Inc. of Livermore, Calif. In this approach, the bonding wire
330
is attached to a bond pad at one end, and formed into an “S” shape to provide a resilient spring, as illustrated in FIG.
3
. The resilient spring shape provides tolerance for a non-uniform contact plane, and can be formed to a length that sufficiently clears the connectors
115
. Consistently forming an S shape with a free-standing bonding wire, however, is a non-standard use of a bonding wire machine, and requires a two-step process. To form the S shape, the bonding wire must be non-resilient; to provide the required resiliency, the resilient coating must be subsequently applied. As multiple springs are formed, maintaining the required shape in the non-resilient bonding wire may be problematic, and the subsequent application of the resilient coating to a field of S shaped bonding wire springs is also likely to be problematic.
BRIEF SUMMARY OF THE INVENTION
It is an object of this invention to provide a method and system that facilitates contact between two integrated circuit devices. It is a further object of this invention to provide a method and system that facilitates the testing of an integrated circuit. It is a further object of this invention to provide a method and system that facilitates contact between two integrated circuits that uses conventional manufacturing processes.
These objects and others are achieved by providing a method and system wherein bonding wire is formed into an inverted “V” shape by bonding both ends of a bonding wire to adjacent points on an integrated circuit. One end of the bonding wire is bonded to a specified point on the integrated circuit, the bonding head is raised, and then lowered to an immediately adjacent point to effect the second bonding, thus forming the inverted V shape. This V shape, being bonded at both ends, is mechanically stable, is resilient in form, and allows for the use of resilient, or non-resilient bonding wire. The vertex of the V shape forms a point or surface for contacting another integrated circuit, or other device, for communicating signals to and from the device to which the bonding wire is bonded.


REFERENCES:
patent: 5441343 (1995-08-01), Pylkki et al.
patent: 6075373 (2000-06-01), Iino
patent: 6169410 (2001-01-01), Grace et al.
patent: 6597187 (2003-07-01), Eldridge et al.
patent: 0 755 071 (1996-07-01), None
(co pending application) “Preconditioned Integrated Circuit for Integrated Circuit Testing”.
“Introducing WOW Technology”, http://www.formfactor.com/about/wow/wow_pg2.html.
“Introducing WOW Technology”, http://www.formfactor.com/about/wow/wow_pg5.html.
“Focus on FormFactor”, The Final Test Report, vol. 12, No. 09, Sep. 2001, Ikonix Corp. P.O. Box 1938, Lafayette, CA 94549-1938.
“Flip-Chip Bonding on 6-um Pitch using Thin-Film Microspring Technology”, Donald L. Smith et al., Xerox Palo Alto Research Center, Proceedings, 48thElectronic Components and Technology Conference, IEEE, May 1998.

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