Temporary interconnect for semiconductor devices

The present invention discloses a bump nest which allows a semiconductor device to be temporarily connected with a package without having to be fused to the package. The disclosed temporary interconnect includes a contact group comprising at least three projecting contact elements. Each of the respective contact elements includes a projecting contact guide, which is concentrically located on an encircling contact. The projecting contact guides and the encircling contact are spaced in a manner so as to surround a ball or a bump of the semiconductor device. In the preferred embodiment, the temporary interconnect may also include a base pad on which each of the encircling contacts is accurately positioned to surround the ball or bump.

FIELD OF THE INVENTION
 The present invention relates generally to interconnection devices, and in
 particular, to a temporary interconnect for a semiconductor device to be
 connected with a package.
 BACKGROUND OF THE INVENTION
 The demand for semiconductor chip packages having high lead counts and
 small footprints has increased. In response to this increase in demand,
 semiconductor manufacturers have developed ball grid arrays, flip-chip,
 and chip scale technology. These semiconductor devices do not use
 traditional wire bonds to mount the devices to a package, rather they are
 mounted to a package using an array of solder balls or similar electrode
 bumps. These semiconductor devices with electrode bumps are generally
 mounted to the packages with the assistance of small pads or traces that
 are located on the packages. Once the semiconductor devices are properly
 aligned and fit together, the devices are heated in a furnace that causes
 the electrode bumps and the traces to fuse together, thereby creating a
 permanent electrical connection.
 A typical ball grid array or pin grid array package contains a
 semiconductor chip that is connected with a substrate and the
 semiconductor chip is wire bonded to electrical traces in the substrate.
 To create the complete package, the semiconductor chip is generally
 encapsulated with a mold material or sealed with a metal lid and the
 electrode bumps are bonded to the electrical traces on the bottom surface
 of the substrate. In a flip-chip package, the solder bumps are attached
 directly to the electrical traces formed in the surface of the chip. The
 flip-chip devices are underfilled with an underfill material to increase
 their reliability, but are not generally encapsulated by a molded
 material. Thus, flip-chip packages are extremely fragile and must be
 handled with great care.
 A chip scale package is a combination of ball grid array packages and of
 flip-chip packages. A chip scale package has electrode bumps that are
 attached directly to electrical traces on the surface of the chip. The
 electrode bumps can also be attached directly to the bond pads through
 openings in the encapsulating material. The electrical traces connect the
 external electrode bumps directly to the bond pads in the chip, thereby
 reducing the size of the overall semiconductor chip.
 The present devices and methods of interconnecting a semiconductor chip
 with a package include the use of some form of electrode bumps and traces.
 As previously stated, in practice, the semiconductor chip is attached to
 the package by reflowing the package together with the semiconductor chip
 in a furnace. A metallurgical bond forms between the semiconductor bumps
 and the package traces creating the desired electrical connection. In
 general, the furnace heats the devices to a predetermined point where the
 electrode bumps and package traces fuse together thereby making a
 permanent electrical connection.
 The problem with these prior art devices and methods of connecting
 semiconductor chips with packages is that the traces that are used on the
 package and the electrode bumps of the semiconductor must be physically
 bonded together. As previously discussed, the devices are physically
 bonded together by heating the two components to the melting point of the
 electrode bumps and package traces. Often, designers, product engineers,
 or wafer process engineers want to remove the semiconductor chip from the
 package after they have been interconnected for failure or performance
 analysis. Other times, product engineers may want to evaluate different
 packages for performance using the same semiconductor chip. Removing the
 semiconductor chip from the package is extremely difficult without
 damaging the semiconductor chip because the electrode bumps and the
 package traces have been fused together during the assembly process. As
 such, a need exists for a temporary interconnect device or bump nest that
 allows easy temporary attachment and removal of semiconductor chips from
 package traces without having to fuse the respective interconnection
 devices together.
 BRIEF SUMMARY OF THE INVENTION
 The present invention discloses temporary interconnection methods and
 devices that allows the semiconductor chip to be temporarily connected
 with the package without having to be fused together. As such, the
 electrode bumps of the semiconductor chip can easily be removed from the
 package for analysis without damaging the semiconductor chip. In preferred
 embodiments, the temporary interconnect is made of gold; however, one
 skilled in the art would recognize that any highly conductive material may
 be used, such as aluminum or copper. The disclosed temporary
 interconnection device can be used in a wide variety of applications in
 the electronic industry.
 The disclosed temporary interconnect includes a contact group comprising a
 plurality of contact elements, spaced to provide at lease one conductive
 interfaces with an electrode bump of a semiconductor chip. Each of the
 contact elements can include an encircling contact pad and a projecting
 contact guide. In the preferred embodiment, the contact elements are
 concentrically located on a base pad. The projecting contact guides and
 the encircling contact are spaced in a manner on the base pad so as to
 surround the electrode bump of the semiconductor chip and provide an
 electrical connection with the package.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 As illustrated in FIG. 1, the present invention discloses a temporary
 interconnect 10 which gives engineers the ability to temporarily
 interconnect a bumped semiconductor device 12 with a package 14. In the
 invention, a contact group 16 (see FIG. 2) is provided which includes at
 least three contact elements 18, 20 and 22. Each of the respective contact
 elements 18, 20, and 22 includes an encircling contact 24 and a projecting
 contact guide 26. As depicted in FIGS. 1 and 2, the contact elements 18,
 20 and 22 are spaced in such a manner so that each of the respective
 projecting contact guides 26 surround an electrode bump 28 of the bumped
 semiconductor device 12.
 As disclosed in FIGS. 1 and 2, the temporary interconnect 10 may include a
 base pad 30 which is connected with the contact group 16. In the preferred
 embodiment, the contact group 16 is positioned on the base pad 30 about a
 central axis 32 of the base pad 30. However, one skilled in the art would
 recognize that the contact group 16 may be located in any manner which
 allows the projecting contact guides 26 to effectively engage the
 electrode bump 28 of a semiconductor device 12 which is to be temporarily
 interconnected with the package 14. In addition, the package 14 may be
 manufactured in such a manner that a plurality of contact groups 16 may be
 placed directly on the conductor traces of the package 14, thereby
 allowing the package traces to act as the base pad 30. However, in the
 disclosed preferred embodiment, the contact group 16 is located on the
 base pad 30 which may then be connected with the traces on the package 14.
 The contact elements 18, 20 and 22 can be optimally positioned and sized to
 electrically connect the electrode bump 28 of the semiconductor device 12
 with the package 14. The package 14 depicted in FIG. 1 is by way of
 example only and is not in any way meant as a limitation of the disclosed
 invention. Those skilled in the art would recognize that the disclosed
 temporary interconnect 10 can be used in any electronic application where
 a need exists for a device that will temporarily interconnect a bumped
 semiconductor device 12 with a second electronic circuit or device, such
 as that depicted herein as package 14. By using the disclosed invention,
 engineers will no longer need to heat the devices in a furnace, thereby
 fusing the components together to make the electrical connection between
 the devices.
 In the disclosed preferred embodiment, each of the respective projecting
 contact guides 26 of the contact elements 18, 20 and 22 is generally cone
 shaped. In addition, each of the encircling contacts 24 is formed in a
 toroidal shape having upper and lower surfaces. The projecting contact
 guides 26 are integrally formed with the upper surface of each encircling
 contact 24. It should be recognized that the general shape of the
 projecting contact guides 26 may vary, but they will always be shaped in a
 manner that allows the contact elements 18, 20 and 22 to provide at least
 one engaging conductive interface with the bump 28 of the semiconductor
 device 12, and a surrounding arrangement of conically shaped guides 26 can
 guide and surround the bump 28 and provide a plurality of engaging
 electrical connections with the bump.
 As previously discussed, the disclosed temporary interconnect 10 may
 include a base pad 30 that is connected with the contact group 12. As
 illustrated best in FIG. 2, the contact group 16 is preferentially
 positioned circumferentially around the base pad 28, each of the plurality
 of projecting contact guides 26 thereby being spaced at an equal distance
 from a central axis 32 of the base pad 30. In addition, the contact group
 16 is arranged in the preferred embodiment so that the ends of the
 projecting contact guides 26 create an equilibrium triangle having the
 central axis 32 of the base pad 30 as the center of the triangle. As
 previously stated, one skilled in the art would recognize that the contact
 group 16 could be mounted directly to the traces of the package 14 using
 the temporary interconnect 10 without the need of a base pad 30. The
 traces of the package 14 could serve the same function as the base pad 30.
 Most packages 14 that might be used in conjunction with the present
 invention will have some form of traces that could be substituted for the
 base pad 30. However, preferentially, each temporary interconnect 10 will
 include the base pad 30 which in turn will be mounted to the traces on the
 package 14.
 Referring to FIG. 3, the present invention further discloses a method of
 temporarily interconnecting a semiconductor device 40 having a plurality
 of bumps 42 with a package 44. In the disclosed method, at least one
 temporary interconnect 46 is provided which has at least three contact
 elements 18, 20 and 22 (see FIG. 2). As previously set forth, each of the
 contact elements 18, 20 and 22 includes an integral projecting contact
 guide 48 that is preferentially located on an encircling contact 50. The
 contact elements 18, 20 and 22 are spaced to surround a respective contact
 42 of the semiconductor device 40 thereby providing an electrical
 connection with each of the respective bumps 42.
 Those skilled in the art would recognize that most packages 44 have a
 plurality of package traces 52 to which a plurality of temporary
 interconnects 46 may be connected to establish an electrical connection
 between the semiconductor device 40 and the package 44. As previously
 discussed, the contact elements 18, 20 and 22 (see FIG. 2) could be
 mounted directly to the package traces 52 or each respective temporary
 interconnect 46 could be provided with a base pad 30 which is connected
 with the package 44, as illustrated in FIGS. 1 and 2. In the preferred
 method, the plurality of bumps 42 of the semiconductor device 40 is
 accurately positioned for temporary electrical engagement with a
 respective one of the plurality of temporary interconnects 46.
 While the invention has been described in its currently best known modes of
 operation and embodiments, other modes and embodiments of the present
 invention will be apparent to those skilled in the art. The invention is
 only limited by the claims that follow.