U.S. patent application number 11/528137 was filed with the patent office on 2007-01-25 for method of making an interposer with contact structures.
Invention is credited to Salman Akram, James M. Wark.
Application Number | 20070017093 11/528137 |
Document ID | / |
Family ID | 22017747 |
Filed Date | 2007-01-25 |
United States Patent
Application |
20070017093 |
Kind Code |
A1 |
Wark; James M. ; et
al. |
January 25, 2007 |
Method of making an interposer with contact structures
Abstract
A method of making an interposer having an array of contact
structures for making temporary electrical contact with the leads
of a chip package. The contact structures may make contact with the
leads as close as desired to the body of the chip package.
Moreover, the contact structures can be adapted for making contact
with leads having a very fine pitch. In one embodiment, the contact
structures include raised members formed over a body of the
interposer. A conductive layer is formed over each of the raised
members to provide a contact surface for engaging the leads of the
chip package. In another embodiment, the raised members are
replaced with depressions formed into the interposer. A conductive
layer is formed on an inside surface of each depression to provide
a contact surface for engaging the leads of the chip package. Any
combination of raised members and depressions may be used.
Inventors: |
Wark; James M.; (Boise,
ID) ; Akram; Salman; (Boise, ID) |
Correspondence
Address: |
TRASK BRITT
P.O. BOX 2550
SALT LAKE CITY
UT
84110
US
|
Family ID: |
22017747 |
Appl. No.: |
11/528137 |
Filed: |
September 27, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10956804 |
Oct 1, 2004 |
|
|
|
11528137 |
Sep 27, 2006 |
|
|
|
10365874 |
Feb 13, 2003 |
|
|
|
10956804 |
Oct 1, 2004 |
|
|
|
09631253 |
Aug 2, 2000 |
6782613 |
|
|
10365874 |
Feb 13, 2003 |
|
|
|
09058586 |
Apr 10, 1998 |
6299456 |
|
|
09631253 |
Aug 2, 2000 |
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Current U.S.
Class: |
29/857 ; 29/860;
29/884 |
Current CPC
Class: |
Y10T 29/49222 20150115;
Y10T 29/49124 20150115; H01L 2924/00 20130101; H01R 12/57 20130101;
H01R 43/205 20130101; Y10T 29/49453 20150115; H05K 2201/10689
20130101; H01L 2924/0002 20130101; H01L 2924/0002 20130101; G01R
1/0466 20130101; G01R 1/0408 20130101; H05K 2201/09472 20130101;
Y10T 29/49123 20150115; Y10T 29/49179 20150115; H05K 3/326
20130101; H05K 3/4007 20130101; Y10T 29/49155 20150115; H05K
2201/0133 20130101; H05K 2201/09045 20130101; H05K 2201/0367
20130101; Y10T 29/49147 20150115; Y10T 29/49126 20150115; Y10T
29/49174 20150115; H05K 3/325 20130101; H05K 1/119 20130101; H05K
2201/0373 20130101; Y10T 29/49117 20150115; Y10T 29/49165
20150115 |
Class at
Publication: |
029/857 ;
029/860; 029/884 |
International
Class: |
H01R 43/00 20060101
H01R043/00 |
Claims
1. A method of making an interposer structure for providing
electrical communication between an array of electrical leads of an
integrated circuit and external circuitry, the method comprising:
providing a substrate including a dielectric material; and forming
an array of contact structures on said substrate, said array of
contact structures being sized and spaced so as to be capable of
electrically engaging said array of electrical leads, wherein each
of said contact structures is formed by: forming a depression into
said substrate, said depression having an inside surface defined
thereon; forming a conductive layer disposed over at least a
portion of said inside surface of said depression; forming an
electrical trace disposed over a surface of said substrate; and
electrically connecting said electrical trace with said conductive
layer, wherein said electrical trace comprises a conductive
material so as to provide electrical communication between said
conductive layer and said external circuitry.
2. The method of claim 1, wherein the substrate comprises a
silicon-containing material.
3. The method of claim 1, further comprising forming an array of
terminal contact points in electrical communication with said array
of contact structures, wherein: said array of contact structures
has a first pitch; and said array of terminal contact points has a
second pitch that is greater than said first pitch.
4. The method of claim 3, wherein: said array of terminal contact
points is in electrical communication with said array of contact
structures by conductive members selected from the group consisting
of conductive tape, wirebonded leads, and non-bonded leads; and
said conductive members are positioned in electrical contact with
said electrical traces.
5. The method of claim 1, wherein forming the depression into the
substrate comprises conducting an etching operation on the
substrate.
6. The method of claim 1, wherein the conductive layer comprises a
material selected from the group consisting of titanium, tungsten,
beryllium, copper, gold, palladium, combinations thereof, and
alloys thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of application Ser. No.
10/956,804, filed Oct. 1, 2004, pending, which is a divisional of
application Ser. No. 10/365,874, filed on Feb. 13, 2003, pending,
which is a divisional of application Ser. No. 09/631,253, filed on
Aug. 2, 2000, now U.S. Pat. No. 6,782,613, issued Aug. 31, 2004,
which is a divisional of application Ser. No. 09/058,586, filed
Apr. 10, 1998, now U.S. Pat. No. 6,299,456, which are incorporated
herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. The Field of the Invention
[0003] The present invention relates to structures for electrically
connecting an integrated circuit to external circuitry. More
particularly, the present invention relates to interposer
structures having formed thereon a plurality of conductive pillars
or recesses adapted to make electrical contact with the leads of an
integrated circuit package.
[0004] 2. The Relevant Technology
[0005] Frequently, after an integrated circuit is manufactured, a
testing process is conducted on the integrated circuit by
subjecting it to a preselected set of input conditions in order to
measure its response or other parameters. Such testing is often
conducted on a chip package that includes an integrated circuit. As
used herein, the terms "integrated circuit package" and "chip
package" refer to an assembly that includes an integrated circuit
or another semiconductor structure in combination with external and
additional structure. The term "semiconductor structure" extends to
any device or assembly that includes circuitry defined in a
semiconductive material, and further extends to a chip package that
includes semiconductive material. The external and additional
structure of a package assembly may be used, for example, for
mounting the semiconductor structure to a printed circuit board or
other external circuitry, for establishing electrical connection
between the semiconductor structure and external circuitry, for
improving the ease of handling or transporting the semiconductor
structure, and/or for protecting the semiconductor structure from
environmental conditions.
[0006] Many chip packages include a lead frame that extends beyond
the body thereof. The lead frame typically includes an array of
electrical leads that extend from the internal circuitry of the
integrated circuit to the exterior portion of the chip package
where they are exposed to the surroundings. Testing of an
integrated circuit package that includes a lead frame assembly is
conventionally conducted by providing temporary electrical
communication between the leads and testing circuitry. For example,
such temporary electrical connection may be established by using a
set of probes, pins, sockets, or the like, to contact the leads.
The integrated circuit package may be clamped or otherwise secured
in position during the testing operation in order for the leads to
remain in electrical contact with the corresponding probes, pins,
sockets, etc., of the testing circuitry.
[0007] Regardless of which electrical connection technique is
employed, it is desirable to effect a connection that causes as
little damage as possible to be leads. If the temporary connection
to contact surfaces damages the leads, the entire integrated
circuit package may be rendered useless.
[0008] The trend in the semiconductor manufacturing industry is
towards smaller devices and an increase in the number of leads
connected to an integrated circuit package. This has the result of
reducing the distance between nearest leads on an integrated
circuit package. In particular, the pitch of leads, which is
defined as the distance between corresponding points on nearest
adjacent leads, has progressively grown smaller.
[0009] As the pitch of integrated circuit packages decreases, it
becomes ever more difficult to effectively and reliably establish
temporary electrical contact with the leads without damaging the
leads. The difficulties are compounded in light of the fact that
testing is generally more reliable when electrical contact is made
with leads as near to the body of the integrated circuit package as
possible. If contact is instead made with the leads a relatively
large distance from the body of the integrated circuit package, the
resulting long conductive segments of the leads can generate
considerable interference and noise which may disrupt the testing
procedure.
[0010] Establishing electrical connection with leads near the body
of the integrated circuit package is further desirable as
integrated circuits operate at ever higher speeds. If electrical
connection is established at a relatively great distance from the
body of a high-speed integrated circuit package, signals are not
able to be received and transmitted at the proper synchronization
or at the proper timing, which may cause the integrated circuit to
malfunction or the testing procedure to become disrupted.
[0011] It can be easily understood that the factors that encourage
electrical connection to be established relatively near the body of
the integrated circuit package are often in conflict with efforts
for making contact with conventional fine pitch lead frames. The
probes, sockets and the like that have been used in the prior art
are often not able to adequately balance these considerations and
increasingly are unable to provide reliable electrical connection
for conducting testing procedures.
[0012] Accordingly, it can be appreciated that it would be an
advancement in the art to provide an interconnect structure that
can provide electrical connection with leads near the body of an
integrated circuit package, particularly when the leads have a
relatively fine pitch.
SUMMARY OF THE INVENTION
[0013] The present invention relates to interposer structures that
include a plurality of contact structures formed thereon in a
pattern that corresponds to electrical leads of an integrated
circuit package. The contact structures are arrayed across a
surface of the interposer structure in a position so as to make
electrical connection with the leads of an integrated circuit
package when the integrated circuit package is positioned
thereover. The contact structures include a conductive layer for
electrically engaging the leads and an electrical trace having a
first end in contact with the conductive layer and an opposite
second end configured to be connected with another conductive
structure. For example, wire bonded leads, conductive tape or
non-bonded leads may be connected with the second end of the
traces. These wires or leads in turn terminate at terminal contact
points that preferably have a pitch greater than the pitch of the
leads of the integrated circuit package. In this manner, relatively
fine pitch leads can be connected to conventional sockets or other
mounting structures on a testing device that have a greater pitch
by means of the interposer structure.
[0014] The interposer structures of the invention include a
dielectric or a semiconductor substrate over which the contact
structures may be formed. The semiconductor substrate is preferably
substantially composed of silicon or a silicon-containing material.
Alternatively, a dielectric substrate can be formed over a
semiconductor substrate. The dielectric substrate may be disposed
over a body portion of the interposer structure or may instead be
an integral portion of the interposer structure.
[0015] Under a first embodiment of the invention, an array of
raised members is formed on the dielectric or semiconductor
substrate, with each raised member having a top surface distal to
the dielectric or semiconductor substrate. A conductive layer is
deposited or otherwise formed on the top surface of each of the
raised members. The raised members are sized and spaced so that the
conductive layers formed thereover may electrically engage the
leads of an integrated circuit package. The raised members may be
formed from the dielectric or semiconductor substrate using any
suitable etching procedure or other micromachining operation.
Silicon or silicon-containing material is a preferred material for
use in the dielectric or semiconductor substrate because such
material is relatively easy to pattern to form the raised members,
as well as being scalable to relatively smaller geometries and
compared to other materials used in etching procedures or
micromachining operations.
[0016] Optionally, one or more projecting apex structures are
formed in the top surface of the raised member, upon which is
positioned the conductive layer opposite the top surface of the
raised member. The projecting apex structures facilitate the
establishment of ohmic contact with the leads by penetrating the
surface of the leads, including any oxide layer that may have been
formed thereon.
[0017] According to a second embodiment of the invention, an
interposer is provided, wherein the raised members are replaced
with an array of depressions formed into the dielectric or
semiconductor substrate. A conductive layer is deposited or
otherwise formed on an inside surface of each of the depressions.
The depressions are aligned and spaced so that the leads of an
integrated circuit package may be placed therein and become
electrically engaged with the conductive layers. For example, the
depressions may take the form of trenches, each having a
longitudinal axis parallel to the longitudinal axis of the
corresponding lead. The trenches or other depressions may have one
end that is open into a nest or other low elevation region on the
face of the interposer structure. The nest may facilitate placement
of the leads into the depressions by allowing the integrated
circuit package to rest low on the interposer and near to the plane
defined by the array of depressions.
[0018] According to either of the foregoing embodiments, electrical
traces preferably extend from the conductive layer along a surface
of the body of the interposer structure. The traces preferably have
a contact pad at one end thereof where a conductive structure such
as a wire or conductive tape may be attached. Any suitable
conductive structure may be used to electrically connect the trace
with external circuitry, such as that found in a testing apparatus.
For example, conductive tape may be attached to the leads to
provide an electrical path to the testing device. According to a
preferred configuration of the interposer structure, the conductive
tape wraps around an edge of the interposer structure and extends
to a face of the interposer structure opposite the contact
structures. The conductive tape may end at a terminal contact point
that can be connected to a conventional socket or probe.
Preferably, the terminal contact points on the conductive tape are
not aligned across the surface of interposer structure, but are
instead staggered, thereby increasing the distance between adjacent
terminal contact points and increasing the pitch.
[0019] When an integrated circuit package is electrically connected
to the interposer structure, the integrated circuit package may
advantageously be secured thereover in order to reliably establish
electrical connection. This can be accomplished by any of a number
of suitable methods. For example, a clamping apparatus may be
brought into contact with the leads or with another part of the
integrated circuit package. The clamping apparatus may be a bar or
a plate that is pressed onto the integrated circuit package on the
opposite side thereof from the interposer structure. Alternatively,
a vacuum source may be connected to a via that extends through the
interposer structure and terminates at an end that is adjacent a
portion of the body of the integrated circuit package. Using the
vacuum source, the integrated circuit package may be held onto the
interposer structure by differences in air pressure. In any case,
when the interposer structure is used for testing an integrated
circuit, the method of securing the integrated circuit package onto
the interposer structure is preferably temporary.
[0020] According to still another embodiment of the invention, the
raised members and depressions of the previous embodiments are
replaced with an array of conductive bumps. The interposer
structure of this embodiment includes a substrate over which a
plurality of segments of conductive tape is positioned. A
conductive bump is deposited over each segment of conductive tape
in order to provide contact surfaces for electrically engaging the
leads of the integrated circuit package.
[0021] In view of the foregoing, the interposer structures of the
invention are able to establish electrical connection to leads
relatively near the body of an integrated circuit package. This is
possible even in situations where the leads have a very fine pitch.
Moreover, reliable temporary electrical contact with leads can be
established without damaging the leads.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to illustrate the manner in which the above-recited
and other advantages of the invention are obtained, a more
particular description of the invention briefly described above
will be rendered by reference to specific embodiments thereof which
are illustrated in the appended drawings. Understanding that these
drawings depict only typical embodiments of the invention and are
therefore not to be considered limiting of its scope, the invention
will be described with additional specificity and detail through
the use of the accompanying drawings in which:
[0023] FIG. 1 is a top view of an interposer structure including an
array of contact structures according to a first embodiment of the
invention.
[0024] FIG. 2 is a top view of an integrated circuit package having
an array of electrical leads that correspond to the array of
contact structures of FIG. 1.
[0025] FIG. 3 is a bottom view of the interposer of FIG. 1. An
array of terminal contact points are arranged on segments of
conductive tape.
[0026] FIG. 4 is a partial cross-sectional elevation view of an
electrical contact assembly including an integrated circuit package
disposed over the interposer structure of FIG. 1. An electrical
lead of the integrated circuit package is placed in electrical
communication with external circuitry.
[0027] FIG. 5 is a partial cross-sectional elevation view of an
alternative configuration of an electrical contact assembly.
[0028] FIG. 6 is an exploded perspective view of a replaceable
module that includes a plurality of contact structures and may be
fitted onto a substrate of an interposer structure.
[0029] FIG. 7 is a perspective view of alternative conductive
structures for electrically connecting traces with external
circuitry.
[0030] FIG. 8 is perspective view of a contact structure including
a raised member and a conductive layer having a plurality of
projecting apex structures.
[0031] FIG. 9 is a partial perspective view of an interposer
structure according to a further embodiment of the invention,
wherein the contact structures on the interposer structure include
depressions formed into a substrate.
[0032] FIG. 10 is a partial cross-sectional elevation view of an
electrical contact assembly, including an integrated circuit
package electrically connected to the interposer structure of FIG.
9.
[0033] FIG. 11 is a cross-sectional elevation view of an interposer
structure having a plurality of contact structures that include
both raised members and depressions.
[0034] FIG. 12 is a partial cross-sectional elevation view of an
electrical contact structure wherein the interposer structure
includes a segment of conductive tape and a conductive bump formed
on the conductive tape according to another embodiment of the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0035] The present invention relates to interposer structures that
may be used for establishing electrical connection between an
integrated circuit and external circuitry. The interposer
structures are useful for making electrical contact with electrical
leads of an integrated circuit package relatively near the body of
the integrated circuit package. The interposer structures include
an array of contact structures sized and spaced so as to correspond
to the leads of the integrated circuit package. The contact
structures may be formed on the interposer with a pitch small
enough to accommodate the leads of substantially any integrated
circuit.
[0036] The interposers of the invention provide electrical paths
from the contact structures to terminal contact points that may
have a pitch greater than the pitch of the leads. Accordingly, the
interposers may be used to connect an integrated circuit having
relatively fine pitch with a conventional socket assembly that has
a larger pitch. According to the invention, the contact structures
may take any of a number of forms, including, but not limited to,
raised members formed over a substrate, depressions formed into the
substrate, conductive bumps formed over conductive tape, and
combinations of the foregoing.
[0037] FIG. 1 illustrates an interposer 10 according to the
invention. Interposer 10 preferably includes a body 12 on which
other portions of interposer 10 are formed. Preferably, body 12 is
formed by etching a material, such as silicon. The etching process
stops once body 12 assumes a desired shape. Then, a dielectric
material is formed thereon so as to isolate, one from another, the
discrete conductive components formed by the etching process.
Silicon is a preferred material for body 12 because of the relative
ease at which it may be etched or otherwise micromachined.
Alternatively, body 12 may be composed of other materials,
including, but not limited to, ceramics, polymers, composites, and
the like. Preferably, body 12 is formed from a material that is
rigid enough to resist significant bending and deformation during
normal use and that has a coefficient of thermal expansion
relatively close to that of the integrated circuit and the
conductive material that are to be disposed thereover.
[0038] Preferably, a nest 14 is formed into one face of body 12 as
seen in FIG. 1. Nest 14 may be useful for centering an integrated
circuit package over body 12 and at least partially restraining
lateral movement of the integrated circuit package. Nest 14 may
take the form of a shallow depression or surface that has a lower
elevation than the surrounding portions of body 12. A plurality of
contact structures 16 is arrayed over a face of body 12 in order to
provide a conductive path between the leads of an integrated
circuit package and external circuitry. Accordingly, contact
structures 16 include a contact surface 18 that is positioned to
electrically engage leads when the integrated circuit package is in
position over interposer 10. Contact structures 16 are positioned
over body 12 so as to have a pitch P.sub.1. The pitch of an array
of contact structures is defined herein as the distance between a
point on one contact structure and the corresponding point on the
nearest adjacent contact structure.
[0039] FIG. 2 depicts one example of an integrated circuit package
20 that may be used in combination with interposer 10 of FIG. 1.
Integrated circuit package 20 includes a body 22 that substantially
encases an integrated circuit assembly such as a semiconductor die.
Body 22 is constructed of, for example, a resin or polymeric
material that insulates the semiconductor die and protects it from
environmental conditions. Accordingly, the semiconductor die is not
visible in FIG. 2.
[0040] The semiconductor die is attached to a lead frame which
includes an array of leads 24. The leads 24 emerge from body 22 and
are therefore at least partially exposed to the surroundings.
Accordingly, leads 24 allow signals or power to be supplied to the
internal circuitry of the integrated circuit. As seen in FIG. 2,
the leads have a pitch P.sub.2 that is defined as the distance
between a point on one lead and the corresponding point on the
nearest adjacent lead. It can be understood that if the contact
surfaces 18 are to be placed in contact with leads 24, pitch
P.sub.1 of contact structures 16 should be substantially equal to
pitch P.sub.2 of leads 24. Integrated circuit package 20 has leads
24 that emerge from body 22 at two of four edges thereof. Other
integrated circuit packages are configured differently, and have
leads on as few as one edge or as many as all edges thereof.
[0041] While the embodiments disclosed herein are generally
discussed in reference to their use with integrated circuit
packages, it should be understood that the invention extends to any
other chip packages and other semiconductor structures that may be
temporarily connected to external circuitry. The specific
configuration, dimensions, and composition of the semiconductor
structures and their accompanying leads are not critical to the
invention. Indeed, the interposers of the invention may be adapted
for use with substantially any array of leads of a chip package or
semiconductor structure.
[0042] FIG. 3 illustrates the interposer 10 of FIG. 1 as viewed
from the opposite side as the view of FIG. 1. In this embodiment of
the interposer, segments of conductive tape 26 extend from
respective contact structures 16 seen in FIG. 1, wrap around the
edges of interposer 10, and terminate on bottom face 28 seen in
FIG. 3. A terminal contact point 30, which is a site that can be
connected to conventional sockets, probes, pins, or the like of a
testing device or other external circuitry, is formed on each
segment of conductive tape 26.
[0043] The terminal contact points 30 are preferably arranged in a
staggered formation across bottom face 28. One example of a
staggered formation is seen in FIG. 3, and provides that the pitch
P.sub.3 of terminal contact points 30 is greater than pitch P.sub.1
of contact structures 16. Of course, terminal contact points 30 may
be arranged on interposer 10 according to patterns other than that
depicted in FIG. 3. Staggering the terminal contact points across a
face of the interposer or at another location can result in a pitch
of the terminal contact points that may be at least two to three
times greater than the pitch of the contact structures. Another
factor that may contribute to the increase in pitch is that the
leads 24 may diverge as seen in FIG. 1 as they extend across body
12 and away from contact surfaces 18.
[0044] FIG. 4 depicts an electrical contact assembly in which an
integrated circuit package is electrically connected to external
circuitry using interposer 10 of FIG. 1. Contact structure 16 is
formed over body 12 and includes raised member 32 that extends away
from body 12. Preferably, raised member 32 is at least partially
composed of a dielectric material and projects away from body 12 to
terminate at a top surface 34. Accordingly, contact structure 16 is
a protruding contact structure. Raised member 32 preferably
includes silicon or a silicon-containing material and may be formed
from the same material as body 12. Indeed, raised member 32 may be
integrally formed as a part of body 12. A conductive layer 36 is
deposited or otherwise formed over top surface 34 of raised member
32. Accordingly, conductive layer 36 is in a position to
electrically engage lead 24 when integrated circuit package 20 is
positioned over interposer 10.
[0045] Conductive layer 36 includes a conductive material that
preferably is durable, has good electrical properties, and can
repeatedly make contact with a lead without being significantly
worn or eroded. Examples of suitable conductive materials include,
but are not limited to, titanium, titanium silicide, beryllium,
copper, tungsten, gold, palladium, and alloys or combinations of
the foregoing.
[0046] A trace 38 preferably extends from conductive layer 36 over
a surface of body 12 and/or raised member 32. Trace 38 has an end
40 that is adapted to be connected with a conductive structure such
as a wire bonded lead, conductive tape, a non-bonded lead, or the
like. Trace 38 may comprise the same conductive material as
conductive layer 36 and may simply be an extension of conductive
layer 36.
[0047] In the example illustrated in FIG. 4, a segment of
conductive tape 26 adheres to end 40 of trace 38. Conductive tape
26 wraps around an edge of body 12 and extends to bottom face 28.
In this manner, a terminal contact point 30 may be positioned on
conductive tape 26 at a location where it may be connected to a
probe 42 or another contact pad on testing device 44 or any other
compatible contact point on another external circuitry device.
Because conductive tape is conventionally composed of a polymeric
substrate and a conductive strip formed on one or both faces
thereof, a via 46 or another conductive path may need to be formed
through or around conductive tape 26 to access the conductive
strip.
[0048] In the embodiment of FIG. 4 and other embodiments of the
invention, the conductive structures that provide a conductive path
between the leads of the integrated circuit package and external
circuitry are preferably selected to have matched or uniform
impedance properties. For example, it is advantageous to use
conductive tape 26, traces 38, and conductive layers 36 that have
substantially uniform impedance properties when compared one to
another. Matched impedance may reduce the noise and other
interference that may be otherwise produced during the testing
operation, and may further allow reliable transmission of signals
between the testing circuitry and the integrated circuit, which
becomes more important as higher-speed integrated circuits are
used. For the foregoing reasons, conductive tape is particularly
useful in the present invention.
[0049] Using the contact structures 16 of this embodiment and other
embodiments of the invention, electrical connection may be
established with leads 24 substantially as near to body 22 as
desired. The distance from body 22 at which electrical connections
are preferably established is determined by the properties of
integrated circuit package 20 and the desired results. However, in
many cases, contact can be made with leads 24 as near as a distance
of about 25 microns from body 22 using this or other embodiments of
the invention. The dimensional precision of the silicon substrate
can be plus or minus one (1) micron. Preferably, the determining
factor, however, will be the tolerance and variation of the
corresponding semiconductor package, which is typically plus or
minus two (2) mils (plus or minus fifty (50) microns).
[0050] When an integrated circuit package 20 is disposed over
interposer 10, there may need to be an apparatus for securing the
integrated circuit package 20 in position. In FIG. 4, this is
accomplished by means of a clamping apparatus 48 that is brought
down on lead 24 on a side thereof opposite conductive layer 36.
Alternatively, clamping apparatus 48 may be placed in contact with
body 22 or one of any number of other mechanisms may be used to
secure integrated circuit package 20 in position. In some cases,
adequate electrical contact may be established and maintained
without the assistance of a clamping apparatus or other device that
performs the same function.
[0051] FIG. 5 shows an electrical contact assembly similar to that
of FIG. 4 wherein the terminal contact points 30 are located at a
position separate from the interposer. In this case, terminal
contact points 30 are not positioned on bottom face 28 of
interposer 10 but are instead located on a distal end of the
segment of conductive tape 26. According to the embodiment of FIG.
5, the segments of conductive tape 26 extend away from body 12.
This configuration is best used when leads 24 do not remain
coplanar with body 12 but instead curve away therefrom, as seen in
FIG. 5. This curvature of leads 24 provides clearance in which the
segments of conductive tape 26 may fan out away from body 12
instead of being wrapped around the edges thereof. The segments of
conductive tape 26 or other conductive structures connected to
traces 38 need not be formed as seen in FIG. 5, but instead may
extend in substantially any direction as desired. In other
respects, the electrical contact assembly of FIG. 5 may be similar
to that of FIG. 4. FIG. 5 also illustrates the manner in which
raised member 32 may be integrally formed from body 12.
[0052] As seen in FIG. 6, a group of contact structures 16 may
optionally be formed on an insert module 50, which may be removably
attached to body 12 of an interposer. For example, insert module 50
supports a plurality of contact structures 16 that are disposed
over a surface thereof. Insert module 50 may be snap fitted, press
fitted, or otherwise removably attached to a mating cavity 52 of
body 12. Insert modules 50 may be used so that contact structures
16 may be easily replaced when one or more are damaged, instead of
having to replace the entire interposer. If insert modules 50 are
used with the interposer, one or more insert modules may be used to
contact the leads of each edge of the integrated circuit
package.
[0053] FIG. 7 is a partial perspective view of an edge portion of
an interposer structure showing part of several traces 38, and
further illustrates three examples of methods for electrically
connecting conductive structures to traces 38. While three
different conductive structures or conductive members are depicted
in FIG. 7, it should be understood that generally only one of these
three or another suitable conductive structure is selected for any
given interposer. However, three alternative methods are presented
here for purposes of illustration.
[0054] The first method involves soldering or otherwise permanently
bonding a wire-bonded lead 54 to trace 38. In the second method,
conductive tape 26 is attached to trace 38. Conductive tape 26 may
include a polymeric substrate 56 which may be a polyimide or other
suitable material coated on one or both sides by a conductive strip
58. For example, conductive tape 26 may be tape automated bonding
(TAB) type conductive tape. Typically, conductive tape 26 is
flexible to the extent that it can be bent and wrapped around
corners. The third illustrated method involves placing non-bonded
lead 60 in contact with trace 38 without forming apermanent bond.
In general, the foregoing three examples of conductive structures
are understood by persons of ordinary skill in the art. Other means
for electrically connecting traces 38 with external circuitry are
certainly within the scope of the invention.
[0055] FIG. 8 is an enlarged view of a preferred contact structure
16. In particular, it can be seen that conductive layer 36 is
preferably relatively thin compared to the dimensions of raised
member 32. Optionally, conductive layer 36 will be formed over one
or more projecting apex structures 62 positioned thereon on a
contact surface 64 of top surface 34 of raised member 32.
Preferably, apex structures 62 are first formed in raised member
32, such as when raised member 32 is integrally formed from body
12, and can be formed by an etching process. Then, conductive layer
36 is evenly deposited over apex structures 62.
[0056] When included in contact structure 16, the projecting apex
structures 62 facilitate the formation of an ohmic contact with a
lead. For example, projecting apex structures 62 may slightly cut
into the leads and penetrate any oxide layer that might have been
formed thereon. A preferred method for forming projecting apex
structures 62 is disclosed in U.S. Pat. No. 5,483,741 issued to
Akram et al. which is incorporated herein by reference for purposes
of disclosure. Projecting apex structures 62 may also act to
securely position an integrated circuit package in place by at
least partially restraining lateral motion thereof.
[0057] An alternative embodiment of the invention is illustrated in
FIG. 9 which is a partial perspective view of an edge portion of an
interposer structure 110. In this embodiment, the contact
structures 116 do not include raised members, but instead comprise
depressions 132 formed into a substrate by any suitable method. For
example, if body 122 consists of silicon or a silicon-containing
material, depressions 132 may be formed therein by etching or
another micromachining operation. Accordingly, contact structures
116 are receding contact structures.
[0058] A conductive layer 136 is preferably formed on an inside
surface of depression 132. In the embodiment of FIG. 9, this inside
surface is substantially coextensive with the bottom of depression
132. A trace 138 preferably extends from conductive layer 136 and
has an end 140 that can be connected with conductive structures or
other external circuitry. The materials used in conductive layers
136 and traces 138 may be the same as conductive layers 36 and
traces 38 of FIG. 4.
[0059] While a variety of dimensions and configurations of
depression 132 may be used, the primary factor for their selection
is the dimensions of the leads that are to be disposed in
depressions 132. Typically, depressions 132 have an end that is
adjacent to a nest 114 so as to provide an unobstructed opening by
which leads may be disposed in depressions 132.
[0060] FIG. 10 illustrates an electrical contact assembly wherein
leads 124 of an integrated circuit package 120 are connected to
contact structures 116 of an interposer 110. It can be seen that
electrical contact may be established with leads 124 at a location
thereon as near as desired to body 122 of the integrated circuit
package 120. As in the previous embodiment, integrated circuit
package 120 is preferably mechanically held in place over
interposer 110 such that electrical contact with leads 124 is
maintained. Securing integrated circuit package 120 in place may be
accomplished by means of a clamping apparatus as depicted in FIG.
4. In this case, a clamping apparatus having an array of
castellations that correspond to depressions 132 may need to be
used in order to make adequate contact with leads 124.
Alternatively, air pressure may be used to hold integrated circuit
package 120 in place. As seen in FIG. 10, a vacuum via 166 may be
formed through interposer 110 to terminate at a surface of body
122. A vacuum source (not shown) may be connected to vacuum via
166, thereby producing reduced pressure therein relative to the
ambient air pressure. The resulting vacuum holds integrated circuit
package 120 in place over interposer 110.
[0061] The embodiment of FIGS. 9 and 10 is especially suitable when
leads 124 are curved so as to be easily placed within a depression
132. However, depressions 132 may be adjusted in order to receive
an array of leads that lie within a plane.
[0062] In order to illustrate a further example of the manner in
which the contact structures of the invention may be adapted for
substantially any chip package, FIG. 11 is a partial
cross-sectional elevation view of yet another embodiment of the
invention, in which an interposer 210 has an array of contact
structures, some of which include raised members and some of which
include depressions. This arrangement may be used with integrated
circuit packages that have two or more sets of leads. For example,
some integrated circuits have two lead frames that lie in planes
that are displaced one from another. In this case, depressions 268
engage leads in one plane while raised members 270 engage leads in
the other plane. In other respects, interposer 210 may be
substantially similar to interposers 10 and 110 disclosed herein.
The raised members and depressions of the invention may be adapted
as needed to conform to the leads of specific integrated circuit
packages and may be provided in any combination on an interposer
structure.
[0063] Yet another embodiment of the invention is depicted in FIG.
12, wherein the contact structures of the previous embodiments are
replaced by conductive tape 326 and conductive bumps 372.
Conductive tape 326 may be disposed on interposer 310 so that it
extends from one face of interposer 310 to the opposite face.
Conductive bump 372 is built up over a conductive strip 358 of
conductive tape 326 and provides a contact surface 364 that can
electrically engage a lead 324. As in other embodiments of the
invention, conductive bumps 372 are preferably arrayed over body
322 in a pattern that corresponds to the leads of the particular
integrated circuit package that is used. In other respects, the
embodiment of FIG. 12 may be substantially similar to the other
embodiments disclosed herein, in that electrical contact may be
made with a lead substantially as close as desired to the body 322
of an integrated circuit package 320. Moreover, reliable contact
can be made with an integrated circuit package having a very fine
pitch. The pitch of terminal contact points 330 may be greater than
the pitch of the leads 324 by staggering terminal contact points
330. The material used in conductive bumps 372 may be the same as
the material used in the conductive layers disclosed herein.
[0064] Any of the foregoing embodiments may be adapted for use with
a variety of testing practices and methods. One common testing
method already disclosed herein involves bringing an integrated
circuit package into contact with the interposers so that testing
can be performed. Alternatively, the interposers disclosed herein
may be adapted for contacting integrated circuit packages that are
held in a tray or another similar collection. In particular, the
interposers may be lowered or positioned onto a stationary
integrated circuit package while the testing operation is
conducted, after which the interposers are lifted away. Still
another variation involves providing a hinged assembly including an
interposer and an opposable and pivotally attached clamping
apparatus. In this method, the integrated circuit package is placed
on the interposer and within the hinged assembly, while the
clamping apparatus is pivoted onto the integrated circuit package.
In view of the foregoing, it should be understood that the
interposers may be adapted for use with substantially any testing
practice or method.
[0065] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. The scope of
the invention is, therefore, indicated by the appended claims
rather than by the foregoing description. All changes which come
within the meaning and range of equivalency of the claims are to be
embraced within their scope.
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