U.S. patent application number 12/361005 was filed with the patent office on 2009-06-11 for low profile clamp for use with apparatus for thermal control in the analysis of electronic devices.
Invention is credited to Daniel C. Canfield, John Joseph Harsany, Frank Sauk.
Application Number | 20090146359 12/361005 |
Document ID | / |
Family ID | 40720639 |
Filed Date | 2009-06-11 |
United States Patent
Application |
20090146359 |
Kind Code |
A1 |
Canfield; Daniel C. ; et
al. |
June 11, 2009 |
LOW PROFILE CLAMP FOR USE WITH APPARATUS FOR THERMAL CONTROL IN THE
ANALYSIS OF ELECTRONIC DEVICES
Abstract
A heat spreader comprising a sheet of transparent diamond with
an aperture therein that accommodates a solid-immersion lens (SIL).
The heat spreader may be mounted within a clamp which allows the
heat spreader to move freely across the Device Under Test (DUT)
whilst maintaining a very high degree of planarity and contact
between the diamond and the silicon substrate of the DUT. The DUT
is secured to its electrical interface with a low profile clamp,
the DUT may be held within the clamp by a mechanism that applies a
pressure to the sides of the DUT package.
Inventors: |
Canfield; Daniel C.;
(McMinnville, OR) ; Harsany; John Joseph;
(Tualatin, OR) ; Sauk; Frank; (San Ramon,
CA) |
Correspondence
Address: |
TROJAN LAW OFFICES
9250 WILSHIRE BLVD, SUITE 325
BEVERLY HILLS
CA
90212
US
|
Family ID: |
40720639 |
Appl. No.: |
12/361005 |
Filed: |
January 28, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11953630 |
Dec 10, 2007 |
|
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|
12361005 |
|
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Current U.S.
Class: |
269/289R |
Current CPC
Class: |
G01R 31/2891 20130101;
G01R 31/311 20130101 |
Class at
Publication: |
269/289.R |
International
Class: |
B23Q 3/00 20060101
B23Q003/00 |
Claims
1. A clamp for use in testing an electrical device comprising: a
frame having a first surface and a second surface parallel to the
first surface, and an aperture formed between the first surface and
the second surface for housing a device under test; a first jaw and
a second jaw; a first spring positioned to bias the first jaw in a
first direction towards the aperture for housing the device under
test; and a second spring positioned to bias the second jaw in a
second direction towards the aperture for housing the device under
test; wherein the first direction is perpendicular to and coplanar
with the second direction and parallel to the first and second
surfaces.
2. The clamp of claim 1 wherein no part of the first or second jaw,
or the first or second spring, extends above the first surface of
the frame.
3. The clamp of claim 1 further comprising a set screw for
adjusting the spring force of the first spring.
4. The clamp of claim 1 wherein the first spring includes at least
one limit post for limiting the spring force of the first
spring.
5. The clamp of claim 1 further comprising at least two protrusions
provided on the first surface of the frame.
6. The clamp of claim 1 wherein any surfaces of the jaws and frame
that face the aperture through the frame have been treated with a
finish to increase the coefficient of friction.
7. The clamp of claim 2 further comprising a set screw for
adjusting the spring force of the first spring.
8. The clamp of claim 2 wherein the first spring includes at least
one limit post for limiting the spring force of the first
spring.
9. The clamp of claim 2 further comprising at least two protrusions
provided on the first surface of the frame.
10. The clamp of claim 2 wherein any surfaces of the jaws and frame
that face the aperture through the frame have been treated with a
finish to increase the coefficient of friction.
11. The clamp of claim 3 wherein the first spring includes at least
one limit post for limiting the spring force of the first
spring.
12. The clamp of claim 3 further comprising at least two
protrusions provided on the first surface of the frame.
13. The clamp of claim 3 wherein any surfaces of the jaws and frame
that face the aperture through the frame have been treated with a
finish to increase the coefficient of friction.
14. The clamp of claim 4 further comprising at least two
protrusions provided on the first surface of the frame.
15. The clamp of claim 4 wherein any surfaces of the jaws and frame
that face the aperture through the frame have been treated with a
finish to increase the coefficient of friction.
16. The clamp of claim 5 wherein any surfaces of the jaws and frame
that face the aperture through the frame have been treated with a
finish to increase the coefficient of friction.
Description
STATEMENT OF PRIORITY
[0001] This is a continuation of pending U.S. application Ser. No.
11/953,630 filed on Dec. 10, 2007.
FIELD OF THE INVENTION
[0002] The present invention relates to methods and apparatus for
inspecting and analysing electronic devices such as
microprocessors.
BACKGROUND TO THE INVENTION
[0003] One known method for inspecting and analysing electronic
devices such as flip-chip packaged microprocessors involves optical
or infrared probing of the electronic device. During probing, a
device which includes a silicon substrate: the device under test
(DUT), is powered normally and its response is measured through the
back of the silicon substrate by analysing the phase shift in a
laser probe. For example, a modulated 1.064 .mu.m laser probe may
be used. The laser illuminates the device through an air-gap lens
or a solid-immersion-lens (SIL) and the reflected beam is collected
through the same lens. As the DUT is under power, it generates a
large amount of heat and needs to be actively cooled to maintain
its temperature and prevent it from entering thermal runaway.
[0004] In another known method, photon emission during switching is
monitored. Such a method requires that the thermal conditions
during the analysis are stable and reproducible in different
locations. Consequently, active cooling is also required in such a
test method.
[0005] Current state of the art inspection tools either use a fixed
diamond heat spreader to remove heat from the device, or use
liquid, such as water, sprayed on to the silicon substrate of the
device to remove the heat from the device. U.S. Pat. No. 6,836,131
discloses an apparatus for spray cooling. For example, "Transparent
Heat Spreader for Backside Optical Analysis of High Power
Microprocessors", Proceedings of the 26.sup.th International
Symposium for Testing and Failure Analysis (2000), pp. 547-551, to
T. M. Eiles, et al., discloses a transparent heat spreader formed
from a polycrystalline diamond window which is placed in contact
with the die of the DUT. The DUT is viewed through the heat
spreader which remains stationary relative to the DUT. Any point on
the die surface of the device can be viewed through the heat
spreader. U.S. Pat. No. 5,895,972 discloses an apparatus for
contacting a DUT with a stationary light-transparent heat spreader.
U.S. Pat. No. 6,760,223 discloses an apparatus for contacting a DUT
with a stationary light-transparent heat spreader and maintaining a
constant pressure.
[0006] Viewing through a diamond window is ideal for high power
dissipation during optical imaging of operating semiconductors.
However, viewing through the diamond heat spreader with a SIL
causes a substantial loss of image quality and significantly
reduces the improvement in numerical aperture (NA). Such a heat
spreader can be used satisfactorily to analyse a 90 nm feature on a
DUT but is incompatible with the optical characteristics of SILs
required to resolve features on DUTs which have a higher
resolution, e.g features of 65 nm and below that are currently
being developed. Such SILs must touch the silicon substrate of the
DUT to achieve the required image resolution.
[0007] The use of a high pressure liquid to spray cool the device
has limited thermal conductivity, especially near a SIL. In
addition, the method does not permit wide area imaging because the
turbulent liquid present in the light path impairs the image
quality acquired using air-gap lenses.
[0008] Consequently, an improved apparatus for analysing
semiconductor devices is required.
SUMMARY OF THE INVENTION
[0009] The present invention provides a heat spreader comprising a
sheet of transparent diamond having a first surface and a second
surface and an aperture formed between the first surface and the
second surface.
[0010] The diamond sheet is preferably chemical vapour deposition
(CVD) diamond, and more preferably polycrystalline (PC) CVD
diamond. The diamond sheet preferably has a thickness of between
300 .mu.m and 1 mm, and most preferably a thickness of 500
.mu.m.
[0011] The thermal conductivity of the diamond sheet is preferably
greater than 1000 W/mK, more preferably greater than 1500 W/mK,
more preferably greater than 1800 W/mK, and most preferably
approximately 2200 W/mK.
[0012] The transmission of the diamond sheet is preferably greater
than 70% at 10.6 microns and greater than or equal to 65% at 1.06
microns, and transmissive at 257 nm.
[0013] The aperture is shaped and sized to accommodate a SIL. A SIL
is typically 1-4 mm in cross section diameter, with a conical or
hemispherical shape. Consequently, the aperture may have a cross
section diameter of approximately 1-4 mm, with a conical or
hemispherical shape.
[0014] In order to improve optical access to the SIL, the aperture
in the diamond may be conical such that the area of the
cross-section at the first surface is larger than the area of the
cross-section at the second surface. The walls of the aperture are
preferably optical quality to allow imaging through the walls. By
providing a conical aperture, SILs of various diameters could be
used with the same diamond heat spreader.
[0015] The diamond heat spreader may be mounted within a heatsink.
The heatsink may have a cooling ring. The cooling ring may comprise
a copper plate. The copper plate may be plated with gold to prevent
corrosion. The diamond sheet may be attached to the cooling ring
with Indium solder. The cooling ring may be air or fluid-cooled and
may include a base having a plurality of cooling fins and a cover.
The coolant may be dry air or fluid in order to reduce the amount
of condensation forming on the cooling ring. The base of the
cooling ring may be separated from the cover by an insulating ring.
Preferably, no cooling fins are provided on the cover in order to
reduce the amount of condensation forming on the cover. The
insulating ring is preferably of comparable size to the base and
preferably formed of Teflon. The provision of such an insulating
ring reduces the amount of condensation that forms on the cooling
ring without impacting cooling performance.
[0016] For input air at -50.degree. C., a DUT at 0.degree.C. and a
device input power of 100 W, the thermal resistance of a heat
spreader is 0.5.degree. C./W. Preferably the thermal performance of
the heat spreader as a whole is in the range 0.4 to 0.6.degree.
C./W. Consequently, a 600 W device could be cooled using commonly
available air cooling systems.
[0017] In use, the heat spreader is placed with its second surface
in contact with the silicon substrate of a DUT so that the highly
effective cooling properties of the diamond heat spreader are
employed to cool the DUT. In order to maximise the resolution of
the analysis, a SIL can be placed in the aperture in the diamond
heat spreader so that the SIL is in direct contact with the silicon
substrate of the DUT. Preferably the profile of the aperture
matches that of the SIL in order to minimise heat build up.
[0018] The diamond heat spreader may be forced against the silicon
substrate of the DUT with a uniform pressure. The SIL may also be
forced against the silicon substrate of the DUT with a uniform
pressure, although the pressure on the SIL may be controlled
separately to that on the diamond heat spreader.
[0019] The heat spreader may be movable relative to the DUT in a
direction parallel to the surface of the silicon substrate of the
DUT, so that any point on the silicon substrate of the DUT can be
analysed at a high resolution with the SIL positioned in direct
contact with the silicon substrate of the DUT.
[0020] In order to maintain a uniform pressure on the silicon
substrate of the DUT and move the heat spreader relative to the
DUT, the heat spreader may be mounted within a clamp which allows
the heat spreader to move freely across the DUT whilst maintaining
a very high degree of planarity and contact between the diamond and
the silicon substrate of the DUT.
[0021] The clamp may comprise a frame having rails in an
X-direction and a Y-direction which is perpendicular to the
X-direction. The X- and Y- directions may be parallel to the
surface of the silicon substrate of the DUT. The heat spreader may
be mounted to slide on the rails. Consequently, the heat spreader
can be positioned at any position within the frame in the X-Y
plane. The frame may be provided with one or more springs for
applying pressure to the heat spreader in a direction towards the
DUT. The springs allow the heat spreader to be forced toward the
DUT with a constant force without restricting its movement in the
X-Y plane.
[0022] The heat spreader and SIL may be movable together.
[0023] Since the diamond heat spreader may be moved with the SIL,
it is not necessary for the diamond sheet to cover the whole
silicon substrate of DUT. Consequently, the size of the diamond can
be reduced relative to known prior art devices, and the cooling
ring can be brought closer to the SIL and the DUT.
[0024] The SIL lens could be movable out of the aperture, and an
air gap lens could be provided which could be used to analyse a
larger area of the DUT at a lower resolution, through the diamond
heat spreader. In such a case, the diamond heat spreader may be
large enough to cover a portion of the silicon substrate of the DUT
or the whole of the silicon substrate of the DUT.
[0025] Consequently, the arrangement of the present invention can
be used in conjunction with both air-gap and SIL lenses. Therefore,
both global-imaging and pin-point measurements can be achieved
using the same heat spreader by taking advantage of both the
optical transparency and thermal conductivity characteristics of
diamond.
[0026] Index matching fluid may be provided between the diamond and
the silicon substrate of the DUT to eliminate reflection losses
associated with light passing through the interface between
dissimilar materials. In addition it is used in this invention to
minimise friction between the diamond and the silicon substrate of
the DUT and to improve the thermal contact and heat transfer. The
index matching fluid may be sufficiently displaced from under the
SIL to avoid affecting its optical performance.
[0027] In order to improve cooling of the SIL through the diamond,
the SIL may be in intimate contact with the diamond heat spreader,
and/or index matching fluid may be provided between the diamond and
the SIL.
[0028] Analysis of the DUT is performed by connecting the DUT to a
socket which allows for easy insertion and removal of the DUT. Such
sockets use spring probes. Although the force required to connect
each probe is low, the number of probes is very high (up to several
thousand). Therefore, assuming the maximum compression force is 250
lbs, the DUT must be pushed downwards onto the socket with 250 lbs
of downward force. This is generally achieved by holding the DUT in
a clamp which pushes down on an upper surface of the DUT
package.
[0029] Accordingly, the present invention also provides a clamp for
a DUT which overcomes this problem. The clamp has a very low
profile which enables the heat spreader to move over a large area
without colliding with the clamp in which the DUT is mounted. In
particular, the clamp is provided so that its uppermost surface is
flush with the DUT package surface. Typically silicon substrates
are thinned to 100 .mu.m for such analysis. Consequently the
silicon substrate surface is positioned about 100 .mu.m above the
DUT package surface and, about 100 .mu.m above the uppermost
surface of the clamp.
[0030] In order to secure the DUT to its electrical interface with
a low profile clamp, the DUT may be held within the clamp by a
mechanism that applies a pressure to the sides of the DUT package.
In particular, the DUT clamp comprises a frame having a first
surface and a second surface parallel to the first surface, and an
aperture formed between the first surface and the second surface
for housing a device under test; a first jaw and a second jaw; a
first spring positioned to bias the first jaw in a first direction
towards the aperture for housing the device under test; and a
second spring positioned to bias the second jaw in a second
direction towards the aperture for housing the device under test;
wherein the first direction is perpendicular to and coplanar with
the second direction and parallel to the first and second
surfaces.
[0031] Each spring forces each jaw against the DUT package, and
each jaw forces the DUT package against a surface of the frame.
Preferably no part of the first or second jaw, or the first or
second spring extends above the first surface of the frame. The
spring force of each of the first and second springs may be
adjusted using a set screw. The spring force of each of the first
and second springs may be limited by limit posts provided on the
springs. At least two protrusions may be provided on the first
surface of the clamp frame. Such protrusions ensure that the heat
spreader is maintained at a constant distance from the DUT package
across the whole silicon substrate. The protrusions may extend the
same distance above the first surface of the DUT clamp as the
thickness of the silicon substrate of the DUT to ensure a contact
force planarity between the heat spreader and the silicon substrate
of the DUT.
[0032] Both the clamp frame and the clamp jaws may be formed from
stainless steel. The springs may be formed from beryllium copper
which has a lower stiffness than stainless steel and consequently
provides more control and feedback for the user mounting the DUT.
The surfaces of the frame and jaws that are in contact with the DUT
package are treated with a bead blast finish or coated with rubber
to increase their coefficient of friction.
[0033] If the number of spring probes is n and the force of each
spring probe is F.sub.s, then the total downward force required is
F.sub.sn. Assuming the finish given to the stainless steel jaws and
housing raises the coefficient of friction against the socket to
.mu..sub.s, this means that the jaws must provide a total sideward
force of F.sub.sn/.mu..sub.s to resist movement from the spring
probes. For example, if the maximum downward force, F.sub.sn,
required is 250 lbs, the DUT clamp must provide 250 lbs of downward
force by clamping sideways to maintain the DUT within the clamp. If
the finish given to the stainless steel jaws and housing raises the
coefficient of friction, .mu..sub.s, against the DUT to 0.4, the
jaws must provide a total sideward force of 625 lbs to resist
movement from the spring probes.
[0034] The DUT clamp controls the clamping force, maintains a very
low profile and takes up a minimum amount of electrical interface
area.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Embodiments of the present invention will now be described
with reference to the following drawing, in which:
[0036] FIG. 1 shows a schematic top view of a heat spreader
according to the present invention;
[0037] FIG. 2 shows a cross-sectional view of the heat spreader of
FIG. 1;
[0038] FIG. 3 shows a cross section view of the heat spreader of
FIG. 1 when positioned in contact with a silicon substrate of a
DUT;
[0039] FIG. 4 shows a perspective exploded view of a heat spreader
according to the present invention;
[0040] FIG. 5 shows a perspective view of the clamp and frame;
[0041] FIG. 6 shows a top view of the DUT clamp with the DUT in
place.
DETAILED DESCRIPTION OF THE INVENTION
[0042] FIGS. 1 to 3 show a heat spreader 1 according to the present
invention. The heat spreader 1 includes a sheet 10 of transparent
diamond having a first surface 11 and a second surface 12 and an
aperture 13 formed between the first surface 11 and the second
surface 12. The diamond sheet 10 preferably has a thickness of 500
.mu.m.
[0043] The aperture 13 is shaped and sized to accommodate a SIL 14.
The SIL 14 typically has a diameter of 1-4 mm. Consequently, the
aperture 13 typically has a diameter of approximately 1-4 mm.
[0044] In order to improve optical access to the SIL, the aperture
13 in the diamond sheet 10 is conical such that the area of the
cross-section of the aperture 13 at the first surface 11 is larger
than the area of the cross-section of the aperture 13 at the second
surface 12. The walls of the aperture 13 are smooth in order to
improve imaging through the diamond 10. The provision of the
conical aperture 13 allows the same heat spreader to be used with
SILs of different diameters.
[0045] The diamond sheet 10 is mounted within a heatsink comprising
a cooling ring. The diamond sheet 10 is attached to the cooling
ring with Indium solder in the area marked by arrow 16 in FIG. 2.
The cooling ring is air-cooled and includes a base 15 formed from
copper plated with gold to prevent corrosion. The cooling ring
includes a plurality of air channels and a cover 18 shown in FIG.
4. The air channels 17 are connected to an air source via inlet and
outlet cooling hoses 19. The base 15 of the cooling ring is
separated from the cover 18 by an insulating ring 18a. No cooling
fins are provided on the cover 18 in order to reduce condensation
forming on the cover 18. The insulating ring is the same size as
the base and preferably formed of Teflon. The provision of such an
insulating ring reduces the amount of condensation that forms on
the cooling ring without impacting cooling performance.
[0046] In use, the heat spreader 1 is placed with its second
surface 12 in contact with a silicon substrate 21 of the DUT 20 so
that the highly effective cooling properties of the diamond heat
spreader 1 are employed to cool the DUT 20. In order to maximise
the resolution of the analysis, a SIL 14 is placed in the aperture
13 in the diamond sheet 10 so that the SIL 14 is in direct contact
with the silicon substrate 21 of the DUT 20. The profile of the
aperture 13 matches that of the SIL 14 in order to minimise heat
build up.
[0047] The diamond heat spreader 1 is forced against the silicon
substrate 21 of the DUT 20 with a uniform pressure. The SIL 14 is
also forced against the silicon substrate 21 of the DUT 20 with a
uniform pressure. The pressure on the SIL 14 is controlled
separately to that on the diamond heat spreader 1.
[0048] The heat spreader 1 is movable relative to the DUT 20 in a
direction parallel to the surface of the silicon substrate 21 of
the DUT 20, so that any point on the silicon substrate 21 of the
DUT 20 can be analysed at a high resolution with the SIL 14
positioned in direct contact with the silicon substrate 21 of the
DUT 20.
[0049] As can be seen from FIG. 5, the heat spreader 1 is mounted
within a clamp 30 in order to maintain a uniform pressure on the
silicon substrate 21 of the DUT 20 and move the heat spreader 1
relative to the DUT 20. The clamp 30 allows the heat spreader to
move freely across the DUT 20 whilst maintaining a very high degree
of planarity and contact between the diamond sheet 10 and the
silicon substrate 21 of the DUT 20.
[0050] The clamp 30 comprises a frame 31 having rails 32, 33 in an
X-direction and a Y-direction which is perpendicular to the
X-direction. The X- and Y- directions are parallel to a surface of
the silicon substrate 21 of the DUT 20. The heat spreader 1 is
mounted to slide on the rails 32, 33. Consequently, the heat
spreader 1 can be positioned at any position within the frame 31 in
the X-Y plane. The clamp also includes a plurality of springs 34
for pushing the heat spreader 1 towards the DUT 20. The springs 34
allow the heat spreader 1 to be forced toward the DUT 20 with a
constant force without restricting its movement in the X-Y
plane.
[0051] The heat spreader 1 and SIL 14 can be moved together.
[0052] Since the heat spreader lower surface is highly polished,
the heat spreader can slide across the surface of the silicon
substrate 21 without scratching the substrate.
[0053] Since the heat spreader 1 can be moved with the SIL 14, it
is not necessary for the diamond sheet 10 to cover the whole of the
silicon substrate 21 of the DUT 20. Consequently, the size of the
diamond sheet 10 is smaller than that used in known prior art
devices, and the cooling ring 15 can be brought closer to the SIL
14 and the DUT 20.
[0054] The SIL lens 14 is movable out of the aperture 13, and an
air gap lens (not shown) could be provided which could be used to
analyse a larger area of the DUT 20 at a lower resolution, through
the transparent diamond sheet 10. In such a case, the diamond sheet
may be large enough to cover just a portion of the silicon
substrate 21 of the DUT 20 or, alternatively, the whole of the
silicon substrate 21 of the DUT 20. A preferred design is to
provide imaging for the largest field of view of all lenses
installed on the inspection tool.
[0055] Since the arrangement of the present invention can be used
in conjunction with both air-gap and SIL lenses, both
global-imaging and pin-point measurements can be achieved using the
same heat spreader.
[0056] Index matching fluid (not shown) is provided between the
heat spreader 1 and the silicon substrate 21 of the DUT 20 to
minimise friction between the heat spreader 1 and the silicon
substrate 21 of the DUT 20 and to improve the thermal contact and
heat transfer. The index matching fluid is sufficiently displaced
from under the SIL 14 to avoid affecting the optical performance of
the SIL.
[0057] In order to improve cooling of the SIL 14 through the
diamond sheet 10, the SIL 14 is positioned in intimate contact with
the diamond heat spreader, and index matching fluid is provided
between the diamond sheet 10 and the SIL 14.
[0058] The DUT 20 is held within a clamp 40. The clamp 40 has a
very low profile which enables the heat spreader 1 to move over a
large area without colliding with the clamp 40 in which the DUT 20
is mounted. In particular, the uppermost surface 41 of the clamp 40
is flush with the back surface of the package of the DUT. Typically
the silicon substrate is positioned about 100 .mu.m above the DUT
package surface and consequently, about 100 .mu.m above the
uppermost surface 41 of the clamp 40.
[0059] In order to secure the DUT 20 to its electrical interface
with a low profile clamp 40, the DUT 20 is held within the clamp by
a mechanism that applies a pressure to the sides of the DUT package
20. In particular, the DUT clamp 40 comprises a frame 42 in which
is mounted a pair of jaws 43. Each jaw 43 is forced against the DUT
package 20 by a spring 44. The first jaw 43 is forced by the first
spring 44 in a first direction and the second jaw 43 is forced by
the second spring 44 in a second direction which is coplanar with
and perpendicular to the first direction. Each of the first jaw 43
and the second jaw 43 forces the DUT package 20 against a vertical
surface of the frame 42. The spring force of each of the first and
second springs 44 is adjustable using a set screw 45. The spring
force of each of the first and second springs 44 is limited by
limit posts 46 provided on the springs 44. Protrusions 47 are
provided on the uppermost surface 41 of the clamp housing 42. These
protrusions 47 ensure that the heat spreader 1 is maintained at a
constant distance from the DUT package across the whole silicon
substrate 21. The protrusions 47 extend 100 .mu.m above the
uppermost surface 41 of the DUT clamp 40, i.e. the same distance as
the thickness of the silicon substrate 21, to ensure a contact
force planarity between the heat spreader 1 and the silicon
substrate 21 of the DUT 20.
[0060] Both the clamp frame 42 and the clamp jaws 43 are
manufactured from stainless steel. The springs 44 are manufactured
from beryllium copper which has a lower stiffness than stainless
steel and consequently provides more control and feedback to the
user. The surfaces of the frame 42 and jaws 43 that are in contact
with the DUT package 20 are treated with a bead blast finish or
coated with rubber to increase their coefficient of friction.
[0061] Analysis of the DUT 20 is performed by connecting the DUT 20
to a socket 50 which allows for easy insertion and removal of the
DUT 20. Such sockets 50 use spring probes. If the maximum
compression force required is 250 lbs, the DUT clamp 40 must
provide 250 lbs of downward force by clamping sideways to maintain
the DUT 20 within the clamp 40 when it is connected to the socket
50. If the finish given to the stainless steel jaws and housing
raises the coefficient of friction (.mu..sub.s) against the socket
to 0.4, this means that the jaws must provide a total sideward
force of 625 lbs to resist movement from the spring probes.
[0062] The DUT clamp 40 controls the clamping force, maintains a
very low profile and takes up a minimum amount of electrical
interface area.
[0063] It will of course be understood that the present invention
has been described above purely by way of example, and that
modifications of detail can be made within the scope of the
invention as defined by the claims.
* * * * *