U.S. patent application number 09/886033 was filed with the patent office on 2001-11-08 for method for fabricating probe tip portion composed by coaxial cable.
Invention is credited to Hayakawa, Satoshi, Inoue, Hirobumi, Matsunaga, Kouji, Nikaidou, Masahiko, Tanehashi, Masao, Taura, Toru, Yamagishi, Yuuichi.
Application Number | 20010038294 09/886033 |
Document ID | / |
Family ID | 27462182 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010038294 |
Kind Code |
A1 |
Matsunaga, Kouji ; et
al. |
November 8, 2001 |
Method for fabricating probe tip portion composed by coaxial
cable
Abstract
In a tip portion structure basically having a substrate, a plate
spring, and a ground block, the substrate is attached to a signal
line on a back surface of the substrate and is contacted on the tip
with the signal electrode of the DUT placed on a device stage. The
plate spring is made of a resilient material, placed on the front
side of the substrate, and positioned to apply a pressure to the
substrate. The ground block is positioned between the signal line
and the device stage functioned as a ground electrode of the DUT.
Alternatively, the tip portion structure further may have a ground
plate or a ground surface formed of a conductive thin plate
covering entirely the front surface of the substrate, and shaped to
surround the signal line in cooperation with the ground block. A
plurality of the signal lines may be arranged in parallel on the
same plane of the substrate. Another tip portion structure is based
on a coaxial cable to be cut from the center at a plane
perpendicular to the axial direction thereof along one or more
oblique plane. A metal ring fitted over a periphery of the coaxial
outer conductor may be used.
Inventors: |
Matsunaga, Kouji; (Tokyo,
JP) ; Inoue, Hirobumi; (Tokyo, JP) ;
Tanehashi, Masao; (Tokyo, JP) ; Taura, Toru;
(Tokyo, JP) ; Nikaidou, Masahiko; (Tokyo, JP)
; Yamagishi, Yuuichi; (Osaka, JP) ; Hayakawa,
Satoshi; (Kanagawa, JP) |
Correspondence
Address: |
David A. Blumenthal
FOLEY & LARDNER
Washington Harbour
3000 K Street, N.W., Suite 500
Washington
DC
20007-5109
US
|
Family ID: |
27462182 |
Appl. No.: |
09/886033 |
Filed: |
June 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
09886033 |
Jun 22, 2001 |
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09328362 |
Jun 9, 1999 |
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6281691 |
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Current U.S.
Class: |
29/828 |
Current CPC
Class: |
G01R 1/06772 20130101;
G01R 1/06738 20130101; Y10T 29/49123 20150115 |
Class at
Publication: |
324/754 |
International
Class: |
G01R 031/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 9, 1998 |
JP |
10-161021 |
Jun 16, 1998 |
JP |
10-167991 |
Jun 16, 1998 |
JP |
10-168248 |
Feb 25, 1999 |
JP |
11-048325 |
Claims
What is claimed is:
1. A tip portion structure of a high-frequency probe having a
signal line which has a fore end pressed against a signal electrode
of a DUT (device-under-test) being placed on a device stage, and a
rear end connected to a connector for connection to an external
measuring instrument, said tip portion structure comprising: a tip
substrate having a front surface and a back surface attached to
said signal line formed on the back surface; a conductive thin
ground plate covering entirely the front surface of said tip
substrate; a plate spring positioned to apply a pressure to said
tip substrate in a state that the fore end of said signal line is
pressed against the signal electrode of said DUT; and a conductive
ground block positioned with a predetermined gap against the back
surface of said tip substrate, and contacting with a ground surface
of said device stage to establish electrical connection in a state
that the fore end of said signal line is pressed against the signal
electrode of said DUT.
2. A tip portion structure of a high-frequency probe according to
claim 1, wherein: said substrate being formed by a tip substrate is
formed of a film-like sheet attaching said signal line; said plate
spring being formed by a resilient material positioned to apply a
pressure to said tip substrate in a state that the fore end of said
signal line is pressed against the signal electrode of said DUT;
and said ground block is being positioned between said signal line
and said device stage functioning as a ground electrode by
establishing electrical connection with said DUT.
3. A tip portion structure of a high-frequency probe according to
claim 2, wherein a contact bump made of a conductive material is
provided at the fore end of said signal line, said contact bump
being brought into contact with the signal electrode.
4. A tip portion structure of a high-frequency probe according to
claim 2, wherein said signal line is formed by a microstrip line on
said tip substrate.
5. A tip portion structure of a high-frequency probe according to
claim 4, wherein said ground block establishes electrical
connection with the entirely-formed ground surface of said tip
substrate, and is shaped to surround said signal line in
cooperation with said ground surface while a predetermined gap is
left between said signal line.
6. A tip portion structure of a high-frequency probe according to
claim 2, wherein said signal line is attached to a surface of said
tip substrate and is divided into a plurality of signal lines
pressed against a plurality of signal electrodes of said DUT.
7. A tip portion structure of a high-frequency probe according to
claim 6, wherein said signal line is formed by a microstrip line on
said tip substrate, and said ground block establishes electrical
connection with the entirely-formed ground surface of said tip
substrate and is shaped to surround said plurality of signal lines
in cooperation with the entirely-formed ground surface while a
predetermined gap is left between said signal lines, said ground
block including partitions positioned between two adjacent ones of
said plurality of signal lines.
8. A tip portion structure of a high-frequency probe according to
claim 1, said tip portion structure connecting to an external
measuring instrument through a coaxial cable which includes a
coaxial inner conductor at the center and a coaxial outer conductor
at an outer periphery, both of the coaxial inner conductor and the
coaxial outer conductor being arranged in a concentric relation
with a dielectric interposed between said coaxial inner conductor
and said coaxial outer conductor, and having a proximal portion to
which a fore end of said coaxial cable is fixed, and a distal
portion including a contact bump disposed to contact with said DUT,
wherein said substrate has a front surface and a back surface
substantially parallel to an axis of said coaxial cable, and
includes a signal contact bump disposed at a fore end of the back
surface to be brought into contact with said DUT, and a signal line
connecting between said signal contact bump and a coaxial inner
conductor of said coaxial cable fixed to said proximal portion,
said ground plate which is operable as a lower absorber being
formed of a conductor, and including a substrate stand provided on
the front side of said lower absorber to receive the back surface
of said substrate fitted to said substrate stand with said signal
contact bump kept exposed, a guide groove formed in a proximal
portion thereof to receive said coaxial cable fitted to said guide
groove and bonded at a coaxial outer conductor thereof to said
guide groove by a conductive material, and a ground contact bump
disposed at a fore end of said lower absorber on the back side
thereof to be brought into contact with said DUT, said ground plate
being bonded at a proximal portion thereof to said lower absorber
by a conductive material in a state that fitted to said lower
absorber, said plate spring being operable as an upper absorber
which is made of a resilient material and which is placed on the
front side of said lower absorber; said substrate and said ground
plate being fitted to said lower absorber, and fixed at near a
proximal portion thereof to said lower absorber.
9. A tip portion structure of a high-frequency probe according to
claim 8, wherein said ground plate and said substrate are formed in
a one-piece structure.
10. A tip portion structure of a high-frequency probe according to
claim 8, wherein said lower absorber has a V-shaped groove for
positioning said coaxial cable and is formed in a bottom surface
thereof near the proximal portion to which said coaxial cable is
fitted.
11. A tip portion structure of a high-frequency probe according to
claim 8, wherein said coaxial cable is disposed in plural number,
and said lower absorber has said V-shaped groove formed in plural
number to arrange said coaxial cables in parallel on the same
plane.
12. A tip portion structure of a high-frequency probe according to
claim 8, wherein said coaxial cable is disposed in plural number,
and said signal contact bump is arranged in plural number at the
fore end of said substrate on the back surface thereof to lie in a
line in a direction perpendicular to the axial direction of said
coaxial cable.
13. A tip portion structure of a high-frequency probe according to
claim 8, wherein said upper absorber is one of the prepared, each
of which has a different strength of resiliency, and is detachably
fixed to said lower absorber.
14. A tip portion structure of a high-frequency probe according to
claim 1, further comprising a coaxial cable which includes a
coaxial inner conductor at the center and a coaxial outer conductor
at an outer periphery, both of the coaxial inner conductor and the
coaxial outer conductor being arranged in a concentric relation
with a dielectric interposed between said coaxial inner conductor
and said coaxial outer conductor, said coaxial cable having one end
surface which is given by a cross section surface perpendicular to
the axial direction thereof and which is used as the rear end
connected to the connector, said substrate having two surfaces
substantially normal to said cross section surface of said coaxial
cable, one of said two surfaces being a flat surface and entirely
formed a conductive ground surface as said ground plate, the other
surface having said signal line which connects to the coaxial inner
conductor of said coaxial cable exposed in said cross section
surface to a protruding portion at a distal end of said substrate
for electrical connection, said substrate having a proximal end
fixed to said cut surface of said coaxial cable, said plate spring
being formed by a bracket for said substrate formed of a plate-like
conductor, bonded to said ground surface to hold said substrate,
and fixedly connected to said cross section surface of said coaxial
cable for electrical connection with said coaxial outer
conductor.
15. A tip portion structure of a high-frequency probe according to
claim 14, wherein said signal line formed on said substrate
linearly extends in the same direction as an axis of said coaxial
inner conductor, and is bonded to said coaxial inner conductor at
said cross section surface by soldering.
16. A tip portion structure of a high-frequency probe according to
claim 14, wherein said signal line has a contact bump formed in an
exposed surface at a fore end thereof.
17. A tip portion structure of a high-frequency probe according to
claim 14, further comprising a ring made of a conductive material
and fixedly fitted over said coaxial cable in a position to cover
the circumference of the cross section surface of said coaxial
cable with electrical connection kept with said coaxial outer
conductor.
18. A tip portion structure of a high-frequency probe according to
claim 17, wherein said ring has a slit formed on the same side as
the surface of said substrate, in which said signal line is
exposed.
19. A tip portion structure of a high-frequency probe according to
claim 1, said tip portion structure having a coaxial cable which
comprises a coaxial inner conductor as said signal line, a coaxial
outer conductor instead of said ground plate, and a dielectric
interposed between said coaxial inner conductor and said coaxial
outer conductor in a concentric relation, said tip portion
structure including: an oblique cut surface formed by cutting said
coaxial cable at a plane perpendicular to the axial direction of
said coaxial cable to form a cross section surface as an end
surface, and then cutting said cross section surface from
substantially the center thereof along at least one oblique plane
with respect to the axial direction of said coaxial cable, said
ground block which is formed by a ring made of a conductive
material and fitted over a periphery of said coaxial outer
conductor to establish electrical connection with said coaxial
outer conductor, said tip portion structure further including a
contact bump bonded to said coaxial inner conductor exposed in said
end surface.
20. A tip portion structure of a high-frequency probe according to
claim 19, wherein said ring has a slit formed on the same side as
said contact bump with respect to the axis of said coaxial
cable.
21. A method of fabricating a tip portion of a high-frequency probe
formed of a coaxial cable comprising a coaxial inner conductor, a
coaxial outer conductor, and a dielectric interposed between said
coaxial inner conductor and said coaxial outer conductor in a
concentric relation, said method comprising: forming a cross
section surface by cutting said coaxial cable at a plane
perpendicular to the axial direction of said coaxial cable; forming
a oblique cut surface by cutting said cross section surface from
substantially the center thereof along at least one oblique plane
with respect to the axial direction of said coaxial cable; fixing a
ring made of a conductive material over a periphery of said coaxial
outer conductor to establish electrical connection with said
coaxial outer conductor; and bonding a contact bump to said coaxial
inner conductor exposed in said cross section surface; said fixing
of ring and said bonding contact bump being executed one after the
other in this order or in the reversed order.
22. A method of fabricating a tip portion of a high-frequency probe
according to claim 21, wherein said forming of the oblique cut
surface further cuts said cross section surface to form oblique cut
surfaces in the form of a pyramid while said coaxial inner
conductor is left as a fore end.
23. A method of fabricating a tip portion of a high-frequency probe
according to claim 21, wherein said forming the oblique cut surface
is performed by cutting said cross section surface from
substantially the center thereof along one oblique plane with
respect to the axial direction of said coaxial cable, thereby
forming a first oblique cut surface facing in the direction in
which the tip portion of said high-frequency probe is pressed
against a DUT.
24. A method of fabricating a tip portion of a high-frequency probe
according to claim 23, wherein said forming the oblique cut surface
further includes, subsequent to said forming the first oblique cut
surface, cutting said cross section surface from substantially the
center thereof along one oblique cut surface with respect to the
axial direction of said coaxial cable, thereby forming a second
oblique cut surface facing in the direction opposed to said first
oblique cut surface.
25. A method of fabricating a tip portion of a high frequency probe
according to claim 24, wherein said forming the oblique end surface
further includes, subsequent to said forming the second oblique cut
surface, cutting said cross section surface from substantially the
center thereof along two oblique cut surface with respect to the
axial direction of said coaxial cable, thereby forming third
oblique cut surfaces to form a rectangular pyramid with said
coaxial inner conductor exposed in said oblique cut surface being
an apex of said rectangular pyramid.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a high-frequency probe
having a signal line which has a fore end pressed against a signal
electrode of a device-under-test (abbreviated to DUT hereafter) to
be measured, and a rear end connected to a connector for connection
to an external measuring instrument.
[0003] The present invention especially relates to a high-frequency
probe for use in measurement of a DUT, which is placed on a device
stage establishing electrical connection with a ground electrode of
the DUT and serving as a ground electrode and which has a number of
signal electrodes arrayed with a narrow pitch. More particularly,
the present invention relates to a tip portion structure of a
high-frequency probe and a method of fabricating a probe tip
portion, which can provide contact with the signal electrodes and
electrical characteristics with higher reliability and more
stability.
[0004] 2. Description of the Related Art
[0005] Hitherto, as illustrated in FIGS. 1A and 1B, a
high-frequency probe 100 of the above-mentioned type comprises a
body block 110, a tip portion 120, and a connector 130. A coaxial
cable 111 penetrating the body block 110 is connected to the
connector 130 for electrical connection which connects an external
measuring instrument and the tip portion 120 brought into contact
with signal electrodes of a DUT to be measured.
[0006] Further, as illustrated in FIG. 2, the tip portion 120
comprises a signal contact lead 121 and two ground contact leads
122, each of which has resiliency. The ground contact leads 122 are
arranged side by side on both sides of the signal contact lead 121
and on substantially the same plane normal to a direction in which
the conductors bend due to resiliency. Thus the signal contact lead
121 and the ground contact leads 122 are formed in a coplanar
structure.
[0007] Usually, the signal contact lead 121 at the center serves as
a contact lead for a signal and is brought into contact with a
signal electrode 211 of a DUT 210. On the other hand, the ground
contact leads 122 on both sides of the signal contact lead 121
serve as ground contact leads and are brought into contact with
ground electrodes 212 of the DUT 210.
[0008] In case that the probe tip portion has such a conductor
array structure, the DUT is limited to a coplanar type device
wherein signal electrodes and ground electrodes are arranged on the
same plane and with the same pitch as conductors arranged in a tip
portion of a high-frequency probe.
[0009] A large surface area is required in the device of the
above-mentioned type having two ground electrodes arranged on both
sides of one signal electrode and on the same plane. For compound
devices obtained from a wafer of gallium arsenide (GaAs), in
particular, the wafer cost is higher than that of a silicon wafer.
Therefore, a reduction in the number of devices obtained from one
piece of wafer considerably pushes up the device cost. Accordingly,
a mass-produced device is constructed such that ground electrodes
are not disposed on the same plane as a signal electrode, and uses
its backside surface as a ground electrode. In addition, a chip
area is reduced and a wafer thickness is thinned to cut down the
device cost and to ensure a desired high-frequency
characteristic.
[0010] In a case that the conventional high-frequency probe
described above is employed to measure a DUT of such a structure
that the backside surface entirely serves as a ground electrode,
any contact between electrodes of the DUT and contact leads of a
probe tip portion cannot be achieved. Accordingly, the measurement
is performed for the DUT mounted on a board. In this case, the
board has measuring electrodes arranged with the same pitch as the
contact leads of the high-frequency probe, and the high-frequency
probe can be connected to the board.
[0011] Also, in the probe having the above tip portion structure,
pressing forces are applied to the electrodes of a DUT in an
unstable condition because the probe contact leads are pressed
against the DUT electrodes with any one electrode serving as a
fulcrum. Such an unstable condition may damage the contact lead
ends of the probe due to application of an excessive pressure.
[0012] The conventional high-frequency probe described above has
therefore problems as follows.
[0013] The first problem is that the measurement is very difficult
or impracticable when the signal electrode and the ground
electrodes of the DUT to be measured are not arranged on the same
plane.
[0014] The reason is because the contact leads of the probe are
arranged side by side on the same plane for making contact with the
DUT electrodes. Further, because the contact leads of the probe has
the pitch in match with the array pitch of those DUT electrodes,
the contact leads cannot contact with DUT electrodes having other
structures not in match with that pitch.
[0015] The second problem is that, in a case of the DUT to have not
the coplanar structure, a measuring board must be prepared and the
measurement requires time and labor.
[0016] The reason is because the above-described high-frequency
probe has the signal contact lead and the ground contact leads
which are of the coplanar structure. In other words, for a
measuring DUT of any structure different from the coplanar type, a
measuring board is necessary and the DUT being measured requires to
be mounted and dismounted to and from the measuring board. For the
DUT having a structure wherein a number of signal electrodes are
arrayed with a narrow pitch, particularly, a lot of time and labor
are taken for wiring job.
[0017] The third problem is that a sufficient contact pressure is
not obtained in a case that the contact lead of the probe is
pressed against the electrode of the DUT for measurement. Thus
resulting is in instability in measurement of electrical
characteristics, and that the contact lead of the probe is
susceptible to damage.
[0018] The reason is because the above-described high-frequency
probe has the structure wherein the contact lead contacts the
signal electrode of the DUT under measurement and bends at a
freely-suspended end. Also, because a pressing force is exerted on
the contact lead of the probe to bend its end about a fulcrum
positioned on the contact lead, it is difficult to adjust the
pressing force. Stated otherwise, the pressing force must be
somewhat moderated in view of such a risk that damage may occur at
the end of the contact lead if the pressing force is intensified to
make stable measurement.
[0019] The fourth problem is that the DUT has an increased area and
the product cost is increased.
[0020] The reason is because, for measuring a DUT by the
above-described high-frequency probe, ground electrode of the DUT
requires to be arranged on both sides of a signal electrode thereof
on the same plane in the same positional relationship as that
between a signal contact lead and ground contact leads of the
probe. In other words, because a surface area of the DUT is
increased, the number of DUTs produced from one piece of wafer is
reduced. The fourth problem is particularly remarkable in a case
that the DUT is a compound device of gallium arsenide being more
expensive than silicon.
[0021] Meanwhile, U.S. Pat. No. 5,506,515 discloses a simplified
structure of the tip portion of the high-frequency probe of the
above-described type. The disclosed structure of the tip portion of
the high-frequency probe is illustrated in FIG. 3. In the figure, a
coaxial cable 140 has a cross section surface at its end and
comprises a coaxial inner conductor, a coaxial outer conductor, and
a dielectric interposed between both the conductors, which are in a
concentric relation.
[0022] Specifically, the coaxial cable 140 comprises three
concentric parts, i.e., a coaxial inner conductor 141 at the axial
center, a coaxial outer conductor 142 at an outer periphery, and a
dielectric 143 interposed between both the conductors 141 and 142.
The end of the coaxial cable 140 is cut perpendicularly to the
coaxial direction to provide a cross section portion 144. A central
contact lead 151 is fixedly connected to the coaxial inner
conductor 141, while outer contact leads 152 are positioned on both
sides of the central contact lead 151 and are fixedly connected to
the coaxial outer conductor 142.
[0023] A description will now be made on the tip portion structure
of the high-frequency probe of the above-described type and a
method fabricating the probe tip portion with reference to FIG. 4A
to FIG. 4D in addition to FIG. 3. FIG. 4A to FIG. 4D are bottom
views looking, from the back side, the probe tip portion
illustrated in the perspective view of FIG. 3 and illustrating one
example of successive fabricating steps.
[0024] First, FIG. 4A shows a state after a step of cutting the
coaxial cable 140 in a plane normal to the axial direction to form
the cross section portion 144.
[0025] Then, FIG. 4B shows a state after a step of cutting out a
semi-cylindrical portion from the end of the coaxial cable 140
along a plane containing the axis and a plane perpendicular to that
plane. Thus defining is a longitudinal cut surface 145 containing
the axis, and a half cross section 146 perpendicular to the
longitudinal cut surface 145.
[0026] Thereafter, in a step illustrated in FIG. 4C, a frame
component 150 is positioned on and fixedly connected to the
longitudinal cut surface 145. The frame component 150 is formed by
machining together with the central contact lead 151, the outer
contact leads 152, and a base plate 153. The base plate 153
supports those leads such that the outer contact leads 152 are
positioned on both sides of the central contact lead 151. And the
outer contact leads 152 are connected to the coaxial outer
conductor 142 in the longitudinal cut surface 145 in a state that
the central contact lead 151 is connected to the coaxial inner
conductor 141 in the longitudinal cut surface 145.
[0027] Finally, in a step illustrated in FIG. 4D, the base plate
153 is no longer needed and is cut off from the contact leads,
whereby the tip portion structure illustrated in FIG. 3 is
completed.
[0028] The above method of fabricating the tip portion structure of
the conventional high-frequency probe requires the frame component
including the contact leads in addition to the coaxial cable. The
frame component includes one central contact lead, two outer
contact leads, and a base plate. Therefore, the above method
requires the steps of fixedly connecting the one central contact
lead to one coaxial inner conductor of the coaxial cable and the
two outer contact leads to one coaxial outer conductor thereof,
respectively, and then cutting off the base plate from the contact
leads. In other words, the frame component in the preparatory step
has a complicated shape, and the completed tip portion has a
relatively large number of parts. This raises a problem that the
fabricating process is complicated and the product cost is
increased.
[0029] Otherwise, the DUT is downsized and has a large number of
signal electrodes arrayed with a narrow pitch and a ground
electrode brought into contact with a device stage serving as a
test or measurement stage. In this case, a tip portion of a
high-frequency probe adapted for such a DUT can also be fabricated
by using a coaxial cable and a frame component with contact leads
and applying the fabricating method described above. A similar
problem as described above however still remains.
SUMMARY OF THE INVENTION
[0030] It is an object of the present invention to provide a tip
portion structure which is useful as a high-frequency probe and
which can solve the above-described problems.
[0031] It is another object of the present invention to provide a
method of fabricating a tip portion structure as described above in
a very simple manner.
[0032] According to an aspect of the present invention, a tip
portion structure of a high-frequency probe to which the present
invention is applicable has a signal line which has a fore end
pressed against a signal electrode of a DUT (device-under-test)
being placed on a device stage, and a rear end connected to a
connector for connection to an external measuring instrument. The
tip portion structure comprises a tip substrate having a front
surface and a back surface attached to said signal line formed on
the back surface, a conductive thin ground plate covering entirely
the front surface of the tip substrate, a plate spring positioned
to apply a pressure to the tip substrate in a state that the fore
end of the signal line is pressed against the signal electrode of
the DUT, and a conductive ground block positioned with a
predetermined gap against the back surface of the tip substrate,
and contacting with a ground surface of the device stage to
establish electrical connection in a state that the fore end of the
signal line is pressed against the signal electrode of the DUT.
[0033] According to another aspect of the present invention, a
method is for use in fabricating a tip portion of a high-frequency
probe formed of a coaxial cable comprising a coaxial inner
conductor, a coaxial outer conductor, and a dielectric interposed
between the coaxial inner conductor and the coaxial outer conductor
in a concentric relation. The method comprises forming a cross
section surface by cutting the coaxial cable at a plane
perpendicular to the axial direction of the coaxial cable, forming
a oblique cut surface by cutting the cross section surface from
substantially the center thereof along at least one oblique plane
with respect to the axial direction of the coaxial cable, fixing a
ring made of a conductive material over a periphery of the coaxial
outer conductor to establish electrical connection with the coaxial
outer conductor, and bonding a contact bump to the coaxial inner
conductor exposed in the cross section surface. The fixing of ring
and the bonding contact bump are executed one after the other in
this order or in the reversed order.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIGS. 1A and 1B show a front view and a side view
illustrating one example of a conventional high-frequency
probe.
[0035] FIG. 2 is a perspective view of the conventional
high-frequency probe in a state where a probe tip contacts
electrodes of a DUT.
[0036] FIG. 3 is a perspective view illustrating one example of a
structure of a conventional high-frequency probe using a coaxial
cable.
[0037] FIG. 4A is a bottom view of the conventional probe in a
state after a preparatory step, illustrating one example of a
process for fabricating the structure illustrated in FIG. 3.
[0038] FIG. 4B is a bottom view of the conventional probe in a
state after a cutting step forming two surfaces subsequent to the
state of FIG. 4A.
[0039] FIG. 4C is a bottom view of the conventional probe in a
state after a frame component mounting step subsequent to the state
of FIG. 4B.
[0040] FIG. 4D is a bottom view of the conventional probe in a
state after a finishing step subsequent to the state of FIG.
4C.
[0041] FIG. 5 is a partial sectional side view illustrating a tip
portion of a high-frequency probe according to a first embodiment
of the present invention.
[0042] FIG. 6 is a perspective view for explaining the structure
and operation of the probe tip portion illustrated in FIG. 5.
[0043] FIG. 7 is a perspective view illustrating a probe tip
portion according to an embodiment modified from that illustrated
in FIG. 6.
[0044] FIG. 8 is a perspective view for explaining a tip portion
structure having a plurality of signal lines in the tip portion
structure illustrated in FIG. 6.
[0045] FIG. 9 shows a partial view of the tip portion structure
illustrated in FIG. 8, and a sectional view taken along line Y-Y in
the partial view.
[0046] FIG. 10 is a sectional view illustrating a tip portion
structure according to an embodiment modified from that illustrated
in FIG. 9.
[0047] FIG. 11 is an exploded perspective view illustrating a tip
portion structure of a high-frequency probe according to a second
embodiment of the present invention.
[0048] FIG. 12 is an exploded perspective view of the tip portion
structure in which parts illustrated in FIG. 11 are assembled
except an upper absorber.
[0049] FIG. 13 is a side view of a completed assembly of the parts
illustrated in FIG. 11.
[0050] FIG. 14A is a perspective view illustrating a state of
fitting coaxial cables to a proximal portion of a lower absorber in
an embodiment modified from that illustrated in FIG. 12.
[0051] FIG. 14B is a front view of the lower absorber illustrated
in FIG. 14A as viewed in the direction facing a proximal end of the
lower absorber.
[0052] FIG. 15 is a side view for explaining a tip portion
structure of a high-frequency probe according to a third embodiment
of the present invention.
[0053] FIG. 16 is a front view of the tip portion structure of the
high-frequency probe, illustrated in FIG. 15, as viewed from the
side of a DUT under measurement.
[0054] FIG. 17A is a side view illustrating a tip portion structure
of a high-frequency probe according to an embodiment modified from
that illustrated in FIG. 15.
[0055] FIG. 17B is a front view of the tip portion structure of the
high-frequency probe, illustrated in FIG. 17A, as viewed from the
side of a DUT under measurement.
[0056] FIG. 18A is a side view illustrating a tip portion structure
of a high-frequency probe according to another embodiment modified
from that illustrated in FIG. 15.
[0057] FIG. 18B is a front view of the tip portion structure of the
high-frequency probe, illustrated in FIG. 18A, as viewed from the
side of a DUT under measurement.
[0058] FIG. 19A shows a front view of a tip portion structure of a
high-frequency probe according to a fourth embodiment of the
present invention in a state after a first step, and a sectional
view taken along line A-A in the front view.
[0059] FIG. 19B is a sectional view taken along line A-A in the
front view of FIG. 19A in a state after a second step subsequent to
the state of FIG. 19A.
[0060] FIG. 19C shows a front view of the tip portion structure in
a state after a third step subsequent to the state of FIG. 19B, and
a sectional view taken along line B-B in the front view.
[0061] FIG. 19D is a sectional view taken along line A-A in the
front view of FIG. 19C in a state after a fourth step subsequent to
the state of FIG. 19C.
[0062] FIG. 20 is a side view of a tip of the high-frequency probe
manufactured through the steps of FIG. 19A to FIG. 19D,
illustrating a state of the probe tip portion placed, by way of one
example, on a device stage in use.
[0063] FIG. 21 is a longitudinal sectional view in a state after a
step where can be inserted subsequent to the state of FIG. 19B.
[0064] FIG. 22 shows a front view of the tip portion structure in a
state after a step where can be inserted subsequent to the state of
FIG. 21, a sectional view taken along line C-C in the front view,
and a sectional view taken along line D-D in the front view.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0065] A first embodiment of the present invention will be
described below with reference to the drawings.
[0066] FIG. 5 is a partial sectional side view illustrating a tip
portion 320 of a high-frequency probe according to the first
embodiment of the present invention, and FIG. 6 is a perspective
view for explaining the structure and the operation of the tip
portion 320 illustrated in FIG. 5.
[0067] First, an outline of the tip portion structure of the
high-frequency probe according to the first embodiment will be
described with reference to FIG. 5 and FIG. 6.
[0068] The tip portion 320 of the high-frequency probe illustrated
in the drawings comprises a tip substrate 321, a plate spring 324,
and a ground block 325. A DUT 620 has a microstrip structure having
a signal electrode 621 formed on the front side thereof and a
ground electrode 622 formed on the backside thereof to establish
electrical connection with the surface of a device stage 610.
[0069] The tip substrate 321 to be the substrate in the summary
described above is in the form of a thin film made of a material,
e.g., a polyimide resin, which has a small dielectric constant and
enables the film to bend in a direction perpendicular to the film
surface. The tip substrate 321 has a microstrip structure having a
signal line 323 formed on one surface thereof brought into contact
with the signal electrode 621 and a ground surface 322 formed
entirely over the other surface thereof. The ground surface 322 is
forming the ground plate in the summary described above.
[0070] Although the tip substrate 321 bends, a constant spacing is
maintained between the signal line 323 and the ground surface 322.
Therefore, characteristic impedance of the tip substrate 321 does
not vary. One (fore) end of the signal line 323 is pressed against
the signal electrode 621 of the DUT 620, which is placed on the
surface of the device stage 610. And the other (rear) end of the
signal line 323 is electrically connected to a signal line on a
substrate 312, which extends through a body block 311. Thus
electrical connection of a signal reaches through the substrate 312
to a connector for connection to an external measuring
instrument.
[0071] On the other hand, the plate spring 324 in the summary
described above has a planar form and is bendable in a direction
coincident with the bending direction of the tip substrate 321. One
end of the plate spring 324 is fixed to the body block 311 by a
screw 313. And the other end of the plate spring 324 is held
against the ground surface 322 of the tip substrate 321 at a
position near its fore end. And the fore end of the signal line 323
is pressed against the signal electrode 621 under a predetermined
pressing force.
[0072] Further, the tip substrate 321 and the ground block 325 are
both fixed to the body block 311 and the substrate 312. At the same
time, the ground surface 322 and the signal line 323 are also both
fixed which are formed respectively on the opposite surfaces of the
tip substrate 321. In a fixed state, the ground surface 322
establishes electrical connection with the ground block 325, and
also establishes electrical connection with a ground line of the
substrate 312.
[0073] The signal line 323 is fixedly positioned in a space defined
by the ground block 325, and establishes electrical connection with
the signal line on the substrate 312.
[0074] Accordingly, in a state that the fore end of the signal line
323 is pressed to establish electrical connection against the
signal electrode 621 of the DUT 620 placed on the surface of the
device stage 610, the fore end of the ground block 325 is pressed
against the surface of the device stage 610 to establish electrical
contact with the ground electrode 622 of the DUT 620. On the other
hand, the ground block 325 is connected to the ground surface 322
on the tip substrate 321, through the shortest distance, and is
then connected to the external measuring instrument through the
ground line on the substrate 312 and the connector not to be
illustrated.
[0075] The operation and function of the probe tip portion will be
next described with reference to FIG. 6.
[0076] First, in a state that the signal line 323 in the tip
substrate 321 is pressed into contact with the signal electrode 621
of the DUT 620, the tip substrate 321 bends. The bend of the tip
substrate 321 is restrained by the plate spring 324 so that a
certain contact pressure is applied to the signal electrode
621.
[0077] Simultaneously, the ground block 325 is pressed against the
surface of the device stage 610 held in contact with the ground
electrode 622 of the DUT 620. Thus the ground block 325 enables the
ground surface 322 to establish, through the shortest distance,
electrical contact with the device stage 610 held in contact with
the ground electrode 622 of the DUT 620. Further, even with the
bend of the tip substrate 321 in the form of a thin film, the
transmission line of the high-frequency probe suffers from no
variation in characteristic impedance because both the ground
surface 322 and the signal line 323 bend at the same time.
[0078] An embodiment modified from that illustrated in FIG. 6 will
be next described with reference to FIG. 7.
[0079] The modified embodiment illustrated in FIG. 7 differs in a
contact bump 326 from the embodiment illustrated in FIG. 6. That
is, the contact bump 326 is made of a conductive material such as a
metal, and is provided at the fore end of the signal line 323
formed in the tip portion 320 described above. And the fore end of
the signal line 323 is brought into contact with the signal
electrode 621 of the DUT 620. Accordingly, the provision of contact
bump 326 ensures electrical connection with the signal electrode
211 more reliably.
[0080] Another modified embodiment including a plurality of signal
lines unlike the embodiments illustrated in FIG. 6 and FIG. 7 will
be next described with reference to FIG. 8.
[0081] The modified embodiment illustrated in FIG. 8 differs in
three signal lines 333 in the tip portion 330 from the embodiment
illustrated in FIG. 6. The three signal lines 333 are arranged on
one surface of a tip substrate 331 parallel to each other.
Accordingly, the tip substrate 331 and a ground block 335
surrounding the tip substrate 331 are structured to have a larger
width than that of the tip substrate 321, illustrated in FIG. 6, in
the direction in which the plurality of signal lines 333 are
arranged. A plate spring 334 instead of the plate spring 324 in
FIG. 7 may also have a large width corresponding to the wide tip
substrate 331. A DUT 630 has a ground electrode 632 formed on the
backside thereof, and a number of signal electrodes 631 with a
narrow pitch. With such a structure, the DUT 630 can be measured by
placing it on the device stage 610 as the ground potential.
[0082] With reference to FIG. 9, a description will be next made on
a structure having the plurality of signal lines 333 and including
a ground wall formed by the ground block 335 to surround the tip
substrate 331.
[0083] The structure of FIG. 9 intends to measure a high-frequency
characteristic with higher accuracy and more stability. The
structure of FIG. 9 is illustrated and described in connection with
the probe tip having a plurality of signal lines. But it is to be
here noted that the structure can also be similarly applied to the
probe tip having one signal line illustrated in FIG. 6.
[0084] FIG. 9 shows a partial view of only a tip portion 330
illustrated in FIG. 8, and a sectional view taken along line Y-Y in
the partial view. As described above with reference to FIG. 8, the
tip substrate 331 in the form of a thin film has three signal lines
333 arranged on the back side thereof, i.e., on the hidden side in
the partial view. A ground surface 332 is formed entirely over the
front side thereof. The tip substrate 331 is positioned with the
signal lines 333 located on the inner side, and serves as a lid for
an inner space defined by the ground block 335 in the form a gutter
shaped in cross-section. With such a structure, the signal lines
333 are surrounded by the ground surface 332 and the ground block
335 except their foremost ends brought into contact with the signal
electrodes of the DUT, while a certain spacing is left between the
signal lines 333 and the ground block 335. As a result, the tip
portion structure is simplified and the production cost can be held
down.
[0085] An embodiment modified from that illustrated in FIG. 9 will
be next described with reference to FIG. 10.
[0086] The modified embodiment illustrated in FIG. 10 differs in a
ground block 336 from that illustrated in FIG. 9. Specifically, the
ground block 336 illustrated in FIG. 10 includes ground walls 337
additionally formed to position between the adjacent signal lines
333 and to electro-magnetically isolate the signal lines 333
arranged parallel to each other. Such a structure contributes to
reducing crosstalk noise between the signal lines 333
respectively.
[0087] Next, a second embodiment of the present invention will be
described below with reference to the drawings. In the second
embodiment, a signal line connecting between a probe tip portion
and a connector is formed of a coaxial cable. Note that the
drawings referred to below to explain a tip portion structure are
schematic views deformed for illustrative purposes, and a relative
relation in size of parts is only by way of reference.
[0088] FIG. 11 and FIG. 12 are exploded perspective views
illustrating the second embodiment of the present invention.
[0089] A tip portion structure of a high-frequency probe
illustrated in FIG. 11 is assembled by placing a substrate 410, a
lower absorber 420, a ground plate 430, and an upper absorber 440,
one above another in the order named. During the assembling
process, two coaxial cables 450 are fitted to the lower absorber
420. The substrate 410 has signal contact bumps 411 and signal line
412. The lower absorber 420 has a ground contact bump 421, a
substrate stand 422, and guide grooves 423. The coaxial cable 450
comprises a coaxial inner conductor 451 and a coaxial outer
conductor 452.
[0090] In the exploded perspective view of FIG. 12, the upper
absorber 440 is illustrated as being separated from an assembly
obtained by assembling the substrate 410, the lower absorber 420
and the ground plate 430 together with the two coaxial cables 450,
illustrated in FIG. 11. And they are fixed by brazing. FIG. 13 is a
side view of a completed assembly of the parts illustrated in FIG.
11.
[0091] The substrate 410 is in the form of a flat plate. The
substrate 410 has a front surface and a back surface parallel to
axes of the two coaxial cables 450 connected to a proximal portion
of the substrate 410, and which has a distal portion tapering
toward its fore end. The two signal contact bumps 411 are provided
at the fore end of the substrate 410 on the back surface. The two
signal lines 412 connect respectively the two signal contact bumps
411 and the coaxial inner conductors 451 of the two coaxial cables
450 connected to the proximal portion of the substrate 410. The two
signal lines 412 (see FIG. 11) are formed of linear strip lines
bonded to the back surface of the substrate 410. The substrate 410
is made of a dielectric material, such as a resin or ceramic, for
the purpose of easy molding.
[0092] The lower absorber 420 to be the ground block in the summary
described above is formed of a conductor, and the ground contact
bump 421 is bonded to a fore end of the lower absorber 420 on the
backside surface. And the lower absorber 420 is formed and
positioning the ground contact bump 421 so as to keep the signal
contact bumps 411 exposed in the state that the substrate 410 is
fitted to the front side of the lower absorber 420. Accordingly,
the substrate stand 422 is formed on the front side of the lower
absorber 420 with a wall frame. And at least the proximal portion
of the substrate 410 is fitted by the wall frame in such a manner
that the signal contact bumps 411 are exposed on the backside of
the substrate 410.
[0093] The guide grooves 423 have wall frames allowing the coaxial
cables 450 to be fitted to a proximal portion of the lower absorber
420. The wall frames of the substrate stand 422 and the guide
grooves 423 have flat surfaces perpendicular to the front surface
of the lower absorber 420. The substrate 410 and the coaxial cables
450 are moved along the perpendicular flat surfaces of the
respective wall frames and then fitted in place. Further, the lower
absorber 420 has deep grooves which are formed in the substrate
stand 422 to extend along the signal line 412 on the substrate 410
and to define a gap left between the signal line 412 and a ground
surface formed by the lower absorber 420.
[0094] The ground plate 430 is formed of a conductor and is in the
form of a thin plate fully covering the front surface of the
substrate 410. The ground plate 430 is fitted to the lower absorber
420 together with the substrate 410, and is bonded at its proximal
portion to the lower absorber 420 by brazing 431.
[0095] The upper absorber 440 to be the plate spring in the summary
described above is formed of a resilient material. The upper
absorber 440 is placed on the front side of the lower absorber 420
after the substrate 410 and the ground plate 430 has been fitted to
it. The upper absorber 440 is fixed at its proximal portion and
thereabout to the lower absorber 420 by, e.g., screwing or
brazing.
[0096] Now, we take a case that the signal contact bumps 411 of the
substrate 410 is brought into contact with signal electrodes of a
DUT and is subject to stress acting to make the signal contact
bumps 411 apart from the ground contact bump 421 of the lower
absorber 420. In this case, an appropriate contact pressure is
obtained between the signal contact bumps 411 and the signal
electrodes of the DUT by selected resiliency of the upper absorber
440. The upper absorber 440 can be made of any suitable material so
long as the material can provide an appropriate contact pressure
between the signal contact bumps 411 and the signal electrodes of
the DUT.
[0097] Each of the coaxial cables 450 is fitted to the guide groove
423 of the lower absorber 420. The coaxial inner conductor 451 is
fixed by, e.g., brazing for electrical connection to the signal
line 412 exposed on the hidden side of the substrate 410, as viewed
in FIG. 11, which is fitted to the substrate stand 422 of the lower
absorber 420. On the other hand, the coaxial outer conductor 452 is
fixed in its portion contacting the lower absorber 420 by silver
brazing 453 for electrical connection to the ground contact bump
421.
[0098] The signal contact bumps 411 are arranged two parallel to
each other in a close relation to the fore end of the back surface
of the substrate 410 in the form of a flat plate. This structure
enables the signal contact bumps 411 to be easily adaptable for the
signal electrodes of the DUT which are formed in a fine pattern or
of multiple pins.
[0099] An embodiment modified from that illustrated in FIG. 11 to
FIG. 13 will be next described with reference to FIG. 14A and FIG.
14B. FIG. 14A is a perspective view illustrating a state of fitting
the coaxial cables 450 to the proximal portion of a lower absorber
460, and FIG. 14B is a front view of the lower absorber 460 as
viewed in the direction facing a proximal end of the lower
absorber.
[0100] While the modified embodiment is similar in general shape
and construction to the above-described embodiment, the lower
absorber 460 differs in a guide groove 463 and two V-shaped grooves
464 from the lower absorber 420, as illustrated. The guide groove
463 is formed in the proximal portion of the lower absorber 460 on
the front side and two V-shaped grooves 464 are formed in the guide
groove 463. Further, an upper absorber 466 has a shape in match
with that of the lower absorber 460.
[0101] The V-shaped grooves 464 are effective to guide and position
the coaxial inner conductors 451 of the coaxial cables 450 with
respect to the signal line 412 on the substrate 410, illustrated in
FIG. 11. This is effectively realized in a case that the coaxial
cables 450 are pushed into the guide groove 463 from the front side
of the lower absorber 460. As illustrated, the coaxial cables 450
are positioned in the corresponding V-shaped grooves 464 and then
fixedly fixed to a contact portion of the lower absorber 460 by
silver brazing 465 for electrical connection between the coaxial
cables 450 and the lower absorber 460.
[0102] While the V-shaped grooves are illustrated and described
above, a satisfactory function can also be obtained with relatively
deep, linear grooves. The V-shaped grooves may be replaced by
U-shaped grooves to which the coaxial cables can be fitted.
[0103] While the two coaxial cables are illustrated and described
above, the number of coaxial cables may be one, or three or more.
The guide grooves or the V-shaped grooves are provided in the lower
absorber in number corresponding to the number of coaxial cables to
be arranged. Also, in the above description, the ground plate is
separately formed of a flat plate having the same shape as the
substrate and is assembled with the substrate. The ground plate and
the substrate may be however formed in a one-piece structure.
[0104] Further, the upper absorber is formed such that the coaxial
cables fitted to the lower absorber are exposed on the front side
of the lower absorber to have effective resiliency. Therefore the
upper absorber may be formed to cover a part or the whole of the
exposed portions of the coaxial cables. The coaxial cable is bonded
to the lower absorber by soldering in the above description. But
the coaxial cables may be fixed by any other suitable means if
complete electrical connection and mechanical fixation can be
obtained.
[0105] While the shapes and materials of the individual parts are
illustrated and described above, the parts may have any other
suitable shapes and may be made of any other suitable materials so
long as satisfactory functions are obtained. In other words, the
above description should not be construed as limiting the scope of
the present invention.
[0106] Next, a third embodiment of the present invention will be
described below with reference to the drawings. In the third
embodiment, a tip portion of a high-frequency probe is formed at an
end of a coaxial cable with a simple structure.
[0107] FIG. 15 is a side view for explaining the third embodiment
of the present invention, and FIG. 16 is a front view of a tip
portion structure of a high-frequency probe 510 as viewed from the
side of a DUT 620.
[0108] In the tip portion structure of the high-frequency probe 510
illustrated in FIG. 15, a substrate 503 is mounted by a bracket 504
to a cross section surface of a coaxial cable 502 which is
perpendicular to the axial direction of the coaxial cable 502. The
bracket 504 is corresponding to the plate spring in the summary
described above.
[0109] Furthermore, FIG. 15 shows a manner of high-frequency
measurement using the high-frequency probe 510. A DUT 620 has a
ground electrode 622 entirely formed on the backside thereof, and
is placed on the surface of a device stage 610 which is formed as a
ground surface.
[0110] The coaxial cable 502 comprises a coaxial inner conductor
511 at the center, a coaxial outer conductor 512 at an outer
periphery, and a dielectric 513 interposed between both the
conductors, which are in a concentric relation. The coaxial cable
502 has one end face given by the cross section surface of the
coaxial cable 502 perpendicular to the axial direction thereof.
[0111] In a state after being mounted, the substrate 503 has two
surfaces normal to the cross section surface of the coaxial cable
502. A signal line 514 is provided on one surface of the substrate
503 to linearly extend from a proximal end to a distal end of the
substrate 503 along the central line. The signal line 514 is held
at the proximal end in close contact with the coaxial inner
conductor 511 of the coaxial cable 502 exposed in the cross section
surface thereof, and is connected to the coaxial inner conductor
511 for electrical connection by, e.g., soldering 515. The other
surface of the substrate 503 is a flat surface and is positioned
near the coaxial outer conductor 512. A ground surface 516 to be
the ground plate in the summary described above is made of a
conductive material and is formed entirely over the other surface
of the substrate 503.
[0112] The bracket 504 is formed of a plate-like conductor, e.g., a
resilient plate, and has an L-shape. One outer surface of the
bracket 504 is held in close contact with a semicircular portion of
the cross section surface of the coaxial cable 502, and the other
outer surface of the bracket 504 is bonded to the entirely-formed
ground surface 516 of the substrate 503. The proximal end of the
substrate 503 is held in close contact with the cross section
surface of the coaxial cable 502. The bracket 504 is held in close
contact with the coaxial outer conductor 512 of the coaxial cable
502, and is connected to the coaxial outer conductor 512 for
electrical connection by, e.g., soldering.
[0113] The surface of the device stage 610 illustrated in FIG. 15
is formed as a ground surface. In measurement, as illustrated, the
DUT 620 to be measured having the ground electrode 622 entirely
formed on the back side thereof is placed on the surface of the
device stage 610. Therefore, in a state that the signal line 514 is
contacted with a signal electrode 621 of the DUT 620, the coaxial
outer conductor 512 of the coaxial cable 502 is pressed against the
ground surface of the device stage 610. Accordingly, the signal
line 514 contacts with the signal electrode 621 as a contact base
surface which the coaxial outer conductor 512 contacts with the
ground surface of the device stage 610. And a contact pressure
applied to the signal electrode 621 can be maintained at a fixed
value in a reproducible manner.
[0114] As described above, a fore end of the coaxial outer
conductor 512 having no resiliency is pressed against the ground
surface of the device stage 610 which serves as a contact base
surface. Accordingly, the contact pressure applied to the signal
electrode 621 is determined depending on the amount of bend of the
substrate 503. Also, by giving resiliency to the bracket 504 to
which the substrate 503 is fixed, a desired contact pressure can be
obtained.
[0115] Further, in the above-described tip portion structure of the
high-frequency probe 510, the signal line 514 on the substrate 503
is positioned between the entirely-formed ground surface 516
thereof and the ground surface formed as the surface of the device
stage 610.
[0116] In the above description, the signal line on the substrate
is linearly extended and is directly connected to the coaxial inner
conductor by soldering. However, the shape, the connected position
and the connecting means of the signal line are optionally
selected, and are not limited to those described above. Also, while
the signal line on the substrate has been illustrated and described
as having a flat surface, the surface of the signal line is not
limited to the flat surface. Similarly, the shape and the mounting
position of the bracket are also not limited to those illustrated
and described above.
[0117] An embodiment modified from that illustrated in FIG. 15 and
FIG. 16 will be next described with reference to FIG. 17A and FIG.
17B in addition to FIG. 15 and FIG. 16.
[0118] FIG. 17A is a side view illustrating a modification of the
above-described third embodiment of the present invention, and FIG.
17B is a front view of a tip portion structure of a high-frequency
probe 520 as viewed from the side of a DUT.
[0119] The tip portion structure of the high-frequency probe 520
differs in a contact bump 521 from that illustrated in FIG. 15 or
FIG. 16. That is, the contact bump 521 made of a metal is provided
at a fore end of the signal line 514 which is brought into contact
with the signal electrode of the DUT. Such a structure renders the
signal line to contact the signal electrode of the DUT through a
contact bump, and therefore improves reproducibility in position of
the contact point of the contact bump on the signal electrode. As a
result, reproducibility in measurement can also be improved. The
other components may have the same structures and functions as
those illustrated in FIG. 15 and FIG. 16 and described above.
[0120] An embodiment modified from those illustrated in FIG. 15,
FIG.16, FIG. 17A and FIG. 17B will be next described with reference
to FIG. 18A and FIG. 18B in addition to FIG. 15 and FIG. 16.
[0121] FIG. 18A is a side view illustrating another modification of
the above-described third embodiment of the present invention, and
FIG. 18B is a front view of a tip portion structure of a
high-frequency probe 530 as viewed from the side of a DUT to be
measured.
[0122] The tip structure of the high-frequency probe 530 differs in
a ring 531 from that illustrated in FIG. 15 or FIG. 16. That is,
the ring 531 of such conductive material as metal covers the
coaxial outer conductor 512 in a close relation to surround an
outer periphery of the cross section surface of the coaxial cable
502 to which the substrate 503 is fixed. This structure prolongs
the life of a portion of the coaxial cable 502 brought into contact
with the ground surface of the device stage. Also, by forming a
slit 532 in a portion of the ring 531 brought into contact with the
ground surface of the device stage, the coaxial cable 502 can be
contacted with the ground surface with stability. Further, by
forming the slit 532 to provide protruding portions, which are
brought into contact with the ground surface of the device stage,
contact stability and reproducibility in position during probing
can be both improved. This results in good reproducibility in
measurement. The other components may have the same structures and
functions as those illustrated in FIG. 15 and FIG. 16 and described
above.
[0123] In the above modifications, different components are added
to the third embodiment illustrated in FIG. 15 and FIG. 16.
However, the contact bump 521 illustrated in FIG. 17A and FIG. 17B
and the ring 531 illustrated in FIG. 18A and FIG. 18B may be both
provided in the third embodiment.
[0124] While the shapes and positions in an assembly of the
individual parts are illustrated and described above, the
components may have any other suitable shapes and may be assembled
in any other suitable positions so long as satisfactory functions
are obtained. In other words, the above description should not be
construed as limiting the scope of the present invention.
[0125] Next, a fourth embodiment of the present invention will be
described below with reference to the drawings. In the fourth
embodiment, a tip portion of a high-frequency probe is formed by
machining a coaxial cable constituting a coaxial cable, and is
realized with a simpler structure.
[0126] FIG. 19A to FIG. 19D are explanatory views illustrating
successive machining steps of fabricating the tip portion of the
high-frequency probe according to the fourth embodiment. The method
comprises a cross section forming, an oblique cut surface forming,
a ring fixing, and a contact bump bonding.
[0127] The tip portion of the high-frequency probe comprises a
coaxial cable 710. The coaxial cable 710 comprises a coaxial inner
conductor 711, a coaxial outer conductor 712, and a dielectric 713
interposed between both the conductors, which are in a concentric
relation.
[0128] In a first fabricating to be the cross section forming, the
coaxial cable 710 is cut at a plane perpendicular to the axial
direction thereof. As a result, as illustrated in FIG. 19A, a cross
section surface 714 is formed at one end of the coaxial cable 710.
FIG. 19A shows a front view of the cross section surface 714 of the
coaxial cable 710 in a state after the first fabricating, and a
sectional view taken along line A-A in the front view.
[0129] In a second fabricating to be the oblique cut surface
forming, the coaxial cable 710 is cut obliquely with respect to the
axial direction, e.g., obliquely downwardly in an illustrated
example, along a plane crossing the center of the cross section
surface 714 in the circular form. As a result, a first oblique cut
surface 715 is formed as illustrated in a sectional view of FIG.
19B.
[0130] In a third fabricating to be the ring fixing, a ring 720
made of such a conductive material as a metal, is fitted over a
periphery of a coaxial outer conductor 712 of the coaxial cable 710
in a close relation so as to establish electrical connection. As
illustrated in FIG. 19C, the fitted ring 720 is positioned such
that the ring 720 covers a portion of the coaxial outer conductor
712 exposed by forming the first oblique cut surface 715. FIG. 19C
shows a front view of the cross section surface 714 of the coaxial
cable 710 in a state after the third fabricating and a sectional
view taken along line B-B in the front view.
[0131] In a final fabricating to be the contact bump bonding, a
metal contact bump 730 is bonded to a fore end of the coaxial inner
conductor 711 exposed in the first oblique cut surface 715. As a
result, the ring 720 and the contact bump 730 form contacts which
are independent of each other and are located on the surface side
of the first oblique cut surface 715, as illustrated in FIG. 19D.
Specifically, the illustrated ring 720 is a resilient member, and
has a slit 721 positioned in a plane containing the contact bump
730 and the axis of the coaxial cable 710 on the same side as the
contact bump 730. Therefore, the ring 720 establishes complete
electrical connection with the coaxial outer conductor 712 of the
coaxial cable 710 due to its own resiliency, and also serves as a
contact.
[0132] In measurement, as illustrated in FIG. 20, a DUT 820 to be
measured is placed on the surface of a device stage 810 which
serves as a device test ground connecting with a ground electrode
822 of the DUT 820. Then, the contact bump 730 of the tip portion
of the high-frequency probe described above with reference to FIG.
19B is pressed against a signal electrode 821 of the DUT 820 while
the first oblique cut surface 715 is positioned to face the device
stage 810. At the same time, a portion of the ring 720 including
the slit 721 is also pressed against the device stage 810 to ensure
contact with the ground surface. As a result, the tip portion of
the high-frequency probe can obtain reliable contacts with a signal
electrode and with a ground electrode respectively.
[0133] In the sequence of fabricating steps described above, the
contact bump is mounted after the ring has been fitted. However,
the sequence of steps may be reversed to the above one.
[0134] With reference to FIG. 21, a description will be next made
on a fabricating, which can be inserted subsequent to the state of
FIG. 19B.
[0135] After forming the first oblique cut surface 715 in the
fabricating of FIG. 21, the coaxial cable 710 is cut obliquely with
respect to the axial direction in a direction opposed to the first
oblique cut surface 715. In an illustrated example, the coaxial
cable 710 is cut obliquely upwardly along a plane crossing the
center of the cross section surface 714 (in FIG. 19B) in the
circular form.
[0136] Consequently, as illustrated in FIG. 21, the first oblique
cut surface 715 and the second oblique cut surface 716 are formed
to extend perpendicularly to a plane containing the drawing sheet
respectively. And a linear line defined by intersection between
both the cut surfaces corresponds to the central line of the cross
section surface 714 and is formed perpendicularly to the section
along line B-B in FIG. 19C.
[0137] Subsequent to the fabricating of FIG. 21, the ring 720 is
fitted as illustrated in FIG. 19C and the contact bump 730 is then
bonded as illustrated in FIG. 19D.
[0138] As a result of inserting the fabricating of FIG. 21, it is
realized that the coaxial cable 710 constituting the high-frequency
probe is obliquely contacted with the DUT under measurement as
illustrated in FIG. 20. Accordingly, a contact point at the fore
end of the coaxial inner conductor 711 can be visually observed
from a position right above the device stage 810.
[0139] With reference to FIG. 22, a description will be next made
on a fabricating, which can be inserted subsequent to the state of
FIG. 21. FIG. 22 shows a front view of the cross section surface
714 of the coaxial cable 710 in a state after fabricating to be
inserted subsequent to the fabricating described above with
reference to FIG. 21. That is, a vertical sectional view taken
along line C-C in the front view and looking from the side, and a
horizontal sectional view taken along line D-D in the front view
and looking from below are illustrated.
[0140] After forming the second oblique cut surface 716 as
illustrated in FIG. 21, in the fabricating of FIG. 22, the coaxial
cable 710 is cut obliquely to form two third oblique cut surfaces
717 and 718, and formed into a quadrangular pyramid shape. For this
purpose, the third oblique cut surfaces 717 and 718 cut the coaxial
cable 710 obliquely from the fore end with respect to the axial
direction in directions perpendicular to both the first and second
oblique cut surfaces 715, 716 and opposed to each other about the
axis.
[0141] As a result of inserting the fabricating of FIG. 22, in a
state that the coaxial cable 710 is obliquely contacted with the
DUT under measurement, the surrounding of a contact point at the
fore end of the coaxial inner conductor 711 can be visually
observed from above and side. This enables the coaxial cable 710 to
be positioned easily.
[0142] While the fore end of the coaxial cable is formed into a
quadrangular pyramid shape, the tip portion of the coaxial cable
may be formed into a triangular pyramid shape, a pyramid shape
having five or more faces, or a conical shape.
* * * * *