Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
1998-11-20
2001-06-05
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C439S482000, C324S755090, C324S072500
Reexamination Certificate
active
06242930
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high-frequency probe for measuring a high-frequency characteristic by pressing one end against a signal electrode and ground electrodes of a device-under-test and connecting an external measuring instrument to another end to input and output electric signals. In particular, the present invention relates to a high-frequency probe capable of adjusting an impedance characteristic in an end part, the end part being detachable.
2. Description of the Related Art
Conventionally, as this type of high-frequency probe, for example, U.S. Pat. No. 4,849,689 proposes a high-frequency probe that is detachable.
A summary of this high-frequency probe will be described with reference to FIG.
1
.
In this high-frequency probe, a probe tip
1010
which contacts to a device-under-test is mutually connected to a connector assembly
1022
for external connection, which is attached to a probe body
1021
, through a circuit board
1023
. The probe tip
1010
has a central signal line or conductor and ground lines or conductors at both sides thereof on a thin plate-like substrate. The circuit board
1023
also has stripline construction where line-shaped ground lines are provided in both sides of the central signal line with the central conductor as the center.
The circuit board
1023
connecting to the connector assembly
1022
for external connection is fitted in a receptacle
1031
formed as a receiving groove on the upper surface of the probe body
1021
and having the same direction as that of the central signal line. In addition, the circuit board
1023
is fitted with the probe tip
1010
at another end, and consequently, forms a high-frequency transmission line with the central signal and ground lines. Furthermore, the circuit board
1023
is pressed by a pressure block
1040
from the upper direction when the circuit board
1023
is fitted in the receptacle
1031
by an absorber
1024
. This absorber
1024
arranges boundary conditions of the transmission line and shields the influence of an external magnetic field.
The pressure block
1040
holds a dielectric compressor bar
1041
and a compression member
1042
and is fitted with stud
1032
of the probe body
1021
using screws. When the circuit board
1023
is pressed by the pressure block
1040
, the dielectric compressor bar
1041
not only presses the probe tip
1010
against the circuit board
1023
from the upper direction, but also positions the circuit board
1023
. The compression member
1042
is an elastic body to securely press against the probe tip
1010
, so as to press the probe tip
1010
against the device-under-test.
The conventional high-frequency probe described above has a problem in that much effort is needed to replace the probe tip, thus requiring many working hours.
The reason for this is that many parts must be disassembled and reassembled, and the parts are small. An example will be described with reference to FIG.
1
. First, by removing the pressure block
1040
, at this time, the dielectric compressor bar
1041
and the compression member
1042
are removed. Next, by removing the circuit board
1023
and absorber
1024
from the receptacle
1031
, the circuit board
1023
and absorber
1024
are separated. Subsequently, the probe tip
1010
fitted with the circuit board
1023
is removed. On the other hand, in assembly, a reverse procedure is performed. In a process like this, careful operation is required because there is a possibility of dropping the dielectric compressor bar
1041
, the compression member
1042
, and the like around the operation area when they are removed.
Next, an end part
1110
of the probe tip (
1010
in
FIG. 1
) will be described with reference to FIG.
2
.
The end part
1110
is an example of an end part of a chip conductor, and has a central signal conductor
1111
and ground conductors
1112
on both sides thereof. These conductors connect to the central signal line and ground lines of the circuit board described above, respectively, and are arranged on the same plane.
As exemplified in
FIG. 3A
, in a device-under-test
2100
arranged on a surface of a device stage
3000
, the height of the signal electrode
2111
provided on the surface as a coplanar electrode is equal to that of the ground electrodes
2112
provided on both sides thereof. On the other hand, in the case shown in
FIG. 3B
, the height of the central signal electrode
2111
B is greater than that of ground electrode
2112
provided on both sides thereof. In this manner, usually, the height of the electrodes arranged in a line is varied.
On the other hand, as shown in
FIG. 4A
, so as to absorb any height difference between a signal electrode
2111
and ground electrodes
2112
of a device-under-test
2100
, only the central signal conductor
1111
in the end part
1110
of the high-frequency probe that is exemplified in
FIG. 3A
has elasticity. Therefore, in the end part
1110
, usually, the central signal conductor
1111
, as shown in the drawing, is positioned on the side to be pressed against the device and the central signal conductor
1111
bends with the elasticity according to the height of the signal electrode
2111
when the central signal conductor
1111
contacts to a device-under-test
2100
. Therefore, as shown in
FIG. 4B
, the central signal conductor
1111
contacts the signal electrode
2111
with elastic pressure when the ground conductors
1112
at both sides thereof contact the ground electrodes
2112
of the device-under-test
2100
.
In addition, in the high-frequency probe described above, if a ground electrode of the device-under-test is not on the same plane as a signal electrode and is provided instead on the entire surface of the backside of the device, the ground electrodes of the high-frequency probe cannot contact the ground electrodes of the device-under-test. In this case, an alternative method is adopted, wherein the device-under-test is mounted on a board and an end of the high-frequency probe is made to contact measurement electrodes provided on the board.
In addition, conventionally, characteristic impedance of a high-frequency probe is matched in 50&OHgr; of impedance in a transmission line of the entire probe.
In consequence, the conventional high-frequency probe described above is problematic in that product cost becomes expensive.
This problem arises because the end parts for contacting respective lines of a device-under-test are arranged in a coplanar construction on the same plane; hence, it is necessary to provide ground electrodes adjacent to a signal electrode of the device-under-test within a predetermined space. Thus, this causes the external size of the device-under-test to become large. In particular, in a compound device such as a GaAs whose wafer cost is expensive, the number of chips per wafer becomes small, and therefore cost increase is not avoidable. On the other hand, in the case of the device-under-test that is down-sized by providing the ground electrode on the entire surface of the backside, the measurement electrodes are provided on the board, and the device-under-test is mounted on the board to be measured. Therefore, a defective rate as a product increases and further repair cost is added.
Furthermore, another problem is that matching of the characteristic impedance in the end part of the high-frequency probe collapses and its high-frequency characteristics become worse.
A height difference between the central signal conductor and ground electrodes arises when the conductors of the end part of the high-frequency probe contact the electrodes of the device-under-test. Furthermore, the height of the electrodes of the device-under-test are different and at least the central signal conductor among the conductors in the end part of the high-frequency probe has elasticity.
Thus, the characteristic impedance of the high-frequency probe, as shown in
FIG. 3A
, is matched when the central signal conductor
1111
and ground conductors
1112
are on the same plane, and the sign
Hayakawa Satoshi
Inoue Hirobumi
Matsunaga Kouji
Nikaidou Masahiko
Tanehashi Masao
Metjahic Safet
NEC Corporation
Nguyen Jimmy
Ostrolenk Faber Gerb & Soffen, LLP
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