U.S. patent application number 09/765290 was filed with the patent office on 2001-07-19 for non-contact board inspection probe.
Invention is credited to Takada, Naoya.
Application Number | 20010008377 09/765290 |
Document ID | / |
Family ID | 14373002 |
Filed Date | 2001-07-19 |
United States Patent
Application |
20010008377 |
Kind Code |
A1 |
Takada, Naoya |
July 19, 2001 |
Non-contact board inspection probe
Abstract
A board inspection probe for inspecting pattern lines on a
circuit board for defects in a non-contact manner. The probe has an
electrode for radiating an electrical signal or receiving an
electrical signal radiated from a first pattern line. The probe
also has a shield to prevent, from reaching the electrode, unwanted
radiant waves emitted from pattern lines located in a region except
a board region immediately below an electrode surface of the
electrode. This shield is terminates near the electrode surface of
the electrode, so that radiant waves from only pattern lines
located on the board region immediately below the electrode are
received.
Inventors: |
Takada, Naoya;
(Hiroshima-ken, JP) |
Correspondence
Address: |
Platon N. Mandros
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. Box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
14373002 |
Appl. No.: |
09/765290 |
Filed: |
January 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09765290 |
Jan 22, 2001 |
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08795859 |
Feb 6, 1997 |
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6201398 |
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Current U.S.
Class: |
324/537 |
Current CPC
Class: |
G01R 31/309
20130101 |
Class at
Publication: |
324/537 |
International
Class: |
H01H 031/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 1996 |
JP |
8-104148 |
Claims
What is claimed is:
1. A board inspection probe (600, 700) for inspecting a pattern
line on a circuit board for a defect in a non-contact manner,
comprising: a main body; an electrode (620) formed at a position
near a board side of said main body and having a conductive
electrode surface (620h) for radiating an electrical signal toward
a first pattern line (520) or receiving an electrical signal
radiated from said first pattern line; and a shield (610) which is
at least electrically grounded, wherein said shield (610) has a
blank surface which does not shield a radiant wave to a second
pattern line (520a) or a radiant wave from said second pattern line
(520a) in a first region of said board, said first region
substantially corresponding to said electrode surface of said
electrode, and a shield surface (610a, 610b, or 650) having an end
portion extending near an end portion of said electrode surface
without being in electrical contact with said end portion of said
electrode surface in order to mainly shield a radiant wave to a
third pattern line (520b) or a radiant wave from said third pattern
line (520b) in a second region except the first region on said
board.
2. The probe according to claim 1, wherein said main body has
vertical and horizontal surfaces substantially perpendicular and
parallel to a surface of said board, said electrode surface (620h)
is formed substantially parallel to said horizontal surface, and
said shield surface (610a, 610b) of said shield vertically and
horizontally extends to cover at least part of said vertical
surface of said main body on said vertical surface.
3. The probe according to claim 2, wherein said shield surface
(610a, 610b) vertically and horizontally extends to entirely cover
said vertical surface of said main body.
4. The probe according to claim 1, wherein pattern lines having a
pitch of several decade .mu.m are formed on said board.
5. The probe according to claim 1, wherein said board is a bare
board prior to mounting circuit parts thereon, and said electrode
surface has an area substantially equal to that of said circuit
parts in a planar direction.
6. The probe according to claim 1, wherein said electrode surface
has a size of several mm.sup.2 to several cm.sup.2.
7. The probe according to claim 1, wherein said shield surface is
divided into a first region (610v-1) and a second region (610v-2)
in a direction perpendicular to said electrode surface, said shield
surface within the first region shields radiation from or to said
pattern lines on said board, and said shield surface within the
second region shields electro-magnetic interference coming from
above said board.
8. The probe according to claim 1, wherein said shield comprises a
two-dimensionally spread flat conductive member (650), and wherein
said member has an opening as said blank surface at a substantially
center thereof, and has a conductive region extending in a
direction parallel to said electrode surface, and surrounding the
opening.
9. An inspection method for inspecting a board using said probe
defined in claim 1.
10. The method according to claim 9, further comprising using as an
inspection target a board on which pattern lines having a pitch of
several decade .mu.m are formed.
11. The method according to claim 9, further comprising bringing
said probe into substantial contact with said board while said
probe is electrically insulated from said board.
12. The method according to claim 9, wherein said board is a bare
board prior to mounting circuit parts thereon, and said electrode
surface has an area substantially equal to that of said circuit
parts in a planar direction.
13. The method according to claim 9, further comprising applying an
AC signal to an end portion of an inspection target pattern line on
said board and detecting an inspection signal at said
electrode.
14. The method according to claim 9, further comprising applying an
AC signal to said electrode and detecting an inspection signal at
an end portion of an inspection target pattern line on said
board.
15. The method according to claim 9, further comprising applying an
AC signal to an end portion of an inspection target pattern line on
said board or detecting an inspection signal at said end portion of
the pattern line, and grounding an end portion of a pattern line
except the inspection target pattern line.
16. The method according to claim 9, further comprising
sequentially switching the end portions of the inspection target
pattern lines.
17. A board inspection apparatus using said inspection method of
claim 9.
18. The apparatus according to claim 17, further comprising means
for moving said probe in an arbitrary direction.
19. A board inspection apparatus using said inspection method of
claim 10.
20. A board inspection apparatus using said inspection method of
claim 11.
21. A board inspection apparatus using said inspection method of
claim 12.
22. A board inspection apparatus using said inspection method of
claim 13.
23. A board inspection apparatus using said inspection method of
claim 14.
24. A board inspection apparatus using said inspection method of
claim 15.
25. A board inspection apparatus using said inspection method of
claim 16.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an inspection probe used
for inspecting a board in a non-contact manner, and an inspection
method and apparatus using this probe. A target board is
represented by a board printed with conductive patterns at a small
pitch and includes e.g., a flexible board (a "flexible board"
includes an LSI package which is not mounted with IC chip and is to
be mounted therewith, and will be referred to simply as a "circuit
board" hereinafter). More particularly, the present invention
relates to a non-contact board inspection probe and an inspection
method and apparatus, all of which are suitable for inspecting
local patterns on a board for disconnections and the like.
[0002] The board inspection probe and the inspection method and
apparatus of the present invention are effective in inspecting a
so-called bare circuit board on which no circuit elements such as
IC packages are mounted yet although conductive patterns having a
small pitch are printed thereon.
[0003] In conventional board inspection, if a board on which
conductive patterns having a small pitch are printed has a large
pitch on the electrode side, as shown in FIG. 1, probes can be
brought into contact with the electrode groups (two or more
electrode groups) of the board to energize the board (power is
supplied from one electrode group, and the inspection result is
detected on the other electrode group).
[0004] A recent highly-integrated circuit board, however, has small
pitches in not only conductive patterns, but also electrodes. This
makes it difficult to accurately bring probes into contact with the
electrodes having a small pitch. An inspection for determining
defectiveness/nondefectiveness (particularly, the presence/absence
of a disconnection) of such a board having patterns (conductive
paths) with a small pitch has often relied on visual observation or
the like.
[0005] In recent years, the conductive patterns of a board
(inspection target board) have a higher density (smaller pitch)
along with decreases in size and weight of electronic devices. The
decrease in pitch tends to cause disconnections in conductive
patterns. A strong demand has therefore arisen for board inspection
meeting this tendency. Demands for improving workability and
reliability and decreasing the cost have become important.
[0006] In inspection for a board having patterns with a small
pitch, in addition to a problem posed by the difficulty in accurate
positioning of probes on electrodes, another problem is posed by an
increase in the number of measuring points. More specifically, In
such a board, when the wiring density of conductive patterns
increases (i.e., when the pitch becomes small), the number of input
and output points (the number of measuring points) increases. Even
if contact probing is possible, it is technically difficult to
maintain stable contact precision and contact properties. In
addition, as the test conditions are becoming stricter than before,
complicated, high-precision inspection jigs must be prepared,
resulting in high cost.
[0007] Under these circumstances, several prior-art techniques
based on non-contact probing, i.e., the board inspection free from
the problem posed by contact between probes and electrodes are
known.
[0008] For example, British Patent No. GB2143954A has proposed a
technique for positioning a probe electrode at the end of a
conductive path to form capacitive coupling between the electrode
and the end of the conductive path. An AC signal is applied between
the electrode and the one end of the conductive path, and a signal
is detected at the other end of the conductive path through the
above capacitive coupling. By this technique, a board can be
inspected without bringing the probe into contact with the
conductive pattern.
[0009] Japanese Patent Laid-Open No. 6-34714 (U.S. Pat. No.
5,254,953) is deemed an improved proposal of the non-contact
inspection method disclosed in GB2143954A described above.
[0010] Japanese Patent Laid-Open No. 5-264672 (U.S. Pat. No.
5,274,336) discloses a capacitive coupling probe (probe chip) used
in an in-circuit test for a high-density circuit board.
[0011] In the above prior arts, the "non-contact" means coupling
free from ohmic contact and is equivalently used as the
"capacitive". That is, a means for capacitive coupling is a
capacitor.
[0012] The present inventor found that when the above prior-art
inspection method and apparatus, however, were applied to a circuit
board such as a bare board prior to mounting circuit parts thereon,
it was difficult to highly accurately detect the presence/absence
of a defect (e.g., a disconnection). That is, even if the prior-art
technique is used to inspect a board in which the presence of a
disconnection has been confirmed, an inspection result representing
the absence of a disconnection is obtained. The present inventor
found the cause for this as follows.
[0013] FIG. 2 is a block diagram of an inspection apparatus in U.S.
Pat. No. 5,254,953. This prior-art technique is an apparatus
serving as an in-circuit tester. This tester inspects to find
whether a lead wire 111 of an IC package 110 is normally connected
to a lead wire 140 on a circuit board by soldering 200. That is,
the tester inspects soldered portions, but does not inspects the
pattern itself for any defects.
[0014] Referring to FIG. 2, an AC signal is supplied from an
oscillator 100 to the lead wire 140 between a probe electrode 120
and the lead wire 111 through a capacitor layer formed by air layer
and the IC package 110. A shield 130 is arranged to prevent the
probe electrode 120 from picking up EMI (Electro-Magnetic
Interference) from various devices (not shown) located above the
probe electrode 120.
[0015] If soldering 200 is proper, the AC signal is detected by an
electrode 310 and measured by an inspection apparatus 300. Whether
soldering is defective or nondefective is determined by the
magnitude of the signal detected by the electrode 310. Note that
the capacitance of the capacitor layer formed by the air layer and
the IC package 110 between the probe electrode 120 and the lead
wire 111 is as small as several femtofarad (fF), and the amplitude
of the signal detected by the electrode 310 is very small.
[0016] The present inventor found that when this probe electrode
120 was applied to a bare board 500, as shown in FIG. 3, the
measurement of a signal by the electrode 310 upon intentionally
forming a disconnection 510 in a lead wire 520 on the board 500 had
almost no difference in the amplitude of the detection signal from
the measurement of a signal by the electrode 310 through a lead
wire 520 free from disconnections.
[0017] According to the findings of the present inventor, no
difference was found in detection signal between the cases in which
the disconnection 510 was present and it was absent because the
signal applied to the probe electrode 120 propagated in the
electro-magnetic field formed in the air layer and was received by
a lead wire portion 520a, and the signal on the lead wire portion
520a was detected by the electrode 310.
[0018] Although the inspection apparatus in FIG. 3 has the shield
130 which is effective to protect the probe electrode 120 from the
EMI signal coming from above, the inspection apparatus is
defenseless against radiant waves from various radiant sources
located below the electrode 120.
[0019] In inspecting a bare board, as shown in FIG. 3, the probe
electrode must particularly come closer to the bare board. In the
inspection apparatus disclosed in U.S. Pat. No. 5,254,953 to
inspect an in-circuit board which need not bring a probe electrode
closer to the board due to the presence of parts, the problem posed
by the EMI signal from the board does not arise because the probe
electrode is used far away from the board.
SUMMARY OF THE INVENTION
[0020] It is an object of the present invention to provide a board
detection probe and a board inspection method and apparatus,
wherein a shield for preventing an EMI signal from acting on a
pattern on a board or from being emitted from the pattern in the
board inspection apparatus for inspecting the board by causing a
probe to come close to the board, thereby realizing highly accurate
inspection.
[0021] In order to achieve the above object, a board inspection
probe (600, 700) for inspecting a pattern line on a circuit board
for a defect in a non-contact manner comprises:
[0022] a main body;
[0023] an electrode (620) formed at a position near a board side of
the main body and having a conductive electrode surface (620h) for
radiating an electrical signal toward a first pattern line (520) or
receiving an electrical signal radiated from the first pattern
line; and
[0024] a shield (610) which is at least electrically grounded,
wherein
[0025] the shield (610) has
[0026] a blank surface which does not shield a radiant wave to a
second pattern line (520a) or a radiant wave from the second
pattern line (520a) in a first region of the board which
substantially corresponds to the electrode surface of the
electrode, and
[0027] a shield surface (610a, 610b, or 650) having an end portion
extending near an end portion of the electrode surface without
being in electrical contact with the end portion of the electrode
surface in order to mainly shield a radiant wave to a third pattern
line (520b) or a radiant wave from the third pattern line (520b) in
a second region except the first region on the board.
[0028] It is another object of the present invention to provide an
inspection method and apparatus using the probe having the above
arrangement.
[0029] It is still another object of the present invention to
provide a probe in which the shield surface (610a, 610b) of the
shield horizontally and vertically extends to partially cover a
vertical surface of the electrode.
[0030] It is still another object of the present invention to
provide a probe in which the shield surface (610a, 610b) vertically
and horizontally extends to entirely cover the vertical surface of
the electrode.
[0031] According to an aspect of the present invention, pattern
lines having a pitch of several decade .mu.m are formed on the
board as a target board of a probe of the present invention.
[0032] According to another aspect of the present invention, the
board as a target board of the probe of the present invention is a
bare board prior to mounting circuit parts thereon, and the
electrode surface has an area substantially equal to that of the
circuit parts in the horizontal direction.
[0033] According to still another aspect of the present invention,
the electrode surface of the probe has a size of several cm.sup.2
to several mm.sup.2.
[0034] According to still another aspect of the present invention,
the shield surface is divided into a first region (610v-1) and a
second region (610v-2) in a direction perpendicular to the
electrode surface.
[0035] It is still another object of the present invention to
provide a probe structure suitable for a probe using a low-profile
electrode, in which
[0036] the shield comprises a two-dimensionally spread flat
conductive member (650), and
[0037] the member has an opening serving as the blank surface at
substantially the center thereof, and
[0038] a conductive region extending in a direction parallel to the
electrode surface so as to surround the opening.
[0039] It is still another object of the present invention to
provide a board inspection method of applying an AC signal to the
end portion of a pattern line serving as an inspection target or
detecting an inspection signal at the end portion of the pattern
line, and at the same time grounding the end portion of a pattern
line except the target pattern line.
[0040] According to an aspect of the inspection method of the
present invention, the end portion of the target pattern line is
sequentially switched.
[0041] According to an aspect of the inspection apparatus of the
present invention, the inspection apparatus further comprises means
for moving a probe in an arbitrary direction.
[0042] Other features and advantages of the present invention will
be apparent from the following description taken in conjunction
with the accompanying drawings, in which like reference characters
designate the same or similar parts throughout the figures
thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] FIG. 1 is a view showing pattern lines terminating with
large pitches at its two terminals;
[0044] FIG. 2 is a diagram showing the arrangement of a board
inspection apparatus system using a conventional probe;
[0045] FIG. 3 is a view for explaining a state in which a probe
used in the inspection system in FIG. 2 picks up unwanted radiant
waves;
[0046] FIG. 4 is a view showing the arrangement of a probe assembly
according to the first embodiment of the present invention;
[0047] FIG. 5 is a plan view showing the arrangement of a probe
assembly suitable for inspecting a board on which pattern lines
extend in four directions, the probe assembly being an example of
the probe assembly of the first embodiment (FIG. 4);
[0048] FIG. 6 is a perspective view showing the arrangement of a
probe assembly in which a shield is divided into upper and lower
regions, the probe assembly being as another example of the probe
assembly of the first embodiment (FIG. 4);
[0049] FIG. 7 is a view for explaining the arrangement of a probe
assembly according to the second embodiment of the present
invention;
[0050] FIG. 8 is a perspective view showing an example of the probe
assembly of the second embodiment (FIG. 7);
[0051] FIG. 9 is a block diagram showing the arrangement of a board
inspection apparatus (first embodiment) using a probe assembly of
the present invention;
[0052] FIG. 10 is block diagram showing the arrangement of a board
inspection apparatus (second embodiment) using a probe assembly of
the present invention; and
[0053] FIG. 11 illustrates how teaching points are arranged in an
inspection system according to a modified embodiment in which one
probe assembly is moved to the points.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0054] Two probes to which the present invention is applied, and
one inspection apparatus using these probes will be described with
reference to the accompanying drawings.
[0055] <Probe Assembly> . . . First Embodiment
[0056] FIG. 4 is a view for explaining the principle of the
arrangement of a probe assembly 600 according to the first
embodiment to which the present invention is applied.
[0057] The probe assembly 600 includes an electrode 620 and a
shield 610. Reference numeral 500 denotes a board serving as an
inspection target.
[0058] Pattern lines 520 and 530 are formed on the board 500. A
disconnection 510 is present in the pattern line 520. The pattern
line 520 is separated into pattern line portions 520a and 520b due
to the presence of this disconnection. FIG. 4 shows a state in
which the probe assembly 600 according to the first embodiment is
positioned above the pattern line portion 520b by a positioning
device (not shown). An electrode 310 is connected to one end of the
pattern line portion 520a.
[0059] When an AC inspection signal is applied to the electrode
310, an electric field or electro-magnetic field is formed along
the pattern line 520. In other words, weak radiant waves are
generated from all portions of the pattern line 520 and they are
apt to reach the electrode 620. Since the disconnection 510 is
present on the board 500, the pattern line portion 520b generates
no radiant waves, but the pattern line portion 520a generates
radiant waves. If the pattern line 530 is capacitively coupled to
or in ohmic contact with the pattern line 520, the pattern line 530
also generates radiant waves.
[0060] Since the pattern line 520 serving as the inspection target
has the disconnection 510, the electrode 620 should not receive any
radiant wave. The shield 610 prevents unwanted radiant waves
(radiant waves from the pattern line portion 520a and the pattern
line 530 in FIG. 4) from reaching the electrode 620. The pattern
line portion 520b generates no radiant waves, and the electrode 620
receives no radiant waves. Therefore, the amplitude of the
detection signal is zero or has a very low level.
[0061] If no disconnection 510 is present, the radiant waves from
the pattern line portion 520b are received by the electrode 620
while the radiant waves from the pattern line portion 520b are
shielded. When the electrode 620 is connected to an amplifier (not
shown), an amplified signal can be monitored to determine the
presence/absence of a disconnection.
[0062] The shield 510 must covers the electrode 620 so that the
electrode 620 may not receive any unwanted radiant waves. In FIG.
4, shields 610a and 610b cover vertical surfaces 620a and 620b of
the flat electrode 620 so that these vertical surfaces 620a and
620b to detect radiant waves from the pattern line portion 520a and
the pattern line 530.
[0063] Pattern lines (pitch: several decade .mu.m) are formed at a
very high density on a board to be inspected by this inspection
probe assembly. The amplitude of a signal to be applied to the
electrode 310 is small, and its frequency is also low (about 10
kHz). For this reason, to detect a signal having a large amplitude
by the probe, the probe assembly 600 must come very close to the
board surface.
[0064] When the probe assembly 600 comes very close to the board,
radiant waves from the pattern line portion 520a and the pattern
line 530 will not round about to be received by a horizontal
surface 620h of the electrode 620.
[0065] When the probe assembly 600 need not come very close to the
board (e.g., when pattern lines have a large pitch, or the
frequency or voltage of an inspection signal is high), the
horizontal surface 620h of the electrode of the probe assembly 600
is separated from the substrate surface. Therefore, the horizontal
surface 620h of the electrode 620 may receive the radiant waves
from the pattern line portion 520a and the pattern line 530. In
this case, the shields 610a and 610b must be further extended
downward.
[0066] The shield 610 need not entirely cover the vertical surfaces
of the electrode 620 because a vertical surface in a given
direction may not have any pattern line portion in this direction.
As the layout of pattern lines on a board serving as an inspection
target is known, a vertical surface in an unnecessary direction
need not be formed on the shield 610. That is, the shield
preferably has directivity, as needed.
[0067] FIG. 5 is a plan view of an example of the probe assembly
600 for inspecting a board having pattern lines extending in four
directions when viewed from the top. In this example, vertical
surfaces 610v of a shield are formed to surround the horizontal
surface 620h of the electrode 620. FIG. 6 is a perspective view of
the probe assembly 600 in FIG. 5.
[0068] A central metal conductor 630 forms an electrode. The
effective surface of this electrode is formed on the lower surface
of the metal conductor 630. Reference numeral 635 in FIG. 6 denotes
an insulating layer for insulating the vertical surfaces 610v of
the shield from the metal conductor 630 serving as an electrode.
The shield having the vertical walls 610v is made of conductive
metal. In the example shown in FIG. 6, the shield covers the
vertical wall surfaces of the metal conductor 630 with inner
surfaces. The shield is divided by a boundary 610 into an upper
region made of a metal net and a lower region made of a copper
plate. The upper region shields the electrode from radiant sources
(e.g., power supply lines of the inspection apparatus and probing
wiring lines) of various waves outside the board.
[0069] The size of the electrode surface of the probe assembly is
determined in accordance with the size of parts to be mounted on
the bare boards serving as a measurement target, i.e., the degree
of spread at the end portions of pattern lines on the board. For
example, the sizes of parts generally range from several mm to
several cm, and the sizes of electrode portions range from several
mm to several cm, accordingly.
[0070] <Probe Assembly> . . . Second Embodiment
[0071] FIG. 7 shows the structure of a probe assembly 700 according
to the second embodiment. An electrode 620 itself of the probe
assembly of the second embodiment is identical to the electrode 620
of the probe assembly of the first embodiment. The probe assembly
700 is different from the probe assembly of the first embodiment in
the shield structure.
[0072] Since the electrode 620 receives radiant waves, the height
of the electrode need not be large. The length of a vertical
surface 620v in the direction of height can be small. The vertical
surface 620v may receive unnecessary radiant waves although the
vertical surface 620 is low (its length is small). For this reason,
the probe assembly 700 of the second embodiment has a flat shield
650 extending in the horizontal direction.
[0073] FIG. 8 is a perspective view of the shield 650. An opening
is formed at the center of the shield 650. The electrode 630 is
stored in the opening of the shield 650. A gap 660 is formed
between the electrode 620 and the shield 650 and is preferably
filled with an insulating material. The material connects and fixes
the electrode 620 to the shield 650. The shield 650 moves together
with the electrode 620 upon movement of the electrode 620.
[0074] <Inspection Apparatus System> . . . First
Embodiment
[0075] FIG. 9 is a block diagram showing the arrangement of a board
inspection apparatus system to which a probe assembly of the
present invention is applied. Each of the probe assemblies of the
above two embodiments is applicable to the system shown in FIG.
9.
[0076] This inspection system is suitable for an inspection of a
board having a larger number of pattern lines such that the
terminals (the electrode 310 in FIG. 4) of the pattern lines as an
inspection target on one side have a relatively large pitch, and
the terminals of the pattern lines on the side of mounted parts
such as IC packages have a very small pitch.
[0077] Referring to FIG. 9, reference numeral 600 denotes the probe
assembly of the first or second embodiment. This probe assembly 600
is connected to a jig plate 900 which is capable of accommodating a
plurality of probe assemblies. A personal computer 800 controls the
jig plate 900 to move downward to fit the probe assemblies 600
closer to a board 700, and to move upward to separate from the
board 700 when a measurement test is terminated.
[0078] A pattern line group constituted by a large-pitch pattern
line portion 750 and a small-pitch pattern line portion 760 is
formed on the board 700 as an inspection target. The board 700 is
entirely grounded by a ground plate 680 disposed under the board
700.
[0079] The terminals of the large-pitch pattern line portion 750
are connected to the probes of a probe group 706, respectively. The
lead wires from the probe group 706 are connected to a switch box
705.
[0080] Referring to FIG. 9, reference numeral 701 denotes an
oscillator for generating a DC inspection signal; 702, a DC power
supply for generating a DC signal; and 703, a power supply relay
for switching between the AC signal from the oscillator 701 and the
DC signal from the power supply 702. A switch 704 is a two-contact
switch, one contact (contact b) of which is grounded.
[0081] The switch box 705 has switch elements whose number is
larger than or equal to that of the contact probes of the contact
group 706. Each switch element has two contacts. When each switch
element is connected to the a side, the signal from the relay 703
is supplied to the corresponding contact probe of the probe group
706. When each switch element is connected to the b side, the
potential from the switch 704 is supplied to the corresponding
contact probe of the probe group 706.
[0082] The signal detected by the probe assembly 600 is supplied to
a waveform processor 710 and subjected to filtering in a filter
(BPF) 711. The output from the filter 711 is amplified by an
amplifier 712. The amplified signal is converted into a digital
signal by an A/D converter 713. The digital signal is fetched into
the personal computer 800.
[0083] Note that the conductive pattern of the illustrated
inspection target board 700 has 5-channel conductive paths for
illustrative convenience. However, the number of channels is not
limited to a specific one.
[0084] Short-Circuiting Test
[0085] A short-circuiting inspection for the conductive patterns of
the pattern line portion 760 will be described first.
[0086] The personal computer 800 controls the relay 703, the switch
705, and the switch box 705 as follows.
[0087] That is, the switch 704 is connected to the a side, i.e.,
the output from the switch 704 is connected to the A/D
converter.
[0088] Of the plurality of switch elements of the switch box 705,
only the switch elements connected to the probes of the probe group
706 connected to the pattern lines serving as the inspection
targets are connected to the terminal b sides, and the remaining
switches in the switch box 705 are connected to the terminal a
sides.
[0089] At the same time, the personal computer 800 controls to
connect the relay 703 to the terminal b side. A DC voltage is
applied from the DC power supply 702 to the inspection target
pattern lines.
[0090] If short-circuiting has occurred in an arbitrary pattern
line on the board 700, the DC voltage applied to the inspection
target pattern line (i.e., a pattern line connected to the
uppermost probe in FIG. 9) is returned through the short-circuited
pattern line and input to an A/D converter 714 through the contact
a side of the switch 704. If no short-circuiting is present, the
potential detected on the terminal a side of the switch 704 must be
low. The personal computer 800 monitors the output signal from the
A/D converter 714 to determine whether short-circuiting has
occurred in the inspection target pattern lines.
[0091] Note that the target pattern lines in the short-circuiting
test can be switched by switching the switches in the switch box
705.
[0092] Disconnection Test
[0093] A disconnection inspection for a conductive pattern will be
described below.
[0094] To perform a disconnection test, the relay 703, the switch
704, and the switch box 705 will be controlled as follows. More
specifically, the switch 704 is connected to the terminal b side
and grounded. Of the plurality of switch elements in the switch box
705, only the switch elements connected to the probes of the probe
group 706 connected to the inspection target pattern lines are
connected to the b sides, and the remaining switches in the switch
box 705 are connected to the a sides. At the same time, the
personal computer 800 controls to connect the relay 703 to the
terminal a side. Therefore, an AC signal is applied from the
oscillator 701 to the inspection target pattern lines.
[0095] Pattern lines except the inspection target pattern lines are
grounded to suppress generation of unnecessary radiant waves from
the pattern lines except the inspection target pattern lines.
[0096] The AC signal applied to the inspection target pattern lines
is received as radiant waves by the electrode of the probe assembly
600. The received radiant waves are filtered by the BPF 711 as an
electrical signal. The electrical signal is amplified and converted
into a digital signal.
[0097] The personal computer 800 compares the input signal from the
A/D converter 713 with a predetermined threshold value to determine
whether a disconnection is present. More specifically, if a
disconnection is present in one of the inspection target pattern
lines, the voltage level of the signal from the A/D converter 713
is much lower than the reference level. Therefore, the
presence/absence of a disconnection can be discriminated in
accordance with this level difference.
[0098] <Inspection Apparatus> . . . Second Embodiment
[0099] The inspection apparatus of the first embodiment applies an
AC inspection signal to the terminals of the large-pitch pattern
line portion. An inspection system of the second embodiment applies
an AC inspection signal from the electrode of a probe assembly 600
to a small-pitch pattern line portion.
[0100] The constituent elements of the inspection apparatus of the
first embodiment can be applied to the inspection apparatus of the
second embodiment. The same reference numerals as in the first
embodiment of FIG. 9 denote the same parts in FIG. 10.
[0101] Short-Circuiting Test
[0102] A short-circuiting inspection for conductive patterns of a
pattern line portion 760 will be described first.
[0103] Referring to FIG. 10, a personal computer 800 controls a
relay 703, a switch 704, and a switch box 705 as follows.
[0104] That is, the switch 704 is connected to the a side, i.e.,
the output from the switch 704 is connected to the A/D
converter.
[0105] Of the plurality of switch elements of the switch box 705,
only the switch elements connected to the probes of a probe group
706 connected to the pattern lines serving as the inspection
targets are connected to the terminal b sides, and the remaining
switches in the switch box 705 are connected to the terminal a
sides. At the same time, the personal computer 800 controls to
connect the relay 703 to the terminal b side. A DC voltage is
applied from a DC power supply 702 to the inspection target pattern
lines.
[0106] If short-circuiting has occurred in an arbitrary pattern
line on a board 700, the DC voltage applied to the inspection
target pattern line (i.e., a pattern line connected to the
uppermost probe in FIG. 10) is returned through the short-circuited
pattern line and input to an A/D converter 714 through the contact
a side of the switch 704. If no short-circuiting is present, the
potential detected on the terminal a side of the switch 704 must be
low. The personal computer 800 monitors the output signal from the
A/D converter 714 to determine whether short-circuiting has
occurred in the inspection target pattern lines.
[0107] Note that the target pattern lines in the short-circuiting
test can be switched by switching the switches in the switch box
705 as in the inspection apparatus of the first embodiment.
[0108] Disconnection Test
[0109] A disconnection inspection for a conductive pattern in the
apparatus of the second embodiment will be described below.
[0110] To perform a disconnection test, the relay 703, the switch
704, and the switch box 705 will be controlled as follows with
referring to FIG. 10. More specifically, the switch 704 is
connected to the terminal b side and grounded. Of the plurality of
switch elements in the switch box 705, only the switch elements
connected to the probes of the probe group 706 connected to the
inspection target pattern lines are connected to the b sides, and
the remaining switches in the switch box 705 are connected to the a
sides.
[0111] Pattern lines except the inspection target pattern lines are
grounded to suppress generation of unnecessary radiant waves from
the pattern lines except the inspection target pattern lines.
[0112] At the same time, the personal computer 800 controls to
connect the relay 703 to the terminal a side, so that the relay 703
is connected to a BPF 711.
[0113] The personal computer 800 then drives an oscillator 701. The
AC signal from the oscillator 701 is applied to the inspection
target pattern lines through the probe assembly 600.
[0114] The radiant waves received by the inspection target pattern
lines appear on the probe group 706 and filtered by the BPF 711 as
an electrical signal. The electrical signal is amplified and
converted into a digital signal.
[0115] The personal computer 800 compares the input signal from the
A/D converter 713 with a predetermined threshold value to determine
whether a disconnection is present. More specifically, if a
disconnection is present in one of the inspection target pattern
lines, the voltage level of the signal from the A/D converter 713
is much lower than the reference level. Therefore, the
presence/absence of a disconnection can be discriminated in
accordance with this level difference.
[0116] <Modifications>
[0117] Referring to FIG. 9, the jig plate 900 may be substituted by
a positioning stage 900 capable of positioning the probe assembly
600 three-dimensionally (X, Y, and Z directions). The personal
computer 800 controls the stage 900 to move the probe assembly 600
to an arbitrary position on a board 700. As shown in FIG. 11, the
target moving positions (indicated by open circles in FIG. 11) are
in advance by teaching, and teaching point data for each board are
stored in a memory (not shown) in the personal computer 800.
[0118] .theta. axis is preferably added to the X, Y, and Z
directions in a positioning stage 900 in order to adjust
directivity.
[0119] <Advantages of Embodiments>
[0120] As has been described above, since a probe according to the
present invention can shield radiant waves which are emitted from
all sources located below the probe electrode and interfere with
inspection, board inspection using this probe can be performed with
a high accuracy.
[0121] As many apparently widely different embodiments of the
present invention can be made without departing from the spirit and
scope thereof, it is to be understood that the invention is not
limited to the specific embodiments thereof except as defined in
the appended claims.
* * * * *