U.S. patent application number 08/875666 was filed with the patent office on 2001-10-11 for test device for flat electronic assemblies.
Invention is credited to BUKS, MANFRED, KRUEGER, JENS, SCHALLER, PETER.
Application Number | 20010028254 08/875666 |
Document ID | / |
Family ID | 7752974 |
Filed Date | 2001-10-11 |
United States Patent
Application |
20010028254 |
Kind Code |
A1 |
BUKS, MANFRED ; et
al. |
October 11, 2001 |
TEST DEVICE FOR FLAT ELECTRONIC ASSEMBLIES
Abstract
The invention concerns a test device for electronic board
assemblies, said device comprising at least one probe which can be
positioned parallel to the surface within the total area of an
assembly by drive devices. The test device is characterized in that
the drive devices comprise a probe drive which, operating in all
directions of movement independently of other probe drives,
positions the probe on a sub-area of the total area.
Inventors: |
BUKS, MANFRED;
(HENSTEDT-ULZBERG, DE) ; SCHALLER, PETER;
(B3ERLIN, DE) ; KRUEGER, JENS; (TANGSTEDT,
DE) |
Correspondence
Address: |
WALTER C FARLEY
P.O. BOX 329
HARPSWELL
ME
040790329
|
Family ID: |
7752974 |
Appl. No.: |
08/875666 |
Filed: |
December 22, 1997 |
PCT Filed: |
January 24, 1996 |
PCT NO: |
PCT/EP96/00280 |
Current U.S.
Class: |
324/750.22 |
Current CPC
Class: |
G01R 1/06705 20130101;
G01R 1/07392 20130101 |
Class at
Publication: |
324/754 |
International
Class: |
G01R 031/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 2, 1995 |
DE |
195 03 329.9 |
Claims
1. A test device for electronic board assemblies (4, 35) comprising
at least one probe (32, 45) which, within the total area of an
assembly, is positionable parallel to the surface by drive means,
characterised in that the drive means comprise a probe drive (11)
which, operating in all movement co-ordinates (X, Y) independently
of the probe drives of other probes, positions the probe on a
sub-area of the total area.
2. A test device according to claim 1, characterised in that the
sub-area is constructed so as to cover component locations
(34).
3. A test device according to claim 1, characterised in that a
plurality of probe drives (11) are disposed so that their probes
(13) cover adjacent sub-areas.
4. A test device according to claim 1, characterised in that the
probe drive (11) is disposed to be positionable in the surface by
drive elements (7, 7') of a main drive.
5. A test device according to claim 1, characterised in that the
probe (32) is disposed at the front end of an elongate needle (13)
which is mounted so as to be pivotable by means of the probe drive
(11) in respect of its angle to the assembly surface.
6. A test device according to claim 5, characterised in that the
probe drive comprises two transverse drives (15, 17) disposed at
different distances from the assembly surface and movable in
different directions (X, Y) parallel thereto, the needle (13) being
mounted on said transverse drives in each case so as to be
universally movable and longitudinally displaceable on at least one
gimbal mount (24, 25).
7. A test device according to claim 5, with a vertical drive for
the probe (32, 45) relatively to the assembly surface,
characterised in that the probe (32, 45) is movable in the
longitudinal direction of the needle (13) by the vertical drive
(26, 44).
8. A test device according to claims 6 and 7, characterised in that
the needle (13) is mounted for longitudinal displacement in both
gimbal mounts (24, 25) and is subjected, at its rear end remote
from the probe (32), to the action of the vertical drive (26, 30),
which moves the needle (13) in its entirety in the in the
longitudinal direction.
9. A test device according to claim 7, characterised in that the
probe (45) is longitudinally movable relatively to the needle by
means of the vertical drive (44) disposed on the needle (43).
10. A test device according to claim 1, characterised in that a
plurality of probe drives having different spatial resolution are
provided.
Description
[0001] The invention relates to a test device of the type referred
to in the preamble of claim 1.
[0002] Test devices of this kind are used for checking electronic
board assemblies of the most diverse type. Board assemblies of this
kind may, for example, be circuit boards, either with or without
components, or, for example, highly integrated circuits, of which a
plurality are disposed on a wafer, for IC manufacture. The probes
may also be of the most diverse kind, for example electric contact
points adapted to be connected via relay banks to stimulus sources
or measuring amplifiers of a suitable electronic measuring device,
or other probes used for other test methods, such as, for example,
inductive or capacitive sensors or optical scanners, e.g. cameras
or microscopes.
[0003] For the rapid testing of relatively large board assemblies,
such as, for example, computer motherboards, a plurality of probes
are usually provided, which can be positioned independently of one
another. A plurality of probes are frequently also necessary so
that when a plurality of electric junction points are to be
contacted simultaneously it may be possible, for example, to apply
a voltage to two junction points and tap off a voltage at a third
junction point. Control of the probes is usually effected by means
of sequence programs compiled individually for a specific board
assembly.
[0004] Known test devices of this type are always so constructed
that all the probes can be positioned over the total area of the
maximum board assembly which can still be tested on the test
device. In the conventional construction, the probes are disposed
on slides which are adapted to move over the surface of the board
assembly by means of spindles in the X-direction and the
Y-direction. In the case of raisable and lowerable contact points,
vertical drives operating in the Z-direction are provided on the
slides.
[0005] In the known test devices, the slide guides and drives have
to be movable over the entire length of the board assembly for
testing, i.e. over considerable lengths which, in the case of a
typical PC circuit board, amount to 30.times.40 cm for example.
With these considerable traversing distances high spatial
resolutions are required. For example, the individual contact pins
of modern ICs must be controlled with a length resolution of much
less than {fraction (1/10)} mm. Consequently, extremely stable and
heavy mountings and drives are required for the slides, resulting
in high moving masses.
[0006] A disadvantage of such test devices is the low speed of
travel from one point to another, due to the high moving masses.
High masses have to be continually accelerated and stopped. Decay
times also have to be taken into account.
[0007] In modern production lines, for example for electronic
equipment, board assemblies are, however, produced at a speed such
that known test devices of the type according to the preamble are
too slow. Consequently, only individual selected board assemblies
can be tested, or else a plurality of test devices have to be used
in parallel.
[0008] In contrast, test devices not in accordance with the
preamble and having a separate probe for each grid point of the
board assembly, i.e. those operating with stationary probes and
which do not have the above-mentioned speed problems, have
advantages in terms of speed. These test devices, however, are
disadvantageous in terms of circuitry and cost, and particularly in
respect of the fixed arrangement of the items under test. They are
therefore suitable only for a specific board assembly manufactured
on a large scale, while the test devices according to the preamble,
with their movable probes, are suitable for rapid changeover to
different board assemblies, i.e. for testing small-scale production
runs.
[0009] The object of the present invention is to provide a test
device of the type according to the preamble but with a higher test
speed.
[0010] This problem is solved according to the invention by the
features of the characterising part of claim 1.
[0011] With this construction, the advantage of the test devices
referred to in the preamble, i.e. to be able to test even larger
board assemblies with just one probe or just a few movable probes,
is retained. Compared with the known test devices in this area, the
advantage lies in the fact that a probe can be driven by a probe
drive over just a sub-area of the total board assembly area. The
traversed distances are thus reduced and the moving masses can be
reduced by several orders of magnitude with the same or better
control accuracy. This results in a traversing speed which can be
correspondingly increased by several orders of magnitude. For
specific applications, e.g. a large board with just one IC, it is
sufficient to provide the sub-area in the size of the IC. The other
few test points of the board can be tested in some other way. If a
plurality of probes are provided with corresponding sub-areas, the
probe drives can, for example, be provided to be movable between
different sub-areas of the board assembly or be provided in a
plurality so as to be stationary covering the total area. With only
a slightly increased mechanical outlay, the test speed is
considerably increased as a result of reducing the driven masses,
and this test speed is sufficient even for the most up-to-date
production lines. This construction also gives the possibility of
considerable further increase of the speed by increasing the number
of probes and probe drives.
[0012] The features of claim 2 are advantageously provided.
Electronic circuit boards which are already equipped, the most
frequent test case, are today predominantly equipped with ICs of
standard size. If the sub-areas are adapted to the ICs, it is
sufficient to position probe drives over all the ICs or move one or
more probe drives from one IC to the next, in order to be able to
approach all the test points to be covered.
[0013] The features of claim 3 are advantageously provided. For
example, a plurality of probe drives can be disposed in one line
and be moved by a main drive successively transversely to the
direction of the line over a larger board. Probe drives can also be
arranged to be stationary so as to cover the entire area of a board
assembly for testing, and this may be of advantage particularly for
smaller assemblies for testing. In the case of the latter
construction, the test speeds which can be achieved are very high
and hitherto unthinkable.
[0014] The features of claim 4 are advantageously provided. Probe
drives can be provided on the slides of known test devices instead
of the probes which were hitherto arranged to be stationary there,
and be moved in relatively large steps by the main drives. Even if
the main drives are very slow, as is usual in the prior art, this
does not appreciably slow down the total testing time, since, with
an optimised test sequence program, care can be taken to ensure
that the main drive makes only a few steps while the far larger
number of test steps is made by the very fast probe drives.
[0015] The features of claim 5 are advantageously provided. If the
probe is disposed on a pivotable needle, it can also be moved
beyond the base area of the probe drive. Probe drives can thus be
disposed adjacent one another, with the probes able to operate so
as to overlap in the boundary zone of two probe drives. In the
present state of the art, pivoting drives can be constructed very
easily and rapidly for the required control electronics. They offer
the additional advantage of enabling difficulty accessible
locations to be reached with an inclined needle, for example
locations of the kind which are accessible only from the side but
not directly from above.
[0016] The features of claim 6 are advantageously provided. With
this construction, the pivoting of the needle can be achieved very
easily with two linear drives. Test rigs have proved very rugged
and extremely rapid.
[0017] Probes can, for example, operate optically, capacitively or
without contact in some other manner, the distance from the surface
location for testing on the board assembly being uncritical. In
that case a vertical drive would not be required for the probe.
However, at least in the case of electrically contacting probes
constructed as a contact point a vertical drive is necessary to set
down and raise the contact point at each test location. In such
test devices, the features of claim 7 are advantageously provided.
By moving the contact point relatively to the probe drive the
masses are again very low and the speeds of movement high for this
drive as well.
[0018] The features of claim 8 are advantageously provided. As a
result, the needle is very easily constructed to be movable as a
whole.
[0019] Alternatively, according to claim 9, the contact point can
be moved relatively to the needle. The needle thus becomes
mechanically more complex but the moving masses are further
reduced.
[0020] The features of claim 10 are advantageously provided. This
creates a large number of possible variations for speed
optimisation. If, for example, an equipped printed circuit board
assembly comprises some highly integrated ICs with a very close
pattern of connecting pins to be contacted, but, for example,
otherwise has a number of discrete components with a coarser
pattern, maximum-resolution probe drives operating over a small
area can be provided to approach the ICs and probe drives of lesser
resolution can be used to approach the other contact locations. It
is even possible, for example, to use probes movable by slow main
drives for these other contact locations.
[0021] The invention is illustrated by way of example and
diagrammatically in the drawings wherein:
[0022] FIG. 1 is a section on the line 1-1 in FIG. 2 through a test
device.
[0023] FIG. 2 is a plan view of FIG. 1.
[0024] FIG. 3 is a vertical section through one of the probe drives
provided in the test device of FIGS. 1 and 2.
[0025] FIG. 4 is a plan view of the probe drive of FIG. 3.
[0026] FIG. 5 is a plan view of a test device of a different form
of construction with six stationary probe drives.
[0027] FIG. 6 is a side elevation of FIG. 5.
[0028] FIG. 7 is an elevation of the bottom end of the needle shown
in FIG. 3, with a different vertical drive, and
[0029] FIG. 8 is an elevation of the top end of the needle shown in
FIG. 3, with another variant of the vertical drive.
[0030] FIGS. 1 and 2 show a test device with two moving probes,
this device being of substantially known construction. A frame
comprising a baseplate 1 and two cheeks 2 accommodates on the
baseplate 1 by means of diagrammatically indicated holders 3 a
circuit board 4 for testing. As will be seen from the Figures, the
circuit board 4 is occupied by an array of ICs or other
components.
[0031] Two spindles 5, 5' extend between the cheeks 2 in a
traversing direction hereinafter referred to as the X-direction.
Cross-members 6, 6' run on said spindles, one being driven by the
spindle 5 and the other by the spindle 5'. Slides 7, 7' run on the
cross-members 6, 6' and are driven in the Y-direction by transverse
spindles 8, 8' mounted on the cross-members 6, 6' parallel thereto.
Drive motors 9, 9' are provided for the spindles 5, 5' and drive
motors 10, 10' for the transverse spindles 8, 8'.
[0032] With this conventional test device, the slides 7, 7' can be
traversed over any desired point of the circuit board 4 by
appropriate control of the motors 9, 9', 10, 10'. Each of the
slides 7, 7' carries a probe drive 11 for a probe disposed at the
end of a needle 13. A vertical drive is provided in the probe
drives 11 to enable the needles 13 to be raised and lowered.
[0033] In order to simplify the drawing, leads extending from the
probes to an electronic test device (not shown) and the electronic
test device itself are omitted from the drawing.
[0034] By means of the test device of known construction as shown
in FIGS. 1 and 2, the circuit board 4 can be contacted, for
example, at two electrical junctions at any time and, for example,
the current-flow resistance can be determined.
[0035] Conventionally, the test device illustrated is equipped with
more probes. For example, there may be more than two cross-members
provided, and a plurality of slides on each of these, so that a
large number of probes can be used.
[0036] Known test devices of the type shown in FIGS. 1 and 2 hold
the probes in a fixed position above the surface by means of the
probe drives 11, which are constructed as rigid holders in the
X-direction and the Y-direction. The drives provided in the
X-direction and the Y-direction have to be moved for each change of
location of one of the probe points. The test device illustrated is
very large and very heavy in the case of the traversing distances
required, for example 60 cm in the X-direction and 40 cm in the
Y-direction, and with the positioning accuracies of less than
{fraction (1/10)} mm required. High acceleration forces occur. The
traversing speeds are correspondingly low.
[0037] The probe drives 11 are provided in order significantly to
reduce the test speed, i.e. the average traversing speed of a
probe, between two places to be contacted on the circuit board 4.
This is explained in detail with reference to FIGS. 3 and 4.
[0038] The probe drive 11 is formed in a shaft 12 in the housing,
in the interior of which drives are provided for the needle 13,
which bears a contact point 32 as the probe at its bottom end.
[0039] First of all, a drive is provided for movement in the
X-direction and the Y-direction, i.e. in the plane of the circuit
board 4. It comprises a slide 15 movable in the X-direction in two
rails 14, and a slide 17 movable in the Y-direction in rails 16.
The linear drives provided in the X-direction and Y-direction in
this way are disposed one above the other with vertical spacing.
The slides are driven respectively by motors 18 and 19, which drive
the slides 15, 17 via revolving endless belts 20, 21 and drivers
22, 23.
[0040] Each of the slides 15 and 17 bears a gimbal mount in the
form of a ball 24 and 25 mounted for universal rotation in a
spherical recess in the slide. The needle 13 extends through a bore
in the balls 24 and 25 respectively so as to be longitudinally
displaceable.
[0041] The needle 13 can be brought into any desired pivoted
positions by movement of the slides 15 and 17 by means of the
motors 18 and 19 in the X-direction and Y-direction. The needle is
longitudinally displaceable in the gimbal mounts of the balls 24,
25. A vertical drive provides vertical movement.
[0042] In the exemplified embodiment illustrated, the vertical
drive comprises a motor 26 mounted on the housing shaft 12, said
motor pivoting an arm 28 in the direction of the arrow (FIG. 3) via
its output shaft 27. A pivoting arm 30 is mounted on the arm 28 by
means of a pivoting bearing 29, the top end of the needle 13 being
guided on the pivoting arm 30 by means of a plain bearing 31 shown
in the form of a ring.
[0043] When pivoted by the slides 15 and 17 in the X-direction and
Y-direction, the needle 13 is pivoted around the balls 24 and 25
respectively of the other slide, so that the top end of the needle
13 deflects correspondingly by means of the plain bearing 31. As a
result of the displaceability of the plain bearing on the pivoting
arm 30 and its pivotability about the pivoting bearing 20, the
vertical drive can allow the entire pivoting range of the top end
of the needle in permanent engagement.
[0044] If the contact point 32 at the bottom end of the needle 13
is required to occupy specific vertical positions, the vertical
drive illustrated must take into account the pivoted position of
the needle. This can be effected via appropriate computer control
of the motor 26 provided for the vertical drive, taking into
account the respective position of the slides 15 and 17 pivoting in
the X-direction and the Y-direction.
[0045] As shown in FIG. 3 in the bottom part of the drawing, the
needle 13 can, by its contact point 32, successively approach
connecting tags 33 of an IC 34 soldered on the circuit board 4.
[0046] With the test device shown in its entirety in FIGS. 1 to 4,
the circuit board 4 illustrated is tested with a test program which
optimises the distances traversed. The main drives comprising the
motors 9, 9', 10, 10' are used as little as possible. They
respectively move the probe drives 11 into a new position in which
these drives can very rapidly reach a very large number of points
by the much faster movement of the lightweight needle 13, the
points being, for example, the various connecting tags 33 of the IC
34 shown in FIG. 3.
[0047] FIGS. 5 and 6 show a basic constructional variant in which a
plurality of the probe drives 11 shown in FIGS. 3 and 4, namely, in
the exemplified embodiment, six drives, are secured to one another
in a fixed arrangement and are disposed by means of holders (not
shown) above a circuit board 35 for testing. The six probe drives
11 shown, for the probes constructed as needles 13, are in this
case stationary above the circuit board 35 during the test
operation. Only the needles 13 move by means of the drives
explained with reference to FIGS. 3 and 4, so that all the points
to be contacted on the circuit board 35 can be reached. A solution
of this kind is particularly suitable for smaller circuit
boards.
[0048] In a variant, for example, a line consisting of a plurality
of adjacent probe drives 11, as will be seen from the side in FIG.
6, are disposed in the form of a line on one of the cross-members
6, 6' of the test device shown in FIGS. 1 and 2. This line of probe
drives can be moved over the circuit board 4 by moving the
respective cross-member having the drive 5, 9; 5', 9' acting in the
X-direction.
[0049] A number of other variants are possible compared with the
embodiments illustrated. The probe drive 11 explained in FIGS. 3
and 4 comprises a vertical drive which moves the needle 13
vertically as a whole. Alternatively, as shown in FIG. 7, a needle
43 can carry a vertical drive 44 which moves the contact point 45
in the direction of the arrow relatively to the needle 43. The
vertical drive can thus be significantly accelerated by reducing
the vertically moving masses. The construction shown in FIGS. 3 and
4 is also simplified, since the vertical drive shown there is
dispensed with. The needle 13 then no longer has to be mounted for
longitudinal displacement in the two gimbal mounts, i.e. in the two
balls 24 and 25. It can be held to be longitudinally stationary in
one of the balls.
[0050] FIG. 8 shows another variant for the vertical drive. As
shown in FIGS. 3 and 4, the needle 13 is guided for longitudinal
displacement in the balls 24 and 25. It is driven vertically from
its top end, but with a different type of drive from that shown in
FIGS. 3 and 4.
[0051] As shown in FIG. 8, a probe 47 is supported relatively to
the slide 17 at the top end of the needle 13 by means of a coil
spring 48 and presses the needle 13 upwards. A plate 50 which is
vertically movable in parallel relationship by means of a drive
member 49 acts from above on the probe 47 and provides vertical
movement of needle 13 against the force of the spring 48.
[0052] At the same time the plate 50 may have on its underside a
recess 51 in the form of an ellipsoid cup, which is formed in two
radii adapted to the spacing around the balls 24 and 25. The
computing work for controlling the vertical drive motor 26 can thus
be reduced.
[0053] In the preferred embodiment illustrated, the probe drive is
in each case constructed as a needle pivoting drive. As shown by
FIG. 6, for example, this has the advantage that the probe at the
bottom end of the needle 13 can be moved beyond the base area of
the respective probe drive 11, i.e. to overlap between adjacent
probe drives. A comparison with FIG. 2 will show that the two probe
drives 11 can be traversed side by side laterally and operate in
overlapping relationship in the boundary zone.
[0054] Drives other than those illustrated can be used as the
needle pivoting drives. For example, the needle can be pivoted
about a central pivoting point by means of suitable drives. It can
also be mounted above the slides 15 and 17 shown in FIGS. 3 and 4
to be pivotable at a fixed point, for example at the location of
the bearing ring 31, i.e. at its top end. The slides 15 and 17 can
then engage the needle by slots extending parallel to their
rails.
[0055] It should also be noted that in this description, which is
limited to the mechanical control, the electrical connections to
the contact point 32 have been omitted. This is connected
electrically through the needle 13 to a connecting lead 52
extending to an electronic tester (not shown). Depending on the
test situation, in this tester the contact point 32 can be
connected to a measuring amplifier or a stimulus source, e.g. a
constant-voltage source or a constant-current source. Reference
should be made to the appropriate extensive literature in
connection with the appropriate test methods. For example, guard
tests or parasitic transistor tests can be carried out in
accordance with DE 41 10 551 C1.
[0056] Instead of the contact point 32 illustrated, which serves
for electrical contacting, the needle 13 shown in the embodiments
can also carry other probes, for example inductive or capacitive
sensors, which in the example of FIG. 3 are not contacted with the
tags 33, but brought into a specific spacing therefrom. The probes
may also, for example, be optical devices, such as cameras or
microscopes with a connected video camera, for high-resolution
observation. Devices of this kind can also be used particularly in
miniaturised form for testing integrated circuits on wafers.
[0057] Instead of the preferred needle pivoting drive for the probe
as shown in the drawings, other mechanical drives can also be used
as probe drives. For example, simple XY-drives, in which the
X-drive is mounted on the Y-drive, can be used, with which a test
point, for example in the form of a needle, can be moved in
parallel relationship. Drives which pivot in a plane in
superimposed relationship parallel to the circuit board for testing
can also be used.
[0058] The test device explained with reference to FIGS. 1 to 4 can
also be completed by an additional coarse vertical drive, by means
of which the probe drives 11 are held on the slides 7, 7'. The
drives may be slow vertical drives which are used only for special
cases, for example when unusual vertical movements are required
during the traversing of a larger component, where such vertical
movements cannot be provided by the vertical drives in the probe
drive 11.
* * * * *