U.S. patent application number 12/766101 was filed with the patent office on 2010-10-21 for methods for planarizing a semiconductor contactor.
This patent application is currently assigned to FormFactor, Inc.. Invention is credited to Benjamin N. Eldridge, Gary W. Grube, Gaetan L. Mathieu.
Application Number | 20100263432 12/766101 |
Document ID | / |
Family ID | 33539390 |
Filed Date | 2010-10-21 |
United States Patent
Application |
20100263432 |
Kind Code |
A1 |
Mathieu; Gaetan L. ; et
al. |
October 21, 2010 |
METHODS FOR PLANARIZING A SEMICONDUCTOR CONTACTOR
Abstract
A planarizer for a probe card assembly. A planarizer includes a
first control member extending from a substrate in a probe card
assembly. The first control member extends through at least one
substrate in the probe card assembly and is accessible from an
exposed side of an exterior substrate in the probe card assembly.
Actuating the first control member causes a deflection of the
substrate connected to the first control member.
Inventors: |
Mathieu; Gaetan L.;
(Varennes, CA) ; Eldridge; Benjamin N.; (Danville,
CA) ; Grube; Gary W.; (Pleasanton, CA) |
Correspondence
Address: |
N. KENNETH BURRASTON;KIRTON & MCCONKIE
P.O. BOX 45120
SALT LAKE CITY
UT
84145-0120
US
|
Assignee: |
FormFactor, Inc.
|
Family ID: |
33539390 |
Appl. No.: |
12/766101 |
Filed: |
April 23, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09527931 |
Mar 17, 2000 |
|
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12766101 |
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Current U.S.
Class: |
72/379.2 |
Current CPC
Class: |
G01R 1/07307 20130101;
G01R 3/00 20130101 |
Class at
Publication: |
72/379.2 |
International
Class: |
B21D 31/00 20060101
B21D031/00 |
Claims
1. A method of adjusting the planarity of a substrate in a probe
card assembly, the method comprising: deflecting at least one of a
first area of the substrate, a second area of the substrate, a
third area of the substrate, and a fourth area of the substrate;
said deflecting comprising applying a pulling force to said at
least one of said first, second, third, and fourth areas of the
substrate.
2-10. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a division of U.S. patent application
Ser. No. 09/527,931, filed Mar. 17, 2000 (pending). The foregoing
U.S. patent application Ser. No. 09/527,931 is incorporated herein
by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to a probe card
assembly, and more specifically to achieving a more planar
relationship between the contact elements on a probe card assembly
and a device under test.
[0004] 2. Background Information
[0005] Individual semiconductor devices (dies) are typically
produced by creating several identical devices on a semiconductor
wafer, using commonly known techniques such as photolithography and
deposition. Generally, these processes are intended to create fully
functional integrated circuit devices, prior to separating the
individual dies from the semiconductor wafer. However, physical
defects in the wafer and defects in the processing of the wafer
often lead to the presence of some defective dies on the wafer. it
is desirable to be able to identify the defective dies prior to
packaging or prior to their separation form the wafer. To perform
such identification, wafer testers or probers are used to make
pressure connections to connection pads (bond pads) on the dies.
The dies can then be tested for defects. A conventional component
of a wafer tester is a probe card which has contact elements that
effect the pressure connections to the bond pads of the dies.
[0006] A probe card can be part of a probe card assembly, such as
that which is described in U.S. Pat. No. 5,974,662, titled "Method
of Planarizing Tips of Probe Elements of a Probe Card Assembly,"
which is incorporated by reference herein. A probe card assembly
according to U.S. Pat. No. 5,974,662 typically includes a number of
components in addition to the probe card itself, such as in
interposer and a space transformer. The interposer is disposed
between the probe card and the space transformer and allows the
orientation of the space transformer to be adjusted relative to the
orientation of the probe card.
[0007] The space transformer permits a plurality of contact
structures on one side of the space transformer to make contact
with the terminals of an electronic component (e.g. bond pads on a
semiconductor device) at a relatively fine pitch, while connections
to another side of the space transformer are made at a relatively
coarser pitch. In a preferred embodiment, the contact structures
make contact with an active semiconductor device, such as a wafer.
Such connections can be disrupted by slight variations in the
planarity of the space transformer. Unfortunately, variations in
the planarity of the space transformer can occur, for example, when
the space transformer is manufactured. For example, an edge of the
space transformer might be bent slightly or the center of the space
transformer might be bowed.
[0008] FIG. 1 illustrates generally a prior art technique for
adjusting the orientation of a space transformer. A space
transformer 110 is shown with different sets of adjustment points
on the bottom of space transformer 110. In one example, the
adjustment points correspond to the locations of ball bearings that
can be pressed against a back surface of space transformer 110 to
adjust the orientation of space transformer 110. In FIG. 1, three
adjustment points 112a-112c are used to adjust the orientation of
space transformer 110. Adjustment points 112a-112c are located
along the periphery of space transformer 110.
[0009] The adjustment points shown in FIG. 1 can be used to deflect
peripheral areas of space transformer 110, but hey cannot be used
to deflect non-peripheral areas, such as the center, of space
transformer 110. The three points of adjustment shown in FIG. 1
define a plane which is approximately parallel to the plane of a
front surface of space transformer 110. However, because there are
only three adjustment points, they can adjust the orientation, but
not the shape, of space transformer 110; geometric changes are made
on only a low order (1.sup.st order polynomial). Furthermore, using
ball bearings in conjunction with the adjustment points provides
for the application of only a pushing force against space
transformer 110, and in some instances, the pushing force is
opposed by a spring member on an opposite side of space transformer
110.
[0010] In many instance, it is desirable to be able to apply a
pulling or pushing force at a multiplicity of locations on a space
transformer because the space transformer may require deflection or
distortion over its surface to achieve better planarity and correct
surface variations.
SUMMARY OF THE INVENTION
[0011] The present invention provides, in one embodiment, a method
of adjusting the planarity of a substrate in a probe card assembly,
in which the method includes deflecting at least one of a first
area of the substrate, a second area of the substrate, a third area
of the substrate, and a fourth area of the substrate, and the
deflecting includes applying a pulling force to at least one of the
first, second, third and fourth areas of the substrate.
[0012] The present invention provides, in another embodiment, a
method of achieving a degree of planarity among contact portions of
a plurality of contact structures mounted to a substrate, in which
the method includes creating the substrate with the plurality of
contact structures connected to a first surface of the substrate,
the contact portions of the contract structures having a first
planar relationship relative to one another, and applying a
plurality of forces selectively to the substrate to deform the
substrate and achieve a second planar relationship of the contact
portions of the contact structures relative to one another
[0013] Additional features and benefits of the present invention
will become apparent upon review of the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Various embodiment of the present invention will be
described in detail with reference to the following drawings in
which like reference numerals refer to like elements. The present
invention is illustrated by way of example and not limitation in
the accompanying figures. It should be noted that many of the
features shown in the figures have not been drawn to scale for the
purpose of better illustrating such features.
[0015] FIG. 1 illustrates generally a prior art technique for
adjusting the planarity of a space transformer in a probe card
assembly.
[0016] FIG. 2 illustrates a cross-sectional view of a probe card
assembly in accordance with the teachings of the present
invention.
[0017] FIGS. 3A and 3B illustrate generally deflections of a
substrate in a probe card assembly in accordance with the teachings
of the present invention.
[0018] FIG. 4A illustrated a bottomview of a probe card assembly in
accordance with the teachings of the present invention.
[0019] FIG. 4B illustrates a bottomview of a substrate in the probe
card assembly shown in FIG. 4A.
[0020] FIGS. 5A-5C illustrate different embodiments of a
planarizing element for a probe card assembly in accordance with
the teachings o the present invention.
[0021] FIG. 6 illustrates multiple adjustable substrates of a probe
card assembly.
[0022] FIG. 7A illustrates a top view of a multiple substrate
assembly in accordance with the teachings of the present
invention.
[0023] FIG. 7B illustrates a side view of the multiple substrate
assembly shown in FIG. 7A.
DETAILED DESCRIPTION
[0024] The following description provides embodiments of the
present invention. However, it will be appreciated that other
embodiments of the present invention will become apparent to those
of ordinary skill in the art upon examination of this description.
Thus, the present description and accompanying drawings are for
purposes of illustration and are not to be used to construe the
invention in a restrictive manner.
[0025] In a preferred embodiment of the present invention, a probe
card assembly includes a probe card, an interposer, a space
transformer, a drive plate and a first control member. The
interposer is located between the probe card and the space
transformer. The drive plate is located adjacent to the probe card.
A protrusion extends from a central area of the bottom surface of
the space transformer and through a through hole in the interposer.
The first control member is coupled to the protrusion and is
disposed within the through hole in the interposer and through
holes in the probe card and drive plate. The first control member
has an actuating component rotatably coupled to an end of the first
control member that is accessible from an exposed side of the drive
plate. A spring is supported by the actuating component to be urged
against the drive plate. As the actuating component is rotated and
moved toward the drive plate, the spring is pressed against the
drive plate and provides a resistance to the movement of the
actuating component. During this time, the space transformer is
pulled toward the interposer via the first control member coupled
to the protrusion extending from the space transformer. Thus, a
non-peripheral area of the space transformer is deflected according
to a preferred embodiment of the present invention.
[0026] FIG. 2 illustrates a side cross-sectional view of a probe
card assembly 200 in accordance with the teachings of the present
invention. A space transformer 210 is held down at its periphery by
a clamping frame 212. The top of space transformer 210 may be
substantially flush with the top of frame 212 such that a plurality
of resilient contact structures 211 extending from the top of space
transformer 210 can extend above the top surface of frame 212.
[0027] Contact structures 211 each have a contact region for making
contact with the terminals of an electronic component (e.g. bond
pads on a semiconductor device). In one embodiment, contact
structures 211 are freestanding, springable contact elements. It is
appreciated that other contact elements can be used in place of
contact structures 211. It is preferred that such elements are
sufficiently coupled to space transformer 210 to benefit from the
planarizing action associated with the present invention. For
example, posts, pins, pads, terminals and bumps/balls or other
contact elements known in the art can be used as contact
elements.
[0028] A clamping spring 214 (e.g. leaf spring) is couple to a
frame 218 by screws 216. Spring 214 secures frame 212. A printed
wiring board 220, such as probe card, is located beneath frame 218
and has a through hole in its center and through holes at points
around the center in a regular pattern. A drive plate 222, which
can also act as a stiffening substrate, is coupled to the bottom of
board 220. Drive plate 222 has a set of through holes which align
with the through holes in board 220. Screws 224 are placed in the
outer through holes in both board 220 and drive plate 222. Ball
bearings 226 rest on an end of screws 224 and are pressed against
space transformer 210 when screws 224 are screwed toward space
transformer 210.
[0029] An interposer 230 is located between space transformer 210
and board 220. Interposer 230 has a central through hole. Resilient
contact structures 229 extend from the top of interposer 230 and
effect pressure connections with contact pads 228 located on space
transformer 210. Resilient contact structures 231 extend from the
bottom of interposer 230 and effect pressure connections with
contact terminals 234 located on board 220. A threaded protrusion
or stud 238 extends from the bottom of space transformer 210. Stud
238 may be coupled to space transformer 210 or integrally formed
with space transformer 210. An extension stud 24C has a threaded
bore in one end which is screwed onto stud 238. The other end of
stud 240 is threaded and accommodates an actuating nut 242. Stud
240 is disposed through the central through holes of interposer
230, board 220 and drive plate 222. A spring element 244 (e.g.
Belleville washer) is supported by nut 242 and is pressed against
drive plate 222 as nut 242 is moved up stud 240.
[0030] It is appreciated that a plurality of resilient contact
structures can be provided on the bottom surface of a space
transformer (e.g. fabricated on the terminals on the bottom surface
of a space transformer) to make direct contact to the terminals on
the top surface of a printed wiring board. Thus, the use of an
interposer is optional. One alternative to an interposer is a
semi-rigid support member that backs a flexible sheet incorporating
contact structures. The semi-rigid support member, and hence the
flexible sheet and contact structures, can be planarized in
accordance with the teaching of the present invention. Other
alternatives to an interposer include flex tape, pogo pins and
other socket or interconnect constructions.
[0031] More detailed discussion of printed wiring boards (e.g.
probe cards), interposers, space transformers, drive plates,
resilient contact structures, contact elements and other components
of a probe card assembly that can be used in conjunction with the
present invention can be found in U.S. Pat. No. 5,974,662, U.S.
patent application Ser. No. 08/920,255, titled "Making Discrete
Power Connections to a Space Transformer of a Probe Card Assembly,"
now U.S. Pat. No. 6,050,829, and U.S. patent application Ser. No.
09/042,606, titled "Probe Card Assembly and Kit" now U.S. Pat. No.
7,064,566, all of which are incorporated by reference herein.
[0032] The planarity of space transformer 210 can be adjusted via
peripheral control members (e.g. screws 224 and ball bearings 226)
and a non-peripheral control member (e.g. stud 240 coupled to stud
238).
[0033] For example, screws 224 can be accessed from the bottom side
of drive plate 222 to drive them upward and force ball bearings 226
against space transformer 210. Because space transformer 210 is
held by frame 212 and spring 214, the contact of ball bearings 226
against space transformer 210 subjects space transformer 210 to
compressive forces. Thus, when ball bearings 226 are pressed
against space transformer 210, space transformer 210 deflects
accordingly. Because ball bearings 226 are located near the
periphery of space transformer 210, only peripheral areas of space
transformer 210 are adjusted via screws 224 and ball bearings 226.
Furthermore, because screws 224 are accessible from an exposed side
of drive plate 222, the planarity of peripheral areas of space
transformer 210 is remotely adjustable. It should be noted that
screws 224 and ball bearings 226 can be used to deflect space
transformer 210 without interfering with interposer 230.
[0034] A central area of space transformer 210 can be deflected
through the actuation of nut 242. As nut 242 is turned and moves up
extension stud 240, spring element 244 is pressed against drive
plate 222 by nut 242. Spring element 244 provides a resistance to
the upward movement of nut 242. Thus, as nut 242 is turned around
the threads of stud 240 and urged against spring element 244, stud
240 is pulled down. Because stud 240 is coupled to stud 238, the
area of space transformer 210 where stud 238 is located is also
pulled down along with stud 240. Thus, such area of space
transformer 210 is subjected to a pulling force or tensile force.
If space transformer 210 is bowed (e.g. domed), then stud 240 can
be pulled down through the actuation of nut 242 to adjust the
planarity of space transformer 210. It should be noted that because
nut 242 is accessible from an exposed side of drive plate 222, the
planarity of a non-peripheral area of space transformer 210 is
remotely adjustable. It should be further noted that studs 238 and
240 can be used to deflect space transformer 210 without
interfering with interposer 230.
[0035] Stud 238 can be located at a variety of positions on the
bottom surface of space transformer 210. For example, stud 238 can
be located near the center or the edge of the bottom surface of
space transformer 210. Thus, it is appreciated that the planarizing
apparatus of the present invention can be used to deflect
peripheral areas, as well as non-peripheral areas, of a substrate
in a probe card assembly. Furthermore, multiple studs can be used.
A space transformer can be configured to use a system in which as
many as all of the studs or other elements fixed to the space
transformer provide pushing and pulling forces through an actuating
mechanism to effect the desired deformation of a surface of the
space transformer.
[0036] Screws 224 and ball bearings 226 cannot be used to pull down
a central area of space transformer 210 because they are configure
to function with an opposing spring against space transformer 210.
The planarizing apparatus of the present invention addresses such a
deficiency as described above. Thus, the planarity of space
transformer 210 can be more thoroughly adjusted, particularly on a
higher order of adjustment (e.g. 2.sup.nd order polynomial,
3.sup.rd order polynomial, etc.), with the planarizing apparatus of
the present invention.
[0037] In addition to being able to adjust the planarity of space
transformer 210, the planarizing apparatus of the present invention
can be used to deflect space transformer 210 such that the contact
regions of contact structures 211 are planarized relative to one
another. The planarization of the contact regions of contact
structures 211 allows more uniform contact to be made with the
terminals of an electronic component to facilitate testing of the
electronic component. Furthermore, the deflection of space
transformer 210 can effect more uniform contact between contact
pads 228 and contact structures 229, and between terminals 234 and
contact structures 231.
[0038] FIGS. 3A and 3B illustrate generally a bowed substrate 310,
such as a space transformer, which is typically located in a probe
card assembly. If substrate 310 is bowed as shown in FIG. 3A then a
fore 332 (e.g. tensile force) which does not directly affect an
adjacent interposer 330 can be applied to substrate 310 to pull
substrate 310 into a desired position. Specifically, a central area
of substrate 310 can be deflected to a desired planarity. Such a
pulling force can be applied as previously described in conjunction
with FIG. 2. If substrate 310 is bowed as shown in FIG. 3B, then a
force 334 (e.g. compressive force) which does not affect interposer
330 can be applied to substrate 310 to push substrate 310 into a
desired position. Specifically, a central area of substrate 310 can
be deflected to a desired planarity. Such a pushing force can be
applied using an embodiment of the present invention as shown in
FIG. 5C.
[0039] FIG. 4A illustrates a bottomview of a probe card assembly
fitted with push-only control members 424, which are similar to
screws 224, and a push-pull control member 440, which is similar to
extension stud 240. A drive plate 422 is coupled to a probe card
420. Both drive plate 422 and probe card 420 have through holes to
accommodate control members 424 and 440. Control members 424 drive
ball bearings 426 at corresponding locations of a substrate 410, as
shown in FIG. 4B. Substrate 410, such as a space transformer, is
typically part of a probe card assembly such as that shown in FIG.
2. A stud 428 extending from the surface of substrate 410 is
coupled to central control member 440 to allow a central area of
substrate 410 to be deflected by the actuation of a nut 442
relative to control member 440. Control members 424 and 440 can be
drive independently to adjust the planarity of substrate 410 in a
variety of ways.
[0040] FIGS. 5A-5C illustrate various embodiments of a planarizing
apparatus according to the present invention. In FIG. 5A, a
substrate 510, such as a space transformer, has a stud 538a coupled
to or integrally formed with the bottom surface of substrate 510.
Stud 538a has a threaded bore to accommodate a connector 540a
having threaded ends. A nut 542 coupled to one of the threaded ends
of connector 540a supports a spring element 544a, which can be
pressed against a substrate (not shown), such as a drive plate, in
a manner similar to that described in conjunction with FIG. 2. The
actuation of nut 542 relative to connector 540a and the resulting
resistance provided by spring element 544a help drive connector
540a down, thereby deflecting substrate 510. Spring element 544a is
shown as a Belleville washer. It is appreciated that other springs
elements, such as coil springs and wavy washers could be used in
lieu of a Belleville washer. Furthermore, the spring element could
be built into the bottom of the drive plate.
[0041] In FIG. 5B, substrate 510 has a threaded stud 539b coupled
to or integrally formed with the bottom surface of substrate 510. A
connector 540b with a threaded bore is coupled to stud 538b. A nut
542 coupled to a threaded end of connector 540b supports spring
elements 544b-544d against a substrate (not shown), such as a drive
plate. Different spring elements can be used as spring elements
544b-544d to provide varying resistances to nut 542 as nut 542 is
twisted along the threads of connector 540b toward space
transformer 510.
[0042] In FIG. 5C, substrate 510 has a threaded stud 538c coupled
to or integrally formed with the bottom surface of substrate 510. A
connector 540c with a threaded bore is coupled to stud 539c. A
threaded end of connector 540c is coupled to a threaded through
hole in a substrate 522, such as drive plate. Connector 540c is
accessible from an exposed side of substrate 522, which is
typically an exterior substrate of a probe card assembly. Connector
540c can be turned clockwise or counter-clockwise to deflect
substrate 510 in opposite directions.
[0043] It should be noted that a multipoint adjustment scheme
according to the present invention can also be used to modify the
orientation (e.g. in x, y and .theta. directions) of a substrate in
a probe card assembly with respect to other substrates in the
assembly without interfering with the planarity or orientation of
such other substrates. Accordingly, a probe card assembly having
multiple deformable substrates may be constructed and made planar
across the surface defined by their contact elements with respect
to a test substrate, while appropriate positions of the contact
elements from substrate to substrate are maintained. Such an
assembly is shown generally in FIG. 6.
[0044] Multiple substrates 610, 620 . . . n are located adjacent to
one another in a combined assembly. Each substrate is adjustable
with respect to the other substrates in x, y and .theta. using
orienting mechanisms (not shown) well known in the art. A system
for deforming substrates in the z direction (out of the page) is
also included but is not shown. Such a system may incorporate
planarizing elements as disclosed herein. The vector r defines the
relationship between corresponding contact elements 610a, 620a . .
. z on multiple substrates 610, 620 . . . n, respectively.
Substrates 610, 620 . . . n are positioned with respect to one
another such that r is within a desired degree of accuracy, and
deformed such that the contact tips of contact elements 610a, 620a
. . . z are coplanar within a desired degree of accuracy in the z
direction.
[0045] Referring to FIGS. 7A and 7B, which provide more detailed
representations of a combined assembly having multiple substrates
similar to that shown in FIG. 6, contact elements 711 are secured
to insulating support member 705. Contact elements 711 are
electrically connected by trances 706 to connecting wires 715,
which are connected in turn to traces 713 and to tester 760.
Contact elements 711 are illustrated as solder balls but of course
can take many of the forms described herein. In one preferred
embodiment, connecting wires 715 are portions of a multi-stranded
flex cable. In another preferred embodiment, connecting wires 715
can be wirebonded connections. In still another preferred
embodiment, insulating support member 705 is polyimide, or other
flex materials well known in the art.
[0046] Substrate 704 supports insulating support member 705. In one
preferred embodiment, they are secured together. In another
preferred embodiment, they can be in close contact, but can move
relative to each other. Substrate 704 is positioned by a push-only
control element comprising actuator 730 acting on element 724 and
ball 726 to press against substrate 704, opposed by spring 712,
which in turn is secured to substrate frame 720. Several of these
push control elements can be used; two are shown in FIG. 7B for
illustrative purposes. Substrate 704 also is positioned by a
push-pull control element comprising actuator 732, element 740, and
stud 738, which is secured to substrate 704. Substrate frame 720 is
secured to substrate housing 722, which in turn is connected to
actuators 730, 732, forming a closed loop system. By selectively
positioning the actuators, the shape of substrate 704 can be
controlled.
[0047] Printed wiring board 750 supports housing 752, which is
connected to positioning element 756, which in turn is connected to
substrate housing 722 directly or, as shown, through bridge housing
754. Positioning element 756 is illustrated in stylized form and
can include elements as desired to provide x, y, z, and three
degrees of positional control over substrate housing 722.
[0048] FIG. 7B illustrates a second substrate 704a as well, with
elements as described above. Each substrate 704, 704a can be
adjusted to a desired degree of planarity. Equally well, each
substrate 704, 704a can be adjusted to a desired degree of flatness
of the contact region portion of each of contact elements 711.
Moreover, substrates 704 and 704A can be positioned relative to
each other to provide a relatively large array of contact elements
711.
[0049] Such a probe card assembly constructed of multiple
deformable substrates is functionally equivalent to a larger probe
card assembly having a much larger (equivalent in area) single
substrate. It is important to note that deformation of the
monolithic substrate in order to change the spatial relationship of
the contact elements residing on it is achieved both by deformation
and x, y, z and .theta. movement of the multiple substrates and
supporting structures in which they reside.
[0050] The planarizing apparatus of the present invention can be
manually actuated or automatically actuated. For example, an
actuator mechanism can be connected to a planarizing apparatus
(e.g. to the actuating nut) and operated according to signals from
a computer system. A greater number of control points driven by
such automated planarizing apparatuses can shape a substrate to a
higher degree of accuracy.
[0051] Although the present invention has been described with
particular reference to probe card assemblies and space
transformers in particular, it is appreciated that the present
invention is not so limited in its applications.
[0052] In the foregoing detailed description, the apparatus and
method of the present invention have been described with reference
to specific exemplary embodiments. However, it will be evident that
various modifications and changes may be made without departing
from the broader scope and spirit of the present invention. The
present specification and figures are accordingly to be regarded as
illustrative rather than restrictive.
* * * * *