U.S. patent number 3,743,148 [Application Number 05/121,886] was granted by the patent office on 1973-07-03 for wafer breaker.
Invention is credited to Heinz F. Carlson.
United States Patent |
3,743,148 |
Carlson |
July 3, 1973 |
WAFER BREAKER
Abstract
Presented is a machine for breaking a semiconductor wafer that
has been scribed into the individual dies described by the scribe
lines.
Inventors: |
Carlson; Heinz F. (Santa Cruz,
CA) |
Family
ID: |
22399370 |
Appl.
No.: |
05/121,886 |
Filed: |
March 8, 1971 |
Current U.S.
Class: |
225/2;
225/96.5 |
Current CPC
Class: |
H01L
21/67092 (20130101); Y10T 225/325 (20150401); Y10T
225/12 (20150401) |
Current International
Class: |
B26F
3/00 (20060101); B28D 1/00 (20060101); H01L
21/70 (20060101); B28D 5/00 (20060101); B28D
5/04 (20060101); H01L 21/78 (20060101); B26f
003/00 () |
Field of
Search: |
;225/2,93,96.5
;29/413 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Yost; Frank T.
Claims
Having thus described the invention, what is claimed to be novel
and sought to be protected by letters patent is as follows:
1. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines, the combination comprising:
a. platen means having a curved surface adapted to initially
support thereon a flat scribed wafer; and
b. non-resilient metal band means opposed to said platen initially
tangentially related to the curved surface thereof and
progressively conformable thereto by relative movement therebetween
perpendicular to the surface of said wafer whereby a flat scribed
wafer disposed between the curved surface of the platen and said
means conformable thereto is broken along said scribe lines.
2. The combination according to claim 1, in which the curved
surface on said platen means is curvilinear, said means opposed to
said platen constitutes a flexible band, and the linear dimension
of said curved surface extends transverse of said flexible
band.
3. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines cut in one surface thereof, the combination
comprising:
a. means having a curved surface adapted to initially engage in
line contact the side of a wafer remote from said scribe lines,
said line engagement extending substantially parallel to said
scribe lines; and
b. means adapted to engage in non-slipping surface contact the
initially flat scribed surface of a wafer the opposite side of
which is engaged in line contact by said means having a curved
surface;
c. said means in surface contact with the scribed surface of the
wafer comprising a non-resilient metal band progressively
conformable to said curved surface by movement perpendicular
thereto whereby said wafer is caused by said band to conform to
said curved surface to thereby break said wafer into portions
defined by said scribe lines.
4. The combination according to claim 3, in which said means having
a curved surface constitutes a platen movable from a flat wafer
loading position through successive wafer breaking positions in
which said wafer is made to conform to said platen and back to said
flat wafer loading position.
5. The combination according to claim 3, in which said means having
a curved surface constitutes a platen having a convex curvilinear
surface thereon, said means adapted to engage the flat scribed
surface of the wafer in surface contact constitutes a flexible band
spaced from said platen an amount sufficient to permit
interposition of said wafer therebetween, and means for effecting
wrapping of said band about the convex curvilinear surface of said
platen.
6. The combination according to claim 3, in which control means are
provided selectively operable to effect progressive conformability
of said means in surface contact with the scribed surface of the
wafer to said curved surface, and means disposed between said
curved surface means and said band means to retain said band means
from slipping in relation to said curved surface means.
7. The combination according to claim 3, in which said means having
a curved surface constitutes a platen, said means conformable to
the curved surface of said platen constitutes a flexible band, and
said apparatus includes a housing divided into a wafer-breaking
section and a power section, said platen and said band being
enclosed within said wafer-breaking section of the housing.
8. The combination according to claim 3, in which said means having
a curved surface comprises a platen, said means adapted to conform
to said curved surface comprises a flexible band, said apparatus
includes a frame on which said platen and said band are supported,
and means are provided on said frame connected to said platen and
said band and selectively operate to effect movement thereof to
conform said band to said curved surface.
9. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines, the combination comprising:
a. platen means having a curvilinear surface formed by lines
parallel to the Y axis in a three dimensional XYZ system of axes
and adapted to support thereon a wafer having scribe lines parallel
to at least said Y axis; and
b. tensioned strap means spaced from said curvilinear surface and
initially abuttable against the flat scribed surface of a wafer
disposed between said curvilinear surface and said tensioned strap
means, said tensioned strap means starting at said Y axis being
progressively conformable to portions of said curvilinear surface
lying on opposite sides of said Y axis to apply pressure
progressively to the side of said wafer opposite said curved
surface starting from said Y axis and progressing circumferentially
thereabout whereby said wafer is progressively broken first along
one of said scribe lines coincident with said Y axis and then
successively along pairs of said scribe lines formed by scribe
lines correspondingly spaced on opposite sides of said Y axis.
10. The method of breaking a semiconductor wafer scribed on one
side to provide two sets of parallel score lines disposed at right
angles to each other, comprising the steps of:
a. orienting a median scribe line of the wafer in supported
relation to a curved surface formed by straight lines extending
parallel to one set of said scribe lines including said median
scribe line; and applying pressure progressively to the side of
said wafer opposite said curved surface starting from said median
scribe line and progressively therefrom and thus causing said
initially flat unbroken wafer to progressively conform to said
curved surface by cinching the wafer progressively starting with
said median scribe line to said curved surface with a taut flexible
band whereby said wafer is stressed to effect breaking thereof
first along said median scribe line and thence progressively
simultaneously along scribe lines correspondingly spaced on
opposite sides of said median scribe line.
11. The method according to claim 10, in which tension is applied
to said flexible band to effect cinching thereof around said curved
surface.
12. The method according to claim 10, in which said curved surface
is curvilinear, the straight lines forming said curved surface
extending parallel to the Y axis of a system of XYZ axes, causing
said curved surface to move in the direction of said Z axis, and
tensioning said flexible band in the direction of said X axis while
retaining the band against slippage in relation to said wafer.
13. The method of breaking a semiconductor wafer scribed on one
side to provide two sets of parallel score lines disposed at right
angles to each other, comprising the steps of:
a. orienting the wafer in relation to an XYZ system of axes so that
one set of said scribe lines extends parallel to the X axis and the
other set of said scribe lines extends parallel to said Y axis;
b. applying pressure progressively to both sides of said wafer
along lines coincident with said scribe lines parallel to said Y
axis whereby said wafer is first broken along a median scribe line
parallel to said Y axis and thence progressively simultaneously
broken along scribe lines correspondingly spaced on opposite sides
of said Y axis;
c. removing the pressure from said wafer whereby the broken strips
of wafer reorient themselves in a flat attitude;
d. reorienting the wafer so that the other set of scribe lines lies
parallel to said Y axis; and
e. again imposing pressure progressively on both sides of said
wafer in the direction of said Z axis along lines coincident with
said scribe lines parallel to said Y axis to effect breaking of
said wafer strips along a median scribe line parallel to said Y
axis and thence progressively simultaneously along scribe lines
correspondingly spaced on opposite sides of said Y axis.
14. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines, the combination comprising:
a. platen means having a curved surface adapted to initially
support thereon a flat scribed wafer; and
b. means opposed to said platen initially tangentially related to
the curved surface thereof and progressively conformable thereto by
relative movement therebetween perpendicular to the surface of said
wafer whereby a flat scribed wafer disposed between the curved
surface of the platen and said means conformable thereto is broken
along said scribe lines;
c. said means opposed to said platen means comprising a taut band
resiliently anchored at each end, said platen means being movable
against said band in opposition to said resilient anchoring
means.
15. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines, the combination comprising:
a. platen means having a curved surface adapted to initially
support thereon a flat scribed wafer; and
b. means opposed to said platen initially tangentially related to
the curved surface thereof and progressively conformable thereto by
relative movement therebetween perpendicular to the surface of said
wafer whereby a flat scribed wafer disposed between the curved
surface of the platen and said means conformable thereto is broken
along said scribe lines;
c. said means opposed to said platen means constituting a flexible
band, means provided to tension said band, and means provided to
move said platen in opposition to said band to effect cinching of
said band about the curved surface of said platen means.
16. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines, the combination comprising:
a. platen means having a curved surface adapted to initially
support thereon a flat scribed wafer; and
b. means opposed to said platen initially tangentially related to
the curved surface thereof and progressively conformable thereto by
relative movement therebetween perpendicular to the surface of said
wafer whereby a flat scribed wafer disposed between the curved
surface of the platen and said means conformable thereto is broken
along said scribe lines;
c. said means opposed to said platen means constituting a band,
said platen means being movable relative to said band, and
pneumatic circuit means including a pair of air cylinders provided
to impose tension on said band in opposition to movement of said
platen means thereagainst.
17. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines, the combination comprising:
a. platen means having a curved surface adapted to initially
support thereon a flat scribed wafer; and
b. means opposed to said platen initially tangentially related to
the curved surface thereof and progressively conformable thereto by
relative movement therebetween perpendicular to the surface of said
wafer whereby a flat scribed wafer disposed between the curved
surface of the platen and said means conformable thereto is broken
along said scribe lines;
c. said means opposed to said platen means comprising a flexible
band, and control means provided to effect progressive
conformability of said band to the curved surface of said platen
means so as to cinch a wafer interposed therebetween into
conformity with the curvature of said platen means, said control
means including an air cylinder operable to effect movement of said
platen means, a pair of air cylinders attached to opposite ends of
said flexible band to impose tension thereon, pressure regulator
means for controlling the pressure in said air cylinders, valve
means for controlling release of air under pressure to the air
cylinder controlling movement of said platen means, and valve means
actuated by said platen means upon completion of a predetermined
excursion and effective to reverse the cycle to return the platen
means to a wafer loading position and release tension on said
flexible band.
18. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines cut in one surface thereof, the combination
comprising:
a. means having a curved surface adapted to engage in line contact
the side of a wafer remote from said scribe lines, said line
engagement extending substantially parallel to said scribe lines;
and
b. means adapted to engage in surface contact the flat scribed
surface of a wafer the opposite side of which is engaged in line
contact by said curved surface;
c. said means in surface contact with the scribed surface of the
wafer being progressively conformable to said curved surface by
movement perpendicular thereto whereby said wafer is caused to
conform to said curved surface to thereby break said wafer into
portions defined by said scribe lines;
d. said means having a curved surface adapted to engage said wafer
in line contact comprising a platen having a curvilinear surface
thereon, said means adapted to engage the flat scribed surface of a
wafer in surface contact comprising a taut flexible band disposed
adjacent said curved surface of the platen whereby wrapping of said
band about said platen effects breaking of said wafer first along a
median scribe line and thence progressively simultaneously along
scribe lines correspondingly spaced on opposite sides of said
median scribe line.
19. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines cut in one surface thereof, the combination
comprising:
a. means having a curved surface adapted to engage in line contact
the side of a wafer remote from said scribe lines, said line
engagement extending substantially parallel to said scribe
lines;
b. means adapted to engage in surface contact the flat scribed
surface of a wafer the opposite side of which is engaged in line
contact by said curved surface;
c. said means in surface contact with the scribed surface of the
wafer being progressively conformable to said curved surface by
movement perpendicular thereto whereby said wafer is caused to
conform to said curved surface to thereby break said wafer into
portions defined by said scribe lines; and
d. a pneumatic circuit including a plurality of selectively
operable air cylinders, a pair of said air cylinders being
connected to said flexible band and another of said cylinders being
connected to said platen, and valve means for actuating said
cylinder connected to said platen to effect movement of said platen
in opposition to said band.
20. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines cut in one surface thereof, the combination
comprising:
a. means having a curved surface adapted to engage in line contact
the side of a wafer remote from said scribe lines, said line
engagement extending substantially parallel to said scribe lines;
and
b. means adapted to engage in surface contact the flat scribed
surface of a wafer the opposite side of which is engaged in line
contact by said curved surface;
c. said means in surface contact with the scribed surface of the
wafer being progressively conformable to said curved surface by
movement perpendicular thereto whereby said wafer is caused to
conform to said curved surface to thereby break said wafer into
portions defined by said scribe lines;
d. said apparatus including a housing having a wafer-breaking
section and a power section, and wafer support means are provided
associated with said wafer-breaking section of the housing operable
to support said wafer in said wafer-breaking section between said
means having a curved surface and said means conformable
thereto.
21. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines, the combination comprising:
a. platen means having a curvilinear surface formed by lines
parallel to the Y axis in a three dimensional XYZ system of axes
and adapted to support thereon a wafer having scribe lines parallel
to at least said Y axis;
b. strap means spaced from said curvilinear surface and initially
abuttable against the flat scribed surface of a wafer disposed
between said curvilinear surface and said strap means, said strap
means being progressively conformable to portions of said
curvilinear surface lying on opposite sides of said Y axis whereby
said wafer is progressively broken first along one of said scribe
lines coincident with said Y axis and then successively along pairs
of said scribe lines formed by scribe lines correspondingly spaced
on opposite sides of said Y axis; and
c. means to impose tension on said strap means and for effecting
movement of said strap means to effect progressive conformability
of said strap means to said curvilinear surface.
22. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines, the combination comprising:
a. platen means having a curvilinear surface formed by lines
parallel to the Y axis in a three dimensional XYZ system of axes
and adapted to support thereon a wafer having scribe lines parallel
to at least said Y axis; and
b. strap means spaced from said curvilinear surface and initially
abuttable against the flat scribed surface of a wafer disposed
between said curvilinear surface and said strap means, said strap
means being progressively conformable to portions of said
curvilinear surface lying on opposite sides of said Y axis whereby
said wafer is progressively broken first along one of said scribe
lines coincident with said Y axis and then successively along pairs
of said scribe lines formed by scribe lines correspondingly spaced
on opposite sides of said Y axis;
c. said apparatus including a housing including an intermediate
support wall dividing said housing into a wafer-breaking section
and the power section, said platen means and said strap means being
enclosed within said wafer-breaking section, and power means
provided within said power section and connected to said platen
means and strap means to tension said strap and effect movement
thereof to progressively conform the strap means to said platen
means.
23. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines, the combination comprising:
a. platen means having a curvilinear surface formed by lines
parallel to the Y axis in a three dimensional XYZ system of axes
and adapted to support thereon a wafer having scribe lines parallel
to at least said Y axis;
b. strap means spaced from said curvilinear surface and initially
abuttable against the flat scribed surface of a wafer disposed
between said curvilinear surface and said strap means, said strap
means being progressively conformable to portions of said
curvilinear surface lying on opposite sides of said Y axis whereby
said wafer is progressively broken first along one of said scribe
lines coincident with said Y axis and then successively along pairs
of said scribe lines formed by scribe lines correspondingly spaced
on opposite sides of said Y axis; and
c. control means for controlling movement of said strap means and
platen means, said control means including a pneumatic circuit
having a plurality of air-actuated cylinders therein, one of said
cylinders being operatively connected to said platen means, and a
pair of said cylinders connected to opposite ends of said strap
means whereby each cylinder acts in opposition to the other
cylinders.
24. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines, the combination comprising:
a. platen means having a curvilinear surface formed by lines
parallel to the Y axis in a three dimensional XYZ system of axes
and adapted to support thereon a wafer having scribe lines parallel
to at least said Y axis;
b. strap means spaced from said curvilinear surface and initially
abuttable against the flat scribed surface of a wafer disposed
between said curvilinear surface and said strap means, said strap
means being progressively conformable to portions of said
curvilinear surface lying on opposite sides of said Y axis whereby
said wafer is progressively broken first along one of said scribe
lines coincident with said Y axis and then successively along pairs
of said scribe lines formed by scribe lines correspondingly spaced
on opposite sides of said Y axis; and
c. a frame, said platen means and strap means being supported on
said frame, and wafer support means mounted on said frame and
selectively operable to insert an unbroken wafer between said
platen means and said strap means and to withdraw said wafer
therefrom after it has been broken.
25. In an apparatus for breaking a flat semiconductor wafer along
predefined scribe lines, the combination comprising:
a. platen means having a curvilinear surface formed by lines
parallel to the Y axis in a three dimensional XYZ system of axes
and adapted to support thereon a wafer having scribe lines parallel
to at least said Y axis; and
b. strap means spaced from said curvilinear surface and initially
abuttable against the flat scribed surface of a wafer disposed
between said curvilinear surface and said strap means, said strap
means being progressively conformable to portions of said
curvilinear surface lying on opposite sides of said Y axis whereby
said wafer is progressively broken first along one of said scribe
lines coincident with said Y axis and then successively along pairs
of said scribe lines formed by scribe lines correspondingly spaced
on opposite sides of said Y axis;
c. said apparatus including a frame, said platen means and strap
means being supported on said frame, a wafer support assembly
mounted on said frame for supporting a wafer oriented so that a
selected set of scribe lines thereon lie parallel to said Y axis,
said wafer support means including a feed slide movable to carry a
properly oriented wafer between said platen means and said strap
means, said strap means extending in the direction of said X axis,
means associated with said strap means for imposing tension on said
strap means in the direction of said X axis, means associated with
said platen means for effecting movement of said platen in the
direction of said Z axis whereby said strap means is caused to be
wrapped around the curvilinear surface of said platen means to
effect progressive breaking of said wafer along a first set of
scribe lines, and means associated with said feed slide to effect
rotation of said wafer by approximately 90.degree. so as to
reorient the wafer with the unbroken set of scribe lines parallel
to said Y axis.
Description
BACKGROUND OF INVENTION
With the advent of microminiature electronics such as integrated
circuits in which the semiconductor chip forming the integrated
circuit is so small as to create problems in handling the chip, one
of the problems has been in producing the chip in the first place.
One of the methods that is commonly used is to manufacture a wafer
of relatively large size, individual areas of the wafer including
the separate integrated circuits being defined by scribe lines cut
into one surface of the wafer in a grid pattern comprising sets of
parallel lines at right angles to each other. Such scribe lines are
usually no more than scratches having a depth of approximately
0.001 of an inch and a width as narrow as can be provided by
appropriate cutting means such as a diamond scribe or a laser.
Wafers from which semiconductor chips are cut to provide integrated
circuit components or semiconductor dies come in various sizes in
various thicknesses. In general, however, it is necessary to break
the wafer into individual "chips" of much smaller size. Frequently,
individual chips or dies constituting a complete integrated circuit
are no more than 0.025 to 0.050 of an inch in transverse dimension,
with a thickness of perhaps 0.010 or 0.012 of an inch. Under these
circumstances, it will be appreciated that it is extremely
difficult to break the wafer along the scribe lines without
cracking the chips or dies in areas which render them useless. In
general, it has been found that conventional wafer breaking
equipment results in a loss factor of from 30 percent to 50 percent
of the possible dies which could be secured from one wafer.
DESCRIPTION OF THE PRIOR ART
Because of the existence of this problem, many attempts have been
made to produce apparatus that would effectively break wafers into
the individual dies. One such apparatus is taught by U.S. Pat. No.
3,040,489. That patent teaches the conventional method of packaging
a scribed wafer in an appropriate plastic envelope so as to protect
the surfaces thereof from contamination. The enclosed and scribed
wafer is then fastened to the surface of a table having a resilient
pad upon which the enclosed wafer packet is placed. The table is
movable so as to carry the wafer beneath a roller which imposes a
downward pressure on the enclosed wafer as the wafer passes
thereunder, causing the wafer to crack along the scribed lines. It
should be noted that this apparatus causes one peripheral edge of
the wafer to be first fed beneath the roller, with the roller
successively imposing pressure on individual scribe lines as the
wafer progresses from one peripheral edge thereof to the other
beneath the roller. When the wafer has been cracked in one
direction, the table is removed, replaced in a position 90.degree.
to its previous position, and the sequence of operation is repeated
so as to break the wafer in the opposite direction. It will be
apparent that this apparatus depends for its operation upon
placement of the enclosed wafer upon the resilient support which is
deformed by the downward pressure exerted by the roller. The axis
of the roller must, of course, be parallel to the scribe lines, and
the wafer is broken along each scribe in turn as the roller passes
thereover.
Another attempt to crack wafers into separate dies is taught by
U.S. Pat. No. 3,105,623. In all essential points, this patent
depends for its operation upon the same principal described with
respect to U.S. Pat. No. 3,040,489, i.e., placement of a scribed
wafer on a resilient base which is then carried beneath a roller to
apply pressure progressively across the wafer from one peripheral
edge to the other so as to break the wafer in turn at each scribe
line over which the roller passes.
U.S. Pat. No. 3,149,765 teaches an apparatus in which a scribed
wafer is arranged in a feed channel provided with a push rod which
successively advances the wafer by predetermined increments to
bring a strip of the wafer defined by a pair of scribe lines into
position so that the entire strip may be individually broken from
the main body of the wafer. The strips so broken away are then
pushed out of the way by a second push rod and main body of the
wafer is again advanced and the operation repeated. As each
individual strip is moved out of the path of the remaining main
wafer portion, each chip in each individual strip is then caused to
register with an appropriate opening in a rotatable platen where it
is broken from the strip and carried away foe further
processing.
A departure from the apparatus described in the previous patents is
taught by U.S. Pat. No. 3,167,228. This patent, briefly, teaches
the utilization of a resilient spherical surface having a radius of
curvature complementary to the radius of curvature of a concave
fixed platen against which the resilient spherical surface is
adapted to abut. A conventionally enclosed and scribed wafer is
supported on the convexly curved resilient surface in a point
contact and the resilient convex surface is projected upwardly so
that it is brought into conformity with the concave complementary
fixed platen. As the two curved surfaces approach each other, it
will be apparent that the outer peripheral edges of the wafer
contact the depending peripheral edges of the concave platen, while
the convex surface on which the wafer is supported imposes an
upwardly directed force on the exact center of the wafer. Because
of the spherically curved surface of the resilient pad on which the
wafer is supported, it is proposed by the patent that the wafer is
broken in both directions in a single operation.
U.S. Pat. Nos. 3,206,088 and 3,396,452 both teach the concept of
placement of an appropriately scribed and packaged wafer on a
deformable base and the application of pressure to the top side of
the wafer by pressure devices of various kinds, including
cylindrical rollers, or a breaking tool having a polygonal cross
section so as to apply pressure to the wafer in the vicinity of
each scribe line, causing it to be deformed into the deformable
base member and broken along the scribe line. The latter U.S. Pat.
No. (3,396,452) adds the refinement of converting the relatively
flat deformable base member taught by the previous patents into a
cylindrical deformable support rotating in unison with a pressure
roller and between which the enclosed wafer is fed. Again, breaking
of the wafer depends upon deformation of the cylindrical deformable
roller in the vicinity of each succeeding scribe line commencing
with a scribe line next adjacent the outer periphery of the
wafer.
Additional methods and apparatuses for breaking wafers are taught
in U.S. Pat. No. 3,461,537, which teaches packing the wafer in a
vacuum-tight envelope prior to application of pressure to break the
wafer, U.S. Pat. No. 3,507,430, the main thrust of which is
directed to a snapping tool adapted to snap a scribed wafer into
separate parts, and U.S. Pat. No. 3,537,169 which also teaches the
concept of applying pressure to the backside of a scribed wafer,
causing it to be deformed into a deformable support member and thus
broken along the separate scribe lines. This patent adds the
refinement to the teaching of previous patents that includes
attachment of the wafer to a foil responsive to application of heat
to effect separation of the dies once broken.
With few exceptions, as indicated by the prior art discussed above,
most wafer breaking devices utilize the concept of a deformable and
resilient base upon which a wafer is supported so that the scribed
side of the wafer faces the deformable base. Pressure is then
applied by an appropriate roller to the back side of the wafer,
causing the deformable base below the wafer to be deformed
maximally along one of the scribe lines, thus causing cracking or
breaking of the wafer along that scribe line. It is believed that
the use of such a deformable base in the cracking or breaking
procedure of wafers contributes importantly to the high percentage
of rejects of dies secured from wafers. Accordingly, it is one of
the principal objects of the present invention to provide a wafer
breaking apparatus that eliminates the use of a deformable
base.
With the exception of U.S. Pat. No. 3,167,228, it appears that most
prior art devices operate by a mode which results in cracking the
wafer along separate scribe lines in individual operations. In
other words, it does not appear that prior art devices for breaking
wafers are capable of breaking the wafer along more than one scribe
line at a time. Accordingly, it is another object of the invention
to provide a wafer breaking device which initially breaks the wafer
along a scribe line lying in a median plane, and subsequently,
simultaneously breaks separate strips from the separate halves of
the wafer.
Another object of the invention is the provision of a wafer
breaking device which utilizes a non-resilient platen upon which
the wafer to be broken is supported, and the imposition thereon of
variable pressure by a non-resilient member which progressively
conforms its configuration and the configuration of the wafer to
the configuration of the platen.
It has been found that when a wafer is caught between two
non-deformable surfaces, one of which is flexible but
non-deformable, and the wafer is caused to conform to the curved
surface of one of the members, the percentage of rejects drops to
approximately one-half to 1 per cent. Accordingly, it is another
object of the invention to provide a wafer breaking device in which
a non-resilient curved platen is utilized to initially support an
unbroken wafer, which is subsequently caused to conform to the
curved surface of the platen by a taut steel band.
As indicated above, diameters and thicknesses of wafers differ.
Also, the sizes of the dies to be broken from such wafers differ.
Such variations in diameter, thicknesses and die size require the
imposition of different pressures to effect adequate breaking along
the scribe lines. Accordingly, it is a still further object of the
invention to provide a wafer breaking device in which the pressure
applied to break the wafer may be varied in accordance to the
special characteristics of the wafer being broken.
Another characteristic noted of wafer breaking devices of the prior
art is that most of such devices are not portable. Accordingly,
another and important object of the invention is to provide a wafer
breaking apparatus which weighs approximately 50 pounds, and which
is completely portable and may be operated either pneumatically,
hydraulically, electrically, mechanically, or
electromechanically.
SUMMARY OF THE INVENTION
In terms of broad inclusion, the wafer breaking device of the
invention comprises a platen having a curved surface, in one aspect
of the invention the curve being curvilinear, and on which the
unbroken wafer is adapted to be supported. Preferably, the platen
is movable between a first loading position and a breaking position
by any suitable means such as the ram in an air cylinder. Opposed
to the platen, and adapted to initially abut against the flat
surface of the unbroken wafer, is a flat section of a tensioned
band, preferably steel but formable from other materials, and which
is adapted to conform itself to the curvature of the underlying
platen as the platen advances from its loading position to the
wafer breaking position. The steel band may be tensioned by any
suitable means such as air cylinders having appropriate rams
connected to opposite ends of the steel band, with tension being
applied to the band by admitting air under pressure behind a piston
in each air cylinder. Obviously, other means of tensioning the band
may be utilized. Since the initial contact of the unbroken wafer
with the tensioned band constitutes a flat surface-to-surface
contact, it will be apparent that application of pressure by the
non-resilient underlying platen will cause fracture of the wafer
along a scribe line lying in a median plane of the wafer, thus
initially breaking the wafer into two separate and equal halves.
Continued movement of the platen in opposition to the tension band
causes the band to progressively conform itself to the curvature of
the underlying platen, causing opposing halves of the wafer to
fracture along pairs of corresponding scribe lines, succeeding
breaks progressing from the center of the wafer outwardly toward
the peripheral edges. Thus, in one operation, assuming a
curvilinear platen, the wafer is initially broken into individual
strips collectively arranged to conform to the curvature of the
underlying platen and the superposed tensioned band.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical cross-sectional view of one embodiment of the
invention, portions of the structure being in elevation for
clarity.
FIG. 2 is a plan view of the device the top plate being removed to
disclose the underlying structure.
FIG. 3 is a vertical cross-sectional view generally taken in the
plane indicated by the line 3--3 in FIG. 2, portions of the
structure being shown in elevation for clarity.
FIG. 4 is a fragmentary vertical sectional view illustrating the
feed and rotating apparatus for the wafer.
FIG. 5 is a plan view of the feed mechanism illustrated in FIG.
4.
FIG. 6 is a front elevational view of the wafer feed and rotating
mechanism.
FIG. 7 is a fragmentary sectional view taken in the plane indicated
by the line 7--7 of FIG. 1.
FIG. 8 is a schematic view of the control circuit for a
pneumatically operated wafer breaking device.
FIG. 9 is a plan view illustrating the scribed face of a wafer, the
scribe lines being spaced apart a considerable distance for
purposes of clarity.
FIG. 10 is a plan view illustrating the wafer of FIG. 9 mounted in
a flexible wafer carrier adapted to be used in conjunction with the
apparatus illustrated in FIGS. 1-3.
FIG. 11 is a schematic view in perspective illustrating the effect
on the wafer of forcing it to conform to the curvilinear surface of
the platen on which it is supported.
FIG. 12 is a schematic perspective view of the same wafer rotated
to 90.degree. and caused to conform to the curvilinear surface of
the platen in accordance with this invention.
FIG. 13 is a schematic view in cross section indicating the
relationship between the non-resilient underlying curvilinear
platen, the unbroken scribed wafer contained in its carrier, and
the superposed tensioned flat section of the steel band illustrated
in FIG. 1.
FIG. 14 illustrates schematically the first break that is made
along a scribe line in the wafer lying in a median plane so as to
divide the wafer into two equal and opposed halves.
FIG. 15 is a schematic view in cross section illustrating the
breaking simultaneously of two separate strips from the two opposed
halves upon progressive conformation of the tensioned steel band to
the curvature of the underlying platen.
FIG. 16 is a view similar to FIG. 15 and illustrates the manner in
which the next two strips are simultaneously broken from opposed
major wafer sections upon continued conformation of the tensioned
steel band to the curvature of the underlying platen.
FIG. 17 is a diagrammatic view illustrating the curvilinear platen,
the wafer and the tensioned steel band in relation to a system of
XYZ axes.
FIG. 18 is a diagrammatic view illustrating the curvilinear platen
in relation to the tensioned steel band superposed thereover and
the directions in which the platen moves and the direction in which
tension is applied to the steel band.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the interest of brevity in this description, the wafer breaking
apparatus of the invention will be described as a pneumatically
operated device, as opposed to any of the other several ways in
which it may be operated, namely, hydraulic, electrical,
electromechanical and mechanical.
Referring to FIG. 1, the pneumatically operated embodiment of the
invention is designated generally by the numeral 2 and includes a
housing formed by top wall 3, bottom wall 4, rear wall 6, and front
wall 7. Approximately midway between the top and bottom walls,
there is provided a transversely extending horizontal intermediate
wall 8, the ends of which are provided with outwardly extending
sections 9 and 12 inclined to the intermediate wall 8 at
approximately 45.degree. and secured thereto by appropriate screws.
As indicated best in FIG. 1, the front and back walls in general
follow the outline provided by the laterally extending upwardly
inclined intermediate wall extensions 9 and 12.
The section of the housing above the intermediate wall 8 may be
categorized as the wafer breaking section, while the section of the
housing below the intermediate wall 8 may be categorized as the
power section. As shown, the end edges or sides of the housing are
closed by side plates 13 and 14 associated with the wafer breaking
section of that housing, and side plates 16 and 17 associated with
the power section of the housing. In general, the front and rear
walls follow the configuration of the side walls so as to form a
completely enclosed two-chamber housing in one chamber of which is
effected the cracking or breaking of the wafer and in which is
included a minimum of control or power components, thus maintaining
this section of the housing relatively free from contaminants,
while the power section of the housing is isolated from the wafer
breaking section, and contains most of the control and operating
components.
Suitably mounted on the intermediate wall 8, here shown as being
specifically mounted on the upwardly inclined extensions 9 and 12
of such intermediate wall, are a pair of pneumatic cylinders, each
preferably being of the type that accommodates a nose-type mounting
secured to the associated transverse wall section by an appropriate
nut 21, having an extensible shaft 22 connected interiorly of the
cylinder to an appropriate air driven piston 23. Each air cylinder
is provided with a port 24 in the usual manner which admits air
under pressure above the piston, tending to drive the piston into
its lower or retracted position. The volume of the cylinder behind
the piston is vented to the outside air through appropriate exhaust
ports 26 formed either in the end wall as shown or in a side wall
of the cylinder.
The shaft 22 of each air cylinder is provided with clevis 27, in
which is pivotally mounted a bracket 28 in the nature of a U-shaped
clamp having transversely extending apertures therethrough and
within which opposite ends 29 of a tensioned steel band 29 may be
caught.
As clearly shown in FIG. 1 the steel band 29 passes over a pair of
laterally spaced rollers 31 journaled on an appropriate axle 32
extending horizontally between the front and back walls of the
housing. Each of the rollers is provided with a central body
section 33 defined by upstanding flanges 34 adjacent opposite ends
of the rollers. It will thus be seen that as the band 29 passes
over the rollers and is supported on the body section 33 thereof,
the upstanding flanges provide a guide and a limit for the edges of
the band, preventing displacement of the steel band in a fore and
aft direction. In the embodiment illustrated, the steel band is
provided with an aperture 36 (FIG. 2) adjacent one edge thereof and
the steel band is preferably fabricated from stainless steel having
a thickness of approximately 0.010 of an inch. The width of the
bank in the embodiment illustrated is preferably approximately 31/4
inches. It is important to note that the working section 36 of the
band in the attitude illustrated in FIG. 1 is horizontal across the
housing, and tangent to the upper periphery of the two spaced
rollers 31. It is important that irrespective of the attitude of
the working section 36', that the end portions of the steel band
connected to clevises 27 extend tangentially from each of the
associated rollers. In this manner, there is never imposed on the
shafts 22 a transverse loading which would have the tendency to
wear seals and bearings.
It should be noted that while the air cylinders 18 and 19 have been
illustrated and described as mounted on the obliquely extending
wall sections 9 and 12, such cylinders could just as easily be
mounted on the intermediate wall section 8 within the lower power
section of the housing. In such event, the housing would be more
rectangular in its configuration, the inclined end walls 13 and 14
being in such an embodiment a continuation of the side walls 16 and
17.
Mounted in the power section of the housing below the intermediate
wall 8 is a power cylinder 41 having a threaded nose section 42
extending through an appropriate aperture 43 in the intermediate
wall 8 and being detachably secured thereto by appropriate nut 44
as shown. The power cylinder 41 in the embodiment illustrated is
preferably a pneumatic double-acting type in which air under
pressure may be admitted selectively to opposite sides of a piston
46 appropriately connected to a shaft 47 the outer end 48 of which
extends above the intermediate wall 8 into the wafer breaking
section of the housing and is equipped with a threaded end portion
49 engaging a complementarily threaded interior bore formed in the
mounting sleeve 51 locked to the threaded section of the shaft by a
nut 52. The upper end of the mounting section 51 is provided with a
reduced-in-diameter stub shaft portion 53 which at its union with
the larger diameter mounting portion 51 provides a shoulder 54 on
which is detachably supported a platen designated generally by the
numeral 56.
The platen 56 in the embodiment illustrated is provided with
vertical end walls 57 extending parallel and spaced from the
adjacent front and back walls of the housing. The platen is
preferably in the form of a solid non-deformable steel block having
a curvilinear surface 58, chrome plated for extreme smoothness and
hardness for reasons which will hereinafter be explained. It is
important that the platen 56 not rotate on the stub shaft 53. To
prevent such rotation, the stub shaft 53 may, of course, be formed
with a cross section that would prevent such rotation, and the
shaft 48 of the air cylinder may be appropriately keyed so that it
does not rotate. However, in the interest of fabricating an
economical unit, it is advantageous that the double-acting cylinder
41 not be of such special construction as to increase its cost.
Accordingly, to prevent rotation of the platen 56, about the
vertical axis of the shaft 48, stop blocks 59 and 59' are mounted
securely to the back wall 6 of the housing by appropriate means
such as screws, and the associated end wall 57 of the platen is
associated with the faces of such stop blocks so as to absorb any
rotary moment that might be imposed on the platen.
As discussed above, it is important that there be no fore and aft
displacement of the band 29 and to prevent such displacement, each
of the spools 31 is provided with the upstanding flanges 34. It is
equally important that there be no longitudinal displacement of the
band in relation to the underlying platen while permitting the
flexure of the band to conform to the curvature of the curvilinear
surface 58 thereof. To prevent such longitudinal displacement of
the band, the platen is provided with an upstanding pin 61 adjacent
one end of the platen and positioned so as to protrude snugly
through the aperture 36 (FIG. 2). It will thus be seen that when
the power cylinder 41 is activated as will hereinafter be
explained, the platen 56 moves upwardly along the axis of the power
cylinder, and after a very short travel abuts the underside of the
working section 36 of the steel band. Thereafter, continued upward
movement of the platen causes the midsection of the band to move
upwardly with the platen, which in turn causes the band to closely
conform to the curvature of the upper curvilinear surface 58 of the
platen. It should be noted that such conformation is progressive,
starting at the axis of the platen and progressively increasing as
the platen moves upwardly.
In the device illustrated, the main power cylinder 41 constitutes a
double-acting cylinder manufactured by the Bimba Manufacturing
Company, Monee, Ill., and sold under the model No. 503-D. Air
cylinders 18 and 19 are manufactured by the same company and carry
a model No. 311-D. It has been found appropriate through
experimentation that a pressure of approximately 100 psi imposed on
the upper side of the piston 23 in each of the air cylinders 18 and
19 through their respective inlet ports 24 produces satisfactory
results for most wafer sizes and thicknesses. As will hereinafter
be explained, such pressure may be increased or decreased through
appropriate means. It is preferable that the tension imposed on the
steel band 29 by cylinders 18 and 19 be closely matched to the
pressure exerted by the main power cylinder 41. Accordingly, the
effective areas of the pistons in the auxiliary cylinders 18 and 19
are proportioned to equal the effective area of the piston 46 of
the main power cylinder 41.
In the embodiment illustrated, a semiconductor wafer 62,
illustrated in plan in FIG. 9, is provided with a first set of
scribe lines 63 extending horizontally as viewed in FIG. 9 and
spaced apart any requisite distance. A second set of scribe lines
64 is provided extending at right angles to the set of scribe lines
63 and therewith defining a grid pattern of scribe lines on the
face 66 of the wafer. The back side 67 of the wafer is not scribed,
although it is contemplated that where economically expedient, such
scribing could be effected. The scribed wafer is then placed in a
carrier member 68 formed from a base sheet 69 having superposed and
adhesively secured thereto an apertured guide sheet 71 as shown in
FIG. 10. Preferably, the aperture 72 in the guide sheet is formed
so as to be slightly larger in diameter than the unbroken wafer
intended to be placed therein. The reason for the larger diameter
of the guide sheet is to provide sufficient clearance to
accommodate an increase in the diameter after it is broken. It
will, of course, be understood that the wafer after being broken
will require a somewhat larger space in which to be contained than
when in unbroken form by virtue of the minute spaces created
between the individual dies or chips into which the wafer has been
broken. It is customary practice in this art to enclose wafers to
be broken in plastic envelopes, one or more surfaces of which are
adhesive in nature and stick to one or both surfaces of the wafer
so as to retain the separate chips in their same positions after
being broken as they were prior to being broken. It has been found
that with the carrier illustrated in FIG. 10, the use of such
envelopes, and particularly the use of an adhesive sheet in
conjunction with the broken wafer are unnecessary. It has been
found advantageous, however, to place a very thin sheet of lens
paper 73 over the scribed side of the wafer after it is deposited
in the recess 72 formed by the guide sheet 71. In FIG. 10, a corner
of such lens paper is illustrated in the lower right-hand corner of
the carrier. In this view, a portion of the wafer has been broken
away to reveal the recess in which it is accommodated.
To effect breaking of the wafer, the carrier thus formed, with the
unbroken wafer in place, and covered with a sheet of lens paper 73,
is deposited in a feed assembly designated generally by the numeral
76. The feed assembly is supported on the front wall 7 of the
cabinet by an appropriate angle bracket 77 in association with a
slot 78 formed in the front wall of the cabinet and through which
the wafer is inserted into the apparatus. Referring to FIG. 4, the
angle bracket 77 supports a guide plate 79, one end of which is
appropriately supported on the support bracket, and the other end
of which extends perpendicularly away from the front wall of the
cabinet. The guide plate is provided with a centrally disposed
dovetail groove 81 having a stop pin 82 extending from the floor of
the groove, the groove being proportioned to slidably receive a
complementarily shaped key 83 attached to the bottom surface of the
feed slide 84. As illustrated in FIG. 5, the feed slide is provided
with a pair of laterally spaced forwardly projecting arms 86 and
87, the inner edges of which are provided with rabbets 88 forming a
recess within which the carrier 68 containing the wafer may be
deposited. A knob 89 is provided attached to the feed slide so that
the feed slide may be pushed through the aperture 78 in the front
wall and against the stop blocks 59 and 59' attached to the back
wall 6. This position of the feed slide is illustrated in FIGS. 2
and 3, while the outermost position of the feed slide is
illustrated in FIGS. 4 and 5.
With the feed slide inserted as illustrated in FIGS. 2 and 3, the
carrier borne wafer is positioned immediately above the curved
surface 58 of the platen as illustrated in dash lines in FIG. 1,
and as illustrated schematically in FIG. 13. In this position, the
wafer is preferably oriented with respect to the lateral edges 91
and 91' of the carrier so that one set of scribe lines, say the
scribe lines 64 as illustrated in FIG. 9, lie parallel to the
lateral edges 91 and 91'. When so oriented, the other set of scribe
lines 63 are, of course, perpendicular to the lateral edges 91 and
91' and parallel to lateral edges 92 and 92'. Referring to FIG. 11,
it will there be seen that when the wafer is so oriented in the
carrier 68, the scribe lines 64 lie parallel to a Y axis which is
in turn parallel to the lateral edges 91-91' of the carrier. In
like manner, the scribe lines 63 lie parallel to the lateral edges
92 and 92' and parallel to an X axis which is in turn parallel to
the lateral edges 92 and 92'.
It will thus be seen that with the carrier 68 positioned in the
rabbets 88 of the feed plate 34 so that the lateral edges 91 and
91' extend parallel to the direction of travel of the feed slide,
the scribe lines 64 of the wafer will also lie parallel to the
direction of movement of the wafer, and will lie parallel to and
extend transversely of the working section 36 of the taut steel
band 29. If it is assumed that the curved surface 58 is curvilinear
in conformation, then the scribe lines 64 will, of course, lie
parallel to the curved surface 58.
Actuation of the main power cylinder 41 when the wafer is thus
positioned will cause the wafer and carrier in which it is
supported to be brought into tight flat abutment with the underside
of the working portion 36 of the steel band 29. Since a vertical
median plane including the axis of the platen and lying
perpendicular to the front and back walls will also include the
axis Y as illustrated in FIG. 11, it will be apparent that
continued upward pressure exerted by the platen will cause the
wafer to crack along the first scribe line A coincident with the Y
axis as viewed in FIG. 11 and as illustrated schematically in FIGS.
13 and 14. This first crack in the wafer along the scribe line A,
of course, divides the wafer into two equal halves along a median
plane defined by the Y axis. The wafer is caused to crack at this
scribe line by virtue of the tension imposed on the band 36 which
lies in tight surface-to-surface abutment with the top surface 66
of the wafer, resulting in a concentrated bending moment being
imposed against the underside of the wafer opposite the scribe line
A by the upwardly moving platen 56. The two opposite halves of the
wafer are caught between the underside of the taut steel band and
the top surface of the platen so that a restraining force is
exerted against upward movement of the wafer by the taut steel
band, such restraining force being spread over the entire scribed
surface of the two halves of the wafer.
It will, of course, be apparent that as the platen moves upwardly
against the underside of the carrier 68, carrying the wafer into
abutting surface contact with the underside of the steel band, the
carrier is lifted bodily from the feed slide 84, and caused to move
upwardly with the platen. Simultaneously, the upwardly moving
platen imposes tension in the band in opposition to the tension
therein imposed by the air cylinders 18 and 19 causing the pistons
23 in such air cylinders to move upwardly against the 100 psi
pressure maintained in the cylinders above the pistons.
Continued upward movement of the platen results in greater
conformation of the flexible steel band 29 with the curvature of
the platen, causing each half of the wafer to be simultaneously
cracked along two scribe lines B and B' as illustrated in FIG. 15.
It will thus be seen that after the first break along the scribe
line A, each resulting half of the wafer is successively broken
simultaneously into separate strips which remain caught between the
band and the upper curved surface of the platen. Obviously, these
strips retain their original orientation with respect to the
carrier within which they are accommodated. As illustrated in FIG.
16, continued upward movement of the platen results in effecting
the third break along the scribe lines C and C', such breaking
action of each half of the wafer continuing until the entire wafer
has been broken along the scribe lines 64 parallel to the Y
axis.
In the second step of the operation, the platen is retracted, the
carrier and the wafer carried therein and now broken into
individual strips is reoriented in the feed slide and the operation
is repeated to break the wafer along the scribe lines 63 in like
manner, thus effectively breaking the wafer into individual chips
or dies. FIG. 11 illustrates the scribed surface of the wafer after
it has been completely broken along the scribe lines 64 parallel to
the Y axis. FIG. 12 illustrates the scribed surface of the wafer
after it has been broken along both sets of scribe lines 63 and 64
lying parallel, respectively, to the X and Y axes. As shown, the
mere act of breaking the wafer has caused the individual dies to
separate somewhat to fill the recess 72 formed in the carrier
68.
FIGS. 17 and 18 illustrate diagrammatically the relationship
between the taut steel band, the underlying platen, and the
carrier-supported wafer interposed therebetween in relation to the
X,Y and Z axes. Applying this system of axes to FIG. 1 of the
drawing, the X and Y axes would lie horizontal, the X axis
extending from left to right longitudinally of and parallel to the
steel band 29, while the Y axis extends in a fore and aft direction
perpendicular to the front and rear walls of the cabinet, and
transversely of the steel band coincident with a vertical axis
through the main drive cylinder 41. The Z axis extends vertically
as viewed in FIG. 1, perpendicular to the X and Y axes and
perpendicular also to the steel band.
FIG. 18 illustrates schematically the directions in which pressures
are applied as between the taut steel band and the movable platen
to effect the result described above. Obviously, different
arrangements may be used to secure a similar effect. For instance,
the platen might be stationary and the taut steel band, resiliently
anchored at opposite ends, be forced downwardly by spools spaced on
opposite sides of the platen. Thus, any appropriate means may be
used to cause the band to drape itself over the platen.
After the wafer has been broken along the scribe lines 64 lying
parallel to the Y axis, the feed slide 84 is withdrawn into the
position illustrated in FIG. 4 and the carrier 68, supporting the
wafer now broken along one set of scribe lines, must be reoriented
with respect to the feed slide so that when it is again advanced to
position the wafer above the platen, the scribe lines 63 will be
oriented parallel to the Y axis. To effect such reorientation of
the carrier, a turning device designated generally by the numeral
96 is provided attached to the lower side of the guide plate 79.
This assembly is best shown in FIGS. 3-6. Referring to FIG. 3, the
assembly includes an outer housing 97 having an internal bore 98
and a downwardly depending skirt portion 99. The skirt portion is
provided with an inverted U-shaped slot 101, the downwardly
depending arms of the U-shaped slot being positioned in the skirt
99 circumferentially 90.degree. apart. Port means 102 are provided
in the wall of the housing as shown, and a plug valve 103 is
slidably disposed within the bore 98 of the housing. A handle 104
is provided attached to the plug valve, the handle being adapted to
work in the U-shaped slot 101 so that the handle may be swung
through an arc of 90.degree. to rotate the plug valve through
90.degree. within the housing. The plug valve 103 is provided with
a transverse passageway 106 which in an elevated position of the
plug valve communicates with the port 102. In the depressed
position of the plug valve, as illustrated in FIG. 3, the
transverse passageway 106 is blocked by the inner periphery of bore
98. A second passageway 107 is provided extending axially of the
plug valve and communicating with the transverse passageway 106.
The upper end of the passageway 107 communicates with an annular
chamber 108 disposed below an apertured cap 109, the apertures 112
in the cap communicating the top surface of the cap with the
chamber 108 thereunder. It will thus be seen that by manipulation
of the handle 104 into a raised position, the transverse passageway
106 is brought into alignment with the port 102 so that suction or
vacuum imposed on this port causes a reduced pressure in the
chamber 108 and apertures 112, thus sucking the carrier 68 tightly
down on the top surface of the cap 109. Since the action of
elevating the plug valve to bring the passageway 106 into alignment
with the port 102 has carried the top surface of the cap 109
upwardly, the carrier 68 has also been carried upwardly until the
lateral edges 91-91' and 92-92' clear the rabbeted edges of the
feed slide so that the carrier may be rotated through 90.degree..
Such rotation is effected by swinging the handle 104 through an arc
of 90.degree. as illustrated in broken lines in FIGS. 5 and 6. The
handle 104 is then lowered, causing the plug valve to slide
downwardly, thus dropping the carrier 68 back into the receptacle
formed by the rabbets in the feed slide 84. The wafer is now ready
to be reinserted for breaking in the opposite direction. The port
102 is connected to a source of vacuum through an appropriate
tubing (not shown) which extends into the housing at the nearest
convenient point for connection to an appropriate fitting 113
carried on the back wall 6 of the housing.
The apparatus thus described in operated by a pneumatic circuit
illustrated schematically in FIG. 8. As there shown, air under
pressure is admitted from a convenient and appropriate source
through a fitting 116 on the back wall 6 of the housing, connected
by an appropriate tubing 117 to the inlet ports of a pair of
miniature pressure regulators 118 and 119. The pressure regulators
are adjustable and may be set to a selected output pressure by
appropriate control knobs 121 (FIG. 1) the selected pressure being
indicated on an appropriate gauge 122 extending through an aperture
formed in the front wall 7 of the housing. The pressure regulators
may conveniently be of the type manufactured by the C. A. Norgren
Company, Littleton, Col., and sold under the model No.
R06-200-RGK-AUl. The pressure regulator 119 is similarly provided
with a gauge 123 correspondingly positioned in the front wall 7 of
the housing, but adjacent the opposite edge 16 thereof.
The outlet port 126 of the pressure regulator 118 is connected by
an appropriate tubing 127 to the inlet port 24 of the air cylinder
18, and by an appropriate branch line 127' to the inlet port 24 of
air cylinder 19. It will thus be seen that manipulation of the
control knob 121 for pressure regulator 118 controls the pressure
imposed on the pistons within air cylinders 18 and 19, and
therefore controls the tension applied to the steel band 29. This
pressure is constantly applied, there being no interruption
necessary or desired so long as the device is connected to a source
of air. The output side of the pressure regulator 119, is connected
through an appropriate tubing 128 to spring pressed valves 129 and
131. Both of these valves are spring pressed in a normally closed
attitude, the valve 129 having a push button 132 accessible from
the front of the housing as illustrated in FIG. 1, while the valve
131 is operated automatically by movement of the platen 56 to its
upper extremity, the platen carrying a short lever 133 adapted to
engage the plunger 134 of valve 131. To vary the excursion of the
platen, the position of the valve 131 within the housing, as
illustrated best in FIGS. 1 and 3, is adjustable by a knob 136
which clamps the valve to an appropriate bracket 137 fastened to
the back wall of the housing.
Mounted within the housing to the back wall thereof as illustrated
in FIG. 1, is a four-way valve 141 having a main inlet port 142
connected to the outlet port of pressure regulator 119. As is
conventional with four-way type air valves, the main input port 142
is flanked by appropriate exhaust ports indicated schematically in
FIGS. 1 and 8 by the short arrows. Ports A and B, constituting the
working ports of the valve, are connected respectively to ports 143
and 144 as shown. Opposite ends of the four-way valve are provided
with pilot fittings 146 and 147, the pilot fitting 147 being
connected to the output port of valve 129. The pilot fitting 146 is
connected by an appropriate tubing 148 to the output port of valve
131 as shown. To actuate the apparatus, the fitting 116 is
connected to an appropriate source of air under pressure, and
pressure regulators 118 and 119 adjusted to the desired pressure
level. It should be noted that the pressure regulator 119 is
connected to the four-way valve through the inlet port 142 and
therefore controls the pressure of air passing through this valve
into the main drive cylinder 41. After adjustment of the pressure,
a wafer is positioned above the platen as previously described, and
when in place, the push button 132 is depressed momentarily. Valve
129 is thus opened to admit air under pressure to the pilot fitting
147, which causes the valve spool within the valve housing to shift
to the left as viewed in FIG. 8, permitting high pressure air to
pass through the valve housing and port B to be admitted into the
cylinder 41 through port 143 so as to cause upward movement of the
piston within the cylinder. Such upward movement of the piston and
platen is resisted by the tension imposed on band 29 by cylinders
18 and 19. As previously discussed, the effective area of piston 46
in cylinder 41 is correlated to the effective area of the pistons
in cylinders 18 and 19 so that the platen is carried upwardly and
the pistons 23 in cylinders 18 and 19 are also carried upwardly
while imposing tension on the band.
When the platen has reached its upper extremity, lever 133 (FIG. 3)
engages plunger 134 of valve 131, causing high-pressure air to pass
through this valve, through tubing 148 and into the pilot fitting
146 of the main four-way valve. The valve spool is thus shifted to
the right, connecting port B thereof to one of the exhaust ports,
and connecting port A to the source of high-pressure air so that
air under pressure is now admitted to port 144 into the air
cylinder 41 above the piston, driving the piston downwardly to
shift the platen into a wafer loading position. After withdrawing
the feed slide, the wafer turning mechanism 96 is actuated to
rotate the wafer 90.degree. so as to reorient it for breaking along
scribe lines extending in the opposite direction to the scribe
lines broken in the first operation. The feed slide is pushed in,
the push button 132 is again depressed, and the apparatus is
automatically recycled so as to break the wafer in the other
direction.
While the foregoing constitutes manual operation of the apparatus,
it will be clear that through appropriate automated feeding
equipment and automated controls, the operation may proceed
substantially completely without human intervention.
* * * * *