U.S. patent application number 09/940203 was filed with the patent office on 2002-02-28 for concave face wire bond capillary.
Invention is credited to Bettinger, Michael J., Chapman, Gregory M., Due, Jennifer A..
Application Number | 20020023943 09/940203 |
Document ID | / |
Family ID | 22586541 |
Filed Date | 2002-02-28 |
United States Patent
Application |
20020023943 |
Kind Code |
A1 |
Chapman, Gregory M. ; et
al. |
February 28, 2002 |
Concave face wire bond capillary
Abstract
An improved wire bonding capillary used in the bonding of wires
to the bond pads of a semiconductor device and the leads of a lead
frame, the wire bonding capillary having a working tip having a
working surface including a flat annular portion surrounding the
wire feed aperture in the capillary and a concave surface extending
therefrom to the intersection with the radius extending from the
external tip diameter of the working tip.
Inventors: |
Chapman, Gregory M.;
(Meridian, ID) ; Bettinger, Michael J.; (Eagle,
ID) ; Due, Jennifer A.; (Meridian, ID) |
Correspondence
Address: |
TRASK BRITT
P.O. BOX 2550
SALT LAKE CITY
UT
84110
US
|
Family ID: |
22586541 |
Appl. No.: |
09/940203 |
Filed: |
August 27, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09940203 |
Aug 27, 2001 |
|
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09649209 |
Aug 28, 2000 |
|
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Current U.S.
Class: |
228/180.5 ;
228/4.5; 257/E21.518; 257/E21.519 |
Current CPC
Class: |
H01L 2224/85205
20130101; H01L 2924/01079 20130101; H01L 2224/45147 20130101; H01L
2224/7825 20130101; H01L 2224/85043 20130101; H01L 2224/48465
20130101; H01L 2224/48465 20130101; H01L 2224/48824 20130101; Y10S
228/904 20130101; H01L 2924/01029 20130101; H01L 2224/78302
20130101; H01L 2924/20107 20130101; H01L 2224/48091 20130101; H01L
2224/48091 20130101; H01L 2224/85205 20130101; H01L 2224/85205
20130101; H01L 2224/85201 20130101; H01L 2924/01005 20130101; H01L
2224/45015 20130101; H01L 2224/85181 20130101; H01L 24/85 20130101;
H01L 2224/48247 20130101; H01L 2224/45144 20130101; H01L 2224/48624
20130101; H01L 2224/05624 20130101; H01L 2224/45144 20130101; H01L
2224/48465 20130101; H01L 2224/78307 20130101; H01L 2224/85045
20130101; H01L 2224/85205 20130101; H01L 2224/78301 20130101; H01L
2224/48824 20130101; H01L 2224/48465 20130101; H01L 2924/20108
20130101; H01L 24/45 20130101; H01L 2924/20105 20130101; H01L
2924/00 20130101; H01L 2924/00 20130101; H01L 2924/00 20130101;
H01L 2224/45144 20130101; H01L 2224/48227 20130101; H01L 2224/48465
20130101; H01L 2924/00 20130101; H01L 2224/48247 20130101; H01L
2924/00 20130101; H01L 2224/48465 20130101; H01L 2224/48091
20130101; H01L 2924/00 20130101; H01L 2924/00014 20130101; H01L
2924/00014 20130101; H01L 2924/00015 20130101; H01L 2924/00014
20130101; H01L 2924/00014 20130101; H01L 2924/00 20130101; H01L
2924/00 20130101; H01L 2224/48227 20130101; H01L 2224/45147
20130101; H01L 2224/45144 20130101; H01L 2924/00 20130101; H01L
2224/78301 20130101; H01L 2224/85181 20130101; H01L 2924/01006
20130101; H01L 2924/01082 20130101; B23K 2101/40 20180801; H01L
2224/45147 20130101; H01L 2224/48227 20130101; H01L 2224/48624
20130101; H01L 2224/78306 20130101; H01L 2924/20106 20130101; B23K
20/005 20130101; H01L 24/78 20130101; H01L 2224/45015 20130101;
H01L 2224/48465 20130101; H01L 2924/01013 20130101; H01L 24/48
20130101 |
Class at
Publication: |
228/180.5 ;
228/4.5 |
International
Class: |
B23K 031/02; B23K
037/00 |
Claims
What is claimed is:
1. A wire bonding capillary used for wire bonding on a
semiconductor device having a plurality of components comprising: a
wire bonding capillary tool including: a capillary tip having an
elongated hole therethrough terminating at one end of the capillary
tip and a face on the one end of the capillary tip, the face
including a first frusto-conical surface extending from a portion
of the elongated hole of the capillary tip, a second frusto-conical
surface having a portion thereof connected to the first
frusto-conical surface, a substantially horizontal annular surface
having a portion connected to the second frusto-conical surface,
said substantially horizontal annular surface defined by the radius
of curvature of the capillary tip, a concave surface with a degree
of curvature, said concave surface extending from a portion of the
substantially horizontal annular surface, the degree of curvature
of the concave surface defined by a radius of curvature and the
degree of curvature of the concave surface providing clearance of
the capillary tip from adjacent components of said plurality of
components, and an annular curved surface intersecting the concave
surface extending from the substantially horizontal annular
surface.
2. The wire bonding capillary of claim 1, wherein the substantially
horizontal annular curved surface is formed by a radius.
3. The wire bonding capillary of claim 1, wherein the substantially
horizontal annular surface intersects an outer diameter of the
capillary tip of the wire bonding capillary tool.
4. The wire bonding capillary of claim 1, wherein the capillary tip
includes an annular conical surface extending from an outer
diameter of the face of the capillary tip.
5. A method of forming a wire bond on a bond pad of a semiconductor
device having an active surface thereon having at least one bond
pad thereon, said method comprising: providing a wire bonding
capillary including: a capillary tip having an elongated hole
therethrough, the elongated hole terminating at one end of the
capillary tip; and a face on the one end of the capillary tip, the
face including a first frusto-conical surface extending from a
portion of the elongated hole of the capillary tip, a second
frusto-conical surface having a portion thereof connected to the
first frusto-conical surface, a substantially horizontal annular
surface having a portion connected to the second frusto-conical
surface, a concave surface having a portion extending from the
substantially horizontal annular surface, and an annular curved
surface intersecting the concave surface; extending a wire through
the elongated hole in the capillary tip; heating a portion of the
wire to form a mass on an end thereof; contacting said at least one
bond pad on said active surface of said semiconductor device with
the mass on the end of the wire; and securing the mass on the end
of the wire to said at least one bond pad on said active surface of
said semiconductor device; and forming a wire bond to said at least
one bond pad having a substantially horizontal annular surface on a
portion of said wire bond, said wire bond having no contact with
said active surface of said semiconductor device, said mass on the
end of the wire used to form said wire bond including a first
frusto-conical portion adjacent the wire, a second frusto-conical
portion connected to the first frusto-conical portion, and a
substantially horizontal annular portion connected to the second
frusto-conical portion.
6. A method of forming a wire bond on a lead finger of a lead frame
comprising: providing a wire bonding capillary including: a
capillary tip having an elongated hole therethrough, the elongated
hole terminating at one end of the capillary tip; a face on an end
of the capillary tip, the face including a first frusto-conical
surface extending from a portion of the elongated hole of the
capillary tip, a second frusto-conical surface having a portion
thereof connected to the first frusto-conical surface, a
substantially horizontal annular surface having a portion connected
to the second frusto-conical surface, having a concave surface
extending from the substantially horizontal annular surface, and an
annular curved surface intersecting the concave surface; extending
a portion of a wire through the elongated hole in the capillary
tip; heating a portion of the wire; contacting a portion of said
lead finger of said lead frame with the heated portion of the wire;
and attaching a portion of the heated portion of the wire to a
portion of said lead finger forming a wire bond thereon having a
curved convex surface on a portion thereof formed by at least a
portion of the concave surface of the face of the capillary tip.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
09/649,209, filed Aug. 28, 2000, pending, which is a continuation
of application Ser. No. 09/162,649, filed Sep. 29, 1998, now U.S.
Pat. 6,158,647, issued Dec. 12, 2000.
BACKGROUND OF THE INVENTION
[0002] Field of the Invention: The invention relates to
semiconductor manufacturing. More particularly, the invention
relates to an improved wire bonding capillary used in the bonding
of wires to the bond pads of a semiconductor device and the leads
of a lead frame.
[0003] Background of the Invention: In semiconductor device
manufacturing, a wire bonding process is used to electrically
connect the metal bond pads on the active surface of a
semiconductor die to the leads or lead fingers of a lead frame.
Wire bonding devices are well known in the art. U.S. Pat. Nos.
3,894,671, 4,877,173, and 5,082,154 illustrate wire bonding
devices.
[0004] The wire bonding process occurs during the final stages of
manufacture of the semiconductor device before the semiconductor
device is enclosed within a sealed or encapsulated package.
Although a variety of different packaging systems are used, most
packaging systems include a lead frame on which the semiconductor
die is mounted. The lead frame has lead fingers which are connected
to the bond pads on the active surface of the semiconductor die
through the use of wires bonded to the lead fingers and bond pads.
Subsequently, the semiconductor die, wires, and portions of the
lead fingers and lead frame are encapsulated in plastic during a
molding process. After the molding process, the portions of the
lead fingers extending beyond the molded plastic material are
trimmed and formed into the desired configuration for the use and
mounting of the semiconductor device on a substrate.
[0005] The wires used to connect the bond pads of the semiconductor
die to the lead fingers of the lead frame are small in diameter,
have as short a length as possible, and are typically of gold.
During the wire bonding process, a heat block heats the
semiconductor die and the lead frame to a temperature in the range
of 150.degree. C. to 350.degree. C. A bonding capillary tool
mechanically presses the wire against a bond pad on the active
surface of the semiconductor die and then to a bonding site on the
desired lead finger of the lead frame. The bond wire is threaded
through the bonding capillary for use in the bonding process. The
end of the wire threaded through the bonding capillary is then
heated by an electrical discharge or a hydrogen torch to a molten
state, thereby forming a ball of molten material on the end of the
bond wire extending from the bonding capillary. The molten ball is
pressed by the bonding capillary against the heated bond pad on the
active surface of the semiconductor die to alloy the metallic
elements of the wire and the bond pad, thereby bonding the wire to
the bond pad in a ball type wire bond. In some instances,
ultrasonic vibration of the bonding capillary may be used during
the bonding process. After the bonding of the wire to the bond pad
on the active surface of a semiconductor die, the bonding capillary
tool is moved to a bonding site on the desired lead finger of the
lead frame. The wire is pressed against the heated lead finger of
the lead frame to bond the wire to the lead finger. The bond wire
is then tensioned by the bonding capillary until the wire is
sheared, making a stitch or wedge type wire bond on the lead
finger. The bonding process is repeated for the desired bond pads
on the active surface of the semiconductor die for connections to
the desired lead fingers of the lead frame.
[0006] One type of wire bonding capillary design is illustrated in
U.S. Pat. No. 4,415,115. The bonding capillary tip is formed having
a flat bonding surface and an annular cutting ridge raised from the
flat bond surface surrounding the aperture through which the wire
is fed in the bonding capillary. Alternately, the cutting ridge may
comprise a semicircle shape rather than an annular shape.
[0007] Another type of wire bonding capillary is illustrated in
U.S. Pat. No. 5,421,503. The bonding capillary is for use in
automatic gold ball bonders for bonding fine gold wires onto
closely spaced bond pads on semiconductor devices. The bonding
capillary comprises a cylindrical body portion which fits into an
ultrasonic transducer having a bottle-neck working tip on the other
end of the body portion. The working tip includes a working face
comprising an annular ring between the chamfer diameter of the
working tip and the working tip diameter and a face angle of
approximately 22 degrees plus or minus 3 degrees.
[0008] Yet another wire bonding capillary is illustrated in U.S.
Pat. No. 5,662,261. The wire bonding capillary includes a working
tip having an elongated hole therethrough and a face extending away
from the hole at multiple angles of increasing magnitude.
[0009] While the size of semiconductor devices continues to
decrease and the number of bond pads on the active surface
continues to increase, having smaller pitch between adjacent bond
pads and the width of lead fingers of lead frames decreases, it is
necessary to have a wire bonding capillary which will form
effective ball type wire bonds on the bond pads of the
semiconductor device and stitch or wedge type wire bonds on the
lead fingers of the lead frame having acceptable pull-off strength
characteristics without damaging the circuitry of the semiconductor
device. Such requirements illustrate the need for a wire bonding
capillary which will effectively make a ball type wire bond on the
bond pad of the semiconductor device without contacting the surface
of the semiconductor device adjacent thereto and will effectively
make stitch or wedge type wire bonds on the lead fingers of lead
frames.
BRIEF SUMMARY OF THE INVENTION
[0010] The present invention relates to an improved wire bonding
capillary used in the bonding of wires to the bond pads of a
semiconductor device and the leads of a lead frame. The wire
bonding capillary has a working tip having a working surface
including a flat annular portion surrounding the wire feed aperture
in the capillary and a concave surface extending therefrom to the
intersection with the radius extending from the external tip
diameter of the working tip.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0011] FIGS. 1 through 4 are cross-sectional views showing the
steps of a typical wire bonding operation;
[0012] FIG. 5 is a cross-sectional view of a prior art working tip
of a wire bonding capillary having a flat surface thereon;
[0013] FIG. 6 is a cross-sectional view of a prior art working tip
of a wire bonding capillary having an angled surface thereon;
[0014] FIG. 7 is a cross-sectional view of the working tip of the
wire bonding capillary of the present invention;
[0015] FIG. 8 is a cross-sectional view of the working tip of the
wire bonding capillary of the present invention making a ball type
wire bond on a bond pad of a semiconductor device; and
[0016] FIG. 9 is a cross-sectional view of the working tip of the
wire bonding capillary of the present invention making a stitch or
wedge type bond on a lead finger of a lead frame.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Referring to drawing FIGS. 1 through 4, a typical wire
bonding operation using a capillary is illustrated. A wire 40,
typically of gold or copper, is threaded through a hole 20 in the
capillary tip 22. The end of wire 40 is heated by an electrical
discharge or a hydrogen torch to a molten state, thereby forming a
ball 42 of molten metal on the end of wire 40. Capillary tip 22 is
lowered toward bond pad 44 on the active surface of a semiconductor
device 46. The bond pad 44 is typically of aluminum or has an
aluminum layer thereon. However, the bond pad may be of any
suitable conductive metal. The semiconductor device 46 is heated to
a temperature of 150.degree. C. to 350.degree. C. by a heated block
48. Molten metal ball 42 is pressed by the capillary tip 22 against
the heat bond pad 44 to alloy the metallic elements of the wire 40
and bond pad 44, thereby bonding the wire 40 to the bond pad 44. In
some instances, ultrasonic vibrations are applied to the capillary
tip 22 as the molten metal ball 42 on the end of wire 40 is pressed
against the bond pad 44.
[0018] Referring specifically to drawing FIG. 4, capillary tip 22
is then raised, causing the wire 40 to feed through the aperture in
the capillary tip 22 and moved to a bonding site on a lead finger
50 of a lead frame. The lead finger 50 is heated to a temperature
of 150.degree. C. to 350.degree. C. by heated block 48. The wire 40
is pressed against the heated lead finger 50 to alloy the metallic
elements of wire 40 and lead finger 50, thereby bonding the wire 40
to the lead finger 50. If desired, ultrasonic vibrations may be
applied to the capillary tip 22 as wire 40 is pressed against lead
finger 50. The face of the capillary tip 22 severs the wire 40 to
form a stitch type wire bond of the wire 40 to the lead finger 50,
thereby allowing the capillary tip 22 to be used to repeat the
process with respect to other bond pads 44 on the active surface of
the semiconductor device 46 and lead fingers 50 of the lead frame,
depending upon the uniformity of the thickness of the coatings 49
and/or 47 (FIG. 5) on the semiconductor device 46.
[0019] Referring to drawing FIG. 5, the tip portion of a prior art
wire bonding capillary 60 is illustrated forming a molten metal
ball 42 on the bond pad 44 of a semiconductor device 46 having a
first coating 47 thereon and a second coating 49 over the first
coating 47. The tip portion of the bonding capillary 60 includes a
central aperture 62 having a frusto-conical surface 63 at the lower
end of the aperture, a flat annular surface 64 extending from the
frusto-conical surface 63 to an annular curved surface 66 which
terminates in the outer surface 68 of the tip. The frusto-conical
surface 63 and flat annular surface 64 help to form the required
wire bonds to the bond pad 44 and lead finger (not shown) of a lead
frame. However, the flat annular surface 64 may contact the second
coating 49 on the semiconductor device 46 during the bonding of the
molten metal ball 42 of the wire 40 to the bond pad 44, causing
damage to the semiconductor device 46.
[0020] Referring to drawing FIG. 6, the tip portion of a prior art
wire bonding capillary 70 is illustrated forming a molten metal
ball 42 on the bond pad 44 of a semiconductor device 46 having a
first coating 47 thereon and a second coating 49 over the first
coating 47. The tip portion of the bonding capillary 70 includes a
central aperture 72 having a first frusto-conical surface 73 at the
lower end of the central aperture 72, a second frusto-conical
surface 74 extending from the first frusto-conical surface 73 to an
annular curved surface 76 which terminates in the outer surface 78
of the tip. The first frusto-conical surface 73 and second
frusto-conical surface 74 help to form the required wire bonds to
the bond pad 44 and lead finger (not shown) of a lead frame. The
second frusto-conical surface 74 is formed generally at an angle of
four degrees (4.degree.) with respect to a horizontal plane
extending through the upper surface of the second coating 49 on the
semiconductor device 46. However, the second frusto-conical surface
74 may contact the second coating 49 on the semiconductor device 46
during the bonding of the molten metal ball 42 of the wire 40 to
the bond pad 44, causing damage to the semiconductor device 46,
depending upon the uniformity of thickness of the coating 49 and/or
47 on the semiconductor device 46.
[0021] Referring to drawing FIG. 7, the tip of a wire bonding
capillary 80 of the present invention is illustrated. The tip
portion of the bonding capillary 80 includes a central aperture 82
having a first frusto-conical surface 84 and second frusto-conical
surface 86 extending from the lower end of the first frusto-conical
surface 84, both located at or near the lower end of the aperture
82, and, on the lower surface of the tip, a flat annular surface 88
extending for a distance between diameter "a" to diameter "b" of
the tip from the second frusto-conical surface 86 of the aperture
82 and a face having an annular concave surface 90 extending from
the diameter b of the flat annular surface 88 into the tip and
outwardly a distance to a point of inflection (tangency) 91 to an
annular curved surface 92 defined by a radius "r" of curvature of
the tip, which, in turn, intersects at point 94, the lower annular
radial diameter "R" of the wire bonding capillary, with the annular
conical outer surface 96 of the tip. A radius of curvature "RR" is
used for the formation of the annular concave surface 90, the size
of the radius "RR" determining the degree of curvature of the
annular concave surface 90 for the relative clearance between the
tip of the capillary 80 and a second coating 49 on the surface of
the semiconductor device 46. The first frusto-conical surface 84
and second frusto-conical surface 86 of the aperture 82 and the
flat annular surface 88 help to form the required wire bonds to the
bond pad 44 and lead finger (not shown) of a lead frame. The flat
annular surface 88 of the lower surface of the tip is used to sever
the wire 40 during the formation of a stitch or wedge type wire
bond on the lead finger (not shown) of a lead frame during the wire
bonding process. The width of the flat annular surface 88 is
determined by the size of the bond pad of the semiconductor device
upon which the wire bonding capillary 80 is to be used.
[0022] Referring to drawing FIG. 8, the tip of a wire bonding
capillary 80 of the present invention is illustrated in relation to
a semiconductor device 46 having a second coating 49 and a bond pad
44 on the active surface thereof. The first frusto-conical surface
84, second frusto-conical surface 86, and flat annular surface 88
form the molten metal ball 42 with the bond pad 44, the annular
concave surface 90 providing clearance with the second coating 49
on the active surface of the semiconductor device 46 to prevent
contact of the tip of the wire bonding capillary 80.
[0023] Referring to drawing FIG. 9, the wire bonding capillary 80
of the present invention is illustrated in conjunction with a lead
finger 50 of a lead frame. The wire 40 is bonded in the bond area
52 of the lead finger 50 by the wire bonding capillary 80 with the
flat annular surface 88, annular concave surface 90, and annular
curved surface 92 of the tip deforming the wire 40 into engagement
with a portion of the lead finger 50. The flat annular surface 88
of the wire bonding capillary 80 is used to sever the wire 40 after
the bonding thereof to the lead finger 50. The annular concave
surface 90 and annular curved surface 92 of the wire bonding
capillary are used in conjunction with the flat annular surface 88
thereof to form the bond area 52 of the connection of the wire 40
to the lead finger 50, the bond area 52 having a convex portion 90'
which is formed by annular concave surface 90 of the tip of
capillary 80 and a curved portion 92' which is formed by the
annular curved surface 92 of the tip of capillary 80. The flat
annular surface 88, annular concave surface 90, and curve annular
surface 92 provide a gradual transition between the wedge deformity
of the wire 40 and the existing circular shape of the wire 40
extending beyond the bond area 52, the wire 40 being heated by
suitable means before the formation of the stitch or wedge type
bond on the lead finger 50 while the lead finger is heated before
the formation of the wire bond thereto.
[0024] From the foregoing, it is apparent that changes,
modifications, and deletions may be made to the capillary bonding
tool of the present invention which fall within the scope of the
invention, for instance, varying the length or size of the radii
"r", "R", or "RR" and the radial dimensions of the flat annular
surface 88 between the dimensions "a" and "b."
* * * * *