PH12013000287B1 - Bonding capillary - Google Patents

Bonding capillary Download PDF

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Publication number
PH12013000287B1
PH12013000287B1 PH12013000287A PH12013000287A PH12013000287B1 PH 12013000287 B1 PH12013000287 B1 PH 12013000287B1 PH 12013000287 A PH12013000287 A PH 12013000287A PH 12013000287 A PH12013000287 A PH 12013000287A PH 12013000287 B1 PH12013000287 B1 PH 12013000287B1
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PH
Philippines
Prior art keywords
tip surface
bonding
wire
asperities
bonding capillary
Prior art date
Application number
PH12013000287A
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PH12013000287A1 (en
Inventor
Jumpei Onishi
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Toto Ltd
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Publication of PH12013000287B1 publication Critical patent/PH12013000287B1/en
Publication of PH12013000287A1 publication Critical patent/PH12013000287A1/en

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Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/74Apparatus for manufacturing arrangements for connecting or disconnecting semiconductor or solid-state bodies
    • H01L24/78Apparatus for connecting with wire connectors
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42Wire connectors; Manufacturing methods related thereto
    • H01L2224/44Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L2224/45Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
    • H01L2224/45001Core members of the connector
    • H01L2224/45099Material
    • H01L2224/451Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof
    • H01L2224/45138Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof the principal constituent melting at a temperature of greater than or equal to 950°C and less than 1550°C
    • H01L2224/45144Gold (Au) as principal constituent
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42Wire connectors; Manufacturing methods related thereto
    • H01L2224/44Structure, shape, material or disposition of the wire connectors prior to the connecting process
    • H01L2224/45Structure, shape, material or disposition of the wire connectors prior to the connecting process of an individual wire connector
    • H01L2224/45001Core members of the connector
    • H01L2224/45099Material
    • H01L2224/451Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof
    • H01L2224/45138Material with a principal constituent of the material being a metal or a metalloid, e.g. boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po), and alloys thereof the principal constituent melting at a temperature of greater than or equal to 950°C and less than 1550°C
    • H01L2224/45147Copper (Cu) as principal constituent
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/74Apparatus for manufacturing arrangements for connecting or disconnecting semiconductor or solid-state bodies and for methods related thereto
    • H01L2224/78Apparatus for connecting with wire connectors
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/74Apparatus for manufacturing arrangements for connecting or disconnecting semiconductor or solid-state bodies and for methods related thereto
    • H01L2224/78Apparatus for connecting with wire connectors
    • H01L2224/7825Means for applying energy, e.g. heating means
    • H01L2224/783Means for applying energy, e.g. heating means by means of pressure
    • H01L2224/78301Capillary
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/74Apparatus for manufacturing arrangements for connecting or disconnecting semiconductor or solid-state bodies and for methods related thereto
    • H01L2224/78Apparatus for connecting with wire connectors
    • H01L2224/7825Means for applying energy, e.g. heating means
    • H01L2224/783Means for applying energy, e.g. heating means by means of pressure
    • H01L2224/78301Capillary
    • H01L2224/78302Shape

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Wire Bonding (AREA)

Abstract

[Object] To provide a bonding capillary that can maintain a sufficient bonding strength for a long time. [Solution] Provided is a bonding capillary including a body having a tip surface that performs wire bonding. The tip surface has microscopic asperities. Peaks of the asperi ties are less sharp than valleys of the asperities. In the bonding capillary, when seen in a direction perpendicular to the tip surface, the area of the peaks is greater than the area of the valleys.

Description

a ' Ct 1
BONDING CAPILLARY 75 .
Technical Field Tg On
Embodiments of the invention relate to bonding capillary, and in particular, to a bonding Aapillary that is suitable for bonding a hard bonding wiye made of copper or the like.
Background Art
In a wire bonding operation of bonding a semiconductor device to a lead of a lead frame through a fine metal wire, an end of the fine metal wire (bonding wire) is press- bonded (first-bonded) to an electrode pad by using a bonding capillary, and then the fine metal wire is drawn and press-bonded (second-bonded) to the lead. When press- bonding the fine metal wire to the lead, ultrasonic vibrations are applied to the bonding capillary while the bonding capillary is pressing the fine metal wire, so that the fine metal wire is securely press-bonded to the lead.
In recent years, copper has been widely used as the material of bonding wires, because copper is less expensive than gold. However, when a copper wire is used for wire bonding, it is difficult to obtain a high bonding strength because a copper wire is hard, and the tip of a bonding ; capillary wears down easily. Therefore, as compared with gold wires, the use of copper wires has a problem in that a
! Yt the frequency of replacement of the bonding capillary is high.
PTL 1 discloses a bonding capillary having a tip surface on which rounded asperities are formed so that the amounts of adherents on the tip surface can be reduced and the lifetime of the bonding capillary can be increased.
PTL 2 discloses a bonding capillary including a tip portion having a part where the grain structure of the material is exposed so that the lifetime of the bonding capillary can be increased.
However, the technologies described in PTL 1 and PTL 2 have room for improvement in terms of a gripping force applied to a bonding wire and the ability to maintain an initial bonding strength for a long time. In particular, when using a bonding wire harder than a gold wire, such as a copper wire, problems arise in that the bonding strength decreases and the lifetime of the bonding capillary decreases due to wear.
Citation List
Patent Literature [PTL 1] Japanese Unexamined Utility Model
Registration Application Publication No. 62-190343 [PTL 2] Japanese Unexamined Patent Application
Publication (Translation of PCT Application) No. 2009-
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Summary of Invention Technical Problem
An object of the invention, which addresses such problems, is to provide a bonding capillary that can maintain a sufficient bonding strength for a long time.
Solution to Problem
A first invention is a bonding capillary including a body having a tip surface that performs wire bonding. The tip surface has microscopic asperities, and peaks of the asperities are less sharp than valleys of the asperities.
With the bonding capillary, a high bonding strength in an initial stage is ensured, and the high bonding strength can be maintained for a long time after repeated bonding operations.
A second invention is a bonding capillary of the first invention in which, when seen in a direction perpendicular to the tip surface, the area of the peaks is greater than the area of the valleys.
With the bonding capillary, the area of contact between a wire and the tip surface is increased and a gripping force between the tip surface and the bonding wire is increased.
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A third invention is a bonding capillary of the second : invention in which a skewness of the tip surface is -0.3 or less, and a mean height of the tip surface is in the range of 0.06 to 0.3 micrometers.
With the bonding capillary, deformation of the tip surface due to wear during use is small and the initial bonding strength can be maintained for a long time after repeated bonding operations.
A fourth invention is a bonding capillary of the . second invention in which a skewness of the tip surface is -0.43 or less, and a mean height of the tip surface is in the range of 0.16 to 0.3 micrometers.
With the bonding capillary, deformation of the tip surface due to wear during use is smaller and the initial bonding strength can be maintained for a long time after repeated bonding operations.
A fifth invention is a bonding capillary of the third or fourth invention in which a maximum peak height of the tip surface is 0.9 times the mean height or less. :
With the bonding capillary, deformation of the tip : surface due to wear during use is small and the initial bonding strength can be maintained for a long time after repeated bonding operations.
TAC
A sixth invention is a bonding capillary of any one of the first to fifth inventions in which a mean grain diameter of crystals exposed on the tip surface is 1.2 micrometers or less.
With the bonding capillary, in the case where the mean grain diameter of ceramic crystals is 1.2 micrometers or less, wear of the tip surface can be reduced.
A seventh invention is a bonding capillary of any one Co of the first to sixth inventions in which the body has a hole, into which a bonding wire is to be inserted, formed in the tip surface, and a chamfered portion located between the hole and the tip surface; and the asperities of the tip surface are defined by means of a roughness profile that is measured along a length of at least 100 micrometers in a surface region of the tip surface, the surface region extending at least 20 micrometers from an edge of the : chamfered portion away from the hole along the tip surface.
With the bonding capillary, in each of the first to : sixth inventions, in the case where the asperities are obtained by means of a roughness profile measured along a length of at least 100 micrometers in the surface region of the tip surface, a sufficient bonding strength can be maintained for a long time.
Advantageous Effects of Invention :
With the embodiments of the invention, a bonding capillary that can maintain a sufficient bonding strength for a long time is provided.
Brief Description of Drawings
FIG. 1 is a schematic view illustrating a bonding capillary according to an embodiment.
FIG. 2 is a schematic enlarged view illustrating the shape of a tip of the bonding capillary according to the embodiment.
FIG. 3 is a schematic enlarged view illustrating a tip surface of the bonding capillary according to the embodiment.
FIG. 4 is a schematic sectional view illustrating a state in which wire bonding is performed.
FIGS. 5(a) and 5(b) illustrate asperities on the tip surface according to the embodiment.
FIGS. 6(a) and 6(b) illustrate asperities on a tip surface according to a reference example (1).
FIGS. 7(a) and 7(b) illustrate asperities on a tip surface according to a reference example (2).
FIG. 8 is a table showing the results of evaluating
Examples and Comparative Examples.
FIG. 9 is a schematic perspective view illustrating a measurement region. e-
a
SE
.
FIG. 10 is a table showing the results of evaluating bonding strength.
FIGS. 1ll(a) and 11(b) are graphs showing the change in
Cpk as the number of times bonding was performed varied.
FIGS. 12(a) and 12(b) illustrate part of the method of manufacturing the bonding capillary.
FIG. 13 illustrates a method of measuring the mean grain diameter of ceramic crystals.
FIG. 14 is a table showing the relationship between the mean grain diameter of ceramic crystals and the lifetime of a bonding capillary.
Description of Embodiments
Hereinafter, an embodiment of the invention will be described with reference to the drawings. In the drawings, the same elements will be denoted by the same numerals and redundant description will be omitted. (Embodiment)
FIG. 1 is a schematic view illustrating a bonding capillary 110 according to the embodiment.
FIG. 2 is a schematic enlarged view illustrating the shape of a tip of the bonding capillary 110 according to the embodiment.
FIG. 3 is a schematic enlarged view illustrating a tip surface 50 of the bonding capillary 110 according to the : embodiment.
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FIG. 1 illustrates the entirety of the bonding capillary 110. FIG. 2 is an enlarged view of a region A in
FIG. 1. FIG. 3 is a bottom perspective view illustrating the tip surface 50.
As illustrated in FIG. 1, the bonding capillary 110 includes a body 10 having the tip surface 50. The body 10 includes a cylindrical portion 11, a conical portion 12, and a bottleneck portion 13. The cylindrical portion 11 has a diameter that allows the bonding capillary 110 to be mechanically fixed to a bonding apparatus. The conical portion 12 is disposed on the tip side of the cylindrical portion 11. The bottleneck portion 13 is formed so that the bonding capillary 110 can bond a fine metal wire to a target position while avoiding contact with an adjacent fine metal wire that has been bonded. The tip surface 50 is an end surface of the bottleneck portion 13 on the tip side.
A hole, into which a fine metal wire (bonding wire) is to be inserted, extends through the bonding capillary 110 in the axial direction. The cylindrical portion 11 has a diameter that allows the bonding capillary 110 to be mechanically fixed to a bonding apparatus. The diameter of the conical portion 12 decreases toward the tip. The conical portion 12 has, for example, a frusto-conical shape. j
The diameter of the conical portion 12 at the boundary between the conical portion 12 and the cylindrical portion- 8 - i
11 is substantially the same as the diameter of the cylindrical portion 11.
As illustrated in FIG. 2, the bottleneck portion 13 is disposed on the tip side of the conical portion 12. The bottleneck portion 13 has such a diameter that the bonding capillary 110 can bond a fine metal wire to a predetermined bonding position while avoiding contact with an adjacent fine metal wire that has been bonded. For example, the diameter of the bottleneck portion 13 decreases from its base portion (on the conical portion 12 side) toward the tip surface 50. In particular, the diameter of the base portion of the bottleneck portion 13 decreases non-linearly.
By decreasing the outside diameter of the bottleneck portion 13, it is possible to perform high-density wire bonding for which the pitch of bonding positions is as small as, for example, 50 micrometers (um) or less. That is, by decreasing the diameter of the bottleneck portion 13, ° even when the pitch of bonding positions is small (when performing high-density wire bonding), it is possible to avoid interference between the bottleneck portion 13 and an adjacent fine metal wire that has been bonded.
As illustrated in FIG. 3, a hole 11h, into which a bonding wire is to be inserted, is formed in the tip surface 50 of the bonding capillary 110. A chamfered portion 13c is located between the hole 11h and the tip
: oo surface 50. The chamfered portion 13c¢ has, for example, a curved surface between the edge of the hole 1lh and the tip surface 50.
FIG. 4 is a schematic sectional view illustrating a state in which wire bonding is performed.
FIG. 4 illustrates a state in which second bonding is performed.
A bonding wire BW (hereinafter, simply referred to as "wire BW"), which has been inserted into the hole 11h in the bonding capillary 110, is first-bonded. Subsequently, the bonding capillary 110 is moved along a predetermined path to a position above a lead 200, so that the wire BW forms a loop.
When the bonding capillary 110 is pressed against the lead 200, the wire BW becomes clamped between the tip surface 50 and the lead 200. Because the tip surface 50 is inclined from its outer periphery toward the edge of the chamfered portion 13c, the distance between the tip surface 50 and the lead 200 decreases from the outside toward the inside of the tip surface 50. Therefore, the thickness of the wire BW, which is clamped between the tip surface 50 and the lead 200, decreases from the outside toward the : inside of the tip surface 50. The wire BW is cut at the edge of the chamfered portion 13c.
While the wire BW is being clamped between the tip surface 50 and the lead 200, for example, ultrasonic vibrations are applied to the bonding capillary 110. Thus, the wire BW is press-bonded to the lead 200. After the wire BW has been press-bonded, the bonding capillary 110 is moved upward. Accordingly, the wire BW connects an electrode pad to the lead 200.
A gripping force between the tip surface 50 and the wire BW 1s an important factor in such a wire bonding operation, because ultrasonic vibrations are applied to the bonding capillary 110 while the tip surface 50 is applying a pressing force to the wire BW. If the gripping force is weak, ultrasonic vibrations are not efficiently applied to a contact area between the wire BW and the lead 200, so that a bonding force between the wire BW and the lead 200 is likely to become weak.
On the other hand, if the pressing force and the amplitude of the ultrasonic vibrations are increased to ensure a sufficient bonding force, the tip surface 50 is likely to wear down. If the tip surface 50 wears down and an appropriate gripping force is not obtained, the bonding capillary 110 needs to be replaced. If the frequency of replacement of the bonding capillary 110 is high, it is necessary to stop the bonding apparatus frequently, and this may lead to an increase in the manufacturing time.
As illustrated in FIG. 3, the tip surface 50 of the bonding capillary 110 according to the embodiment has microscopic asperities. The peaks of the asperities are less sharp than the valleys of the asperities. Therefore, the bonding capillary 110 can maintain an appropriate gripping force for a long time.
Here, the asperities on the tip surface will be described.
FIGS. 5(a) and 5(b) illustrate the asperities on the tip surface 50 according to the embodiment.
FIGS. 6(a) and 6(b) illustrate asperities on a tip surface 51 according to a reference example (1).
FIGS. 7(a) and 7(b) illustrate asperities on a tip surface 52 according to a reference example (2).
FIGS. 5(a), 6(a), and 7(a) are images of the tip surfaces taken by using a three-dimensional scanning electron microscope, showing the measurements of the asperities. FIGS. 5(b), 6(b), and 7(b) conceptually illustrate the roughness profiles of the tip surfaces.
The asperities on the tip surface can be represented by, for example, the mean height Rc and the skewness Rsk.
The mean height Rc and the skewness Rsk are calculated on the basis of JIS B 0601-2001.
In the embodiment, the roughness profile of the tip surface is measured under the following conditions. !
Measurement Apparatus: laser microscope (OLS4000, made ; by Olympus Corporation)
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Measurement Magnification: 50 times
Cutoff (phase-compensation high-pass filter) Ac: 25 Um
The mean height Rc of the roughness profile measured under the above conditions is calculated using equation (1) below, and the skewness Rsk of the roughness profile is calculated using equation (2) below.
Equation 1
Le
Re==YZ7ti = (1) m5
Equation 2 3
Zq N=
In equation (1), m is the number of profile elements, and Zti is the height of each profile element.
In equation (2), Zqg is the root-mean-square height, and Zn the value of the height of the roughness profile.
The mean height Rc of the tip surface 50 according to the embodiment, which is illustrated in FIGS. 5(a) and 5(b), is 60 nanometers (nm) or greater, and the skewness Rsk of the tip surface 50 is in the range of about -1.2 to -0.3.
The mean height Rc of the tip surface 51 of reference ; example (1), which is illustrated in FIGS. 6(a) and 6(b),
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Co is in the range of 10 to 15 nm, and the skewness Rsk of the tip surface 51 is in the range of -0.5 to 0.3.
The mean height Rc of the tip surface 52 of reference example (2), which is illustrated in FIGS. 7(a) and 7(b), is in the range of 150 to 280 nm, and the skewness Rsk of the tip surface 52 is in the range of -0.25 to 0.2.
As described above, the skewness Rsk of the tip surface 50 according to the embodiment is -0.3 or less.
The skewness Rsk may be -1.2 or greater. The skewness Rsk represents the degree of symmetry between the peaks and the valleys of the asperities. If the distribution of the peaks and valleys of the asperities is a sinusoidal distribution, the skewness Rsk is 0. A negative value of the skewness Rsk implies that, when seen in a direction perpendicular to the tip surface 50, the area of peaks is greater than the area of valleys (the peaks are less sharp than the valleys).
The bonding capillary 110 according to the embodiment, which has the tip surface 50, has a high initial bonding strength and a long lifetime. In contrast, the bonding capillary of reference example (1), which has the tip surface 51, does not have a high initial bonding strength.
The bonding capillary of reference example (2), which has the tip surface 52, does not have a long lifetime, although it has a high initial bonding strength.
Because the peaks of the asperities of the tip surface 50 are less sharp than the valleys of the asperities, the bonding capillary 110 has a high initial bonding strength and can maintain the high bonding strength for a long time after repeated bonding operations.
Because the skewness Rsk of the tip surface 50 is negative and the area of the peaks is greater than the area of the valleys, the area of contact between the tip surface 50 and the wire BW is increased. Moreover, because the slopes toward the valleys are steep, the gripping force between the tip surface 50 and the wire BW increases.
Accordingly, the bonding capillary 110 having the tip surface 50 has a sufficient initial bonding strength, high wear resistance, and a long lifetime. The bonding capillary 110 according to the embodiment can achieve a sufficient bonding strength even when bonding a hard wire
BW made of, in particular, copper. Because the tip surface 50 has high wear resistance, the initial bonding strength can be maintained for a long time even when wire bonding using a hard wire BW made of copper or the like is repeatedly performed. (EXAMPLES)
Next, Examples of the bonding capillary 110 according to the embodiment will be described.
FIG. 8 is a table showing the results of evaluating
Examples and Comparative Examples.
FIG. 9 is a schematic perspective view illustrating a measurement region.
FIG. 8 shows the mean height Rc, the skewness Rsk, and the maximum peak height Rp of tip surfaces of Examples 1 to 6 and Comparative Examples 1 to 8.
The mean height Rc, the skewness Rsk, and the maximum peak height Rp for each of these Examples and Comparative
Examples were measured in a surface region 50r shown in FIG. 9. As illustrated in FIG. 9, the surface region 50r is a region of the tip surface 50 within a length L1 from the edge of the chamfered portion 13c in a direction away from the hole 11h along the tip surface 50. The length L1 is at least 20 um. A measurement length L2 is about 100 pm within the surface region 50r. In the embodiment, the roughness of the tip surface 50 along each of three lines in the surface region 50r, each line having the measurement length L2 of 100 um, was measured; and the average of the measurements was obtained.
Cpk of bonding strength shown in FIG. 8 is the process capability index. In the Examples and Comparative Examples shown in FIG. 8, Cpk = (Ave - 3gf)/36, where Ave is the average bonding strength of the wire BW and 3 gram- force (gf) is the lower specification limit of the bonding strength. The bonding strength was measured in a pull test
C16 -
-
Co for second bonding. The number of samples was 30. In general, it 1s required that Cpk of bonding strength of wire bonding be 1.67 or greater.
As shown in FIG. 8, the combinations of the mean height Rc, the skewness Rsk, and the maximum peak height Rp for Examples 1 to 6 and Comparative Examples 1 to 8 differ from each other. For Examples 1 to 6 and Comparative
Examples 4 to 8, Cpk of bonding strength was 1.67 or greater.
FIG. 10 is a table showing the results of evaluating bonding strength.
FIG. 10 shows the results of evaluating the bonding strength for Examples 1 to 6 and Comparative Examples 4 to 6, for which Cpk of bonding strength was 1.67 or greater, as shown in FIG. 8.
The evaluation of bonding strength was determined on the basis of whether or not Cpk in the initial stage, Cpk after wire bonding was performed 500 thousand times, Cpk after wire bonding was performed 1000 thousand times, and
Cpk after wire bonding was performed 1500 thousand times were less than 1.67. In the evaluation of bonding strength shown in FIG. 10, "OK" denotes a case where Cpk was 1.67 or greater, and "NG" denotes a case where Cpk was less than 1.67.
As shown in FIG. 10, the evaluations of bonding strength in the initial stage were all "OK" for Examples 1 to 6 and Comparative Examples 4 to 6. After wire bonding : was performed 500 thousand times, the evaluations for
Examples 1 to 6 were "OK", but the evaluations for
Comparative Examples 4 to 6 were "NG". After wire bonding was performed 1000 thousand times, the evaluations for
Examples 1 to 3, 5, and 6 were "OK", but the evaluations for Examples 4 and Comparative Examples 4 to 6 were "NG".
After wire bonding was performed 1500 thousand times, the evaluations for Examples 5 and 6 were "OK", but the evaluations for Examples 1 to 4 and Comparative Examples 4 to 6 were "NG".
FIGS. ll(a) and 11(b) are graphs showing the change in
Cpk as the number of times bonding was performed varied.
FIG. 1ll(a) represents the change in Cpk for Example 2 shown in FIGS. 8 and 10. FIG. 11(b) represents the change in Cpk for Comparative Example 6 shown in FIGS. 8 and 10.
As illustrated in FIG. 1ll(a), for a bonding capillary having a tip surface of Example 2, the initial bonding strength was maintained and Cpk continued to be 1.67 or greater after wire bonding was performed 1000 thousand times.
In contrast, as illustrated in FIG. 11(b), for a bonding capillary having a tip surface of Comparative
Example 6, although Cpk in the initial stage of bonding was 1.67 or greater, Cpk sharply decreased to become lower than 1.67 after wire bonding was performed about 300 thousand times.
On the basis of the results described above, it is preferable that the skewness Rsk of the tip surface 50 be in the range of about -1.2 to -0.3 and the mean height Rc of the tip surface 50 be in the range of 0.06 to 0.3 pm.
If the mean height Rc is less than 0.06 um, the gripping force is small and in particular, when bonding a wire BW made of copper, a sufficient bonding strength cannot be obtained. If the mean height Rc is greater than 0.3 um, it is difficult to form asperities for which the skewness Rsk is -0.3 or less. It is more preferable that the skewness
Rsk of the tip surface 50 be in the range of about -1.2 to -0.43 and the mean height Rc of the tip surface 50 be in the range of 0.16 to 0.3 um. In this case, the initial bonding strength can be maintained after wire bonding is performed 1500 thousand times.
It is preferable that the maximum peak height Rp of the tip surface 50 be 0.9 times the mean height Re or less (Rp/Rc £ 0.9). The Rp/Rc may be 0.5 or greater. If Rp/Rc is greater than 0.9, it is difficult to maintain the initial bonding strength for a long time. If Rp/Rc is 0.9 or less, change in the shape of the tip surface 50 due to wear during use is small, so that the initial bonding :
strength can be maintained for a long time. (Manufacturing Method)
Next, a method of manufacturing the bonding capillary 110 according to the embodiment will be described.
FIGS. 12(a) and 12(b) illustrate part of the method of manufacturing the bonding capillary 110.
FIGS. 12 (a) and 12(b) illustrate steps of the method of manufacturing the bonding capillary 110 for forming asperities on the tip surface 50.
The material of the bonding capillary 110 according to the embodiment includes, for example, aluminum oxide ( Al,03) and zirconium dioxide (Zr0,). As illustrated in
FIG. 12(a), in the bonding capillary 110, ZrO, grains having smaller grain diameters are dispersed in Al,0; grains having larger grain diameters. When the tip surface 50 is polished, ZrO, crystals become exposed on the surface of an
Al,03 base material at the tip surface 50.
In this state, the tip surface 50 is sandblasted.
Examples of conditions of sandblasting include the type of abrasive, the blasting pressure, and the blasting time. By optimizing the conditions of sandblasting, ZrO, crystals, which are softer than Al,0;, come off the surface of the
Al,;0; base material. Thus, as illustrated in FIG. 12(b), valleys are formed in parts of a flat portion of the tip surface 50. At this time, because the ratio of ZrO, to the :
Al,0; base material is low, the area of valleys, which are formed when ZrO, crystals come off the surface of the Al,0; base material, does not become greater than the area of peaks (flat surface).
The manufacturing method described above is only an example, and the bonding capillary 110 may be made by using a method other than sandblasting. (Crystal Grain Diameter)
Next, the crystal grain diameter of a bonding capillary will be described.
In the bonding capillary 110 according to the embodiment, the mean grain diameter of ceramic crystals exposed on the tip surface 50 is 1.2 um or less. The mean grain diameter of ceramic crystals may be 0.3 um or greater.
When the mean grain diameter of ceramic crystals is 1.2 um or less, wear of the tip surface 50 is decreased and the lifetime of the bonding capillary 110 is increased.
FIG. 13 illustrates a method of measuring the mean grain diameter of ceramic crystals.
FIG. 13 shows a scanning electron microscope (SEM) image of a surface of a ceramic sample that has been polished and then thermally etched to make the boundaries between grains clearly visible.
First, any appropriate portion of the sample is observed by using a SEM with a magnification in the range a of about 10000 to 30000 times, and a SEM image of the portion is obtained. The mean grain diameter is calculated using, for example, a planimetric method on the basis of the obtained SEM image.
The mean grain diameter is calculated as follows.
First, a circle CIR having an area A (um’) is drawn on the obtained SEM image. Next, the number nc of grains : within the circle CIR and the number ni of grains on the circumference of the circle CIR are counted. By using nc and ni, the mean grain diameter is calculated using the following equations.
N = (nc + (1/2)ni)/(A/magnification?)
The mean grain diameter (pum) = 2/(m-N)!/?
FIG. 14 is a table showing the relationship between the mean grain diameter of ceramic crystals and the lifetime of a bonding capillary.
FIG. 14 shows the results of evaluating the lifetimes of bonding capillaries having different mean grain diameters after bonding was performed different numbers of times. Wire bonding was performed 500 thousand times and 1000 thousand times. The lifetime was evaluated as "OK" if
Cpk was 1.67 or greater and as "NG" if Cpk was less than 1.67.
From the results shown in FIG. 14, it is preferable that the mean grain diameter of ceramic crystals be in the
I ot range of about 0.3 to 1.2 um in order that Cpk of 1.67 or greater is maintained after wire bonding is performed 500 thousand times. It is more preferable that the mean grain diameter be in the range of about 0.3 to 0.7 um. When the mean grain diameter is 0.7 pum or less, Cpk of 1.67 or greater is maintained after wire bonding is performed 1000 thousand times.
By making the bonding capillary 110 from a ceramic having crystals with such a mean grain diameter, wear of the tip surface 50 is reduced. Thus, the lifetime of the bonding capillary 110 is increased, and the frequency of replacement of the bonding capillary is reduced.
As heretofore described, with the embodiment, the wire
BW and the lead 200 can be bonded to each other with a sufficient bonding strength in wire bonding. Moreover, the initial bonding strength can be maintained for a long time while wire bonding is repeatedly performed.
The invention is not limited to the embodiment described above. Modifications of the embodiment that are made by a person having ordinary skill in the art are included in the scope of the invention .as long as the : modifications have the features of the invention. For example, the shape, the size, and the material of the bonding capillary 110 are not limited to those in the embodiment described above, and can be changed as appropriate.
Reference Signs List 10: body 11: cylindrical portion 11h: hole 12: conical portion 13: bottleneck portion 13c: chamfered portion 50: tip surface 50r: surface region 110: bonding capillary 200: lead
BW: wire
CIR: circle

Claims (6)

  1. ‘0 - [CLAIMS]
    [Claim 1] A bonding capillary comprising: a body having a tip surface that performs wire bonding, wherein the tip surface has microscopic asperitidg, NV -4 Pl wherein peaks of the asperities are less sharp than valleys of the asperities, wherein, when seen in a direction perpendicular t he tip surface, the area of the peaks is greater than the area of the valleys, and wherein a skewness of the tip surface is -0.3 or less, and a mean height of the tip surface is in the range of 0.06 to 0.3 micrometers.
  2. [Claim 2] A bonding capillary comprising: a body having a tip surface that performs wire bonding, wherein the tip surface has microscopic asperities, wherein peaks of the asperities are less sharp than valleys of the asperities, wherein a skewness of the tip surface is -0.43 or less, and a mean height of the tip surface is in the range of 0.16 to 0.3 micrometers, and wherein, when seen in a direction perpendicular to the tip surface, the area of the peaks is greater than the area of the valleys.
  3. [Claim 3] The bonding capillary according to Claim 1 or 2, wherein a maximum peak height of the tip surface is 0.9 times the mean height or less. ;
  4. [Claim 4] The bonding capillary according to Claim 1 or 2, wherein a mean grain diameter of crystals exposed on the tip surface is 1.2 micrometers or less.
  5. [Claim 5] The bonding capillary according to Claim 1 or 2, wherein the body has a hole, into which a bonding wire is to be inserted, formed in the tip surface, and a chamfered portion located between the hole and the tip surface, and wherein the asperities of the tip surface are defined by means of a roughness profile that is measured along a length of at least 100 micrometers in a surface region of the tip surface, the surface region extending at least 20 micrometers from an edge of the chamfered portion away from the hole along the tip surface.
  6. [Claim 6] The bonding capillary according to Claim 1 or 2, wherein a maximum peak height of the tip surface is 0.9 times the mean height or less, wherein a mean grain diameter of crystals exposed on the tip surface is 1.2 micrometers or less, wherein the body has a hole, into which a bonding wire is to be inserted, formed in the tip surface, and a chamfered portion located between the hole and the tip surface, and wherein the asperities of the tip surface are defined by means of a roughness profile that is measured along a length of at least 100 micrometers in a surface region of the tip surface, the surface region extending at least 20 micrometers ; from an edge of the chamfered portion away from the hole along the tip surface.
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JP6126144B2 (en) * 2014-06-30 2017-05-10 Toto株式会社 Bonding capillary
USD771168S1 (en) 2014-10-31 2016-11-08 Coorstek, Inc. Wire bonding ceramic capillary
USD797171S1 (en) 2015-02-03 2017-09-12 Coorstek, Inc. Ceramic bonding tool with textured tip
USD797172S1 (en) 2015-02-03 2017-09-12 Coorstek, Inc. Ceramic bonding tool with textured tip
USD797826S1 (en) 2015-02-03 2017-09-19 Coorstek, Inc. Ceramic bonding tool with textured tip
USD753739S1 (en) 2015-04-17 2016-04-12 Coorstek, Inc. Wire bonding wedge tool
JP6064308B2 (en) * 2015-07-03 2017-01-25 Toto株式会社 Bonding capillary
WO2017006880A1 (en) * 2015-07-03 2017-01-12 Toto株式会社 Bonding capillary
IL264627B2 (en) 2016-08-08 2023-04-01 Asml Netherlands Bv Electron emitter and method of fabricating same
USD868123S1 (en) 2016-12-20 2019-11-26 Coorstek, Inc. Wire bonding wedge tool
JP7407751B2 (en) * 2021-01-27 2024-01-04 三菱電機株式会社 Wire bonding equipment and semiconductor device manufacturing method
CN114309920A (en) * 2021-12-23 2022-04-12 潮州三环(集团)股份有限公司 Ceramic cleaver and preparation method thereof

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US7389905B2 (en) * 1999-02-25 2008-06-24 Reiber Steven F Flip chip bonding tool tip
US6910612B2 (en) * 2001-07-17 2005-06-28 Kulicke & Soffa Investments, Inc. Capillary with contained inner chamfer
TWI229021B (en) * 2002-06-12 2005-03-11 Shi-Tong Yang Welding head of spot welding machine
WO2008005684A2 (en) * 2006-07-03 2008-01-10 Kulicke And Soffa Industries, Inc. Bonding tool with improved finish

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JP2014082450A (en) 2014-05-08
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PH12013000287A1 (en) 2015-04-06

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