TW201601229A - Solder pin - Google Patents

Abstract

The object of the present is to inhibit cracks on a solder wire and improve bonding strength at the same time. The solution according to an embodiment of the present invention is to provide a solder pin which is characterized by comprising: a pressing surface for pressing a solder wire; an insertion hole with the solder wire inserted therethrough; a tapered hole connected to the insertion hole and the pressing surface and expanding toward the pressing surface; and a chamfered portion disposed between the tapered hole and the pressing surface. The surface of the chamfered portion has a concave-convex shape. Sharpness of a convex portion of the concave-convex shape is less than that of a concave portion of the concave-convex shape.

Description

Solder pin

The disclosed embodiment relates to a bonding capillary.

One of the methods for electrically connecting a semiconductor wafer to a lead frame has been known as wire bonding. Wire bonding is a method of electrically connecting a semiconductor wafer and a lead frame by arranging a metal wire called a bonding wire between the electrodes of the semiconductor wafer and the lead frame.

A cylindrical tool called a welding pin is used in the wire bonding. Specifically, the wire is passed through the inside of the welding pin and protruded from the tip end, and the protruding wire is pressed against the electrode using the tip end surface of the welding pin. Further, ultrasonic waves are applied to the welding pins to vibrate the tip end surface, and the bonding wires are applied to the electrodes. According to this, the bonding wire is bonded to the electrode.

In order to prevent the bonding wire from adhering to the tip end surface, it is known that the R portion having a predetermined curvature is provided around the opening of the insertion hole through which the bonding wire is inserted (see, for example, Patent Document 1).

[Patent Document 1] Japanese Patent Publication No. 9-326411

However, when the wire bonding is performed using the welding pin having the above-described R portion, it is difficult to obtain the joint strength. This is because it is difficult to apply the bonding wire to the electrode because the holding force of the wire is lowered due to the provision of the R portion.

The problem of such joint strength becomes remarkable in the case of wire bonding using a bonding wire made of Al (aluminum). This is because Al is easily oxidized as compared with Au (gold) which is generally used as a material of the bonding wire, and bonding to the electrode is easily hindered by the oxide film formed on the surface.

Further, in the bonding wire made of Al, there is a problem that cracks are likely to occur in comparison with the bonding wire made of Au. Therefore, in the case where wire bonding is performed using a bonding wire made of Al, it is preferable to increase the bonding strength and suppress the occurrence of cracks.

An object of the embodiment is to provide a welding pin which can suppress the occurrence of cracks in the bonding wire and at the same time improve the bonding strength.

A welding pin according to an embodiment of the embodiment, comprising: a pressing surface for pressing the bonding wire; an insertion hole through which the bonding wire is inserted; connecting the insertion hole and the pressing surface toward the foregoing a tapered hole extending from the pressing surface; a chamfered portion provided between the tapered hole and the pressing surface, wherein the chamfered portion has a concave-convex shape on the surface, and the sharpness of the convex portion in the concave-convex shape is longer than the foregoing The sharpness of the concave portion in the uneven shape is small.

Since the stress applied to the bonding wire can be relieved by providing a chamfered portion between the tapered hole and the pressing surface, generation of cracks in the bonding wire can be suppressed. Further, since the uneven shape can be provided on the surface of the chamfered portion, the gripping force against the bonding wire when the bonding wire is applied to the electrode can be improved, so that the bonding strength can be improved. On the other hand, in the case where only the uneven shape is provided, the wire is scratched due to the sharpness of the convex portion in the uneven shape, and the metal wire is likely to be cracked due to the flaw. Therefore, the sharpness of the convex portion in the uneven shape is made smaller than the sharpness of the concave portion. According to this, it is possible to suppress the occurrence of cracks due to the uneven shape.

Further, the concavo-convex shape of the chamfered portion has a skewness of -0.164 or less and an average height of 0.035 μm or more and 0.092 μm or less.

According to this, in the case where the wire bonding is performed using the bonding wire made of Al, it is possible to suitably suppress the occurrence of cracks after the first bonding process on the bonding wire. Moreover, sufficient joint strength can be obtained in the tail portion after the second bonding process.

Further, the pressing surface has a concavo-convex shape, and the sharpness of the convex portion in the concavo-convex shape of the pressing surface is larger than the sharpness of the convex portion in the concavo-convex shape of the chamfered portion.

It is difficult to cause cracks to be generated on the weld line when the pressing surface is opposite to the chamfered portion. Therefore, in the pressing surface, the above-described configuration may be employed in view of the improvement of the gripping force rather than the prevention of the occurrence of cracks. With the above configuration, the gripping force on the bonding wire can be further improved.

Further, the uneven shape in the pressing surface has an average height of 0.113 μm or more.

According to this, in the case where the wire bonding is performed using the bonding wire made of Al, a sufficient bonding strength can be obtained in the stitch portion after the second welding process.

Further, the chamfered portion has a curved surface that smoothly continues to the tapered hole and the pressing surface, and the curved surface has a radius of curvature of 4.55 μm or more and 20.30 μm or less.

According to this, in the case where the wire bonding is performed using the bonding wire made of Al, it is possible to suitably suppress the occurrence of cracks in the bonding wire. Further, it is possible to suitably suppress the occurrence of the cutting failure of the bonding wire after the second welding process.

Further, the chamfered portion has a curved surface that smoothly continues to the tapered hole and the pressing surface, and the curved surface has a radius of curvature of 12.8 μm or more and 20.30 μm or less.

According to this, in the case where the wire bonding is performed using the bonding wire made of Al, even if the loop length of the bonding wire is 3 mm or more, it is possible to suitably suppress the occurrence of cracks in the bonding wire. Further, it is possible to suitably suppress the occurrence of the cutting failure of the bonding wire after the second welding process.

Further, it is characterized in that the taper angle of the tapered hole is 100 or less.

According to this, in the boundary corner portion between the insertion hole and the tapered hole, it is possible to suitably suppress the occurrence of cracks in the bonding wire.

Further, the outer diameter of the pressing surface is 4.0 times or more and 5.7 times or less the wire diameter of the bonding wire.

According to this, the desired joint strength can be obtained.

According to an aspect of the embodiment, it is possible to suppress the occurrence of cracks in the bonding wire and to improve the bonding strength.

Hereinafter, an embodiment of the welding pin disclosed in the present invention will be described in detail with reference to the accompanying drawings. Further, the present invention is not limited by the embodiments described below.

(Embodiment) First, the overall configuration of a welding pin according to this embodiment will be described with reference to Figs. 1 and 2 . Fig. 1 is a schematic side view showing a welding pin according to the embodiment. 2 is a schematic enlarged view of the H1 portion shown in FIG. 1.

As shown in Fig. 1, the welding pin 1 (hereinafter referred to as "welding pin 1") according to the present embodiment has an insertion hole 11 through which a bonding wire (hereinafter referred to as "metal wire") is inserted. Further, the welding pin 1 is formed by, for example, ceramic. The material of the welding pin 1 is, for example, alumina or the like. Alternatively, as the material of the welding pin 1, a composite material containing alumina and at least one of zirconia and chromia may be mentioned.

The welding pin 1 includes a cylindrical portion 12, a conical portion 13, and a neck portion 14. The conical portion 13 is a portion disposed at one end of the cylindrical portion 12 and has a shape that is reduced in diameter toward the distal end side. The neck portion 14 is a portion disposed at the distal end of the conical portion 13 and has a smaller diameter than the distal end diameter of the conical portion 13 . The insertion hole 11 is provided to penetrate the cylindrical portion 12, the conical portion 13, and the neck portion 14.

As shown in FIG. 2, a tapered hole 20 is provided between the pressing surface 30 of the tip end surface of the neck portion 14 and the insertion hole 11. The tapered hole 20 is tapered in such a manner as to expand from the insertion hole 11 toward the pressing surface 30.

The welding pin 1 configured as described above presses the wire protruding from the tapered hole 20 to the outside by using the pressing surface 30, and the pressing surface 30 is vibrated by ultrasonic waves to apply the metal wire to the electrode to make the metal The wire is bonded to the electrode.

Here, as the material of the metal wire, Au (gold) is generally used. In this regard, a pad electrode of an electrode of a semiconductor wafer is generally made of Al (aluminum). When the dissimilar metals are bonded to Au and Al in this manner, voids are generated at the joint interface to lower the joint strength. Moreover, since expensive Au is used, there is also a problem that the manufacturing cost of a semiconductor device becomes high.

Therefore, in recent years, use of a material which is the same as a pad electrode of a semiconductor wafer and which is cheaper than Au is used as a metal wire has been proposed.

However, Al has a lower strength than Au. Therefore, after the first welding procedure described later, there is a problem that cracks are likely to occur in the bent portion of the metal wire. Further, Al is more likely to be oxidized than Au, and the bonding to the electrode is easily hindered by the oxide film formed on the surface. Therefore, there is also a problem that sufficient joint strength is not easy.

Therefore, in the welding pin 1 according to the present embodiment, the chamfered portion is provided at the boundary portion between the pressing surface 30 and the tapered hole 20, and the occurrence of cracks in the bent portion of the wire is suppressed. Further, in the welding pin 1 according to the present embodiment, by providing a fine uneven shape on the chamfered portion, the pressing surface 30 is vibrated to improve the gripping force on the metal wire when the metal wire is applied to the electrode. Thereby the joint strength is increased.

On the other hand, in the case where only the uneven shape is provided, the metal wire is damaged due to the sharpness of the convex portion in the uneven shape, and the metal wire is likely to be cracked due to the damage of the metal wire. Therefore, in the welding pin 1 according to the present embodiment, the sharpness of the convex portion in the uneven shape is made smaller than the sharpness of the concave portion. According to this, it is possible to suppress the occurrence of cracks due to the uneven shape. Further, [sharpness] means the degree of sharpness of the convex portion and the concave portion. Therefore, [making the sharpness of the convex portion smaller than the sharpness of the concave portion] means that the sharpness of the convex portion is sharper than the sharpness of the concave portion.

Hereinafter, the configuration of the chamfered portion formed at the boundary portion between the pressing surface 30 and the tapered hole 20 and the uneven shape formed on the surface of the chamfered portion will be specifically described with reference to FIGS. 3 and 4 . 3 is a schematic side cross-sectional view showing a tip end portion of the neck portion 14. 4 is a schematic enlarged view of the H2 portion shown in FIG. 3.

As shown in FIG. 3, the pressing surface 30 is formed in a convex shape which is slightly raised from the outer edge portion toward the central portion. Further, a tapered hole 20 is formed in a central portion of the pressing surface 30. Therefore, in the welding pin 1, the boundary portion between the tapered hole 20 and the pressing surface 30 is the portion which most protrudes from the tip end side, in which the metal wire is liable to be cracked.

The chamfered portion 40 is provided at a boundary portion between the tapered hole 20 and the pressing surface 30. As shown in FIG. 4, the chamfered portion 40 has a curved surface that is smoothly continuous from the tapered hole 20 to the pressing surface 30.

Fig. 5 is a schematic side sectional view showing the surface shape of the pressing surface 30. Moreover, FIG. 6 is a schematic side cross-sectional view showing the surface shape of the chamfered portion 40. As shown in FIGS. 5 and 6, the pressing surface 30 and the chamfered portion 40 are formed with a fine uneven shape on the surface. These uneven shapes are formed such that the sharpness of the convex portions 31 and 41 is smaller than the sharpness of the concave portions 32 and 42.

Further, the uneven shape of the pressing surface 30 shown in FIG. 5 is formed such that the sharpness of the convex portion 31 is larger than the sharpness of the convex portion 41 in the uneven shape of the chamfered portion 40 shown in FIG. 6 . According to this, in the welding pin 1 according to the present embodiment, the gripping force of the pressing wire 30 against the wire can be improved more than the gripping force of the opposing wire of the chamfering portion 40.

Next, the action of the above configuration will be described with reference to FIGS. 7 and 8 together with the operation of the wire bonding. Fig. 7 is a schematic side sectional view showing the state of the first welding procedure. Moreover, Fig. 8 is a schematic side sectional view showing the state of the second welding program.

The wire bonding includes a first welding process, a loop forming process, and a second welding process. The first welding procedure is a procedure for joining metal wires to one of the electrodes. The line arc forming program is a program for forming a line arc of a metal line between electrodes by moving the welding pin 1 in a predetermined orbit after the first welding procedure. The second welding procedure is a procedure in which the wire is joined to the other electrode after the in-line arc forming process. By these procedures, a metal wire is placed between the electrodes to electrically connect the semiconductor wafer to the lead frame.

FIG. 7 shows a first welding in the case where wire bonding is performed by using a metal wire made of Au (hereinafter referred to as [Au metal wire]) and using a metal wire made of Al (hereinafter referred to as [Al metal wire]). The look of the program.

Here, in the wire bonding using the conventional Au metal wire, the first welding process performs ball bonding. The spherical bonding is a method in which a tip of a metal wire is melted by discharge to form a ball of Au, and a metal wire is bonded to the electrode by thermocompression bonding the electrode to the electrode. A soldering pin is used for the ball joint.

On the other hand, when the wire bonding is performed using an Al metal wire, it is difficult to perform the above-described spherical bonding. This is because Al and Au are more susceptible to oxidation and it is difficult to form a ball like Au. Therefore, in the case of wire bonding using an Al metal wire, a wedge bonding tool in which a metal wire is bonded to an electrode without forming a ball is generally used (for example, refer to Japanese Laid-Open Patent Publication No. 2001-156100).

However, since the wedge bonding tool is complicated in structure compared with the welding pin, it is expensive and has low durability. Therefore, in the present embodiment, it is intended to perform wire bonding using an Al metal wire using a welding pin 1 of a welding pin which is relatively inexpensive and has high durability as a wedge bonding tool. According to this, the productivity of the semiconductor element can be improved.

As shown in FIG. 7, the welding pin 1 first presses the Al metal wire W to one of the electrodes, such as the lead electrode 100 of the lead frame, using the pressing surface 30. At this time, a predetermined interval is provided between the chamfered portion 40 and the wire electrode 100 so that the Al metal wire W is not cut between the chamfered portion 40 and the wire electrode 100.

Next, the cylindrical portion 12 (see FIG. 1) of the welding pin 1 is pressed with ultrasonic waves. According to this, the pressing surface 30 vibrates the Al metal wire W to be applied to the wire electrode 100. According to this, the Al metal wire W is bonded to the wire electrode 100.

Next, the welding pin 1 moves while drawing a predetermined track to form a line arc of the metal wire. At this time, a bent portion is formed at a boundary between a portion of the wire electrode 100 bonded to the Al metal wire W and a portion not joined, for example, the region B shown in FIG. Cracks are easily generated in the bent portion.

In this case, in the welding pin 1 according to the present embodiment, the chamfered portion 40 is provided at a boundary portion between the tapered hole 20 and the pressing surface 30. According to this, the stress concentration in the region B is moderated as compared with the case where the chamfered portion 40 is not provided, and it is possible to suppress the occurrence of cracks in the bent portion of the Al metal wire W.

Further, as described above, since the Al metal wire W is easily prevented from being bonded to the electrode by the oxide film formed on the surface, it is difficult to obtain a sufficient bonding strength than the Au metal wire.

In this case, in the welding pin 1 according to the present embodiment, it is intended to provide a fine uneven shape on the surface of the chamfered portion 40. As a result, the gripping force of the chamfered portion 40 against the Al metal wire W is improved. Therefore, even when the Al metal wire W having difficulty in obtaining joint strength is used as compared with the Au metal wire, sufficient joint strength can be obtained.

Further, the concavo-convex shape of the chamfered portion 40 is formed such that the sharpness of the convex portion 41 is smaller than the sharpness of the concave portion 42. Therefore, according to the welding pin 1 according to the present embodiment, it is possible to suppress the occurrence of cracks due to the uneven shape and to obtain high joint strength.

Further, in the welding pin 1 according to the present embodiment, it is also intended to provide a fine uneven shape on the pressing surface 30. It is difficult for the pressing surface 30 to cause cracks in the Al metal wire W as compared with the chamfered portion 40. Therefore, from the viewpoint of paying attention to the improvement of the gripping force rather than the prevention of the occurrence of cracks, the uneven shape of the pressing surface 30 has a sharpness of the convex portion 31 larger than the sharpness of the convex portion 41 in the uneven shape of the chamfered portion 40. Formed (see Figures 5 and 6). According to this, the gripping force to the Al metal wire W can be further improved.

Next, the welding pin 1 performs a second welding process. First, as shown in FIG. 8, the welding pin 1 presses the Al metal wire W to the other electrode, for example, the pad electrode 200 of the semiconductor wafer, using the pressing surface 30. In the second soldering process, after the Al metal wire W is bonded to the pad electrode 200, the Al metal wire W needs to be cut. Therefore, the interval between the chamfered portion 40 and the pad electrode 200 is set to be shorter than that in the first welding procedure.

Next, the welding pin 1 vibrates the pressing surface 30 by ultrasonic waves to apply the Al metal wire W to the pad electrode 200. According to this, the Al metal wire W is bonded to the pad electrode 200.

Then, the welding pin 1 is raised only by a predetermined distance. As shown in FIG. 8, the Al metal wire W is also joined to the pad electrode 200 in the tail portion T on the inner side of the chamfered portion 40, not only in the seam portion S outside the chamfered portion 40 but also in the slit portion S outside the chamfered portion 40. . Therefore, as the welding pin 1 rises, the rising Al metal wire W is drawn by the welding pin 1. The drawn Al metal wire W is a portion joined to the wire electrode 100 in the next first welding process.

Then, the Al metal wire W is cut between the sewing portion S and the tail portion T by, for example, the welding needle 1 moving left and right.

Thus, in order to extract the Al metal wire W from the welding pin 1 in the second welding process, the Al metal wire W needs to be temporarily joined to the pad electrode 200 in the tail portion T. However, as described above, since the oxide film is easily formed on the Al metal wire W, it is not easy to secure the bonding strength of the tail portion T.

On the other hand, in the welding pin 1 according to the present embodiment, by providing the fine concavo-convex shape in the chamfered portion 40, the gripping force on the Al metal wire W of the chamfered portion 40 can be increased, so that the tail portion T is A good joint strength can also be obtained.

As described above, the welding pin 1 according to the present embodiment includes the pressing surface 30, the insertion hole 11, the tapered hole 20, and the chamfered portion 40. The pressing surface 30 is a surface that presses the bonding wire. The insertion hole 11 is a hole through which the above-mentioned bonding wire is inserted. The tapered hole 20 is a hole that connects the insertion hole 11 and the pressing surface 30, and has a shape that expands toward the pressing surface 30. The chamfered portion 40 is disposed between the tapered hole 20 and the pressing surface 30. The chamfered portion 40 has a concavo-convex shape on the surface, and the sharpness of the convex portion 41 in the concavo-convex shape is smaller than the sharpness of the concave portion 42 in the concavo-convex shape.

Therefore, according to the welding pin 1 according to the present embodiment, it is possible to suppress the occurrence of cracks in the bonding wire and to improve the bonding strength.

(Embodiment) Next, an embodiment of the welding pin 1 according to the present embodiment will be described with reference to Figs. 9 to 11 . Fig. 9 is a graph illustrating a roughness curve of the surface of the chamfered portion. FIG. 10 is a view showing evaluation results of a case where the skewness and the average height of the uneven shape in the chamfered portion 40 and the average height of the uneven shape in the pressed surface 30 are changed. Moreover, FIG. 11 is a view showing an evaluation result of a case where the radius of curvature of the chamfered portion 40 is changed.

The uneven shape of the pressing surface 30 and the chamfered portion 40 is expressed by, for example, an average height Rc and a skewness Rsk. The average height Rc and the skewness Rsk are calculated in accordance with JIS B 0601-2001.

The skewness Rsk is a value indicating the symmetry of the convex portion and the concave portion in the uneven shape. If the uneven shape is symmetrical, the skewness Rsk becomes zero. Further, when the skewness Rsk is negative, the sharpness of the convex portion in the uneven shape is smaller than the sharpness of the concave portion, in other words, the area of the tip end portion of the convex portion in the case where the uneven shape is viewed in a plan view is larger than the concave portion The bottom portion has a large area.

In the present embodiment, the roughness curves of the pressing surface 30 and the chamfered portion 40 were measured using a laser microscope (OLS4000, manufactured by OLYMPUS). The measurement conditions are as follows: Measurement magnification: 50 times Evaluation length (roughness measurement): 500 μm to 800 μm Cutoff (phase compensation type high-pass filter) λc: 25 μm

From the roughness curve measured by the above conditions, the average height Rc is obtained by the following formula (1), and the skewness Rsk is obtained by the following formula (2).

Formula 1)

Formula (2)

Here, in the formula (1), m is the number of contour curve elements, and Zti is the average value of the heights of the contour curve elements. Further, in the formula (2), Zq is a root mean square height, and Zn is a value of a height in the roughness curve.

An example of the roughness curve obtained by measuring the surface of the chamfered portion 40 by a laser microscope is shown in Fig. 9 . In Fig. 9, the vertical axis represents the height (micrometer: μm), and the horizontal axis represents the measurement position (μm). In the roughness curve shown in FIG. 9, the skewness Rsk of the uneven shape of the chamfered portion 40 is -0.164, and the average height Rc of the uneven shape of the chamfered portion 40 is 0.073.

FIG. 10 shows items of [crack], [tail joint], and [sewing joint] in the case where the skewness Rsk and the average height Rc of the chamfered portion 40 and the average height Rc of the pressing surface 30 are changed, respectively. Evaluation results.

Here, the [crack] item is an item indicating whether or not a crack has occurred in the Al metal wire W after the first welding procedure. The case where no crack is generated in the [crack] item is [○]. Further, the [tail joint] item and the [stitch joint] item are items indicating whether or not sufficient joint strength is obtained in the tail portion T and the seam portion S shown in Fig. 8 after the second welding program. In the [tail joint] item and the [stitch joint] item, the case where sufficient joint strength is obtained is [○].

As shown in FIG. 10, in Comparative Examples 1 and 2, sufficient joint strength could not be obtained in the tail portion T and the seam portion S after the second welding procedure. Further, in Comparative Examples 3 to 6, cracks occurred in the Al metal wire W after the first welding process.

On the other hand, in the first to fifth embodiments, the Al metal wire W after the first welding process was not cracked, and sufficient joint strength was obtained in the tail portion T and the seam portion S after the second welding process. .

As a result, the uneven shape in the chamfered portion 40 has a skewness Rsk of -0.164 or less, and an average height Rc of preferably 0.035 μm or more and 0.092 μm or less. Further, the average height Rc of the uneven shape in the pressing surface 30 is preferably 0.113 μm or more.

When the skewness Rsk of the uneven shape in the chamfered portion 40 is less than -1.4, the average height Rc of the chamfered portion 40 is, for example, 0.035 μm or more, which is difficult in the processing principle. Therefore, it is preferable that the skewness Rsk of the uneven shape in the chamfered portion 40 is -1.4 or more.

The average height Rc of the concavo-convex shape in the pressing surface 30 can be 4.462 μm or less. When the average height Rc of the uneven shape in the pressing surface 30 is higher than 4.642 μm, the uneven shape having an average height Rc of 0.092 μm or more after the chamfered portion 40 is formed tends to remain in the chamfered portion 40. Therefore, the average height Rc of the uneven shape in the pressing surface 30 is preferably 4.642 μm or less. Further, the average height Rc 4.642 μm of the concavo-convex shape in the pressing surface 30 is the average height of the concavo-convex shape in the chamfered portion 40 by the lower limit value of the radius of curvature of the chamfered portion 40 of 4.55 μm (refer to FIG. 11). The upper limit value of Rc is 0.092 μm (see Fig. 10) and is added.

The concavo-convex shape in the pressing surface 30 is formed, for example, by sandblasting. When the concavo-convex shape in the pressing surface 30 is formed by sandblasting, the average height Rc of the concavo-convex shape of the pressing surface 30 can be made 0.45 μm. When the average height Rc of the concavo-convex shape of the pressing surface 30 is more than 0.45 μm, for example, ceramic particles on the surface tend to be lost (particle falling off). Therefore, the average height Rc of the uneven shape in the pressing surface 30 is preferably 0.45 μm or less.

FIG. 11 shows the evaluation results of the respective items of [crack] and [metal wire cutting failure] in the case where the radius of curvature of the chamfered portion 40 is changed.

Here, the [crack] item is the same item as the [crack] item shown in FIG. Further, the [metal wire cutting failure] item is an item indicating whether or not the Al metal wire W is appropriately cut after the second welding process. In the [metal wire cutting failure] item, the case where the cutting failure of the Al metal wire W does not occur is [○].

As shown in FIG. 11, in Comparative Examples 7 and 8, the Al metal wire W after the first welding process was cracked. Further, in Comparative Example 9, the cutting failure of the Al metal wire W occurred after the second welding process.

On the other hand, in Examples 6 to 10, the Al metal wire W after the first welding process was not cracked, and the cutting failure of the Al metal wire W did not occur after the second welding process.

From this result, the radius of curvature of the chamfered portion 40 is preferably 4.55 μm or more and 20.3 μm or less.

FIG. 12 is a view showing an evaluation result of the [crack] item in a case where the radius of curvature of the chamfered portion 40 is changed. The case where the line arc length of the joint of the first welding (for example, the point on the wire electrode 100) and the joint of the second welding (for example, the point on the pad electrode 200) is 3 mm or more is evaluated. Here, the length of the line arc is the length of the imaginary line connecting the center lines of the two joint portions. In such a package having a long arc length, the tension applied to the Al metal wire W in the in-line arc forming process becomes large, and the crack becomes more likely to occur.

The [crack] item in Fig. 12 is the same item as the [crack] item shown in Figs. 10 and 11 .

As shown in FIG. 12, in Comparative Example 10, cracks occurred in the Al metal wire W after the first welding process. On the other hand, in Examples 11 to 13, the Al metal wires W after the first soldering process did not cause cracks. From this result, the radius of curvature of the chamfered portion 40 is preferably 12.8 μm or more and 20.3 μm or less. According to this, even if the line arc length of the joint of the first welding and the second welding is 3 mm or more, the occurrence of cracks in the Al metal wire W can be suitably suppressed. Further, it is possible to suitably suppress the occurrence of the cutting failure of the bonding wire after the second welding process.

FIG. 13 is a view showing an evaluation result of the [crack] item in a case where the taper angle θ1 (see FIG. 3) of the tapered hole 20 is changed. The angle θ2 of the boundary corner portion 50 of the insertion hole 11 and the tapered hole 20 is defined by the taper angle θ1. When the taper angle θ1 is relatively large, the angle θ2 of the boundary corner portion 50 is relatively small. Therefore, if the taper angle θ1 is too large, for example, a crack is generated in a portion of the Al metal wire W that abuts against the boundary corner portion 50.

In Fig. 13, the [crack] item is an item indicating whether or not a crack is generated in the portion of the Al metal wire W after the first welding process that abuts the boundary corner portion 50. In the [crack] item, the case where no crack is generated is [○].

As shown in FIG. 13, in Comparative Examples 11 and 12, since the taper angle θ1 of the tapered hole 20 was excessively large, cracks occurred in the Al metal wire W after the first welding procedure. On the other hand, in Examples 14 and 15, the Al metal wire W after the first welding process was not cracked. From this result, the taper angle θ1 of the tapered hole 20 is preferably 100 or less. According to this, it is possible to suitably suppress the occurrence of cracks in the Al metal wire W.

The taper angle θ1 of the tapered hole 20 is preferably 0° or more. When the radius of curvature of the chamfered portion 40 is a predetermined value (for example, 4.55 μm or more and 20.3 μm or less, or 12.8 μm or more and 20.3 μm or less), even if the taper angle θ1 of the tapered hole 20 is 0° or close to 0°. In other cases, it is also suppressed that cracks are generated in the portion of the Al metal wire W that abuts against the chamfered portion 40.

At the time of bonding, energy for bonding the Al metal wire W and the wire electrode 100 is generated at the boundary surface of the Al metal wire W and the wire electrode 100 (hereinafter simply referred to as [boundary surface]). The energy distribution affects the joint strength.

FIG. 14 is a perspective view showing a mode of an example of a result of simulation at the time of joining. Fig. 15 is a plan view showing an example of a simulation result of energy distribution at the time of joining. FIG. 16 is a view showing evaluation results of the [joint strength] item in the case where the wire diameter Dw and the outer diameter Dp of the pressing surface are changed. Fig. 14 is a view of the joint portion as seen obliquely from below. In the example shown in Fig. 14, the boundary surface is slightly elliptical. The energy distribution obtained by the simulation in Fig. 14 is displayed on the boundary surface as a contour line.

For example, the energy distribution is changed by changing the ratio Rd (= Dp/Dw) of the pressing surface outer diameter Dp (see FIG. 3) to the wire diameter Dw (see FIGS. 7 and 8). Here, the pressing surface outer diameter Dp is an imaginary circle Cr which is formed by intersecting the extended surface of the outer peripheral portion of the neck portion 14 with the plane of the end portion including the tapered hole 20 as shown in FIG. 3 . diameter.

Fig. 15(a) shows a simulation result in a case where the ratio Rd between the wire diameter Dw and the outer diameter Dp of the pressing surface is less than 6 times. Fig. 15(b) shows a simulation result in a case where the ratio Rd between the wire diameter Dw and the outer diameter Dp of the pressing surface is 6 times or more. 15 (a) and 15 (b) show half of the energy distribution.

The [sewing joint] item of Fig. 16 is an item indicating whether or not sufficient joint strength is obtained in the seam portion S shown in Fig. 8 after the second welding procedure. In the [sewing joint] item, the case where sufficient joint strength is obtained is [○]. The average height Rc of the concavo-convex shape in the pressing surface 30 used in the specimen of the present evaluation is 0.20 μm or more and 0.23 μm or less.

As shown in FIG. 13, in Comparative Examples 13 and 15 in which the ratio Rd was large, a predetermined joint strength could not be obtained. This is because the area of the wire diameter Dw pressing surface 30 is too large, and the amount of energy generated per unit area generated on the boundary surface is small. In this case, the predetermined joint strength cannot be obtained, and the Al metal wire W tends to be peeled off from the wire electrode 100 in the boundary surface.

On the other hand, in Comparative Example 14 in which the ratio Rd was small, a predetermined joint strength could not be obtained. This is because the area of the wire diameter Dw pressing surface 30 is too small, and a sufficient joint area cannot be obtained. On the other hand, in Examples 16 to 19, the ratio Rd was 4.0 times or more and 5.7 times or less. The desired joint strength was obtained in Examples 16 to 19. From the above results, the ratio Rd is preferably 4.0 times or more and 5.7 times or less. According to this, the desired joint strength can be obtained.

(Manufacturing Method) Next, an example of a method of manufacturing the welding pin 1 according to the present embodiment will be described with reference to Fig. 17 . Fig. 17 is a flow chart illustrating a part of a method of manufacturing the welding pin 1. FIG. 17 shows a procedure for forming the chamfered portion 40 and a procedure for forming the concavo-convex shape on the pressing surface 30 and the chamfered portion 40 in the method of manufacturing the welding pin 1.

As shown in Fig. 17, first, by applying a R chamfering process at a boundary portion between the pressing surface 30 and the tapered hole 20, a chamfered portion 40 is formed at the boundary portion (step S101). R chamfering is performed by, for example, brush grinding. The conditions for brush polishing include, for example, polishing pressure and polishing time, and by optimizing these conditions, a chamfered portion 40 having a desired radius of curvature is formed.

Then, by applying sandblasting to the pressing surface 30 and the chamfered portion 40, irregularities are formed on the surfaces of the pressing surface 30 and the chamfered portion 40 (step S102).

Then, by only brushing the chamfered portion 40, the sharpness of the convex portion 41 in the uneven shape of the chamfered portion 40 is smaller than the sharpness of the convex portion 31 in the uneven shape of the pressed surface 30 (step S103) ). As a result, the chamfered portion 40 is provided between the pressing surface 30 and the tapered hole 20, and the welding pin 1 having a fine uneven shape on the surface of the pressing surface 30 and the chamfered portion 40 is manufactured.

Further, the program of the above-described manufacturing method is an example, and the chamfered portion 40 and the uneven shape may be formed by another program. For example, after the blasting process is performed in step S102, both the pressing surface 30 and the chamfering portion 40 may be brush-polished before the brushing of the chamfered portion 40 in step S103. According to this, the surface of the pressing surface 30 and the chamfered portion 40 can be surely formed into a concavo-convex shape in which the area of the distal end portion of the convex portions 31 and 41 is larger than the area of the bottom portion of the concave portions 32 and 42. In other words, the convex portions 31 and 41 are formed. The sharpness is smaller than the sharpness of the concave portions 32 and 42. Further, the brush polishing of the pressing surface 30 and the chamfered portion 40 may be performed after the step S103.

(Modification) Although the above-described embodiment has been described using a so-called bottle neck type welding pin, the welding pin disclosed in the present invention does not necessarily require a neck pin type welding pin. For example, a normal type of welding needle which does not have a neck portion, that is, a tip end portion which is not scraped finely may be used.

Further, in the above-described embodiment, an example in which the concavo-convex shape is formed on the pressing surface and the chamfered portion has been described. However, it is not necessary to form the concavo-convex shape on the pressing surface. Further, a concave-convex shape may be formed in the chamfered portion and the tapered hole.

Further, in the above-described embodiment, the case where the pad electrode of the semiconductor wafer is electrically connected to the lead electrode of the lead frame has been described as an example. However, the soldering pin disclosed in the present invention can also be applied to an object other than the above. The case of bonding the wire.

Further effects or variations can be readily derived by those skilled in the art. Therefore, the broader aspects of the invention are not limited to the specific details and embodiments shown and described. Therefore, various changes may be made without departing from the spirit or scope of the concept of the invention as defined by the appended claims.

1‧‧‧ soldering needle
11‧‧‧ inserted through hole
12‧‧‧Cylinder
13‧‧‧Cone
14‧‧‧ Bottleneck
20‧‧‧Conical hole
30‧‧‧Squeezing surface
31, 41‧‧ ‧ convex
32, 42‧‧‧ recess
40‧‧‧Chamfering
50‧‧‧ top surface
100‧‧‧ wire electrode
200‧‧‧ pads electrode
B‧‧‧Area
Cr‧‧‧ imaginary circle
Dp‧‧‧ pressing surface outer diameter
Dw‧‧‧ Wire diameter θ1‧‧‧ Cone angle of the tapered hole θ2‧‧‧ Angle of the corner of the boundary
S‧‧‧Sewed part
T‧‧‧ tail part
W‧‧‧Al wire

Fig. 1 is a schematic side view showing a welding pin according to the embodiment. Fig. 2 is a schematic enlarged view of the H1 portion shown in Fig. 1. Fig. 3 is a schematic side sectional view showing a tip end portion of a bottleneck portion. Fig. 4 is a schematic enlarged view of the H2 portion shown in Fig. 3. Fig. 5 is a schematic side sectional view showing the surface shape of the pressing surface. Fig. 6 is a schematic side sectional view showing the surface shape of the chamfered portion. Fig. 7 is a schematic side sectional view showing the state of the first welding procedure. Fig. 8 is a schematic side sectional view showing the state of the second welding procedure. Fig. 9 is a graph illustrating a roughness curve of the surface of the chamfered portion. FIG. 10 is a view showing evaluation results of a case where the skewness and the average height of the uneven shape in the chamfered portion and the average height of the uneven shape in the pressed surface are changed. FIG. 11 is a view showing an evaluation result of a case where the radius of curvature of the chamfered portion is changed. FIG. 12 is a view showing an evaluation result of a case where the radius of curvature of the chamfered portion is changed. Fig. 13 is a view showing an evaluation result of a case where the angle of the tapered hole is changed. Fig. 14 is a perspective view showing a mode of an example of a result of a simulation of bonding. 15(a) and 15(b) are plan views showing an example of a result of a simulation of joining. Fig. 16 is a view showing an evaluation result of a case where the ratio of the outer diameter of the pressing surface to the wire diameter is changed. Fig. 17 is a flow chart illustrating a part of a method of manufacturing a welding pin.

1‧‧‧ soldering needle

11‧‧‧ inserted through hole

20‧‧‧Conical hole

30‧‧‧Squeezing surface

40‧‧‧Chamfering

100‧‧‧ wire electrode

B‧‧‧Area

Dw‧‧‧ wire diameter

W‧‧‧Al wire

Claims (12)

A welding pin, comprising: a pressing surface of a tight bonding wire; an insertion hole through which the bonding wire is inserted; and a tapered hole extending to the pressing surface and connecting the insertion hole and the pressing surface And a chamfered portion disposed between the tapered hole and the pressing surface, the chamfered portion having a concave-convex shape on the surface, and the sharpness of the convex portion in the concave-convex shape is sharper than the concave portion in the concave-convex shape Small. In the welding pin according to the first aspect of the invention, the uneven shape of the chamfered portion has a skewness of -0.164 or less and an average height of 0.035 μm or more and 0.092 μm or less. The welding pin of claim 1 or 2, wherein the pressing surface has a concave-convex shape, and a sharpness of the convex portion in the concave-convex shape of the pressing surface is convex than a convex shape in the concave-convex shape of the chamfered portion The sharpness of the ministry is large. The welding pin of claim 3, wherein the uneven shape in the pressing surface has an average height of 0.113 μm or more. The welding pin of claim 1 or 2, wherein the chamfered portion has a curved surface that is smoothly continuous to the tapered hole and the pressing surface, and the radius of curvature of the curved surface is 4.55 μm or more and 20.30 μm or less. . The welding pin of claim 1 or 2, wherein the chamfered portion has a curved surface that is smoothly continuous with the tapered hole and the pressing surface, and the radius of curvature of the curved surface is 12.8 μm or more and 20.30 μm or less. . The welding pin of claim 1 or 2, wherein the tapered hole has a taper angle of 100 or less. The welding pin of claim 1 or 2, wherein the outer diameter of the pressing surface is 4.0 times or more and 5.7 times or less of the wire diameter of the bonding wire. The welding pin of claim 1 or 2, wherein the pressing surface has a concave-convex shape, and a sharpness of the convex portion in the concave-convex shape of the pressing surface is convex than a convex shape in the concave-convex shape of the chamfered portion The sharpness of the portion is large, and the uneven shape in the pressing surface has an average height of 0.113 μm or more, and the chamfered portion has a curved surface smoothly continuous to the tapered hole and the pressing surface, and the radius of curvature of the curved surface is 4.55 μm or more and 20.30 μm or less. The welding pin of claim 1 or 2, wherein the pressing surface has a concave-convex shape, and a sharpness of the convex portion in the concave-convex shape of the pressing surface is convex than a convex shape in the concave-convex shape of the chamfered portion The sharpness of the portion is large, and the uneven shape in the pressing surface has an average height of 0.113 μm or more, and the chamfered portion has a curved surface smoothly continuous to the tapered hole and the pressing surface, and the radius of curvature of the curved surface is 12.8 μm or more and 20.30 μm or less. The welding pin according to claim 9 wherein the taper angle of the tapered hole is 100° or less, and the outer diameter of the pressing surface is 4.0 times or more and 5.7 times or less of the wire diameter of the wire. The welding pin of claim 10, wherein the tapered hole has a taper angle of 100 or less, and an outer diameter of the pressing surface is 4.0 times or more and 5.7 times or less of a wire diameter of the wire.