TW201701982A - Bonding capillary - Google Patents

Abstract

Provided is a bonding capillary which is characterized in that: the bonding capillary is provided with a body comprising a through-hole into which a wire is inserted, a first pressing face which presses on the wire and has a first sloping face provided in the periphery of the through-hole and inclining along the extending direction of the through-hole, and a second pressing face which presses on the wire and has a tapered face provided between the first sloping face and the through-hole and a second sloping face provided between the tapered face and the first sloping face; and the root-mean-square gradient of the roughness curve element on the second sloping face is smaller than the root-mean-square gradient of the roughness curve element on the first sloping face.

Description

Solder pin

Aspects of the invention are generally related to bonding capillary.

Wire bonding of a semiconductor element and a lead frame is performed by a bonding wire (hereinafter referred to as [wire]) in the process of the semiconductor device. Using a soldering pin to bond one end of a metal wire to an electrode pad of a semiconductor element in wire bonding (e l e c t r o d e p a d ) (first bond)). Second, the pull metal wire is bonded to a lead (second bond). When the metal wire is joined, ultrasonic waves are applied in a state where the metal wire is pressed by the welding pin.

For example, in the second welding, a main joint portion (stitch bond) of the metal wire and the wire, and a temporary joint portion (tail bond) of the wire and the wire are formed. After this second welding, the wire extending by the tail wire joint is cut. The semiconductor device is then fabricated by sealing a semiconductor element connected to the metal wire with a lead frame with a sealing resin.

In recent years, semiconductor devices have been used in, for example, in-vehicle electronic devices, and are used in a harsh temperature cycle environment. In the case where the semiconductor device is used in a severe temperature cycle environment, the problem of peeling or cracking of the sealing resin tends to occur due to a thermal expansion difference between the sealing resin and the metal. Therefore, high environmental reliability (temperature cycle reliability) is required in the semiconductor device manufactured as described above.

Moreover, in recent years, attempts have been made to use copper which is lower in cost than gold as a material of a metal wire. From the viewpoint of the adhesion between the metal and the sealing resin, the material of the sealing resin is also changed when the material of the metal wire is changed. However, in the case where copper is used for the metal wire, further improvement is required in order to meet the demand for high environmental reliability.

In contrast, a method of using a lead frame called a roughened lead frame is proposed, for example. A thick plating layer containing nickel or the like is formed on the surface of the roughened lead frame, and the surface of the plating layer is subjected to a roughening treatment. The adhesion of the lead frame to the sealing resin can be improved by surface roughness.

However, if such a roughened lead frame is used, the metal wire containing hard copper is pressed against the thick plating layer at the time of the second welding. At this time, the metal wire sinks into the thick plating layer, and the bondability between the metal wire and the wire tends to decrease. Moreover, the cuttability of the metal wire deteriorates after the second welding. When the cuttability of the metal wire is deteriorated, there is a problem that the joint portion is peeled off (peeling failure) when the wire is cut. Further, since the welding pin is pressed against the plating layer having a rough surface, the welding pin is easily worn, and the life of the welding pin tends to deteriorate.

[Patent Document 1] Japanese Patent Publication No. 2009-540624 [Patent Document 2] Japanese Patent Laid-Open No. 2-136951

The present invention has been made in view of such a problem, and an object of the invention is to provide a welding pin which can improve the joint strength, improve the cutting property of a metal wire, and suppress abrasion.

A first invention is a soldering pin, comprising: a body portion including: an insertion hole through which a metal wire is inserted; and pressing the metal wire, and extending around the insertion hole and having the insertion hole a first pressing surface of the first inclined surface that is inclined in the axial direction; the metal wire is pressed, and has a tapered surface provided between the first inclined surface and the insertion hole, and is disposed on the tapered surface a second pressing surface of the second inclined surface between the first inclined surface, and a root mean square slope of the second inclined surface is larger than the first The root mean square slope of the roughness curve element of the inclined surface is small.

According to the welding pin, the metal wire can be pressed on the rough first inclined surface at the time of main joining, and the joint strength of the stitch joint portion can be ensured. Further, since the metal wire is pressed by the second inclined surface and the tapered surface during the temporary bonding, the contact area between the welding pin and the metal wire is increased, and the bonding strength of the tail wire bonding portion can be improved. Further, when the metal wire is cut after joining, a large tensile force is generated in the metal wire by the first inclined surface having a large root mean square slope. On the other hand, it is difficult to generate a pulling force on the metal wire by the second inclined surface having a small root mean square slope. By this action, the stress is maximized in a position where the metal wire located near the boundary between the first inclined surface and the second inclined surface is cut (for example, the thinnest portion of the metal wire). Therefore, the occurrence of micro cracks is promoted, and the deformation form of the micro cracks becomes the mode I (opening mode), and the crack progresses. According to this, the cutting property of the metal wire can be improved. Further, in the second inclined surface having the root mean square slope smaller than the first inclined surface, the stress generated when the metal wire is pressed is dispersed, and the wear of the welding pin can be suppressed.

According to a second aspect of the invention, in the first aspect of the invention, the root mean square slope of the roughness curve element of the first inclined surface is 8゚ or more, and the roughness curve elements of the second inclined surface are both The square root slope is 5 ゚ or less.

According to the welding pin, the root mean square slope of the first inclined surface is 8 ゚ or more, and when the wire is cut, the tensile force generated on the wire by the first inclined surface can be increased. Further, the root mean square slope of the second inclined surface is 5 ゚ or less, and when the wire is cut, the tensile force generated on the wire by the second inclined surface can be reduced. Therefore, the deformation form of the micro crack generated at the appropriate position where the wire is cut is the mode I (opening mode), and the crack progresses. According to this, the cutting property of the metal wire can be improved.

According to a third aspect of the invention, in the first or second aspect of the invention, the root mean square slope of the roughness curve element of the first inclined surface is 11 ゚ or more, and the roughness of the second inclined surface The root mean square slope of the curve element is 2゚ or less.

According to the welding pin, the root mean square slope of the first inclined surface is 11 ゚ or more, and the root mean square slope of the second inclined surface is 2 ゚ or less, and even if the welding pin is worn, the mean square of the first inclined surface is easily obtained. The difference between the root slope and the root mean square slope of the second inclined surface is maintained at a certain level or more. Therefore, it is possible to suppress a decrease in the tensile force generated on the wire by the first inclined surface and the difference in the tensile force generated on the wire by the second inclined surface. As a result, even if the welding pin is worn, the deformation form of the micro crack generated at the appropriate position where the wire is cut is the mode I, and the crack progresses. Therefore, the cutting property of the metal wire can be improved.

According to a fourth aspect of the invention, in the first aspect to the third aspect, the width of the second inclined surface is an outer diameter of the first pressing surface when viewed along the axial direction. 2% or more and 8% or less.

According to the welding pin, when the width of the second inclined surface is 2% or more of the outer diameter of the first pressing surface when viewed in the axial direction, the critical stress of the raw material abrasion of the welding pin can be lowered. The maximum stress generated at the tip of the solder pin. According to this, the wear of the welding pin can be greatly suppressed. Further, when the width of the second inclined surface when viewed in the axial direction is 8% or less of the outer diameter of the first pressing surface, a stress capable of obtaining a sufficient joint strength of the tail wire joint portion can be generated.

A fifth invention is characterized in that in any one of the first to fourth inventions, the first inclined surface has a maximum height Rz of 0.2 μm or more, and the second inclined surface has a maximum height Rz of 0.16 μm. the following.

According to the welding pin, since the maximum height Rz of the first inclined surface is 0.2 μm or more, the metal wire can be pressed on the first inclined surface, so that sufficient joint strength can be obtained. Further, the sliding of the metal wire and the welding pin is promoted by the maximum height Rz of the second inclined surface being 0.16 μm or less. According to this, the cutting property of the metal wire can be improved. The occurrence of poor peeling can be suppressed by the above.

According to a sixth aspect of the invention, in the first aspect of the invention, the first inclined surface has a maximum height Rz of 0.3 μm or more, and the second inclined surface has a maximum height Rz of 0.10 μm. the following.

According to the welding pin, since the maximum height Rz of the first inclined surface is 0.3 μm or more, even if the welding pin is worn, it is easy to maintain the maximum height Rz of the first inclined surface constant or more. According to this, even if the welding pin is worn, the metal wire can be pressed on the first inclined surface, so that sufficient joint strength can be obtained. Further, even if the welding pin is worn, the sliding of the metal wire and the welding needle can be promoted by the maximum height Rz of the second inclined surface being 0.10 μm or less. According to this, the cutting property of the metal wire can be improved.

According to a seventh aspect of the invention, in the first aspect of the invention, the axially perpendicular surface and the second inclined surface are formed at an angle larger than the axially perpendicular surface The angle formed by the first inclined surface is small.

According to this welding pin, since the metal wire is pressed by the second inclined surface at the time of temporary joining, the joint strength of the tail wire joining portion can be improved.

According to a seventh aspect of the invention, in the first aspect of the invention, the angle between the axially perpendicular surface and the second inclined surface is 11 degrees or less.

According to the welding pin, since the angle between the surface perpendicular to the axial direction and the second inclined surface is 11 degrees or less, the stress of the joint strength of the tail joint portion at the time of temporary joining can be obtained (the second pressing surface) The force of pressing the wire) is generated.

According to a ninth aspect of the invention, in the first aspect of the invention, the boundary between the first inclined surface and the second inclined surface is a saw shape when viewed along the axial direction.

According to the welding pin, the sawing shape of the boundary between the first inclined surface and the second inclined surface causes a repeated stress on the wire during the joining operation. According to this, it is easy to cause micro cracks in the metal wire. Therefore, the cutting property of the metal wire can be improved, and the occurrence of peeling failure can be suppressed.

According to a tenth aspect of the invention, in the first aspect of the invention, the first inclined surface has a skewness of -0.3 or less, and an average height of the first inclined surface is 0.06 μm or more and 0.3 μm or less.

According to the welding pin, the shape change accompanying wear during use can be reduced. Even if the joining is repeated, the initial wire cutting property and the joint strength can be maintained for a long period of time.

According to a eleventh aspect of the invention, in the first aspect of the invention, the kurtosis of the second inclined surface is 5.0 or less.

According to the welding pin, the slanting of the second inclined surface is 5.0 or less, so that the sliding of the metal wire and the welding pin is promoted, and the cutting property of the metal wire can be improved.

Hereinafter, the form of the embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and detailed descriptions thereof will be omitted.

(Embodiment) FIG. 1 is a schematic view illustrating a welding pin according to this embodiment. Fig. 2 is a schematic enlarged view showing a shape of a tip end of a welding pin according to the embodiment. The entirety of the welding pin 110 is shown in FIG. Fig. 2 shows an enlarged view of the area A shown in Fig. 1.

As shown in FIG. 1, the welding pin 110 has a body portion 10. The body portion 10 is a tubular member and has an insertion hole 20 . The insertion hole 20 is a through hole that extends in the axial direction Da of the body portion 10. The metal wire is inserted into the insertion hole 20 during use of the welding pin.

The main body portion 10 is provided with a cylindrical portion 11 , a conical portion 12 disposed on the distal end side of the cylindrical portion 11 , and a neck portion 13 disposed on the distal end side of the conical portion 12 . The insertion hole 20 is provided to penetrate the cylindrical portion 11, the conical portion 12, and the neck portion 13.

Further, in the present specification, the distal end side or the distal end direction means a direction from the end portion on the side of the cylindrical portion 11 toward the end portion on the side of the neck portion 13. The tip end of the welding pin (body portion) means the end portion on the side of the neck portion 13.

The cylindrical portion 11 has a diameter for mechanically fixing the welding pin 110 to the bonding device.

The diameter of the conical portion 12 becomes smaller toward the distal end side. The conical portion 12 has, for example, a truncated cone shape. The diameter of the end portion on the side of the cylindrical portion 11 of the conical portion 12 is substantially equal to the diameter of the cylindrical portion 11.

The diameter of the neck portion 13 is smaller than the diameter of the conical portion 12. For example, the diameter of the neck portion 13 gradually becomes smaller toward the tip end direction. Since the diameter of the neck portion 13 is small, the adjacent metal wires that have been wired can be avoided and the wire bonding can be performed at a predetermined position.

Further, the welding pin 110 is formed of, for example, ceramic. As a material of the welding pin 110, for example, alumina or the like can be used. Alternatively, a composite material containing alumina, at least one of zirconia and chromia, or the like may be used as the material of the welding pin 110.

Fig. 3 is a schematic enlarged view showing a distal end of a welding pin according to the embodiment. Fig. 3 is a perspective view showing the tip end of the welding pin shown in Fig. 2 as seen obliquely from below. As shown in FIG. 3, the main body portion 10 has a first pressing surface 51 and a second pressing surface 52 which are disposed at ends in the axial direction.

The first pressing surface 51 is provided around the insertion hole 20 in the top end of the body portion 10. The first pressing surface 51 is a part of the surface of the neck portion 13, and is, for example, a curved surface.

The second pressing surface 52 is disposed between the insertion hole 20 and the first pressing surface 51. The second pressing surface 52 is a part of the surface of the neck portion 13 and is a surface continuous with the first pressing surface 51.

As will be described later, the first pressing surface 51 and the second pressing surface 52 are surfaces for pressing the wire to the lead frame during wire bonding. For example, the first pressing surface 51 is a pressing surface forming a main joint, and the second pressing surface 52 is a pressing surface forming a temporary joint.

The details of the shapes of the first pressing surface 51 and the second pressing surface 52 will be further described. 4(a), 4(b) and 5 are schematic cross-sectional views illustrating a tip end of a welding pin according to the embodiment. Fig. 4(a) is a cross section showing the line A1-A2 shown in Fig. 3. That is, FIG. 4(a) is a cross section showing a plane parallel to the axial direction Da. Fig. 4(b) is a cross-sectional view showing an enlarged view of a region B shown in Fig. 4(a).

As shown in FIG. 4(b), the insertion hole 20 has a tapered hole 21 and a straight hole 22. The tapered hole 21 is provided on the distal end side of the straight hole 22, and is connected to the straight hole 22. The diameter of the tapered hole 21 becomes larger as it goes toward the tip end side.

The first pressing surface 51 has a first inclined surface 51s provided around the insertion hole 20. The first inclined surface 51s is inclined with respect to the axial direction Da and the radial direction (the direction perpendicular to the axial direction Da). Moreover, the diameter of the first inclined surface 51s becomes smaller toward the distal end side of the body portion 10. That is, the distance between the central axis 20a of the insertion hole 20 and the first inclined surface 51s becomes shorter along the distal end direction. In this example, the cross-sectional shape of the first inclined surface 51s in Fig. 4(b) includes a curved portion, but may be linear, and may be constituted by a straight line and a curved line.

The second pressing surface 52 has a tapered surface 52t and a second inclined surface 52f. The tapered surface 52t is provided around the insertion hole 20 between the first inclined surface 51s and the insertion hole 20. The tapered surface 52t is a portion facing the tapered hole 21 in the second pressing surface 52. The tapered surface 52t has a tapered shape that expands toward the top end. That is, the distance between the central axis 20a of the insertion hole 20 and the tapered surface 52t becomes longer along the tip end direction.

The second inclined surface 52f is provided between the tapered surface 52t and the first inclined surface 51s. The second inclined surface 52f is a surface continuous with the tapered surface 52t and the first inclined surface 51s, and is located at the most distal end side of the neck portion 13. In this example, the second inclined surface 52f extends along a plane perpendicular to the axial direction Da (that is, θ1 = 0 后 which will be described later). However, the second inclined surface 52f may be slightly inclined by a plane perpendicular to the axial direction Da (θ1>0).

In the present embodiment, the surface of the first pressing surface 51 is formed to be rougher than the surface of the second pressing surface 52. That is, the second inclined surface 52f and the tapered surface 52t are smoother than the first inclined surface 51s. The uneven shape of the surface of the second inclined surface 52f is smaller than the uneven shape of the surface of the first inclined surface 51s, and the uneven shape of the surface of the tapered surface 52t is smaller than the uneven shape of the surface of the first inclined surface 51s. Specifically, the root mean square slope (RΔq) of the roughness curve element of the second inclined surface 52f is smaller than the root mean square slope (RΔq) of the roughness curve element of the first inclined surface 51s. Further, for example, the root mean square slope (RΔq) of the roughness curve element of the tapered surface 52t is smaller than the root mean square slope (RΔq) of the roughness curve element of the first inclined surface 51s. The root mean square slope (RΔq) of the roughness curve element indicates the uneven shape of the surface, and is a parameter corresponding to the magnitude of the inclination of the unevenness.

Fig. 5 is a cross section illustrating an enlarged view of Fig. 4(b). In the example shown in FIG. 5, the diameter of the second inclined surface 52f becomes smaller toward the distal end side of the body portion 10. That is, the distance between the central axis 20a of the insertion hole 20 and the second inclined surface 52f becomes shorter along the distal end direction. For example, the intersection (intersection line) of the tapered surface 52t and the second inclined surface 52f is located at the top end of the body portion 10.

As shown in FIG. 5, the angle θ1 is smaller than the angle θ2. Here, the angle θ1 is an angle formed by the surface P1 perpendicular to the axial direction Da and the second inclined surface 52f. The angle θ2 is an angle formed by the plane P1 perpendicular to the axial direction Da and the first inclined surface 51s. It is preferable that the angle θ1 is 0 degrees or more and 11 degrees or less. The angle θ2 is preferably 2 degrees or more and 45 degrees or less, for example.

Next, the bonding using the solder pins (second bonding) will be described. Fig. 6 is a schematic cross-sectional view showing a state in which wire bonding is performed. The metal wire BW inserted through the insertion hole 20 of the solder pin 110 is first bonded to an electrode or the like of a semiconductor element (not shown). Then, the soldering pin 110 is pulled onto the wire 200 in a prescribed track and a loop is formed in the wire BW. Next, a second bonding of bonding the metal wires BW to the wires 200 is performed. A state in which the wire 200 of the lead frame is joined to the second wire of the wire BW is shown in FIG.

The lead frame used in the present embodiment is, for example, a roughened lead frame. That is, a thick Ni plating layer or the like which is subjected to roughening treatment is disposed on the surface of the wire 200. The thickness of the plating layer is, for example, about 20 μm. Moreover, for example, copper is used as the material of the metal wire BW.

In the second bond, the solder pin 110 is pressed over the wire 200. According to this, the metal wire BW is sandwiched between the first pressing surface 51 (first inclined surface 51s) and the wire 200. Further, the metal wire BW is sandwiched between the second pressing surface 52 and the wire 200.

Since the first inclined surface 51s is inclined toward the second inclined surface 52f, the interval between the first inclined surface 51s and the wire 200 is narrowed in the direction toward the inner side of the welding pin 110. Therefore, the thickness of the metal wire BW sandwiched between the first inclined surface 51s and the wire 200 is thinned in the direction toward the inner side of the welding pin 110.

Moreover, the thickness of the metal wire BW is the thinnest between the second inclined surface 52f and the wire 200. Since the tapered surface 52t has a tapered shape, the interval between the tapered surface 52t and the wire 200 is widened in the direction toward the inner side of the welding pin 110. Therefore, the thickness of the metal wire BW sandwiched between the tapered surface 52t and the wire 200 becomes thicker toward the inner side of the welding pin 110.

In this manner, for example, ultrasonic waves are applied to the welding pin 110 while the metal wire BW is interposed between the welding pin 110 and the wire 200. Accordingly, the wire BW is crimped to the wire 200. A main joint portion (pin type joint portion SB) is formed between the first pressing surface 51 (first inclined surface 51s) and the wire 200, and the second pressing surface 52 (second inclined surface 52f and tapered surface 52t) is formed. A temporary joint portion (tail line joint portion TB) is formed between the wire 200 and the wire 200.

After the metal wire BW is crimped, the solder wire 110 is raised in a state where the metal wire BW is clamped by the solder pin 110. According to this, the metal wire BW is cut by the tail wire joint portion TB. For example, since the intersection (intersection line) of the second inclined surface 52f and the tapered surface 52t is formed relatively sharply, the metal wire BW is cut at the portion pressed against the intersection.

7(a) and 7(b) are photographic images illustrating the bonding wires and the wires 200. In FIGS. 7(a) and 7(b), the joint portion after the second joining is enlarged and displayed.

As shown in Fig. 7(a), after the second bonding of the welding pin 110 according to the present embodiment is used, the wire BW is joined to the wire 200 and is cut by the tail wire bonding portion TB.

In this second bonding, in the case where the roughened lead frame is used, the metal wire easily sinks into the wire when the soldering pin is pressed against the wire. Therefore, the joint strength is deteriorated, and the cuttability of the metal wire tends to deteriorate.

Fig. 7(b) is a view illustrating a defect occurring in the case where the cuttability of the metal wire is deteriorated. When the cutting property of the metal wire is deteriorated, as in the region C shown in Fig. 7(b), when the metal wire is cut, a part of the joint portion (for example, the tail wire joint portion TB) is peeled off, which is often called Peeling or poor fish tail.

On the other hand, in the welding pin 110 according to the present embodiment, the first inclined surface 51s having a rough surface state is provided at the tip end of the welding pin 110. Therefore, the wire BW can be pressed against the wire 200 efficiently by the first inclined surface 51s. Therefore, the joint strength of the stitch joint portion SB can be ensured.

Further, in the welding pin 110 according to the present embodiment, a smooth second inclined surface 52f and a tapered surface 52t are provided at the distal end of the welding pin 110. The wire BW is pressed against the wire 200 by the second inclined surface 52f and the tapered surface 52t. Therefore, the contact area of the welding pin 110 and the wire BW is increased as compared with the case where the second inclined surface 52f is not provided, and the joint strength of the tail wire joint portion TB can be improved.

Further, when the metal wire is cut after the joining, the metal wire BW is pressed by the rough first inclined surface 51s, and the sliding of the metal wire BW and the welding pin 110 is promoted by the smooth second inclined surface 52f. According to this, the cutting property of the metal wire can be improved.

Figs. 8(a) and 8(b) are schematic views for explaining the cutting of the metal wire by the welding pin according to the embodiment. Fig. 8(a) is a conceptual view for explaining the action of the welding pin when the wire is cut. Fig. 8(a) shows an enlarged cross section of a region where the welding pin 110 is in contact with the wire BW in the vicinity of the boundary between the first inclined surface 51s and the second inclined surface 52f. This area corresponds to the appropriate position where the metal wire of the metal wire BW is cut, that is, the thinnest portion of the metal wire BW.

The left side of the welding pin 110 in the drawing corresponds to the first inclined surface 51s having a large RΔq (root mean square slope), and the right side corresponds to the second inclined surface 52f having a small RΔq. The appearance of the large RΔq indicating the uneven shape on the unevenness of the unevenness on the surface of the metal wire is displayed. That is, for example, the angle θ3 shown in FIG. 8(a) is larger than the angle θ4.

When the wire BW is cut, ultrasonic waves are applied in a state where the welding pin 110 contacts the wire BW as shown in Fig. 8(a). Accordingly, a force is applied to the welding pin 110. For example, a horizontal force (vector F1) is applied to the first inclined surface 51s, and a horizontal force (vector F2) is applied to the second inclined surface 52f. Here, for convenience of explanation, the size and direction of the vector F1 are considered to be the same as the size and direction of the vector F2.

For example, the vector F2 can be decomposed into a vector F21 and a vector F22. The vector F21 is a vector along the direction of the surface of the second inclined surface 52f. The vector F22 is a vector that is perpendicular to the direction of the vector F21. Here, the vector F21 is larger as RΔq is smaller. That is to say, if RΔq is small, the component which is upward as the vector F21 becomes larger. Therefore, the force transmitted from the surface of the welding pin 110 to the wire BW becomes small. Therefore, the tensile force FT2 generated in the metal wire BW by the second inclined surface 52f having a small RΔq is relatively small.

Similarly, the vector F1 can be decomposed into a vector F11 and a vector F12. The vector F11 is a vector along the direction of the surface of the first inclined surface 51s. The vector F12 is a vector that is perpendicular to the direction of the vector F12. Since RΔq is large in the first inclined surface 51s, the component which is upward in the direction of the vector F11 is small. Therefore, the tensile force FT1 generated in the metal wire BW is large by the first inclined surface 51s having a large RΔq.

In the welding pin 110 according to the present embodiment, the first inclined surface 51s having a large RΔq and the second inclined surface 52f having a small RΔq are disposed in the adjacent direction. Therefore, a large stress is generated by the difference between the tensile force FT1 and the tensile force FT2 in a position where the metal wire near the boundary between the first inclined surface 51s and the second inclined surface 52f is cut. Therefore, as shown in FIG. 8(a), the occurrence of minute cracks in the vicinity of the boundary between the first inclined surface 51s and the second inclined surface 52f is promoted. Further, in the microcracks that have occurred, the deformation form of the microcracks becomes the mode I (opening mode) of Fig. 8(b). As a result, as the region D of FIG. 8(a) progresses, the cutting property of the metal wire can be improved. As a result, it is possible to suppress the occurrence of defects such as peeling.

Further, since the surface of the roughened lead frame is rough, the tip end of the welding pin is easily worn by pressing the welding pin. On the other hand, the second inclined surface 52f is disposed to be slightly parallel to the surface of the lead wire 200. Further, since RΔq of the second inclined surface 52f is small, as shown in FIG. 8(a), the tip end angle θ5 of the convex portion of the second inclined surface 52f is large. For example, the tip angle θ5 is larger than the tip end angle θ6 of the convex portion of the first inclined surface 51s. Therefore, concentration of stress in the tip end of the welding pin 110 can be suppressed, and abrasion of the welding pin can be suppressed.

Hereinafter, an embodiment of the welding pin 110 according to the present embodiment will be described with reference to the evaluation result of the welding pin.

Further, in the present specification, the uneven shape (RΔq, Rz, Rc, Rsk, Rp, Rku, etc.) of the surface of the welding pin is calculated in accordance with JIS B 0601-2001. Further, the roughness curve was measured under the following conditions in each evaluation. The uneven shape was calculated from the measurement result of the roughness curve. Measuring apparatus: laser microscope (manufactured by OLYMPUS, OLS4000) Measurement magnification: 50 times Evaluation length: 125 μm to 400 μm Cutoff (phase compensation type high-pass filter) λc: 25 μm FIG. 9 is an illustration of a solder pin A diagram of the results of the evaluation. FIG. 9 is a view showing an example in which the root mean square slope RΔq(゚) of the roughness curve element of the first inclined surface 51s and the root mean square slope RΔq(゚) of the roughness curve element of the second inclined surface 52f are different (comparison The evaluation results of Examples 1 to 4 and Examples 1 to 8). In the present evaluation, RΔq of the first inclined surface 51s is 5.4 ゚ to 12.4 ゚. Further, the RΔq of the second inclined surface 52f is 1.8 ゚ to 13.4 ゚. Further, RΔq of the tapered surface 52t is made the same as RΔq of the second inclined surface 52f.

Further, the root mean square slope RΔq of the roughness curve element can be calculated by the following formula (1). l is the reference length, and Z(x) is the value of the height in the roughness curve. Formula 1) Fig. 9 is a view showing the evaluation results of the frequency of occurrence of peeling failure. Here, the item of [exfoliation occurrence frequency] is the frequency of occurrence of peeling after the second joining. Regarding each of Comparative Examples 1 to 4 and Examples 1 to 8 shown in Fig. 9, the number of samples was 32 or 128. [×] means that peeling occurred in 32 samples. That is to say, [x] means that the frequency of occurrence of spalling is 1/32 or more. [○] means that no peeling occurred in 32 samples, but peeling occurred when the number of samples increased. [○] means that the frequency of occurrence of peeling is 1/127 or more and less than 1/32. [◎] means that no peeling occurred in 128 samples. That is to say, [◎] means that the frequency of spalling is less than 1/128.

As in Comparative Examples 1 to 3, it is found that peeling easily occurs when both the RΔq of the first inclined surface 51s and the RΔq of the second inclined surface 52f are both large or small.

On the other hand, in the first to eighth embodiments, when RΔq of the first inclined surface 51s is 8゚ or more and RΔq of the second inclined surface 52f is 5゚ or less, the frequency of occurrence of peeling is low. Further, as in the seventh and eighth embodiments, when RΔq of the first inclined surface 51s is 11 ゚ or more and RΔq of the second inclined surface 52f is 2 ゚ or less, the occurrence of peeling can be further suppressed. This point is as described with reference to FIGS. 8(a) and 8(b), and it is considered that the tensile force generated by the first inclined surface 51s is large and the tensile force generated by the second inclined surface 52f is small. The occurrence of minute cracks is promoted at an appropriate position where the wire is cut, and the deformation form of the micro crack is the mode I (opening mode), and the crack progresses. According to this, the cutting property of the metal wire can be improved.

Further, when RΔq of the first inclined surface 51s is 11 ゚ or more and RΔq of the second inclined surface 52f is 2 ゚ or less, even if the welding pin is worn, it is easy to set the RΔq of the first inclined surface 51s and the second inclined surface 52f. The difference in RΔq is kept constant or more. Therefore, the stress generated by the wire BW due to the difference in tensile force can be maintained.

Fig. 10 is a view exemplifying the evaluation results of the welding pins. FIG. 10 is a view showing an evaluation result of a case where the width W1 of the second inclined surface 52f is changed to the tip end diameter T of the welding pin 110.

Here, the width W1 of the second inclined surface 52f means the width of the second inclined surface 52f when the welding needle 110 is viewed in the axial direction. The shape of the second inclined surface 52f is an annular shape having an outer diameter D1 and an inner diameter D2 when viewed in the axial direction (see FIGS. 4(a) and 4(b)). At this time, the width W1 is 1/2 times the difference between the outer diameter D1 and the inner diameter D2. Further, it is also possible to use the average value in the circumferential direction as the outer diameter D1 in the case where the outer diameter changes in the circumferential direction. It is also possible to use the average value in the circumferential direction as the inner diameter D2 in the case where the inner diameter changes along the circumferential direction.

The tip end diameter T of the welding pin 110 is an outer diameter of the first inclined surface 51s (the first pressing surface 51) that is annular when viewed in the axial direction. Specifically, the outer diameter of the first inclined surface 51s is the diameter of the virtual circle Cr generated by the extension surface of the outer circumferential surface of the neck portion 13 and the plane including the second inclined surface 52f (see FIGS. 4(a) and 4( b)).

Fig. 10 is a graph showing the results of evaluation of the frequency of occurrence of peeling failure. Here, the item of [exfoliation occurrence frequency] is the frequency of occurrence of peeling after the second joining. In the evaluation, regarding the ratio of the width W1 to the tip diameter T shown in FIG. 10, the number of samples was 32. [○] means that no peeling occurred. That is to say, [○] means that the incidence of peeling is less than 1/32. [×] means that spalling has occurred. That is to say, [x] means that the incidence of peeling is 1/32 or more. Further, a metal wire having a diameter of 25 μm was used in the evaluation. Further, the tip end diameter T of the welding pin 110 is 75 μm.

As is apparent from the evaluation results shown in FIG. 10, peeling does not occur when the ratio of the width W1 to the tip diameter T is 2% or more and 8% or less. In other words, the width W1 of the second inclined surface 52f is preferably 2% or more and 8% or less of the tip diameter T. When the ratio of the width W1 to the tip diameter T is larger than 8%, it becomes difficult to generate sufficient stress at the tip end of the welding pin 110, and the joint strength is lowered. On the other hand, when the ratio of the width W1 to the tip end diameter T is less than 2%, the stress generated at the tip end of the welding pin 110 is increased, and the tip end of the welding pin 110 is easily worn. In the embodiment, by the ratio of the width W1 to the tip end diameter T of 2% or more and 8% or less, abrasion of the welding pin 110 can be suppressed, and sufficient joint strength can be obtained.

Fig. 11 is a view exemplifying the evaluation results of the welding pins. FIG. 11 is an evaluation result showing an example in which the combination of the maximum height Rz of the first inclined surface 51s and the maximum height Rz of the second inclined surface 52f is different (Comparative Examples 5 to 9 and Examples 9 to 14). Further, the maximum height Rz of the tapered surface 52t and the maximum height Rz of the second inclined surface 52f are regarded as the same. The maximum height Rz is the sum of the maximum value of the mountain height in the reference length and the maximum value of the valley depth.

Fig. 11 is a result of evaluation showing the frequency of occurrence of peeling failure. The item of [exfoliation occurrence frequency] is the frequency of occurrence of peeling after the second joining as in the description of Fig. 9 . That is, in each case (each condition), [◎] means that no peeling occurred in 128 samples, [○] means that no peeling occurred in 32 samples, and [x] means that peeling occurred in 32 samples. .

As a result of the evaluation shown in FIG. 11, when the maximum height Rz in the first inclined surface 51s is 0.2 μm or more and the maximum height Rz in the second inclined surface 52f is 0.16 μm or less, the peeling occurrence frequency is [○]. . Further, in the first and fourth embodiments, when the maximum height Rz of the first inclined surface 51s is 0.3 μm or more and the maximum height Rz of the second inclined surface 52f is 0.10 μm or less, the peeling occurrence frequency becomes [◎].

Since the maximum height Rz of the first inclined surface 51s is 0.2 μm or more, the metal wire BW can be suppressed on the first inclined surface 51s, so that sufficient joint strength can be obtained. Further, the maximum height Rz of the second inclined surface 52f and the maximum height Rz of the tapered surface 52t are each 0.16 μm or less, so that the sliding of the metal wire BW and the welding pin is promoted. According to this, the cutting property of the metal wire BW can be improved. By the above, the occurrence of peeling failure can be suppressed. Further, when the maximum height Rz of the first inclined surface 51s is 0.3 μm or more and the maximum height Rz of the second inclined surface 52f is 0.10 μm or less, the maximum height Rz can be kept constant or more even if the welding pin is worn. According to this, the cutting property of the metal wire can be improved as described above.

Fig. 12 is a view exemplifying the evaluation results of the welding pins. FIG. 12 is a view showing an evaluation result of a case where the angle θ1 (see FIG. 5) of the second inclined surface 52f is changed. In the present evaluation, the angle θ1 is 0.5 degrees or more and 17 degrees or less. Further, the angle θ2 of the first inclined surface 51s is 20 degrees, and the width W1 of the second inclined surface 52f is 4 μm.

The item of [exfoliation occurrence frequency] of Fig. 12 is the frequency of occurrence of peeling after the second joining as in the description of Fig. 9 . That is, when the number of samples of each condition of the angle θ1 was evaluated by 32, [○] means that no peeling occurred, and [x] means that peeling occurred.

The angle θ1 is smaller than the angle θ2. According to this, since the second inclined surface 52f can press the metal wire at the time of temporary joining, the joint strength of the tail wire joint portion can be improved. Further, from the evaluation results shown in FIG. 12, it is found that the peeling failure does not occur when the angle θ1 is 0.5 degrees or more and 11 degrees or less. When the angle θ1 is 11 degrees or less, the metal wire can be pressed by the second inclined surface 52f at the time of temporary bonding. According to this, it is possible to generate a stress that can obtain a sufficient joint strength of the tail wire joint portion. Therefore, the occurrence of peeling failure can be suppressed.

Figs. 13(a) and 13(b) are views for explaining a welding pin according to the embodiment. FIGS. 13(a) and 13(b) show the appearance of the tip end (the first pressing surface 51 and the second pressing surface 51) of the welding pin 110 as viewed in the axial direction. Fig. 13 (a) is a laser microscope image, and Fig. 13 (b) is a plan view corresponding to Fig. 13 (a).

The boundary B1 of the first inclined surface 51s and the second inclined surface 52f is, for example, a substantially circular shape centering on the central axis 20a as shown in Fig. 13(b). However, when viewed in the axial direction, the shape of the boundary B1 is not a true circle (or an ellipse) but a saw shape (a zigzag shape). That is, the distance L1 from the central axis 20a to the point on the boundary B1 varies along the circumferential direction Dc. Specifically, the point on the upper boundary B1 is scattered in a range of a circle (or ellipse) obtained by approximating (or smoothing) the shape of the boundary B1, for example, within 1.5 μm.

As described with reference to FIGS. 8(a) and 8(b), the metal wire BW receives a large stress from the welding pin in the vicinity of the contact with the boundary B1 of the first inclined surface 51s and the second inclined surface 52f. Further, as shown in FIGS. 13(a) and 13(b), the boundary B1 is in a saw shape, and the boundary B1 is brought into contact with the metal wire BW. That is, a large stress is generated in which the contact portion of the boundary B1 of the metal wire BW and the metal wire BW increases. According to this, when an ultrasonic wave is applied, for example, the stress on the metal wire BW is repeatedly generated. The above-mentioned micro cracks are likely to occur, and the cutting property of the metal wire can be improved.

Fig. 14 is a view exemplifying the evaluation results of the welding pins. FIG. 14 shows the results of determination of the joint strength in the examples (Comparative Examples 10 to 12 and Examples 15 to 20) in which the uneven shape of the first inclined surface 51s is different. In this evaluation, the average height Rc of the roughness curve element, the skewness Rsk of the roughness curve, and the maximum mountain height Rp of the roughness curve are changed to be the uneven shape of the first inclined surface 51s.

The average height Rc is obtained by the following formula (2). The skewness Rsk is obtained by the following formula (3). Formula (2) Formula (3)

In the formula (2), m is the number of contour curve elements, and Zti is the average value of the heights of the contour curve elements. In the formula (3), Zq is a root mean square height, and Zn is a value of a height in the roughness curve. The maximum mountain height Rp is the maximum value of the height in the roughness curve.

The skewness Rsk is a symmetry of a mountain (convex) and a valley (concave) indicating a concavo-convex shape. If the uneven shape is a sinusoidal distribution, the skewness Rsk becomes zero. The fact that the skewness Rsk is negative means that the area of the mountain (convex) is larger than the area of the valley (concave) (the tip end of the convex portion is smaller than the tip end of the concave portion).

The average height Rc, the skewness Rsk, and the maximum mountain height Rp in each of the examples (each condition) are shown in FIG. In this evaluation, the joint strength was determined based on the process capability index Cpk of the joint strength. In each of the examples shown in Fig. 14, the average of the joint strength of the metal wire BW is Ave, and the lower limit of the joint strength is 3 gram weight (gf), and Cpk = (Ave - 3gf) / 3 σ. Calculation. The joint strength is the strength under a pull test in the second weld. The number of samples is 30. The Cpk of the joint strength in the wire bonding is generally required to be 1.67 or more.

In the item of [joining strength determination] of Fig. 14, when Cpk is 1.67 or more, it means [OK], and when Cpk is less than 1.67, it means [NG]. In each of the examples (each combination of Rc, Rsk, and Rp), it was determined after the wire bonding as follows: initial, after 500,000 wire bonding, 1 million wire bonding, and 150 After 10,000 times of wire bonding.

In Examples 15 to 20 and Comparative Examples 10 to 12, the initial joint strength was judged to be [OK]. After the wire bonding was performed 500,000 times, Examples 15 to 20 were [OK], but Comparative Examples 10 to 12 were both [NG]. After 15 million wire bonding, Examples 15 to 17, 19, and 20 were [OK], and Example 18 and Comparative Examples 10 to 12 were [NG]. After the wire bonding was performed 1.5 million times, Examples 19 and 20 were [OK], and Examples 15 to 18 and Comparative Examples 10 to 12 were [NG].

As a result of the above, the skewness Rsk of the first inclined surface 51s is about -1.2 or more and 0.3 or less, and the average height Rc of the first inclined surface 51s is preferably 0.06 μm or more and 0.3 μm or less. When the average height Rc is not 0.06 μm or more, the grip force is small, and in particular, in the case of using the metal wire BW of the copper wire, sufficient joint strength cannot be obtained. Further, when the average height Rc exceeds 0.3 μm, it becomes difficult to form irregularities of -0.3 or less with the skewness Rsk. Further, it is more preferable that the skewness Rsk of the distal end surface 50 is about -1.2 or more to 0.43 or less, and the average height Rc of the distal end surface 50 is 0.16 μm or more and 0.3 μm or less. According to this, the initial bonding strength can be maintained even after 1.5 million times from the initial stage of bonding.

Further, it is preferable that the maximum mountain height Rp of the first inclined surface 51s is 0.9 times or less (Rp/Rc ≦ 0.9) of the average height Rc. Moreover, Rp/Rc can be 0.5 times or more. When Rp/Rc exceeds 0.9, it is difficult to maintain the initial bonding strength for a long period of time. On the other hand, when Rp/Rc is 0.9 or less, the shape change accompanying wear during use is small, and the joint strength at the initial stage of the long period is maintained.

Fig. 15 is a view exemplifying the evaluation results of the welding pins. 15 is an evaluation result showing an example in which the kurtosis Rku of the roughness curve of the second inclined surface 52f is different (Comparative Examples 13, 14 and Examples 21 to 23). The kurtosis Rku is obtained by the following formula (4). Formula (4) Rq is the root mean square height of the roughness curve, lr is the reference length, and Z(x) is the roughness curve (the height of the mountain). That is to say, the kurtosis (Rku) refers to the fourth power of Z(x) in the reference length divided by the fourth power of the root mean square. The kurtosis Rku is the [sharpness] indicating the roughness curve. The unevenness of the surface is sharper as the Rku is larger.

The item of [exfoliation occurrence frequency] of Fig. 15 is the frequency of occurrence of peeling after the second joining as in the description of Fig. 9 . That is, when the number of samples in each example was evaluated by 32, [○] means that no peeling occurred, and [x] means that peeling occurred.

As a result of FIG. 15, the kurtosis Rku of the second inclined surface 52f is preferably 5.0 or less, more preferably 3.0 or less. When the kurtosis Rku of the second inclined surface 52f is 5 μm or less, the sliding of the metal wire BW and the second inclined surface 52f is promoted when the metal wire is cut. According to this, the cutting property of the metal wire can be improved.

The embodiments of the present invention have been described above. However, the present invention is not limited to the descriptions. With regard to the above-described embodiments, it is within the scope of the present invention to incorporate design changes as appropriate to those skilled in the art. For example, the shape, size, material, arrangement, installation form, and the like of each element provided in the insertion hole, the first pressing surface, the second pressing surface, and the like are not limited to those exemplified, and can be appropriately changed. Further, each element included in each embodiment described above is technically combinable as much as possible, and each element included in each of the above-described embodiments is included in the scope of the present invention as long as it includes the features of the present invention.

According to the aspect of the invention, it is possible to provide a welding pin which can improve the joint strength, improve the cuttability of the wire, and suppress abrasion.

10‧‧‧ Body Department
11‧‧‧Cylinder
11h‧‧‧ hole
12‧‧‧Cone
13‧‧‧ Bottleneck
20‧‧‧ inserted through hole
20a‧‧‧Center axis
21‧‧‧Conical hole
22‧‧‧ Straight hole
51‧‧‧First pressing surface
51s‧‧‧First inclined surface
52‧‧‧Second pressing surface
52f‧‧‧Second inclined surface
52t‧‧‧ Cone
110‧‧‧ soldering needle
200‧‧‧ wire
A, B, C, D‧‧‧ areas
B1‧‧‧ border
BW‧‧‧metal wire
Cpk‧‧‧Process Capability Index
Cr‧‧‧ imaginary circle
Da‧‧‧ axial
Dc‧‧‧ Zhou Xiang
D1‧‧‧ OD
D2‧‧‧Down
F1, F11, F12, F2, F21, F22‧‧‧ vectors
FT1, FT2‧‧‧ pull
P1‧‧‧ face
SB‧‧‧pin joints
TB‧‧‧ tail wire joint TB
T‧‧‧ top diameter
Rc‧‧ average height
Rku‧‧‧ kudu
Rp‧‧‧Max Mountain Height
Rsk‧‧‧ skewness
Rz‧‧‧Max height
RΔq‧‧‧ root mean square slope
W1‧‧‧Width θ, θ1~θ6‧‧‧ Angle

Fig. 1 is a schematic view showing a welding pin according to the embodiment. Fig. 2 is a schematic enlarged view showing a distal end of a welding pin according to the embodiment. Fig. 3 is a schematic enlarged view showing a distal end of a welding pin according to the embodiment. 4(a) and 4(b) are schematic cross-sectional views illustrating a tip end of a welding pin according to the embodiment. Fig. 5 is a schematic cross-sectional view showing a tip end of a welding pin according to the embodiment. Fig. 6 is a schematic cross-sectional view showing a state in which wire bonding is performed. 7(a) and 7(b) are photographic images illustrating bonding wires and wires. Figs. 8(a) and 8(b) are schematic views for explaining the cutting of the metal wire by the welding pin according to the embodiment. Fig. 9 is a view exemplifying the evaluation results of the welding pins. Fig. 10 is a view exemplifying the evaluation results of the welding pins. Fig. 11 is a view exemplifying the evaluation results of the welding pins. Fig. 12 is a view exemplifying the evaluation results of the welding pins. Figs. 13(a) and 13(b) are views for explaining the tip end of the welding pin according to the embodiment. Fig. 14 is a view exemplifying the evaluation results of the welding pins. Fig. 15 is a view exemplifying the evaluation results of the welding pins.

10‧‧‧ Body Department

11‧‧‧Cylinder

12‧‧‧Cone

13‧‧‧ Bottleneck

20‧‧‧ inserted through hole

110‧‧‧ soldering needle

A‧‧‧ area

Da‧‧‧ axial

Claims (11)

A welding pin characterized by comprising: a body portion of a member: an insertion hole through which a metal wire is inserted; pressing the metal wire, and providing an axial inclination of the insertion hole extending around the insertion hole a first pressing surface of the first inclined surface; the metal wire is pressed, and has a tapered surface disposed between the first inclined surface and the insertion hole, and is disposed on the tapered surface and the first a second pressing surface of the second inclined surface between the inclined surfaces, wherein a root mean square slope of the roughness curve element of the second inclined surface is smaller than a root mean square slope of the roughness curve element of the first inclined surface. The welding pin of claim 1, wherein the root mean square slope of the roughness curve element of the first inclined surface is 8゚ or more, and the root mean square slope of the roughness curve element of the second inclined surface is 5゚the following. The welding pin of claim 1 or 2, wherein the root mean square slope of the roughness curve element of the first inclined surface is 11 ゚ or more, and the root mean square of the roughness curve element of the second inclined surface The slope is 2 ゚ or less. The welding pin of claim 1 or 2, wherein the width of the second inclined surface is 2% or more and 8% or less of the outer diameter of the first pressing surface when viewed along the axial direction. The welding pin of claim 1 or 2, wherein the first inclined surface has a maximum height Rz of 0.2 μm or more, and the second inclined surface has a maximum height Rz of 0.16 μm or less. The welding pin of claim 1 or 2, wherein the first inclined surface has a maximum height Rz of 0.3 μm or more, and the second inclined surface has a maximum height Rz of 0.10 μm or less. The welding pin of claim 1 or 2, wherein the axially perpendicular surface and the second inclined surface form an angle which is perpendicular to the axial direction of the surface and the first inclined surface The angle is small. The welding pin of claim 1 or 2, wherein an angle formed by the axially perpendicular surface and the second inclined surface is 11 degrees or less. The welding pin of claim 1 or 2, wherein the boundary between the first inclined surface and the second inclined surface is saw-shaped when viewed along the axial direction. The welding pin of claim 1 or 2, wherein the first inclined surface has a skewness of -0.3 or less, and the first inclined surface has an average height of 0.06 μm or more and 0.3 μm or less. The welding pin of claim 1 or 2, wherein the second inclined surface has a kurtosis of 5.0 or less.