JP2017017306A - Bonding capillary - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bonding capillary capable of improving bond strength, improving segmentation of wire, and suppressing abrasion.SOLUTION: There is provided a bonding capillary including a body comprising: a through-hole into which a wire is inserted; a first pressing face which presses on the wire and which 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 which has a taper face with a tapered shape 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. 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.SELECTED DRAWING: Figure 3

Description

  Aspects of the invention generally relate to bonding capillaries.

  In the manufacturing process of a semiconductor device, wire bonding is performed in which a semiconductor element and a lead frame are connected by a bonding wire (hereinafter referred to as “wire”). In wire bonding, one end of a wire is bonded to an electrode pad of a semiconductor element using a bonding capillary (first bond). Next, the wire is drawn and joined to the lead (second bond). When bonding wires, ultrasonic waves are applied in a state where the wires are pressed by a bonding capillary.

  For example, in the second bond, a main bonded portion (stitch bond) between the wire and the lead and a temporary bonded portion (tail bond) between the wire and the lead are formed. After such a second bond, the wire extending from the tail bond is cut (cut). Thereafter, the semiconductor device is manufactured by sealing the semiconductor element and the lead frame connected by the wire with a sealing resin.

  In recent years, semiconductor devices are used in, for example, in-vehicle electronic devices, and are used under severe temperature cycle environments. When a semiconductor device is used in a severe temperature cycle environment, a problem of peeling or cracking of the sealing resin may occur due to a difference in thermal expansion between the sealing resin and the metal. For this reason, high environmental reliability (temperature cycle reliability) is required in the semiconductor device manufactured as described above.

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

  In contrast, for example, a method using a lead frame called a roughened lead frame has been proposed. A thick plated layer containing nickel or the like is formed on the surface of the roughened lead frame, and the surface of the plated layer is roughened. Due to the rough surface, the adhesion between the lead frame and the sealing resin can be improved.

  However, when such a rough lead frame is used, a wire containing hard copper is pressed against a thick plating layer when performing a second bond. At this time, the wire may sink into the thick plating layer, and the bondability between the wire and the lead may deteriorate. And after the second bond, the breakability of the wire deteriorates. When the wire splitting property is deteriorated, there is a problem that a defect (peeling failure) occurs in which the joint part is peeled off when the wire is divided. Further, since the bonding capillary is pressed against the plating layer having a rough surface, the bonding capillary is likely to be worn, and the life of the bonding capillary may be deteriorated.

Special table 2009-540624 JP-A-2-163951

  The present invention has been made based on recognition of such a problem, and an object of the present invention is to provide a bonding capillary that can improve bonding strength, improve wire segmentation, and suppress wear.

  1st invention is the 1st press surface which presses the said wire through which the wire is penetrated, Comprising: It provided in the circumference | surroundings of the said through hole, and inclined with respect to the direction where the said through hole extends A first pressing surface having a first inclined surface and a second pressing surface for pressing the wire, the tapered surface having a taper shape provided between the first inclined surface and the insertion hole. And a second pressing surface having a second inclined surface provided between the tapered surface and the first inclined surface, and a rough surface of the second inclined surface. In the bonding capillary, the root mean square slope of the roughness curve element is smaller than the root mean square slope of the roughness curve element of the first inclined surface.

  According to this bonding capillary, the wire can be pressed with the rough first inclined surface during the main bonding, and the bonding strength of the stitch bond portion can be ensured. Furthermore, since the wire is pressed by the second inclined surface and the tapered surface at the time of temporary joining, the contact area between the bonding capillary and the wire is increased, and the joining strength of the tail bond portion can be improved. Further, when the wire is divided after joining, a large tensile force is generated on the wire by the first inclined surface having a large root mean square inclination. On the other hand, depending on the second inclined surface having a small root mean square inclination, a tensile force is hardly generated on the wire. By this action, the stress is maximized at a suitable position for cutting the wire (for example, the thinnest part of the wire) located near the boundary between the first inclined surface and the second inclined surface. For this reason, generation | occurrence | production of a microcrack is promoted, the deformation | transformation form of a microcrack becomes mode I (opening mode), and a crack progresses. Thereby, the parting property of a wire can be improved. Furthermore, in the second inclined surface having a root mean square inclination smaller than that of the first inclined surface, stress generated when the wire is pressed is dispersed, and wear of the bonding capillary can be suppressed.

  In a second aspect based on the first aspect, the root mean square slope of the roughness curve element of the first inclined surface is 8 ° or more, and the root mean square of the roughness curve element of the second inclined surface The square root inclination is a bonding capillary characterized by being 5 ° or less.

  According to this bonding capillary, when the root mean square inclination of the first inclined surface is 8 ° or more, the tensile force generated on the wire by the first inclined surface can be increased when the wire is divided. Moreover, when the root mean square inclination of the second inclined surface is 5 ° or less, the tensile force generated on the wire by the second inclined surface can be reduced when the wire is divided. For this reason, the deformation mode of the microcrack generated at the appropriate position for dividing the wire becomes mode I (opening mode), and the crack progresses. Thereby, the parting property of a wire can be improved.

  According to a third invention, in the first or second invention, the root mean square slope of the roughness curve element of the first inclined surface is 11 ° or more, and the roughness curve element of the second inclined surface Is a bonding capillary characterized by having a root mean square slope of 2 ° or less.

  According to this bonding capillary, the root mean square slope of the first inclined surface is 11 ° or more, and the root mean square slope of the second inclined surface is 2 ° or less. The difference between the root mean square slope of the first slope and the root mean square slope of the second slope is easily kept above a certain level. For this reason, it is possible to suppress a decrease in the difference between the tensile force generated on the wire by the first inclined surface and the tensile force generated on the wire by the second inclined surface. As a result, even if the bonding capillary is worn, the deformation mode of a microcrack that occurs at an appropriate position for cutting the wire becomes mode I, and the crack progresses. Accordingly, the wire breakability can be improved.

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

  According to the bonding capillary, when the width of the second inclined surface is 2% or more of the outer diameter of the first pressing surface when viewed along the axial direction, the maximum stress generated at the tip of the bonding capillary is reduced. It is possible to lower the critical stress that the material of the bonding capillary wears. Thereby, wear of the bonding capillary can be significantly suppressed. Furthermore, when the width of the second inclined surface is 8% or less of the outer diameter of the pressing surface when viewed along the axial direction, a stress capable of obtaining a sufficient bonding strength of the tail bond portion is generated. Can do.

  According to a fifth invention, in any one of the first to fourth inventions, a maximum height Rz of the first inclined surface is 0.2 micrometers or more, and a maximum height of the second inclined surface is The thickness Rz is a bonding capillary characterized by being 0.16 micrometers or less.

  According to this bonding capillary, since the maximum height Rz of the first inclined surface is 0.2 micrometers (μm) or more, the wire can be pressed by the first inclined surface, so that sufficient bonding strength is obtained. Can be obtained. Moreover, when the maximum height Rz of the second inclined surface is 0.16 micrometers or less, sliding between the wire and the bonding capillary is promoted. Thereby, the parting property of a wire can be improved. As described above, occurrence of peeling failure can be suppressed.

  According to a sixth invention, in any one of the first to fifth inventions, a maximum height Rz of the first inclined surface is 0.3 micrometers or more, and a maximum height of the second inclined surface is The thickness Rz is a bonding capillary characterized by being 0.10 micrometers or less.

  According to this bonding capillary, since the maximum height Rz of the first inclined surface is 0.3 micrometers or more, even if the bonding capillary is worn, the maximum height Rz of the first inclined surface is more than a certain value. Easy to keep in. Thereby, even if the bonding capillary is worn, the wire can be held by the first inclined surface, so that a sufficient bonding strength can be obtained. Further, even when the bonding capillary is worn, the maximum height Rz of the second inclined surface is 0.10 micrometer or less, so that sliding between the wire and the bonding capillary can be promoted. Thereby, the parting property of a wire can be improved.

  In a seventh aspect based on any one of the first to sixth aspects, an angle formed between a surface perpendicular to the axial direction and the second inclined surface is perpendicular to the axial direction. A bonding capillary characterized by being smaller than an angle formed by a surface and the first inclined surface.

  According to this bonding capillary, since the wire is pressed by the second inclined surface during temporary bonding, the bonding strength of the tail bond portion can be improved.

  An eighth invention is characterized in that, in any one of the first to seventh inventions, an angle formed by a surface perpendicular to the axial direction and the second inclined surface is 11 degrees or less. A bonding capillary.

  According to this bonding capillary, since the angle between the surface perpendicular to the axial direction and the second inclined surface is 11 degrees or less, the stress that can obtain a sufficient bonding strength of the tail bond portion at the time of temporary bonding (The force with which the second pressing surface presses the wire) can be generated.

  According to a ninth invention, in any one of the first to eighth inventions, the boundary between the first inclined surface and the second inclined surface is saw-shaped when viewed along the axial direction. It is a bonding capillary characterized by being.

  According to this bonding capillary, stress is repeatedly generated in the wire during the bonding operation due to the saw shape at the boundary between the first inclined surface and the second inclined surface. Thereby, it becomes easy to produce a micro crack in a wire. Therefore, it is possible to improve the breakability of the wire and suppress the occurrence of peeling failure.

  In a tenth aspect based on any one of the first to ninth aspects, the skewness of the first inclined surface is −0.3 or less, and the average height of the first inclined surface is 0. A bonding capillary characterized by having a thickness of .06 micrometers or more and 0.3 micrometers or less.

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

  An eleventh invention is the bonding capillary according to any one of the first to tenth inventions, wherein the kurtosis of the second inclined surface is 5.0 or less.

  According to this bonding capillary, when the kurtosis of the second inclined surface is 5.0 or less, sliding between the wire and the bonding capillary is promoted, and the breakability of the wire can be improved.

  According to the aspect of the present invention, there is provided a bonding capillary that can improve the bonding strength, improve the wire cutting property, and suppress wear.

It is a schematic diagram which illustrates the bonding capillary which concerns on this embodiment. It is a typical enlarged view which illustrates the tip of the bonding capillary concerning this embodiment. It is a typical enlarged view which illustrates the tip of the bonding capillary concerning this embodiment. 4A and 4B are schematic cross-sectional views illustrating the tip of the bonding capillary according to this embodiment. It is a typical sectional view which illustrates the tip of the bonding capillary concerning this embodiment. It is typical sectional drawing which illustrates the state of wire bonding. FIG. 7A and FIG. 7B are photographic images illustrating bonding wires and leads. FIG. 8A and FIG. 8B are schematic diagrams for explaining wire cutting by the bonding capillary according to the present embodiment. It is a figure which illustrates the evaluation result of a bonding capillary. It is a figure which illustrates the evaluation result of a bonding capillary. It is a figure which illustrates the evaluation result of a bonding capillary. It is a figure which illustrates the evaluation result of a bonding capillary. FIG. 13A and FIG. 13B are views illustrating the tip of the bonding capillary according to this embodiment. It is a figure which illustrates the evaluation result of a bonding capillary. It is a figure which illustrates the evaluation result of a bonding capillary.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, in each drawing, the same code | symbol is attached | subjected to the same component and detailed description is abbreviate | omitted suitably.

(Embodiment)
FIG. 1 is a schematic view illustrating a bonding capillary according to this embodiment.
FIG. 2 is a schematic enlarged view illustrating the tip shape of the bonding capillary according to this embodiment.
FIG. 1 shows the entire bonding capillary 110. FIG. 2 shows an enlarged view of the region A shown in FIG.

  As shown in FIG. 1, the bonding capillary (hereinafter sometimes referred to as “capillary”) 110 has a main body 10. The main body 10 is a cylindrical member and has an insertion hole 20. The insertion hole 20 is a through hole extending in the axial direction Da of the main body 10. When the capillary is used, the wire is inserted into the insertion hole 20.

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

  In the specification of the present application, the distal end side or the distal end direction refers to a direction from the end portion on the cylindrical portion 11 side toward the end portion on the bottle neck portion 13 side. The tip of the capillary (main body part) refers to the end part on the bottle neck part 13 side.

  The cylindrical portion 11 has a diameter for mechanically fixing the capillary 110 to the bonding apparatus.

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

  The diameter of the bottle neck portion 13 is smaller than the diameter of the conical portion 12. For example, the diameter of the bottleneck portion 13 gradually decreases along the tip direction. Since the diameter of the bottleneck portion 13 is small, it is possible to perform wire bonding at a predetermined position while avoiding an adjacent wire already wired.

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

FIG. 3 is a schematic enlarged view illustrating the tip of the bonding capillary according to this embodiment. FIG. 3 is a perspective view of the tip of the capillary shown in FIG. 2 as viewed obliquely from below.
As shown in FIG. 3, the main body 10 includes a first pressing surface 51 and a second pressing surface 52 provided at the end in the axial direction.

  The first pressing surface 51 is provided around the insertion hole 20 at the tip of the main body 10. The 1st press surface 51 is a part of surface of the bottleneck part 13, for example, is a curved surface shape.

  The second pressing surface 52 is provided between the insertion hole 20 and the first pressing surface 51. The second pressing surface 52 is a part of the surface of the bottle 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 that press the wire against the lead frame in wire bonding. For example, the first pressing surface 51 is a pressing surface that forms the main bonding, and the second pressing surface 52 is a pressing surface that forms the temporary bonding.

Details of the shapes of the first pressing surface 51 and the second pressing surface 52 will be further described.
FIG. 4A, FIG. 4B, and FIG. 5 are schematic cross-sectional views illustrating the tip of the bonding capillary according to this embodiment.
FIG. 4A shows a cross section taken along line A1-A2 shown in FIG. That is, FIG. 4A shows a cross section in a plane parallel to the axial direction Da. FIG. 4B illustrates an enlarged cross section of the region B illustrated in FIG.

  As shown in FIG. 4B, 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 increases toward the tip side.

  The first pressing surface 51 has a first inclined surface 51 s provided around the insertion hole 20. The first inclined surface 51s is inclined with respect to the axial direction Da and the radial direction (a direction perpendicular to the axial direction Da). Then, the diameter of the first inclined surface 51 s becomes smaller toward the distal end side of the main 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 tip direction. In this example, the cross-sectional shape of the first inclined surface 51 s in FIG. 4B includes a curved portion, but may be a linear shape or may be configured 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 52 t is a portion of the second pressing surface 52 that faces the tapered hole 21. The tapered surface 52t has a tapered shape that widens toward the tip. That is, the distance between the central axis 20a of the insertion hole 20 and the tapered surface 52t is longer along the distal 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 that is continuous with the tapered surface 52t and the first inclined surface 51s, and is located on the most distal end side of the bottle 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 ° described later). However, the second inclined surface 52f may be slightly inclined from 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 on the surface of the second inclined surface 52f is smaller than the uneven shape on the surface of the first inclined surface 51s, and the uneven shape on the surface of the tapered surface 52t is smaller than the uneven shape on the surface of the first inclined surface 51s. Is also small. 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 slope 51s. In addition, 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 slope 51s. The root mean square slope (RΔq) of the roughness curve element represents the irregular shape of the surface and is a parameter corresponding to the magnitude of the irregularity slope.

  FIG. 5 illustrates a cross-section obtained by further enlarging FIG. In the example shown in FIG. 5, the diameter of the second inclined surface 52 f is smaller toward the tip side of the main body 10. That is, the distance between the central axis 20a of the insertion hole 20 and the second inclined surface 52f is shortened along the distal direction. For example, the intersection (intersection line) between the tapered surface 52 t and the second inclined surface 52 f is located at the foremost end of the main body 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 plane 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. It is desirable that the angle θ1 is 0 degree or more and 11 degrees or less. The angle θ2 is preferably, for example, 2 degrees or more and 45 degrees or less.

Next, bonding (second bonding) using a bonding capillary will be described.
FIG. 6 is a schematic cross-sectional view illustrating the state of wire bonding.
The wire BW inserted through the insertion hole 20 of the capillary 110 is first bonded to an electrode or the like of a semiconductor element (not shown). Thereafter, the capillary 110 is drawn around the lead 200 in a predetermined orbit to form a loop on the wire BW. Next, second bonding for bonding the wire BW to the lead 200 is performed. FIG. 6 shows a second bonding state in which the lead 200 of the lead frame and the wire BW are joined.

  The lead frame used in this embodiment is a rough lead frame, for example. That is, on the surface of the lead 200, a thick Ni plating layer or the like subjected to roughening treatment is provided. The thickness of the plating layer is, for example, about 20 μm. For example, copper is used as the material of the wire BW.

  In the second bonding, the capillary 110 is pressed onto the lead 200. Accordingly, the wire BW is sandwiched between the first pressing surface 51 (first inclined surface 51s) and the lead 200. Further, the wire BW is sandwiched between the second pressing surface 52 and the lead 200.

  Since the first inclined surface 51 s is inclined toward the second inclined surface 52 f, the distance between the first inclined surface 51 s and the lead 200 becomes narrower along the direction toward the inside of the capillary 110. . Therefore, the thickness of the wire BW sandwiched between the first inclined surface 51 s and the lead 200 is reduced along the direction toward the inside of the capillary 110.

  The thickness of the wire BW is the thinnest between the second inclined surface 52f and the lead 200. Since the taper surface 52t has a taper shape, the interval between the taper surface 52t and the lead 200 becomes wider along the direction toward the inside of the capillary 110. Accordingly, the thickness of the wire BW sandwiched between the tapered surface 52t and the lead 200 increases along the direction toward the inside of the capillary 110.

  In this manner, for example, an ultrasonic wave is applied to the capillary 110 with the wire BW sandwiched between the capillary 110 and the lead 200. Thereby, the wire BW is crimped to the lead 200. A main joint (stitch bond portion SB) is formed between the first pressing surface 51 (first inclined surface 51s) and the lead 200, and the second pressing surface 52 (second inclined surface 52f and A temporary joint portion (tail bond portion TB) is formed between the tapered surface 52t) and the lead 200.

  After crimping the wire BW, the capillary 110 is raised with the wire BW clamped by the capillary 110. As a result, the wire BW is cut off from the tail bond portion TB. For example, since the intersection (intersection line) between the second inclined surface 52f and the tapered surface 52t is formed relatively sharply, the wire BW is divided at a portion pressed by this intersection.

  FIG. 7A and FIG. 7B are photographic images illustrating bonding wires and leads 200. 7 (a) and 7 (b), the joint after the second bonding is performed is shown enlarged.

  As shown in FIG. 7A, after the second bonding using the capillary 110 according to the present embodiment, the wire BW is joined to the lead 200 and separated from the tail bond portion TB.

  In such second bonding, when a rough lead frame is used, the wire tends to sink into the lead when the capillary is pressed against the lead. For this reason, joining strength deteriorates and the parting property of a wire may deteriorate.

  FIG. 7B illustrates a defect that occurs when the wire breakability deteriorates. When the dividing property of the wire is deteriorated, as shown in the region C shown in FIG. 7B, when the wire is divided, a part of the bonding portion (for example, the stitch bond portion SB) is peeled off, which is called peeling or fishtail. Defects may occur.

  On the other hand, in the capillary 110 according to the present embodiment, the first inclined surface 51 s having a rough surface state is provided at the tip of the capillary 110. For this reason, the wire BW can be efficiently pressed against the lead 200 by the first inclined surface 51s. Therefore, the bonding strength of the stitch bond portion SB can be ensured.

  In the capillary 110 according to the present embodiment, a smooth second inclined surface 52f and a tapered surface 52t are provided at the tip of the capillary 110. The wire BW is pressed against the lead 200 by the second inclined surface 52f and the tapered surface 52t. For this reason, compared with the case where the 2nd inclined surface 52f is not provided, the contact area of the capillary 110 and the wire BW increases, and it can improve the joint strength of the tail bond part TB.

  Further, when the wire is divided after the joining, the wire BW is pressed by the rough first inclined surface 51s, and the sliding between the wire BW and the capillary 110 is promoted by the smooth second inclined surface 52f. Thereby, the parting property of a wire can be improved.

FIG. 8A and FIG. 8B are schematic views for explaining wire division by the bonding capillary according to the embodiment.
FIG. 8A is a conceptual diagram for explaining the action of the capillary when the wire is divided. FIG. 8A shows an enlarged cross section of a region where the capillary 110 and the wire BW are in contact with each other in the vicinity of the boundary between the first inclined surface 51s and the second inclined surface 52f. This region corresponds to an appropriate position for dividing the wire BW, that is, the thinnest portion of the wire BW.

  The left side of the capillary 110 in the figure corresponds to the first inclined surface 51s having a large RΔq (root mean square inclination), and the right side corresponds to the second inclined surface 52f having a small RΔq. It is shown that the slope of the unevenness with respect to the wire surface is larger when RΔq representing the uneven shape is larger. That is, for example, the angle θ3 shown in FIG. 8A is larger than the angle θ4.

  When dividing the wire BW, ultrasonic waves are applied in a state where the capillary 110 is in contact with the wire BW as shown in FIG. As a result, force is applied to the capillary 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 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 in a direction along the surface of the second inclined surface 52f. The vector F22 is a vector in a direction perpendicular to the vector F21. Here, the vector F21 increases as RΔq decreases. That is, when RΔq is small, the component deviating upward is increased as in the vector F21. For this reason, the force transmitted from the surface of the capillary 110 to the wire BW is reduced. Accordingly, the tensile force FT2 generated on the 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 in a direction along the surface of the first inclined surface 51s. The vector F12 is a vector in a direction perpendicular to the vector F12. In the first inclined surface 51s, since RΔq is large, the component deviating upward is small as in the vector F11. For this reason, the tensile force FT1 generated in the wire BW by the first inclined surface 51s having a large RΔq is large.

  In the capillary 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 provided adjacent to each other. For this reason, a large stress is generated due to the difference between the tensile force FT1 and the tensile force FT2 at an appropriate position for dividing the wire located near the boundary between the first inclined surface 51s and the second inclined surface 52f. For this reason, as shown in FIG. 8A, generation of a microcrack is promoted near the boundary between the first inclined surface 51s and the second inclined surface 52f. And in the micro crack which generate | occur | produced, the deformation | transformation form of a micro crack becomes mode I (opening mode) like FIG.8 (b). Thereby, like the area | region D of Fig.8 (a), a crack progresses and the parting property of a wire can be improved. As a result, occurrence of defects such as peeling can be suppressed.

  Further, since the surface of the roughened lead frame is rough, the tip of the capillary is easily worn by pressing the capillary. On the other hand, the second inclined surface 52 f is provided so as to be substantially parallel to the surface of the lead 200. Further, since RΔq of the second inclined surface 52f is small, as shown in FIG. 8A, the tip 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 angle θ6 of the convex portion of the first inclined surface 51s. For this reason, concentration of stress at the tip of the capillary 110 can be suppressed, and wear of the capillary can be suppressed.

  Hereinafter, an example of the capillary 110 according to the present embodiment will be described with reference to an evaluation result regarding the bonding capillary.

In the specification of the present application, the irregular shape (RΔq, Rz, Rc, Rsk, Rp, Rku, etc.) on the capillary surface is calculated based on JIS B 0601-2001. In each evaluation, a roughness curve was measured under the following conditions. The uneven shape is calculated from the measurement result of the roughness curve.
Measuring instrument: Laser microscope (Olympus, OLS4000)
Measurement magnification: 50 times Evaluation length: 125 μm to 400 μm
Cut-off (phase compensation type high-pass filter) λc: 25 μm
FIG. 9 is a diagram illustrating an evaluation result of the bonding capillary.
FIG. 9 shows a combination of the root mean square slope RΔq (°) of the roughness curve element of the first inclined surface 51s and the root mean square slope RΔq (°) of the roughness curve element of the second slope 52f. Shows evaluation results of examples (Comparative Examples 1 to 4, Examples 1 to 8) different from each other. In this evaluation, RΔq of the first inclined surface 51s was set to 5.4 ° to 12.4 °. Further, RΔq of the second inclined surface 52f was set to 1.8 ° to 13.4 °. Note that RΔq of the tapered surface 52t is the same as RΔq of the second inclined surface 52f.

The root mean square slope RΔq of the roughness curve element can be calculated based on the following equation (1). l is the reference length, and Z (x) is the height value in the roughness curve.

FIG. 9 shows the evaluation result of the occurrence frequency of peeling failure. Here, the item “Peeling occurrence frequency” represents the occurrence frequency of peeling after the second bonding. The number of samples was 32 or 128 for each of Comparative Examples 1 to 4 and Examples 1 to 8 shown in FIG. “X” represents that peeling occurred in 32 samples. That is, “x” means that the occurrence frequency of peeling is 1/32 or more. “◯” indicates that peeling did not occur in 32 samples, but peeling occurred when the number of samples was increased. “◯” means that the occurrence frequency of peeling is 1/127 or more and less than 1/32. “◎” represents that no peeling occurred in 128 samples. That is, “◎” means that the occurrence frequency of peeling is less than 1/128.

  As in Comparative Examples 1 to 3, it can be seen that peeling is likely to occur when RΔq of the first inclined surface 51s and RΔq of the second inclined surface 52f are both large or small.

  On the other hand, as in Examples 1 to 8, when RΔq of the first inclined surface 51s is 8 ° or more and RΔq of the second inclined surface 52f is 5 ° or less, the peeling of The frequency of occurrence is low. Further, as in Examples 7 and 8, when the RΔq of the first inclined surface 51s is 11 ° or more and the RΔq of the second inclined surface 52f is 2 ° or less, further peeling is performed. Occurrence can be suppressed. As described with reference to FIGS. 8A and 8B, this is considered to be due to the large tensile force caused by the first inclined surface 51s and the small tensile force caused by the second inclined surface 52f. . The occurrence of a microcrack is promoted at an appropriate position for dividing the wire, and the deformation mode of the microcrack becomes mode I (opening mode), and the crack progresses. Thereby, the parting property of a wire improves.

  Further, when RΔq of the first inclined surface 51s is set to 11 ° or more and RΔq of the second inclined surface 52f is set to 2 ° or less, the first inclined surface 51s even if the bonding capillary is worn. It is easy to keep the difference between RΔq of R2q and RΔq of the second inclined surface 52f above a certain level. For this reason, the stress which arises in the wire BW by the difference in tensile force can be maintained.

FIG. 10 is a diagram illustrating an evaluation result of the bonding capillary.
FIG. 10 is a diagram illustrating an evaluation result when the width W1 of the second inclined surface 52f is changed with respect to the tip diameter T of the capillary 110. FIG.

  Here, the width W1 of the second inclined surface 52f is the width of the second inclined surface 52f when the capillary 110 is viewed along 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 along the axial direction (see FIGS. 4A and 4B). At this time, the width W1 is ½ times the difference between the outer diameter D1 and the inner diameter D2. In addition, when an outer diameter changes along the circumferential direction, you may use the average value in the circumferential direction as outer diameter D1. When the inner diameter changes along the circumferential direction, an average value in the circumferential direction may be used as the inner diameter D2.

  The tip diameter T of the capillary 110 is the outer diameter of the annular first inclined surface 51s (first pressing surface 51) when viewed along the axial direction. Specifically, for example, the outer diameter of the first inclined surface 51s is an imaginary circle Cr formed by intersecting an extended surface of the outer peripheral surface of the bottle neck portion 13 and a plane including the second inclined surface 52f. (See FIG. 4 (a) and FIG. 4 (b)).

  FIG. 10 shows the evaluation result of the occurrence frequency of peeling failure. Here, the item “Peeling occurrence frequency” represents the occurrence frequency of peeling after the second bonding. In this evaluation, the number of samples is 32 for each ratio of the width W1 to the tip diameter T shown in FIG. “◯” indicates that no peeling occurred. That is, “◯” means that the peeling occurrence rate is less than 1/32. “X” indicates that peeling has occurred. That is, “x” means that the occurrence rate of peeling is 1/32 or more. In the evaluation, a wire having a diameter of 25 μm was used. The tip diameter T of the capillary 110 was set to 75 μm.

  As can be seen from the evaluation results shown in FIG. 10, no peeling occurred when the ratio of the width W1 to the tip diameter T was 2% or more and 8% or less. That is, 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 of the capillary 110, and the bonding strength is lowered. On the other hand, when the ratio of the width W1 to the tip diameter T is less than 2%, the stress generated at the tip of the capillary 110 becomes large, and the tip of the capillary 110 is easily worn. In the embodiment, by setting the ratio of the width W1 to the tip diameter T to be 2% or more and 8% or less, sufficient bonding strength can be obtained while suppressing wear of the capillary 110.

FIG. 11 is a diagram illustrating an evaluation result of the bonding capillary.
FIG. 11 shows the evaluation results of examples (Comparative Examples 5-9, Examples 9-14) 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. Show. The maximum height Rz of the tapered surface 52t is the same as the maximum height Rz of the second inclined surface 52f. The maximum height Rz is the sum of the maximum value of the peak height and the maximum value of the valley depth in the reference length.

  FIG. 11 shows the evaluation result of the occurrence frequency of peeling failure. The item “Peeling occurrence frequency” represents the occurrence frequency of peeling after the second bonding, as described in FIG. That is, in each example (each condition), “◎” represents that no peeling occurred in 128 samples, “◯” represents that no peeling occurred in 32 samples, and “×” "" Indicates that peeling occurred in 32 samples.

  As can be seen from the evaluation results shown in FIG. 11, the maximum height Rz of the first inclined surface 51s is 0.2 μm or more, and the maximum height Rz of the second inclined surface 52f is 0.16 μm or less. At some point, the peeling occurrence frequency is “◯”. Further, as in Examples 13 and 14, 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. Sometimes the peeling occurrence frequency is “頻 度”.

  Since the maximum height Rz of the first inclined surface 51 s is 0.2 μm or more, the wire BW can be suppressed by the first inclined surface 51 s, so that sufficient bonding strength can be obtained. Further, since 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, sliding between the wire BW and the bonding capillary is promoted. Thereby, the parting property of the wire BW can be improved. As described above, 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, even if the capillary is worn, The maximum height Rz can be kept above a certain level. Thereby, in the same manner as described above, the wire breakability can be improved.

FIG. 12 is a diagram illustrating an evaluation result of the bonding capillary.
FIG. 12 shows an evaluation result when the angle θ1 (see FIG. 5) of the second inclined surface 52f is changed. In this evaluation, the angle θ1 is set to 0.5 degrees or more and 17 degrees or less. The angle θ2 of the first inclined surface was 20 degrees, and the width W1 of the second inclined surface 52f was 4 μm.

  The item “Peeling occurrence frequency” in FIG. 12 represents the occurrence frequency of peeling after the second bonding, as described in FIG. That is, when the number of samples of each condition of the angle θ1 is evaluated as 32, “◯” indicates that peeling has not occurred, and “x” indicates that peeling has occurred.

  The angle θ1 is desirably smaller than the angle θ2. Thereby, since the 2nd inclined surface 52f can hold down a wire at the time of temporary joining, the joining strength of a tail bond part can be improved. Further, as can be seen from the evaluation result shown in FIG. 12, no peeling failure occurs when the angle θ1 is not less than 0.5 degrees and not more than 11 degrees. If the angle θ1 is 11 degrees or less, the wire can be pressed by the second inclined surface 52f during temporary bonding. Thereby, it is possible to generate a stress capable of obtaining a sufficient bonding strength of the tail bond portion. Therefore, occurrence of peeling failure can be suppressed.

FIG. 13A and FIG. 13B are diagrams illustrating the bonding capillary according to the embodiment.
FIG. 13A and FIG. 13B show a state when the tips (the first pressing surface 51 and the second pressing surface 52) of the bonding capillary 110 are viewed along the axial direction. FIG. 13A is a laser microscope image, and FIG. 13B is a plan view corresponding to FIG.

  As shown in FIG. 13B, the boundary B1 between the first inclined surface 51s and the second inclined surface 52f is, for example, a substantially circular shape centered on the central axis 20a. However, when viewed along the axial direction, the shape of the boundary B1 is not a perfect circle (or an ellipse) but a saw shape (sawtooth shape, jagged shape). That is, the distance L1 from the central axis 20a to the point on the boundary B1 changes along the circumferential direction Dc. Specifically, the points on the boundary B1 vary in a range of, for example, 1.5 μm or less from a circle (or an ellipse) obtained by approximation (or smoothing) of the shape of the boundary B1.

  As described with reference to FIGS. 8A and 8B, the wire BW has a large stress from the capillary near the boundary B1 between the first inclined surface 51s and the second inclined surface 52f. Receive. Then, as shown in FIGS. 13A and 13B, the boundary B1 has a saw shape, so that the boundary B1 comes into further contact with the wire BW. That is, the contact portion between the boundary B1 and the wire BW that causes a large stress on the wire BW increases. Thereby, for example, when an ultrasonic wave is applied, stress is repeatedly generated in the wire BW. As described above, microcracks are easily generated, and the wire breakability can be improved.

FIG. 14 is a diagram illustrating an evaluation result of the bonding capillary.
FIG. 14 shows the determination results of the bonding strength in the examples (Comparative Examples 10-12, Examples 15-20) 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 peak height Rp of the roughness curve are changed as the uneven shape of the first inclined surface 51s.

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

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

  The skewness Rsk represents the symmetry between the concavo-convex peaks (convex) and valleys (concave). If the uneven shape is a sine distribution, the skewness Rsk is zero. When the skewness Rsk is negative, it means that the area of the peak (convex) is larger than the area of the valley (concave) (the sharpness of the convex part is smaller than the sharpness of the concave part).

  FIG. 14 shows the average height Rc, skewness Rsk, and maximum peak height Rp in each example (each condition). In this evaluation, the bonding strength was determined based on the process capability index Cpk of the bonding strength. In each example shown in FIG. 14, when the average of the bonding strength of the wire BW is Ave and the lower limit standard of the bonding strength is 3 gram weight (gf), the calculation is performed by Cpk = (Ave−3gf) / 3σ. The bonding strength is a strength in a pull test in the second bond. The number of samples is 30. In general, the joint strength Cpk in wire bonding is required to be 1.67 or more.

  In the item “bond strength determination” of FIG. 14, “OK” is indicated when Cpk is 1.67 or more, and “NG” is indicated when Cpk is less than 1.67. In each example (each combination of Rc, Rsk and Rp), after initial wire bonding 500,000 times, after wire bonding 1,000,000 times, and after wire bonding 1.5 million times Went.

  In Examples 15 to 20 and Comparative Examples 10 to 12, all of the initial bonding strength determinations are “OK”. After 500,000 times of wire bonding, Examples 15 to 20 are “OK”, but Comparative Examples 10 to 12 are all “NG”. After 1 million times of wire bonding, Examples 15 to 17, 19 and 20 are “OK”, and Example 18 and Comparative Examples 10 to 12 are “NG”. After 1.5 million times of wire bonding, Examples 19 and 20 are “OK”, and Examples 15 to 18 and Comparative Examples 10 to 12 are “NG”.

  From the above results, 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 0.06 μm or more and 0.3 μm. The following is preferable. If the average height Rc is 0.06 μm or more, the gripping force is small, and in particular, when a copper wire BW is used, sufficient bonding strength cannot be obtained. On the other hand, when the average height Rc exceeds 0.3 μm, it becomes difficult to form unevenness of −0.3 or less as the skewness Rsk. More preferably, the skewness Rsk of the tip surface 50 is about −1.2 or more and −0.43 or less, and the average height Rc of the tip surface 50 is 0.16 μm or more and 0.3 μm or less. As a result, the initial bonding strength can be maintained even after 1,500,000 times from the initial bonding.

  Further, the maximum peak height Rp of the first inclined surface 51s is preferably 0.9 times or less (Rp / Rc ≦ 0.9) of the average height Rc. Rp / Rc can be 0.5 times or more. When Rp / Rc exceeds 0.9, it becomes 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, there is little shape change due to wear during use, and the initial bonding strength is maintained for a long period of time.

FIG. 15 is a diagram illustrating an evaluation result of the bonding capillary.
FIG. 15 shows evaluation results of examples (Comparative Examples 13 and 14, Examples 21 to 23) having different kurtosis Rku of the roughness curve of the second inclined surface 52f. The kurtosis Rku is determined by the following equation (4).

Rq is the root mean square height of the roughness curve, lr is the reference length, and Z (x) is the roughness curve (peak height). That is, kurtosis (Rku) is obtained by dividing the fourth average of Z (x) in the reference length by the fourth power of the root mean square. The kurtosis Rku represents the “sharpness” of the roughness curve. The unevenness of the surface is sharper as Rku is larger.

  The item “Peeling frequency” in FIG. 15 represents the occurrence frequency of peeling after the second bonding, as described in FIG. That is, when the number of samples in each example was evaluated as 32, “◯” represents that peeling did not occur, and “x” represents that peeling occurred.

  From the result of FIG. 15, the kurtosis Rku of the second inclined surface 52f is preferably 5.0 or less, and more preferably 3.0 or less. When the kurtosis Rku of the second inclined surface 52f is 5 μm or less, sliding of the wire BW and the second inclined surface 52f is promoted when the wire is divided. Thereby, the parting property of a wire can be improved.

  The embodiment of the present invention has been described above. However, the present invention is not limited to these descriptions. As long as the features of the present invention are provided, those skilled in the art appropriately modified the design of the above-described embodiments are also included in the scope of the present invention. For example, the shape, dimensions, material, arrangement, installation form, and the like of each element included in the insertion hole, the first pressing surface, the second pressing surface, and the like are not limited to those illustrated, but may be changed as appropriate. it can. Moreover, each element with which each embodiment mentioned above is provided can be combined as long as technically possible, and the combination of these is also included in the scope of the present invention as long as it includes the features of the present invention.

DESCRIPTION OF SYMBOLS 10 Main body part, 11 Cylindrical part, 12 Conical part, 13 Bottle neck part, 20 Insertion hole, 20a Center axis, 21 Tapered hole, 22 Straight hole, 51 1st press surface, 51s 1st inclined surface, 52 Second pressing surface, 52f second inclined surface, 52t taper surface, 110 bonding capillary, 200 lead, A, B, C, D region, B1 boundary, F1, F11, F12, F2, F21, F22 vector, BW Wire, Cr virtual circle, Da axial direction, Dc circumferential direction D1 outer diameter, D2 inner diameter, P1 surface, SB stitch bond part, TB tail bond part, T tip diameter, W1 width, θ1-6 angle

Claims (11)

An insertion hole through which the wire is inserted;
A first pressing surface that presses the wire, the first pressing surface having a first inclined surface that is provided around the insertion hole and is inclined with respect to an axial direction in which the insertion hole extends;
A second pressing surface that presses the wire, and includes a tapered surface that is provided between the first inclined surface and the insertion hole and has a tapered shape; and the tapered surface and the first inclined surface. A second pressing surface having a second inclined surface provided therebetween,
A main body having
The bonding capillary characterized in that the root mean square slope of the roughness curve element of the second slope is smaller than the root mean square slope of the roughness curve element of the first slope. The root mean square slope of the roughness curve element of the first inclined surface is 8 ° or more,
2. The bonding capillary according to claim 1, wherein a root mean square slope of a roughness curve element of the second inclined surface is 5 ° or less. The root mean square slope of the roughness curve element of the first inclined surface is 11 ° or more,
3. The bonding capillary according to claim 1, wherein the root mean square slope of the roughness curve element of the second inclined surface is 2 ° or less. 4.   The width of the second inclined surface when viewed along the axial direction is 2% or more and 8% or less of the outer diameter of the first pressing surface. The bonding capillary according to any one of the above. The maximum height Rz of the first inclined surface is 0.2 micrometers or more,
5. The bonding capillary according to claim 1, wherein a maximum height Rz of the second inclined surface is 0.16 μm or less. The maximum height Rz of the first inclined surface is 0.3 micrometers or more,
The bonding capillary according to claim 1, wherein a maximum height Rz of the second inclined surface is 0.10 μm or less.   An angle formed between a surface perpendicular to the axial direction and the second inclined surface is smaller than an angle formed between the surface perpendicular to the axial direction and the first inclined surface. The bonding capillary according to any one of claims 1 to 6.   The bonding capillary according to any one of claims 1 to 7, wherein an angle formed by a surface perpendicular to the axial direction and the second inclined surface is 11 degrees or less.   The boundary between the first inclined surface and the second inclined surface has a saw shape when viewed along the axial direction, according to any one of claims 1 to 8. Bonding capillary. The skewness of the first inclined surface is −0.3 or less,
10. The bonding capillary according to claim 1, wherein an average height of the first inclined surface is 0.06 μm or more and 0.3 μm or less.   11. The bonding capillary according to claim 1, wherein the kurtosis of the second inclined surface is 5.0 or less.