Conductive pin, power module, ultrasonic welding system and use method thereof

Abstract

A conductive pin for ultrasonic welding is provided. The conductive pin includes a body portion. The conductive pin also includes a pin head at one end of the body portion. The pin head defines a bonding surface that is configured to be ultrasonically welded to a workpiece. The bonding surface includes at least one of (i) a non-planar surface and (ii) an aperture defined in a central region of the bonding surface.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 607,533, filed on December 7, 2023, the content of which is incorporated herein by reference. Technical field

[0003] The present invention relates to ultrasonic welding, and more particularly, to improved systems and methods for performing ultrasonic welding operations, including welding of conductive pins. Background art

[0004] Ultrasonic energy is widely used to form interconnections between two or more materials. For example, wire bonding systems (such as ball bonders, wedge bonders, ribbon bonders, etc.) are used to bond / weld leads or ribbon materials to bonding / welding positions. Wire bonding employs relatively low energy levels (such as bond force, ultrasonic energy, etc.). An exemplary wire bonding system is sold by Kulicke and Soffa Industries, Inc., of Fort Washington, Pennsylvania.

[0005] Certain applications involve the bonding of materials other than leads. Welding has been considered for such applications. Ultrasonic welding is also a widely used technique. Ultrasonic welding can use an ultrasonic transducer (e.g., carrying a sonotrode) to convert electrical energy into mechanical motion / scrubbing (e.g., linear motion / scrubbing, torsional motion / scrubbing, etc.). However, existing ultrasonic welding techniques and equipment have limited ability to provide solutions that meet market demands in terms of cost, operation efficiency, flexibility, portability, and related factors.

[0006] U.S. Patent No. 10,882,134 (entitled "Ultrasonic Welding Systems and Methods of Using the Same"), U.S. Patent No. 11,364,565 (entitled "Ultrasonic Welding Systems and Methods of Using the Same"), and U.S. Patent Nos. 11,850,676 and 12,070,814 (entitled "Ultrasonic Welding Systems, Methods of Using the Same, and Related Workpieces Including Welded Conductive Pins"), assigned to Kulicke and Soffa Industries, Inc., relate to improvements in ultrasonic welding technology and are incorporated herein by reference in their entirety.

[0007] However, in the application of ultrasonic welding, including ultrasonic pin welding (where these pins are typically solder and / or press-fit into power modules), improvements are still needed. Accordingly, it is desirable to improve ultrasonic welding techniques, including ultrasonic pin welding. SUMMARY OF THE INVENTION

[0008] According to an exemplary embodiment of the present invention, a conductive pin for ultrasonic / ultrasonic welding is provided. The conductive pin includes a body portion. The conductive pin further includes a pin head located at one end of the body portion. The pin head defines a bonding surface configured to be ultrasonically welded to a workpiece. The bonding surface includes at least one of the following: (i) a non-planar surface and (ii) a hole defined in a central region of the bonding surface.

[0009] According to other embodiments of the present invention, the aforementioned conductive pin may have any one or more of the following features: the bonding surface includes a non-planar surface; the non-planar surface is a curved surface; the curved surface has a radius of curvature between 2 mm and 100 mm; the bonding surface includes a hole defined in a central region of the bonding surface; the hole has a maximum depth between 10 μm and 1000 μm; the hole extends through the entire length of the body portion of the conductive pin; the hole is a tapered hole; the hole is a curved hole; the curved hole has a radius of curvature between 2 mm and 100 mm; the hole is a cylindrical hole; the non-planar surface is an angled surface; the angled surface is configured to be at an angle between 1 degree and 15 degrees relative to a horizontal plane, the horizontal plane being perpendicular to the longitudinal direction of the body portion; and / or the bonding surface is configured to be ultrasonically welded to the workpiece using torsional vibration.

[0010] According to another exemplary embodiment of the present invention, a power module is provided. The power module includes a semiconductor element. The power module further includes a carrier for supporting the semiconductor element. The power module further includes at least one conductive pin ultrasonically welded to the carrier. The conductive pin includes a body portion and a pin head located at one end of the body portion. The pin head defines a bonding surface welded to the carrier. Before being ultrasonically welded to the carrier, the bonding surface of the conductive pin includes at least one of the following: (i) a non-planar surface and (ii) a hole defined in a central region of the bonding surface.

[0011] According to other embodiments of the present invention, the power module described in the preceding paragraph may have any one or more of the following features: the bonding surface includes a non-planar surface before being ultrasonically welded to the carrier; the non-planar surface is a curved surface; the curved surface has a radius of curvature between 2 mm and 100 mm; the bonding surface includes a hole defined in the central region of the bonding surface before being ultrasonically welded to the carrier; the hole has a maximum depth between 10 μm and 1000 μm; the hole extends through the entire length of the body portion of the conductive pin; the hole is a tapered hole; the hole is a curved hole; the curved hole has a radius of curvature between 2 mm and 100 mm; the hole is a cylindrical hole; the non-planar surface is an angled surface; the angled surface is configured to be at an angle between 1 degree and 15 degrees relative to the horizontal plane, where the horizontal plane is perpendicular to the longitudinal direction of the body portion; and / or the bonding surface is configured to be ultrasonically welded to the workpiece using torsional vibration.

[0012] According to yet another exemplary embodiment of the present invention, an ultrasonic welding system is provided that is configured to weld a conductive pin to a workpiece. The ultrasonic welding system includes an ultrasonic electrode configured to ultrasonically weld the conductive pin to the workpiece during the welding process. The ultrasonic welding system further includes a control system configured to control the welding process, which includes bonding the bonding surface of the conductive pin to the workpiece, and the bonding surface includes at least one of the following: (i) a non-planar surface and (ii) a hole defined in the central region of the bonding surface.

[0013] According to other embodiments of the present invention, the ultrasonic welding system described in the preceding paragraph may have any one or more of the following features: the control system is configured to apply process parameters based on the bonding surface during the welding process; the bonding surface includes a non-planar surface, and the control system is configured to apply process parameters based on the non-planar surface during the welding process; the bonding surface includes a hole defined in the central region, and the control system is configured to apply process parameters based on the hole defined in the central region during the welding process; the bonding surface includes a non-planar surface and a hole defined in the central region of the non-planar surface, and the control system is configured to apply process parameters based on the non-planar surface and the hole defined in the central region of the non-planar surface during the welding process; the process parameters include at least one of bond force, bond energy, and bond time; and / or the welding process employs torsional vibration applied by the ultrasonic electrode. Additionally, it should be understood that any one or more of the features of the conductive pin and / or power module described in the preceding paragraphs of the present invention summary can be used in combination with the ultrasonic welding system.

[0014] According to yet another exemplary embodiment of the present invention, a method for ultrasonically welding a conductive pin to a workpiece is provided. The method includes the following steps: (a) providing a workpiece; and (b) ultrasonically welding the conductive pin to the workpiece, the conductive pin including a body portion; and a pin head located at one end of the body portion, the pin head defining a bonding surface configured to be ultrasonically welded to the workpiece, the bonding surface including at least one of the following: (i) a non-planar surface and (ii) a hole defined in a central region of the bonding surface.

[0015] According to other embodiments of the present invention, the method described in the preceding paragraphs may have any one or more of the following features: Step (b) includes using a control system to apply process parameters based on the bonding surface during ultrasonic welding; Step (b) includes using a control system to apply process parameters based on the non-planar surface during ultrasonic welding; Step (b) includes using a control system to apply process parameters based on the hole defined in the central region during ultrasonic welding; Step (b) includes using a control system to apply process parameters based on the non-planar surface and the hole defined in the central region of the non-planar surface during ultrasonic welding; Step (b) includes using a control system to apply process parameters during ultrasonic welding, the process parameters including at least one of bonding force, bonding energy, and bonding time; and / or Step (b) includes using a control system to apply process parameters during ultrasonic welding, and the ultrasonic welding employs torsional vibration applied by an ultrasonic electrode configured to ultrasonically weld the conductive pin to the workpiece. In addition, it should be understood that any one or more features of the conductive pin and / or power module described in the preceding paragraphs of the present invention content can be used in combination with the ultrasonic welding system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention is best understood when read in conjunction with the following detailed description with reference to the accompanying drawings. It should be emphasized that, according to convention, the various features in the drawings are not drawn to scale. Instead, for clarity, the dimensions of the various features are arbitrarily enlarged or reduced. The accompanying drawings include the following schematic diagrams:

[0017] Figure 1 is a side view block diagram of an ultrasonic welding system according to an exemplary embodiment of the present invention;

[0018] Figures 2A to 2F is a cross-sectional side view of a conductive pin (or portions thereof) according to various exemplary embodiments of the present invention;

[0019] Figures 3A to 3F is a cross-sectional side view of a conductive pin (or portions thereof) according to various exemplary embodiments of the present invention;

[0020] Figures 4A to 4D is a cross-sectional side view of a conductive pin (or portions thereof) according to various exemplary embodiments of the present invention;

[0021] Figure 5 is a side view block diagram of a power module according to an example of the present invention; and

[0022] Figure 6 is a flow chart of a method for ultrasonically welding conductive pins to a workpiece according to various exemplary embodiments of the present invention. DETAILED DESCRIPTION

[0023] Certain exemplary embodiments of the present invention relate to an ultrasonic welding system and, for example, a method of using an ultrasonic welding system related to conductive pins and / or power modules. Such an ultrasonic welding system can be used to weld (and / or bond) conductive pins (and / or copper terminals or other conductive terminals) to a workpiece (such as a substrate, carrier, etc.).

[0024] An ultrasonic welding system typically includes an ultrasonic welding transducer. Such a transducer can be designed to operate, for example, in a linear mode / motion or in a torsional mode / motion. For example, a linear ultrasonic transducer carries an ultrasonic welding electrode, and during operation, the contact portion of the ultrasonic welding electrode will undergo ultrasonic vibration in a substantially linear motion manner. In contrast, a torsional ultrasonic transducer carries an ultrasonic welding electrode, and during operation, the concave portion of the ultrasonic welding electrode will undergo ultrasonic vibration in a substantially rotational / torsional motion manner.

[0025] A particular ultrasonic welding system (such as a pin welder) can be used to weld / bond conductive pins to a workpiece. The traditional bonding surfaces (i.e., welding sides) of conductive pins for ultrasonic welding are almost all substantially flat or planar surfaces with varying surface roughness. Traditional conductive pins typically have a bottom side (welding side) with a substantially flat profile. In traditional torsional pin welding, the center point of the bonding surface of the conductive pin (i.e., the point that coincides with the rotational axis of the conductive pin and / or the ultrasonic welding electrode) may not receive sufficient bonding energy. Therefore, stress concentration (such as due to non-uniform bonding or insufficient bonding), delamination, fatigue points, poor conductivity, or other bonding problems may occur at the bonding interface between the conductive pin and the workpiece (such as a carrier). Certain aspects of the present invention address these problems associated with the traditional bonding surfaces of conductive pins.

[0026] According to a particular aspect of the present invention, the pin head of a conductive pin can have a non-planar bonding surface. The bonding surface can be considered to have a non-planar profile. Examples of non-planar profiles include an inclined profile, an angled profile, a curved profile, and other profiles described herein and / or within the scope of the present invention. The non-planar bonding surface of the pin head can significantly improve the welded conductive pin connection.

[0027] According to a particular aspect of the present invention, the pin head of a conductive pin can have a bonding surface that includes a hole defined in a central region of the bonding surface.

[0028] Referring now to the drawings, Figure 1 illustrates an ultrasonic welding system 100. The ultrasonic welding system 100 is configured to ultrasonically weld conductive pins (e.g., conductive pins 108, 208, 308, 408 in Figure 1 , Figures 2A to 2F , Figures 3A to 3F and Figures 4A to 4D respectively) to a workpiece (e.g., workpieces 102a1, 102a2, 102a3, carriers, etc.). The ultrasonic welding system 100 includes an input workpiece supply 102 for providing the workpiece 102a1, wherein the input workpiece supply 102 is configured to carry a plurality of workpieces 102a1 (e.g., the workpiece supply 102 can be a magazine handler for carrying a plurality of workpieces 102a1 or other supply structures suitable for specific workpiece applications, etc.). Exemplary workpieces 102a1 carried by the input workpiece supply 102 include semiconductor elements, power modules, carriers, components of power modules, lead frames, battery modules, etc. The workpiece 102a1 is provided from the input workpiece supply 102 to the material handling system 104 (by any required transfer components that may be included in the material handling system 104, such as gripper components).

[0029] The material handling system 104 moves the workpiece 102a1 to a support structure 106 (e.g., using a conveyor component, using a gripper component, etc.). The support structure 106 supports the workpiece during the welding operation (now labeled as the clamped workpiece 102a2 when clamped against the support structure 106 using a workpiece fixture). After the welding operation (described below with respect to the welding head assembly 112), the now welded workpiece 102a3 (e.g., using a conveyor component, using a gripper component, etc.) is moved from the portion of the material handling system 104 downstream of the support structure 106 to an output workpiece supply 110. The output workpiece supply 110 is configured to receive the welded workpiece 102a3 after being processed by the welding head assembly 112. The output workpiece supply 110 can be a magazine handler for carrying a plurality of welded workpieces 102a3, or can be other supply structures suitable for specific workpiece applications.

[0030] The ultrasonic welding system 100 includes a welding head assembly 112. The welding head assembly 112 includes an ultrasonic transducer 112b that carries an ultrasonic electrode 116 and is movable along a plurality of substantially horizontal axes. In Figure 1 the example shown, the welding head assembly 112 is configured to move along the x-axis and y-axis of the ultrasonic welding system 100. In Figure 1 the example shown, the welding head assembly 112 is further configured to move along the z-axis of the ultrasonic welding system 100 and rotate about the θ-axis of the ultrasonic welding system 100 ( move along the axes). Not every application requires all of these axes of motion. Using the axes of motion of the tip assembly 112, the ultrasonic electrode 116 can be moved to an appropriate welding position relative to the clamped workpiece 102a2. A camera 114 is also provided (the camera is optionally carried by the tip assembly 112 or can be carried by other components of the ultrasonic welding system 100) for imaging operations related to alignment between the ultrasonic electrode 116 and the clamped workpiece 102a2, alignment of the components of the clamped workpiece 102a2 itself, optical inspection of the welded portion after the welding operation, etc.

[0031] The ultrasonic electrode 116 is shown coupled to a vacuum 118 (such as a vacuum source). The ultrasonic electrode 116 can define a vacuum channel (not shown) that is coupled to the vacuum via a conduit 118a for receiving the conductive pins 108 from a conductive pin supply (not shown).

[0032] The ultrasonic electrode 116 is shown carrying the conductive pins 108 prior to the ultrasonic welding operation. The body portion 108a of the conductive pin 108 is shown disposed together with the ultrasonic electrode 116. As will be understood by those skilled in the art, the conductive pins 108 (and other conductive pins illustrated and / or described herein) are typically cylindrically symmetric and / or have a circular cross-section along their length. The pin head 108b (located at the distal end of the body portion 108a) is shown disposed below the ultrasonic electrode 116. Details of the conductive pin 108 and the pin head 108b are as Figures 2A to 2F , Figures 3A to 3F and Figures 4A to 4D shown.

[0033] The ultrasonic welding system 100 is shown including a control system 120. The control system 120 is configured to control the welding process (e.g., welding the conductive pins 108 to the workpiece 102a1 / 102a2 / 102a3). The welding process includes ultrasonic welding the bonding surface of the conductive pin to the workpiece, the bonding surface including at least one of the following: (i) a non-planar surface and (ii) a hole defined in a central region of the bonding surface. In a particular embodiment, the control system 120 is configured to apply process parameters based on the bonding surface during the welding process.

[0034] In one example, when the bonding surface includes a non-planar surface, the control system can be configured to apply process parameters based on the non-planar surface during the welding process.

[0035] In another example, when the bonding surface includes a hole defined in a central region of the bonding surface, the control system can be configured to apply process parameters based on the hole defined in the central region during the welding process.

[0036] In another example, when the bonding surface includes a non-planar surface and a hole defined in a central region of the non-planar surface, the control system can be configured to apply process parameters based on the non-planar surface and the hole defined in the central region of the non-planar surface during the welding process.

[0037] The process parameters can include one or more of a bonding force, a bonding energy, and a bonding time. The welding process can employ torsional vibrations applied by an ultrasonic electrode.

[0038] An ultrasonic welding system 100 (or other systems within the scope of the present invention) can be used to weld various types of workpieces. Exemplary workpieces include power modules, lead frames, and battery modules.

[0039] It will be understood that the term "power module" (sometimes also referred to as a power electronics module) as used herein refers to a module that houses one or more power components (such as power semiconductor elements or devices). Exemplary power components include MOSFETs, IGBTs, BJTs, thyristors, GTPs, and JFETs. Such a module typically also includes a carrier (such as a power electronics substrate) for carrying the power components. Compared to discrete power semiconductors, power modules tend to provide higher power density. As will be understood by those skilled in the art, the power modules shown in the figures have been simplified for ease of illustration.

[0040] According to the present invention, various types of ultrasonic motion can be applied to a conductor (such as a conductive pin, a signal connector, a conductive terminal, a power terminal, etc.). For example, the ultrasonic electrode can be configured to weld the conductor to the workpiece using at least one of linear ultrasonic motion and torsional ultrasonic motion.

[0041] Certain workpieces among those workpieces are configured to receive conductive pins. As used herein, the term "conductive pin" is a conductive structure intended to be welded to a workpiece. The conductive pin can have a free end (after being welded to the workpiece), and the body portion of the conductive pin can extend substantially vertically from the "welded" end to the free end. The cross-section of the conductive pin can be circular, square, rectangular, or have any desired cross-section. The term "conductive pin" should also be understood to include a conductive socket or sleeve (such as having a tubular shape, such as a rivet), where the conductive socket / sleeve is ultrasonically welded to the workpiece and is configured to receive another conductive element. According to a particular exemplary embodiment, the ultrasonic welding system 100 can include a conductive pin supply configured to provide a plurality of conductive pins for welding using the ultrasonic electrode 116. Example configurations for the conductive pin supply include: a grid arrangement (including columns and rows of conductive pins oriented for easy pick-up), a bowl feeder, a hopper, a spool, etc. Alternative configurations are conceivable. Such a conductive pin supply can be configured to operate with a buffer system so that the pins are fed through an accumulation zone and are ready for pick-up for welding.

[0042] Exemplary embodiments of conductive pin 108 are illustrated as conductive pin 208, conductive pin 308, and conductive pin 408, respectively, in Figures 2A to 2F , Figures 3A to 3F and Figures 4A to 4D .

[0043] Specifically referring to Figure 2A , conductive pin 208 is shown in the figure. Conductive pin 208 includes a body portion 208a. Conductive pin 208 further includes a pin head 208b at the distal end of the body portion 208a (i.e., along the z-axis). The pin head 208b defines a bonding surface 208c that is configured to be ultrasonically welded to a workpiece. The bonding surface 208c includes at least one of the following: (i) a non-planar surface and (ii) a hole defined in the central region of the bonding surface 208c. The longitudinal direction LD and the horizontal plane HP of the body portion 208a are illustrated; the horizontal plane HP is perpendicular to the longitudinal direction LD of the body portion 208a. An example range of the total length (or height) of the conductive pin 208 (or any other conductive pin illustrated and / or described herein) is: 1 mm to 100 mm; and 3 mm to 30 mm. Other ranges are also conceivable.

[0044] Figures 2B to 2F Various embodiments of conductive pin 208 are illustrated, including pin heads 208b1, 208b2, 208b3, 208b4, and 208b5, respectively. Throughout Figures 2B to 2F , each respective pin head is illustrated as having a width of W 1 and a curved surface (of the bonding surface 208c) with a radius of curvature of ρ 1 . The example range of W 1 includes: 0.5 mm to 10 mm; and 1 mm to 4 mm. The example range of the radius of curvature ρ 1 includes: 1 mm to 1000 mm; and 2 mm to 100 mm. Other ranges are also conceivable.

[0045] Specifically referring to Figure 2B , pin head 208b1 is illustrated as including a bonding surface 208c1. The bonding surface 208c1 includes a non-planar surface 208c1a; specifically, the non-planar surface 208c1a is a curved surface. The radius of curvature of the non-planar surface 208c1a is ρ 1 .

[0046] Now referring to Figure 2C, the pin header 208b2 is shown to include a bonding surface 208c2. The bonding surface 208c2 includes a non-planar surface 208c2a; specifically, the non-planar surface 208c2a is a curved surface. The bonding surface 208c2 further includes a hole 208c2b defined in a central region of the bonding surface 208c2. Specifically, the hole 208c2b is an angled hole 208c2b. The hole 208c2b is shown as a tapered hole with a width of W 2 , an angle of θ 1 , and a maximum depth of d 1 . The width W 2 has an example range of 0.1 mm to 3 mm. The angle θ 1 has an example range of 60 to 170 degrees; and 90 to 120 degrees. The d 1 has an example range including: 10 μm to 1000 μm; and 1 μm to 3000 μm. Other ranges are also conceivable.

[0047] Now referring to Figure 2D , the pin header 208b3 is shown to include a bonding surface 208c3. The bonding surface 208c3 includes a non-planar surface 208c3a; specifically, the non-planar surface 208c3a is a curved surface. The bonding surface 208c3 further includes a hole 208c3b defined in a central region of the bonding surface 208c3. Specifically, the hole 208c3b is a curved hole. The hole 208c3b is shown as a spherical cap hole or a domed hole with a width of W 2 , a radius of curvature of ρ 2 , and a maximum depth of d 2 . The width W 2 has an example range of 0.1 mm to 3 mm. The radius of curvature ρ 2 has an example range including 2 mm to 100 mm; and 1 mm to 1000 mm. The maximum depth d 2 has an example range including 10 μm to 1000 μm; and 1 μm to 3000 μm. Other ranges are also conceivable.

[0048] Now referring to Figure 2E , the pin header 208b4 is shown to include a bonding surface 208c4. The bonding surface 208c4 includes a non-planar surface 208c4a; specifically, the non-planar surface 208c4a is a curved surface. The bonding surface 208c4 further includes a hole 208c4b defined in a central region of the bonding surface 208c4. Specifically, the hole 208c4b is a cylindrical hole. The hole 208c4b is shown as having a width of W 2 , and a maximum depth of d 3 . The width W 2 has an example range of 0.1 mm to 3 mm. The maximum depth d 3Example ranges include: 10 μm to 1000 μm; and 1 μm to 3000 μm. Other ranges are also conceivable. It should be understood that the hole 208c4b can be implemented as a rectangular hole, an oval hole, and holes of other geometries.

[0049] Now referring to Figure 2F , the pinhead 208b5 is illustrated as including a bonding surface 208c5. The bonding surface 208c5 includes a non-planar surface 208c5a; specifically, the non-planar surface 208c5a is a curved surface. The bonding surface 208c5 also includes a hole 208c5b defined in a central region of the bonding surface 208c5. Specifically, the hole 208c5b is a cylindrical hole. The hole 208c5 is illustrated as having a width of W 2 , and extending through the length (e.g., the full length) of the body portion 208a. The width W 2 has an example range of 0.1 mm to 3 mm. Other ranges are also conceivable. It should be understood that the hole 208c5b can be implemented as a rectangular hole, an oval hole, a pyramidal hole, and holes of other geometries.

[0050] Now referring to Figure 3A , a conductive pin 308 is shown in the figure. The conductive pin 308 includes a body portion 308a. The conductive pin 308 also includes a pinhead 308b at the distal end of the body portion 308a (i.e., along the z-axis). The pinhead 308b defines a bonding surface 308c, which is configured to be ultrasonically welded to a workpiece. The bonding surface 308c includes at least one of the following: (i) a non-planar surface and (ii) a hole defined in a central region of the bonding surface 308c. The longitudinal direction LD of the body portion 308a and the horizontal plane HP are illustrated; the horizontal plane HP is perpendicular to the longitudinal direction LD of the body portion 308a.

[0051] Figures 3B to 3F Various embodiments of the conductive pin 308 are illustrated, including pinheads 308b1, 308b2, 308b3, 308b4, and 308b5, respectively. Throughout Figures 3B to 3F , each corresponding pinhead is illustrated as having a width of W 1 and an angled surface of the bonding surface with an angle of θ 2 . The angled surface is configured to be at an angle of θ 2 relative to the horizontal plane HP. The W 1 has example ranges including: 0.5 mm to 10 mm; and 1 mm to 4 mm. The angle θ 2 has example ranges including: 1 to 15 degrees; and 1 to 45 degrees. Other ranges are also conceivable.

[0052] Specifically referring to Figure 3B, the pinhead 308b1 is illustrated as including a bonding surface 308c1. The bonding surface 308c1 includes a non-planar surface 308c1a; specifically, the non-planar surface 308c1a is an angled surface. The angle of the non-planar surface 308c1a is θ 2 .

[0053] Now referring to Figure 3C , the pinhead 308b2 is illustrated as including a bonding surface 308c2. The bonding surface 308c2 includes a non-planar surface 308c2a; specifically, the non-planar surface 308c2a is an angled surface. The bonding surface 308c2 also includes a hole 308c2b defined in the central region of the bonding surface 308c2. Specifically, the hole 308c2b is an angled hole. The hole 308c2b is illustrated as a tapered hole, and its angle is θ 1 , with a width of W 2 , and a maximum depth of d 1 . The angle θ 1 has example ranges of: 60 to 170 degrees; and 90 to 120 degrees. The width W 2 has example ranges of 0.1 mm to 3 mm. The maximum depth d 1 has example ranges including: 10 μm to 1000 μm; and 1 μm to 3000 μm. Other ranges are also conceivable.

[0054] Now referring to Figure 3D , the pinhead 308b3 is illustrated as including a bonding surface 308c3. The bonding surface 308c3 includes a non-planar surface 308c3a; specifically, the non-planar surface 308c3a is an angled surface. The bonding surface 308c3 also includes a hole 308c3b defined in the central region of the bonding surface 308c3. Specifically, the hole 308c3b is a curved hole. The hole 308c3b is illustrated as a spherical cap hole or a domed hole, and its radius of curvature is ρ 2 , with a width of W 2 , and a maximum depth of d 2 . The radius of curvature ρ 2 has example ranges including: 2 mm to 100 mm; and 1 mm to 1000 mm. The width W 2 has example ranges of 0.1 mm to 3 mm. The maximum depth d 2 has example ranges including: 10 μm to 1000 μm; and 1 μm to 3000 μm. Other ranges are also conceivable.

[0055] Now referring to Figure 3E, the pinhead 308b4 is illustrated as including a bonding surface 308c4. The bonding surface 308c4 includes a non-planar surface 308c4a; specifically, the non-planar surface 308c4a is an angled surface. The bonding surface 308c4 further includes a hole 308c4b defined in a central region of the bonding surface 308c4. Specifically, the hole 308c4b is a cylindrical hole. The hole 308c4b is illustrated as having a width of W 2 , and a depth of d 3 . The width W 2 has an exemplary range of 0.1 mm to 3 mm. The depth d 3 has exemplary ranges that include: 10 μm to 1000 μm; and between 1 μm and 3000 μm. Other ranges are also conceivable. It should be understood that the hole 308c4b can be implemented as a rectangular hole, an oval hole, and holes of other geometries.

[0056] Now referring Figure 3F , the pinhead 308b5 is illustrated as including a bonding surface 308c5. The bonding surface 308c5 includes a non-planar surface 308c5a; specifically, the non-planar surface 308c5a is an angled surface. The bonding surface 308c5 further includes a hole 308c5b defined in a central region of the bonding surface 308c5. Specifically, the hole 308c5b is a cylindrical hole. The hole 308c5b is illustrated as having a width of W 2 , and extending through the length (e.g., full length) of the body portion 308a. The width W 2 has an exemplary range of 0.1 mm to 3 mm. Other ranges are also conceivable. It should be understood that the hole 308c5b can be implemented as a rectangular hole, an oval hole, a pyramidal hole, and holes of other geometries.

[0057] Now referring Figure 4A , a conductive pin 408 is shown in the figure. The conductive pin 408 includes a body portion 408a. The conductive pin 408 further includes a pinhead 408b located at a distal end of the body portion 408a (i.e., along the z-axis). The pinhead 408b defines a bonding surface 408c that is configured to be ultrasonically welded to a workpiece. The bonding surface 408c includes at least one of the following: (i) a non-planar surface and (ii) a hole defined in a central region of the bonding surface 408c. The longitudinal direction LD of the body portion 408a and a horizontal plane HP are illustrated; the horizontal plane HP is perpendicular to the longitudinal direction LD of the body portion 408a.

[0058] Figures 4B to 4D Various embodiments of the conductive pin 408 are illustrated, including pinheads 408b1, 408b2, and 408b3, respectively. Throughout Figures 4B to 4D , each respective pinhead is illustrated as having a width of W 1 . The width W1 Example ranges include: 0.5 mm to 10 mm; and 1 mm to 4 mm. Other ranges are also conceivable.

[0059] Now referring to Figure 4B , the pin header 408b1 is illustrated as including a bonding surface 408c1. The bonding surface 408c1 includes a hole 408c1a defined in a central region of the bonding surface 408c1. Specifically, the hole 408c1a is an angled hole. The hole 408c1a is illustrated as a tapered hole with an angle of θ 1 , having a width of W 2 , and a maximum depth of d 1 . The angle θ 1 Example ranges are: 60 to 170 degrees; and 90 to 120 degrees. The width W 2 Example ranges are from 0.1 mm to 3 mm. The maximum depth d 1 Example ranges include: 10 μm to 1000 μm; and between 1 μm and 3000 μm. Other ranges are also conceivable.

[0060] Now referring to Figure 4C , the pin header 408b2 is illustrated as including a bonding surface 408c2. The bonding surface 408c2 includes a hole 408c2a defined in a central region of the bonding surface 408c2. Specifically, the hole 408c2a is a curved hole. The hole 408c2a is illustrated as a spherical cap hole or a dome-shaped hole with a radius of curvature of ρ 2 , having a width of W 2 , and a maximum depth of d 2 . The radius of curvature ρ 2 Example ranges include: 2 mm to 100 mm; and 1 mm to 1000 mm. The width W 2 Example ranges are from 0.1 mm to 3 mm. The maximum depth d 2 Example ranges include: 10 μm to 1000 μm; and between 1 μm and 3000 μm. Other ranges are also conceivable.

[0061] Now referring to Figure 4D , the pin header 408b3 is illustrated as including a bonding surface 408c3. The bonding surface 408c3 includes a hole 408c3a defined in a central region of the bonding surface 408c3. Specifically, the hole 408c3a is a cylindrical hole. The hole 408c3a is illustrated as having a width of W 2 , and a maximum depth of d 3 . The width W 2 Example ranges are from 0.1 mm to 3 mm. The maximum depth d 3Exemplary ranges include: 10 μm to 1000 μm; and 1 μm to 3000 μm. Other ranges are also contemplated. It should be understood that the hole 408c3a can be implemented as a rectangular hole, a pyramidal hole, an oval hole, and holes of other geometric shapes.

[0062] through Figures 2C to 2F , Figures 3C to 3F and Figures 4B to 4D , various holes are illustrated and described in geometric shapes, such as tapered holes, spherical cap / dome-shaped holes, cylindrical holes, etc. It should be understood that these descriptions are exemplary in nature and are not intended to limit the scope of the embodiments. For example, Figure 2C , Figure 3C and Figure 4B the "tapered" holes in Figure 2D , Figure 3D and Figure 4C are intended to cover similar holes, such as frustum-shaped holes, asymmetrically tapered-like holes, etc. In another example,

[0063] It should be understood that the conductive pins described herein can be formed of copper material. Although copper (or copper alloy) conductive pins (and terminals and buses) are described herein, it can be understood that the present invention (and associated terminals, buses, and methods) is not limited to copper material. The conductive pins can be made of other conductive materials (such as aluminum).

[0064] Now referring to Figure 5 , a power module 122 (a specific type of workpiece) is shown in the figure. The power module 122 includes a semiconductor element 102an. As used herein, the term "semiconductor element" is intended to mean any structure that includes (or is configured to include in a later step) a semiconductor chip or wafer (e.g., a power semiconductor element). Exemplary semiconductor elements include substrates (e.g., lead frames, PCBs, carriers, etc.), substrates that carry one or more semiconductor wafers, bare semiconductor wafers, packaged semiconductor devices, flip-chip semiconductor devices, wafers embedded in substrates, semiconductor wafer stacks, etc. In addition, the semiconductor element can include elements configured to be bonded or otherwise included in a semiconductor package (e.g., spacers, substrates, etc. bonded in a stacked wafer configuration).

[0065] The power module 122 further includes a carrier 124 for supporting the semiconductor element 102an. The power module 122 further includes at least one conductive pin 108 that is ultrasonically welded to the carrier 124 (e.g., Figures 2A to 2F the conductive pin 208 of Figures 3A to 3F the conductive pin 308 of Figures 4A to 4Dof the conductive pin 408). The conductive pin 108 includes a body portion 108a and a pin head 108b located at one end of the body portion 108a. Before ultrasonic welding, the pin head 108b includes a bonding surface configured to be ultrasonically welded to a workpiece (such as the carrier 124). The bonding surface of the conductive pin 108, before being ultrasonically welded to the carrier, includes at least one of the following: (i) a non-planar surface and (ii) a hole defined in a central region of the bonding surface.

[0066] In Figure 5 it, the conductive pin 108 is illustrated as being bonded to the carrier 124. It should be understood that Figure 5 illustrated is a very simplified form of the power module 122; for simplicity, some details are omitted.

[0067] Figure 6 is a flowchart illustrating a method of ultrasonically welding a conductive pin to a workpiece. As will be understood by those skilled in the art, specific steps included in the flowchart may be omitted; specific additional steps may be added; and the order of the steps may vary from the illustrated order, all within the scope of the present invention.

[0068] In step 600, a workpiece is provided (e.g., Figure 1 the workpiece 102a1 / 102a2 / 102a3 in Figure 5 the carrier 124 in

[0069] In step 602, a conductive pin (e.g., Figure 1 the conductive pin 108 in Figures 2A to 2F the conductive pin 208 in Figures 3A to 3F the conductive pin 308 in Figures 4A to 4D the conductive pin 408 in

[0070] In a particular embodiment, step 602 includes applying process parameters based on the bonding surface using a control system (e.g., Figure 1 the control system 120 in

[0071] In a particular embodiment, step 602 includes applying process parameters based on the non-planar surface using a control system (e.g., Figure 1 the control system 120 in

[0072] In a particular embodiment, step 602 includes using a control system (e.g.,Figure 1 The control system 120) in

[0073] In a particular embodiment, step 602 includes using a control system (such as Figure 1 the control system 120) in

[0074] In a particular embodiment, step 602 includes using a control system (such as Figure 1 the control system 120) in

[0075] In a particular embodiment, step 602 includes using a control system (such as Figure 1 the control system 120) in

[0076] Although the invention has been illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Instead, various modifications may be made in the scope and equivalents of the claims without departing from the invention.

Claims

1. A conductive pin for ultrasonic welding, the conductive pin comprising: The main body part; as well as A pin head is located at one end of the body portion, the pin head defining a bonding surface, the bonding surface being configured to be ultrasonically welded to a workpiece, the bonding surface comprising at least one of: (i) a non-planar surface and (ii) a hole defined in a central region of the bonding surface. 2 . The conductive pin of claim 1 , wherein the bonding surface comprises a non-planar surface. The conductive pin according to claim 2 , wherein the non-planar surface is a curved surface. The conductive pin according to claim 3 , wherein the curved surface has a radius of curvature between 2 mm and 100 mm. 5 . The conductive pin of claim 3 , wherein the bonding surface further comprises a hole defined in a central region of the bonding surface. 6 . The conductive pin of claim 5 , wherein the hole has a maximum depth between 10 μm and 1000 μm.

7. The current conducting pin of claim 5, wherein the hole extends through the entire length of the body portion of the current conducting pin. The conductive pin according to claim 5 , wherein the hole is a tapered hole.

9. The conductive pin according to claim 5, wherein the hole is a curved hole. 10 . The conductive pin of claim 9 , wherein the curved hole has a radius of curvature between 2 mm and 100 mm. The conductive pin according to claim 5 , wherein the hole is a cylindrical hole.

12. The current conducting pin of claim 2, wherein the non-planar surface is an angled surface.

13. The current conducting pin of claim 12, wherein the angled surface is configured at an angle between 1 degree and 15 degrees relative to a horizontal plane, the horizontal plane being perpendicular to a longitudinal direction of the body portion.

14. The conductive pin of claim 12, wherein the bonding surface further comprises a hole defined in a central region of the bonding surface. 15 . The current conducting pin of claim 14 , wherein the hole has a maximum depth between 10 μm and 1000 μm.

16. The current conducting pin of claim 14, wherein the hole extends through the entire length of the body portion of the current conducting pin. The current conducting pin according to claim 14 , wherein the hole is a tapered hole. The conductive pin according to claim 14 , wherein the hole is a curved hole. The conductive pin according to claim 14 , wherein the hole is a cylindrical hole.

20. The current conducting pin of claim 1, wherein the bonding surface includes a hole defined in a central region of the bonding surface. The current conducting pin according to claim 20 , wherein the hole is a tapered hole.

22. The conductive pin according to claim 20, wherein the hole is a curved hole.

23. The current conducting pin of claim 22, wherein the curved hole has a radius of curvature between 2 mm and 100 mm. The conductive pin according to claim 20 , wherein the hole is a cylindrical hole.

25. The conductive pin of claim 20, wherein the hole has a maximum depth between 10 μm and 1000 μm.

26. The current conducting pin of claim 1, wherein the bonding surface is configured to be ultrasonically welded to a workpiece using torsional vibration.

27. A power module comprising: Semiconductor components; A carrier for supporting the semiconductor element; as well as at least one conductive pin ultrasonically welded to the carrier, the conductive pin comprising a body portion and a pin head at one end of the body portion, the pin head defining a bonding surface welded to the carrier, The bonding surface of the conductive pin, before being ultrasonically welded to the carrier, includes at least one of: (i) a non-planar surface and (ii) a hole defined in a central region of the bonding surface.

28. The power module of claim 27, wherein the bonding surface comprises a non-planar surface prior to being ultrasonically welded to the carrier.

29. The power module of claim 28, wherein the non-planar surface is a curved surface.

30. The power module of claim 29, wherein the curved surface has a radius of curvature between 2 mm and 100 mm.

31. The power module of claim 28, wherein the bonding surface further comprises a hole defined in a central region of the bonding surface prior to being ultrasonically welded to the carrier.

32. The power module of claim 31, wherein the holes have a maximum depth between 10 μm and 1000 μm.

33. The power module of claim 31, wherein the hole extends through the entire length of the body portion of the conductive pin.

34. The power module of claim 31 , wherein the hole is a tapered hole.

35. The power module of claim 31 , wherein the hole is a curved hole.

36. The power module of claim 35, wherein the curved hole has a radius of curvature between 2 mm and 100 mm.

37. The power module of claim 31, wherein the hole is a cylindrical hole.

38. The power module of claim 28, wherein the non-planar surface is an angled surface.

39. The power module of claim 38, wherein the angled surface is configured at an angle between 1 degree and 15 degrees relative to a horizontal plane, the horizontal plane being perpendicular to a longitudinal direction of the body portion.

40. The power module of claim 38, wherein the bonding surface further comprises a hole defined in a central region of the bonding surface prior to being ultrasonically welded to the carrier.

41. The power module of claim 40, wherein the holes have a maximum depth between 10 μm and 1000 μm.

42. The power module of claim 40, wherein the hole extends through the entire length of the body portion of the conductive pin.

43. The power module of claim 40, wherein the hole is a tapered hole.

44. The power module of claim 40, wherein the hole is a curved hole.

45. The power module of claim 40, wherein the hole is a cylindrical hole.

46. ​​The power module of claim 27, wherein the bonding surface includes a hole defined in a central region of the bonding surface prior to being ultrasonically welded to the carrier.

47. The power module of claim 46, wherein the hole is a tapered hole.

48. The power module of claim 46, wherein the hole is a curved hole.

49. The power module of claim 48, wherein the curved aperture defines a radius of curvature between 2 mm and 100 mm.

50. The power module of claim 46, wherein the hole is a cylindrical hole.

51. The power module of claim 46, wherein the holes have a maximum depth between 10 μm and 1000 μm.

52. The power module of claim 27, wherein the bonding surface is configured to be ultrasonically welded to a workpiece using torsional vibration.

53. An ultrasonic welding system configured to weld a conductive pin to a workpiece, the ultrasonic welding system comprising: a sonotrode configured to ultrasonically weld the conductive pin to the workpiece during a welding process; as well as A control system configured to control the welding process, the welding process comprising bonding a bonding surface of the conductive pin to the workpiece, the bonding surface comprising at least one of: (i) a non-planar surface and (ii) a hole defined in a central region of the bonding surface.

54. The ultrasonic welding system of claim 53, wherein the control system is configured to apply process parameters based on the bonding surfaces during the welding process.

55. The ultrasonic welding system of claim 53, wherein the bonding surface comprises a non-planar surface, and the control system is configured to apply process parameters during the welding process based on the non-planar surface.

56. The ultrasonic welding system of claim 53, wherein the bonding surface includes a hole defined in a central region, and the control system is configured to apply process parameters during the welding process based on the hole defined in the central region.

57. The ultrasonic welding system of claim 53, wherein the bonding surface comprises a non-planar surface and a hole defined in a central region of the non-planar surface, and the control system is configured to apply process parameters during the welding process based on the non-planar surface and the hole defined in the central region of the non-planar surface.

58. The ultrasonic welding system of claim 53, wherein the process parameters include at least one of bonding force, bonding energy, and bonding time.

59. The ultrasonic welding system of claim 53, wherein the welding process employs torsional vibrations imparted by the sonotrode.

60. A method for ultrasonically welding a conductive pin to a workpiece, the method comprising the steps of: (a) Providing workpieces; as well as (b) ultrasonically welding the conductive pin to the workpiece, the conductive pin comprising a body portion and a pin head located at one end of the body portion, the pin head defining a bonding surface, the bonding surface being configured to be ultrasonically welded to the workpiece, the bonding surface comprising at least one of: (i) a non-planar surface and (ii) a hole defined in a central region of the bonding surface.

61. The method of claim 60, wherein step (b) comprises using a control system to apply process parameters based on the bonding surfaces during ultrasonic welding.

62. The method of claim 60, wherein step (b) comprises using a control system to apply process parameters based on the non-planar surface during ultrasonic welding.

63. The method of claim 60, wherein step (b) includes using a control system to apply process parameters during ultrasonic welding based on the hole defined in the central region.

64. The method of claim 60, wherein step (b) includes using a control system to apply process parameters during ultrasonic welding based on the non-planar surface and the hole defined in the central region of the non-planar surface.

65. The method of claim 60, wherein step (b) comprises applying process parameters during ultrasonic welding using a control system, wherein the process parameters comprise at least one of bonding force, bonding energy, and bonding time.

66. The method of claim 60, wherein step (b) comprises applying process parameters using a control system during ultrasonic welding, wherein the ultrasonic welding employs torsional vibrations imparted by a sonotrode configured to ultrasonically weld the conductive pin to the workpiece.

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