Conductive pin, power module and ultrasonic welding system

Abstract

The utility model provides a conductive pin for ultrasonic welding. 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. The utility model also provides a power module comprising the conductive pin and an ultrasonic welding system.

Description

[0001] Cross-reference to related applications

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

[0003] This invention relates to ultrasonic welding, and more particularly to an improved system and method for performing ultrasonic welding operations (including conductive pin welding). Background Technology

[0004] Ultrasonic energy is widely used to form interconnects between two or more materials. For example, wire bonding systems (such as ball bonders, wedge bonders, strip bonders, etc.) are used to bond / solder leads or strips of material to bonding / soldering sites. Wire bonding utilizes relatively low energy levels (such as bonding force, ultrasonic energy, etc.). Exemplary wire bonding systems are sold by Kulicke and Soffa Industries, Inc., Fort Washington, Pennsylvania.

[0005] Specific applications involve bonding materials other than leads. Soldering has been considered for these applications. Ultrasonic welding is also a widely used technique. Ultrasonic welding uses an ultrasonic transducer (e.g., a sonotrode) to convert electrical energy into mechanical motion / rubbing (e.g., linear motion / rubbing, torsional motion / rubbing, etc.). However, existing ultrasonic welding technologies and equipment have limited ability to provide solutions that meet market demands in terms of cost, operational efficiency, flexibility, portability, and related factors.

[0006] U.S. Patent No. 10,882,134 (titled "Ultrasonic Welding Systems and Methods of Using the Same"), U.S. Patent No. 11,364,565 (titled "Ultrasonic Welding Systems and Methods of Using the Same"), and U.S. Patent Nos. 11,850,676 and 12,070,814 (titled "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] Nonetheless, improvements are needed in the application of ultrasonic welding, including ultrasonic pin welding (these pins are often soldered and / or press-fit into power modules). Accordingly, it is desirable to improve ultrasonic welding techniques, including ultrasonic pin welding. SUMMARY

[0008] According to an exemplary embodiment of the present application, a conductive pin for ultrasonic / sonic 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 configured to be ultrasonically welded to a workpiece. The bonding surface includes at least one of: (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 application, the conductive pin of the preceding paragraph can 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 pm and 1000 pm; the hole extends through a full 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 have an angle relative to a horizontal plane between 1 degree and 15 degrees, the horizontal plane being perpendicular to a longitudinal direction of the body portion; and / or the bonding surface is configured to be ultrasonically welded to the workpiece using torsional vibrations.

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

[0011] According to other embodiments of the present application, the power module described in the preceding paragraph can have any one or more of the following features: the bonding surface includes a non-planar surface prior to 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 a central region of the bonding surface prior to being ultrasonically welded to the carrier; the hole has a maximum depth between 10 pm and 1000 pm; the hole extends through an 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 have an angle relative to a horizontal plane between 1 degree and 15 degrees, the horizontal plane being perpendicular to a longitudinal direction of the body portion; and / or the bonding surface is configured to be ultrasonically welded to the workpiece using torsional vibrations.

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

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

[0014] According to yet another exemplary embodiment of the present application, a method of ultrasonic welding a conductive pin to a workpiece is provided. The method includes the steps of: (a) providing a workpiece; and (b) ultrasonic welding a conductive pin to the workpiece, the conductive pin including a body portion; and a pin head at one end of the body portion, the pin head defining a bonding surface configured to be ultrasonic welded to the workpiece, the bonding surface including at least one of: (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 application, the method described in the preceding paragraph can have any one or more of the following features: step (b) includes using a control system to apply process parameters during the ultrasonic welding based on the bonding surface; step (b) includes using a control system to apply process parameters during the ultrasonic welding based on the non-planar surface; step (b) includes using a control system to apply process parameters during the ultrasonic welding based on the hole defined in the central region; step (b) includes using a control system to apply process parameters during the ultrasonic welding based on the non-planar surface and the hole defined in the central region of the non-planar surface; step (b) includes using a control system to apply process parameters during the ultrasonic welding, the process parameters including at least one of a bonding force, a bonding energy, and a bonding time; and / or step (b) includes using a control system to apply process parameters during the ultrasonic welding, the ultrasonic welding employing torsional vibrations applied by an ultrasonic horn configured to ultrasonic weld the conductive pin to the workpiece. Furthermore, 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 this Summary can be used in conjunction with the ultrasonic welding system. BRIEF DESCRIPTION OF DRAWINGS

[0016] The present application can best be understood by reading the following detailed description in conjunction with the accompanying drawings, in which:

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

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

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

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

[0021] Figure 5 is a side view block diagram of a power module according to examples of the present utility model; and

[0022] Figure 6 is a flowchart of a method of ultrasonically welding a conductive pin to a workpiece according to various example embodiments of the present utility model. DETAILED DESCRIPTION

[0023] Particular example embodiments of the present utility model relate to ultrasonic welding systems, and methods of using ultrasonic welding systems, for example in connection with conductive pins and / or power modules. Such ultrasonic welding systems can be used to weld conductive pins (and / or copper terminals or other conductive terminals) to workpieces (e.g., substrates, carriers, etc.).

[0024] Ultrasonic welding systems generally include an ultrasonic welding transducer. Such transducers 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 horn, and during operation, a contact portion of the ultrasonic horn will ultrasonically vibrate in a substantially linear motion. In contrast, a torsional ultrasonic transducer carries an ultrasonic horn, and during operation, a concave portion of the ultrasonic horn will ultrasonically vibrate in a substantially rotational / torsional motion.

[0025] Particular ultrasonic welding systems, such as pin welders, can be used to weld / bond conductive pins to workpieces. Conventional bonding surfaces (i.e., weld sides) of conductive pins used in ultrasonic welding are almost always substantially flat or planar surfaces with varying surface roughness. Conventional conductive pins generally have a bottom side (weld side) that has a substantially flat profile. In conventional torsional pin welding, a center point of the bonding surface of the conductive pin (i.e., a point that coincides with the rotational axis of the conductive pin and / or ultrasonic horn) can not be subjected to sufficient bonding energy. As a result, the bonding interface between the conductive pin and the workpiece (e.g., a carrier) can experience stress concentrations (e.g., due to uneven or insufficient bonding), delamination, fatigue points, poor conductivity, or other bonding issues. Particular aspects of the present utility model address these issues associated with conventional bonding surfaces of conductive pins.

[0026] According to particular aspects of the present utility model, a 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 a sloped profile, an angled profile, a curved profile, and other profiles described herein and / or within the scope of the present utility model. The non-planar bonding surface of the pin head can significantly improve the welded conductive pin connection.

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

[0028] Reference is now made to the drawings, Figure 1 An ultrasonic welding system 100 is illustrated. 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-2F , Figures 3A-3F and Figures 4A-4D , respectively) to workpieces (e.g., workpieces 102a1, 102a2, 102a3, carriers, etc.). The ultrasonic welding system 100 includes an input workpiece supply 102 for providing workpieces 102a1, where the input workpiece supply 102 is configured to carry a plurality of workpieces 102a1 (e.g., the input workpiece supply 102 can be a bin handler or other supply structure appropriate to the particular workpiece application, etc., for carrying a plurality of workpieces 102a1). Exemplary workpieces 102a1 carried by the input workpiece supply 102 include semiconductor components, power modules, carriers, components of power modules, lead frames, battery modules, etc. The workpieces 102a1 are provided from the input workpiece supply 102 to a material handling system 104 (via any required transport components that can be included in the material handling system 104, such as gripper assemblies, etc.).

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

[0030] The ultrasonic welding system 100 includes a horn assembly 112. The horn assembly 112 includes an ultrasonic transducer 112b that carries an ultrasonic horn 116, and is movable along a plurality of substantially horizontal axes. In the example shown, Figure 1 The horn assembly 112 is configured to move along the x-axis and the y-axis of the ultrasonic welding system 100. In the example shown, Figure 1In the illustrated example, the horn assembly 112 is also configured to move along a z-axis of the ultrasonic welding system 100 and about a theta-axis of the ultrasonic welding system 100 (θ-axis). Not every application requires all of these axes of motion. Using the axes of motion of the horn assembly 112, the ultrasonic welding horn 116 is able to be moved into the proper welding position relative to the clamped workpiece 102a2. A camera 114 (which is optionally carried by the horn assembly 112, or can be carried by other components of the ultrasonic welding system 100) is also provided for imaging operations related to alignment between the ultrasonic welding horn 116 and the clamped workpiece 102a2, alignment of components of the clamped workpiece 102a2 themselves, optical detection of the weld after the welding operation, and the like.

[0031] The ultrasonic welding horn 116 is illustrated as being coupled with a vacuum 118 (e.g., a vacuum source). The ultrasonic welding horn 116 can define a vacuum channel (not illustrated) that is coupled with the vacuum via a conduit 118a for receiving a conductive pin 108 from a conductive pin supply (not illustrated).

[0032] The ultrasonic welding horn 116 is illustrated as carrying the conductive pin 108 prior to an ultrasonic welding operation. A body portion 108a of the conductive pin 108 is illustrated as being disposed with the ultrasonic welding horn 116. As will be appreciated by those skilled in the art, the conductive pin 108 (as well as other conductive pins illustrated and / or described herein) is generally cylindrical symmetric, and / or has a circular cross-section along its length. A pin head 108b (at a distal end of the body portion 108a) is illustrated as being disposed beneath the ultrasonic welding horn 116. Details of the conductive pin 108 and the pin head 108b are illustrated in Figures 2A-2F 、 Figures 3A-3F and Figures 4A-4D .

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

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

[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 the 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.

[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 the ultrasonic horn.

[0038] Various types of workpieces can be welded using the ultrasonic welding system 100 (or other systems within the scope of the present disclosure). Example workpieces include power modules, lead frames, and battery modules.

[0039] It can be appreciated 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 (e.g., power semiconductor elements or devices). Exemplary power components include MOSFETs, IGBTs, BJTs, thyristors, GTPs, and JFETs. Such modules typically also include a carrier (e.g., a power electronics substrate) for carrying the power components. Power modules tend to provide higher power density as compared to discrete power semiconductors. As will be appreciated by those skilled in the art, the power modules shown in the figures are simplified for ease of illustration.

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

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

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

[0043] With particular reference to Figure 2A , a conductive pin 208 is illustrated. The conductive pin 208 includes a body portion 208a. The conductive pin 208 also includes a pin head 208b at a distal end of the body portion 208a (i.e., along the z-axis). The pin head 208b defines a bonding surface 208c configured to be ultrasonically welded to a workpiece. The bonding surface 208c includes at least one of: (i) a non-planar surface and (ii) a hole defined in a central region of the bonding surface 208c. A longitudinal direction LD of the body portion 208a and a horizontal plane HP are illustrated; the horizontal plane HP is perpendicular to the longitudinal direction LD of the body portion 208a. An example range for the overall 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 contemplated.

[0044] Figures 2B-2F Various embodiments of the conductive pin 208 are illustrated, including pin heads 208b1, 208b2, 208b3, 208b4, and 208b5, respectively. Throughout the description of the various embodiments of the conductive pin 208, the following features are common to all of the embodiments: Figures 2B-2FEach respective pin head is illustrated as having a width of W1 and a curved surface (of the bonding surface 208c) with a radius of curvature of p1. Example ranges for W1 include: 0.5 mm to 10 mm; and 1 mm to 4 mm. Example ranges for the radius of curvature p1 include: 1 mm to 1000 mm; and 2 mm to 100 mm. Other ranges are also contemplated.

[0045] With specific reference now to Figure 2B The 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 non-planar surface 208c1a has a radius of curvature of p1.

[0046] With reference now to Figure 2C The pin head 208b2 is illustrated as including 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 also 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 illustrated as a tapered hole having a width of W2, an angle of 01, and a maximum depth of d1. Example ranges for the width W2 are 0.1 mm to 3 mm. Example ranges for the angle 01 are 60 to 170 degrees; and 90 to 120 degrees. Example ranges for d1 include: 10 pm to 1000 pm; and 1 pm to 3000 pm. Other ranges are also contemplated.

[0047] With reference now to Figure 2D The pin head 208b3 is illustrated as including 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 also 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 illustrated as a spherical cap hole or a dome-shaped hole having a width of W2, a radius of curvature of p2, and a maximum depth of d2. Example ranges for the width W2 are 0.1 mm to 3 mm. Example ranges for the radius of curvature p2 include 2 mm to 100 mm; and 1 mm to 1000 mm. Example ranges for the maximum depth d2 include 10 pm to 1000 pm; and 1 pm to 3000 pm. Other ranges are also contemplated.

[0048] With reference now to Figure 2EPin head 208b4 is illustrated as including a bonding surface 208c4. Bonding surface 208c4 includes a non-planar surface 208c4a; specifically, non-planar surface 208c4a is a curved surface. Bonding surface 208c4 also includes a hole 208c4b defined in a central region of bonding surface 208c4. Specifically, hole 208c4b is a cylindrical hole. Hole 208c4b is illustrated as having a width W2, and a maximum depth d3. Example ranges for width W2 include: 0.1 mm to 3 mm. Example ranges for maximum depth d3 include: 10 pm to 1000 pm; and 1 pm to 3000 pm. Other ranges are also contemplated. It should be appreciated that hole 208c4b can be implemented as a rectangular hole, an elliptical hole, and other geometrically shaped holes.

[0049] Reference is now made to Figure 2F Pin head 208b5 is illustrated as including a bonding surface 208c5. Bonding surface 208c5 includes a non-planar surface 208c5a; specifically, non-planar surface 208c5a is a curved surface. Bonding surface 208c5 also includes a hole 208c5b defined in a central region of bonding surface 208c5. Specifically, hole 208c5b is a cylindrical hole. Hole 208c5 is illustrated as having a width W2, and extending through a length (e.g., full length) of body portion 208a. Example ranges for width W2 include: 0.1 mm to 3 mm. Other ranges are also contemplated. It should be appreciated that hole 208c5b can be implemented as a rectangular hole, an elliptical hole, a pyramidal hole, and other geometrically shaped holes.

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

[0051] Figures 3B-3F Various embodiments of conductive pin 308 are illustrated, including pin heads 308b1, 308b2, 308b3, 308b4, and 308b5, respectively. Throughout the description of the various embodiments of conductive pin 308, it should be appreciated that the various features of the embodiments can be combined in any manner. Figures 3B-3FEach respective pin head is illustrated as having a width of W1 and an angled surface of a bond surface of an angle of Θ2. The angled surface is configured to have an angle of Θ2 with respect to a horizontal plane HP. Example ranges for W1 include: 0.5 mm to 10 mm; and 1 mm to 4 mm. Example ranges for the angle Θ2 include: 1 to 15 degrees; and 1 to 45 degrees. Other ranges are also contemplated.

[0052] With specific reference to Figure 3B The pin head 308b1 is illustrated as including a bond surface 308c1. The bond surface 308c1 includes a non-planar surface 308c1a; specifically, the non-planar surface 308c1a is an angled surface. The non-planar surface 308c1a has an angle of Θ2.

[0053] With reference now to Figure 3C The pin head 308b2 is illustrated as including a bond surface 308c2. The bond surface 308c2 includes a non-planar surface 308c2a; specifically, the non-planar surface 308c2a is an angled surface. The bond surface 308c2 also includes a hole 308c2b defined in a central region of the bond surface 308c2. Specifically, the hole 308c2b is an angled hole. The hole 308c2b is illustrated as a tapered hole having an angle of Θ1, a width of W2, and a maximum depth of d1. Example ranges for the angle Θ1 include: 60 to 170 degrees; and 90 to 120 degrees. Example ranges for the width W2 include: 0.1 mm to 3 mm. Example ranges for the maximum depth d1 include: 10 μιη to 1000 μιη; and 1 μιη to 3000 μιη. Other ranges are also contemplated.

[0054] With reference now to Figure 3D The pin head 308b3 is illustrated as including a bond surface 308c3. The bond surface 308c3 includes a non-planar surface 308c3a; specifically, the non-planar surface 308c3a is an angled surface. The bond surface 308c3 also includes a hole 308c3b defined in a central region of the bond surface 308c3. Specifically, the hole 308c3b is a curved hole. The hole 308c3b is illustrated as a spherical cap hole or a dome-shaped hole having a radius of curvature of p2, a width of W2, and a maximum depth of d2. Example ranges for the radius of curvature p2 include: 2 mm to 100 mm; and 1 mm to 1000 mm. Example ranges for the width W2 include: 0.1 mm to 3 mm. Example ranges for the maximum depth d2 include: 10 μιη to 1000 μιη; and 1 μιη to 3000 μιη. Other ranges are also contemplated.

[0055] With reference now to Figure 3EPin head 308b4 is illustrated as including a bonding surface 308c4. Bonding surface 308c4 includes a non-planar surface 308c4a; specifically, non-planar surface 308c4a is an angled surface. Bonding surface 308c4 also includes a hole 308c4b defined in a central region of bonding surface 308c4. Specifically, hole 308c4b is a cylindrical hole. Hole 308c4b is illustrated as having a width W2, and a depth d3. Example ranges for width W2 include: 0.1 mm to 3 mm. Example ranges for depth d3 include: 10 pm to 1000 pm; and between 1 pm to 3000 pm. Other ranges are also contemplated. It should be appreciated that hole 308c4b can be implemented as a rectangular hole, an elliptical hole, and other geometrically shaped holes.

[0056] Reference is now made to Figure 3F Pin head 308b5 is illustrated as including a bonding surface 308c5. Bonding surface 308c5 includes a non-planar surface 308c5a; specifically, non-planar surface 308c5a is an angled surface. Bonding surface 308c5 also includes a hole 308c5b defined in a central region of bonding surface 308c5. Specifically, hole 308c5b is a cylindrical hole. Hole 308c5b is illustrated as having a width W2, and extending through the length (e.g., full length) of body portion 308a. Example ranges for width W2 include: 0.1 mm to 3 mm. Other ranges are also contemplated. It should be appreciated that hole 308c5b can be implemented as a rectangular hole, an elliptical hole, a pyramidal hole, and other geometrically shaped holes.

[0057] Reference is now made to Figure 4A A conductive pin 408 is illustrated. Conductive pin 408 includes a body portion 408a. Conductive pin 408 also includes a pin head 408b at a distal end of body portion 408a (i.e., along the z-axis). Pin head 408b defines a bonding surface 408c configured to be ultrasonically welded to a workpiece. Bonding surface 408c includes at least one of: (i) a non-planar surface and (ii) a hole defined in a central region of bonding surface 408c. A longitudinal direction LD of body portion 408a and a horizontal plane HP are illustrated; horizontal plane HP is perpendicular to the longitudinal direction LD of body portion 408a.

[0058] Figures 4B-4D Various embodiments of conductive pin 408 are illustrated, including pin heads 408b1, 408b2, and 408b3, respectively. Throughout the description of the various embodiments of conductive pin 408, it should be appreciated that the various features of the embodiments can be combined in any manner. Figures 4B-4D Each respective pin head is illustrated as having a width of W1. Example ranges for width W1 include: 0.5 mm to 10 mm; and 1 mm to 4 mm. Other ranges are also contemplated.

[0059] Reference is now made to Figure 4BPin head 408b1 is illustrated as including a bonding surface 408c1. Bonding surface 408c1 includes a hole 408c1a defined in a central region of bonding surface 408c1. In particular, hole 408c1a is an angled hole. Hole 408c1a is illustrated as a tapered hole having an angle θ1, a width W2, and a maximum depth d1. Example ranges for angle θ1 include: 60 to 170 degrees; and 90 to 120 degrees. Example ranges for width W2 include: 0.1 mm to 3 mm. Example ranges for maximum depth d1 include: 10 μιη to 1000 μιη; and between 1 μιη to 3000 μιη. Other ranges are also contemplated.

[0060] Referring now to Figure 4C Pin head 408b2 is illustrated as including a bonding surface 408c2. Bonding surface 408c2 includes a hole 408c2a defined in a central region of bonding surface 408c2. In particular, hole 408c2a is a curved hole. Hole 408c2a is illustrated as a spherical cap hole or a dome-shaped hole having a radius of curvature p2, a width W2, and a maximum depth d2. Example ranges for radius of curvature p2 include: 2 mm to 100 mm; and 1 mm to 1000 mm. Example ranges for width W2 include: 0.1 mm to 3 mm. Example ranges for maximum depth d2 include: 10 μιη to 1000 μιη; and between 1 μιη to 3000 μιη. Other ranges are also contemplated.

[0061] Referring now to Figure 4D Pin head 408b3 is illustrated as including a bonding surface 408c3. Bonding surface 408c3 includes a hole 408c3a defined in a central region of bonding surface 408c3. In particular, hole 408c3a is a cylindrical hole. Hole 408c3a is illustrated as having a width W2, and a maximum depth d3. Example ranges for width W2 include: 0.1 mm to 3 mm. Example ranges for maximum depth d3 include: 10 μιη to 1000 μιη; and 1 μιη to 3000 μιη. Other ranges are also contemplated. It should be appreciated that hole 408c3a can be implemented as a rectangular hole, a pyramidal hole, an elliptical hole, and other geometrically shaped holes.

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

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

[0064] Reference is now made to Figure 5 , which shows a power module 122 (one specific type of workpiece). 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 die (e.g., a power semiconductor element). Exemplary semiconductor elements include a substrate (e.g., a leadframe, a PCB, a carrier, etc.), a substrate that carries one or more semiconductor dies, a bare semiconductor die, a packaged semiconductor device, a flip-chip semiconductor device, a die embedded in a substrate, a semiconductor die stack, etc. Further, 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 die configuration).

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

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

[0067] Figure 6is a flowchart illustrating a method of ultrasonically welding a conductive pin to a workpiece. As will be appreciated by those skilled in the art, certain steps included in the flowchart can be omitted; certain additional steps can be added; and the order of the steps can be changed, all without departing from the scope of the present disclosure.

[0068] At step 600, a workpiece (e.g., workpiece 102a1 / 102a2 / 102a3 in FIG. 1) is provided. Figure 1 At step 600, a workpiece (e.g., workpiece 102a1 / 102a2 / 102a3 in FIG. 1) is provided. Figure 5 At step 600, a workpiece (e.g., workpiece 102a1 / 102a2 / 102a3 in FIG. 1) is provided.

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

[0070] At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1, Figure 1 At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1, At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1,

[0071] At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1, Figure 1 At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1, At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1,

[0072] At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1, Figure 1 At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1, At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1,

[0073] At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1, Figure 1 At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1, At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1,

[0074] At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1, Figure 1 At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1, At step 602, a conductive pin (e.g., conductive pin 108 in FIG. 1,

[0075] In particular embodiments, step 602 includes applying process parameters during ultrasonic welding using a control system (e.g., control system 120 in FIG. 6B) where the ultrasonic welding employs torsional vibrations applied by an ultrasonic horn configured to ultrasonically weld a conductive pin to a workpiece during a welding process. Figure 1

[0076] While the application has been illustrated and described in connection with certain embodiments, it will be understood that it is not intended to be limited to the details shown. Rather, this application is intended to cover any alternatives, modifications, equivalents, and other uses within the scope of the claims and the scope of the specification and the appended claims.​

Claims

1. An electrically conductive pin for ultrasonic welding, characterized in that, The electrically conductive pin comprises: a body portion; and a pin head at one end of the body portion, the pin head defining a bonding surface 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 electrically conductive pin of claim 1, wherein, The bonding surface comprises a non-planar surface.

3. The electrically conductive pin of claim 2, wherein, The non-planar surface is a curved surface.

4. The electrically conductive pin of claim 3, wherein, The curved surface has a radius of curvature of between 2 mm and 100 mm.

5. The electrically conductive pin of claim 3, wherein, The bonding surface further comprises a hole defined in a central region of the bonding surface.

6. The electrically conductive pin of claim 5, wherein, The hole has a maximum depth of between 10 pm and 1000 pm.

7. The electrically conductive pin of claim 5, wherein, The hole extends through a full length of the body portion of the electrically conductive pin.

8. The electrically conductive pin of claim 5, wherein, The hole is a tapered hole.

9. The electrically conductive pin of claim 5, wherein, The hole is a curved hole.

10. The electrically conductive pin of claim 9, wherein, The curved hole has a radius of curvature of between 2 mm and 100 mm.

11. The electrically conductive pin of claim 5, wherein, The hole is a cylindrical hole.

12. The electrically conductive pin of claim 2, wherein, The non-planar surface is an angled surface.

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

14. The electrically conductive pin of claim 12, wherein, The bonding surface further comprises a hole defined in a central region of the bonding surface.

15. The electrically conductive pin of claim 14, wherein, The hole has a maximum depth of between 10 pm and 1000 pm.

16. The electrically conductive pin of claim 14, wherein, The hole extends through a full length of the body portion of the electrically conductive pin.

17. The electrically conductive pin of claim 14, wherein, The hole is a tapered hole.

18. The electrically conductive pin of claim 14, wherein, The hole is a curved hole.

19. The electrically conductive pin of claim 14, wherein, The hole is a cylindrical hole.

20. The electrically conductive pin of claim 1, wherein, The bonding surface comprises a hole defined in a central region of the bonding surface.

21. The electrically conductive pin of claim 20, wherein, The hole is a tapered hole.

22. The electrically conductive pin of claim 20, wherein, The hole is a curved hole.

23. The electrically conductive pin of claim 22, wherein, The curved hole has a radius of curvature of between 2 mm and 100 mm.

24. The electrically conductive pin of claim 20, wherein, The hole is a cylindrical hole.

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

26. The electrically conductive pin of claim 1, wherein, The bonding surface is configured to be ultrasonically welded to a workpiece using torsional vibrations.

27. A power module, characterized by Comprise: a semiconductor element; a carrier for supporting the semiconductor element; and at least one electrically conductive pin ultrasonically welded to the carrier, the electrically 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, wherein the bonding surface of the electrically conductive pin, prior to being ultrasonically welded to the carrier, comprises 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 of 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 hole has a maximum depth of between 10 pm and 1000 pm.

33. The power module of claim 31, wherein, The hole extends through a full length of the body portion of the electrically 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 of 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. The angled surface is configured to have an angle relative to a horizontal plane of between 1 degree and 15 degrees, the horizontal plane being perpendicular to a longitudinal direction of the body portion.

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 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 hole has a maximum depth between 10 pm and 1000 pm.

42. The power module of claim 40, wherein, The hole extends through a full 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 further comprises 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 hole 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 hole has a maximum depth between 10 pm and 1000 pm.

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

53. An ultrasonic welding system configured for welding a conductive pin to a workpiece, characterized in that, The ultrasonic welding system comprises: an ultrasonic horn configured to ultrasonically weld the conductive pin to the workpiece during a welding process; and 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 a process parameter based on the bonding surface during the welding process.

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

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

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, the control system is configured to apply a process parameter based on the non-planar surface and the hole defined in the central region of the non-planar surface during the welding process.

58. The ultrasonic welding system of any one of claims 54 to 57, wherein, The process parameter comprises at least one of a bonding force, a bonding energy, and a bonding time.

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

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