Abstract: An unwelded battery assembly (32) is fed to a shuttle (36) which moves the unwelded battery assembly (32) to a moveable platform (46) in a raised position. The platform lowers the battery assembly into a nest (44) which rigidly supports the battery assembly. An ultrasonic horn is lowered into contact with the battery assembly and welds the battery cover (16) to the battery housing (14). The welded battery assembly (57) is then raised out of the nest by the moveable platform (46), and is moved to a second stage (48) while another unwelded battery assembly is shuttled to the platform. A central control circuit (49) operates and synchronizes the apparatus.

Abstract: A low mounting impedance ultrasonic transducer for mounting on a bonding machine comprises a prior art type transducer having a modified mounting flange which includes one or more elongated apertures in the mounting flange or the transducer body to isolate transverse radial stress in the transducer body from entering into the mounting flanges and coupling to the bonding machine.

Abstract: A mount for a vibratory member, such as an elongate half wavelength resonator, includes a pair of cylindrical flexural tubes, each tube coupled with one end to the nodal region of the member and the other end of each tube coupled to a stationary member. The axial length and the thickness of the tubes are selected to enable the tubes to flex radially responsive to the substantially radial vibrations manifest at the nodal region of the member so as to decouple the vibrations of the member from the stationary member. A method of decoupling a vibration member from its stationary mount is also described.

Abstract: An extrusion assembly for extrusion of a triple walled (plastic/metal/plastic) pipe includesa first extrusion apparatus, for extruding an inner plastics layer of the pipe, having an extruder with a coaxial outer extrusion sleeve and inner extrusion die,a shaping sleeve surrounding and substantially coaxial with the extruder, which shaping sleeve is capable of shaping a U-section form metallic layer passing through it into a tubular configuration and a welder for welding the metallic layer of tubular configuration to provide a metal tube,a conduit for supplying a pressurized gas internally of the pipe whereby extruded plastics material emerging from the first extrusion apparatus is forced against an internal surface of the metal tube, anda second extrusion apparatus, for extruding an outer plastics layer of the pipe, having a body part and a supply channel within the body part for supplying plastics material,which extrusion assembly has at least one of,(a) an essentially annular section recess in the body part

Abstract: A laser head for simultaneously attaching solder balls to a carrier has at least one solder tip, with the number of solder tips being equal to the number of solder balls to be attached to the carrier. Each solder tip is heated by an optical fiber in thermal contact with the tip at one end of the fiber and coupled to a laser, preferably operating in the infrared wavelength range, at the other end of the fiber via a multiplexer coupling device. A spring is used in association with each solder tip to bias each solder tip to hold the carrier in contact with the solder balls. The tip absorbs the radiant energy as it exits the optical fiber, and the tip is heated. The laser and multiplexer permit precise control over the heat imparted to the tip, which in turn permits control of the amount of the solder ball that is reflowed.

Abstract: A polar motion bond head for bonding semiconductor devices includes voice coil motors for providing positioning motion to the bond head, and a vision system that has an optical path that allows the camera to see all polar positions with the image staying on the camera centerline.

Abstract: An ultrasonic horn of a bonding apparatus quipped with a bonding tool attached to one end of the horn and a vibration-generating source such as an electrostrictive strain element, magnetostrictor, etc. attached to a bonding arm that supports the bonding horn. The ultrasonic horn is further provided with a vertical vibration adjuster which adjusts the vertical component of the vibration of the ultrasonic horn, and the vertical vibration adjuster includes a projection, recess, etc. provided at the end of the horn.

Abstract: In a wave solder manufacturing process, a test device is used to measure the contact-area between a solder wave and a printed wiring board. In particular, the test device is a printed wiring board (PWB) that includes at least two arrays of electrical contacts, one array near each side of the PWB. As the PWB makes contact with a solder wave, the number of electrical contacts in each array that are grounded by the solder wave are counted and displayed on an alpha-numeric display mounted on top of the PWB. This "distance-based" measurement provides an accurate determination of the uniformity of the contact-area, and concomitantly the dwell-time of the soldering process. This test device provides a basis for real-time adjustment of solder wave height, and end-to-end balance, in a solder wave machine. In particular a wave solder machine includes a means for receiving contact-area information from the test device and a means for adjusting the solder wave in response to the contact-area information.

Abstract: A method of bond quality monitoring wherein a bonding machine is fitted with a touchdown mechanism including a pair of contacts (23, 24), which normally open upon touchdown of a bonding tool (27) raised and lowered by a bond head carriage (13). As the tool (27) is lowered towards a bonding surface (31), the bonding machine's computer (61) performs a test (103) to sense production of a touchdown signal produced by opening of the contacts (23, 24). If touchdown is sensed, the carriage (13) proceeds to an overtravel position. Upon reaching the overtravel position, a second test (108) is performed to confirm touchdown, and energy is then applied to the bond site. During energy application, the logic state of the touchdown mechanism is checked to ensure that the contacts do not close, for example, to check for application of inadequate force during bonding. If a contact closure is sensed, the bond site location is logged for further examination such as a nondestructive pull test.

Abstract: An apparatus for enhancing toner release from an image bearing member in an electrostatographic printing machine, including a resonator suitable for generating vibratory energy arranged in line contact with the back side of the image bearing member for uniformly applying vibratory energy to the image bearing member. The resonator includes a piezoelectric transducer and a horn-type waveguide assembly, wherein an adhesive epoxy augmented with a substantial concentration of electrically conductive, free flowing particulate bead elements is used to bond the horn and piezoelectric transducer element together, without the requirement of a backing plate or bolts. The conductive beads resolve bond layer thickness anomalies while eliminating adhesive flow restrictions such that substantially uniform tip velocity and frequency output can be achieved.

Abstract: A bonding tool for connecting inner leads to pads of a semiconductor chip by means of high efficiency transmittance of ultrasonic vibrations is disclosed. The shape of the tool as seen in a plane parallel to the ultrasonic vibration is either to have a substantially flat plane on one side and a uniformly continuous sloped plane with a predetermined angle starting from a pressing face against the inner lead, or to have the shape of a uniformly continuous machined conical surface starting upwardly from the pressing face until the diameter of the cone reaches 200 .mu.m or more.

Abstract: A bonding apparatus used in manufacturing, for example semiconductor devices, including an adiabatic plate provided beneath a bonding horn for blocking the radiant heat from a heating block that heats up a workpiece. The apparatus further includes horn cooling pipes and a mirror tube cooling pipe for blowing cooling air onto a bonding horn and onto a mirror tube of a detection camera or a detection camera supporting arm.

Abstract: A novel bonding tool is designed for use in conventional ultrasonic transducers. The bonding tool body is mounted in the ultrasonic transducer at an angle or in an offset holder so that the working face of the bonding tool is offset and out from under the end of the ultrasonic transducer. The axis of a wedge bonding tool body is mounted at an inclined angle of up to forty-five degrees and the tapered wedge of the bonding tool is inclined in the opposite direction so that the working face of the offset tapered wedge is in a horizontal working plane.

Abstract: A wire bonder for electrically coupling an integrated circuit die to associated wiring traces is disclosed. In one aspect of the invention, the wire bonder includes a pair of ultrasonic transducers. A capillary holder is connected between the transducers to support a capillary having a bonding wire suitable for electrically connecting an integrated circuit die pad to a lead on an associate wiring trace. A signal generator applies drive signals to the transducers to mechanically bond a bonding wire to at least one of an integrated circuit die pad and a wiring trace. The signal generator is arranged to permit independent actuation of the transducers at frequencies suitable for ultrasonic welding. The signal generator means includes a controller for controlling the timing of the drive signals. With this arrangement, the direction of ultrasonic energy applied during welding may be varied by adjusting the relative timing of actuation of the transducers.

Abstract: A method and apparatus for non-destructively detecting pressure contact open types of solder connections transmits acoustic emissions through an electronic component and the carrier upon which the electronic component is mounted by one or more solder connections. Emissions which are transmitted through the solder connections and which will interact with acoustic emissions generated if pressure contact opens are present are analyzed by comparison with the signal which is used to cause emissions to detect the presence of pressure contact opens by comparison of one or more of harmonics, energy, count, voltage, duration, rise time and time delay. A housing is preferably used to position a pair of transducers at respective locations which have solder connections topologically intervening therebetween. The testing process can thus be automated for screening assembled devices for the presence of pressure contact opens.

Abstract: A bonding apparatus with an ultrasonic horn for manufacturing, for example, semiconductor devices having a horn support that is used for mounting the ultrasonic horn to a bonding arm of the bonding apparatus, and tow vibration-generating sources are provided on both sides of the horn support. The vibration-generating sources are such a piezoelectric element as an electrostrictive strain element and a magnetostrictor.

Abstract: A motor-vehicle latent-heat storage unit is made by first positioning an elongated rectangular sheet-metal blank over a longitudinally extending slot formed in a die and then pressing an elongated anvil bar forming one of a pair of ultrasonic welding tools down against the blank over the slot to push the bar and the blank into the slot. This imparts to the blank a U-section and leaves longitudinally extending edge regions of the blank projecting out of the slot past the anvil bar. These edge regions are then folded transversely one after the other inward over the bar to form the blank into a tube with the edge regions overlapping each other. The other of the ultrasonic welding tools is subsequently pressed against the overlapped edge regions and therethrough against the anvil bar to ultrasonically weld together the overlapped edge regions along a full length of the tube. Finally the welded tube and the bar are moved longitudinally relative to each other to separate the tube from the bar.

Abstract: A method of bond quality monitoring wherein a bonding machine is fitted with a touchdown mechanism including a pair of contacts (23, 24), which normally open upon touchdown of a bonding tool (27) raised and lowered by a bond head carriage (13). As the tool (27) is lowered towards a bonding surface (31), the bonding machine's computer (61) performs a test (103) to sense production of a touchdown signal produced by opening of the contacts (23, 24). If touchdown is sensed, the carriage (13) proceeds to an overtravel position. Upon reaching the overtravel position, a second test (108) is performed to confirm touchdown, and energy is then applied to the bond site. During energy application, the logic state of the touchdown mechanism is checked to ensure that the contacts do not close for example to check for application of inadequate force during bonding. If a contact closure is sensed, the bond site location is logged for further examination such as a nondestructive pull test.

Abstract: A bonding head for an ultrasonic bonding machine comprises a wedge operatively associated with an ultrasound transducer by means of which an electrically conducting wire can be pressed against a contact surface of an electrical or electronic component and bonded thereto by ultrasonic excitation of the wedge. A wire clamp is located adjacent to and ahead of the wedge and can be moved back and forth by drive means in the direction of the wire being fed to the wedge. The wedge can be moved up and down together with the wire clamp and its drive means in a direction substnatially perpendicular to the contact surface. The bonding head as a whole is also disposed so that it can be swung about an axis perpendicular to the contact surface. The drive means for wire clamp comprises a translational drive which can move the wire clamp exactly parallel to the direction of the wire being fed to the wedge.

Abstract: A wedge bond tool tip (20, 30, 50, 56) for bonding electronic interconnects to bonding pads of a semiconductor device enables fine-pitch non-orthogonal wire bonding. The tool tip (20, 30, 50, 56) has an overall width and a front face (12', 52) that has a reduced area which is narrower than the overall width. The reduction in the front face is accomplished through either chamfering or rounding of the corners to reduce the contact distance (42 and 44) between the wedge tool and a previously made adjacent bond. This design maintains the structural integrity needed to produce acceptable wedge bonds.

Abstract: Mounting means for a vibratory member, such as an elongate half wavelength resonator, include a pair of cylindrical tubes, each tube coupled with one end to the nodal region of the member and the other end of each tube coupled to a stationary clamping means disposed about the member. The axial length and the thickness of the tubes are selected to enable the tubes to flex radially responsive to the substantially radial vibrations manifest at the nodal region of the member, whereby to decouple the vibrations of the member from the stationary clamping means.

Abstract: A wire bonding apparatus realizing stable bonding by supplying a constant electric power to a joint. Under loadless conditions, an electric-power calculation circuit calculates the power supply from a feedback current and oscillating voltage corresponding to a level setting signal set to a level change circuit. When the tip of a bonding wire contacts a bond electrode, the feedback current gets smaller than that under loadless conditions and the power supply decreases. The electric-power calculation circuit calculates the power supply from the feedback current and oscillating voltage and a correction circuit outputs a control voltage for complementing a decrease of power supply accumulated since the loadless state. A level change circuit converts an oscillating voltage into a level corresponding to the control voltage. Thereby, the electric power to be supplied to the joint is kept constant.

Abstract: An ultrasonic bonding apparatus comprises an ultrasonic wave controller, a bonding system including a bonding head, a laser oscillator, a laser optics, a vibration monitoring system including a vibrometer, and a mechanism for feeding a result of monitoring back to a bonding condition.

Abstract: A specially designed tip containing an electron discharge milled cone of specific dimensions is used to transfer a critical solder volume from a solder ball carrier to a specific solder ball site on the base line metal on a high density chip, substrate terminal connection, solder ball connection, or any solder ball array. The critical tip/cone dimensions have a height of the cone and a circumference at the base which generate a specific volume of solder to be transferred.

Abstract: A bonding apparatus including an ultrasonic horn that has a bonding tool, a horn support, which is for mounting the ultrasonic horn to a bonding arm of the bonding apparatus, and vibration-generating sources provided on both sides of the horn support. These vibration-generating sources are operated to generate vibrations by an ultrasonic oscillation device that operates the vibration-generating sources via separate outputs.

Abstract: A conventional ultrasonic tube sealing device is modified for dissipating undesirable heat energy by locating in close proximity to a horn a heat sink block, causing via pneumatic means the heat exchange block to make contact with the horn only when the horn is in an open retracted position with respect to an anvil, and causing the heat exchange block to separate from the horn when the horn is in a closed sealing position with respect to the anvil. The heat exchange block cools the heat exchange block by drawing off undesirable heat energy, yet, by separating during the sealing mode, allows the horn to function properly and does not adversely affect its ultrasonic properties. The heat exchange block may be cooled by transporting through strategically located passageways an externally cooled fluid.

Abstract: An automated wire bonding tool for interconnecting circuit pads on microelectronic circuit devices and substrates. A single application of the bonding tool spans both bond sites with the wire being held under the bond tool and gripped at both ends while bonding the wire to both bond sites simultaneously and with high placement accuracy.

Abstract: A conformed control knob (23) is mounted to a manipulating lever (22) of an apparatus (20) having an arm (21) to be operably controlled by the manipulating lever (22). Through manual manipulation of the control knob (23), the arm (21) can be controlled for proportional precision movement. The control knob (23) includes an upwardly facing substantially planar support surface (25) formed for supporting at least one fingertip (26) of an operator's hand thereon, and includes a recess (27) formed therein to receive the fingertip (26). The support surface (26) is sufficiently cupped and the manipulating lever (22) is sufficiently biased upwardly toward the fingertip (26) to transmit both lateral and vertical movement of the operator's hand to the manipulating lever (22) for fingertip control thereof.

Abstract: A bonding apparatus used in manufacturing semiconductor devices, etc. including an ultrasonic horn mounted to a bonding arm of the bonding apparatus via a horn support. The ultrasonic horn is provided with a bonding tool at one end and a vibration-generating source at another end, and respective values of vibrational wavelengths on both sides of the horn support are set so that the value on the bonding tool side of the horn support is 7 or greater relative to a value of 3 on the opposite side of the horn support from the capillary. In other words, the distance from the horn support to the end of the vibration-generating source is set to be 1/4 of the wavelength, and the distance from the horn support to the end of the horn where the bonding tool is attached is set to be 3/4 of the wavelength.

Abstract: A wire bonder system comprising mounting a tool for ultrasonic bonding onto a transducer and the tool is protruded from the transducer with its bonding side to supply the high frequency electric power to the transducer. The protruded length of the tool is adjusted so as to avoid the length protruded from the transducer to minimize the high frequency electric power.

Abstract: A capillary-retaining structure for an ultrasonic horn used in a wire bonding apparatus including a stress relief hole formed inside of a capillary attachment hole that is opened at an end portion of the ultrasonic horn. Thus, the capillary retention by the ultrasonic horn is stabilized, and the vibrational characteristics of the ultrasonic horn are also stabilized, thus improving overall bondability in wire bonding. The same effect can be obtained by setting the thickness of a portion between the end surface of the horn and the capillary attachment hole to be thin or by utilizing a bold and nut combination to hold the capillary.

Abstract: An apparatus for applying interconnect bumps to an integrated circuit comprising a wedge bonder assembly (10) including a bonding tool (14) adapted to be selectively moved relative to the integrated circuit (42) and to transmit ultrasonic force to bond wire or ribbon (62) located between the bonding tool (14) and the integrated circuit (42) to the integrated circuit and form an interconnect bump (63), the bonding tool (14) defining a passage (44) through which wire or ribbon (50) is passed to be brought into contact with the integrated circuit (42) and an edge (38) positioned and adapted to weaken wire or ribbon (50) as the bonding tool (14) is moved to the point at which the bonding tool (14) is closest to the integrated circuit (42), the wedge bonder assembly being adapted to move the bonding tool (14) so as to separate the interconnect bump (63) from the wire or ribbon (50) proximal of the bump.

Abstract: The transducer has a metal body with a welding end, an opposite end for supporting a source for causing the body and the welding end to vibrate at ultrasonic frequency for welding purposes and an intermediate mounting structure for supporting the body for welding purpose. The mounting structure may be a cylinder or flange spaced from and surrounding the body with at least two spaced apart spokes connected between the body and the mounting structure.

Abstract: An ultrasonic bonding apparatus including a piezoelectric element which transmit a vibration via the electric strain or magnetic strain effect to a capillary which is mounted to a non-resonant bonding arm, a microcomputer which outputs frequency data and amplitude data and an open-loop control circuit which includes a memory in which output waveform data is stored, a programmable frequency generator which varies the frequency according to the frequency data from the microcomputer and outputs a memory address switching signal, a first D/A converter which determines the amplitude in accordance with the amplitude data from the microcomputer, and a second D/A converter which applies output voltage or current to the piezoelectric element based upon the output waveform data at an address stored in the memory and selected by the address switching signal which is sent from the programmable frequency generator and upon the amplitude determined by the first D/A converter.

Abstract: An apparatus for ultrasonic sealing of thermoplastic materials includes a vibration generator of a so-called giant magnetostrictive powder composite (GMPC) which is anchored to a jaw at an anchorage point. The vibration generator is formed with a cross-sectional area which progressively reduces as seen from the anchorage point. A free end of the vibration generator has a narrow working surface. The vibration generator is surrounded by a coil for generating a magnetic field.

Abstract: Apparatus and a method for controlling the power output of an ultrasonic generator to a transducer includes a variable impedance network circuit which is interposed between the generator and the transducer. Sensing circuits and a microprocessor are coupled to the input of the transducer so that the total impedance Z.sub.T, the transducer impedance in free air Z.sub.FA and the load impedance Z.sub.L may be calculated and the network impedance Z.sub.NW may be set for a bonding operation to maintain the power level P.sub.L or the impedance Z.sub.L at a desired predetermined level.

Abstract: This invention is intended to reduce the size of a bonding apparatus and includes a first means which is to construct the bonding apparatus by swingably mounting a lifter arm 4 for holding a horn 2 to the upper Y table 9 of an X-Y table 10. The second means is to construct the apparatus by using the upper Y table of the X-Y table as a bottom plate of a bonding head, and the third means is that in addition to the second means, it is further arranged so that a linear motor 15 is fixed such that a part or the entire portion of a magnet section 16 of the linear motor 15 is embedded in the Y table 9, while a coil section 17 of the linear motor 15 is fixed to the lifter arm 4.

Abstract: A polar motion bond head for bonding semiconductor devices includes voice coil motors for providing positioning motion to the bond head, and a vision system that has an optical path that allows the camera to see all polar positions with the image staying on the camera centerline.

Abstract: A head of an ultrasonic wire bonding apparatus for bonding a lead wire to a lead frame, includes a capillary, a capillary supporting member, and a vibrator, vertically arranged and connected to the capillary supporting member, for producing ultrasonic torsional vibration along opposite directions and applying the vibration to the capillary via the capillary supporting member, the vibrator having two piezoelectric elements superimposed on each other via a column member in which magnets are circularly arranged so as to produce the ultrasonic torsional vibration along the opposite directions.

Abstract: An electrical system for vehicle panels which include a plurality of conductors and electrical accessories for connection to the panel. The electrical accessories include insulation displacement contacts for connection with conductors in the panel. In one embodiment, the panel includes a plurality of conductive layers providing an electrical bus for the panel. In another embodiment, the conductors are formed in the panel between two dielectric layers.

Abstract: A method for ball-bonding thin film structures. The bonding characteristics of a thin-film electrode structure are measured, before the actual bonding step, by pressing a ball (of a material similar to that of the bonding wire) against an electrode by a bonding capillary, and then measuring the resultant indentation of the electrode. The depth of this test indentation of the electrode has a good correlation with the bondability.

Abstract: A wire bonding apparatus in fabricating, for example, semiconductor devices including a bonding arm that is vertically and horizontally movable and has a capillary through which a bonding wire is passed. The bonding arm is provided with a piezoelectric element which transmits a vibration to the capillary via its electric strain effect or magnetic strain effect so that the capillary performs wire bonding. With the use of the piezoelectric element that is provided near the capillary, vibrational energy loss can be minimal, and the frequency and amplitude of the vibration can be changed during each bonding operation.

Abstract: In order to vibrate a capillary stably at an arbitrary frequency with an arbitrary waveform, a bonding apparatus having a piezoelectric element vibrating stably at an arbitrary frequency with an arbitrary waveform in response to an input of a piezoelectric element control signal from a piezoelectric element control signal generator is provided.

Abstract: In order to minimize the size of an aluminum pad in a method of forming a bump, a metal wire is wedge-bonded on the aluminum pad, a necessary amount of the wire is left on the aluminum pad, and the metal wire is disconnected by a clamp. The width of a collapsed portion of the wire on the aluminum pad can be reduced to 1.5 times or less the wire diameter.

Abstract: A wire bonding method and apparatus for welding a wire with at least one end formed with a ball and a pad of a printed wiring board. A bonding head moves downward slowly to crush the ball to form a flat surface, and will move upward once to adjust a relative position of the pad and the ball. The bonding head will move downward again, and an ultrasonic wave is applied to heat the ball and the bonding head so that the ball and the pad are welded. If necessary, a portion of the wire to be bent is moved to a desired position of the wiring board, by a supporting apparatus. A free end of the wire which is not welded is moved by a jig to bend the portion of the wire for routing.

Abstract: An (10) and method is provided for bonding wire (12) to the bond sites (28) of integrated circuits (14). In preferred embodiments gold wire (12) is bonded to aluminum bond pad (28). Apparatus (10) includes a high frequency ultrasonic energy source (20) designed to provide ultrasonic energy at frequencies above about 125 kHz. The ultrasonic energy is imparted to the bonding interface (32) via transducer (18) and capillary (16). The transducer is modified in length and tool clamp point (40) is sited on transducer (18) so that the wavelength of the high frequency ultrasonic energy is at the antinodal point in its application to interface (32) and thus is optimized. In the preferred embodiments of the process the ultrasonic energy is applied at about 350 kHz at ambient temperature. In this fashion, the bond formed between bond end (30) and bond pad (28) is optimized in terms of shear strength, bonding time and processing temperatures.

Abstract: An ultrasonic anvil cartridge for use in association with ultrasonic apparatuses for sealing at least two layers of ultrasonic reactive material. The ultrasonic anvil cartridge cooperates with an anvil housing and an ultrasonic wave generator towards maintaining a substantially even pressure across at least two layers of ultrasonic reactive material such that a substantially even and tight seal can be formed across at least two layers of ultrasonic reactive material. The ultrasonic anvil cartridge includes a plurality of substantially C-shaped support members which are operably and successively aligned so as to be positioned one adjacent another. This plurality of substantially C-shaped members is further encapsulated in substantially elastomeric encapsulating material which is operably positioned within the collective concave surface of the plurality of substantially C-shaped support members to form a unitary cartridge having a substantially convex exterior surface.

Abstract: The description relates to an apparatus for the ultrasonic welding of sealing seams on packages for fluid media. The apparatus comprises a sonotrode and an anvil (7) which is situated opposite the front end face of the sonotrode. Both sonotrode and also anvil (7) are adapted for movement on predetermined paths.

Abstract: A single point bonding tool for use in ultrasonically bonding a fine or ultrafine wire to another electrical conductor, has a thin film resistor integrally formed thereon. The thin film resistor is integrally formed on the bonding tip by standard photolithographic techniques applied to the bonding tool. The tool combines ultrasonic energy and thermal energy provided by the resistor to provide required bonding energy that may be localized both in space and in time. The result offers optimized energy transfer to the selected workpieces and minimizes risk of damage to adjacent, heat sensitive devices.

Abstract: A device is described for welding the ends of electrical conductors, especially strand ends, by means of ultrasonics which comprises a sonotrode, provided with a plurality of different projections, and an anvil, associated with the sonotrode, which anvil is provided with a plurality of different or like recesses which, together with the sonotrode projections, constitute compaction spaces for the strand ends. The anvil is disposed with its longitudinal axis coaxially with the longitudinal axis of the sonotrode, and the cross-sections of the compaction spaces can be simultaneously varied by rotation of the anvil relative to the sonotrode about the common longitudinal axis, so that a plurality of strand ends can be simultaneously welded by only one anvil. Several alternatives for the rotational drive of the anvil are also described.