One aspect of our business that has continued to set us apart from our competitors is our patented Wedge-Reed Ultrasonic Welding System.  Specifically designed for high-impedance metal welding, it is the only ultrasonic system able to weld tin-coated and oxidized wires and terminals.  The Wedge-Reed System enables our equipment to produce durable welds without having to sacrifice the protective qualities of tin coating, and at a fraction of the energy and time required by alternative welding methods. 

Why Tinned Copper

Copper has long been the go-to metal for electrical applications due to its superior conductivity and great tensile strength.  But, its effectiveness and longevity plummet in the humid and wet conditions of the marine industry; in high-temperature applications, such as appliance and solar panel wiring; and in high-environmental-stress industries, like waste-water treatment and paper mill operations.  Tin coating protects the underlying copper, resisting corrosion and lengthening the lifespan of wires and terminals. 

Unreliable Welds

Methods for assembly of tin-coated wires include mechanical crimps and resistance welding but neither provides optimum results.  Mechanical fastening is inconsistent and resistance welding uses more energy and presents problems with arcing.  Our ultrasonic method also ensures RoHS compliance which is problematical with soldering, and it speeds up the production process.

Principles of Ultrasonic Welding

The ultrasonic welding process begins with a power supply that converts input line power into high frequency electrical power and transmits that energy to a transducer.  The transducer transforms the electrical energy into vibratory energy.  This vibratory energy is delivered to the welding area in the form of sound waves that are above the audio frequency range – known as ultrasonics. 

When the vibrating, shear forces of the ultrasonic waves are directed via the welding tip to the interface between two metals held together under clamping force, internal stresses cause deformation where the metals are in contact.  A localized increase in temperature, coupled with interfacial slip, breaks up oxides and surface films and permits metal-to-metal contact at many points. 

Continued vibration causes the points to deform, increasing the contact area and creating a structure similar to a diffusion weld but without melting.  The result is a highly conductive, metallurgical bond without the change in structure caused by melting the metals.

Achieving Shear Vibratory Mode

For effective ultrasonic metal welding, the direction of the vibration must be in a shear mode parallel tothe interface of the materials to be welded.  The two methods of achieving this are Sonobond’s Wedge-Reed System and the lateral drive system.

Our Wedge-Reed System uses a vertical vibrating reed, driven by a wedge-shaped coupler and transducer assembly that is perpendicular to the reed. This creates the α motion for the weld.  With the line of static clamping force directly above the parts to be welded, high clamp force can be achieved without bending stress or stalling. 

In contrast, the lateral drive system was originally designed for welding plastic, with the vibration direction perpendicular to the plane of the weld.  For metal welding, the vertical drive system welder is rotated 90 degrees to a lateral position to achieve the necessary shear motion.  The welding tip is part of, or attached to, a longitudinally vibrating transducer-horn assembly driven parallel to the weld interface. 

Because of its cantilevered approach, clamping force is applied some distance from the weld, resulting in a bending moment on the coupler that limits static force.  This makes the lateral drive system incapable of producing acceptable welds for tinned or oxidized wires and terminals.

Matching System and Load Impedance

While our Wedge-Reed System features low vibratory amplitude and high vibratory force, suitable for welding metals, the lateral drive system is characterized by high vibratory amplitude and low vibratory force, appropriate for welding plastics.  This affects the amount of vibratory force and impedance each system can produce.  Operating at the same power level, the Wedge-Reed System has an impedance value about nine times that of a lateral drive system.

In ultrasonics, as in electrical systems, the most efficient operation is achieved when the system impedance and the load impedance are closely matched. In ultrasonic welding, the acoustic load impedance is proportional to the density of the materials being welded. 

Since most metals are six to nine times as dense as plastics, it’s clear that our Wedge-Reed System provides a better impedance match for a metal weld than a lateral drive system.  This is especially true for oxidized and tinned metal surfaces, which present an even higher impedance than cleaned or bare metals.

While plastic has low impedance and requires high vibration amplitudes (up to about .005 inches) to weld, metal has high impedance and usually welds better at lower amplitude levels (about .001 inches or less).

Additionally, up to a certain point, the energy required to make a weld decreases as the static force increases, indicating that static force affects load impedance.  Again, our Wedge-Reed System, with its ability to achieve high static clamping force, is better suited for metal welding than the lateral drive system.

Sonobond Equipment Options

Sonobond offers a variety of ultrasonic welders that handle a range of wire bundle sizes starting at one sq. mm.  Our SpliceRiteTM units provide one-pulse wire splicing of up to 100 mm2 in stranded bare copper wire and tinned wire to 60mm2.  Our SonoWeld® and Dual Head Spot Welders can be custom-tooled to suit special applications such as welding tinned wire to bare or coated terminals, completing most assemblies in less than one second with minimal operator training.

All Sonobond metal welding machines feature a microprocessor controller that can be equipped to program welds by height, energy or time, and store and recall up to 250 jobs.   Plus, all   units have heat-treated, taper-lock tips that are capable of up to 100,000 welds.  They’re easily replaceable without requiring machine readjustment or calibration.  Additionally, our equipment offers automatic frequency control and overload protection, and can detect and prevent wrong-part or no-part activation.

Free Welding Viability Test

To ensure that our equipment meets your needs and specifications, we offer a free Ultrasonic Welding Viability Test using materials supplied by you.  Simply click here to request your free sample welds.  If Sonobond units are incorporated into your production process, we provide service and technical support before, during and after installation.

An industry leader

Sonobond has been a pioneer in ultrasonic technology, holding more than 150 patents, including the first for ultrasonic metal welding in 1960, when the company was known as Aeroprojects.  In the ensuing 60+ years, we have established and maintained a well-earned reputation for innovative and quality-engineered products.  Today, our company manufactures a complete line of ultrasonic welding and bonding equipment used by leading firms in the electrical, automotive, appliance, HVAC, solar, aerospace, filtration, medical and apparel industries.

More information

Click here for more information on our ultrasonic technology and on the equipment mentioned in this article.  For immediate attention, call 800-323-1269, 610-696-4710 or email me directly at This email address is being protected from spambots. You need JavaScript enabled to view it..