Part 1: Ultrasonic Metal Welding in Accessory Power Components

Industrial welding conjures up the hiss of Argon, incandescent sparks, and the acrid smoke of white-hot welding rods to strengthen steel joints. In contrast, ultrasonic welding uses friction to weld metals—vibrations upwards of 20,000 Hz per second. In the 1960s, ultrasonic welding was firmly entrenched in the automotive and toy industries. This two-part series will highlight metal welding first with plastic next month.

Today, ultrasonic welding has expanded far beyond automobile subsystems and toys—a universal welding process certainly used in billions if not trillions of products from cell phones to computers, to food containers and thin metals including copper wire. Somewhere along the assembly line you will likely find an ultrasonic welder—it has long become a staple in just about every aspect of manufacturing. 

Inside a Socket Strip

With production facilities in Oskaloosa and Lamoni, Iowa, Interpower Corporation uses metal ultrasonic welders for its components and accessory power system must-haves such as accessory power strips (APS) and power distribution units (PDUs). The accessory power systems contain intricate ultrasonic welded wiring inside the metal housings. 

“Bricks” of Ultrasonic Welded Copper Inside a Socket Strip

Dan Ford, Technical Support Specialist at Interpower, shares what you need to know when designing a product for worldwide markets and how you can utilize Accessory Power.

What ultrasonic welding does is bond material at the molecular level of material through intense friction (heat) and shear force. In Interpower’s case, that material is copper conductor wire—no matter the AWG or mm² sizes, all strands must be bonded, resulting in a rectangular “gold brick” of copper. This type of weldment strengthens the existing copper without the copper leaving its solid state, making it both durable and reliable as a conductor of electricity. Though Interpower uses its welder primarily for copper, ultrasonic welding is used to bond a wide variety of other soft, conductive non-ferrous metals such as aluminum, brass, gold, lithium, nickel and silver.

The ultrasonic welder used by Interpower allows operators to place the wire into the tooling’s “welding zone” which rests in the Anvil (a “mold”) the latter providing a knurled surface designed to hold wires securely against the lower component which vibrates at 20,000 Hz. The Gathering Tool sweeps across the face of the tip to collect the wire strands which forms the width of the Compressor Chamber. The ultrasonic energy is introduced through the tip or the welder’s “horn” creating an oscillating shear force which bonds the wires via friction and heat without melting the wires. The ultrasonic energy is delivered efficiently with a proper combination of base material, shape, and knurled design.

Welding Copper on the Ultrasonic Welding Machine

Programmable Metrics:

• Energy
• Weld Pressure
• Amplitude
• Splice Height

Weld Modes:

• Energy
• Time (Seconds)
• Height (mm)
• Advantages and Testing

In comparison to other bonding methods such as soldering and clipping, ultrasonic metal welding doesn’t require added metals or compounds to create bonds. The process is highly controllable and repeatable as a solid-state bonding technique. Many variables are involved in the ultrasonic welding process—amplitude, frequency, pressure and tooling are the major ones.

After experimenting with settings and developing weld parameters through experimentation, the machine settings can be documented for training purposes and used by future machine operators based on the current settings of the machine. As with any process, testing is a key factor. If not welded properly, strands will come loose, or the wire becomes brittle. There is resistance-destruction testing such as pulling and peeling the weld, but destructive testing is time-consuming and may not offer reliable accuracy.

Ultrasonic weld inspection has an advantage over traditional weld inspection methods currently in operation such as destructive testing and visual inspection. A major advantage is the software’s ability to measure the size of the weld brick without the use of destructive testing. Such tracking software processed by the welder’s CPU can greatly contribute to the consistency of real-time weld inspection. When inspection parameters are integrated into the CPU, and measurements are allowed to influence control parameters during the welding process, the inspection system becomes its own automated quality assurance system. This is a major advancement over destructive testing.

Choosing the appropriate ultrasonic welder based on application, frequency, and materials is also essential. Companies, like Emerson, Sonics and Rexroth offer a range of welders and services to meet ever-changing industry demands, including automation integration—they can help simplify the process of setting up your ultrasonic welding needs for streamlining production.

Next month, we will examine the ultrasonic welding of plastic.