Ultrasonic Soldering – Flux-Free Joining of Hard Metals to Steel

Ultrasonic soldering is revolutionizing the way hard metals are joined, offering a cleaner, more efficient alternative to traditional methods. By applying high-intensity ultrasonic waves, this advanced technique eliminates the need for toxic fluxes, which are commonly used to break down oxides and enable bonding. Particularly effective for challenging materials like tungsten carbide, ultrasonic soldering enhances joint strength while reducing health risks and environmental impact. This innovative approach is opening new possibilities for industries requiring robust, reliable connections between hard metals and steel.

The Sonicator UIP1000hdT for Soldering

The RIF Institute achieved its groundbreaking soldering results using the Hielscher UIP1000hdT, a 1000-watt probe-type sonicator renowned for its precision and power. This state-of-the-art device generates high-intensity ultrasonic waves, enabling advanced processes like cavitation to effectively break down oxides and enhance material wetting. Its robust design ensures consistent performance under demanding conditions, while its user-friendly touchscreen interface and programmable settings provide precise control over key parameters. The UIP1000hdT’s ability to deliver reliable, repeatable results makes it an indispensable tool for cutting-edge research and industrial applications, including ultrasonic-assisted soldering.

In the quest for innovative and sustainable manufacturing solutions, the RIF Institute for Research and Transfer (Dortmund, Germany) has achieved a breakthrough in ultrasonic-assisted soldering for joining hard metals to steel. This cutting-edge approach eliminates the need for toxic fluxes, offering both health and environmental benefits while maintaining robust joint performance.

The Challenge of Soldering Hard Metals

Hard metals, such as tungsten carbide, are notoriously difficult to solder due to their structural properties and chemical behavior. Traditional soldering with steel is hampered by two main factors:

• Differential Thermal Expansion: The mismatched expansion rates of hard metals and steel during the soldering process can compromise joint integrity.
• Oxide Formation: Oxide layers naturally form on metal surfaces during soldering, impeding the wetting process and reducing bond strength.

In order to address these challenges, conventional soldering methods rely heavily on chemically aggressive fluxes. However, these fluxes pose significant health risks and can damage materials over time. Alternatives such as vacuum or protective gas soldering are effective but come with high equipment costs and lengthy processing times.

The Ultrasonic Solution: Flux-Free Soldering

Ultrasonic-assisted soldering presents a groundbreaking alternative. Already utilized for light metals, this method leverages ultrasonic waves to enhance soldering performance at lower temperatures.

How Ultrasonic Soldering Works

When ultrasonic waves are applied to the soldering process, they create a phenomenon called cavitation. This involves the formation of microscopic gas bubbles in the solder, which collapse under high pressure and temperature. This implosive action comes with several benefits:

• Breaks up and removes oxide layers from the metal surfaces.
• Distributes oxide fragments throughout the solder seam.
• Enhances wetting of the hard metal by the solder.

By eliminating the need for flux, ultrasonic soldering significantly reduces chemical hazards while achieving high-quality bonds.

Advanced Soldering Technology

At the RIF Institute, researchers have optimized ultrasonic soldering using the Hielscher sonicator model UIP1000hdT for hard metal-to-steel applications. Key advancements include:

• Customized Soldering Station: A specialized setup where joining partners are inductively heated while ultrasonic waves are precisely applied.
• Process Monitoring: Advanced measurement and control systems ensure reproducible results across various combinations of steels and hard metals.
• Thorough Testing: Soldered joints undergo rigorous non-destructive imaging and mechanical testing to validate strength and reliability.

Through meticulous experimentation, the RIF institute identified critical process parameters such as soldering temperature and ultrasound activation time. The results are remarkable:

• Strength Boost: Ultrasonic soldering produced joints with strength up to 368 MPa—an increase of 347% compared to soldering without flux or ultrasound (106 MPa).
• Competitive Performance: The joint strength achieved with ultrasonic soldering rivals conventional flux-based methods.

Henrik Ulitzka, a leading researcher at RIF, highlighted the significance of these findings:
“Our tests revealed the critical influence of process parameters. By fine-tuning temperature and ultrasound activation time, we unlocked the full potential of ultrasonic soldering for hard metal-to-steel connections.”

The Future of Ultrasonic Soldering

With its ability to produce strong, flux-free joints, Hielscher sonicators for soldering represent a promising advancement for industries ranging from automotive to aerospace.
The RIF Institute’s work demonstrates that innovation and sustainability can go hand in hand, setting a new standard for soldering technology.

Design, Manufacturing and Consulting – Quality Made in Germany

Hielscher ultrasonicators are well-known for their highest quality and design standards. Robustness and easy operation allow the smooth integration of our ultrasonicators into industrial facilities. Rough conditions and demanding environments are easily handled by Hielscher ultrasonicators.

Hielscher Ultrasonics is an ISO certified company and put special emphasis on high-performance ultrasonicators featuring state-of-the-art technology and user-friendliness. Of course, Hielscher ultrasonicators are CE compliant and meet the requirements of UL, CSA and RoHs.