fundamentals of metals

ULTRASONIC WELDING TECHNOLOGY

FUNDAMENTALS OF METALS

02 | 03 Herrmann Ultraschall | Ultrasonic welding technology – FUNDAMENTALS OF METALS

Ultrasonic welding technology. For nonferrous metals.

Herrmann Ultraschall is a world-leading company in the field of ultrasonic welding. For our custom-ers, we assume both the role of consultants and application solution providers with regards to the ultrasonic joining of nonferrous metals. This brochure provides practical advice and introductory information for the welding of nonferrous metals by means of ultrasonics.

In addition to leading-technology products, we provide excellent application consulting to solve joining tasks, taking economical aspects into account. Please note that this brochure is intended to be an introduction to joining technology for nonferrous metals using ultrasonics and in no way replaces application-specific consulting given by our experts.

02 | 03

Ultrasonic welding of nonferrous metals, such as copper and aluminum, is an established joining technology and is suitable for many applications in the fields of automotive, consumer products and electronics industry. Due to ris-ing demands for lithium-ion batteries, the use of ultrasonic welding for pre-welding and main welding of anode and cathode foils has significantly increased. The process can be implemented as a manual work station or incorporated as an automated process into production lines.

The advantages offered by this process are:

�High strength

� Short cycle times

� Low energy consumption

�No consumables

In the welding of metals, process stabilization, particle minimization and the service life of tools play a major role. Setting up such a process requires tactical planning and consideration since the aspects of application, materials, and production environment must be considered.

Generation of ultrasonic vibrationsThe ultrasonic generator converts the supply voltage into a high frequency voltage at a frequency of 20 or 35 kHz. This electrical signal is converted into mechanical vibra-tions by the converter using the inverse piezoelectric effect. The generated mechanical vibrations increase by means of the booster and sonotrode, and are applied to the materials to be welded. Through a defined force, the sonotrode, which is the active weld tool, introduces trans-verse vibrations through the upper joining part into the joining area between the parts to be welded.

The anvil is the passive counterpart to the sonotrode and provides the rigid, fixed surface required for welding. The lower joining part is held in the anvil and does not move. The sonotrode’s working face must be knurled, as other-wise the top joining part would not couple, which is to say, no relative motion would be generated between the parts to be welded. Under the effect of force and mechanical vibration, the metal surfaces are activated and a molecular bonding joint is obtained.

Generator

Converter Booster Sonotrode

Vibration direction

Weld force

Anvil

Application


Ultrasonic welding technology. Bonding below the melting point.

Physical mechanismUltrasonic welding is used to join conductive nonferrous and precious metals. Through its knurled surface, the sonotrode transfers the vibration into the upper joining part. The lower joining part remains fixed by the structure of the anvil. This results in relative motion between the upper and the lower joining parts. This relative transversal movement of the joining parts results in friction and thus plastic deformation of the rough peaks on the surface.

The three main stages of formation of a molecular bonding joint by means of ultrasonics are:

1) Shearing off the rough peaks through relative move-ment of the joining parts – initial plastic deformation.

2) The ultrasonic vibration causes dispersion of impurities inclusions/oxides and further deformation of the rough peaks. This results in increased metal-metal contact and formation of weld zones, also referred to as mi-cro-welds.

3) Further ultrasonic vibration results in enlargement of the contact surface and thus larger weld zones.

The decisive advantage of ultrasonic welding is no heat is introduced into the weld joint. The solid state weld is created at temperatures far below the melting points of the metals, due to the relative motion of the parts to be welded.

weldable

individual verification required

not weldable

Ag

Ag

Al

Au

Cu

Fe

Ni

Pb

Sn

Al Au Cu Fe Ni Pb Sn

Weld force

Sonotrode

Weld zoneAnvil

Application

Vibration direction

04 | 05

Application variety. One process, endless possibilities.

Terminal-terminalIn terminal-terminal welding, metal sheets with thickness-es of up to 3 mm are welded to each other. The require-ments for force and power are significantly higher here. They are used for transmission of high current loads, for example in battery management systems or high-power contacts.

FoilsUltrasonic welding of foils is typical in the field of battery cell production. For this purpose, foils of thicknesses be-tween 6 µm and 0.3 mm are welded. The number of foils may vary from two to up to 160 layers that are simultane-ously welded.

Application examples are prismatic cells, pouch and cy-lindrical cells.

Cable-terminalIn modern vehicles, cables and connectors assembled with ultrasonics have become indispensable. The range of cable cross-sections is between six and 85 mm². The conductor materials used are copper and aluminum. One of the most frequent applications is the transmission of high power within the cable harness.


Precise parameters. For optimal reproducibility.

Process parametersThe major benefit of the ultrasonic welding process is the result of the large variety of parameters that may be used for precise setting of the process, evaluation, and quality control.

Optimal parameters can help you achieve:

� Optimum loading of the material for strongest possi-ble welding without damage

� Easy reproducibility and consistent weld results

The major parameters of the ultrasonic welding process are:

� Frequency

� Amplitude

�Weld force

� Switch-off criterion (weld time, energy, weld depth ...)

The welding procedure can be graphically illustrated. The visualization on the controller and user interface shows deviations in the procedure and allows for process opti-mization. The conditions for good welds include sufficient relative movement between the joining parts and stable forces.

Weld process sequence

Close tool

Force

Amplitude

Power

Ultrasonic on Ultrasonic off t

Distance

Build-up weld force

Ultrasonic active Switch-off criteria reached

Open tool

06 | 07

Optimum process control. For reproducible quality.

Process monitoringThe controller monitors the process parameters and graphically displays them. This graphical display of parameters on the screen, which includes amplitude, energy, weld depth, and weld force, is an important instrument to ensure stable and reproducible processes. A process window must be determined for each application to balance out material and production tolerances.

Process visualization

Ultrasonic welding parameters

Wel

din

g m

od

e

(sw

itch

-off

)

Trigger force Weld force Time Energy Distance RPNDistance absolute Amplitude

Time programmed programmed setmin. limit max. limit

min. limit max. limit


programmed

Energy programmed programmedmin. limit max. limit

setmin. limit max. limit


programmed

Distance RPN* programmed programmedmin. limit max. limit


setmin. limit max. limit

programmed

Distance absolute programmed programmed




set programmed


Ideal tool geometry. For the strictest requirements.

The structures of the sonotrode and anvil have a major impact on the quality of the weld result and on process stability.

Factors influencing the weld result:

� Structure: (truncated) pyramids, semi-spheres, lines

� Alignment of the structure

� Thickness of the material (thicker material requires coarser structures)

Standard

Equal tension of the upper foils on the entire front side

Rotation

Tension level of the upper foils reduced through 45 ° rotation

41% greater area for force distribution

Contour sonotrodes

Terminal WireBattery

08 | 09

Highly efficient. Optimum tool design.

The acoustical components of the system are the stack and the anvil. The purpose of the stack is to generate and transform mechanical vibration and introduce it into the application. The anvil is the counterpart that supports the lower weld part and prevents it from vibrating.

While the converter and the booster are standard components, the sonotrode and the anvil are individually adapted to the requirements of the application.

SonotrodeRequirements for the sonotrodes

� Frequency matching of the longitudinal modes for operating frequency

�Optimal strength at the required operating amplitude

� Low internal heat-up through intrinsic damping

�Wear/service life

�Reproducibility

� Transformation of the input amplitude to the required operating amplitude

The FEM calculation method ensures fast and precise tool development to adaptation to the operating frequency, tensions and vibration shapes are optimized such that the perfect tool is obtained for the respective application. The correct software tool for simulation and the quality of the input parameters are important.

AnvilRequirements for the anvil

� The weld forces must be reliably absorbed

� Prevention of resonances within the range of the operating frequency

�Wear resistance

While the sonotrode initiates vibration in the joining part,the purpose of the anvil is to prevent the parts to be welded from vibrating. This ensures initiation of a relative movement between the joining partners. While the sono-trode is intended to vibrate at the operating frequency, the anvil is supposed to be particularly inert and difficult to move and vibrate. With the help of the FEM calcula-tion, intrinsic resonances of the anvil within the range of the operating frequency are prevented.

Modal analysis of a sonotrode top: Deformation plot bottom: Tension plot

Modal analysis of an anvil, including the anvil carrier

Innovative welding technology. Leading in speed and precision.

Herrmann intelligent Spotwelder Wire and Terminal

Herrmann intelligent Spotwelder Battery

The intelligent spot welders of the Herrmann HiS series

HiS VARIO BHiS VARIO B ultrasonic welding systems provide the ideal platform for a broad spectrum of battery-related applications all over the world. Quality control is possible through evaluation of the weld process parameters and process mon-itoring. The design as a flexible modular system ensures fast and simple inte-gration into various production lines.

� Low space requirements

� Process visualization and process stability

� Easy integration into production lines

HiS VARIO W The modular concept of the HiS VARIO W welding machine ensures flexi-ble production strategies thanks to easy replacement of ultrasonic tools and equipment. Through consistent pursuit of a clean design strategy, the machine is highly ergonomic and soiling/contamination is significantly reduced.

�Modular and compact machine design

� Encoded equipment for automated program selection

� Full accessibility from the front

HiS VARIO THiS VARIO T ultrasonic welding machines by Herrmann Ultraschall ensure added value with regard to process stability and compliance with customer re-quirements. Graphic visualization in the VARIO controller ensures optimization of the weld process, i.e. through adjustable force profiles. This leads to highest weld quality for customized weld applications.

�Weld process visualization

�Quality monitoring

�Modular adjustment options


10 | 11

Continuous support from the beginning. ULTRASONIC ENGINEERING.

The teams of experts at Herrmann Ultraschall will support you during every phase of your project. This includes joint design discussion, component design, pre-production prototype welding in application laboratories, weld parameter definition for verification of the required component properties, training/instruction services, and after-sales services. Close cooperation with the customer and efficient prod-uct development is the primary focus.

Ultrasonic laboratory Application consulting

� Early support for component design

� Support and direction for designing the weld geometry

� Principle testing for feasibility

Application optimization

�Common trials and tests with the customers

� Determination and optimization of tooling profiles and process limits

� Verification of trial/test results with the help of microscopy, tensile tests, sealing tests, burst tests, high-speed cameras, and microtome cuts

�Complete documentation of feasibility test results

Trainings and seminars�Beginner and expert seminars

�Hands-on user training

� Trainings on site or at our local facilities

�Customer-specific trainings

Technical project management� Consistent implementation of customer requirements and test results in design concepts

� 3D supported collision analysis

� FEM supported sonotrode design

�Mechanical and electrical interface definition

� Consulting on integrating the weld process into the manufacturing process

Tech-Center on-site� Customer-oriented support for feasibility analyses

� Ultrasonic laboratories are strategically located in the major metal markets worldwide

� Experienced and native-speaking application specialists

After-sales service� Optional 24-hour service hotline

� On-site service in the respective languages through our Tech-Center network.

� Preventative maintenance and service measures

Headquarters Tech-Center Local Sales Office

7000

997

01/

20

EN

G

250

Tec

hnic

al c

hang

es re

serv

ed.

FIRST CLASS TECHNOLOGY. WORLDWIDE. 27 LOCATIONS IN 20 COUNTRIES.

North America Headquarters Herrmann Ultraschall, Inc.1261 Hardt Circle · Bartlett, IL 60103, USAwww.herrmannultrasonics.com

Global HeadquartersHerrmann Ultraschalltechnik GmbH & Co. KGDescostraße 3 –11 · 76307 Karlsbad, Germanywww.herrmannultraschall.com

China Headquarters Herrmann Ultraschall (Taicang) Co. Ltd.Build 20-B, No. 111, North Dongting Road, Taicang, Jiangsu Province, China · www.herrmannultrasonic.cn

Japan Headquarters Herrmann Ultrasonic Japan CorporationKOIL 503-1, 148-2 Kashiwanoha Campus, 178-4 Wakashiba, Kashiwa City, Chiba 277-8519 · www.herrmannultrasonic.co.jp

fundamentals of metals

Documents