2-2 Ultrasonic Welding

ULTRASONIC WELDING

SolidState

Welding

Electrical

Chemical

Mechanical

Friction

PressureUltrosonic

Weld

A solid state welding process in which coalescence is produced at the faying surfaces by the application of high frequency vibratory energy while the work pieces are held together under moderately low static pressure.

Definition of Ultrasonic Welding

Ultrasonic Welding Process

Process Description:

• Components of ultrasonic welding system include:– Transducer

– Sonotrode

– Anvil

Anvil

Mass

Sonotrode tip

Clampingforce

wedge Transducer

Force

WeldmentVibration

• A static clamping force is applied perpendicular to the interface between the work pieces.

• The contacting sonotrode oscillates parallel to the interface.

• Combined effect of static and oscillating force produces deformation which promotes welding.

Anvil

Mass

Sonotrode tip

Clampingforce

wedge Transducer

Force

workpiece

Ultrasonic Welding Mechanism

10-75 KHz

Process Variations

• Spot Welding• Ring Welding• Line Welding - Linear Sonotrode• Continuous Seam Welding - Roller Sonotrode• Microminiature Welding

Typical 1500 ultrasonicspot-type welding machine

Courtesy AWS handbook

AWS Welding Handbook


100 W Lateral DriveUltrasonicWelder


Typical Ring Welding ApplicationsTip in Shape of Weld

AWS Welding HandbookAttachment for Continuous Ring Welding


Traversing Head for Continuous Seam Welding

Tip

• Ultrasonic power

• Clamping force

• Welding time

• Frequency

• Linear Vibration Amplitude

Welding Variables

Ultrasonic Welding Variables

Ultrasonic Welding Power Generation

• Electrical power of 60 Hz is supplied to the frequency converter.

• The frequency converter converts the required 60 Hz signal to the welding frequency (from 10 to 75 kHz).

Electrical energy

Frequency converter

Vibratory transducer

Tran

sdu

cer

Power Generation

• Frequency is transformed to vibration energy through the transducer.

• Energy requirement established through the following empirical relationship.– E = K (HT)3/2

– E = electrical energy

– H = Vickers hardness number

– T = thickness of the sheet

Electrical energy

Frequency Converter

Vibratory transducer

Power Generation

Ultrasonic Welding Power Generation

2/3)HT(KE

Where:E = electrical energy, W*s (J)k = a constant for a given welding systemH = Vickers hardness number of the sheet T = thickness of the sheet in contact with the sonotrode tip, in. (mm)

Power Requirements

The constant “K” is a complex function that appears to involve primarily the electromechanical conversion efficiency of the transducer, the impedance match into the weld, and other characteristics of the welding system. Different types of transducer systems have substantially different K values.

Source AWS handbook

Sonotrode Tip and Anvil Material

High Speed Tool Steels Used to Weld• Soft Materials• Aluminum• Copper• Iron• Low Carbon Steel

Hardenable Nickel-Base Alloys Used to Weld• Hard, High Strength Metals and Alloys

• Localized temperature rises resulting from interfacial slip and plastic deformation.

• Temperature is also influenced by power, clamping force, and thermal properties of the material.

• Localized Plastic Deformation

• Metallurgical phenomena such as recrystallizing, phase transformation, etc..... can occur.

Ultrasonic Welding Interfacial Interaction

Source AWS handbook

Ultrasonic Welding Materials Combinations

Extreme InterpenetrationNickel Foil (top) to Gold-Plated Kovar Foil

Local Plastic FlowDark Regions are Trapped OxideNickel Foil (top) to Molybdenum Sheet

Very Little Penetration, Thin Bond Line, Fiber FlowMolybdenum Sheet to Itself


AWS Welding HandbookComparison With Resistance Spot Weld

• No heat is applied and no melting occurs.

• Permits welding of thin to thick sections.

• Welding can be made through some surface coatings.

• Pressures used are lower, welding times are shorter, and the thickness of deformed regions are thinner than for cold welding.

Advantages of Ultrasonic Welding

• The thickness of the component adjacent to the sonotrode tip must not exceed relatively thin gages because of power limitations of the equipment.

• Process is limited to lap joints.

• Butt welds can not be made because there is no means of supporting the workpieces and applying clamping force.

Limitations of Ultrasonic Welding

Other Process Variations• Ultrasonic Welding of Non-metallic• Ultrasonic Plastic Welding

Welds Can Be Made to Non-MetallicSubstrate Materials Coated with Thin

Layers of Metal Films

Non-Metallic

Metal Film

Material Welded

Ultrasonic Welding of Plastics

• Advantages– Fast

– Can spot or seam weld

• Limitations– Equipment complex,

many variables

– Only use on small parts

– Cannot weld all plastics

0.1.1.2.5.T25.95.12

• Assembling of electronic components such as diodes and semiconductors with substrates.

• Electrical connections to current carrying devices including motors, field coils, and capacitors.

• Encapsulation and packaging.• Plastic parts

Applications of Ultrasonic Welding

AWS Welding HandbookNote weld progression (no weld in center)

Starter motor armature with wiresjoined in commutator slots by

ultrasonic weldingUltrasonically welded Helicopter

access door.Courtesy AWS handbook

Field coil assembled by ultrasonic welding

Courtesy AWS handbook

UltrasonicHorn

First Weld Made Cut and Second Weld Made

Bundled Wires

Welds

Ultrasonic Tying Tool

Metal Tape Fed Around bundle of Wires and welded once, then cut and welded again.

Wire Bundle Placed in Jaws

Ultrasonic Stitch (Clad) Welding

Anvil

Sonatrode

Louks, et al “Ultrasonic Bonding Method” US Patenet 6,099,670 Aug. 8, 2000

Ultrasonic Welding of Eraser Holder on Plastic Pencil

Coinon, A, Trajber, Z, “Pencil Having and Eraser-Holding Ferrule Secured by Ultrasonic Welding” US Patent 5,774,931 July 7, 1998

Explosive Gas Generator For Auto Air Bag(Plastic Ultrasonic Weld)

Plastic Cap Welded to Plastic Base

Gas Generating Explosive Powder

Primer

Ultrasonic Weld

Avory, et al “Electrical Initiator” US Patent 5,763,814 June 9, 1998.

2-2 Ultrasonic Welding

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