2-2 Ultrasonic Welding

ULTRASONIC WELDING

Ultrasonic Welding Lesson Objectives When you finish this lesson you will understand: • Ultrasonic Welding Definition, Characteristics, Process & Applications • Ultrasonic Power Generation • Interfacial Interactions & Dissimilar Metals Welding

Learning Activities 1. View Slides; 2. Read Notes, 3. Listen to lecture 4. Do on-line workbook

Keywords: Ultrasonic Welding, Transducer, Sonotrode, Anvil

E le c tr ic a l

S o lid S ta te W e ld in g

C h e m ic a l F r ic tio n M e c h a n ic a l

P re s s u re

U lt r o s o n ic W e ld

Definition of Ultrasonic Welding 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.

Ultrasonic Welding Process Clamping force

Process Description: • Components of Sonotrode ultrasonic welding tip system include: Vibration – Transducer – Sonotrode – Anvil

Mass

wedge Transducer

Weldment Anvil Force

Ultrasonic Welding Mechanism Clamping force

• 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 10-75 KHz welding.

Mass

wedge Transducer Sonotrode tip workpiece Anvil Force

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

Typical 1500 ultrasonic spot-type welding machine Courtesy AWS handbook

AWS Welding Handbook

100 W Lateral Drive Ultrasonic Welder

AWS Welding Handbook

Typical Ring Welding Applications Tip in Shape of Weld

AWS Welding Handbook

Attachment for Continuous Ring Welding

AWS Welding Handbook

Tip

Traversing Head for Continuous Seam Welding AWS Welding Handbook

Welding Variables

Ultrasonic Welding Variables • • • • •

Ultrasonic power Clamping force Welding time Frequency Linear Vibration Amplitude

Power Generation

Ultrasonic Welding Power Generation

Frequency converter

Electrical energy

Transducer

• 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).

Vibratory transducer

AWS Welding Handbook

Power Generation

Ultrasonic Welding 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 Requirements

E = K(HT )

3/2

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

AWS Welding Handbook

AWS Welding 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

Ultrasonic Welding Interfacial Interaction • 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 Materials Combinations

Source AWS handbook

Extreme Interpenetration Nickel Foil (top) to Gold-Plated Kovar Foil

Local Plastic Flow Dark Regions are Trapped Oxide Nickel Foil (top) to Molybdenum Sheet

Very Little Penetration, Thin Bond Line, Fiber Flow Molybdenum Sheet to Itself

AWS Welding Handbook

Comparison With Resistance Spot Weld

AWS Welding Handbook

Advantages of Ultrasonic Welding • 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.

Limitations 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.

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

Welds Can Be Made to Non-Metallic Substrate Materials Coated with Thin Layers of Metal Films Material Welded Metal Film Non-Metallic

AWS Welding Handbook

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

Applications of Ultrasonic Welding • 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

AWS Welding Handbook

Note weld progression (no weld in center)

AWS Welding Handbook

Starter motor armature with wires joined in commutator slots by ultrasonic welding Ultrasonically welded Helicopter access door. Courtesy AWS handbook

Field coil assembled by ultrasonic welding Courtesy AWS handbook

AWS Welding Handbook

Wire Bundle Placed in Jaws

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

Ultrasonic Horn Bundled Wires

Welds

First Weld Made

Cut and Second Weld Made

Ultrasonic Stitch (Clad) Welding Sonatrode

Anvil

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) Gas Generating Explosive Powder Primer

Plastic Cap Welded to Plastic Base Ultrasonic Weld

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