Ultrasonic Welding
“Ultrasonic welding is an industrial technique whereby high-frequency ultrasonic acoustic vibrations are locally applied to workpieces being held together under pressure to create a solid-state weld. It is commonly used for plastics, and especially for joining dissimilar materials. In ultrasonic welding, there are no connective bolts, nails, soldering materials, or adhesives necessary to bind the materials together.”
“For joining complex injection molded thermoplastic parts, ultrasonic welding equipment can be easily customized to fit the exact specifications of the parts being welded. The parts are sandwiched between a fixed shaped nest (anvil) and a sonotrode (horn) connected to a transducer, and a ~20 kHz low-amplitude acoustic vibration is emitted. (Note: Common frequencies used in ultrasonic welding of thermoplastics are 15 kHz, 20 kHz, 30 kHz, 35 kHz, 40 kHz and 70 kHz). When welding plastics, the interface of the two parts is specially designed to concentrate the melting process. One of the materials usually has a spiked energy director which contacts the second plastic part. The ultrasonic energy melts the point contact between the parts, creating a joint. This process is a good automated alternative to glue, screws or snap-fit designs. It is typically used with small parts (e.g. cell phones, consumer electronics, disposable medical tools, toys, etc.) but it can be used on parts as large as a small automotive instrument cluster. Ultrasonics can also be used to weld metals, but are typically limited to small welds of thin, malleable metals, e.g. aluminum, copper, nickel. Ultrasonics would not be used in welding the chassis of an automobile or in welding pieces of a bicycle together, due to the power levels required.”
(Wikipedia, Ultrasonic Welding, 2/8/2011)
Fabrication
Welding
Ultrasound /Ultrasonics
Recent US Patents
3/1/2011
7,896,994
Ultrasonic assembly method
Soccard of the European Aeronautic Defence and Space Company, France, developed a method for assembling two rigid thermoplastic material based parts. The two parts are superposed to have at least one interface zone, wherein at least one of the two parts includes one or plural energy directors, protruding, situated in the interface zone. An excited ultrasonic source is brought into contact with one of the two parts by compression. (RDC 9/12/2011)
1/18/2011
7,871,481
Method for producing a hermetic plastic zipper and a hermetic plastic zipper
Kasai, Japan, developed a method of continuously manufacturing a hermetic plastic zipper wherein the plastic zipper has a readily peelable plastic layer in a lengthwise direction of the plastic zipper, the readily peelable plastic layer is welded using ultrasonic wave so that the peeling intensity of the welded portion is within a certain range. (RDC 8/5/2011)
10/5/2010
7,807,093
Method for arranging a thermoplastic insert in a thermoplastic sandwich product
De Groot of Fits Holding , Netherlands has developed a method of welding a thermoplastic insert into a thermoplastic laminate by insert the object into a recess in the structure and heating ultrasonically. (RDC 12/20/2010)
8/17/2010
7,776,171
Arrangement and method for treatment of a material by means of an ultrasonic device.
Lehto, Nyqvist,and Yngvesson of SCA Hygiene Products ultrasonically weld together sheets including nonwovens, using a roller and a sensor to control the distancebetween the ultrasonic horn and the sheets. (RDC 10/11/2010)
Recent Journal Articles
OPTIMISING THE REGIME FOR THE HIGH-FREQUENCY WELDING OF PLASTICS WITH RESPECT TO THE DEPTH OF THE HEAT-AFFECTED ZONE
(T/63-T/66) International Polymer Science and Technology 38, #3 (2011)
Markov, Trofimov and Yulenets showed that the optimum process parameters were those ensuring a comparatively narrow depth of the heat-affected zone. The optimum depth of the heat-affected zone was determined for cases of the high-frequency welding of specimens of polyamide-610 and PVC. (RDC 6/27/2011)
Ultrasonic bond process for polymer-based anisotropic conductive film joints. Part 2: Application in chip-on-FR4 board assemblies
(449-456) Polymer Testing 30 #4 (2011)
Lin et al of Central South University, China, studied the ultrasonic flip chip bond technology for anisotropic conductive film (ACF) joints in Chip-on-Glass (COG) assemblies. The optimized ultrasonic bonding process conditions for the Chip-on-FR4 organic rigid board assemblies are obtained as: (1) the bonding time can be from 2500 ms to 3000 ms; (2) the bonding force should be over 10 N; (3) the substrate temperature should be higher than 70 °C; (4) the optimum ultrasonic power is about 2.80 W. (RDC 6/10/2011)
Interdiffusion analysis based on novel ultrasonic welding method with inserting interposed sheet
(103–108)Polymer Engineering & Science 51 #1 (2011)
Zhang and Qiu of Akita Prefectural University, Japan explained ultrasonic welding with a hauling theory of interdiffusion based on the classical reptation theory which can accelerate molecular movement and interpenetration. Hauling effect can promote the interdiffusion but has no effect on the interpenetration length. The coefficient ku is used to modify the relationship between the reptation time before and diffusion time, which can be related to the relative displacement and friction coefficient among the molecular in terms of the equations. (RDC 2/2/2011)