SUCCESS STORY – Ultrasonic Piezo Elements have Countless Applications-- Frank Möller --Ultrasonic Piezo Elements have Countless Applications
From Sonar to Welding Equipment

PI Ceramic GmbH, Lindenstraße, 07589 Lederhose, Germany
Phone +49 36604 882-0, Fax +49 36604 882-4109,Email info@piceramic.com

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SUCCESS STORY – Ultrasonic Piezo Elements have Countless Applications-- Frank Möller --Ultrasound is sound with frequencies above the range ofhuman hearing frequencies starting at around 16 kHz. These
high-frequency oscillations are used for many purposes inindustry, medical engineering and research. The spectrum
ranges from distance measurement and object recognition,
filling level or flow rate measurements, ultrasonic welding orbonding, through high-resolution material tests, up to
medical diagnosis and therapy. Piezoelectric ceramics offer
the best prerequisites for generating and detecting ultrasonicwaves. They can be cost-effectively manufactured inpractically any shape and are thus suitable as tailor-madesolutions for diverse applications.
Piezoelectric materials produce an electrical charge when aforce is applied to them (piezo effect), and they change theirdimensions when an electrical field is applied (inverse piezoeffect). In other words, they convert mechanical power intoelectrical power and vice versa; they are also referred to astransducers. While the direct piezo effect can be used forsensor applications, the inverse piezo effect lends itself
particularly to the manufacture of actuators. Their motion isexclusively based on solid state effects, and is friction- andwear-free.

Design Flexibility
With piezo components, different geometric variants andresonant frequencies can be realized in addition to thematerial selection for the respective application (Fig. 1);
components such as disc- or plate-shaped transducers inthickness vibration mode, piezoceramic rings, piezo tubes andshear elements can be delivered on very short notice on thebasis of semi-finished products in stock.
Geometries beyond the standard dimensions are alsoavailable upon request. PI Ceramic furthermore ensures
integration in the final product. This includes the contactingof the elements according to customer specifications as well
as mounting in provided components, gluing or potting of theultrasonic transducers. To measure the flow, filling level andforce or acceleration, customized sensor components are
manufactured that can be easily integrated in the respective
application.

Frequencies and Amplitudes
The creation and detection of ultrasound, for example, is aclassic piezo application because the piezo element starts tooscillate when an a.c. voltage is applied. The short response
times in the microsecond range allow for ultrasoundgeneration with frequencies of up to 20 MHz.
The piezo elements from PI Ceramic are thus suitable for amultitude of ultrasonic applications. These can be generallyclassified in mainly sensor applications in the high-frequency
range and power ultrasound where the energy densities arehigher.
As a result, the piezo elements accomplish considerable
mechanical work, e. g. in crushing kidney stones andremoving dental plaque, with cleaning baths as well as inindustrial welding or bonding. The typical frequencies ofpower ultrasound are between 20 and 800 kHz.

PI Ceramic GmbH, Lindenstraße, 07589 Lederhose, Germany
Phone +49 36604 882-0, Fax +49 36604 882-4109,Email info@piceramic.com

Fig. 1

Many variants of piezo elements are possible, e.g. tubes, disks,benders, shear elements or transducers, which makes it easy toadapt them to the respective application

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SUCCESS STORY – Ultrasonic Piezo Elements have Countless Applications-- Frank Möller --Application Examples fromPractice

The dosing amounts range from the microliter and nanoliter
range to the picoliter range. Here, piezo-based microdosing
systems stand out due to their very small dimensions, theirlow energy consumption and low costs.

The range of applications for piezoceramic components isdiverse. The direct as well as the inverse piezo effect is usedin ultrasonic measurement of propagation times. A typicalapplication for propagation time measurement is themeasurement of filling levels. The piezo transducer works as atransmitter and a receiver.

The same also applies to devices for aerosol generation (Fig.
3), in which a piezo element excites a diaphragm to ultrasonicvibrations. The frequency is approx. 35 kHz. Due to theresulting pressure changes at the diaphragm, the fluid ispressed through the holes in the diaphragm and thereby
aerosolized.

It transmits an ultrasonic pulse that is reflected by the filling
medium. The propagation time required is a measure of thedistance travelled in the empty part of the container. Flowmeasurement is based on the propagation time difference
during alternate transmission and receiving of ultrasonicpulses in and against the flow direction (Fig. 2).

Fig. 3Fig. 2The propagation time measurement is based on the alternate
transmission and receiving of ultrasonic pulses in and against thedirection of flowHere, two piezo transducers operating as both transmitterand receiver are arranged diagonally to the direction of flowin an acoustic path. With the Doppler effect, the phase andfrequency shift of the ultrasonic waves which are scatteredand reflected by particles of liquid are evaluated.

The piezo ring is directly glued to the metal ring of thediaphragm. When an a.c. voltage is applied, the piezo element
oscillates with a frequency of approx. 35 kHz (Pari Pharma/PI)

Further interesting applications are found in the area ofpower ultrasound. In industry, ultrasonic welding – primarilyof plastics – and the bonding of wires in chip manufacturing
are considered a cost-effective, efficient solution. Anotherindustrial application is ultrasonic cleaning, also in
microsystems technology and semiconductor manufacturing(Fig. 4).

The frequency shift between the reflected wavefront emitted
and received by the same piezo transducer is proportional to
the flow speed. Many other tasks can be effectively solved ina similar way, such as e.g. object recognition or highresolution material tests.
Piezo elements have also become indispensable in medicalengineering. In addition to propagation time measurements
such as in air bubble detection, typical applications are inpumping and dosing.

PI Ceramic GmbH, Lindenstraße, 07589 Lederhose, Germany
Phone +49 36604 882-0, Fax +49 36604 882-4109,Email info@piceramic.com

Fig. 4High-frequency ultrasonic cleaning systems offer effective
support for cleaning, etching and development processes(Sonosys Ultraschallsysteme GmbH)

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SUCCESS STORY – Ultrasonic Piezo Elements have Countless Applications-- Frank Möller --Today, ultrasonic instruments allow minimally invasive
operation techniques as well as plaque removal (Fig. 5).
Kidney stones can also be crushed with high-energy shockwaves.

Fig. 5

Each oscillation leads to an over-pressure phase or lowpressure phase in the fluid, depending on whether thetransducer expands or contracts. During the low-pressure
phase, due to the fluid's limited tensile strength, small
cavities form in the fluid; these so-called cavitation bubbles
implode during the over-pressure phase. When the cavitation
bubbles implode at the surface to be cleaned, dirt particles
are removed.

Instrument for ultrasonic plaque removal (OEM product). The
piezo disks can be clearly seen

Ultrasonic Cleaning inMicrosystems Technology andSemiconductor Manufacturing
For micro-level cleaning systems, it is a challenging task not todamage tiniest structures on the surface to be cleaned.
Ultrasonic systems that work with operating frequencies
between 700 kHz and 3 MHz are best suited for this (Fig. 6).
With these systems, dirt particles can be removed reliably inthe nanometer range without damaging the sensitive surfaces
by a too high pressure or too high temperatures. The
functional principle is easy to understand:The ultrasonic system consists of three components: The
electronic
ultrasonicgenerator,
theultrasonicoscillator/transducer, a piezo element, and an appropriate
cleaning fluid, selected according to the cleaning task.

Fig. 6

PrincipleofMegasonicUltraschallsysteme GmbH)cleaning(Image:Sonosys

The ultrasonic generator converts the supplied alternating
current of 50 Hz or 60 Hz respectively to a frequency that
corresponds to the operating frequency of the transducer.
The transducer then converts the released electric energy
into mechanical acoustic oscillations causing the surrounding
fluid to oscillate.

PI Ceramic GmbH, Lindenstraße, 07589 Lederhose, Germany
Phone +49 36604 882-0, Fax +49 36604 882-4109,Email info@piceramic.com

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SUCCESS STORY – Ultrasonic Piezo Elements have Countless Applications-- Frank Möller --Author

Dipl.-Phys. Frank Moeller, Sales at PI Ceramic

PI Ceramic in Brief
PI Ceramic is considered a global leading player in the field ofpiezo actuators and sensors. The broad range of expertise inthe complex development and manufacturing process offunctional ceramic components combined with state-of-theart production equipment ensure high quality, flexibility andadherence to supply deadlines.
Prototypes and small production runs of custom-engineered
piezo components are available after short processing times.
PI Ceramic also has the capacity to manufacture mediumsized to large series in automated lines. PI Ceramic, asubsidiary of Physik Instrumente (PI) GmbH & Co. KG, islocated in the city of Lederhose, Thuringia, Germany.

PI Ceramic GmbH in Lederhose, Thuringia, GermanyPI Ceramic GmbH, Lindenstraße, 07589 Lederhose, Germany
Phone +49 36604 882-0, Fax +49 36604 882-4109,Email info@piceramic.com

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