An In Depth
Look At The Advantages Of Crest's Patented
Ceramically Enhanced Transducer Technology
By J. Michael Goodson
discovery of the ability to substitute acoustically
superior high-tech ceramics for metals in
stacking transducers is perhaps the most
important development in ultrasonics in
the last 30 years. The high-tech ceramics
transmit sound better than even the latest
state-of-the-art metals used in traditional
transducers. Ceramically stacked high frequency
transducers are designed to meet the needs
of high-tech applications where the requirements
are submicron cleaning. They offer superior
transmission of sound at higher frequencies
which results in better contaminant removal
and reduced damage to sensitive parts. Both
general and critical cleaning applications
benefit from this advanced technology.
Should You Choose?
of chart A over chart B is clearly evident.
High-tech ceramics make possible the direct
stacking of high frequencies that before
were only available as subharmonics of metal
stacked frequencies (which derive their
primary power from the weaker first harmonics).
The stacking of a ceramic transducer to
the exact frequency results in a significantly
increased level of activity.
that even with a third harmonic direct stacking,
the Crest first harmonic (40 kHz) is stronger
than the competitor's metal stacked 40 kHz
Transmit Sound Better
acoustical speed at which sound travels
through high-tech ceramics is 63% to 125%
greater than aluminum, stainless steel or
Index: The following graph demonstrates
the comparative speed of sound going through
metals and state-of-the-art ceramics. (Acoustical
with traditional metal stacked transducers
is that solid metal is actually made up
of strands and strands of metal, which under
high magnification is actually quite porous.
In the transmission of sound waves, the
porosity becomes very significant
ceramics like alumina oxide and silicon
carbide have a composition of molecules
so minute, the porosity is near zero. Their
surfaces are so flat they can be measured
in 1,000,000 of an inch. As a result they
offer superior acoustical speed and an improved
surface interface. Thus stacking an ultrasonic
transducer with ceramics greatly enhances
the transmission of ultrasonic energy. The
near perfect transmission of sound also
reduces the amount of stress involved with
transmitting ultrasonic energy, resulting
in increased day-to-day reliability and
a much longer trouble-free life for the
system in use.
Transducers With Ceramics
into consideration the acoustic superiority,
transmitting sound into the ceramic resonator
directly before the aluminum head mass results
in more sound waves being transferred and
with greater intensity
ceramic interface allows for the near-perfect
transmission of sound
Harmonic Frequencies... The Biggest Advantage
is a third harmonic frequency?
Crystals (PZTs) used for creating ultrasonic
energy are known by their first frequencies,
the traditional Crest 40 kHz PZT for example
(see chart 1). Expand the chart and you
see an even stronger third harmonic frequency
(chart 2). Looking at the chart's full spectrum,
you will see a number of different harmonics
(see chart 3). The harmonics are based on
the number of signals that can be readily
identified with some subjective expectations
of strength which makes them useful. High-tech
ceramics make possible the direct stacking
of high frequencies that were previously
only available as sub-harmonics of metal
stacked frequencies (which derive their
primary power from first harmonics). Third
harmonics are always stronger than first
harmonics. Therefore the direct stacking
of third harmonics is highly desirable.
Fifth and higher harmonics also offer good
potential for future development.
first harmonic is 40 kHz (Chart
when you expand the chart, notice
the stronger third harmonic
If you do a complete
scan of the 40 kHz PZT you can
see a total of six (6) strong
harmonics, with 40 kHz (the
first harmonic) being the weakest.
The advantage of being able
to directly stack harmonics
other than the first gives the
user of ceramic stacked transducers
a big advantage. Metal stacking
works off the weakest harmonics.
Many Third Harmonic Possibilities Are There
For High Frequencies?
Is it possible to create
a third harmonic frequency at any point
between 100 and 350 kHz? Yes, you can create
third harmonics up to 500 kHz but it would
be cost prohibitive for the end user, as
you go above the 325 to 350 kHz range.
The Ceramic 132 kHz The Universal Transducer
Of The Future?
No. It is a great third harmonic
frequency, but with ceramic stacking you
have the luxury of having a family of third
and higher harmonics designed to meet specific
This new introduction
will challenge the megasonic
frequencies and their modest
intensity. Like other third
harmonics, it is extremely intense
for such a high frequency. With
the ceramic intensity, it is
likely to replace many of the
megasonic units on the market.
Reliability: Using the Martin
Walter power supply we expect
the transducers to last for
several years compared to most
megasonic transducers' life
expectancy of 6 to 12 months.
Reliable Are Ceramic Transducers?
more than 18 months since its introduction,
and with more than 75 ceramic 132 kHz systems
installed world wide, not one single generator/transducer
installation failure has been reported anywhere
in the world. It seems unbelievable, but
it is true. This reliability can be directly
attributed to the enhanced efficiency of
transmitting ultrasonic sound waves using
high-tech ceramics and state-of-the-art
Martin Walter AG power supplies to power
Good Are The Cleaning results?
- A disk
media manufacturing facility cut its process
time in half and got the cleanest disks
- Another disk media manufacturing
facility improved its yield by 4%. The equipment
pays for itself in 79 days.
- A slider
fab application increased yield to 100%.
- A military application using solvent
improved process time by 40%.
- An Asian
solvent/alcohol application for cleaning
& drying produced the highest HSA yield
ever recorded, with submicron specifications.