Photos courtesy of Kyocera, unless otherwise indicated.
Advanced ceramics offer engineers a unique set of
physical, chemical, electrical and thermal characteristics that place them
among the "miracle materials" of modern technology. Simply put,
ceramics possess a full range of properties that metals lack, and vice versa.
Such mutually exclusive material properties produce a
common engineering dilemma: we are often confronted with the need to combine
the characteristics of metals and the characteristics of ceramics into a single
component. Though this challenge may be akin to mixing oil and water, a
solution can often be obtained by metallizing
material-attaching a metal alloy to a ceramic surface through a process of
chemical or mechanical bonding. Done properly, metallized ceramics can offer
engineers the best of both material worlds in a wide range of challenging
The basic technologies for metallizing ceramic have been
known for more than 60 years. In today's society of rapid change, this long history
may suggest a mature technology in declining demand. In fact, the opposite is
true. Many of today's hottest and most promising fields depend on metallized
ceramics. Examples include the revolution in wireless communication, high-speed
optical Internet technology, advanced medical diagnostic equipment, implantable
medical devices, scientific test and measurement equipment, and even research
into high-energy particle physics and nuclear fusion energy.
Suppliers of metallized ceramic solutions can provide a
range of products and services, including bare ceramics and substrates for a
variety of applications, metallized ceramics for customers that attach metal
assemblies via brazing or welding, brazed ceramic sub-assemblies for customers
who weld or braze the component into a final assembly, and full-service
metallized and brazed solutions for customers who prefer to outsource all
processing. In all cases, metallized ceramic components offer critical,
high-added-value performance characteristics that may otherwise be unattainable
using conventional material technologies.
Selective Electrical Conductivity
LD-MOS device package for wireless communications infrastructure.
Although ceramic materials are electrically non-conductive, metallization allows electrical contacts to be printed onto a ceramic surface. This property is invaluable in the field of passive electronic components, where the ability to metallize ceramic has created a revolution in leadless, "surface-mountable" capacitors, resistors, filters and other devices. As a result, new generations of electronic equipment can occupy the same footprint while offering significantly greater functionality; or, conversely, equipment offering equivalent functionality can be made significantly smaller. These leadless devices have been among the main drivers allowing manufacturers to miniaturize all types of electronic equipment, from palmtop computers to cellular phones.
In addition to basic electrical contacts, specially formulated metallic inks can be applied to a ceramic surface using an automated screen-printing process to produce high-precision circuit patterns. After firing the ceramic component, these printed areas can be electroplated with nickel or gold for outstanding electrical conductivity, while maintaining the material's electrical insulating properties in the unprinted areas. As a result, metallized and multilayer ceramics play an indispensable role in semiconductor packaging, including many of the industry's most demanding applications.
The metallization of ceramic can also permit resistive circuitry to be printed onto a ceramic substrate to create an effective heating element in applications ranging from gas igniters to diesel glow plugs.
Metallized ceramic chambers used in synchrotron radiation facility.
Metallized ceramics can be designed for high-voltage
feed-through applications involving up to 100 kV (100,000 volts). The numerous
applications for this feature include equipment for high-energy physics
research, where particle accelerators are facilitating new discoveries in many
fields of science (see the "Metallized Ceramics at Japan's
SPring-8 Synchrotron Lab" sidebar). In addition, high-voltage metallized
ceramic components are also widely used in medical diagnostic and radiation
therapy equipment, such as that used in treating many cancers; in mass
spectrometers; and in a wide range of other test and measurement equipment.
Multilayer ceramic "multi-chip module" semiconductor package.
High-performance semiconductors, laser devices and
crystal units require complete protection from moisture, dust and gases. In
housing these devices, hermetic seals are generally recognized as the best form
of protection against the external environment. Plastics and epoxy
materials-widely used for components in low-cost consumer equipment-are
inherently moisture-permeable, leading to reliability issues over time.
In contrast, the extreme physical and chemical stability
of advanced ceramics allows them to offer extremely durable hermetic sealing,
both for these devices and for a full range of other critical applications that
require ultra-high vacuum conditions. Metallized ceramics play an essential
role in such applications, including optical communications infrastructure,
where 25 years of trouble-free duty is the industry standard.
Metallized ceramic isolator flange used in nuclear fusion research.
As electronic technology advances, so does demand for
miniaturization, integration and operating speed, resulting in an unprecedented
need for thermal management. In fact, thermal limitations are now a major
limiting factor in the performance of advanced electronic equipment. Ceramics
generally offer better thermal conductivity than other materials, and
metallization can enhance this performance further by facilitating the
attachment of metal heat sinks to transmit very high levels of heat away from
Mini-DIL package for optical communications infrastructure.
As a general rule, engineers employ advanced ceramics
only where the material's unique properties are necessary to achieve specific
performance goals. At some point, the ceramic component must interface with
another component within a system, and some kind of attachment or joint is
necessary at this point of interface.
Ceramic materials are inherently difficult to join,
either to themselves or to other materials, which limits some potential
applications. Fortunately, this challenge can be overcome through
metallization, which allows durable metal mounting hardware to be soldered,
brazed or welded onto a metallized ceramic component-essentially moving the
ceramic away from the direct point of interface.
A Promising Future
Metallized ceramics have a promising future in many
cutting-edge technologies where rising performance goals require a
super-material. In communications, for example, the diffusion of wireless phone
technologies is allowing developing regions of the world to adopt 21st century
infrastructure at relatively low costs.
In developed regions, the expansion of broadband
technology using fiber optic networks is already allowing low-priced,
high-speed Internet access to be bundled with TV and phone services. Future
advancements may make the typewritten e-mail message obsolete in favor of video
messaging, and enable full-length feature movies to be downloaded to your home
theater system within seconds.
New medical diagnostic equipment, including advanced X-ray
systems, can provide detailed, 3-D views inside a patient for better analysis
of treatment options before any incisions are made. Implantable devices like
pacemakers, defibrillators, neurostimulators and drug delivery devices are
offering life-saving medical solutions to millions of people each year.
High-energy particle physics research is helping to
advance the most exciting realms of science. And continued research into
nuclear fusion offers the long-term potential for a limitless source of affordable,
renewable energy, with none of the nuclear waste associated with today's
The introduction of metallized ceramics into so many
fields provides an example of the broad opportunities available for the
advanced ceramics industry as a whole.
For additional information regarding metallized
ceramics, contact Kyocera Industrial Ceramics Corp. at 220 Davidson Ave., Suite
104, Somerset, NJ 08873; (732) 563-4340; e-mail email@example.com;
or visit www.kyocera.com.
SPring-8. Photo courtesy of Japan Science and Technology
SIDEBAR: Metallized Ceramics at Japan's SPring-8 Synchrotron Lab
A synchrotron radiation facility consists of an injector,
which generates an electron beam and accelerates electrons, and a storage ring,
where electrons are accumulated. SPring-8, located in Japan's Harima
Science Garden City, is the world's largest "third generation"
synchrotron radiation facility. It features 62 beamlines and an 8 billion
electron-volt (8 GeV) storage ring measuring 1.4 kilometers in diameter.
Researchers worldwide use SPring-8 for exciting work in materials science,
spectroscopic analysis, earth science, life science, environmental science and
Beam positioning monitor.
The electron beams that circulate at near-light-speed
inside SPring-8's massive storage ring need to run smoothly and efficiently at
all times. To facilitate this, a minute electrical current generated by the
flowing electron beams is constantly measured and analyzed to continuously
correct the beam's position in the center of the ring's cross-section. This is
accomplished through the use of 1300 metallized ceramic beam positioning
monitors (BPMs)-four at each of 325 locations within the ring. Each BPM
measures an electrical signal equivalent to a 25-picosecond pulse, requiring
both excellent high-frequency operating characteristics and strong hermetic
sealing to maintain the super-high-vacuum environment within the ring.