Applications explained
MultiLayer Ceramic Capacitors (MLCC)
MultiLayer Ceramic Capacitors can store large amounts of energy in a minimum of space. They are insensitive to temperature, moisture and polarity reversal. These ceramic components make ideal surface mount devices (SMDs) and are eminently suitable for telecommunications, automotive and entertainment electronics applications.
Low Temperature Cofired Ceramic (LTCC) (HTCC)
The Low Temperature Cofired Ceramic (LTCC) technology can be defined as a way to produce multilayer circuits with the help of single tapes, which are to be used to apply conductive, dielectric and / or resistive pastes on. These single sheets have to be laminated together and fired in one step all. This saves time, money and reduces circuits dimensions. An other great advantage is that every single layer can be inspected (and in the case of inaccuracy or damage) replaced before firing; this prevents the need of manufacturing a whole new circuit. Because of the low firing temperature of about 850°C it is possible to use the low resistive materials silver and gold instead of molybdenum and tungsten (which have to be used in conjunction with the HTCCs).
Multilayer Varistors (MLV)
Multilayer Varistors or MLV's are tiny ceramic chips terminated on each end. They can be used to protect circuits from electrostatic discharge and other high voltage surges. As with disc varistors, the purpose of an MLV is to protect an electronic circuit by carrying away unwanted high voltage spikes.
Multilayer inductors (MLI)
Multilayer inductors (MLI) are manufactured using semiconductor material typically based on ferrites with inorganic dopants (a black, nonconductive, brittle magnetic material). MLI´s are inductors constructed by layering the coil between the layers of core material. When using tape cast ceramic layers, holes are punched and filled with the conductor used to make the interconnection between the spiral´s circles screen printed in the subsequent layers. The coil normally consists of a bare metal material (no insulation). This technology is normally referred to as “non-wirewound”. Two technologies exist to manufacture these components: the so called wet technology using screen printing and the dry technology using tape casting. A comparison can be found in the paper by Oostra and Höppener in 2001 which can be downloaded on this website.
The inductance value can be made larger by adding additional layers for a giving spiral pattern. These are all ploys to multiply the inductance of a given coil by the "permeability" of the core material. Packing methods for chip inductors include tape reel, tray, tube, or bulk pack. Common applications include common mode choke, general purpose, high current, high frequency, power inductor, and RF choke.
Thermistors (PTC/NTC)
PTC and NTC thermistors are ceramic components whose resistance varies with temperature. They are mainly used to measure and control temperature in automotive electronics and domestic appliances. Thermistors also protect electric motors against overload.
Piezo Actuators
Piezo Actuators are key components of piezoelectric fuel injection systems in diesel and gasoline engines. With their low mass and short switching times, piezo actuators are far superior to the conventional solenoid valves used to actuate the injection needles in fuel injection valves. Thanks to piezo technology, the injection process can be divided into seven injection events at four times the switching speed. Whereas solenoid valves have a fixed displacement, that of a piezo actuator can be varied. Key benefits are lower fuel consumption, and reduced exhaust and noise emissions. The piezo actuator uses the inverse piezo effect. If a voltage is applied to a piezoelectric crystal, its dimensions change. But this effect cannot be exploited and no significant displacement obtained until several hundred layers of piezoelectric material are superimposed. Depending on type, piezo actuators contain up to 1,800 ceramic layers in a stack up to 45 mm high. This results in a displacement of 65 micrometers – enough to operate the needle in the injection nozzle and inject fuel into the cylinder.
Solid Oxide Fuel Cells
Solid Oxide Fuel Cells are devices that convert chemical energy into electrical and thermal energy, combining oxygen and hydrogen. They operate at high temperatures (600...1000°C). Single SOFC cells consist of three main components: two porous electrode layers separated by a dense, oxygen-conducting electrolyte layer (the structure thickness is less than 1 mm). The cathode receives oxygen (usually from hot air), and the anode receives hydrogen, often derived from a hydrocarbonyl fuel. The oxygen ions, created by surface reactions in the cathode, migrate from the cathode to the anode through the electrolyte and combine with hydrogen. Water and free electrons are produced and a current flow is created through an external load. The most common electrolyte material is Yttria Stabilized Zirconia (YSZ); the cathode is generally made up of porous perovskite-structured ceramics. The currently preferred SOFC anode material is a porous Ni-YSZ cermet.
The SOFC cells fabrication process consists of:
- tape casting of the anode and cathode layers
- deposition of the electrolyte on either the cathode or the anode layer
- co-sintering of the stack.
Solar cells
Solar cells convert sunlight directly into electricity. Solar cells are often used to power calculators and watches. They are made of semiconducting materials similar to those used in computer chips. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity. This process of converting light (photons) to electricity (voltage) is called the photovoltaic (PV) effect.
Solar cells are typically combined into modules that hold about 40 cells; about 10 of these modules are mounted in PV arrays that can measure up to several meters on a side. These flat-plate PV arrays can be mounted at a fixed angle facing south, or they can be mounted on a tracking device that follows the sun, allowing them to capture the most sunlight over the course of a day. About 10 to 20 PV arrays can provide enough power for a household; for large electric utility or industrial applications, hundreds of arrays can be interconnected to form a single, large PV system.
Thin film solar cells use layers of semiconductor materials only a few micrometers thick. Thin film technology has made it possible for solar cells to now double as rooftop shingles, roof tiles, building facades, or the glazing for skylights or atria. The solar cell version of items such as shingles offer the same protection and durability as ordinary asphalt shingles.
Some solar cells are designed to operate with concentrated sunlight. These cells are built into concentrating collectors that use a lens to focus the sunlight onto the cells. This approach has both advantages and disadvantages compared with flat-plate PV arrays. The main idea is to use very little of the expensive semiconducting PV material while collecting as much sunlight as possible. But because the lenses must be pointed at the sun, the use of concentrating collectors is limited to the sunniest parts of the country. Some concentrating collectors are designed to be mounted on simple tracking devices, but most require sophisticated tracking devices, which further limit their use to electric utilities, industries, and large buildings.
Typically the solar cells are manufactured by fully automated screen printing processes onto the silicon wafers. Short cycle times and high productivity are of the highest importance.