Low temperature co-fired ceramic
Encyclopedia
Low temperature co-fired ceramic (LTCC) devices are monolithic, ceramic microelectronic devices. In this context ‘co-fired ceramic’ means that the ceramic support structure and any conductive, resistive, and dielectric materials are fired in a kiln at the same time, and ‘Low temperature’ means that the sintering, temperature is less than 1000 °C. LTCC devices include capacitors, inductors, resistors, transformers
, and hybrid circuits. LTCC processes can also be used to make packages for ICs
. LTCC devices are made by processing a number of layers independently and assembling them into a device as a final step. This differs from semiconductor device fabrication where layers are processed serially; each new layer being fabricated on top of previous layers.
and wireless
applications, LTCC technology is also used to produce multilayer hybrid integrated circuits
, which can include resistors, inductors, capacitors, and active components in the same package. LTCC hybrids have a smaller initial ("non recurring") cost as compared with ICs
, making them an attractive alternative to ASIC
s for small scale integration devices.
ceramic tape. Depending on the desired inductance and current carrying capabilities a partial winding to several windings may be printed on each layer. Under certain circumstances a non ferrite ceramic may be used. This is most common for hybrid circuits where capacitors, inductors, and resistors will all be present and for high operating frequency applications where the Hysteresis
loop of the ferrite becomes an issue.
one can achieve these resistances with different cut forms to the exact resistance value (±1%) desired. With this procedure, the need for additional discrete resistors can be reduced, thereby allowing a further miniaturization of the printed circuit boards.
: the ceramic is generally fired below 1000°C due to a special composition of the material. This permits the co-firing with highly conductive materials (silver, copper and gold). LTCC also features the ability to embed passive elements, such as resistors, capacitors and inductors into the ceramic package minimising the size of the completed module.
Transformers
A transformer is a device that transfers electrical energy from one circuit to another by magnetic coupling.Transformer may also refer to:* ASUS Eee Pad Transformer, an Android 3.2 Honeycomb tablet computer manufacturer by Asus...
, and hybrid circuits. LTCC processes can also be used to make packages for ICs
Electronic packaging
Electronic packaging is a major discipline within the field of electronic engineering, and includes a wide variety of technologies. It refers to enclosures and protective features built into the product itself, and not to shipping containers...
. LTCC devices are made by processing a number of layers independently and assembling them into a device as a final step. This differs from semiconductor device fabrication where layers are processed serially; each new layer being fabricated on top of previous layers.
History
Co-fired ceramics were first developed in the late 50’s and early 60's to make more robust capacitors. The technology was later expanded in the 60’s to include multilayer printed circuit board like structures.Hybrid Circuits
LTCC technology is especially beneficial for RF and high-frequency applications. In RFRadio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
and wireless
Wireless
Wireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few meters for television remote control, or as far as thousands or even millions of kilometers for deep-space radio communications...
applications, LTCC technology is also used to produce multilayer hybrid integrated circuits
Hybrid circuit
A hybrid integrated circuit, HIC, hybrid microcircuit, or simply hybrid is a miniaturized electronic circuit constructed of individual devices, such as semiconductor devices and passive components , bonded to a substrate or printed circuit board...
, which can include resistors, inductors, capacitors, and active components in the same package. LTCC hybrids have a smaller initial ("non recurring") cost as compared with ICs
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
, making them an attractive alternative to ASIC
ASIC
ASIC may refer to:* Application-specific integrated circuit, an integrated circuit developed for a particular use, as opposed to a customised general-purpose device.* ASIC programming language, a dialect of BASIC...
s for small scale integration devices.
Inductors
Inductors are formed by printing conductor windings on ferriteFerrite (magnet)
Ferrites are chemical compounds consisting of ceramic materials with iron oxide as their principal component. Many of them are magnetic materials and they are used to make permanent magnets, ferrite cores for transformers, and in various other applications.Many ferrites are spinels with the...
ceramic tape. Depending on the desired inductance and current carrying capabilities a partial winding to several windings may be printed on each layer. Under certain circumstances a non ferrite ceramic may be used. This is most common for hybrid circuits where capacitors, inductors, and resistors will all be present and for high operating frequency applications where the Hysteresis
Hysteresis
Hysteresis is the dependence of a system not just on its current environment but also on its past. This dependence arises because the system can be in more than one internal state. To predict its future evolution, either its internal state or its history must be known. If a given input alternately...
loop of the ferrite becomes an issue.
Resistors
Resistors may be embedded components or added to the top layer post firing. Using screen printing, a resistor paste is printed onto the LTCC surface, from which resistances needed in the circuit are generated. When fired, these resistors deviate from their design value (±25%) and therefore require adjustment to meet the final tolerance. With Laser trimmingLaser trimming
Laser trimming is the manufacturing process of using a laser to adjust the operating parameters of an electronic circuit.One of the most common applications uses a laser to burn away small portions of resistors, raising their resistance value...
one can achieve these resistances with different cut forms to the exact resistance value (±1%) desired. With this procedure, the need for additional discrete resistors can be reduced, thereby allowing a further miniaturization of the printed circuit boards.
Transformers
LTCC transformers are similar to LTCC inductors except transformers contain two or more windings. To improve coupling between windings transformers include a low-permeability dielectric material printed over the windings on each layer. The monolithic nature of LTCC transformers leads to a lower height than traditional wire wound transformers. Also, the integrated core and windings means these transformers are not prone to wire break failures in high mechanical stress environments.Advantages
This technology presents advantages compared to other packaging technologies such as HTCCHigh temperature co-fired ceramic
High temperature co-fired ceramic is a multi-layer packaging technology for the electronics industry, used in military electronics, MEMS, microprocessor and RF applications....
: the ceramic is generally fired below 1000°C due to a special composition of the material. This permits the co-firing with highly conductive materials (silver, copper and gold). LTCC also features the ability to embed passive elements, such as resistors, capacitors and inductors into the ceramic package minimising the size of the completed module.
See also
- High temperature co-fired ceramicHigh temperature co-fired ceramicHigh temperature co-fired ceramic is a multi-layer packaging technology for the electronics industry, used in military electronics, MEMS, microprocessor and RF applications....
(HTCC) - Tape castingTape castingTape casting is a casting process used in the manufacture of thin ceramic tapes from ceramic slurry.The tapes thus produced can be used for a variety of purposes, including the manufacture of electronic components such as ceramic capacitors....
- Laser trimmingLaser trimmingLaser trimming is the manufacturing process of using a laser to adjust the operating parameters of an electronic circuit.One of the most common applications uses a laser to burn away small portions of resistors, raising their resistance value...
- Hybrid integrated circuit
External links
- LTCC Technology description of LTCC and related drawings
- Kyocera LTCC drawings showing an LTCC hybrid circuit stack up