Low temperature cofired ceramics are multilayer circuits made of individual ceramic layers. By printing the individual ceramic layers, conductor tracks, resistors as well as capacitive and inductive functionalities can be generated. To produce multilayer circuits, the ceramic carriers must be pressed and finally sintered at 850 to 900° C.
Is LTCC always the optimal substrate technology?
There are special requirements for electronic circuits and components for numerous applications. Conventional board technologies often do not provide the desired performance. This is the case at:
- ideal heat conduction in a wide temperature range (-100 ° C ... + 200 ° C)
- high frequency stability
- permanent hermeticity
- long-term stability (> 20 years)
- high dielectric strength &mechanic solidity
- resistance to plasma or ion bombardment
- high degree of miniaturization - 3-D functions such as cavities, stepped bonding planes, channels and membranes
Compared to conventional circuit carriers, e.g. FR4, LTCC technology can meet precisely these requirements. Typical fields of application are, for example, in the medical technology, automotive and HF industries.
facts and figures of Multilayer ceramic circuits by Micro-Hybrid
- Materialsystems DuPont 951 + 9K7: Low thermal expansion coefficient, 5.8 ppm / K (DuPont 951), 4.4 ppm / K (DuPont 9K7)
- Compatibility with various precious metal pastes (for very reliable conductors)
- Thickness of a single layer: 40 μm -200 μm
- Number of layers 3 ... .40
- Benefit size: 6 "x 6" (unsintered state)
Typical setup of a LTCC assembly
Prefabricated green sheets are used for the production of LTCC. Depending on the given design, holes are punched at predetermined positions and filled with a metal paste. These so-called vias form the vertical contact in the multilayer structure. Subsequently, the metal pastes are applied by means of screen printing to the green film, which form the planar electrical conductor tracks. After the metal structures are applied, the green sheets are pressed together in a predetermined order and sintered between 850-900 ° C. Sensitive structures or surface elements can additionally be applied or fitted. Subsequently, the LTCC substrates are singled out and tested for their functionality.