Co-fired ceramics are hard substrate materials in which metalization and ceramic are fired together (co-fired, ya dig?) to form signal interconnects such as buried feedthroughs, microstrip, and stripline. There are two broad categories of co-fired ceramics, low-temperature co-fired ceramics (LTCC) and high-temperature co-fired ceramics (HTCC).
While the attractions are many (3D-structures are possible), the drawbacks must be understood. The dielectric properties of co-fired ceramics are not nearly as good as pure alumina, and the metalizations are not as good as pure metals. Thus you can expect more transmission line losses when you use co-fired ceramics.
Low-temperature co-fired ceramics
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High-temperature co-fired ceramics
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