Multilayer Ceramics manufacture
Multilayer ceramics are manufactured using high and low-temperature, co-fired alumina ceramics. The ceramics are produced by mixing ceramic and glass powders of specific composition, and small quantities of binding agent and solvent to create a homogeneous slurry. This slurry is then cast to form sheets of uniform thickness (about 100 μm - 500 μm). Once dried, these so-called Green Sheets can be easily cut, rolled up for transport, and processed further.
The next step in the production involves the definition of the electrical conducting lines. Depending on the design, the sheets are punched to form cavities and vias, which can be filled with a metal paste. These vias create vertical connections for the electrical feedthroughs. The planar electrical lines are defined on the ceramic sheets by screen-printing, again using refractory metal pastes.
Once the various metal structures are defined, the ceramic sheets are stacked in a specific order and laminated. This process connects the individual, basically two dimensional sheets and ends up in a three dimensional structure with hermetic electrical feedthroughs. In data communication, the cross section of this three dimensional structure often is similar to a "T", which is why the finished ceramic product is also called a T-bar.
The multilayer ceramic is co-fired at high temperatures to form a solid and hermetic ceramic. For HTCC a final metal coating (e.g. a plated Ni or Ni/Au coating) on the accessible metal structures offers the possibility for high temperature brazing (using e.g. AgCu eutectic) or low temperature soldering (e.g. AuSn eutectic) process steps. By this the ceramic feedthrough component can be combined with an even more complex metal housing, providing an extremely reliable hermetic package with various customized mechanical, electrical, optical and thermal functionalities.
Characteristics of HTCC:
Characteristics of LTCC:
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