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LTCC |
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The LTCC (Low Temperature
Co-Fired Ceramic) is a ceramic wiring carrier with a multi-layer
structure. A flexible raw material (Green Tape) is used as a
base. This unsintered film consists of a mixture of glass, ceramic
and organic solvents. The firms Heraeus, DuPont and Ferro for
example supply this raw material.
In the manufacturing of a LTCC Ceramic, a corresponding number
of layers is started through the cutting of the Green Tapes.
Prior to their further processing some materials require an
additional Temper-Process at about 120 °C. As a second step
the different layers are mechanically processed. This means
that the adjustment and plated-through holes (Vias) are punched
in the tapes. This is followed by a via-filling pressure and
the application of the metallisations, resistors and the other
films using a thick film-silk screen process. The usual conductive
materials are gold, silver, platinum and palladium alloys. The
injecting of the layers and the subsequent sintering at about
850 °C - 900 °C produce the finished multilayers. The
sintering causes the LTCC material to shrink by about 12% in
the x/y direction and 17% in the z-direction. It is particularly
the shrinkage on the x/y-level that adversely affects any adherence
to the structural precision. In order to prevent this, non-shrinkage
material for the x/y-direction (0.1%) has been developed. This
positive effect is achieved through a combination of specially
developed tape materials. When deploying this material the increase
of the shrinkage in the z-direction (about 45%), especially
in the utilisation of holes and cut-out sections, must not be
ignored. If this is observed in the construction and processing
phases then the 0-shrinkage tape is a step forward in comparison
to the traditional LTCC tape material.
Benefits
The possibility of processing the layers individually and in
different ways prior to the sintering enables the LTCC to also
be used as a packaging construction element. In this way cavities,
ducts and other forms can be achieved. This technology enables
multilayer structures to be achieved in a simple way with integrated,
passive components. LTCC also possesses, apart from the thermal
conductivity, the same positive features as thick film circuitry.
The leakage of waste heat must be carried out via thermal vias
if necessary.
Applications
LTCC solutions are used for circuit boards with high or low
ambient temperatures and a strong thermal cycling with the simultaneous
implementation of packaging tasks. The LTCC solution presents
a cost-effective solution for larger numbers of pieces such
as those which are customary in the automobile sector.
The etching of the thick film on the top side or the metallization
on the thin film means that the implementation for high-frequency
applications can also be considered.
details
on this technology |
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