4.2.3 Metallisation
Some manufacturers of technical ceramics
offer metallised ceramics. Aluminium oxide and aluminium nitride
are available as substrate materials. The metallisation offered
is suitable for brazing, and, of course, also for soft soldering,
and consists of a base metallisation of tungsten having a
layer thickness of at least 6 ?m, applied by a screen printing
process and fired on. A layer of nickel, applied non-electrolytically,
with a minimum thickness of 2 µm, is applied on top
to assist the flow of solder. Other layer thicknesses are
possible.
A gold layer with a thickness of approx. 1 ?m can be deposited
to protect against corrosion. Alternatively, the electroless
applied nickel layer can be reinforced with a bondable gold
layer. An additional layer of tin can also be applied if soft
soldering is planned.
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