8.2.4.3 Active
Soldering
Active soldiers typically melt at between
600 and 1,000°C, and are processed at between 800 and
1,050 °C.
Active soldering makes it possible to solder directly to ceramic
without an additional metallisation process. These solders
are metallic, the compositions of which alloys permit them
to wet non-metallic inorganic materials. They contain components
such as titanium, zirconium or hafnium that react with ceramics.
Special attention is called for by the active soldering process,
since the solders do not flow like conventional solders, and
the capillary effect cannot be used. Active soldering in a
furnace must, however, be carried out in a carefully monitored
furnace atmosphere.
The process of active soldering is achieved through the high
reactivity of titanium. During the soldering process, a thin
yet continuous reaction layer forms on the surface of the
ceramic, providing the necessary adhesion.
Active soldering systems typically consist of silver/titanium,
silver/copper/titanium, or silver/copper/indium/titanium.
The soldering is usually carried out under argon or in a vacuum.
In addition to aluminium oxide and aluminium nitride, almost
any other ceramic and metals that are not easily wetted may
be soldered. Actively soldered joints are therefore appropriate
in the machine construction sector.
Solders for various ceramics are available on the market.
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