8.2.4.4 Measures
to be Taken
Soldering joins different materials together
through a material bond. The coefficients of thermal expansion,
which depend on the materials, can sometimes be very different.
Unrestrained materials shrink differently as they cool, so
that stresses still develop in the joint after different materials
have been soldered.
There are a number of ways of keeping such thermally induced
stresses under control:
- The design of the construction is such that the ceramic
is subject to acceptable compressive stress.
- The two materials being combined only have small differences
in their thermal expansion coefficients.
- An additional buffer material can be used that compensates
through elastic or plastic deformation. The solder itself
can represent such a buffer material. The physical properties
of soft solders, and the thicknesses used in that process,
are particularly suitable for this purpose.
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