Alloy 36, commonly known as Invar, is a low thermal expansion alloy with a main composition of 36Ni-Fe. It has a very low coefficient of thermal expansion, which suppresses dimensional changes due to temperature changes, so it is used in applications that require high-precision dimensions or where stress due to dimensional changes is not desired.
Alloy 42 is a low thermal expansion alloy with a main composition of 42Ni-Fe.
Although its coefficient of thermal expansion is greater than that of Alloy 36, it is close to the glass, ceramics, and silicon, and is threfore used as a glass sealing material for IC lead frames and other applications.
KOV is a low thermal expansion alloy with a main composition of 29Ni-17Co-Fe. Although the coefficient of thermal expansion is higher than that of Alloy 36 or Alloy 42, it is close tohard glass, and is therefore used for IC leadframes and other applications for sealing hard glass.