4J36, also known as Invar 36 alloy, is a special, low-expansion iron-nickel alloy with an ultra-low coefficient of expansion (CTE); it has a low linear coefficient of thermal expansion in the range of 20-100°C. 4J42 alloy has a constant coefficient of thermal expansion (CTE) that matches that of hard glass, soft glass, and ceramics.

Alloy 4J42 is an iron-nickel alloy with a constant coefficient of expansion, its coefficient of thermal expansion (CTE) matches that of hard glass, soft glass, ceramics, and can be hermetically sealed through the glass-to-metal sealing process to achieve hermetically sealed packaging housings; CTE closure of commonly used alumina, oxidative plated LTCC, and AlN circuit board substrates; total magnetic energy and excellent electrical properties; and good machining, plating, and soldering properties.