KOVAR parts seal preparation and physical properties

Kovar® is a vacuum-melted iron-nickel-cobalt low-expansion alloy. The chemical composition content is controlled in a very narrow range to ensure accurate and balanced thermal expansion performance. At the same time, strict quality control during the manufacturing process of KOVAR machining parts also ensures balance Its physical and mechanical properties are more suitable for deep drawing, stamping and various cutting processes.

Material use

Kovar® is used for vacuum sealing of hard glass and ceramics, and is widely used in electron tubes, microwave tubes, transistors and diodes. On integrated circuits, it is used for flat integrated circuits and dual in-line packages.

Seal preparation

All parts made by Kovar® should be degassed and annealed in a wet hydrogen atmosphere. Hydrogen is injected into water at room temperature and gets wet through blisters. Care must be taken to prevent surface carbonization. The heat treatment furnace must have a cooling chamber that provides the same atmosphere. The heat treatment is carried out in the temperature range of 1540/2010°F (838/1099°C). The heat treatment time starts from a low temperature and rises to a high temperature in 20 minutes. Then the parts are moved to the cooling zone and cooled to 570°F (299° C) Then take it out.

When sealing between metal and hard glass, it is recommended that the metal has an oxide film. The preferred oxide film is thin and tightly adsorbed on the metal surface treatment. Such an oxide film can be heated to 1200/1290°F (650/700°C) in an atmospheric environment and continue for a period of time until the dark gray surface layer turns into a light brown oxide film.

Physical properties
The proportion is 8.36;
Density 0.3020lb/in3;
Thermal conductivity 120.0 BTU-in/hr/ft²/°F;
Elasticity coefficient (E) 20.0 x 103 ksi;
Resistance (70.0°F) 294.0 ohm-cir-mil/ft;
Curie temperature 815°F;
The melting point is 2640°F.
magnetic

Kovar alloy machining are magnetic below the Curie temperature, and the magnetic properties depend on heat treatment. The smaller the hardness, the higher the permeability and the smaller the hysteresis loss.