KOVAR, also known as ASTM F 15 alloy, is a controlled expansion alloy commonly used in metal seals, LIDS, lead frames, and electronic package bases for high integrity glass and ceramics. Kovar is made of nickel, cobalt and iron. This alloy is designed to accommodate the technological needs of computers, microwaves, hydrides, semiconductors and the space age, and as such, it is an important resource for the defense, aerospace and telecommunications industries.
The F15 undergoes a rigorous vacuum melting process to produce the highest level of cleanliness and a more uniform alloy. The ASTM F15 alloy (Kovar) is very stable, passing the standard phase transition test at -80℃ and remaining stable at -196℃.
kovar is a nickel-cobalt-ferro alloy designed to be compatible with the thermal expansion characteristics of borosilicate glass (~5×10-6 /K between 30 and 200°C and ~10×10-6 /K up to 800°C) in order to achieve direct mechanical connection over a range of temperatures. It is used in electroplating conductors, into glass jackets of electronic components such as vacuum tubes (valves), X-ray and microwave tubes, and some light bulbs
The name Kovar is often used as a general term for FeNi alloys with these particular thermal expansion properties. Note the related special Fe-Ni alloy Invar, which exhibits minimal thermal expansion.
F15 nickel alloys usually harden fairly quickly, and the high pressures created by processing can cause hardening and slow progress, as well as cause warping in some materials. Make sure you have a rigid setting to work at a low speed, and try using sulphide mineral oil. When working Kovar (ASTM F15 alloy), it tends to be quite colloidal. The knife tends to go straight through the metal rather than cutting it.
Complete control of heating is important when working F15, as excessive heat build-up can cause the alloy to deform. When working on metal, you must make sure to remove the feathery or wire edges from the tool. As you have always done, make sure that every tool is under constant review. Carbide tools will provide you with the highest cutting rate without breakage and should be used for turning operations without interrupting cuts. If you have interrupted cutting, use a high speed steel tool. Your drill should be as short as possible. When reaming, you should only drill at half speed and your feed should be about 3 times the speed of your bit for safe reaming. Whether you are processing rolls or sheets of this controlled expansion alloy, or making glass to metal or ceramic to metal seals, we hope that some of the above Cova processing techniques will be helpful in your next application.
Application of KOVAR:
- Electronic packaging bases, covers, lead frames and glass to metal seals.
- Communications, aircraft and aviation industries, military and defense.
- Semiconductors and microwaves.
