Kovar Alloy  – ASTM F15

Pernifer® 2918, Dilver® P1, Nilo® K

EFINEA is a leading global supplier of the nickel-iron-cobalt alloy, Kovar® Alloy (ASTM F15).  This unique controlled expansion alloy with a combination of  29% nickel, 17% cobalt, and the balance iron was developed in the 1930s, under the guidance of Westinghouse. It was the first stress-free, glass-to-metal seal capable of maintaining its integrity in a range of environments and is still the preferred alloy for hermetic sealing today.

For over 50 years, EFINEA has been a leading supplier of Kovar® and controlled expansion alloys.  With warehouses in NJ and CA, our stock of coil, strip, plate, round bar/rod, and sheet is available in numerous sizes, tempers, and conditions to meet the global demands of customers.  All standard stock items are ready-to-ship for those in immediate need of materials. Request a quote today!

Kovar® Properties & Characteristics

ASTM F15 Alloy (UNS K94610)

Various manufacturers have produced ASTM F15 under their own brand names such as Kovar®, Pernifer® 2918, Dilver® P1, and NILO® K. Kovar’s product expansion characteristics match both borosilicate (Pyrex®) glasses and alumina ceramics making it one of the most popular of the controlled expansion alloys for hermetic sealing applications.  A porosity-free product, it is produced to ensure good properties for machining and deep drawing.

In manufacturing ASTM F15 Alloy, controls are exercised at various stages to assure close limits of thermal expansion and other desired properties are met.  Procedural tests are conducted to measure the uniformity and high-quality thermal expansion, transformation, cupping for “drawability”, Rockwell hardness, and grain size, free from gas, and glass sealing.  Rod and wire soundness are assured by subjecting the primary bar stock to ultrasonic testing and microscopic examination of the ends. A thorough inspection of sheets guards against surface defects.

Kovar Melting Temperatures

Kovar® or ASTM F15 Alloy is made not to undergo a phase transformation from gamma to alpha at temperatures above minus 80 °C (minus 176 °F).  The actual transformation is considerably lower. Where extremely low temperatures are service requirements, specially selected alloy melts with specific transformation points can be supplied.  Kovar® ( ASTM F15) is a stock material from EFINEA and has been tested by our mills to not transform to -196°C.

Frequently Asked Questions About Kovar

What is Kovar® material?

Kovar® is an iron-nickel-cobalt, controlled expansion alloy with 29% Nickel, 17% Cobalt, and the remaining balance Iron. Kovar® expansion characteristics match both borosilicate (Pyrex) glasses and alumina ceramics making it one of the most popular of the controlled expansion alloys for hermetic sealing applications allowing direct mechanical connections over a range of temperatures in conductors entering glass envelopes of electronic parts. It is also known as ASTM F-15, NILO K, Pernifer 2918, and Dilver P1.

What is Kovar® used for?

Kovar® is used for hermetic sealing applications. In power tubes it is used for glass or ceramic-to-metal construction in radio and television transmitters, induction heating equipment and navigational aids. It is used in oscillators, amplifiers, and converters in microwave tubes for radar, scatter propagation systems, electronic countermeasure equipment, navigational systems and communication links. Kovar® is used in integrated circuits in flatpack and dual-in-line packages for access to and isolation for the semiconducting chip.

Is Kovar® Steel?

No, Kovar® is an iron-nickel-cobalt alloy used in the electronics industry due to its unique properties of thermal expansion, and its machining and deep drawing characteristics. Kovar® is used for applications such as vacuum tubes (valves), X-ray tubes, microwave tubes, power tubes, transistors, diodes, and hybrid packages.

What materials are Kovar® similar to?

Kovar® is similar to other controlled expansion alloys that are used in applications where the thermal changes of a metal must be factored into the design of a component such as when forming a hermetic seal with glass or ceramic or when a specific expansion must be met over a certain temperature range. Other controlled expansion alloys are Alloy 42, Alloy 46, Alloy 48, Alloy 52, Invar® and Super Invar® 32-5.

EFINEA is a leading supplier of Kovar® – ASTM F15 Alloy. A controlled expansion, glass-to-metal sealing alloy that is also known as Pernifer® 2918, Dilver® P1, Nilo® K.

Dilver is a registered trademark of Aperam Alloys Imphy, France

Kovar is a registered trademark of CRS Holdings LTD., Delaware, USA

NILO is a registered trademark of Huntington Alloys Corp., West Virginia, USA.

Pernifer is a registered trademark of VDM Metals GmbH, Germany