Kovar,Nilo-K,UNS K94610,E FORU

### **Kovar® / Nilo-K® / UNS K94610** **Iron-Nickel-Cobalt Alloy with Controlled Thermal Expansion for Glass and Ceramic Sealing

** --- #### **1. Overview

** **Nilo-K**, commonly known by the generic name **Kovar**, is an iron-nickel-cobalt alloy specifically engineered to possess a thermal expansion coefficient that closely matches those of borosilicate hard glass and certain ceramics over a wide temperature range. This unique characteristic makes it indispensable for creating reliable, hermetic glass-to-metal and ceramic-to-metal seals in electronic components. The alloy is designed to minimize thermal stress at the seal interface during temperature cycling, ensuring the long-term integrity and reliability of encapsulated electronic devices.

 --- #### **2. Chemical Composition (Weight %)

** The typical chemical composition of Nilo-K is outlined below. The balance is Iron (Fe). 

 | Element | Content (%) | Key Function | 

| :--- | :--- | :--- | | **Iron (Fe)** | Balance | Forms the primary matrix of the alloy. | 

| **Nickel (Ni)** | 28.5 - 29.5 | Primary element controlling the thermal expansion coefficient to match sealing glasses. | 

| **Cobalt (Co)** | 16.8 - 17.8 | Fine-tunes the thermal expansion characteristics and improves high-temperature stability. | 

| **Manganese (Mn)** | 0.20 - 0.50 | Aids in deoxidation during melting and improves hot workability. | 

| **Silicon (Si)** | 0.20 max | Controlled to ensure optimal oxide formation for glass wetting and adhesion. | 

| **Carbon (C)** | 0.02 max | Kept very low to prevent the formation of CO/CO₂ gases during the high-temperature sealing process. | 

| **Aluminum (Al)** | 0.10 max | Controlled to maintain surface quality necessary for effective sealing. | 

| **Magnesium (Mg)** | 0.10 max | Improves the characteristics of the surface oxide for bonding. | 

| **Zirconium (Zr)** | 0.10 max | Enhances grain boundary stability at high temperatures. | 

| **Sulfur (S)** | 0.015 max | Impurity, kept low to prevent hot shortness and embrittlement. | 

| **Phosphorus (P)** | 0.015 max | Impurity, controlled to maintain ductility. | 

 --- #### **3. Physical Properties** 

 | Property | Value / Condition | 

| :--- | :--- | 

| **Density** | 8.36 g/cm³ (0.302 lb/in³) | 

| **Melting Point** | ~ 1450 °C (2640 °F) | 

| **Mean Coefficient of Thermal Expansion (CTE)** | 20 - 400°C (68 - 752°F): **5.1 x 10⁻⁶/°C** (2.8 x 10⁻⁶/°F)
20 - 450°C (68 - 842°F): **5.3 x 10⁻⁶/°C** (2.9 x 10⁻⁶/°F) | 

| **Thermal Conductivity** | 17.0 W/m·K (118 Btu·in/hr·ft²·°F) at 20°C (68°F) | 

| **Specific Heat Capacity** | 439 J/kg·K (0.105 Btu/lb·°F) at 20°C (68°F) | 

| **Electrical Resistivity** | 0.49 μΩ·m at 20°C (68°F) | 

| **Modulus of Elasticity (Young's Modulus)** | 138 GPa (20.0 x 10⁶ psi) at 20°C (68°F) | 

| **Curie Temperature** | ~ 435 °C (815 °F) | | **Magnetic Permeability** | Ferromagnetic below the Curie temperature. | 

 --- #### **4. Mechanical Properties

 (Typical for Annealed Condition)** 

| Property | Value at Room Temperature | 

| :--- | :--- | |

 **Tensile Strength** | 517 MPa (75 ksi) | 

| **Yield Strength (0.2% Offset)** | 345 MPa (50 ksi) | 

| **Elongation (in 50 mm / 2 in)** | 30% | | **Hardness** | 65 - 80 HRB |

 --- #### **5. International Standards

** Nilo-K (Kovar) conforms to the following international specifications: 

 *   **ASTM:**    

*   **F15:** Standard Specification for Iron-Nickel-Cobalt Sealing Alloy 

*   **AMS:**    

*   **AMS 7724:** Sheet, Strip, and Plate    

*   **AMS 7725:** Bar and Wire 

*   **UNS:** K94610 

*   **ISO:**    

*   **ISO 17672:** Brazing — Filler metals (relevant for assembly processes) 

*   **MIL:**    

*   **MIL-I-23011:** Insulating Compound, Electrical (for Sealing) 

*   **JIS:**    

*   **JIS C 2531:** Iron-nickel alloy for sealing use 

 --- #### **6. Product Applications

** Nilo-K is critical in applications requiring precise thermal expansion matching for hermetic sealing: 

 *   **Microelectronics & Semiconductor Packaging:

**    *   Integrated Circuit (IC) packages (DIP, CerDIP)    

*   Transistor and diode headers/caps    

*   Microwave and RF power device packages 

*   **Aerospace & Defense Electronics:

**    *   Hermetic connectors and feedthroughs    

*   Sensor housings    

*   Flight-critical electronic enclosures 

*   **Telecommunications & Optoelectronics:

**    *   Fiber optic component housings    

*   Laser diode packages    

*   Photonic integrated circuit (PIC) enclosures 

*   **Medical Electronics:

**    *   Implantable medical device housings (e.g., pacemakers, neurostimulators)    

*   Hermetic sensor packages for in-vivo monitoring 

*   **Power Electronics:

**    *   High-power semiconductor packages (IGBTs, Thyristors)    

*   Power module bases and lids 

 --- #### **7. Key Characteristics & Advantages

** *   **Precision Matched CTE:** Coefficient of Thermal Expansion (∼5.1-5.3 x 10⁻⁶/°C) is tailored to match borosilicate glass (e.g., Pyrex) and alumina ceramics. 

*   **Superior Seal Reliability:** Minimizes thermal stress at the seal interface, preventing cracking and leakage over countless thermal cycles. 

*   **Excellent Hermeticity:** Capable of achieving and maintaining high vacuum or pressure seals. 

*   **Good Mechanical Strength:** Provides robust structural support for delicate internal components. 

*   **Good Electrical and Thermal Conductivity:** Suitable for applications requiring electrical feedthroughs and heat dissipation. 

*   **Excellent Fabricability:** Can be readily deep-drawn, stamped, machined, and polished into complex shapes. 

*   **Proven Long-Term Stability:** Offers consistent performance and reliability over decades of service. 

 --- **Disclaimer:

** *Kovar® and Nilo-K® are registered trademarks. The values provided are typical and for informational purposes only. For critical applications, always consult the official material data sheets from the supplier and relevant design codes. Successful glass-to-metal sealing requires strict control of the alloy's surface finish, pre-oxidation treatment, and the sealing atmosphere.*

Packing of Kovar,Nilo-K,UNS K94610

Standard Packing: 

Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 1679 gallon liquid totes Special package is available on request.