Schott® borosilicate glass 7056 was widely used as a Kovar Sealing glass. This glass has been discontinued and is out of melt. This borosilicate glass was replaced with Corning® 7720 Nonex Tungsten Sealing glass which also has been discontinued and has now been replaced by Schott® 8250 Kovar Sealing glass. You can also view Corning® 7052 Kovar Sealing glass datasheet.
| Kovar Sealing Glass: Corning® 7056 | ||
|---|---|---|
| Glass Code: Corning® | 7056 |
|
| Type | Alkali Borosilicate |
|
| Color | Clear |
|
| Principal Use | Electronic |
|
Mechanical |
Metric | English |
| Density | 2.29g/cm3 |
143 lb/ft3 |
| Young's Modulus | 6.4 x 103 kg/mm2 |
9.2 x 106 psi |
| Poisson's Ratio | 0.21 |
|
| Shear Modulus | 2.7 x 103 kg/mm2 |
3.8 x 106 psi |
Viscosity |
Metric | English |
| Working Point (104Poise) | 1058°C |
1936°F |
| Softening Point (107.6 Poise) | 718°C |
1324°F |
| Annealing Point (1013 Poise) | 512°C |
954°F |
| Strain Point (1014 Poise) | 472°C |
882°F |
Thermal |
Metric | English |
Coefficient of Expansion (0 - 300°C) (25°C to set point 679°C) |
51.5 x 10-7/°C |
28.5 x 10-7/°F |
54.5 x 10-7/°C |
30.0 x 10-7/°F |
|
Optical |
Metric | English |
| Refractive Index (589.3nm) | 1.487 |
|
| Birefringence Constant | 300nm/cm/kg/mm2 |
|
Electrical |
Metric | English |
| Log10 Volume Resistivity @ 250°C | 10.3 ohm-cm |
|
| Log10 Volume Resistivity @ 350°C | 8.4 ohm-cm |
|
| Dielectric Constant @ 20°C, 1MHz | 5.7 |
|
| Loss Tangent @ 20°C, 1MHz | 0.27% |
|