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Home  > Products and Service  > Electronics Products  > Glass Disk For Magnetic Head Flying Height Tester (GD-FHT)
 
Glass Disk For Magnetic Head Flying Height Tester (GD-FHT)
 
|  GD-FHT  |
 
OHARA's GD-FHT is a glass disk for use in flying height testers. It contributes to the decrease of static breaking in the magnetic head, both in manufacturing and R&D. This obvious advantage is due to the superior electrical properties of GD-FHT compared to conventional products, such as S-BSL7 and Synthetic Fused Silica. As the glide height of the magnetic head is lowered, we offer our "smooth type" GD-FHT which is an extremely precise, super smooth and ultra-clean disk. OHARA's GD-FHT is transparent with the same mechanical strength as conventional products.   GD-FHT
 

Please inquire about other specifications.

 

GD-FHT

Properties GD-FHT Conventional Materials
S-BSL7 (BK7) Synthetic
Fused Silica
Electrical
Properties
Volume Resistivity* (Ω·cm) 1.1×1011 1.0×1015 1.0×1019
Surface Resistivity*** (Ω·□) 4.4×1012 1.0×1015 8.6×1014
Charging Voltage*** kV 0.05 2.6 3.1
Half Decay Period*** (s) 8.9 >30min >30min
Mechanical
Properties
Knoop Hardness** Hk 590 (6) 570 (6) 640 (6)
Abrasion** 53 94 59
Young's Modulus (GPa) 82 80 71
Rigidity Modulus (GPa) 33 33 31
Bending Strength (MPa) 107 64 69
Poisson's Ratio 0.22 0.21 0.17
Thermal
Properties
CTE (10-7/K) 33 72 5.5
*Measured at 20°C and Humidity of 60% according to JIS K 6911.
**Measured according to Japanese Optical Glass Industrial Standards (JOGIS).
***Measured referring to JIS L 1094 (OHARA's original method).
·Half decay period is the time required for the charging voltage of the surface to half of its initial value.

Transmittance
(%)
Wavelength nm 400 500 600 700
2.45mmt 89.8 91.4 91.6 92.0
2.76mmt 89.8 91.3 91.6 92.0
4.35mmt 88.5 90.9 91.3 91.6
6.44mmt 87.4 90.7 91.3 91.6
Refractive Indices 436nm 1.539
486nm 1.534
546nm 1.530*
588nm 1.528
633nm 1.526*
656nm 1.525
*Calculated Value n=0.00482/λ2+1.51362                n: Refractive Index λ: Wavelength μm)

Specifications Outer Diameter mm 48-133
Inner Diameter mm 5-10
Thickness mm 2-8
Concentricity μm 5-10
Roundness of Inner
Diameter μm
≤5-10
Parallelism μm ≤5-10
Flatness μm ≤0.5
Roughness Rmax nm ≤2.5-4.0
Properties subject to change along development.
 
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