SCHOTT Technical Glasses

38
The material properties – especially the gas barrier properties
– are by far superior to polymer films:
Oxygen transmittance rate (cc/[m 2 · 24 hr]) ––>
100
10
1
0.1
0.01
30 µm ultra-thin glass (AF 32 ® eco)
100 µm PET
100 µm PEN
20 µm PVA
20 µm PVDC coated PET
0.001
10 –6 10 –5 10 –4 10 –3 10 –2 10 –1 1 10 100 1000
Water vapor transmittance rate (g/[m 2 · 24 hr]) ––>
Sample inspection of a thin glass wafer after processing
Fig. 31. Gas barrier properties of ultra-thin glass
8.4 Thin glass processing
Further material properties of the ultra-thin glass types
which are available either on roll or as cut-to-size sheets
property D 263 T eco AF 32 ® eco
CTE 7.2 ppm/K 3.2 ppm/K
alkaline content low no
transformation point 557 °C 715 °C
refractive index 1.5231 1.5255
transmission
λ = 550 nm,
d = 1 MHz
dielectric constant
(at 1 MHz and 20 °C)
loss tangent (tan δ)
(at 1 MHz and 20 °C)
thermal conductivity
(90 °C)
91.7 % 91.9 %
6.7 5.1
0.0061 0.0009
1.06 W/(m · K) 1.06 W/(m · K)
glass type borosilicate alumin-borosilicate
Table 7. Technical data of relevant materials
SCHOTT offers an entire portfolio of technologies for processing
of thin glass, e.g.
• Cut-to-size for a wide range of wafer and substrate sizes
• Surface refinement by polishing and/or coating
• Structuring of holes or cavities
• Edge treatment options
• Ultrasonic washing
• Clean room packaging
SCHOTT thin glass from a down-draw process does not require
any polishing for typical wafer applications due to its
inherently pristine surface quality, low roughness and excellent
geometry like low total thickness variation. Wafers are
directly CNC cut from the mothersheet. Depending on
customer requirements, only edge grinding and ultrasonic
washing are subsequent processing steps. These wafers are
used in high volumes as semiconductor cover glass in wafer
level packaging processes of CMOS image sensors for camera
modules.