SCHOTT Borofloat® 33 /
Nexterion® Glass B
Flatness and Surface
Quality
SCHOTT Borofloat® 33 / Nexterion® Glass B
 Borofloat® 33 is a flat, borosilicate glass
 Borofloat® 33 is manufactured using the “microfloat” method
 The production method produces virtually flawless flat glass and a
mirror-like surface quality
Many Parameters Influence Glass Sheet “Flatness”
 Surface Flatness is the deviation for a plano surface
 Warp is the difference between the maximum and minimum deviations of the median
surface relative to the backside reference plane. Warp is like the wavy deformation seen
in potato chips.
 Bow is the measure of how concave or convex the deformation of the median surface of
the glass sheet at the center point, independent of any thickness variations. The easy
way to visualize Bow is if you think of a bowl turned either upside down or right side up
on a flat surface (convex or concave).
 Total Thickness Variation (TTV) represents the difference between the minimum and
maximum thickness measured on the sheet of glass.
 Thickness Tolerance (inter-slide) The production of large flat sheets of glass yields
variances in thickness. Thickness will vary depending on sheet size and where on the
sheet the measurement is made. In order to accommodate this fact SCHOTT uses a
nominal tolerance value
 Thickness deviation (intra-slide) This is the thickness differences between slides
 Surface Roughness Smoothness: RA (average roughness) or RMS (root mean
squared) is a measure of the texture of a surface.
Bow and Warp
Total Thickness Variation (TTV)
“Flatness” of Nexterion® Glass B Slides
 SCHOTT Nexterion® defines “flatness” as the accumulated
overall possible thickness deviation
 This includes warp, intra-slide thickness deviation, and interslide thickness tolerance
convex side up
Warp
Thickness deviation intra-slide
S-shape
a
Thickness tolerance inter-slide
b
concave side up
Warp
P
 Nexterion® slides have a maximum total “flatness” deviation of ≤ 25 µm for these
three factors combined
Measurement of individual Glass B Slide
Flatness using Interferrometry
ZYGO's VeriFire™ XP/D
Laser Fizeau mechanical phase-shifting interferometer
Flatness of Nexterion® Glass B Slides
The typical flatness across a single 75.6 x 25 mm slide is ≤ 5 µm
Surface MicroRoughness of Glass B Slides
Measured using Digital instrument nanoScope Atomic Force Microscope (AFM)
Surface MicroRoughness of Glass B Slides
Typical MicroRoughness Ra < 3 nm
This data represents typical average values and is for reference only.
Thank you