FOTURAN®

FOTURAN® is manufactured by Schott Glass Corporation, Technical Glass Division, and is a photosensitive glass which enables it to be structured for a variety of purposes. This material combines the unique glass properties (transparency, hardness, chemical and thermal resistance, etc.) and the opportunity to achieve very fine structures with tight tolerances and high aspect ratio (hole depth/hole width). Smallest structures of 25 µm are possible with a roughness of 1 µm.

1. UV-Exposure
In the exposure step, FOTURAN® glass is exposed to ultraviolet light at a wavelength between 290 - 330 nm. It is possible to illuminate material thicknesses of up to 2 mm. An energy density of approximately 2 Joule/cm² is sufficient to structurize a 1 mm thick FOTURAN® plate.

2. Heat treatment
With the UV exposure step silver atoms are formed in the illuminated areas. During the heat treatment between 500^o and 600^oC the glass crystallizes around these silver atoms.

3. Etching
The crystalline regions, when etched with a 10% solution of hydrofluoric acid at room temperature, have an etching rate up to 20 times higher than that of the vitreous regions. If wet chemical etching is supported by ultrasonic etching or by spray-etching, the resulting structures display a large aspect ratio. Etching

FOTURAN® Process guidance

UV-Exposure
Wavelength	290 - 330 nm
Mask	Chromium on quartz
Lamp	Hg Lamp (1000 W)
Energy density	2 Joule/cm² to structurize a 1 mm thick substrate

Heat treatment
Ramp rate	room temperature - 500^oC : 1^o - 3^oC/min
Dwell time	500^oC : 1h
Ramp rate	500^o - 600^oC : 1^oC/min
Dwell time	600^oC : 1h
Cooling rate	600^oC - room temperature : 3^oC/min

Etching
Etchant	10% hydrofluoric acid
Speed	appr. 10 µm/min.; highly dependant of process parameters
Selectivity	20:1 (exposed:unexposed)

Crystallisation
Temperature	800^o - 900^oC
Time	1h

FOTURAN® Material properties

Mechanical Properties	Glass	Glass ceramic (brown)
Young's modulus [10³ N/mm²]	78	88
Poisson's ratio	0,22	0,19
Knopp hardness [N/mm²]	4600	5200
Modulus of rapture [N/mm²]	60	150
Density [g/cm³]	2,37	2,41

Thermal properties	Glass	Glass ceramic (brown)
Thermal expansion a_20-300[10^-6/K]	8,6	10,5
Thermal conductivity 20^oC [W/mK]	1,35	2,73
Specific heat 25^oC [J/gK]	0,88	0,92
Transformation temperature [^oC]	465	-
Max. safe processing temperature [^oC]	450	750

Electrical properties	Glass	Glass ceramic (brown)
Electrical conductivity 25^oC [Ohm*cm]	8,1*10¹²	5,6*10¹⁶
Electrical conductivity 200^oC [Ohm*cm]	1,3*10⁷	4,3*10⁷
Dielectric constant 1 MHz, 20^oC	6,5	5,7
Loss factor tan d 1 MHz, 20^oC [*10^-4]	65	25

Chemical properties	Glass	Glass ceramic (brown)
Water resistance DIN/ISO 719 [(µg) Na₂O/g]	468	1300
Acid resistance DIN 12116 [mg/dm²]	0,4	0,9
Alkali resistance DIN/ISO 695 [mg/dm²]	96	250

Web page adapted from http://www.mikroglas.com
Last Updated Fri Apr 1 12:28:02 PST 2000

1. UV-Exposure In the exposure step, FOTURAN® glass is exposed to ultraviolet light at a wavelength between 290 - 330 nm. It is possible to illuminate material thicknesses of up to 2 mm. An energy density of approximately 2 Joule/cm² is sufficient to structurize a 1 mm thick FOTURAN® plate.
2. Heat treatment With the UV exposure step silver atoms are formed in the illuminated areas. During the heat treatment between 500^o and 600^oC the glass crystallizes around these silver atoms.
3. Etching The crystalline regions, when etched with a 10% solution of hydrofluoric acid at room temperature, have an etching rate up to 20 times higher than that of the vitreous regions. If wet chemical etching is supported by ultrasonic etching or by spray-etching, the resulting structures display a large aspect ratio.