Glass
Soda Lime Glass
this is the most common substrate used for masks, due to its good quality/price ratio. The glass is optically good, very flat, and has no imperfections. When covered in chrome, the mask is very durable and hard-wearing, and can easily cope with many contact print / clean processes due to its robustness. Exhibits high transmission in the visible range but shows significant absorption in the ultraviolet (UV) region below approximately 350 nm
Soda Lime Glass has a medium thermal co-efficient expansion (which means it is not perfectly dimensionally accurate in differing environments).
- Excellent price/quality ratio
- Easy to clean
- Relatively stable
- Wavelength 350nm +
- Fits common equipment
- Can break
Quartz
sometimes called Fused Silica; is equally a very good substrate, and probably the most common for ‘high-end’ applications such as semiconductor chips.
There are a couple of mechanical benefits of quartz over standard soda lime glass – firstly the quartz material is optically pure, with a very high transmission of light even at very low UV wavelengths. The second major benefit of quartz is that it has extremely low thermal expansion, and remains dimensionally stable even in extreme temperatures, which also impacts its thermal shock resistance which is very high because very little expansion takes place. Offers excellent transmission from the UV region around 200 nm through the visible spectrum and into the near-infrared (NIR) region, maintaining high transmission up to approximately 2000 nm.
Quite often, quartz is the chosen substrate used in laser ablation applications, where low wavelengths are used to project through the mask and ablate the surface of various materials.
- Optically pure
- Transmission from 200nm
- Thermally stable
- Can break
- Relatively expensive
Boroscilicate
This is also known for having low coefficients of thermal expansion, appearing somewhere between the range of Soda Lime and Quartz. Normally this would make it an ideal substitute for Soda Lime glass, but the manufacturing process of the glass means that often their can be inclusions and bubbles in the glass which does not lend perfectly to high optical demands. Provides good transmission in the visible and NIR regions, with a transmission range extending from about 310 nm to 2700 nm.
- Low thermal expansion
- Easy to clean
- Low quality purity of material
- Not commonly held in stock
- Can break
B270 Glass
This is also known as “white crown glass” . This does not mean that it is white in colour (please see our alternative materials if you require “white glass”)
The “white” refers to the fact that it is optically clear, which is in part due to the fact that during manufacture most of the non-silicate particles are removed, so the high silica content makes it very optically pure. However, the drawback of the manufacturing process means that it is difficult to cut into smaller shapes, and also the cost is much higher than soda lime glass even though the composition is very similar. For that reason, Soda Lime glass is often chosen. Demonstrates high transmission in the visible spectrum, typically from 350 nm to 2000 nm, making it suitable for a variety of optical applications.
- Easy to clean
- Optically clear
- Difficult to cut
- Not commonly held in stock
- Can break
