Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, that is, in the range between 400 nm and 10 nm, corresponding to photon energies from 3 eV to 124 eV.

UVA ( Curing )

Name Abbreviation Wavelength (nm) Energy (eV)
Ultraviolet A (long wave, or black wave) UVA 315mn - 400nm 3.10 - 3.94eV
Ultraviolet B (medium wave) UVB 280nm - 315nm 3.94 - 4.43eV
Ultraviolet C(short wave, or germicidal) UVC 200nm - 280nm 4.43 - 12.4eV
Vacuum Ultraviolet VUV 100nm - 200nm 6.20 - 124eV

Ultraviolet A (UVA 315-400nm) is used for low energy UV polymerization reactions in the bonding and curing of various materials, and is also used in non-destructive fluorescent inspection methods. Photons in the UVA (315-400 nm) promote through cure, especially with thicker film layers.

Ultraviolet B B (UVB 280-315nm) is used along with UVA for polymerization and since it is the most energetic region of natural sunlight, for accelerated light aging of materials Photons in the UVB (280 - 315 nm) contribute to bulk cure.

Ultraviolet C (UVC 100-280nm) is used for rapid surface cure of UV inks and lacquers, and is also used in the sterilization and germicidal processes and applications, the most energetic of the wavelengths used in UV curing. Photons in the UVC are important for surface cure and promote surface properties such as hardness, stain resistance, and abrasion resistance.

Vacuum Ultraviolet (VUV 10-200nm) can only be used in a vacuum, however, they have very significant commercial importance. As is well know from Moore's law, microelectronics can address smaller and smaller dimensions. Currently 193nm and 157nm are most important for making 65-30nm nodes. [Nitrogen does not strongly absorb VUV. Actually nitrogen is the most popular "purging gas" to prevent VUV being absorbed by oxygen.

UV-LED Technology

UV-LED Application

Chip Process

Soft-Epi Inc is basically pursuing flip-chip process for manufacturing UV LED chips and packaging. Flip-Chip process has very excellent reliability and thus produces stable high power devices.

Lateral Chip Vertical Chip Flip-Chip
Merits - Normal Process
- High Reliability
- High components per chip
- Profitableness for High Power Device
- Normal Process
- High Reliability
- Profitableness for High Power Device
Demerits - Low components per chip
- Difficulty for High Power Device
- Specific process
- Low Reliability
- High Cost
- Complicated manufacturing process (relative to lateral chip)
Cost - Low Cost - High Cost - Medium Cost
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