Comparing Laser Types — continued

Consider the following two examples of excimer laser machining compared to CO₂ and Nd:YAG.

CO2	Excimer

As you can see, there is a marked difference in the resolution of the cuts. The following comparison shows 300µm-diameter holes drilled in 75µm thick polyimide.

Nd:YAG (IR)	CO2	Excimer

In both examples it is clear that the excimer laser is better suited to high-precision micromachining. CO₂ and Nd:YAG lasers produce round spots suited to drilling, welding and profile cutting.

While the high average power and lower feature resolution make CO₂ and Nd:YAG laser systems well-suited to heavy industrial applications, excimer lasers are often the only efficient, practical and cost-effective manufacturing method available for high-precision micromachining applications.

While CO₂ and Nd:YAG lasers generate thermal effects that can affect surrounding materials, excimer laser beams do not generate heat. Instead, they turn materials directly into gas by breaking chemical bonds, a process called photo-chemical ablation, that provides cleaner, more precise cuts.

The following specifications typify excimer lasers:

• Active medium: Noble and halogen gas pump pressure mixture
• Pump scheme: High-speed transverse electrical discharge
• Wavelength:157nm to 351nm, depending on gas mixture
• Pulse energy: 0.1 to 1 Joules
• Pulse duration: 10 to 50ns
• Peak power: 107 watts
• Pulse repetition rate:50 to 400 PPS
• Average power: 25 to 150 watts

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