The current and next generation of micro-engineered products, such as sensors, motors and pumps, will require very small (10-1000µm) and precise two and three dimensional components to be machined in materials such as silicon, metals, polymers, ceramics and glass.
Lasers can play an important part in the production of such products, and lasers for these applications require very small focused spot diameters, controlled energy output, high pulse repetition rates and accurate alignment capability.
The solid state pulsed Nd:YAG laser is a versatile materials processing tool. TWI has recently acquired a Spectron Laser Systems series SL 800 Nd:YAG laser. This is equipped with a series of crystals which, when included in the beam path, can alter the output wavelength of the laser. By using this 'frequency multiplying' technique the Spectron laser can lase at the fundamental Nd:YAG wavelength of 1064 nanometres, as well as at 532, 355 and 266 nanometres. These shorter wavelengths can be focused to small spots and interact very differently with materials.
Most 'frequency multiplied' Nd:YAG lasers are developed with a fixed set of process parameters for specific processes. The Spectron laser at TWI is equipped with facilities to change pulse energy, pulse repetition rate and pulse width, as well as wavelength making this laser a very flexible tool for process feasibility and product development work.
Recent work has demonstrated the laser's capability for fine scale ablation. The task was to take a 2.5mm diameter Alumina rod 5mm long and ablate the silver film coating to produce a series of isolated conductive tracks. A series of nine longitudinal tracks, each of 100µm wide were successfully produced using 266 nanometres wavelength, pulse energy - 40mJoules, pulse width - 15ns, pulse repetition rate 10Hz and a traverse speed of 50mm/min.
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