4M Knowledge base - papers

W. O’Neill, K. Li, Q. Hu, P. Chopra, J. Kanghee, A. Buntardjo
Institute for Manufacturing, University of Cambridge, Cambridge, CB2 1RX, UK

Abstract

The advances in design, performance, cost reduction, and brightness for the modern Yb fiber laser have opened up the possibility of redefining the micro processing options for a range of semiconductor materials and micro fabrication production techniques at a wavelength of 1064nm. The usual laser of choice for micro electronics processing is the 532, 355, or 266 nm DPSS system. The provision of a new MOPA high brightness Yb based fiber laser configuration has provided a range of pulse parameters (10-200 ns FWHM), peak powers approaching ~ 2G Wcm^(-2) , and pulse repetition rates up to 500 kHz. These processing parameters offer a broad range of material response characteristics. This paper provides a preliminary analysis of the use of a Yb based fiber laser in the production of Si and Glassy Carbon microstructures and explores the potential of this source for low cost micromachining solutions.

P V Petkov, S S Dimov, R. Minev and D T Pham
Manufacturing Engineering Centre, Cardiff University, Queen’s Building, Newport Road, The Parade, Cardiff, CF24 3AA, UK

Abstract

Laser milling of engineering materials is a viable alternative to conventional methods for machining complex micro components. The laser source employed to perform such micro structuring has a direct impact on achievable surface integrity. At the same time, the trade offs between high removal rates and the resulting surface integrity should be taken into account when selecting the most appropriate ablation regime for performing laser milling. In this paper the effects of pulse duration on surface quality and material microstructure are investigated when ablating a material commonly used for manufacturing micro tooling inserts. When performing ultra short pulsed laser ablation some heat is dissipated into the bulk but not sufficient to trigger significant structural changes.

P V Petkov, S Scholz and S Dimov
Manufacturing Engineering Centre, Cardiff University, Queen's Buildings, The Parade, Newport Road, Cardiff, CF24 3AA, UK

Abstract

Laser milling with microsecond pulses is a thermal material removal process usually associated with detrimental effects such as heat affected zones (HAZ), a recast layer and debris. Process optimisation can lead to considerable reduction of the above mentioned negative effects. In this context, the research investigates the effects of tool path optimisation and material removal strategies on the resultant surface quality and edge definition. The conducted experimental study shows clearly that the applied milling strategies have a significant effect on the resulting surface topography and the edge definition. Also, the research demonstrates that by optimising the laser path and material removal strategies it is possible to reduce significantly the thermal load when milling micro features, and thus to minimise HAZ and other secondary effects.

G. Lalev (1), P. Petkov (1), N. Sykes (2), V. Velkova (1), S. Dimov (1), D. Barrow (2)

(1) Manufacturing Engineering Centre, Cardiff University, Newport Road,Cardiff, CF24 3AA, UK
(2) metaFAB, Cardiff University, Newport Road, Cardiff, CF24 3AA, UK

Abstract

A cost effective methodology for pattering of Nano Imprint Lithography (NIL) templates with different length scale features is proposed. The approach relies on selecting the optimum processing window of different technologies for cost effective micro and nano patterning. Very promising results were obtained when first fused silica templates were structured by F2 laser ablation at 157 nm without inducing phase transformation of the material. It was demonstrated that nanoscale features and complex 3D microscale features could be machined with a Focused Ion Beam (FIB) over the existing topography produced by laser ablation. Thus, a large area (up to several square centimetres) of the NIL templates is easily patterned with micro- and even meso-scale features by laser ablation while nano- and micro-scale features could be introduced by FIB machining.