4M Knowledge base - papers
Georgi Lalev(a), Stefan Dimov(a), Jeff Kettle(a), Falco van Delft(b) and Roussi Minev(a)
a: Manufacturing Engineering Centre, Cardiff University, Queen's Buildings, The Parade, Newport Road, Cardiff, CF24 3AA, UK
b: Philips Research Europe, MiPlaza, High Tech Campus 4, 5656 AE Eindhoven, The Netherlands
The realization of complex three-dimensional structures at micro- and nano-meter scale in various materials is of great importance for a number of micromechanical, microoptical and microelectronic applications. Focused Ion Beam (FIB)patterning is one of the promising technologies for producing such 3D structures utilizing layer-by-layer fabrication methods. A novel and efficient data preparation approach is proposed in this paper for layer-based FIB processing. By applying it, complex surfaces can be designed easily in any 3D CAD package and then converted into GDSII streams for FIB sputtering or deposition. To validate the proposed CAD/CAM approach an experimental study was conducted.
The factors that can affect the accuracy of the structures produced by layer-based FIB processing are also discussed. By assessing all stages of the proposed approach and the results of its experimental validation, conclusions are drawn about its applicability.
T Dobrev, D T Pham and S S Dimov
Manufacturing Engineering Centre, Cardiff University, Cardiff, CF24 3AA
In pulsed laser material removal systems, it is very important to understand the physical phenomena that take place during the laser ablation process. A two-dimensional theoretical model is developed to investigate the crater formation on a metal target by a microsecond laser pulse. The model takes into account the absorption of the laser light, and heating and vaporisation of the target, including an adjustment to compensate for the change of state. A simple numerical technique is employed to describe the major physical processes taking part in the laser milling process. The temperature distribution in the target material during the pulse duration is analysed. The effect of the laser fluence on the resulting crater is investigated in detail. The proposed simulation model was validated experimentally for laser material interactions between a microsecond Nd:YAG laser (λ= 1064 nm) and a stainless steel workpiece. The measured crater depths are in agreement with the model. Such a study is very important for understanding the mechanisms of micro-structuring when laser milling is employed. The results of this research will be used in improving the micro-machining capabilities of the process.
D. Karnakis, G. Rutterford, M. R. H. Knowles
Oxford Lasers Ltd., Unit 8, Moorbrook Park, Didcot, Oxfordshire OX11 7HP, UK
We describe high power diode-pumped solid-state (DPSS) laser micro-machining results of commonly used industrial materials such as stainless steel and silicon. Frequency up-converted lasers were used at 532nm and 355nm. We discuss the benefits of high laser intensity (~ GW/cm2) micro-machining for efficient laser microfabrication.
At such high irradiance conditions material properties are approaching their critical limits and ablation mechanisms are complex. These can be exploited to our advantage in particular for micro-drilling and micro-cutting small feature sizes in the order 10-20 μm and high aspect ratios of up to 20:1. Etch rate data are presented and a comparative study of the ablation efficiency in these materials is discussed. Results of single shot and multiple shot ablation are also presented. The potential applications of this technology to device singulation for electronic and power generation devices will be described.
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
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.
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