Emir Mutapcic

Automated generation of NC part programs for excimer laser ablation micromachining from known 3D surfaces

The purpose of this research project is to improve the capability of the laser micromachinning process, so that any desired 3D surface can be produced by taking the 3D information from a CAD system and automatically generating the NC part programs. In addition, surface quality should be able to be controlled by specifying optimised parameters. This paper presents the algorithms and a software system, which processes 3D geometry in an STL file format from a CAD system and produces the NC part program to mill the surface using the Excimer laser ablation process. Simple structures are used to demonstrate the prototype systems part programming capabilities, and an actual surface is machined.

3D visualization tool for excimer laser micromachining

This paper presents the results of our investigations on the laser micromachining of structures in a dry film photoresist polymer (Dynachem, Laminar AX dry film) laminated on a copper clad Printed Circuit Board (PCB) and (100) Silicon wafer coated with Ti (15nm)/Cu (100 to 4000 nm) and copper seed layers. This study concentrated on investigating and comparing the effect of laser fluence (0.01 to 2 J/cm2) and number of shots (1 to 1000) on the etch characteristics of the Laminar AX dry film on both substrates. The other important aspects that were studied include the minimum required seed layer thickness for electroplating.The removal of the residual polymer layer at the end of the laser micromachining process and its effect on plating characteristics has been studied. The surface quality and roughness of the laser micromachined sites and their effect on the plated Nickel structures have also been investigated. The laser fluence and the number of shots used at this stage affected the conditions of the seed layer, which in turn influenced the plated film growth kinetics. The seed layers with thicknesses less than or equal to 0.8 µm were completely removed when high fluence (< around 1 J/cm2) was used. The seed layer surface after micromachining was characterised using Scanning Electron Microscopy (SEM), Xray photoelectron spectroscopy (XPS) and profilometer. High Aspect Ratio Structures (HARS) of Nickel were fabricated using the Laminar AX moulds. The highest aspect ratio achieved so far in this work is 6. The characteristics of these structures are discussed in detail.

A novel CAD/CAM tool for excimer laser ablation-machining process

This paper reports on the development of a novel software system for excimer laser ablation machining processes. The system’s algorithms use the 3D geometry of a microstructure, defined in a CAD model, and parameters that influence the process (etch rate, wall angle, stitching errors, etc) to automatically generate a precise NC part program for the excimer laser machine. The algorithms and a prototype software system have been developed for the step-and-repeat laser ablation technique and extended to include the workpiece-dragging technique. The latter, achieves both higher surface accuracy and smoothness within the sub-micron range. The algorithm enables various mask sizes to be used to control accuracy of the machined part and development includes tool path optimisation and processing time reduction. The software simplifies part program creation and is useful for excimer laser operators who currently use a tedious trial and error process to generate microstructure parts. The benefits of the software include more accurate microstructures and reduced overall costs of the process itself. The performance of the system has been verified by NC part program generation for several 3D microstructures and subsequent machining trials. The analysis of stitching and edge errors is reported, and comparisons of 3D models with the machined surfaces are given. Microstructures were analysed using Scanning Electron Microscopy (SEM), Laser Scanning Confocal Microscopy (LSCM) and optical microscopy.This paper reports on the development of a novel software system for excimer laser ablation machining processes. The system’s algorithms use the 3D geometry of a microstructure, defined in a CAD model, and parameters that influence the process (etch rate, wall angle, stitching errors, etc) to automatically generate a precise NC part program for the excimer laser machine. The algorithms and a prototype software system have been developed for the step-and-repeat laser ablation technique and extended to include the workpiece-dragging technique. The latter, achieves both higher surface accuracy and smoothness within the sub-micron range. The algorithm enables various mask sizes to be used to control accuracy of the machined part and development includes tool path optimisation and processing time reduction. The software simplifies part program creation and is useful for excimer laser operators who currently use a tedious trial and error process to generate microstructure parts. The benefits of the software inc...

A comparison of 355NM and 248NM laser ablation of PET for microfluidic applications

PET has proven itself as an important material for the fabrication of microfluidic based lab-on-a-chip devices due to its’ chemical resilience, mechanical stability, and compatibility with laser microfabrication techniques. Here, we compare the results of laser beam interaction with the material using two different lasers; a frequency tripled Nd:YAG (λ=355nm) and the KrF excimer (λ=248nm) lasers. Results are presented demonstrating the processing issues, minimum feature sizes, thermal effects, surface roughness, and surface chemistry.The surface properties are of particular relevance to the microfluidic applications where surface to volume ratios are extremely high. X-ray photo-electron spectroscopy (XPS) has shown that both 355nm and 248nm ablation of PET increases the percentage ratio of carbon:oxygen, in agreement with similar analyses performed by others [1,2]. This results in an increased hydrophobicity, but redeposition of material during the excimer machining process leaves a measurably less hydrop...