4M Knowledge base - papers

H. Willeck(a), W. Eberhardt(a), H. Kück(b)
a: Hahn-Schickard-Institute of Microassembly Technology HSG-IMAT, Stuttgart, Germany
b: University of Stuttgart, Institute of Micro and Precision Engineering, Germany

Abstract

Through miniaturisation and 3D capability moulded interconnect devices (MID) offer great opportunities for various applications in a broad industrial field. Especially, when applying the laser-direct-structuring process of the company LPKF (LPKF-LDS® process) fine conductors can be fabricated on thermoplastic substrates. A main criterion for the industrial application is the adhesive strength of the conductors. As for LDS MID there is currently no suitable test method for directly determining the adhesive strength of conductors. Therefore, a measuring device consisting of a sensor and peel off unit has been developed at HSG-IMAT. It has been used to investigate a measuring principle utilising a peel off chisel for adhesion determination. Promising and repeatable results have been obtained by testing conductors on thermoplastic substrates.

Richard Thelen (a), Joachim Schulz (a), Pascal Meyer (a), Volker Sailea (a)
(a) Institute for Microstructure Technology, Research Centre Karlsruhe, 76646 Eggenstein, Germany

Abstract

Reproducibility and precision of LIGA structures has been claimed in many publications, founded mainly on brilliant pictures. Because of the poor accessibility to the sidewalls many publications are based on surface measurements without including information about z depending aspects [1] and focus on reproducibility as measured close to the top.
Often this neglects operator’s influence, short time and long time reproducibility, environmental effects on the CMM and others. Tactile optical metrology might help to overcome 2D measurements. Repeatability of tactile optical metrology at IMT was proven to be less than 0,3 μm over some months using ultra fine probes with less than 25 μm diameter. In addition DoE was used to determine the minimum deviation for best possible machine settings. Standard Deviation between 50 and 30 nm was measured. Compared to that, uncertainty remains about 1-2 μm for 3D measurements even with z maximum restricted to 1 mm [2]. Not enough to measure sub-μm product variation that is a typical benefit of LIGA products.
Investigations were started at the Research Centre Karlsruhe to find out more about the effects influencing the measurements to explain why repeatability and capability do not match. Interaction between sample and sensor was the main reason. This was simulated and the results were used to reduce the uncertainty of the system. IMT elaborated a new strategy that improves the capability of a coordinate measurement machine CMM with tactile optical sensor for LIGA parts with sub μm variation.

A. Temun, L. Mattsson

Department of Production Engineering, KTH – the Royal Institute of Technology, SE-100 44 Stockholm, Sweden

Abstract

Evaluation of three digital cameras are presented focusing on their capabilities and applicability in the detection of low-contrast surface features on the micrometer level. The key to a successful identification of surface flaws on micro-structured surfaces, such as silicon wafers is the ability to determine minor deviations in the reflectance of an object surface. Micro-topography of a surface, surface structure and surface roughness has a strong influence on the amount and direction of scattered light. Different portions of the surrounding illumination are reflected on different parts of an uneven surface, hence the resulting contrast-variation on the illuminated surface has a strong correlation to the surface structure itself.

In our work we discuss the possibilities of using either of the investigated cameras for the automated visual inspection of micro-structured surfaces. The cameras - two of them equipped with CCD and one with CMOS image sensors - are studied in an environment which is similar to standard surface appearance measurements, involving human observers. The specimens, featuring different surface structures are imaged in a well-controlled environment under varying illumination conditions. Experimental results of spatial resolution and contrast sensitivity are presented.

C. Ferri, E. Brousseau
Manufacturing Engineering Centre, Cardiff University, CF24 3AA, UK

Abstract

This paper presents a spline-based calibration method in order to overcome the limitations observed in the built – in calibration procedure of a commercial white light interferometer microscope. Quantitative experimental evidence highlighted the presence of inconsistencies of this built-in procedure with the international standard about the linear calibration method. A bias in the measurement results was shown experimentally. The proposed spline-based approach was implemented with reference materials of nominal heights ranging from 182 to 218 μm. The state of control of the measuring process during a calibration and between calibrations was also monitored using purpose developed control chart designs.

H.N. Hansen
Department of Manufacturing Engineering and Management, Produktionstorvet, Building 427S, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark

Abstract

The need for dimensional metrology at micro and nano scale is evident both in terms of quality assurance of components and products and in terms of process control. As critical dimensions are scaled down and geometrical complexity of objects is increased, the available measurement technologies appear not sufficient. New solutions for measuring principles and instrumentation, tolerancing rules and procedures as well as traceability and calibration are necessary if micro manufacturing is to develop into industrial manufacturing solutions. The current paper describes issues and challenges in dimensional metrology at micro scale by reviewing typical measurement tasks and the measuring capability of available instrumentation. Traceability and calibration issues are discussed subsequently. Finally needs and gaps are identified based on these observations.