Part tilting in capillary-based self-assembly: Modeling and correction methods (original) (raw)
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Self-assembly of microsystem components with micrometer gluing pads through capillary forces
Journal of Manufacturing Processes, 2020
The self-alignment of microparts based on capillary forces and micrometer adhesive pads was evaluated through experimental evidence, analytical modelling and simulation. The local deposition of adhesive pads in the range of 2000 to 20 μm was realized by photo-lithographical patterning of an acrylate adhesive interlayer, followed by the spontaneous assembly with glass counterfaces that have a complementary array of hydrophobically modified gold structures. The design rules for self-alignment of microparts were studied from calculations of the capillary force and displacement as a function of the adhesive pad dimensions, pad heights and offset length. In all cases, the self-alignment induced by capillary forces is driven by a minimization of the surface energy, leading to an equilibrium position. The analytical results provided good qualitative understanding of the alignment process: larger dimensions, smaller separation and higher offset values contributed to higher forces and fast alignment. The simulation experiments in Surface Evolver were based on calculated geometries of adhesive pad providing a minimum surface energy and also take into account the local deformation of the adhesive pad together with an additional degree of rotational freedom. Consequently, the latter results indicated a high degree of precision with good correlation to the experiments and analytical results.
Multi-batch micro-self-assembly via controlled capillary forces
… and Systems, 2001. …, 2001
Recent advances in silicon processing and microelectromechanical systems (MEMS) have made possible the production of very large numbers of very small components at very low cost in massively parallel batches. Assembly, in contrast, remains a mostly serial (i.e., nonbatch) technique. In this paper, we argue that massively parallel selfassembly of microparts will be a crucial enabling technology for future complex microsystems. As a specific approach, we present a technique for assembly of multiple batches of microparts based on capillary forces and controlled modulation of surface hydrophobicity. We derive a simplified model that gives rise to geometric algorithms for predicting assembly forces and for guiding the design optimization of selfassembling microparts. Promising initial results from theory and experiments and challenging open problems are presented to lay a foundation for general models and algorithms for selfassembly.
Challenges for capillary self-assembly of microsystems
2011
Within the currently rising trend of heterogeneous microsystem integration and packaging, capillary self-assembly emerges as an innovative technique to enhance, complement and eventually replace pick-and-place assembly. Vast literature and experimental data support such claim. Still, the technique needs to overcome some important limitations in order to fully express its potential and earn wide industrial recognition. In this paper, we review and illustrate what are in our opinion the challenges ahead for making part-to-substrate capillary self-assembly reliable and seriously competitive with long-established assembly techniques. After setting self-assembly methods in the context of microsystem assembly and integration technologies, we focus on the standard embodiment of capillary self-assembly, and we describe in details the main, often novel technological steps required for its effective and reproducible performance. This preludes to an outline of what are presently, in our view, the major failure modes affecting the overall yield of the capillary self-assembly technique. Consequently, we propose solutions to face and overcome these challenges, which need to be met to foster the success of this technique.
Concept for Fluidic Self-Assembly of Micro-Parts Using Electro-Static Forces
Self-assembly is relatively unused in industrial micro-fabrication, although it offers opportunities to simplify processes and to lower manufacturing costs. A variety of self-assembly procedures have been introduced that take advantage of various forces, e.g. capillary, gravitational, electro-static. In this paper a concept for the alignment of micro-parts on a substrate using fluidic-self-assembly with electro-static attraction is presented. Further, FEM-simulations for the electro-static alignment force are performed and its dependence on several geometric parameters, e.g. the width of the binding sites and the distance between micro-part and substrate at the binding sites, is investigated. Based on results an analytic model is extracted. Furthermore, simulations are also performed to estimate capillary alignment forces, acting on micro-parts that are self-aligned. Finally, the magnitude of electro-static and capillary forces is compared. This novel assembly concept, where the ali...
Precision Engineering
Self-assembly of components using liquid surface tension is an attractive alternative to traditional robotic pick-and-place as it offers high assembly accuracy for coarse initial part placement. One of the key requirements of this method is the containment of the liquid within a designated binding site. This paper looks to expand the applications of self-assembly and investigates the use of topographical structures applied to 3D printed micro components for self-assembly using liquid surface tension. An analysis of the effect of edge geometry on liquid contact angle was conducted. A range of binding sites were produced with varying edge geometries, 45-135°, and for a variety of site shapes and sizes, 0.4 - 1 mm in diameter, and 0.5 × 0.5–1 × 1 mm square. Liquid water droplets were applied to the structures and contact angles measured. Significant increases in contact angle were observed, up to 158°, compared to 70° for droplets on planar surfaces, demonstrating the ability of these ...
2010 IEEE 23rd International Conference on Micro Electro Mechanical Systems (MEMS), 2010
This paper presents a novel method to achieve high yield assembly of millimeter-scale thin silicon chips from an air-water interface. Surface functionalized silicon parts (1000!1000!100 !m 3 ) assemble in preprogrammed hydrophilic locations on a wafer substrate with self-alignment. We optimized the process and design factors systematically using DOE (Design of Experiment) that leads to high yield (100 %).
Electrostatic attraction and surface-tension-driven forces for accurate self-assembly of microparts
Microelectronic Engineering, 2010
Self-assembly is not widely used in industrial micro-fabrication, although it can potentially involve assembly processes that are considerably less complex. A variety of procedures for self-alignment of parts have been introduced and investigated lately. These procedures mainly utilise capillary, gravitational or electrostatic forces in the micro-scale. This paper investigates two different concepts for accurate selfassembly of parts. One is well described in the literature by third parties and involves the alignment of parts by utilising the surface tensions of micro-scaled adhesive films, which are selectively coated on hydrophobic alignment structures. In the present publication the influence of the dimensions of such structured alignment sites on the process flow is discussed. The second concept is a novel approach to accomplish self-alignment of micro-structures with electrostatic attraction. Several complementary and electrically conductive micro-structured patterns serve as binding sites for the alignment of parts in this approach. In order to obtain knowledge of how these two approaches operate, they have been modelled and simulated. Additionally, in order to analyse the feasibility of these procedures and to verify simulation results experiments have been performed on micro-structured parts and substrates. In particular, the layout of the alignment structures and the size of the parts were identical for both described concepts in the experimental work; therefore, these two methods were compared. With the self-assembly procedure that utilises electrostatic attraction, high alignment accuracies and forces, affecting the part over large distances, were observed. Finally, parts with micro-structured binding sites, which were as small as 10 Â 10 lm 2 , could accurately be self-aligned with electrostatic attraction.
Self-alignment of silicon chips on wafers: A capillary approach
Journal of Applied Physics, 2010
As the limits of Moore's law are approached, 3D integration appears as the key to advanced microelectronic systems. Die-to-wafer assembly appears to be an unavoidable step to reach full integration. While robotic methods experience difficulties to accommodate fabrication speed and alignment accuracy, self-assembly methods are promising due to their parallel aspect which overcomes the main difficulties of current techniques. The aim of this work is the understanding of the mechanisms of self-alignment with an evaporating droplet technique. Stable and unstable modes are examined. Causes for misalignments of chips on wafers and their evolution are investigated with the help of the Surface Evolver numerical software. Precautions for suitable alignment are proposed.