Marcel Tichem

A classification scheme for quantitative analysis of micro‐grip principles

This paper proposes a classification scheme for the quantified analysis of micro‐grip principles. Micro‐part gripping has received quite some attention in micro‐assembly research. However, there is a lack of quantified data on the characteristics and applicability of micro‐grip principles. The micro‐grip principle is the physical principle that produces the necessary forces to get and maintain a part in a position with respect to the gripper. The classification scheme defines criteria that are essential in the evaluation and selection of a micro‐grip principle for gripping a given part. The criteria are defined on the basis of characteristics of the parts to be gripped, demands on the grip operation to be performed and characteristics of the environment in which the grip operation takes place. The classification scheme is evaluated using examples from literature.

Designer support for product structuring—development of a DFX tool within the design coordination framework

Abstract This paper presents results of a continuing research project, which aims at the development of supporting tools for designers in the structuring of products, taking into account a number of life-cycle considerations. The structure of a product is a context-dependent description of the composition of the product out of elements and relations between the elements. The main issue of the paper is a model of the design process which serves as a basis for developing supporting tools. The model of the design process presented here is based on the desire to give design-problem specific support to the designer through the entire design process. The model consists of three main elements: execution of design activities, results of design activities, and coordination of design activities. Based on the model of the design process, the functionality of a computer-based supporting tool is discussed.

In-package MEMS-based thermal actuators for micro-assembly

The paper describes the first fabrication and experimental results in the on-going development of MEMS-based electrothermal actuation devices for lateral XY positioning of an optical fibre to a laser diode chip to improve their coupling efficiency and reduce the overall packaging cost. The deflection performance of bulk silicon U- and V-beam thermal actuators with and without fibre loading has been experimentally determined. This is a part of an investigation of the feasibility of an alternative method of performing micro-assembly tasks, i.e. by means of product-internal assembly functions.

An improved in-plane thermal folded V-beam actuator for optical fibre alignment

This paper presents an improved thermal actuator design, providing high work per unit of chip area. The actuator was developed for high accuracy fibre alignment. This application requires that the fibre tip is moved by pushing close to its end, posing geometric design constraints on the actuator design. The basic structure of the actuator is a parallelogram, consisting of a non-moving base, a bar parallel to the base placed orthogonal to the fibre axis in contact with the fibre, and heater arms and reinforced restraining arms which connect the base and the bar. The heater arms thermally expand when passing a current through them. On either side of the heater arms there is one restraining arm, placed at a slightly different angle with the base and bar than the heater arms. The restraining arms do not heat up, and constrain the motion due to thermal expansion of the heater arms, resulting in a motion of the bar in its longitudinal direction. The performance of this actuator is compared to two well-known alternative thermal actuator configurations. Comparison shows that the improved actuator delivers 15% more work per area, and is therefore considered an attractive alternative solution for purposes such as in-plane optical fibre alignment.

Two-Dimensional Fiber Positioning and Clamping Device for Product-Internal Microassembly

In this paper, we present a microelectromechanical systems-based two-degrees-of-freedom positioning device combined with a clamping structure for positioning and constraining an optical fiber. The fiber position can be controlled in the two directions perpendicular to the fiber axis using two specifically designed wedges that can be accurately moved in-plane. These wedges are positioned using in-plane thermal actuators. Actuation of a fiber tip greater than 25 mum in-plane and 40 mum out-of-plane is achieved with a displacement resolution better than 0.1 m. After aligning the fiber the final position can be maintained by switching off the mechanical clamp, which also uses thermal actuators. The position of the fiber can be kept within 0.1 mum after switching off the mechanical clamp and the positioning actuator. Fiber-to-fiber alignment experiments have been performed and the technique can be extended to fiber-to-laser alignment.

A contact position detection and interaction force monitoring sensor for micro-assembly applications

This paper presents a piezoresistive sensor for micro-assembly application, which is capable of detecting the contact position of the micro-object on the grasping surface as well as the grasping force. By comparing the outputs of a local 2D force sensor and a global force sensor, the 2D contact position on the grasping surface and the contact force can be extracted. The device is fabricated with an IC-compatible process and can be integrated into micro-grippers. The measurement results show that different contact positions can be distinguished. The device is suitable to detect a contact force up to 4 mN, with a sensitivity of 16.4 V/N. The estimated force resolution is 1 µN.

First investigations on force mechanisms in liquid solidification micro-gripping

The paper reports on ongoing research on liquid solidification based micro-gripping. First, micro-grip technology and the features of liquid solidification gripping are introduced. Next, the physical mechanisms of adhesion in terms of the role they play in solidification gripping are described. A research prototype design and first experimental results, focused on the grip force that can be generated, are then reported on. It is shown that the main parameters which influence the grip force are the surface roughness of the part, the material combinations and freezing temperature. Forces are measured in the range of 0.6 up to 5.3 N with a contact area of about 1 to 2 mm2

Fabrication and characterization of suspended beam structures for SiO2 photonic MEMS

This paper proposes a microfabrication process for the reliable release of SiO2 beam structures. These structures are intended to be utilized in SiO2 photonic MEMS. A major fabrication challenge is the release of thick (>10 ?m) SiO2 structures with high yield. A single mask process is developed based on temporary reinforcement of the SiO2 structure. A supporting layer of Si functions as a reinforcing layer during etching and release, thereby enabling a high fabrication yield. Furthermore, the process allows to create structures of which the final Si support thickness is configurable from tens of micrometers to zero, thereby providing additional design freedom. The fabrication process is tested on a silicon wafer with a ?15 ?m thick thermal oxide layer. The obtained suspended structures are mechanically characterized. Two deformation effects can be distinguished: a curvature of the beam and a slope at the base of the beam. These effects are caused by the compressive mean stress and the gradient stress in the thermal SiO2. The curvature of the SiO2–Si beams corresponds to a concave downward profile while the SiO2 beams without supporting Si reveal a small curvature in the opposite direction (concave upward). The slope at the base is approximately ?0.5° for the SiO2 beams and between ?0.5° and 0° for the SiO2–Si beams. The acquired bending stiffness of long SiO2 beams is in the newton per meter range (e.g. 0.8 N m?1 for a cantilever measuring 1000 ?m in length and 13 ?m in width).

Magnetic Self-Assembly of Ultra-Thin Chips to Polymer Foils

A self-assembly process is developed for the placement and alignment of Ultra-Thin Chips (UTCs) to polymer foils. The chips are presented within the working range of a magnetic force field, and subsequently driven to and aligned at a target location. A low-viscosity die attach adhesive layer supports chip mobility during alignment, and is UV-cured after assembly to generate a mechanical bond. An adaptive electrical interconnection scheme compensates the position errors present after assembly. Standard Ni + Au bumps provide sufficient magnetization to generate the required alignment force. Numerical modeling confirms that over a long range magnetic forces operate on a chip and drive it to a target location. Also, an asymmetric bump arrangement supports achieving a unique in-plane orientation. Experimentally, chips with a thickness of 20 μm were successfully trapped and aligned with a repeatability of ±100 μm in x and y-direction, and the best achieved cycle time is below 1.0 s. The cycle time depends considerably on the viscosity of the die attach adhesive. The presence of unique in-plane orientations, depending on the bump arrangement, is demonstrated.

Passive Photonic Alignment With Submicrometer Repeatability and Accuracy

In this paper, we report on passive alignment with submicrometer accuracy of two photonic chips on a silicon optical bench. An effective design principle to minimize the tolerance chain is presented and applied to a case study. The chips have been successfully manufactured and an experimental setup has been made that can precisely assemble the chips and evaluate the alignment performance based on the camera images and coupling efficiency. It was demonstrated that passive alignment features defined in the waveguiding layers are robust enough to function as mechanical endstops. Subpixel image analysis of assembled chips showed that a 3σ chip-to-chip repeatability better than 500 nm can be achieved. Finally, based on optical coupling measurements, an absolute alignment accuracy of 670 nm has been concluded.