Bertram Schmidt

A new device with PZT ultrasonic transducers in MEMS technology

Thick-film piezoelectric transducers have been produced and tested for implementation into a MEMS ultrasonic sensor array. The arrays are intended to be used for beam forming in sensing applications for fluidics in channels at millimeter or micrometer scale (e.g. flow rate measurement, detection of beads, bubbles). Stripe and matrix aligned elements have been fabricated for one-dimensional and two-dimensional beam steering, respectively. In this contribution we further concentrate on an improved Q-factor and PZT layer homogeneity as a major requirement for the transducer elements.

Development of micromachined switches with increased reliability

By micromachining of silicon and glass, an electrical switch with low-resistance metal contacts was made. The switch is aimed at applications as a binary pressure sensor and to replace conventional push-button switches. First measurements on switches yielded electrical lifetimes over 10/sup 5/ cycles and contact resistance clearly below 1 /spl Omega/.

Electrostatically actuated micromirror devices in silicon technology

Micromirrors with a size of 1 to 3 mm for laser beam deflection are described. The mirrors are fabricated from single crystalline silicon using bulk micromachining, dry etching and anodic bonding and are actuated electrostatically.

A New Test Device for Characterization of Mechanical Stress Caused by Packaging Processes

This paper reports on a new method for estimation and minimization of mechanical stress on MEMS sensor and actuator structures due to packaging processes based on flip chip technology. For studying mechanical stress a test chip with silicon membranes was fabricated. A network of piezo-resistive solid state resistors created by diffusion was used to measure the surface tension pattern between adjacent membranes. Finite element method simulation was used to calculate the stress profile and to determine the optimum positions for placing the resistive network.

A multilayer process for the connection of fine‐pitch‐devices on molded interconnect devices (MIDs)

Purpose – The purpose of this paper is to present a new multilayer process for three‐dimensional molded interconnect devices (3D‐MIDs) that allows the assembly of modern area array packaged semiconductors.Design/methodology/approach – A new 3D‐MID multilayer process based on local overmolding is developed. To investigate this new process, a 3D demonstrator is designed, simulated and fabricated. Various technologies such as injection molding, maskless laser assisted electroless metallization, overmolding and laser via drilling are used.Findings – Using the new 3D‐MID multilayer process a 3D demonstrator with three metallization layers is fabricated. Injection molding simulation is utilized to ensure a feasible demonstrator design. It is shown that a surface laser treatment improves layer‐to‐layer adhesion during the process. Shear and pull tests prove the adhesion promotion. The 3D fine‐pitch‐metallization is done down to 60 μm track width. Via resistance is measured by four terminal sensing in agreement w...

Resonant marker design and fabrication techniques for device visualization during interventional magnetic resonance imaging

Abstract Magnetic resonance imaging (MRI) has great potential as an imaging modality for guiding minimally invasive interventions because of its superior soft tissue contrast and the possibility of arbitrary slice positioning while avoiding ionizing radiation and nephrotoxic iodine contrast agents. The major constraints are: limited patient access, the insufficient assortment of compatible instruments and the difficult device visualization compared to X-ray based techniques. For the latter, resonant MRI markers, fabricated by using the wire-winding technique, have been developed. This fabrication technique serves as a functional model but has no clinical use. Thus, the aim of this study is to illustrate a four-phase design process of resonant markers involving microsystems technologies. The planning phase comprises the definition of requirements and the simulation of electromagnetic performance of the MRI markers. The following technologies were considered for the realization phase: aerosol-deposition process, hot embossing technology and thin film technology. The subsequent evaluation phase involves several test methods regarding electrical and mechanical characterization as well as MRI visibility aspects. The degree of fulfillment of the predefined requirements is determined within the analysis phase. Furthermore, an exemplary evaluation of four realized MRI markers was conducted, focusing on the performance within the MRI environment.

Pre-tuned resonant marker for iMRI using aerosol deposition on polymer catheters

New advances in MRI technology enable fast acquisition of high-resolution images. In combination with the new open architecture this scanners are entering the surgical suite being used as intra-operative imaging modality for minimally invasive interventions. However, for a usage on a large scale the major issue of availability of appropriate surgical tools is still unsolved. Such instruments, i.e. needles and catheters have to be MR-safe and -compatible but in contrast still have to be visible within the MRI image. This usually is solved by integration of markers onto non-magnetic devices. For reasons of MR-safety, work-flow and cost effectiveness semi-active markers without any connection to the outside are preferable. The challenge in development and integration of such resonant markers is to precisely meet the MRI frequency by keeping the geometrical dimensions of the interventional tool constant. This paper focuses on the reliable integration and easy fabrication of such resonant markers on the tip of an interventional instrument. Starting with a theoretical background for resonant labels a self-sufficient pre-tuned marker consisting of a standard capacitor and a thin-film inductor is presented. A prototype is built using aerosol deposition for the inductor on a 6-F polymer catheter and by integration of an off-the-shelf capacitor into the lumen of the catheter. Due to the fact that the dielectric materials of some capacitors lead to artifacts in the MRI image different capacitor technologies are investigated. The prototypes are scanned by an interventional MRI device proving the proper functionality of the tools.

A new device for characterization of mechanical stress caused by packaging processes

This paper reports on a new method for estimation and minimization of mechanical stress on MEMS sensor and actuator structures due to packaging processes based on flip chip technology. For studying mechanical stress a test chip with silicon diaphragms was fabricated. A network of piezo-resistive solid state resistors created by diffusion was used to measure the surface tension pattern between adjacent diaphragms. Finite element method simulation was used to calculate the stress profile and to determine the optimum positions for placing the resistive network.

A multilayer process for fine-pitch assemblies on molded interconnect devices (MIDs)

The miniaturization of overall systems plays a key role for the propagation of technological applications. To meet future requirements in size decreasing environments especially the packaging and mounting of silicon devices needs new impulses. 3D-MIDs (3-dimensional molded interconnect devices) exhibit a high potential for smart packages and assemblies. The integration of various functionalities (electrical connections, housing, thermal management, mechanical support) in one 3-dimensional shaped circuit carrier makes a further system shrinking possible. The compatibility between 3D-MIDs and high density fine-pitch semiconductor packages (like BGAs, MCMs, CSPs or even bare dies) is limited. Due to lack of a 3-dimensional multilayer technology the wiring of semiconductors with a high I/O count is critical. Therefore a new 3D-MID multilayer process is developed and combined with an established 3D-MID metallization process. The new multilayer process is investigated with respect to its electrical and mechanical behavior. A demonstrator was fabricated to perform desired tests.

A novel injection molded fluidic interposer for microfluidic applications

The implementation of fluidic functions in 3D-MID (three dimensional molded interconnect devices) allows to create a new field of applications and enhanced system solutions. We report about the capabilities of MID for the packaging of chip modules with microfluidic functions. A mechanically stable and leak tight fluidic connection is needed between the microfluidic chip and the environment. For this purpose a fluidic interposer is fabricated by the LDS-process (laser direct structuring) and includes a metallization for electrical signals and channel structures for fluidic features. The presented interposer enables the transformation of fluidic ports from the macro- to the micro scale. To characterize the device, a microfluidic test chip made of silicon and glass (Borofloat®) has been fabricated and mounted on the fluidic interposer by a flip-chip vapor phase process. Finally the potential of the system is shown by testing maximum pressurization and fluidic sealing.