Soeren Hirsch

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.

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...

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.

Towards a SAW based phononic crystal sensor platform

A Surface Acoustic Wave (SAW) sensor platform based on phononic crystals specifically designed for chemical and biosensing will be introduced. The unique feature of this sensor concept is the possibility to determine volumetric properties of analytes at volume as low as 1 nl. The sensor platform has the capability paving the way to study chemical reactions in microreactors or biomaterials directly in their physiological environment without any label.

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.

Micro fluidic biosensor array for parallelized cell adhesion analysis during pathogenic infection

In this contribution we present a novel disposable micro fluidic biosensor array for parallelized monitoring of cell adhesion during pathogenic infection. The biosensor array consists of 4 bioreactor chips and a flow distribution network. Thus, 4 biological experiments, can be run in parallel. Each bioreactor chip contains 4 quartz crystal resonators (QCRs) with randomly spread cells on top which are stimulated identically. Insofar, the array enables the analysis of the cellular response dependent on cell distribution. Injection molding technology was applied for the fabrication of low cost and disposable micro fluidic devices. Sensor signals are monitored with a miniaturized impedance analyzer combined with a novel sensor interface electronics for 16 QCRs. Light microscope pictures can be acquired in parallel. The array was used for the analysis of Madin-Darby canine kidney cells (MDCK-II). Results show significant variations in sensor signals, respectively cellular response, that can be attributed to different cell distributions on the sensor surface.

Application of a method for characterization of thermo mechanical stress caused by packaging processes

This paper reports on a method for the investigation of mechanical stress on MEMS sensor and actuator structures due to packaging processes. A silicon test chip is developed and manufactured to validate the simulation results. Finite element analysis (FEA) is used to optimize the geometric parameters and to find a stress sensitive sensor geometry. A diaphragm structure is used as mechanical amplifier for bulk induced stresses during the packaging process. Piezo resistive solid state resistors are doped into the surface of the chip to measure the stress in the diaphragms and at the contact pads being most significant locations for analysis. A high precision ohmmeter was used to measure the resistance prior and past the packaging process. The captured data allows for computation of the resulting stress loads in magnitude. Therefore, a stress evaluation of different packaging technologies is conducted and the impact of the packaging process on reliability can be estimated immediately.

Aerosol deposition of catalytic ink to fabricate fine pitch metallizations for moulded interconnect devices (MID)

The permanent miniaturization of automotive, medical and consumer products requires alternative packaging solutions. So far most electronic products are circuit boards mounted in a separate body. An upcoming alternative are moulded interconnect devices (3D-MID). They combine the substrate function for interconnects and the housing function. To ensure a high integration density it is necessary to apply fine pitch metallizations to the polymer devices.