Components: Fabrication and Assembly Technologies

A New Approach to Qualitiy Assurance in Resistance Welding for Microsensors Packaging

Abstract

The permanent development of microelectronics technologies provide new challenges for miniaturization and complexity increasing for new packaging technologies. So the exciting applications for microsystems, sensors and actuators production are looking for the best quality hermetic sealing of metal packages. The paper showed our researches and experiments results for a new approach to quality assurance in resistance welding. These will analyze the main causes of weld failures and also our methods of determining its value. On the basis of this requirement have monitored through the weld sequence, integrated concept of power monitor. The technical features developed a modern concept applicable to a wider range of fields. Our monitor could be used to wide range of welding technologies like distributed spot and focused spot, projection, roller spot and mash welding machines, working with single or three phase, ac. or dc. The experiments with our equipment have proven its advantage for fast production assembly line.

Keywords: microwelding, microsensors and microsystems, quality assurance, monitoring systems

Design of a Micro Injection Moulding Machine for Thermosetting Moulding Materials

Abstract

Micro products made of thermosetting polymers enable innovative applications since thermoplastics do not always yield the desired properties: thermosetting moulding grades offer advantages in thermal durability and chemical resistance in comparison to thermoplastic resins. Processing smallest quantities of polymeric material for applications in micro system technology require high process accuracies, e.g. in the volume of plasticised material and injection dynamics. Alternative machine concepts especially designed for micro injection moulding meet these requirements by means of special constructive setups mostly by using a plunger for injection. An appropriate micro injection moulding machine prototype is available at IKV Aachen. A new design of the plasticising and injection unit specially designed for thermosetting moulding materials is presented in this paper.>/p>

Keywords: micro injection moulding machine, plasticising, thermosetting materials, machine concept

Laser Transmission Welding of Transparent Plastics Parts in Micro Technology

Abstract

Most welding processes for plastics do not meet the special demands of micro technology. Laser transmission welding, however, features distinctive advantages like low mechanical and thermal load of the joining parts. Hence it is particularly suitable for the welding of micro plastics parts. Certain optical properties of the components to be welded are needed though. While one of the welding parts has to exhibit a high transmittance in the range of the laser wavelength the absorptance of the other one has to be high enough to ensure a sufficient absorption of the laser radiation to plasticise the material. Here, carbon black has almost exclusively gained industrial importance, since it is an inexpensive material with good absorbing properties. However, it leads to a black coloration which is not always acceptable. Recently, there are special pigmentations which allow for a non black colour in the visible range of light, but nevertheless absorb laser radiation. Up to know, only few is known about their welding characteristics, so that it has to be investigated whether they are suitable for the application in micro technology.

Keywords: laser transmission welding, pigments, weld seam width, weld seam morphology

Different Influences on the ECF Process

Abstract

Electrochemical milling with ultra short voltage pulses (ECF) is an innovative technique to machine electrochemically active materials at micrometer feature size, especially very hard materials like steel. The movement of the tool is similar to conventional milling, although it does not rotate. Therefore 3D-forming of the workpiece is possible. The surface of the workpiece is etched by a galvanic current. Due to this neither mechanical forces nor thermal loads are applied to workpiece or tool. The ability to manufacture hard materials like stainless steel at micrometer feature size makes ECF the ideal technique for processing micro moulds. When manufacturing moulds large differences in machining speed and quality of the surface occur. So far possible explanations for this were supposed differences between the machinability of grain boundaries and interior of the grains. But experiments showed no significant influence. Furthermore the dependence of the tool diameter on the working distance was determined. Experiments showed a decreasing working distance with increasing tool diameter. This phenomenon could also be explained theoretically. Finally the influence of the grade of hardness on the ECF process is investigated at the tool steel M 340.

Keywords: ECF, working distance, grade of hardness, grain boundary

Multi-Component Micro Injection Moulding – Trends and Developments

Abstract

With standard micro injection molding becoming more and more established in practical manufacturing, special variants are attracting increasing attention. Especially the approaches on multi-component micro injection moulding have to be mentioned: As handling and assembly are difficult procedures especially in micro technology, methods to reduce mounting efforts are of high economic importance. By merging of shaping and mounting procedures in one step economic progress as well as new material combinations can be obtained. An interesting approach for the fabrication of metal (or, in principal, ceramic) micro components is the combination of insert injection molding and metal deposition by electroforming. First, an electrically conductive base plate is produced by injection moulding of conductively filled polymers. In a second injection moulding step microstructures consisting of insulating plastics are mounted on these plates. The quasi-infinite conductivity gradient allows controlled electroplating starting at the base plate only, so that defect-free metal micro components can be achieved. As a further variant of micro injection moulding, the development of the so-called MicroPIM process facilitates a large-scale series fabrication technology for metal and ceramic micro components. Combined with multi-component technology, an interesting new approach for micro manufacturing is obtained, i.e. the realization of magnetic/nonmagnetic or conductive/non-conductive material combinations by two-component MicroPIM.

Keywords: micro injection moulding, two-component injection moulding, powder injection moulding, electroplating, galvanoforming

Fabrication of Highly Precise Fiber Optical Array Products by use of Laser Based Micro Alignment

Abstract

The proceeding integration and miniaturization of mechanical and optical functions in systems for optical communication, for sensor and environmental technologies or for life sciences require an improvement and a customization of the manufacturing technologies. For fiber optical systems and components, especially for singlemode applications, adequate methods for a precise adjustment are necessary which allow a fast and cost-efficient alignment of fibers and other optical components like microlenses or laserdiodes. The demands on the adjustment process rise additionally for array applications. Laser based micro alignment is a promising technology for such critical adjustment tasks. We investigated the use of this technology for the alignment of fibers within fiber arrays. They are used for the assembly of fiber collimator arrays. We developed and analysed suitable actuator geometries for this application. In this paper we show some important results of the FEM based analyses to demonstrate the influence of the laser irradiation regime. First experimental results confirm the actuator behaviour calculated in the FEM analysis. Based on the simulations and experimental results, we are developing a compact alignment module which is adapted to the demands on the assembly process of fiber optical components. This alignment tool is one module within a complete miniaturised, scaleable and modular assembly line for the production of fiber collimator arrays.

Keywords: laser based micro alignment, fiber collimator array, assembly platform

Application of EDM to the Production of Micro Tooling

Abstract

The mass production of micro and meso scale products made of polymers or metals is intimately related to the production of high quality microtooling in stable materials capable to provide an accurate and repetitive performance throughout the whole demanded production. As it is widely known, the WEDM process provides high accuracy but is conceptually limited to the production of ruled features. The SEDM process can be a complement to this aspect but the electrodes must be manufactured by other technologies like WEDM, micromilling, turning, etc. Given the importance of several parameters like dimensional accuracy, tooling material for the different replication processes or tooling production technology, the present paper introduces some tests performed by the 4M Metals Workgroup. The analysis of some components manufactured by members of the group is presented discussing the influence of the EDM process on the machined tooling components and the consequent influence on the replication process.

Keywords: tooling, micro-punching, micro-EDM

Rapid Prototyping of 3D Micro- Nanostructures to Explore Cell Behaviour

A Novel Approach for Batch Production of Micro Holes by Micro EDM

Abstract

The paper proposed a novel approach of effective production of mass micro holes. A set of micro w-EDM mechanism is designed and mounted on the developed tabletop precision machine tool. The tension of micro wire is precisely controlled by magnetic force. In addition, the micro vibrations of the wire during discharging are effectively suppressed by the developed vibration suppression system. In order to fabricate the mass micro holes, the microstructure array of the high aspect ratio 10×10 micro squared electrodes with the width and the height of 21μm and 700μm, respectively for each electrode, and the spacing between two electrodes of 24μm is fabricated first by the proposed “reverse w-EDM” machining strategy. This micro electrodes array is employed directly to machine the mass micro holes on the same machine via the modified micro EDM peck drilling. By sequentially positioning the micro electrodes array after one drilling through process, the 900 same size micro through-holes array is successfully obtained on the stainless steel board of 0.1mm thickness. The results show satisfactory hole geometry, dimensional accuracy and surface roughness. More, it is verified that the mass micro holes can be fabricated efficiently by the proposed approach.

Keywords: batch production, mass micro holes, micro EDM

Investigations in Injection Moulding of Micro Structures and Microstructured Surfaces

Abstract

Telecommunication, information and medical industries have a high growth potential. A key technology for those industries is the replication of micro-structures. Precise micro-structured parts with functional surfaces can be produced economically by injection moulding. The whole process chain (thermal mould condition, moulding, demoulding, measurement and analysis) must be analysed carefully to ensure the highest precision and reliability. To enable the precise production of the above mentioned structures fundamental studies were conducted at the IKV. The studies considered on the one side several polymers (PMMA, PC, POM ) and on the other side various test structures. In addition an external inductive heating unit was analyzed and implemented into the process to heat the cavity surface efficiently. Using this technique new mould concepts could be developed with a dynamic inductive heating system to increase the moulding accuracy and reduce the formation of orientations in the moulded part drastically. The final step of the process chain comprises the measurement and analysis of the micro-structured moulded parts. To analyse the microscopic deviation between mould cavity and the surface of the moulded part, a special softwareprototype was developed. This software calculates the so called “differential surfaces” to show the influence of shrinkage and warpage on the micro structures and the macroscopic part geometry.

Keywords: Injection Moulding, microstructures, dynamic heating

Simulation of Micropart Motion under 2D Force Fields Implemented on a Cilia Microactuator Array

Abstract

Micromanipulation is a hot topic in the manufacturing of MEMS products. Alternatives to established manipulation techniques that have been proposed in the recent years include manipulation with force fields and microcilia actuator arrays. In this paper, a simulator for the positioning and alignment of microparts on a microcilia array under two dimensional force fields is presented. A description of its design and motion dynamics is given and the simulation results are presented and discussed.

Keywords: MEMS, 2D manipulation, simulation, force fields, cilia microactuator array

New Methods for Selective Metallization of 3-D Polymer Microparts

Abstract

The development of microdevices would be well served by integration of electronic connects into 3-D packaging. A number of technologies have been proposed in which conductive paths are created on polymer structures, e.g. by local activation of organometallic components present in plastic. But these suffer either from limited 3-D freedom, yield problems in mass production or excessive use of chemicals. Here two new and patented methods, selective etching and selective masking, for selective metallization for the production of three dimensional integrated devices are presented, which do not use precatalyzed polymers. After initial tests, a two-shot moulded three-dimensional test object with solder patches, through holes and varying track widths was used to test their selectivity and reproducibility for selected polymer combinations. The selective etching method gave for the PA4,6-PET combination excellent results with regard to the selective plating and subsequent reflow soldering. The second method, selective masking could be applied to a LCP-PPS combination, however process stability needs to be improved.

Keywords: metallization, integrated electronics, two-shot moulding

High Precision Placement of Solar Cell Assemblies on Large Base Plates for Concentrator Photovoltaics

Abstract

Photovoltaic concentrator applications use an optical system to concentrate sunlight on solar cells. A high concentration factor is necessary in order to reduce the size of the solar cells and hence to lower the costs for concentrator systems. The precise handling of the small solar cells calls for a high precision micro assembly process for base plate manufacturing. In this paper, the accuracies of the equipment and the processes used for high precision assembly of module base plates are analyzed. The sensitivity of the concentrator module to lateral dislocations of the cells is investigated in order to quantify the accuracy needed for the assembly process. The manufacturing equipment was characterized with respect to repeatability and to absolute accuracy. A repeatability of ± 6 μm for the X-axis and ± 15 μm for the Y-axis has been determined. The process accuracy is better than ± 60 μm, depending strongly on the measurement methods used for calculating the position errors.

Keywords:

An Investigation on Development of MEMS in LTCC by Embossing Technique

Abstract

The latest results achieved during the investigation of possibilities for producing MEMS in unfired green Low Temperature Cofired Ceramic (LTCC) by embossing technique are presented in this paper. Ceramic tapes in unfired state are subjected to compression by means of using tools specially designed and developed for this purpose. Structures obtained in this way demonstrate high repeatability and surface quality comparable with those gained by other techniques. In comparison with traditionally used laser cutting or injection moulding for ceramic processing, this technique offers better resolution and further miniaturisation, improved rigidity of small structures and possibility to profile the vertical walls in U- and V-shapes. The main focus of this paper will be on the optimisation of embossing parameters (embossing force, embossing time and temperature) in order to get repeatable and reliable results. Structures produced in this way could be successfully used in optical as well as in medical applications.

Keywords: LTCC, embossing, MEMS mass production, 3D packaging.

Layer Manufacturing as a Generic Tool for Microsystem Integration

Abstract

Nearly every microsystem application requires specific packaging solutions. In this paper we suggest a new approach to use layer manufacturing as a generic tool for microsystem integration. Three different methods to produce 3D electrical interconnects are presented. Ink jet printing is used for the ceramic layer manufacturing process, as well as for the printing of silver for circuit patterns. The technique is demonstrated for an Inertial Measurement Unit(IMU) platform. A four-sided pyramid was manufactured with layer manufacturing in ceramics and four gyroscopes were mounted on the sides of the pyramid. A demonstrator with three light diodes was also manufactured to demonstrate the possibility to produce 3D electrical interconnects in the volume of the pyramid.

Keywords: Layer Manufacturing, Microsystem 3D Electrical Interconnect, Micros system packaging

Bimaterial Actuators and Sensor with Built-in Compensation of the Ambient Temperature Interference

Abstract

We present a novel simple and efficient method for the full removal of the influence of ambient temperature variations to the operation of bimaterial-based MEMS actuators and sensors. The removal of the undesired interference is achieved through the very structure of the bimaterial cantilever, by reversing the order of bimaterial constituent materials at a certain length. Thus an extremely simple geometry is obtained for full self-compensation of the structures. We performed the full simulation of our devices by the finite element method. The structures require standard surface micromachining and utilize only Si-technology compatible materials like polyimides or SU-8. A simple rule for the determination of the zero-deflection condition is presented. The described compensation method enables a significantly reduced bimaterial device area and a much higher packaging density in element arrays, as well as an improved signal-to-noise ratio. The method is especially convenient for photodetector arrays for direct conversion of infrared radiation spatial distribution into a visible image.

Keywords: MEMS, temperature sensor, thermal actuator, bimaterial cantilever