Tenghsien Lai

Design and fabrication of acoustic wave actuated microgenerator for portable electronic devices

An acoustic wave actuated microgenerator for power system applications in mobile phone was design, fabricated, and characterized. We used the acoustic wave of human voices or speakerphone by way of an electromagnetic transducer to produce electrical power for charging or to run a portable electronic device. The proposed microgenerator is composed of a planar coil, a suspension plate with supporting beams and a permanent magnet. In this paper, the dynamic response of the suspension structure and the variation of the induced magnetic flux were characterized by using commercial finite element analysis and Ansoft Maxwell EM3D software, respectively. The electroplating nickel and silicon bulk micromachining techniques were used to fabricate the suspension plate and planar coil, and by integrating a permanent magnet as well as wafer to wafer adhesion bonding to accomplish the microgenerator assembly. The experimental results shown the typical microgenerator with a planar dimension of 3 mm times 3 mm, the maximum induce-voltage 0.24 mV was generated at the driving frequency of 470 Hz. The dynamic response of microgenerator can be designed to meet a specific acoustic driving frequency to increase the efficiency of energy harvesting.

MEMS technology on wafer-lever LED packaging

This study demonstrated a newly type technology of a wafer level packaging method for light emitting diode (LED) with aspheric lens and microlens array using microelectromechanical systems (MEMS) technology and transfer molding process. The novel packaging structure includes two components: the silicon-based packaging substrate which is formed with arrayed reflector depression and through-hole interconnects by bulk micromachining and the optical encapsulation with lens configuration that formed by transfer molding in wafer level. By this pattern transfer process, the precise alignment between lens configuration and the reflector of silicon substrate can be achieved and batch process can be realized to reduce the costs. Beside, the packaging element can be used more applications. In the study, the pattern transfer of various lens profiles was also accomplished successfully by using silicone gel as lens mold. The brightness of the packaging elements with single aspheric lens profile and high fill factor microlens array can be increased by 26% and 16%, respectively, in comparison to the case of optical encapsulation with smooth curved surface. Furthermore, the light radiation uniformity was improved effectively through 100% fill factor microlens array. Therefore, the structure can satisfy the requirements of wafer level LED packaging and improve the heat dissipation and light extraction efficiency.

Characterization of the bending creep behavior for electroplating nickel microbeam

This study aims to investigate the creep behavior of electroplating nickel film using bending micromachined cantilever approach. The bending test including quasi-static, reloading, and time-dependent creep were performed by using a nano-indentation loading system. The resulting Youngs modulus and yielding strength were determined through mechanical testing, and the experimental average values are 191 GPa and 0.79 GPa, respectively. In addition, by measuring the load-deflection of micro cantilever under various stress levels with a constant temperature, the bending creep behavior of electroplating nickel film was determined and characterized. Experimental results show that when the bending stress is smaller than the measured yielding strength, the relation between the stress and strain rates is expressed as: (d/spl epsiv//dt) =0.00661n(/spl sigma/) +0.0104. These test results can provide the basis for the design optimization of nickel microstructure. Thus the performance and reliability of the MEMS devices can be predicted and improved.

Novel direct-view LED backlight unit with an aspheric microlens array and a rough-texture sheet

Abstract— This study proposes a novel direct-view light-emitting-diode (LED) backlight unit with a high-fill-factor aspheric microlens array and a rough-texture sheet. An aspheric microlens array and a rough-texture sheet made from polysiloxine were used as the grating element and optical diffuser, respectively, which increases light-extraction efficiency and improves luminance uniformity. The specific aspheric microlens-array mold was fabricated by using a heating encapsulated air process based on a glass wafer. This microlens array has the features of high fill factor and square-foot boundary with a continuous surface-relief profile. This unique out-of-plane surface profile creates a square light pattern with uniform luminance, and thus composes a uniform large-sized light pattern exactly in accordance with the layout of the LED array. The rough-texture sheet, which can scatter light uniformly, was formed by fine-grit-sandpaper molding. Experimental results show that by using an aspheric microlens array and rough-texture sheet reported here as the backlight diffusing components is highly effective in improving light uniformity at a wide viewing angle. An increase in illuminance by more than 10% was achieved in comparison with commercial backlight modules. Low cost in fabricating the aspheric microlens array and rough-texture sheet is anticipated due to the simplicity of the process.

A claw type of MEMS probe card for the electrical testing of micro-solder ball

This paper presents a micromachined claw probe with electroplating nickel for micro-solder ball electrical testing applications. The suspension claw structure consists of two bridges and four curved cantilevers, which have a flexible spring constant in a small region. The typical bending cantilever structure, made by nickel electroplating, had a thickness of 6.5μm, a width of 10μm and a length of 80μm. The maximum out-of-plane deflections of the fabricated 40×40 claw-probe array were approximately 50μm, under the effect of residual tensile stress. For the probing test of the micro-solder ball with diameter 200μm, the contact resistance was about 20Ω when the contact force was 6.7mN.

A novel electromagnetic microactuator with lateral magnetio-static force for scanning micromirror device

A novel electromagnetic microactuator with lateral magneto-static force was developed in this study for scanning micromirror device. The actuation performances in different vacuum degrees were also examined for verification. The present device assembled a tiny permanent magnet on a supporting beam to couple with a fixed solenoid coil for driving a micromirror plate in vibration. In an ambient environment, the corresponding scanning angle to the fast axis is 11.2 degrees at the first resonate frequency 4434 Hz. The maximum scanning angle for the case of fast scanning at the vacuum degree of 76 mTorr is increased by 31% compared with that of 760 Torr. The thermal effect induced by the coil is minimized to scanning quality, even at high vacuum environments. Thus, based on the results of this study, high reliability with high vacuum packaging can be expected.

High density out-of-plane microprobe array

In this paper, the high density out-of-plane microprobe array is demonstrated. The fabrication processes of proposed device including bulk micromachining, thin film deposition and electroplating. By depositing the various thickness of thin film with residual tensile stress, the deflection of bending beam could be precisely controlled. The horizontal variation of bending beam array could also restrict in a few micrometer. The concept for the device fabrication is depositing the Ti thin film on a suspension SiO2 cantilever to bring out-of-plane bending deformation, and then use electroplating process such as low stress Ni film to increase the stiffness of the probe structure without change the beampsilas bending profile. Through the different electroplating bath, the bending microprobe with different material, such as Ni and Cu, could be fabricated for IC testing and interconnection applications. According to the mask design, the high density probe array could easily achieve. The prototypes of the 40 times 40 microprobe array in pitch sizes of 50 mum, 80 mum and 100 mum were fabricated and characterized. Measurement result by the optical interferometer shown the mean bending height of twenty samples are about 3 mum, 9 mum and 26 mum in different beam length 25 mum, 55 mum and 85 mum, besides the maximum horizontal variations are less than plusmn0.8 mum, plusmn1.2 mum, plusmn2 mum that corresponded to the pitch size of 50 mum, 80 mum, and 100 mum, respectively.

Design and fabrication of Electroplating Nickel Micromachined Probe with out-of-plane predeformation

This paper present a new type of electroplating Nickel micromachined probes with out-of-plane predeformation for the next generation integrated circuit (IC) chip testing probe card application. It was fabricated using silicon bulk etching, Ti deposition and Ni electroplating process. We use the residual stress effect of thin films deposition to cause the flexible micromachined probe with a large out-of-plane predeformation and combine postelectroplating technique to further increase beams thickness and therefore enhance its stiffness. The typical micromachined probe had a thickness 5~10 µm, a width of 20 µm, and a length of 100 µm. The maximum deflection of the fabricated Nickel probe beam was 28 µm. This micromachined probe is capable of providing a very larger number of testing probe card, including the array pad format, and this designed also to satisfy the requirements for high frequency, high resolution and low cost wafer-level testing...