Sung-Pil Chang

A Study on Energy Harvester with Cantilever Structure Using PZT Piezoelectric Material

Nowadays, the increasing demands upon mobile devices such as wireless sensor networks and the recent advent of low power electrical devices such as MEMS make such renewable power sources attractive. A vibration-driven MEMS lead zirconate titanate (PZT) cantilever device is developed for energy harvesting application. This paper presents a piezoelectric based energy harvester which is suitable for power generating from conventional vibration and has in providing energy for low power electron ic devices. The PZT cantilever is used d33 mode to get the electrical power. The PZT cantilever based energy harvester with the dimension of 7 mm3 mm0.03 mm is fabricated using micromachining technologies. This PZT cantilever has the mechanical resonance frequency with a 900 Hz. With these conditions, we get experimentally the 37 uW output power from this device with the application of 1g acceleration using the 900 Hz vibration. From this study, we show the feasibility of one of energy harvesting candidates using PZT based structure. This PZT energy harvester could be used for various applications such a batteryless micro sensors and micro power generators.

Study on Low Temperature Bonding Technology for Optical PCB with Polymer Intermediate Layers

Abstract As the demands for the higher data transmission speed and capacity as well as integration density grow throughout the network, much works have being done in order to integrate the Electrical PCB with Optical PCB. However, one of the most troublesome problems in the commercial bonding process is to need the high temperature for the bonding. Due to the high temperature bonding process, lots of side problems are followed such as warpage and crack, etc. In t his paper, we tried to develop the new bonding technology with low temperature around 100℃. As a result of this study, the PCB bonding technology with high bonding strength is demonstrated with the value of bonding strength from 7 to 8 MPa at the temperature of 100 ℃.Key Words : Low temperature bonding, Electrical PCB, Optical PCB, Bonding strength 1. 서 론 1.지식 정보화 사회의 고도화에 따라 정보 전송량에 대한 수요가 급격하게 증가하고 있으며, 이에 따른 전송용량의 수요를 충족시키기 위한 수단으로 광도파로가 포함된 인쇄회로기판인 광 PCB가 대두되고 있다. 이제까지 광 PCB 모듈은 다수의 광소자와 IC 칩의 이차원적 배율에 의하여 이루어져 왔다. 그러나 최근 제품의 소형화, 경량화가 급격히 진행됨에 따라 반도체 칩을 2차원적으로 배열하여서는 원하는 크기와 성능을 얻는데 한계에 도달하게 되어 광 PCB를 3차원으로 적층하는 3D 패키지에 대한 연구가 진행되고 있다.광 PCB의 적층형 패키지는 크기 및 무게의 현저한 감소와 더불어 단위면적당 소자 기능의 증가 및 공정가격 저하 등의 여러 장점을 지니고 있다. 그러나 현재 상용되고 있는 적층형 전기 PCB는 1. 인하대학교 전자공학과 (인천시 남구 용현동 253)a. Corresponding Author : spchang@inha.ac.kr접수일자 : 2009. 11. 51차 심사 : 2009. 12. 7심사완료 : 2009. 12. 22라미네이션 공정을 이용한 200℃ 이상의 고온 공정을 주로 사용하고 있다. 이러한 고온 공정은 적은 변형에도 큰 성능 변화를 가져올 수 있는 광 PCB에는 적합한 공정이 아니다. 고온 공정이 진행된 후에 기판의 열팽창계수 차이로 인하여 광 PCB에는 비틀림이나 휨 현상이 발생할 수 있고, 심지어는 파괴까지도 일어날 수 있다. 그것은 작은 변형에도 성능 변화가 심한 광 PCB의 신뢰성에 큰 악영향을 끼칠 수 있는 요소이다. 그래서 최근 광 PCB와 전기 PCB 간의 적층형 PCB 접합에서는 저온 접합에 관한 연구가 활발히 진행되고 있다.본 논문에서는 높은 저항, 낮은 손실 기울기, 낮은 유전율 등의 특성을 지닌 포토레지스트를 이용하여 100℃ 이하의 저온 공정을 진행하여 그 기계적 특징을 비교하였다.

Demonstration of MEMS Inductor on the LTCC Substrate

Lots of integration work has been done in order to miniaturize the devices for communication. To do this work, one of key work is to get miniaturized inductor with high Q factor for RF circuitry. However, it is not easy to get high Q inductor with silicon based substrate in the range of GHz. Although silicon is well known for its good electrical and mechanical characteristics, silicon has many losses due to small resistivity and high permittivity in the range of high frequency. MEMS technology is a key technology to fabricate miniaturized devices and LTCC is one of good substrate materials in the range of high frequency due to its characteristics of high resistivity and low permittivity. Therefore, we proposed and studied to fabricate and analyze the inductor on the LTCC substrate with MEMS fabrication technology as the one of solutions to overcome this problem. We succeeded in fabricating and characterizing the high Q inductor on the LTCC substrate and then compared and analyzed the results of this inductor with that on a silicon and a glass substrate. The inductor on the LTCC substrate has larger Q factor value and inductance value than that on a silicon and a glass substrate. The values of Q factor with the LTCC substrate are 12 at 3 GHz, 33 at 6 GHz, 51 at 7 GHz and the values of inductance is 1.8, 1.5, 0.6 nH in the range of 5 GHz on the silicon, glass, and LTCC substrate, respectively.

Study on Micro Dried Bio-potential Electrodes Using Conductive Epoxy on Textile Fabrics

In this paper, micro dried bio-potential electrodes are demonstrated for sEMG (surface ElectroMyoGraphic) signal measurement using conductive epoxy on the textile fabric. Micro dried bio-potential electrodes on the textile fabric substrate have several advantages over the conventional wet/dry electrodes such as good feeling of wearing, possibility of extended-wearing due to the good ventilation. Also these electrodes on the textile fabric can easily apply to the curved skin surface. These electrodes are fabricated by the screen-printing process with the size of and the resultant resistance of these electrodes have the average value of . The conventional silver chloride electrode shows the average value of . However, the electrode on the textile fabric are able to measure the sEMG signal without feeling of difference and this electrode shows the lower resistance of than conventional silver chloride electrode with in the condition of the very sharp curve surface (the radius of curvature is 40 mm).

Fabrication of Nickel-based Piezoelectric Energy Harvester from Ambient Vibration with Micromachining Technology

Owing to the rapid growth of mobile and electronic equipment miniaturization technology, the supply of micro mobile computing machine has been fast raised. Accordingly they have performed many researches on energy harvesting technology to provide promising power supply equipment to substitute existing batteries. In this paper, in order to have low resonance frequency for piezoelectric energy harvester, we have tried to make it larger than before by adopting nickel that has much higher density than silicon. We have applied it for our energy harvesting actuator instead of the existing silicon based actuator. Through such new concept and approach, we have designed energy harvesting device and made it personally by making with micromachining process. The energy harvester structure has a cantilever type and has a dimension of for length, width and thickness respectively. Its electrode type is formed by using Au/Ti of interdigitate d33 mode. The pattern size and gap size is 50 . Based on the measurement of the nickel-based piezoelectric energy harvester, it is found to have 778 Hz for a resonant frequency with no proof mass. In that resonance frequency we could get a maximum output power of 76 at 4.8 being applied with 1 g acceleration.

Fabrication of the Micromachined Transformer using High Permeability NiFe Core

Recently as the electronic devices are getting to be more and more smaller, transformers are needed to be micro fabricated using MEMS technology. In this paper transformers have been fabricated and measured by depositing insulation layer to reduce the loss of eddy current and in the middle core a high permeability permalloy was designed based on the turns ratio between primary coil and secondary coil which are 1:1 transformers. (the number of turns of primary coil and secondary coil: 3/3, 5/5, 7/7). The size of the transformers including ground shield are , , respectively. The line width, pitch and the height of post are 50um. Based on the measured data from the micro fabricated transformers, the 3/3 turns in the primary coil and secondary coil showed the lowest insertion loss with 1.5 dB at 480 MHz and the 7/7 turns in the primary coil and secondary coil showed the highest insertion loss with 2.5 dB at 280 MHz. Also confirmed that the bandwidth goes up as the number of turns goes down. There was some difference between the actual measured data and the HFSS simulation result. It looks as if it is an error of the difference between oxidation of copper or the permeability of SU-8.

Demonstration of Alternative Fabrication Techniques for Robust MEMS Device

This work describes efforts in the fabrication and testing of robust microelectromechanical systems (MEMS). Robustness is typically achieved by investigating non-silicon substrates and materials for MEMS fabrication. Some of the traditional MEMS fabrication techniques are applicable to robust MEMS, while other techniques are drawn from other technology areas, such as electronic packaging. The fabrication technologies appropriate for robust MEMS are illustrated through laminated polymer membrane based pressure sensor arrays. Each array uses a stainless steel substrate, a laminated polymer film as a suspended movable plate, and a fixed, surface micromachined back electrode of electroplated nickel. Over an applied pressure range from 0 to 34 kPa, the net capacitance change was approximately 0.14 pF. An important attribute of this design is that only the steel substrate and the pressure sensor inlet is exposed to the flow; i.e., the sensor is self-packaged.