Fabrication and Characterization of Flexible Thermoelectric Generators Using Micromachining and Electroplating Techniques

Development of a Rapid Tool for Metal Injection Molding Using Aluminum-Filled Epoxy Resins

Metal injection molding (MIM) is a near net-shape manufacturing process combining conventional plastic injection molding and powder metallurgy. Two kinds of injections molds for MIM were developed using conventional mold steel and aluminum (Al)-filled epoxy resins in this study. The characteristics of the mold made by rapid tooling technology (RTT) were evaluated and compared with that of the fabricated conventional machining method through the MIM process. It was found that the service life of the injection mold fabricated by Al-filled epoxy resin is about 1300 molding cycles with the average surface roughness of 158 nm. The mold service life of the injection mold fabricated by Al-filled epoxy resin is about 1.3% that of the conventional mold steel. The reduction in manufacturing cost of an injection mold made by Al-filled epoxy resin is about 30.4% compared with that of the fabricated conventional mold steel. The saving in manufacturing time of an injection mold made by RTT is about 30.3% compared with that of the fabricated conventional machining method.

Thermoelectric Energy Micro Harvesters with Temperature Sensors Manufactured Utilizing the CMOS-MEMS Technique

This study develops a TEMH (thermoelectric energy micro harvester) chip utilizing a commercial 0.18 μm CMOS (complementary metal oxide semiconductor) process. The chip contains a TEMH and temperature sensors. The TEMH is established using a series of 54 thermocouples. The use of the temperature sensors monitors the temperature of the thermocouples. One temperature sensor is set near the cold part of the thermocouples, and the other is set near the hot part of the thermocouples. The performance of the TEMH relies on the TD (temperature difference) at the CHP (cold and hot parts) of the thermocouples. The more the TD at the CHP of the thermocouples increases, the higher the output voltage and output power of the TEMH become. To obtain a higher TD, the cold part of the thermocouples is designed as a suspended structure and is combined with cooling sheets to increase heat dissipation. The cooling sheet is constructed of a stack of aluminum layers and is mounted above the cold part of the thermocouple. A finite element method software, ANSYS, is utilized to compute the temperature distribution of the TEMH. The TEMH requires a post-process to obtain the suspended thermocouple structure. The post-process utilizes an RIE (reactive ion etch) to etch the two sacrificial materials, which are silicon dioxide and silicon substrate. The results reveal that the structure of the thermocouples is completely suspended and does not show any injury. The measured results reveal that the output voltage of the TEMH is 32.5 mV when the TD between the CHP of the thermocouples is 4 K. The TEMH has a voltage factor of 8.93 mV/mm²K. When the TD between the CHP of the thermocouples is 4 K, the maximum output power of the TEMH is 4.67 nW. The TEMH has a power factor of 0.31 nW/mm²K².

Foundry Service of CMOS MEMS Processes and the Case Study of the Flow Sensor

The complementary metal-oxide-semiconductor (CMOS) process is the main stream to fabricate integrated circuits (ICs) in the semiconductor industry. Microelectromechanical systems (MEMS), when combined with CMOS electronics to form the CMOS MEMS process, have the merits of small features, low power consumption, on-chip circuitry, and high sensitivity to develop microsensors and micro actuators. Firstly, the authors review the educational CMOS MEMS foundry service provided by the Taiwan Semiconductor Research Institute (TSRI) allied with the United Microelectronics Corporation (UMC) and the Taiwan Semiconductor Manufacturing Company (TSMC). Taiwan’s foundry service of ICs is leading in the world. Secondly, the authors show the new flow sensor integrated with an instrumentation amplifier (IA) fabricated by the latest UMC 0.18 µm CMOS MEMS process as the case study. The new flow sensor adopted the self-heating resistive-thermal-detector (RTD) to sense the flow speed. This self-heating RTD half-bridge alone gives a normalized output sensitivity of 138 µV/V/(m/s)/mW only. After being integrated with an on-chip amplifier gain of 20 dB, the overall sensitivity of the flow sensor was measured and substantially improved to 1388 µV/V/(m/s)/mW for the flow speed range of 0–5 m/s. Finally, the advantages of the CMOS MEMS flow sensors are justified and discussed by the testing results.