Improving the Electrical Contact Performance for Amorphous Wire Magnetic Sensor by Employing MEMS Process.

Yulong Chen,Jianwen Chen,Lixin Xu,Jianhua Li

doi:10.3390/mi9060299

Yulong Chen, Jianwen Chen + Show 2 more

Open Access

https://doi.org/10.3390/mi9060299

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Journal: Micromachines	Publication Date: Jun 14, 2018
Citations: 7	License type: CC BY 4.0

Affiliation: Beijing Institute of Technology

Abstract

This paper presents a novel fabrication method for amorphous alloy wire giant magneto-impedance (GMI) magnetic sensor based on micro electro mechanical systems (MEMS) technology. In this process, negative SU-8 thick photoresist was proposed as the solder mask due to its excellent properties, such as good stability, mechanical properties, etc. The low melting temperature solder paste was used for the electrical connections with the amorphous alloy wire and the electrode pads. Compared with the conventional welding fabrication methods, the proposed micro electro mechanical systems (MEMS) process in this paper showed the advantages of good impedance consistency, and can be fabricated at a low temperature of 150 °C. The amorphous alloy wire magnetic sensor made by the conventional method and by the micro electro mechanical systems (MEMS) process were tested and compared, respectively. The minimum resistance value of the magnetic sensor made by the conventional welding method is 19.8 Ω and the maximum is 28.1 Ω. The variance of the resistance is 7.559 Ω2. The minimum resistance value of the magnetic sensor made by micro electro mechanical systems (MEMS) process is 20.1 Ω and the maximum is 20.5 Ω. The variance of the resistance is 0.029 Ω2. The test results show that the impedance consistency by micro electro mechanical systems (MEMS) process is better than that of the conventional method. The sensor sensitivity is around 150 mV/Oe and the nonlinearity is less than 0.92% F.S.

Highlights

Amorphous alloy wire has a huge and sensitive response to the small direct current (DC) magnetic field at room temperature
Compared with the existing magnetic sensors based on Giant Magneto Resistance (GMR), Hall effect, fluxgate and superconducting quantum interference [3], amorphous alloy material show advantages of high resolution, low power consumption and fast response speed [4]
Honkura in Aichi steel company of Japan implemented the electrical connection of the amorphous alloy wire and ceramic electrodes by adoption of ultrasonic welding method [5]

Summary

Introduction

Amorphous alloy wire has a huge and sensitive response to the small direct current (DC) magnetic field at room temperature. In amorphous alloy wire giant magneto-impedance (GMI) magnetic sensor fabrication, many works have been carried out. Liu et al connected the microwire with 24 mm long and electroplated two-terminal length of 4 mm on printed circuit board (PCB) using lead-free solder, which is composed of tin (Sn: 96.5%), silver (Ag: 3.0%), and copper (Cu: 0.5%) in wt % [8]. In an earlier study by our team, we formed the micro pick-up coil of the amorphous wire giant magneto-impedance (GMI) magnetic sensor by micro electro mechanical systems (MEMS) technology [14]. Micro electro mechanical systems (MEMS) process was employed to fabricate amorphous alloy wire based giant magneto-impedance (GMI) magnetic sensor. SU-8 negative photoresist was used as the solder mask and low temperature solder paste (Sn42/Bi58) was used to connect the amorphous alloy wire and the electrode pads

Device Design

Findings

Conclusions