SIM卡電極接觸力線上檢測器之研發

Abstract

本文旨在研發一檢測器能夠線上檢測手機內部SIM卡與插槽觸腳的接觸力，以防止SIM卡接觸不良的問題。而由於SIM卡插槽內共有六到八個彈性簧片的觸腳，所以利用微製程來製作一個具有八個電容式荷重元的檢測器，荷重元本身為一組平行板電容，當受力之後會使得上下電極的間距改變，進而改變電容值，即可藉由量測電容值的變化以推算出負載的大小。 為了防止因受力過大導致受力面的矽基板損毀但又希望上電極的位移要夠大以獲得較大靈敏度，因此先利用有限元素法軟體ANSYS進行一系列模擬，以獲取較佳的受力結構，再將該結構的變位節點匯入ANSYS的靜電模型中計算電容，並調整各電極間距、尺寸以及幾何形狀，以達最佳的靈敏度與解析度。 荷重元電容值的讀取係採用高解析度電容數位轉換晶片AD7150，並搭配C#程式語言所編寫的視窗軟體，將AD7150內的暫存器資料讀取至電腦，經校正後繪製出各荷重元的校正曲線，還具備線上檢測受力情況以及繪製荷重歷時曲線等功能。 製作完成的感測器經過校正後，解析度可達0.45g/fF。

This thesis focus on the developing of a sensor to detect the contact forces between SIM card and SIM card contact pins in situ. This detector can help to prevent open circuit SIM card and SIM card contact pins. There are six to eight contact pins per SIM card slot which are made of flexible metal reed. The detector consists of eight load cells is fabricated with MEMS techniques. Each load cell is a parallel plate capacitor which capacitance is a function of the external force applied. Therefore the contact force can be obtained by measuring the capacitance, In order to prevent damage of silicon structure caused by external force and also to maintain larger deflection of the moving electrode, finite element analysis was conducted to find the optimal dimensions. Then the deflection of the upper plate was imported into ANSYS models to calculate capacitance. Then the electrode spacing and size can be adjusted to achieve optimal electrode geometry, capacitance variation and resolution. High resolution capacitance to digital converter AD7150 was adopted to read the capacitance value of load cells. The data in AD7150 registers were imported into computer via a C# program. Recorded data were used to calibrate load cells, detecting the external force and constructing the loading history. The resolution of detector developed can reach 0.45g/fF.