微感測器之掉落衝擊試驗與可靠度評估

Drop Test Reliability Assessment of Micro Sensors

黃子恆(Tzu-Heng Huang)

指導教授 ： 葉孟考

國立清華大學/工學院/動力機械工程學系/碩士(2014年)

摘要

近年來隨著物聯網(Internet of Things)技術之發展，硬體設備以及電子資訊的串聯已為重要的關鍵技術。由於產品逐漸往追求多功能性的目標發展，為了建立人與人、人與物、物與物間的智慧互動式平台，微型化的智慧感測元件成為其中的關鍵技術。例如加速度計，憑藉著體積小、重量輕及低功率的特色，已廣泛應用在工程量測、車輛安全系統及數位遊戲產業中。由於電子元件大多具有高精度、高單價的特點，產業界為了對電子元件進行有效的可靠度評估，大多採用掉落衝擊試驗(Drop Test)的結果做為依據。本研究主要是以MEMS微感測器為研究對象，使用JEDEC規範進行掉落衝擊試驗，並使用有限元素分析軟體ANSYS，針對JESD22-B111規範下的掉落衝擊試驗進行模擬。採用加速度1500G和衝擊波時間0.5ms做為掉落條件，運用支承激振法(Support Excitation Method)來預測基板在掉落碰撞時整體的受力變化情形，並使用韋伯可靠度函數配合掉落衝擊試驗結果，進行更完整的可靠度評估。由於目前產業界並沒有特別針對MEMS微感測器制定相關的掉落試驗規範，因此本研究分析感測器之訊號變化，定義失效準則，以結合JEDEC規範進行掉落衝擊試驗。結果顯示本實驗所研究之加速度感測器屬於耗損型，從有限元素分析的結果，可得知在多次掉落衝擊後，由於MEMS結構與Die的彈簧銜接處反覆產生大應力，使得材料發生疲勞，導致加速度感測器訊號或靈敏度出現異常。本研究之成果可做為多功能人機互動平台開發上可靠度評估之參考。

關鍵字

掉落衝擊試驗 ； 可靠度

並列摘要

With the development of Internet of Things in recent years, the connection between device hardware and electronic information is becoming a critical technology. With the evolution of electronics industry, consumers demand for muti-functions in electronic components and products. In order to establish a logical interactive platform, application of micro sensor becomes a critical technology. For example, accelerometer is light and small, it has already been widely used in measurement, car and game industry. Electronic products have high precision and high price, most people use the drop test to evaluate their reliability. This study focused on MEMS micro accelerometer sensor, performed the drop test under JEDEC standards, and used the finite elements analysis software ANSYS○R to simulate the drop test under JESD22-B111 standard, using maximum acceleration 1500 G and impact time 0.5 ms as the impact conditions. By using the support excitation method, the stress distribution was calculated on the test board during drop impact, and the results were compared with Weibull reliability distribution. Since there is no existing standard for drop test of MEMS micro sensors, this study established a failure standard by analyzing the signal of sensors. The results showed that the failure rate of accelerometer sensor increased with time. After comparing the results with those from finite elements analysis, fatigue of accelerometer sensor occurred in springs of MEMS structures, and caused errors in output signal as well as the sensitivity of accelerometer. The results of this study can be used as the reference for developing the multi-functional logical interactive platform.

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