電子元件可靠度評估－以通訊用連接器為例

Reliability Assessment of Electronic Devices - A Case Study of Connectors Applied to Telecommunication

陳耀鍾(Yao-Chung Chen)

指導教授 ： 吳文方

國立臺灣大學/工學院/機械工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.02941

摘要

一般而言，產業界對於通訊用電子產品穩態期之失效率評估，常是以Telcordia SR-332可靠度預估模型來做估算，其基本假設是產品壽命分佈符合指數分佈且失效率為一定值。儘管此方式可快速預估產品的平均失效時間與失效率等相關可靠度指標，但在現實使用環境中，產品仍會受到眾多因素影響，導致模型評估的結果不一定符合該產品之特性。因此，本研究藉由失效模式及影響性分析與失效樹分析，釐清本研究對象－2-mm Hard Metric Connector（以下簡稱連接器）最關鍵之潛在失效因子，並針對分析結果擬定加速試驗與插拔試驗規劃，最後再透過試驗數據，依可靠度工程原理找出最符合產品特性之可靠度指標。研究結果顯示，此型連接器端子的活化能為0.26 eV，若以阿列尼厄斯(Arrhenius)模型分析連接器端子在40 ℃環境下之壽命，在幾種常見的機率密度函數中，對數常態機率密度函數為其最適分配，平均失效時間為69,734小時；若以艾林(Eyring)模型分析端子在40 ℃與40 ℃/30％ RH環境下之壽命，對數常態機率密度函數亦為其最適分配，其中在40 ℃的使用環境下，平均失效時間為74,634小時，而在40 ℃/30％ RH的使用環境下，其平均失效時間則為70,725小時。以上顯示此類電子產品的壽命分配並非恆為指數分佈、且失效率並非恆為定值。同樣的試驗數據若依Telcordia SR-332可靠度預估模型計算，其失效率為1.79 FITs (Failures Per Billion Device Hours)，換算平均失效時間為558,659,218小時，相較於前述分析結果存有極大之差異，所以在解讀Telcordia模型的分析結果時，務必要格外謹慎、小心。本研究插拔試驗之分析結果則同樣顯示對數常態機率密度函數為插拔壽命之最適分配，平均失效次數為41,771次。綜合以上分析結果可知，此型連接器對於外在環境與反覆插拔均具相當的可靠度。

關鍵字

Telcordia SR-332 ； 失效模式及影響性分析 ； 連接器 ； 加速試驗 ； 插拔試驗 ； 活化能

並列摘要

The steady-state failure rates of electronic products applied to telecommunication are frequently estimated based on Telcordia SR-332 Reliability Prediction Model. Its basic assumptions are that product lives follow the exponential distribution and failure rates are constants. Although this approach provides us an easy way to estimate the failure rate, mean time to failure (MTTF) and other quantities related to product reliability, it may not be able to reflect complicated environmental conditions a product may be subjected to. In practical applications, products are affected by many environmental factors causing reliabilities predicted by the model inconsistent with characteristics of the products. Therefore, in the present study, Failure Mode and Effect Analysis (FMEA) and Fault Tree Analysis (FTA) are used to identify the most relevant failure modes of a particular electronic product - a two-mm hard metric connector. Based on results from FMEA and FTA, a series of accelerated test and durability test are designed and performed for the studied connectors. Detailed reliability analyses are carried out. The result shows that the activation energy is 0.26 eV for pins of this type of connector. Among the fitted probability distribution functions, the pin life follows the lognormal distribution the best, and its MTTF is 69,734 hours under the condition of 40 ℃ if Arrhenius model is adopted. If Eyring model is considered instead, the lognormal distribution is also the best fit to the tested data. Its MTTFs are 74,634 hours under the condition of 40 ℃, and 70,725 hours under the condition of 40 ℃/30％ RH, respectively. The above results show that the pin life does not follow the exponential distribution and the failure rate is not a constant as reflected by Telcordia model. If Telcordia SR-332 Reliability Prediction Model is applied, the failure rate is found to be 1.79 FITs (Failures per Billion Device Hours), which has a MTTF of 558,659,218 hours. As for the plug-in-and-out durability test, the result from analyzing the test data indicates the pin life may be fitted by a lognormal distribution, and its MTTF is 41,771 cycles. In summary, with its rather strong pins, the tested and analyzed type of connector is quite reliable.

並列關鍵字

Telcordia SR-332 ； Failure Mode and Effect Analysis (FMEA) ； connector ； accelerated test ； durability test ； activation energy

參考文獻

20. 闕延洲，自行車內變速系統之可靠度研究，國立台灣大學機械工程研究所碩士論文，民國93年。

4. Smith, C. L. and Womack, J. B., “Raytheon Assessment of PRISM as a Field Failure Prediction Tool,” Reliability and Maintainability Symposium, pp. 37-42, 2004.

5. Bennett, J., “Telcordia Reliability Prediction Procedure - Upper Confidence Levels,” Reliability and Maintainability Symposium, pp. 452-455, 2008.

6. Ebeling, C. E., “An Introduction to Reliability and Maintainability Engineering,” McGraw-Hill, 1997.

7. Caruso, H. and Dasgupta, A., “A Fundamental Overview of Accelerated-Testing Analytical Models,” Reliability and Maintainability Symposium, pp. 389-393, 1998.