熱電模組特性分析與其可靠度壽命之機械性加速測試方法研究

Characteristic analyse and the mechanical accelerate life test on the reliability of thermoelectric modules

蕭富澤(Fu-Ze Siao)

指導教授 ： 陳永樹

元智大學/工程學院/機械工程學系/碩士(2012年)

https://doi.org/10.6838/YZU.2012.00351

摘要

熱電材料目前主要之應用有利用Seebeck效應之熱電產生器(Thermoelectric Generator, TEG)以及利用Peltier效應之熱電致冷器 (Thermoelectric Cooler, TEC)。其廣泛用於人造衛星之電力提供、車用冰箱冷卻、電子防潮箱除濕，…等。熱電模組運作時產生的溫度梯度，使元件間產生熱漲冷縮效應而變形，造成在介面處產生張應力與壓應力，在此應力反覆循環作用下，最終造成元件的材料熱疲勞(Thermal Fatigue)破壞而嚴重影響其使用壽命。國內外相關研究皆著重於材料改善以提升效率之設計為主，針對其使用壽命的研究則是相對稀少。
而一般電子產品有關溫度之可靠度測試，主要以溫度循環測試為主。然熱電材料運作時產生溫度梯度之特性，顯然不完全適用均溫之熱循環測試，且一般溫度循環測試時間動輒數千小時以上。即便實際對TE做連續之電源循環開、關 (Power Cycling) 測試，其失效往往費時半年以上，這冗長的測試時間並不符合產品的研發成本。
本研究首先就熱電元件的特性做探討，結合熱電偶與全域應變量測設備探討熱電模組在實際使用時，其溫度梯度與晶片翹曲變形之關聯性。接著對熱電元件進行非破壞性X-Ray檢測，觀察熱電元件內部焊錫是否產生缺陷，再者利用破壞性分析將熱電元件切割、鑲埋、研磨後，藉由光學顯微鏡觀察其失效模式。最終目的在於開發一套新的測試方法，利用機械彎曲測試配合所設計之特殊施力夾具，產生類似熱電模組實際使用之形變，快速施以循環應力，期以縮短元件測試時間，衍生出新的「機械測試」方法來取代傳統溫度循環測試。另外更改其加速壽命因子如加大位移與頻率，藉此得以估算出產品的壽命。有此有效之壽命評估方式，對熱電模組之可靠度改善設計有立即而顯著之效益。

關鍵字

熱電模組 ； 壽命 ； 熱變形 ； 疲勞失效 ； 熱循環 ； 彎曲測試

並列摘要

The applications of thermoelectric (TE) modules can be set into two categories. It is based on principles of the Seebeck effect for applications in thermoelectric generators, and on the Peltier effects in thermoelectric coolers use. It is widely used in power source of satellite, care refrigerator, and electronic dehumidifiers. While a TE module was working, it will generate temperature gradients on both sides of the device that often caused deformation and thus induced repetitive tensile and compressive stresses. This will cause thermal fatigue failure that affects its life dramatically. However, most of the research focused on developing new consisting materials in improving its efficiency. Whereas, the reliability study of TE modules were rarely seen in literatures.
Generally, reliability assurance for electronic devices used temperature cycling test (TCT). It can provide homogeneous heating and cooling on the device. But this test method seemed improper for TE modules that have temperature gradients. Also, the typical test period usually takes a thousand hours. Even with the consecutive power cycling (on-off) test on the TE module, it still takes about six months to get a failure data. This can’t fit the economic concern in the development of TE products
The study developed a new test method in reducing the test time for reliability study of TE modules. Firstly, it will use Digital Image Correlation(DIC) equipment to measure the deformation of TE modules in real applications. Then, it will design a special fixture on the mechanical bend test machine to exert forces on the TE modules so as to generate similar deformation as those measured in DIC. Meanwhile, with the finite element analysis to calculate the stresses both from the temperature effects and mechanical bend test were compared with each other. The crosshead speed and descending displacement of the cyclic bend test were also varied in simulating the repeated deformation resulted from the heating and cooling of TE. Different life accelerated factor were controlled by varying the amount of exerting forces. The life was estimated through these stress-cycle curves. It is believed that with this efficient reliability test method, it can provide immediate design improvements for TE modules’ reliability.

並列關鍵字

Thermal Cycling ； Thermal Deformation ； Thermal Electric Module ； Reliability ； Bend Test ； Fatigue Failure ； Life

參考文獻

[11] 林佑丞，”以有限元素法分析熱電特性對熱電致冷器冷卻性能之影響”，國立成功大學機械工程學系碩士論文，2011。

[6] G. D Giacomo, “Reliability of Electronic Packages and Semiconductor Devices ,” McGraw-Hill, New York, 1996.

[7] A. Dasgupta, “Failure Mechanism Models for Cyclic Fatigue,” IEEE Transactions on Reliability, Vol.42, No.4, pp.548–555, 1993.

[9] 林昆標，”熱電致冷器之三維暫態模擬分析”，國立成功大學機械工程學系碩士論文，2004。

[10] 吳亭瑩，”熱電致冷器熱變形之實驗與數值探討”，國立清華大學動力機械工程學系碩士論文，2010。