剪力與彎曲測試用於替代覆晶球柵陣列構裝元件溫度循環可靠度測試之適用性研究

A Suitability Study for the Shear and Bend Tests as substitutions for Thermal Cycling Reliability Test of Flip Chip Ball Grid Array Components

范振澤(Chen-Tse Fan)

指導教授 ： 陳永樹

元智大學/工程學院/機械工程學系/碩士(2008年)

摘要

電子封裝可靠度測試領域中，最為重要且廣泛使用之測試為加速熱循環測試。但此測試方式通常需歷經一千小時，過於耗時而造成測試之瓶頸。因此，需時甚短之相關機械性彎曲、剪力測試則是常用之替代方案。但是，熱循環測試時電子元件上之受力狀況到底與這些機械應力測試何者較相似？顯然是考量替代方案時必須探究的。本研究從基本力學分析與失效機制及有限元素分析，探討何者才是最佳之熱循環替代測試方式，以準確掌握機械性可靠度測試之合理性。
　　本研究首先對於封裝結構，以簡化之三層樑理論計算受熱時之剪應力與正向應力，配合原有構裝元件之有限元素分析模型，分別進行彎曲測試、剪力測試與熱循環測試之模擬分析。比對彼此間對元件所產生應力分佈狀態之差異。藉此驗證所建立之熱應力數學模型之正確性，並據以判定何者為最適切之熱循環測試替代者。而實驗測試方面，則針對不同材料之覆晶構裝元件，包括有鉛銲錫之63Sn37Pb及無鉛銲錫Sn3.0Ag0.5Cu及Sn4.0Ag0.5Cu三種錫球材質之電子封裝元件進行循環剪力測試與彎曲測試。
　　研究結果指出，在0.4mm與0.525mm兩種綠漆通孔尺寸之測試元件中，綠漆通孔尺寸較寬可提升銲點之可靠度，且無鉛銲錫相較於有鉛之錫鉛合金銲錫也具有較高之平均壽命，但無鉛銲銲錫之壽命分佈則變異性較大。此外，三層樑理論模型與有限元素分析中所探討FCBGA元件於熱循環分析及剪力分析時之應力變化及分佈狀況，得知機械性剪力測試較近於熱循環之受力狀況。而機械性彎曲測試由實驗及分析之結果來看，與熱循環測試所呈現之結果仍有落差，而此研究結果對於提升電子元件可靠度測試之效率與準確性極具應用價值。

關鍵字

有限元素分析 ； 疲勞壽命 ； 覆晶球柵陣列構裝 ； 循環剪力測試 ； 綠漆通孔

並列摘要

The Accelerated Thermal Cycling(ATC) test is probably the most important and widely adopted reliability methods in various electronic packaging applications. However, it usually takes more than a thousand hours on this time-consuming test that also often causes a bottle-neck in the reliability test. As a result, mechanical stress test such as bend test and shear test, that requires much less time are used as a substitute to shorten the cycling time. However, which is the best alternative of ATC test between these two mechanical tests, deserves more detailed studies. Hence, the study conducts the theoretical mechanics analysis, failure modes analyses, and Finite Element Analysis (FEA) on the flip chip ball grid array(FCBGA) components with the bend, shear and thermal cycling test. It is expected to find, in particular, an accelerated mechanical test that can fully represent the ATC test but also compatible in the physics of package reliability.
In the theoretical analysis, a simplified Suhir’s tri-layer beam model which resembles the component’s packaging structure is utilized to evaluate interfacial normal and peeling stresses. In the mean time, the FEA of the same packaging is also conducted to simulate the bend, shear, and ATC test. An insight of the stress distributions on components under those reliability tests are obtained for the comparison purposes. Regarding the reliability test, both leaded solder material with composition of 63Sn37Pb and unleaded solder with Sn3.0Ag0.5Cu, Sn4.0Ag0.5Cu are used both in the bend and shear test.
The study showed that for the two 0.4mm and 0.525mm solder mask openings on components, the latter which with larger solder mask area has better fatigue life. Besides, the lead-free solder material is higher than that of eutectic solder materials in their average fatigue life, whereas the former has much more variations in the failed cycles no matter for cyclic bend tests or shear tests. Moreover, from the magnitude variations and the distributions of the thermal stress on the FCBGA package via the theoretical and nonlinear finite element analyses, it reveals that shear fatigue test is found to be in good agreement with the results from ATC. It is concluded that shear test should be taken as the best alternative for ATC test. The established results can be advantageous to the industry applications in the efficiency by shortening the test time and the correctness due to closer failure physics to that of ATC test.

並列關鍵字

Fatigue Life ； Finite Element Analysis ； Flip Chip Ball Grid Array ； Shear Fatigue Test ； S/M Opening Size

參考文獻

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