| 研究生: |
張家豪 Chang, Chia-Hao |
|---|---|
| 論文名稱: |
以田口式品質工程分析QFN構裝體疲勞壽命之最佳化探討 Optimal Design of Fatigue Life for Quad Flat No Lead Package by Using Taguchi Method |
| 指導教授: |
陳榮盛
Chen, Rong-Sheng |
| 學位類別: |
碩士 Master |
| 系所名稱: |
工學院 - 工程科學系 Department of Engineering Science |
| 論文出版年: | 2007 |
| 畢業學年度: | 95 |
| 語文別: | 中文 |
| 論文頁數: | 123 |
| 中文關鍵詞: | 田口分析方法 、無鉛錫膏 、有限元素分析 、QFN構裝體 |
| 外文關鍵詞: | Finite element analysis, Fatigue Life, Lead-free Solder Paste, Taguchi Method, QFN package |
| 相關次數: | 點閱:106 下載:8 |
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四方扁平無腳封裝為接近晶片尺寸級封裝具有極細間距與小尺寸的特色,可提高印刷電路板的利用率,而與TSOP或QFP封裝體比較,體積縮小了60%,而且成本又低於CSP,非常適合於小型可移動產品之應用,再者,使用銅導線架之膠體封裝,並利用錫膏將QFN連接到印刷電路板上,因縮短連接距離,可增加電性能。此外,中央大的晶片墊,可將封裝體之熱量迅速地傳到印刷電路板上,具有良好的熱性能。
本研究將採用ANSYS9.0套裝分析軟體,根據JEDEC規範將QFN構裝體施予-40℃~125℃的溫度循環負載,而錫膏以亞蘭德黏塑性分析法,及使用Coffin-Manson疲勞壽命預測公式來計算QFN構裝體錫膏的疲勞壽命。
在本文中考慮溫度循環範圍振幅、溫度循環範圍平均溫度、晶片厚度、印刷電路板厚度、印刷電路板熱膨脹係數、封膠熱膨脹係數、結構黏膠熱膨脹係數、錫膏外觀形狀與晶片墊熱膨脹係數等因子,進行單一因子分析,以評估各因子對封裝結構疲勞壽命的效應,然後將上述各因子利用田口品質設計,建立直交表進行實驗,並經誤差統合,找出最佳化的參數組合,並且有效改善QFN構裝體之可靠度。
由單一因子分析結果顯示,藉由縮小溫度循環範圍振幅、減少印刷電路板厚度、降低晶片墊熱膨脹係數、增加印刷電路板熱膨脹係數、增加封膠熱膨脹係數、增加錫膏高度,皆能有效提高QFN構裝體疲勞壽命,其餘因子對QFN構裝體疲勞壽命的影響性並不大。最後,利用田口品質設計所得最佳製程參數之構裝體疲勞壽命為3587次,而原始製程參數設計之構裝體疲勞壽命為1050次,疲勞壽命約提昇3.42倍,因此有效改善QFN構裝體之可靠度。
Since the quad flat no-lead package (QFN) is closed to Chip scale package with characters of fine pitch and small outline.It is facilitated to increase the utility rate of PCB and Compared to TSOP or QFP, QFN is in favor of 60% reduction in volume and less costs than CSP which is good for the application of small size and portable products. Furthermore, with the lead frame filled with an epoxy mould compound, and connecting to PCB through the solder paste , QFN has advantage in shortening the circuit so that the electrical performance can be promoted. Besides, the large central Die pad is in favor of prompt heat transfer to PCB and hence has advantage in thermal performance.
This study will adopt ANSYS9.0 software for analysis.Based on JEDEC code,QFN will be loaded by a temperature cycle of -40℃~125℃.The solder paste is assumed to be Anand’s viscoplastic, then the Coffin-Manson fatigue life formula will be applied to predict the fatigue life of the solder paste in QFN package.
The single-factor experiment was adopted to predict the impact on fatigue life of QFN by following factor: the the control factors are the amplitude of temperature cycling range,the mean temperature of temperature cycling range ,thickness of Die, thickness of PCB,CTE of PCB,CTE of Mold Compound,CTE of structural adhensive,the shape of solder paste,CTE of Die pad.Finally,the Taguchi Method was applied to obtain an option parameter combination to improve the reliability of QFN package.
The results of single-factor study showed that by reducing the amplitude of temperature cycling range, thickness of PCB,CTE of Die pad as well as by increasing CTE of PCB, CTE of Mold Compound and the standoff of solder paste, will increase the solder fatigue life. On the other hand, the other factors have no significant effect on the solder paste fatigue reliability.
Finally,the optimal design from Taguchi Method optimized the fatigue life of 3587 cycles, but the original design had much less fatigue life of 1050 cycles, the optimal design had 3.42folds on the fatigue life over the original design, far improving the reliability of QFN module package.
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