本論文中，我們將討論金屬披覆層於系統級半導體封裝結構表面所產生的電磁屏蔽率之效益以及相關之製程方法、結構穩定性以及可靠度。
首先我們先研究系統級半導體封裝結構及其製程特性,設計一電路結構,將封裝結構之接地屬性利用導電金屬體延伸並連結至金屬披覆層,讓濺鍍製程所形成金屬披覆層達到接地屏蔽之屬性.
接著在金屬披覆層設計過程中,我們依據傳輸線理論及平面波屏蔽效應理論來分析並驗證此金屬披覆層於封裝結構帶來的電磁防護效能, 在理論分析結果顯示,由於金屬層厚度約略介於1毫米至4毫米,如此厚度所帶來的吸收效應有限;因此,反射效應成為此金屬披覆層所產生之電磁屏蔽效能的主要來源. 依據平面波屏蔽理論,選用導電性較佳之材料能夠提高該屏蔽材料與空氣界面之阻抗差距,進而達到較好之反射效能,提高屏蔽效能. 依據基礎理論所設計電磁屏蔽結構,我們設計一個實驗,包含一個具有所提出電磁屏蔽的測試樣品及相對應的測試系統,並使用電磁模擬軟體來預測電磁屏蔽效能.根據模擬及實際量測結果,在本論文中所提出的電磁屏蔽方案能夠在1GHz至 16GHz提供至少15dB的屏蔽效能,符合大多數電子產品在設計過程中對於電磁干擾抑制的需求.
此外,對於此金屬披覆層,我們也採用 ASTM D3359 之結合力測試方法測試金屬披覆層與半導體封裝體之結合力效能,並使用業界標準之JEDEC可靠度試驗條件測試此電磁屏蔽結構於半導體封裝之可靠度效能.This thesis presents an investigation of a novel EMI shielding method on semiconductor package, including related issues of shielding effect characterization, fabrication methods, process characterization and reliability performance.
Structure of the SiP module package and its fabrication flow are examined. The proposed shielding method is then designed by using an electrical conductive element to extend the electrical ground to side surface of semiconductor package, capable of connecting to the metal coating layer. Consequently, the metal coating layer is formed on the top surface and side surface of the semiconductor package by sputtering metallization technology and the metal coating layer is allowed to connect to the conductive element.
During the concept design of the proposed shielding structure, shielding effectiveness of metal coating layer on SiP module semiconductor package is analyzed using the transmission line theory and plane wave shielding theory. Based on the above theories, since the thickness of metal coating layer is around 1um ~ 4um in which the thickness fails to provide an excellent absorption performance, the reflection mechanism is the major contributor of shielding effectiveness. Additionally, the shielding material with higher electrical conductivity can enlarge the impedance mismatch between the shielding material and outside environment, which can provide improved reflection performance and shielding effectiveness. Based on the above theories, a test vehicle is designed and the shielding effectiveness of test vehicle is characterized by electrical simulation software and shielding effectiveness measurement system. Evaluation results demonstrate that the shielding performance of the proposed methodology can exceed 15 dB above, from 1GHz to 16GHz, thus satisfying EMC requirements of electronic product design.
Since the coating layer material differs from the package encapsulation material, this work attempts to enhance the adhesion between the metal coating layer and package surface by implementing and optimizing the plasma clean process. The adhesion performance is also verified by following the American Society for Testing and Materials (ASTM) D3359 standard adhesion test. Furthermore, the reliability performance is verified using the industrial standard Joint Electron Devices Engineering Council (JEDEC) reliability test items and criteria. Analysis results indicate that the test vehicle reaches best level (level-5B) of ASTM D3359 and passes the selected JEDEC reliability test items, demonstrating that the proposed shielding method can withstand an additional assembly process for electronic products and outside environmentAcknowledgments i
中文摘要 ii
Abstract iii
Chapter1 Introduction 1
1.1 Background and Objective 1
1.2 Conventional Shielding Solution and Proposed Shielding Architecture for Semiconductor Package 1
1.3 Organization 5
Chapter 2 Electromagnetic Shielding Theory 6
2.1 Shielding Theory and Wave Impedance 6
2.2 Shielding Effectiveness 8
Chapter 3 Conformal Shielding Fabrication and Characterization 15
3.1 Metal Coating Methodologies of Semiconductor Package 15
3.1.1 Electrolytic Plating 15
3.1.2 Spray Coating 16
3.1.3 Sputtering Metallization 18
3.1.4 Enhanced Metal Coating Adhesion Method 20
3.2 Adhesion Test Method and Evaluation Results 22
3.2.1 Adhesion Test Method 22
3.2.2 Adhesion Test Result 23
3.3 Test Vehicle Fabrication and Evaluation Results 26
3.3.1 Fabrication of Test Vehicle 26
3.3.2 Reliability Test of Test Vehicle and Result Discussion 31
Chapter 4 Conformal Shielding Effect Characterization 34
4.1 Schematic of Test Vehicle Design 34
4.2 Simulation of Shielding Effectiveness 35
4.2.1 Simulation Molding of Test Vehicle 35
4.2.2 Simulation Results 36
4.3 Measurement of Shielding Effectiveness 41
4.3.1 Shielding Effective Measurement Methodology 41
4.3.2 ASTM D4935 Measurement Method 41
4.3.3 GTEMTM Measurement Method 43
4.3.4 Evaluation Results of Test Vehicle 45
Chapter 5 Conclusion and Future Developments 51
5.1 Summary 51
5.2 Future Developments 51
References 5
