Investigation and Determination of Maximum Delamination Strength of LED Film Structure by Point Load and Four Point Bending Tests
| Autor: | Yang, Shin-Yueh, 楊炘岳 |
|---|---|
| Rok vydání: | 2012 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 101 High-power light emitting diodes (LEDs) are found in a number of applications in high-volume consumer markets, such as illumination, signalling, screen backlights, automotives, and others, because of the numerous advantages of LEDs, including low power cost, long life span, and high efficiency. Wire bonding is one of the major processes in the LED packaging process that provide electrical interconnection between the bonding pad and the lead. However, due to bad parameter setup in a wire bonder, the LED will crack and the pad will peel after wire bonding. In this study, the strength of LED is determined for the design requirement in order to ensure good reliability of wire bonding. Point-load test (PLT) and focused ion beam (FIB) are used to determine the maximum allowable force the epilayer can withstand, which is approximately 75 g. By combining the finite element method and experimental data, a useful design tool to confirm LED die strength is provided. The finite element result of contact analysis show that the stress concentration area is located on the edge of the pin and maximum stress (212 MPa) occurs in the epilayer. Parametric study and new structure design are employed to find ways to reduce stress in LED layer. The results indicate that the strength of epilayer can be enhanced to resist the crack initiation due to new structure design. Furthermore, the four-point bending (4PB) delamination test and modified virtual crack closure technique (MVCCT) is adopted to measure and predict the critical energy release rate near the interface of multiple quantum well. Simulation results have a good agreement with the experimental data and show a weak adhesion near the interface. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|