Publication: Investigation of thermal reflow process for copper pillar technology.
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Date
2022-07-25
Authors
Rosli, Muhammad Faiz Ridhwan
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Abstract
Modern gadgets are rapidly growing and providing multiple functions and applications for the users such as smart phones, laptops, desktops, etc. Since the invention of the microchip, modern technology has driven us forward to create smaller gadgets. For older technologies, traditional solder bump was used in most flip chips. Solder bumps have the range size of 75 to 150 microns and copper pillar bump have the range of 50 to 100 microns. Hence, copper pillar technology is taking over the traditional solder bump as it gains popularity to solve the new features and sizes of flip chips. However, the high-quality interconnection joint is dependent on the temperature profile of the reflow soldering process. Therefore, this research paper is pursued to predict the reflow temperature distribution, structure effects with variation of diameter of the solder and copper pillar bump; and validation of the copper pillar bump structure during the reflow soldering. The diameter of the solder and copper pillar bump is the core parameter of this research. This research was done by running a simulation for thermal reflow process by using the ANSYS Fluent software and conducting an experiment using an actual reflow oven with sac305 solder paste and copper substrate. The results show that solder with the diameter of 0.15mm has the highest peak temperature and the lowest peak temperature is the solder diameter of 0.35mm. Other than that, the highest reflow stage starting temperature is the solder diameter of 0.25mm and the lowest reflow stage starting temperature is the solder diameter of 0.35mm. Lastly, the highest final temperature for the thermal reflow process is the solder diameter of 0.35mm and the lowest is the solder diameter of 0.25mm. In order to advance the design for microelectronic industries in the future, this study provides a foundation and insights into the effects of copper pillar bump structure during reflow soldering.