A Study on Warpage Behavior of Underfill in Flip Chip

The reliability of electronic packaging is a systematic project, which involves aspects of the design of packaging structure, packaging process technology, characteristics of packaging materials, and the use of the environment. Various factors take effect on package defects and failures, such as material composition and properties, package design, environmental conditions, and process parameters. However, the phenomenon of warpage caused by the mismatch of thermal expansion coefficients between chips and substrates is one of the most important problems in device reliability research.The paper independently designed a test vehicle structure that simulates an actual chip to study the warpage behavior of underfill during curing and reflow soldering. In the study, underfill containing five different kinds of toughening agents were used to study the effect of curing stress on warpage behavior, thereby reducing the warpage behavior of underfill and improving package reliability from a formulation perspective.The results showed that the warpage behavior of underfill in the curing process of test vehicle structure mainly occurred in the cooling stage, but almost didn’t take place in the heating and curing stages. Through studying the effects of five toughening agents on the warpage behavior, it was found that the addition of toughening agents reduced the amount of the warpage of the test vehicle structure, which varied with different types of toughening agents. In the process of simulating reflow soldering, the warpage behavior was alleviated to a certain extent, and different categories of toughening agents took different effects. Finally, the most suitable toughening agent for underfill was successfully selected through the study, and the reliability of the device was improved.