Reliability issues of direct chip attachment using no-flow underfills

Abstract

Direct chip attachment is becoming more popular when the demand for smaller consumer electronics is growing. In order to achieve high reliability, underfills are important for flip chip devices since the materials used in microelectonics packaging have such a large differences in coefficient of thermal expansion. Capillary flow underfilling is the leading underfilling technique today, but new techniques are being developed in order to minimize the amount of processing steps and to reduce the processing time. No-flow underfilling is relatively new technique, and it is still being developed. The use of no-flow underfills reduces processing steps and also shortens the processing time. When these underfills are developed and used, new issues need to be considered.In this thesis, the no-flow underfills are described, and the interconnection with no-flow underfills is studied. Two different no-flow underfills are used in this study, and the joining is done using a flip chip bonder as a pick and place machine and reflow oven to melt the solder and to cure the underfill. During these tests different alignment parameters are used, and the interconnection yield is studied. The results showed that the no-flow underfills still need to be developed, but when the interconnection yield is high, this technique is very promising. /Kir10