High Density Flip Chip on Flex (FCOF); Process, Materials and Reliability

摘要

In portable electronics product business there is a strong trend towards miniaturization. At the same time when the size and the weight of these products are decreasing the number of functions and the performance are increasing. This trend of miniaturization means that the packaging density is increasing significantly /1/. Target of our research was to develop small pitch flip chip on flex process for electronic module applications. In this paper the results from the reliability tests of 54 m and 80 m flip chip on flex (FCOF) are presented. Different type of flexible substrates and different types of anisotropically conductive adhesives were tested in high-density flip chip on flex application. The reliability of the samples was tested using thermal shock tests (-40C←→+125C) and 85°C/85RH environmental test. Cross section samples were made to analyze the possible failure mechanism of failed contacts. Two different test devices with two layouts for both pitches were used. The contact resistance was measured with four-point method and the serie resistance with Daisy chain method. The results are a part of European Union supported development project.