To secure the reliability of lead free solder is a critical issue for a chip-scale packaging process. While lots of researches on the solder reliability have been conducted by applying numerical simulation techniques, researches on IMC (intermetallic compound) are not intensively condoned due to its thin thickness, geometric irregularity and so on. However, the IMC layer which is generated during the solder bumping process between solder and substrate is known as a key material determining the failure of solder joint. In this paper, the failure mode of solder joint is investigated by simulating the board level drop test which is described in the JEDEC standard. In this context, the IMC layer is produced by an ENEPIG process. Material properties of the IMC layer are obtained by performing a nano-indentation test for several points in the IMC region and the resulting test data are used for 3-dimensional finite element analyses to simulate the failure behavior. As a result, the solder joint corresponding to ENEPIG(0.1/0.8/0.12) surface finishing shows more resistant tendency against the drop impact failure than any other solder joint owing to a strain softening effect prior to the failure. The solder joint corresponding to ENEPIG(5/0.4/0.12) surface finishing, however, shows a sudden brittle failure mode due to the brittle characteristics of Nickel layer. (C) 2009 Elsevier B.V. All rights reserved.