Abstract

The monitoring of intermetallic compound (IMC) at solder joints has become more important recently because it is understood that IMC thickness and composition are the factors which determine the quality and reliability of solder joints. Normally it is quite difficult to view IMC optically due to its small (nanometer scale) thickness so scanning electron microscope (SEM) imaging is required to perform the observation. However, the most important factor for successful observation is the sample preparation, the grinding, polishing, and etching process in particular. Therefore, in this work we will discuss our experiments to develop an effective sample preparation technique to facilitate the observation of the IMC at the solder joint. Proper sample preparation will provide a good contrast between the IMC and surrounding metals under the SEM. We used the following 2 sample preparation techniques for ease of IMC observation: Fine polishing process: Polishing the sample with diamond compound followed by silica. Acid etching process: Etching the sample in HNO3 solution. This process is relatively simple and takes less time than polishing but acid etching will damage the solder so that this method is not suitable if analysis of the solder ball is also needed.

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