Organic solderability preservatives (OSPs) pad is one of the pad finishing technologies where Cu pad is coated with a thin film of an organic material to protect Cu from oxidation during storage and many processes in IC manufacturing. Thickness of OSP film is a critical factor that we have to consider and control in order to achieve desirable joint strength. Until now, no non-destructive technique has been proposed to measure OSP thickness on substrate. This paper reports about the development of EDS technique for estimating OSP thickness, starting with determination of the EDS parameter followed by establishing the correlation between C/Cu ratio and OSP thickness and, finally, evaluating the accuracy of the EDS technique for OSP thickness measurement. EDS quantitative analysis was proved that it can be utilized for OSP thickness estimation.

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.

In this work, we proposed new sample preparation technique (combination of mechanical and chemical method) for inspection of intermetallic bondballs. The use of this new method will provide more accurate estimation of the percentage of intermetallic formation area. The procedure to perform the sample preparation is: 1. Grind unit from the bottom side of the package until the bulk silicon die is visible. 2. Dipping the unit into KOH 50% solution at 100 to 110 degree C to remove the bulk silicon 3. Dip unit in HF : DI water (1:10) at room temperature to remove any diffusion layers, metal lines, barrier metal and inter-dielectric layers. Then clean the unit by using Hydrogen Peroxide (H2O2) 4. The images are imported into Image-Pro software to calculate the percentage values.