SMT007 Magazine

SMT-Aug2018

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64 SMT007 MAGAZINE I AUGUST 2018 identify each specific residue that is present. The ROSE test provides a single bulk value (not ion selective) and liters of solution are often used, which affects the sensitivity. Please consider the results in the following table taken from our 2017 SMTAi presentation. Before I discuss the results in Figure 1, it would be prudent to first discuss what was done. First, the cleanliness of five different ball grid array (BGA) groups (i.e., size, ball count and pitch) was baselined using IC. We processed two replicates for each group because we had a limited number of parts to work with. The BGAs were then sent to be re-balled using a standard robotic reballing process. The ionic cleanliness of each group was then re-evaluated using the ROSE test as defined in the GEIA-STD-0006 and again with IC. The solvent volumes used for each test were five milliliters for the IC test and ninety- eight milliliters for the ROSE test. A side-by-side overview of what was done for this testing is shown in Figure 2. The different ions listed in Figure 1 are from the IC test. As we have indicated, IC has considerably greater selectivity than does ROSE and can identify specific ion species from a sample extract. At the bottom of the table is a red circle around the ROSE and IC results. The ROSE result is expressed as μg of NaCl equivalents per square centimeter. It is important to understand that this is neither a measurement of sodium nor chloride, but an expression of the result compared to a standardized solution of a NaCl salt, which is used to standardize the instrument. The IC results are given as micrograms of ion per square centimeter. The IC results are direct measurements made back to certified standards of specific ion species. Each ion species is calibrated separately. In our example, we compared the ROSE result with the sodium and chloride ion results Figure 1: IC has considerably greater selectivity than does ROSE and can identify specific ion species from a sample extract.

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