To Quantify a Wetting Balance Curve

Wetting balance testing has been an industry standard for evaluating the solderability of surface finishes on printed circuit boards (PCB) for many years. A Wetting Balance Curve showing Force as a function of Time, along with the individual data outputs "Time to Zero" T(0), "Time to Two-Thirds Maximum Force" T(2/3), and "Maximum Force" F(max) are usually used to evaluate the solderability performance of various surface finishes. While a visual interpretation of the full curve is a quick way to compare various test results, this method is subjective and does not lend itself readily to a rigorous statistical evaluation. Therefore, very often, when a statistical evaluation is desired for comparing the solderability between different surface finishes or different test conditions, one of the individual parameters is chosen for convenience. However, focusing on a single output usually doesn't provide a complete picture of the solderability of the surface finish being evaluated.

In this paper, various models here-in labeled as "point" and "area" models are generated using the three most commonly evaluated individual outputs T(0), T(2/3), and F(max). These models have been studied to quantify how well each describes the full wetting balance curve. The solderability score (S-Score) with ranking from 0 to 10 were given to quantify the wetting balance curve as the result of the model study, which corresponds well with experimental results....