Technical Articles From Enthone

To Quantify a Wetting Balance Curve

Oct 19, 2017 | Frank Xu Ph.D., Robert Farrell, Rita Mohanty Ph.D.

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....