Issue link: https://iconnect007.uberflip.com/i/410144
44 The PCB Magazine • November 2014 and immersed in SAC305 at a temperature of 255°C for ten seconds. Further: 1) Ten samples per test shall be run. 2) The mean and standard deviation of the maximum force achieved shall be documented. Interestingly, the committee has also rec- ommended that a second set of test coupons be processed under the same pretreatment condi- tions. This time, however, without the drying step. Again, the ANSI-JSTD-003B, wetting bal- ance procedure to measure wettability, will be utilized. I would also suggest that there is another way with that one can determine whether a particular OSP is lead-free compatible: Does the particular organic film stand up to high temperatures? Further, this relates to the tem- perature at which the OSP film begins to de- compose (Figures 1 and 2). The data shows that depending on the chemical structure of OSP molecule, the resistance to thermal de- composition of the organic film can be differ- ent. Obviously, the greater the temperature re- sistance of the OSP, the better the chance that the film will protect the underlying copper from significant oxidation. Remember, it is all about the oxidation or lack thereof that we are looking for. Regardless, it is highly recommended that fabricators follow a set procedure to qualify any OSP and its suitability as a lead-free compatible coating. Before doing that, however, it is critical to realize that the thickness of the OSP film plays a role in its ability to protect the underlying cop- per surface from oxidation. So, how can one en- sure that the film thickness is sufficient to func- tion as a lead-free compatible OSP? One test that is very simple to implement is the silver nitrate test. The procedure is as follows: LEAD-FREE COMPATIBLE OSPS: WHAT DOES THIS REALLy MEAN? continues figure 1: benzimidazole type osP.