Issue link: https://iconnect007.uberflip.com/i/1533904
74 SMT007 MAGAZINE I APRIL 2025 finish. is is followed by preheating the components on a hot plate, then manually applying RMA flux to the leads before mov- ing each component into the same static sol- der pot for re-tinning. When component leads are manually tinned, several issues can arise. e manual tinning process may not create a high-qual- ity intermetallic bond on the lead, leading to a poor base metal and a rough surface finish. When soldering to a printed circuit board, the solder can initially wick up the lead and wet the plated through-hole. However, once the re-tinned surface becomes liquidus, the sol- der may partially run back down or migrate away from the lead, resulting in de-wetting at the targeted soldering temperature. us, the de-wetting at the joint site and poor sol- derability can oen be traced to irregularities from the manual tinning process that nega- tively impact the intermetallic bond. An additional disadvantage of using a sin- gle solder pot is the risk of contamination. Since there is no circulation within a static solder pot, the composition of the surface level solder is dependent on the specific grav- ity of the elements present. is is especially problematic when using a static pot to per- form both alloy removal and refinishing of a component's leads. If the original lead finish is gold-plated, the gold can dissolve into the static pot, potentially altering the composi- tion of the solder alloy. Furthermore, a static solder pot, as seen in Figure 1, may contain other contaminants, such as dross, RMA flux residues, and oxidation on the surface, which can negatively impact solderability. Another drawback of repeatedly using a single static solder pot is that organic con- taminants, such as mold release agents, can float on the surface of the molten sol- der. ese agents will not be driven off by heat unless temperatures exceed 500°C. e presence of these organic contaminants in the static solder pot can be verified using either atomic absorption (AA) analysis or infrared spectrophotometr y with Fourier transform (FTIR). Figure 1: A static pot may contain other contaminants, such as dross, RMA flux residues, and oxidation on the surface, which can negatively impact solderability.