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Gold embrittlement poses a considerable reliability challenge in electronic assemblies. e risk of embrittlement depends on sev- eral factors, including the amount of gold that leaches from plated surfaces, the volume of the resulting solder joint, and whether the solder comes from an unlimited source, such as wave or selective soldering processes, or a limited source, such as solder paste. For sur- face mount technology (SMT) components, the small volume of solder paste applied to the pads can increase the concentration of gold in the molten solder. is heightened concen- tration raises the likelihood of gold dendrites forming within the solder joint, which can act as catalysts for crack propagation. Gold has a relatively low melting point and dissolves quickly during the soldering pro- cess. When excessive gold dissolution occurs during the solder alloy's liquidus phase, it can change the composition and mechanical properties of the resulting solder joint, lead- ing to further gold embrittlement when com- bined with other metals during solder joint formation. Typically, this stems from gold- plated component leads, not from contri- butions from PCB finishes, such as Electro- less Nickel Immersion Gold (ENIG) or Elec- troless Nickel Electroless Palladium Immer- sion Gold (ENEPIG). ese board finishes, averaging around 0.10 µm, are typically too thin to con- tribute significantly to gold embrittlement, as the thresh- old associated with potential issues is 0.25 µm. Manual soldering of SMT or through-hole solder joints, with their limited solder, results in a gold-rich envi- ronment, making them more prone to crack propagation. Using gold-finished compo- nents exacerbates this issue, causing embrittlement and voids in solder joints, thereby weakening the mechanical bond strength in PCB assemblies. Under certain conditions, gold-plated components can fail because of excessive remnant gold. Embrittlement in tin-lead (SnPb) solder joints is a known failure mechanism caused by excess gold. Meanwhile, lead-free sol- der alloys, such as SAC305, offer improved mechanical properties when combined with gold, mainly because of their higher tin con- tent. However, SAC305 solder joints are not immune to degradation from increased gold levels. Studies show a lack of defined accept- able gold thresholds in SAC305 solder joints, suggesting gold removal is the best practice. e 2014 release of Revision F of IPC-J- STD-001 addressed persistent gold embrit- tlement issues faced by end users, particu- larly due to insufficient turbulence during the wave soldering process in plated through- holes. IPC-J-STD-001 Rev F marked a sig- nificant shi in the Class 2 electronics man- ufacturing sector by making it mandatory to remove gold for many electronic compo- nents in Class 2 printed circuit board (PCB) assemblies. e IPC defines criteria with specific clas- sifications: "N" indicates no requirement, "A" denotes acceptable, "P" signifies a pro- cess indicator, and "D" denotes a defect. For 68 SMT007 MAGAZINE I MAY 2025 Figure 1: One drawback to using gold is that it's porous and can dissolve in eutectic tin-lead solder.