Entrapped Silicone Can Prevent Solder Wetting to Tin-Plated Leads

What the evidence preview establishes

Silicon-rich contamination, most consistent with silicone, was entrapped within and distributed over the electroplated tin leads. It prevented effective solder wetting and produced weak solder-to-lead interfaces that fractured readily.

Why this case matters

When only one component type resists soldering despite adequate flux and heat, inspect unused leads in cross-section. Contamination embedded within a plated finish cannot be corrected reliably by ordinary board-level cleaning or rework.