What is Gold Filled?
Gold filled jewelry contains a layer of Karat Gold, mechanically bonded to a layer of bronze (or another supporting alloy) before being rolled or drawn to the desired thickness.
The item maintains the same gold content throughout our signature production process. Our gold filled products contain either 12 or 14 Karat bonded to a bronze alloy layer.
Why is Gold Filled Superior?
Gold plating is used in the manufacture of jewelry. Gold atoms diffuse into the gold layer, causing slow gradual fading of its color and eventually causing tarnishing of the surface. This process may take months and even years, depending on the thickness of the gold layer. A barrier metal layer is used to counter this effect. Copper, which also migrates into gold, does so more slowly than silver. The copper is usually further plated with nickel. A gold-plated silver article is usually a silver substrate with layers of copper, nickel, and gold deposited on top of it.
The Drawbacks of using Gold Plating
Soldering gold-plated parts can be problematic as gold is soluble in solder. The solder which contains more than 4–5% gold can become brittle. The joint surface is dull-looking.
Gold reacts with both tin and lead in their liquid state, forming brittle intermetallics. When eutectic 63% tin – 37% lead solder is used, no lead-gold compounds are formed, because gold preferentially reacts with tin, forming the AuSn4 compound. Particles of AuSn4 disperse in the solder matrix, forming preferential cleavage planes, significantly lowering the mechanical strength and therefore reliability of the resulting solder joints.
If the gold layer does not completely dissolve into the solder, then slow intermetallic reactions can proceed in the solid-state as the tin and gold atoms cross-migrate. Intermetallics have poor electrical conductivity and low strength. The ongoing intermetallic reactions also cause Kirkendall effect, leading to mechanical failure of the joint, similar to the degradation of gold-aluminum bonds known as purple plague.