Gold plating

The microns of thickness determines how long the gold plating lasts with usage.

Gold, applied by evaporated methods or electroplating, has been specified by NASA to thermally control spacecraft instruments, due to its 99.4% reflectivity in infrared wavelengths.

A layer of a suitable barrier metal, usually nickel, is often deposited on the copper substrate before the gold plating.

These include what the deposit will be used for, configuration of the part, materials compatibility and cost of processing.

Selective plating is used, depositing the nickel and gold layers only on areas where it is required and does not cause the detrimental side effects.

Gold reacts with both tin and lead in their liquid state, forming brittle intermetallics.

The ongoing intermetallic reactions also cause Kirkendall effect, leading to mechanical failure of the joint, similar to the degradation of gold-aluminium bonds known as purple plague.

A 2–3 μm layer of gold dissolves completely within one second during typical wave soldering conditions.