Meaning
Metallic thin films deposited between electronic substrate surfaces and noble metal contacts prevent chemical migration at elevated temperatures. A gold diffusion barrier inhibits the movement of gold atoms into silicon or base metal interfaces. Without this intermediate layer, atomic intermixing leads to localized corrosion and electrical contact failure.
This structural integrity maintains the conductivity of gold plated components under high thermal stress.
Thermal Migration
Interface degradation occurs when gold diffuses into underlying layers during soldering or long term environmental exposure. Such movement creates brittle intermetallic compounds that compromise mechanical bond strength. A nickel layer is frequently employed for this purpose because nickel possesses high density and slow atomic mobility.
Proper application ensures the gold remains on the surface where it facilitates reliable connections.
Processing Variable
Deposition parameters define the density and grain structure of the barrier material. Vacuum evaporation or electroplating rates determine whether the film contains voids or porosity that allow metal ions to bypass the protective layer. High current densities during plating often produce internal stress that causes the barrier to fracture during thermal cycling.
Moulders monitor plating bath chemistry to ensure the deposited film matches the required thickness specifications.
Cost Impact
Excessive thinness results in component rejection due to premature electrical open circuits during accelerated life testing. Thicker coatings increase material expense and introduce potential adhesion issues when the assembly undergoes physical deformation. Optimization involves balancing the minimum thickness required for complete coverage against the rising cost of noble metal inputs.
Total performance depends on the uniformity of this layer across complex three dimensional geometries.
