Gold is by far the most popular plating metal. Functional, practical, effective. Superior corrosion resistance, spectacular aesthetics. Yellow to orange color depending on proprietary process used. Will range from matte to bright finish depending on basis metal. Good corrosion resistance, and has high tarnish resistance. Provides a low contact resistance, and is a good conductor. Has excellent solder-ability. Unless otherwise specified, an intermediate nickel plate is required on copper base alloys or copper plated surfaces prior to the gold plating.
Type I 99.7% gold min.
Type II 99.0% gold min.
Type III 99.9% gold min.
Class 00 0.00002" min.Grade A 90 Knoop max
Class 0 0.00003" min.Grade B 91-129 Knoop
Class 1 0.00005" min.Grade C 130- 200 Knoop
Class 2 0.00010" min.Grade D above 200 Knoop
Class 3 0.00020" min.
Class4 0.00030" min. Type I (Grades A, B or C)
Class 5 0.00050" min. Type II (Grade B, C or D)
Class 6 0.00150" min.Type III (Grade A only)
here are several types of gold plating used in the electronics industry:
l Soft, pure gold plating is used in the semiconductor industry . The gold layer is easily soldered and wire bonded . Its Knoop hardness ranges between 60-85. The plating baths have to be kept free of contamination.
l Bright hard gold on contacts, with Knoop hardness between 120-300 and purity of 99.7-99.9% gold. Often contains a small amount of nickel and/or cobalt ; these elements interfere with die bonding, therefore the plating baths cannot be used for semiconductors.
l Bright hard gold on printed circuit board tabs is deposited using lower concentration of gold in the baths. Usually contains nickel and/or cobalt as well. Edge connectors are often made by controlled-depth immersion of only the edge of the boards.
l Soft, pure gold is deposited from special electrolytes. Entire printed circuit boards can be plated. This technology can be used for depositing layers suitable for wire bonding.