Gold plating

Gold plating is commonly used as connector coating and in other places where preservation of the electrical contact is necessary. Gold protects well from corrosion, and the deposit will not oxidize. The coating also looks attractive and is suitable for many decorative purposes.

Pinnoitus Helin Oy’s gold plating solutions:

  • Bath type: hard gold (99.7 % Au, the rest is additives affecting hardness)
  • Hardness: 110-170 HV
  • Method: barrel or hanging
  • Maximum dimensions of the object: 700x500x250 mm
  • Materials to be coated: aluminium, copper, steel, and their alloys

Gold plating is an important coating used by electrical and electronic industries, and is often an important part of faultless functioning of a product. There are several types of gold plating processes. It is important to select a process best suitable for each object, and determine the least possible gold thickness. For the proper functioning of the gold plating, a mid-layer coating is also necessary to prevent the mixing of different metals (diffusion problem). Nickel is the most common material used as a mid-layer.White bronze or palladium are used in objects where allergic nickel may not be used for health reasons.

  • Hard gold is most common in electrical and electronic industry contacts. The coating can be precipitated in many different thicknesses and it is non-porous. Typical thicknesses include 0.20µm, 0.50µm and 1.2µm. Metals that increase hardness, usually cobalt or nickel, will coprecipitate into the coating. Solderability is good with thin layer thicknesses, but gets more difficult with thicknesses over 0.5µm.
  • Soft gold coating has no hardness increasing materials, and it is well solderable in all layer thicknesses.
  • Immersion Gold Plating is a reaction coating that gives minimal or temporary protection against oxidation. The process does not use electrolysis but is based on displacement with a less precious base material. The reaction is not autocatalytic and it ends when the outer atoms of the base material or mid-layer have been exchanged with gold. The maximum thickness of the coating is about 0.2µm and it is well solderable.
  • Gilding is used only for decorative coatings. The coating color hue selection is wide, resulting from additives (metals) that give the desired hues. The additive content in the coating can reach 40 %. For this reason gilding is not suitable for electronics.
  • ENEPIG is a combination coating. Its usage increased after the RoHS directive became effective. When lead free soldering materials are used, ENEPIG gives a very reliable solder in high temperatures. The coating is formed as a combination of electroless nickel, electroless palladium, and immersion gold. The recommended thicknesses are Ni3-5µm, Pd0.16µm and Au0.2µm.