Gold Plating- Electrical contacts are necessary electronic circuit components in every device that regulates electricity flow. Contacts are often found in circuit breakers, relays, connectors, and switches, and they open and shut the electrical circuit that runs through them. The circuit is “closed” and capable of carrying electricity when the contacts are joined. The circuit is “open” and stopped when contacts are separated by an insulating air gap.
Conductive metals such as nickel, copper, cadmium, and other alloys are used in many conventional and special electrical connections. Although these materials are competent, oxidation, corrosion, erosion, and heat may and do cause them to deteriorate over time. To safeguard their contacts and increase their capabilities, several manufacturers add a thin layer of gold plating with nickel undercoating.
What Is the Purpose of Gold Plating?
You’re probably asking why gold plating is used on electrical contacts; after all, the precious metal is pricey. Gold, on the other hand, has a number of physical and chemical characteristics that make it perfect for electrical use. Here are a few reasons why it’s a good long-term investment.
- Better corrosion resistance. Gold has a high resistance to oxidation, which causes corrosion, making it excellent for connections that are exposed to corrosive environments or agents.
- Corrosive conditions and substances damage metals frequently used in contacts, interfering with their conductivity. Under these circumstances, gold does not degrade and protects the contacts from corrosion and rust.
- Increased durability. Gold protects contacts from everyday wear and tear, such as fretting, which is erosion caused by continuous rubbing and friction; this may significantly extend the life of a contact.
- Ease of use. An electrical contact just needs a very thin layer of plating; any more coating would reduce the contact’s effectiveness. Because gold is such a flexible metal, it’s easy to apply the right amount of plating for each application.
- Gold’s characteristics make it a viable kind of protection for contacts that are regularly exposed to high temperatures (>125°C/257°F).
AMP Incorporated has published many criteria for the use of gold plating in electrical connections. Some of these criteria are summarised here.
- High Dependability Applications with Gold Plating — The detachable contact interface must be insulated from environmental degradation for connection applications in electronics that demand reliability. The application of gold to the interface of a detachable connection results in a component with a long, stable, and extremely low contact resistance.
- Corrosive Conditions and Gold Plating – Corrosive environments, such as high humidity or an atmosphere containing corrosive chemicals such as chlorine or sulphur fumes, will attack and damage metals such as nickel. Corrosion will cause electrical contact to be disrupted. In these circumstances, gold does not degrade. However, if the gold plating is too thin or porous, it may break apart, thus it is critical that the plating be done at the proper thickness and with an appropriate bottom layer metal for complete protection.
- Suitable Under Layer Metals for Gold Plating –To minimise gold plating deterioration, particularly in corrosive conditions like those indicated above, gold plating should be put over a quality metal like nickel as an underlayer. For a gold-plated surface, a nickel underlayer will operate as follows:
- Pore-Corrosion Inhibitor — Nickel as an underplate inhibits gold plating from corroding via pores in narrow places.
- Corrosion Creep Inhibitor – Protects against corrosion by forming a barrier.
- Diffusion Barrier – Prevents other metals, such as copper or zinc, from diffusing into the gold surface.
Nickel boosts the longevity of gold plating by functioning as a mechanically supporting under layer for contact surfaces.
Gold Plating Thickness Determined by Electronic Component Requirements – The appropriate gold plating thickness is determined by the electronic component’s intended use. Despite the recent drop in the price of gold, a smart place to start when selecting the overall thickness of the plating is to maintain the plating thickness as low as possible.
“In general, a 0.8 micron (30 microinches) hard gold coating over a minimum of 1.3 microns (50 microinches) nickel delivers a degree of durability deemed suitable for most connection applications,” according to the AMP research. Hard or soft gold thin coatings of 0.03 – 0.1 microns (1 – 4 microinches) over nickel underplate should be utilised exclusively for situations where fretting is unlikely. When the thickness of a gold coating is increased, the porosity decreases, reducing the sensitivity of the contacts to pore corrosion.
Contacts with gold plating that work at high temperatures – Gold’s characteristics make it a good choice for electrical connections that are subjected to high temperatures (>1250C/>257°F). The nominal gold and nickel thicknesses should be raised to provide protection against high temperatures.
Prior to plating, each application of the electronic component to be plated should be decided to ensure that all elements are considered and planned for in order to achieve the desired performance.