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Features of galvanic treatments Gold plating
The gilding process is widely used, as well as for decorative purposes, in applications sectors for important sectors: electronic, space, defense, microelectronics, nuclear, telecommunications.
Why gold? For a number of reasons:
- It is the noble metal par excellence: it does not oxidize and is stable over time;
- It has a high resistance to corrosion, even in the most corrosive environments: it is attached only by white spirit water (a mixture of nitric acid and concentrated hydrochloric acid) and by particular solutions specially formulated with presence of cyanide;
- It has a good resistance to corrosion from "fretting"; (contact or frictional corrosion);
- It has a contact resistance low and stable over time.
- It has good electrical conductivity, second only to silver and copper;
- It is easily weldable;
- Up to 98% it reflects the infrared rays (heat shield against heating by radiation);
- It has a high shielding power to the X-rays, resembling lead.
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The gold plating can be applied to any type of base metal with a suitable "barrier" layer, normally in nickel (and in most cases chemical-Ni): it improves corrosion resistance by reducing the porosity arising from the base material and lowering the difference of electric potential between the base metal and gold; blocks the diffusion phenomenon that occurs at operating at temperatures above the ambient one (especially between copper and gold), which alters the typical characteristics of gold. A layer of silver under the gold is strongly discouraged especially for electronic components (ref. Standard MIL-DTL-45204).
Heat shield - Gold plating on aluminum base made for the radiometer SLSTR Selex ES for the mission of ESA Sentinel 3 |
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The Galvanic Paciotti offers two types of gilding:
> PURE GOLD
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Carrier for microelectronics/space - Au 99.9% on aluminum base
Details for space - Au 99.9% on aluminum base
Housing for space – Au 99,9% on aluminum base |
High purity gold, deposited from baths free from organic or metallic additives (brighteners / hardeners), particularly suitable for applications in space, microelectronics, nuclear engineering, components for semiconductor and vacuum applications.
• MIL-DTL-45204 (Tipo III - Grade A)
Its main features are:
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> HARD GOLD
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Co-deposited gold with a small percentage of cobalt (typical 0.2%) which gives it a higher hardness, which makes it particularly suitable for electrical contacts, connectors and for general applications where you do not require applications such as bonding/thermal-compression. It is used both for decorative and protective purposes in various commercial and civil sectors, both in the defense, space and electronics in general. This type of browning meets the requirements of the standards: • MIL-DTL-45204 (Tipo I - Grade C) • ASTM B488 (Tipo I - Code C) |
Its main features are:
- Semi-glossy – shiny appearance, depending on the type of finish of the treated surface and of the applied thickness;
- Hardness (Knoop): 130-200 HK25
- Purity: 99.7% Minimum
- Density: 17.5-18 g / cm3
- Melting point: 1064 ° C
- Good wettability which allows soldering with tin-based alloys.
- Resistance to temperature up to 260 ° C (over that temperature discolorations or stains formation can occur).
- Good wear resistance, that makes it suitable for electrical contacts subject to rubbing.
- Ideal for small parts (screws, nuts, turrets…), it is used in the electrical/electronics industry and on printed circuit boards.
- It has a good reflectance, which combined with the ability to have polished finishes, makes interesting its use for mirrors/laser cavity.
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