Surface treatment & coatings for contact springs

Q: Which coatings are suitable for which requirements?

Gold : highest reliability, oxidation-free, highly conductive Silver : best electrical conductivity, good solderability Nickel : good corrosion protection, often used as a base layer Tin : inexpensive, good solderability Palladium/PdNi, rhodium, platinum : particularly robust and abrasion-resistant for special applications The choice depends heavily on factors such as cost, load, contact resistance and environmental influences.

Surface treatment

Surface treatment plays a key role in the reliable functioning of contact springs. The choice of the appropriate process depends heavily on the area of application, the electrical requirements, the mechanical load and the environmental conditions.

Objectives of surface treatment

Contact springs are surface treated to optimise their electrical, mechanical and chemical properties. The main objectives are:

Reduction of contact resistance
Prevention of oxidation and corrosion
Increase in wear resistance
Improvement in solderability

Types of surface treatment

Surface treatment can be divided into two main categories:

1. Mechanical processes

These change the topography (i.e. the roughness, shape or cleanliness) of the surface.

Polishing / grinding
Smoothing the surface for better contact areas
Brushing / blasting
Removes oxides or burrs
Deburring
Prevents mechanical damage during installation
Ultrasonic cleaning
Removes the finest particles and films

2. Chemical-physical processes

These change the chemical composition or structure of the surface.

a) Coatings (plating)

Applied electrochemically by rolling

Coating	Advantages	Note
Gold (Au)	Oxidation-free, highly conductive, durable	Expensive, often on Ni intermediate layer
Silver (Ag)	Highest conductivity, easy to solder	Tends to oxidise
Nickel (Ni)	Good corrosion protection layer	Often used as a base for precious metals
Tin (Sn)	cost-effective, good solderability	soft
Palladium (Pd/PdNi)	robust, abrasion-resistant	good alternative to gold
Rhodium (Rh), platinum (Pt)	Very hard, corrosion-resistant	For special applications
Cadmium with passivation (Cd)	Very good corrosion protection	For special applications

b) Passivation / conversion coatings

Protective films, e.g. through chemical treatment with acids or bases
Cadmium passivation (e.g. through colour coating) is used in military and aviation technology as it offers excellent corrosion protection.
Silver thiol passivation: forms a protective chemical layer on silver surfaces, improves corrosion resistance

Selection criteria for the right surface

The appropriate surface treatment depends on several factors:

Criterion	Typical decision
Environmental influences (moisture, chemicals)	Gold, platinum
Type of mechanical stress Sliding contact, pressure contact Dynamic – static	PdNi, rhodium
Cost factor	Tin, nickel
Contact resistance	Gold, silver

Coating methods

Surface coating – rack electroplating for complex geometries

Rack electroplating is suitable for series, small series and individual items, even in larger formats. Sensitive workpieces or those that are unsuitable due to their shape are fixed to racks and coated with precision. Partial coatings are also possible.

[Translate to Englisch:] Oberflächenbearbeitung Trommelgalvanik

Surface coating – barrel plating

Barrel plating is ideal for the cost-effective finishing of large quantities of small or sensitive components. They pass through all process steps in an automated treatment line. Even complex parts with threads or blind holes are processed gently and reliably.

[Translate to Englisch:] Oberflächenbeschichtung – Virbotechnik (Vibrationsgleitspanen)

Surface coating – vibration technology (vibration finishing)

In vibration finishing, workpieces are set in motion with abrasive media in order to deburr, smooth or polish them. The process is ideal for large quantities and complex geometries and delivers consistent results with high cost-effectiveness.

From the idea to the perfect surface – we accompany you every step of the way

We would be happy to advise you on selecting the right process and work with you to develop a tailor-made coating solution.

Arrange a consultation 03379 - 20 82 92

Frequently asked questions from our customers about surface treatment

Why is the surface treatment of contact springs so important?

Surface treatment improves the electrical, mechanical and chemical properties of contact springs. For example, it reduces contact resistance, prevents corrosion and increases wear resistance. This significantly increases the reliability and service life of the components.

What surface treatment methods are available?

A basic distinction is made between mechanical processes (e.g. polishing, brushing, deburring, ultrasonic cleaning) and chemical-physical processes (e.g. electroplating, passivation, PVD/CVD coatings). The appropriate method is selected depending on the area of application.

Which coatings are suitable for which requirements?

Gold: highest reliability, oxidation-free, highly conductive
Silver: best electrical conductivity, good solderability
Nickel: good corrosion protection, often used as a base layer
Tin: inexpensive, good solderability
Palladium/PdNi, rhodium, platinum: particularly robust and abrasion-resistant for special applications

The choice depends heavily on factors such as cost, load, contact resistance and environmental influences.

What coating methods are used?

Different processes are used depending on the geometry, quantity and sensitivity of the components:

Rack electroplating: precise coatings, including partial coatings, for complex geometries
Barrel plating: cost-effective for large quantities of small parts
Vibration technology (vibration finishing): ideal for deburring, smoothing and polishing in series production