Wire conductors are essential wire harness components, often requiring coatings to improve their solderability and electrical properties at high frequencies.
This article covers everything about coating wire conductors.
Let’s get started!
Types of wire conductors
Here are the different types of wire conductors;
Silver
Silver has the best conductivity but is expensive. So we often use it as a coating for copper to improve skin conductivity and offer some protection against corrosion.
Copper
Copper’s conductivity is second only to silver, and it is more economical, plentiful, and ideal for pressure crimping (termination, etc.) with breakthrough surface oxidation.
Copper wire
Aluminum
Aluminum has poor conductivity, making it difficult to sell or plate it while improving its solderability.
Copper-covered steel
This type of wire conductor combines the following;
- Strength of steel with the corrosion resistance
- Conductivity of copper
Copper-covered steel can be either of the following;
- Type 1: Molten welding permanently bonds copper and steel
- Type 2: A copper layer electroplated over a steel rod
- Type 3: The steel rod and copper metallurgically bonded
High-strength copper alloy
The most common high-strength copper alloys are;
- Chromium copper
- Cadmium copper
- Zirconium Copper
- Cadmium-chromium copper
Their ideal application areas include;
- Aerospace wires and cables applications
- Computer wires and cables applications
Stainless steel
These wire conductors have worse conductivity than copper.
However, gold-plating ones may improve their conductivity and make them ideal application areas, including medical lead cables and wires.
Tinned copper/ tin-coated copper wire conductors
Tin protects a copper conductor from corrosion without affecting its conductivity.
Also, It is eminently solderable.
A “tinned” conductor usually means one coated with a lead-tin alloy — a solder.
Tinned copper wire conductors are ideal for the following applications;
- Solder-dipping of stripped lead
- Manual twisting of the stripped lead
Soldering tin wire
Silver-coated copper/silver-plated copper electrical wire conductors
These wire conductors are ideal for;
- High-frequency applications where higher conductivity is desirable
- Wires operating between 150 degrees Celsius to 200 degrees Celsius
Nickel-coated copper/nickel-plated wire conductors
“Nickel coated” refers to a much thicker plating, and you can use them where silver plating is objectionable due to possible solder wicking.
The table below compares different conducting materials.
| For 30 AWG Wire | Temperature Coefficient2 | |||||||
| Relative Resistance | Lbs per 100 ft. | Ohms per 1000 ft. | “Ohm-Lbs-1 per 1000 ft. | Specific Gravity | Melting Point (degree Celsius) | Change in temperature % per degree Celsius | Change in resistance per degree Celsius | |
| Copper | 1 | 0.304 | 103 | 31.4 | 8.89 | 1083 | 61.1 | 0.0039 |
| Aluminum | 1.64 | 0.092 | 169 | 15.6 | 2.7 | 660 | 28.7 | 0.0039 |
| Silver | 0.94 | 0.359 | 97 | 34.9 | 10.5 | 961 | 18.8 | 0.0038 |
| Gold | 1.42 | 0.661 | 146 | 96.6 | 19.32 | 1063 | 14.3 | 0.0034 |
| Tin | 0.67 | 0.25 | 691 | 172.7 | 7.3 | 232 | 26.9 | 0.0042 |
| Relative to copper | ||||||||
| Copper | 100% | 100% | 100% | 100% | 100% | 100% | 100% | 100% |
| Aluminium | 164% | 30% | 164% | 50% | 30% | 61% | 178% | 99% |
| Silver | 94% | 118% | 94% | 111% | 118% | 89% | 117% | 97% |
| Gold | 142% | 217% | 142% | 308% | 217% | 98% | 89% | 87% |
| Tin | 670% | 82% | 670% | 550% | 82% | 21% | 167% | 10% |
Why does copper wire need plating?
Plating maximizes and customizes the properties of a wire conductor.
Here are the reasons why copper wire needs plating;
Enhance copper wire’s weldability and oxidation resistance.
Oxidation of copper when exposed to air does the following;
- Increases resistance
- Reduces conductivity
The plated copper wire prevents redox reactions, which;
- Improves the wire’s weldability
- Improves the wire’s electrical conductivity
- increases heat dissipation.
Increases the obstacle avoidance between the wire and the insulation layer
You can use tinned copper wire as;
- Outer shield braids
- Conductive cores
Therefore, copper wires need plating because it;
- Improves weldability of copper wires;
- Prevents the conductive core of the rubber-insulated cable from sticking.
Increase the solderability of metal objects.
Coating copper wires increases the metal’s solderability, which makes soldering to another surface easier.
Wire plating options: Tin vs. nickel vs. silver vs. gold
Here is a comparison of various wire plating options;
| Wire plating option | Description |
| Tin | Silver has high conductivity, making it ideal for high-frequency applications. It also; Reduces the resistance of plated wiresImproves chemical resistanceIncreases high-temperature performanceHas excellent solderability. |
| Silver | Gold is a common plating choice for the following; ARINC coax contactsBrass connector pinsParts of some other connectors Gold has excellent corrosion resistance properties and high conductivity. Also, you can easily solder it. However, it is an expensive wire plating option. |
| Nickel | The properties of nickel include; High resistance to corrosion and high temperatures, relatively low conductivity. Therefore, plating the wire will increase its resistance. |
| Gold | Gold is a common plating choice for the following;ARINC coax contactsBrass connector pinsParts of some other connectors Gold has excellent corrosion resistance properties and high conductivity. Also, you can easily solder it. However, it is an expensive wire plating option. |
How does the plating process work?
Manufacturers create tin-plated objects using the following metal finishing methods;
Hot-dip tinning method
Hot-dip tinning involves heating and melting solid tin.
Measures
Immerse copper in molten (heated) tin solution
Advantages and disadvantages
The hot-dip tinning method has the following advantages;
- Controllable, low cost, low scrap rate
- Little environmental pollution
- Excellent reflectivity and appears more beautiful
- Excellent welding performance
- The process is simple, with a short delivery time
Its disadvantages include;
- Limited storage time
- Poorer adhesion and continuity
- The tin layer is difficult to control
Application consideration
Hot-dip plating is an ideal application method if;
- The wire gauge is relatively small (0.15 to 0.32 mm)
- You require a thicker coating
Plating tinning method
This method uses the electrolysis principle.
Measures
You should use negative and positive electrodes as power media.
Advantages and disadvantages
Wire plating tinning method has the following advantages;
- The surface is clean and smooth, with no tin powder
- High roundness and consistent wire diameter
- Long storage time
- Stable in layer
- Controllable tin layer’s thickness
- Excellent electrical and welding performance
- The coating is uniform, with exceptional concentricity and eccentricity
Its disadvantages include;
- Environmental pollution
- Complicated electroplating operation and process
- Require high chemical technology
- High upfront investment costs
Application consideration
Electroplating is recommended for electroplating multiple thin copper wires.
Consideration for choosing a wire tinning machine
Factors to consider while choosing a wire tinning machine include;
Production speed
The production speed of a wire tinning machine depends on the following;
- The size of the tinning wire
- The type of the tinning wire
Safety
Your wire tinning machine should have the following safety features;
- Safety guards
- Emergency buttons
These features prevent possible accidents and damage to the wires.
Repair and maintenance of the wire tinning machine
The best wire tinning machine should be;
- Easy to repair
- Easy to maintain
By considering this factor, you will choose a machine;
- With an extended lifespan
- That ensures consistent output
Type of metal used for tinning
The common types of metals used for tinning are;
- Silver
- Copper
- Tin, etc.
Therefore, your machine should be adjustable according to the metal used.
Type of tinning process
Wire tinning machines are designed for unique wire tinning methods.
For instance,
- Electroplating tinning machines generate consistent and even coating layers.
- Hot-dip tinning machines are slower and can damage the wires
Conclusion
Coating wire conductors are essential in wiring projects for high-quality transition.
At Cloom Tech, we provide a wide range of wire harness solutions.
Contact us today to request a quote.