In this article, we will discuss bare copper vs. tinned copper.
Electrical cables and wires are designed to carry electrical currents with the help of the conductor.
The properties of the conductor decide the flow of the current.
Apart from the base metal and stranding technique, plating is another way to improve and customize a conductor’s properties, and one such plated conductor is tinned copper.
Why Choose Copper as Your Wire Conductor Metals
In electrical conductors, copper is a standard conductor and is inexpensive as available in high quantity.
Copper wire vs. Aluminum wire
Aluminum is a bit lighter than copper, which makes it more suitable for the aircraft industry.
It weighs around 1/3 that of copper; despite its poor conductivity, its per-pound basis performance is 2:1 as compared to copper.
Despite these benefits, aluminum is not a viable solution in electrical connections because it results in a galvanic reaction with copper/brass fittings and terminals when there is moisture.
As a result, there is corrosion which may result in connection failure due to high resistance and an open circuit.
Changing all the pins, terminations, contacts, and conducting hardware may solve this problem.
However, this solution is not possible physically, and even if you do that, the tendency of aluminum to develop complex oxides can affect the conductivity of the circuit.
Using bimetallic adaptors is a second solution to this problem, but re-wiring a whole building is impractical.
Further, it is tough to solder or plate aluminum for soldering.
So, is there the only legitimate use of aluminum in the aircraft industry? The answer is NO.
Aluminum is used mainly in airborne 6 or larger wire gauges aiming at power applications and not on avionics systems.
The corrosion effects compensate for the high currents in such large conductors.
Copper wire vs. silver wire
Silver is a better conductor than copper but is more expensive.
Thus, manufacturers mostly use silver as a copper coating to enhance skin conductivity and make it corrosion-resistant.
This feature is beneficial at high frequencies when the current stays mainly at the skin of the conductor, and this phenomenon is referred to as the skin effect.
Aluminum wire screwed to an electrical transformer
Why Tin Wires?
Manufacturers and industries use stranded copper wires in PCBs and other devices with the help of a screw-style terminal block.
Tinning helps prevent wire strands from fraying when you connect them to a termination site.
Suppose you push the stranded wires into the screw-type terminal block cage.
The chances are that stranded wires do not get pushed into the cage resulting in a short.
Further, frequent installation and removal of the wire strands at the termination site can make the process more difficult.
However, tinning works as a wonderful solution to this problem. Tinning ensures that all the wires are included in the electrical connection.
During tinning, when you use a soldering iron, the solder melts and fills the voids between the wire strands.
As a result, you get one solid wire you can easily bend and place under screws.
With this, you get a robust electrical connection, and no loose strands come from the terminal screws.
All in all, you can do tinning to hold the stranded wires together.
Also, tinning improves the bare copper wire’s operating temperature range, mechanical strength, and water resistance.
Wire plating options
You must know that tinning does not involve tin but only an electrical grade solder.
| Options | Applications |
| Tin | The low cost and good solder properties make it one of the most common coatings for copper and its alloys. Tin plating also results in resistance to chemicals and corrosion depending upon the copper thickness. Tin also improves the operating temperature range of copper due to its low melting temperature. Apart from this, the low conductivity of tin in comparison to copper creates an intermetallic layer that increases resistance compared to bare copper wire or silver-plated one. |
| Silver | Silver has high conductive properties and thus decreases the plated wire resistance. In high-frequency applications, this property is very advantageous as, due to the skin effect, there is more increased current flow through silver. In addition, silver also improves the wire’s operating temperature range and chemical resistance. Silver has excellent solderable properties, and the high conductivity of silver does not allow its oxidation feature to affect its solderability. Silver plating is advantageous overall, but its cost is sometimes a drawback. |
| Nickel | This hard metal provides excellent resistance to very high temperatures. Nickel plating improves the operating temperature range but depends on the plate’s thickness; however, it is always better than silver’s. It has good resistant properties against corrosion and harsh environmental conditions. As the nickel is hard, you may need to use an activated flux during soldering. Nickel-plated wires need crimp termination, but due to the metal’s hardness, you may need to adjust tools. The low conductivity of the nickel tends to increase the resistance of the wire. |
| Gold | This pricey metal is a standard coating for ARNIC coax connectors, brass connector pins, and other parts. Gold is preferred for plating as it has extreme corrosion-resistant properties, even with high exposure. Additionally, gold is a superb conductor and is easily solderable. |
Bared copper wire
Options for tinning wires:
You can tin the wire either manually or through machines. Whatever way you do, it improves the strength of bare copper wire.
How to tin electrical wire strands by hand?
You must be cautious while soldering as solder iron is very hot and may result in severe burns if handled carelessly.
Always put the soldering iron on a heat-resistant surface during its heating and cooling off.
Work above a heat-resistant platform during soldering and keep it away from any flammable material.
Don’t overheat the wire, as it may melt wire insulation. Please use scraps of the same wire for soldering for better results.
During an electrical project, if you use an existing wire, remember to determine its type before connecting it to new wires.
Cut the wire from one end, and you can quickly know whether the wire is of aluminum or tinned copper.
Prepare what you will need
- Solder iron,
- Sponge,
- Wire stripper,
- Stranded electrical wires.
Picking the suitable solder:
Always use electrical-grade rosin-core solder for tinning stranded copper wires, as it is the best.
This acid-free solder has a flux at the solder core. Do not use solder that uses acid to strip and tin wires, as it will damage the wire and its insulation.
You can use acid-core solders in plumbing applications. You can also use an acid-free solder without a rosin core, but then you must apply flux to the wire for the soldering process.
Preparing the wire
You know that tinning requires a bare copper wire. So, if the wire has insulation, use a wire stripper to strip off ¾ to 1 inch of insulation.
Ensure that the stripped wire length is long enough to be wrapped around the screw terminals but should not be long enough to keep the wire exposed.
Preparing the soldering iron
Plug the soldering iron into the electrical plug and let it heat up.
Wipe off the solder iron tip on the damp sponge to remove any oxidation during the heating up of the iron.
Applying solder to the wire
Let the solder extend out from the spool in a straight line.
You can clamp the wire on a heat-resistant holding surface or in a third-hand tool for convenience.
Now allow it to get closer to contact with the soldering iron tip to create a tiny pool of liquid solder on the iron tip.
As a result, the heat passes from the iron to the wire.
Now, touch the soldering iron tip towards the bottom side of the wire to allow the solder pool to come in contact with the wire.
Apply the solder towards the wire’s top side opposite the iron’s tip. Ensure that solder melts and penetrates in and around wire strands.
Try moving solder and iron together on the bare wire parts, letting the solder melt as you move.
When you are soldering a thin wire, make sure that you touch the solder to the wire briefly so it does not accumulate around it.
Let the wire cool.
Now, allow the solder to cool down, and once cooled, observe the results.
See if there is only a thin coating of the solder all around the wire, and there should not be any glob or heavy pool of solder as it may increase the electrical resistance.
A perfect soldering is one where you can see wire strands under the solder.
If you see any extra solder around the wire, heat the iron again and melt it to wipe it off.
If your application demands, you can bend the tinned wire with the help of nose pliers into a candy-cane shape hook to easily wrap around the terminals on receptacles and switches.
Considerations for choosing a wire tinning machine
Automated wire-tinning machines are used a lot in industry and manufacturing because they can shorten the time to tin the wire, increasing productivity.
Production speed:
Although the production speed largely depends on the size and type of wires, an excellent tinning machine can quickly in a vast number of wires.
Also, it must be capable of tinning wires of different sizes and shapes to get desired results.
Type of tinning process:
There are different types of wire tinning processes, such as electroplating and hot dip tinning, and a good wire tinning machine should perform all these processes.
Every process has its pros and cons. Hot dip tinning is fast but needs high temperatures, while plating is a slow process creating a consistent and uniform metal layer on the wire.
Type of tinning metal:
The wire tinning machine should work with copper, silver, or tin. The use of metal depends on the intended wire use.
Every metal has unique properties, and one must adjust the tinning process according to the metal to achieve optimal results.
Safety:
Wire tinning machines can cause burns or injuries, so they must have emergency stop buttons or safety guards to avoid accidents.
Ensure that only a trained professional handle the device so that the person and the wire remain safe.
Maintenance and repair of the wire tinning machine:
Ensure you choose only those tinning machines requiring lesser maintenance and repair.
Further, the parts should be readily available if a malfunction occurs. With regular and proper care, you can extend the machine’s life and always get excellent and consistent results.
Galvanic baths for electrolytic copper plating
Reasons for tinned copper becoming loose in screw terminals?
The tinned wire may start getting loose right from when the tin flows through the open spaces between copper-stranded wires and converts copper wires and tin into a solid material mass.
After this, there are two situations when tinned wire becomes loose.
During installation in the terminal
When you insert the wire into the terminals and the cage closes and clamps to the wire, the wire block tends to get compressed and changes its shape.
In this process, sometimes, tin breaks and pulls apart the wire strands and creates voids in between. It finally results in the loosening of the wire.
During operation
Even when you securely secure wires in the terminals, the regular operation of the wire can make it lose.
During wiring operation, wires heat up and cool down according to the environmental conditions, and the current flows through such wires.
When there is a rise in wire temperature, it may result in the loosening of the terminations.
The wire and the tin material tend to expand due to high temperatures and take up larger volumes.
As the coefficient of thermal expansion for different metals is different, the expansion of the metal also differs.
Further, as the metal cools down, they shrink and use smaller space.
Due to this continuous expansion and contraction, the tinned wire changes shape and becomes loose.
As a result, the clamp between the pressure plate and the cage becomes unstable.
Conclusion:
Copper soldering requires a flux that may leave some corrosive residues.
Thus, if you want to solder copper, you must use tinned or plated copper, making soldering easier and providing corrosion protection.
Bare copper is suitable for pressure terminations like crimping etc.
It would be best to always consider the application type and the environment before choosing a bare or tinned copper conductor.
If you are still determining which conductor will suit your application, contact Cloom.
We deal in high-quality cable assemblies and wiring harnesses suitable for almost all applications.