Choose the Best RJ45 Connector

In the market for RJ45 connectors, there is a wide variety of options available, including full copper, pure copper, oxygen-free copper, and various thicknesses of gold-plated connectors. So, which type of RJ45 connector is the most suitable and how to choose the best RJ45 connector?

 

1. All types of RJ45 Connector pins in the market::

 

1.1 Oxygen-free copper/pure copper pin connectors.

Some manufacturers specify using oxygen-free copper or pure copper for the pins in their RJ45 connectors.

Oxygen-free copper is known for having lower electrical resistance and higher conductivity. When transmitting signals, its insertion loss is relatively low. The contact resistance of oxygen-free copper or pure copper pins is also low. Additionally, since the conductors of network cables are made of oxygen-free copper, the impedance mismatch is reduced. So, many manufacturers use oxygen-free copper or pure copper for the pins in RJ45 connectors. However, oxygen-free copper or pure copper is relatively soft and difficult to pierce the PE sheath and make contact with the conductor. As a result, RJ45 connectors with oxygen-free copper or pure copper pins often suffer from poor contact, high return loss, or excessive insertion loss.

 

1.2 Full copper pin connectors without nickel plating.

Full copper connectors are also common and aren't attracted by magnets. However, these unplated pins are prone to oxidation and blackening when exposed to air for a long time. This is why you often see blackened contact surfaces on RJ45 connectors. In a 24-hour salt spray test (a common method to test corrosion resistance), they appear to deteriorate (turning green or black).

(The left image shows a nickel-plated pin, and the right image shows an unplated pin. After a 24-hour salt spray test, it can be seen that the full copper pin has started to oxidize and turn black.)

 

1.3  Nickel-plated and gold-plated copper pin connectors.

This type of RJ45 connector is typically made by more reputable companies. Nickel, when exposed to air, undergoes an oxidation-reduction reaction to form nickel oxide, which prevents further oxidation of the nickel. Therefore, nickel-plated copper pins do not easily oxidize and turn black. Additionally, careful engineers have also found that the exposed surface of the copper pin (the side that contacts the module) is gold-plated. The gold layer mainly prevents the wear of the nickel oxide and nickel layer. Therefore, after 1000 insertion and removal tests, the gold layer on the surface of the nickel-plated and gold-plated RJ45 connector is not completely worn, and the nickel layer remains intact.

This issue has been addressed before. You can refer to the following picture:  normal use after 24-hour salt spray test.

From the image, it can also be seen that after a 24-hour salt spray test, there is no sign of oxidation on the pins, and they remain functional.

After 1000 insertions and removals, another 24-hour salt spray test was conducted.

It can be seen that after 1000 insertions and removals, the surface of the RJ45 connector remains bright. Therefore, under normal circumstances, a nickel-plated and gold-plated copper pin RJ45 connector can be used for five years without any issues.

So, when choosing RJ45 connectors, opt for ones with copper pins that are both nickel-plated and gold-plated.
 

 

2.  Here are some answers to common questions engineers have about RJ45 connectors:

 

1. Some manufacturers say that nickel-plated connectors have higher contact resistance and can cause impedance mismatch.

In the market, some salespeople may say that RJ45 connector pins without nickel plating are due to the higher resistivity of nickel compared to copper, which can cause impedance mismatch in connectors. However, this is unfounded. We know that the characteristic impedance of twisted pair cables (commonly used in Ethernet networks) is 100 ohms, but the allowable error is 15 ohms. The nickel plating layer on RJ45 connectors is usually 50-150 microns. 1 micron = 0.001 mm; 1 micron = 40 U''. The thickness is very small, and the resistance is also very small. The impact on the characteristic impedance of the link is minimal.

 

2. Some RJ45 connectors can be picked up by magnets, but copper should not be attracted by magnets. What is attracted must be iron. Are RJ45 connectors made of iron?

COBTEL's RJ45 connectors use brass pins. However, considering that brass is prone to oxidation and blackening in natural environments, we apply a 150-micron nickel plating treatment to the brass pins. Since nickel itself can be attracted by magnets, this is why the pins of RJ45 connectors can be picked up by magnets. Of course, considering the wear on the nickel plating from insertion and removal, we also apply a gold plating treatment to the contact layer.

So, why can't the pins of another brand's RJ45 connectors be picked up by magnets? First, as the customer told us, the pins are made of copper, which cannot be attracted by magnets. Therefore, it can be confirmed that these pins are copper. However, they have not been covered with nickel plating, so they cannot be attracted. As a result, these RJ45 connectors are more prone to oxidation and blackening in natural environments.

Will nickel plating affect the stability of twisted pair cables?

No, the characteristic impedance of twisted pair cables and both ends of the connectors should generally be maintained around 100 ohms to achieve impedance balance. Of course, the allowable error for characteristic impedance is 15%. This means that characteristic impedance between 85-115 ohms is within the standard. The nickel plating of 150 microns, which is a thickness of 0.15 mm, does not increase the impedance by more than 1 ohm. Therefore, it does not affect the stability of twisted pair cables.