The resistance of a USB socket interface is generally very low and is mainly reflected in the following aspects:

1.Contact Resistance

· The USB standard clearly specifies requirements for contact resistance:

· It must not exceed 30 milliohms (mΩ).

· High-quality USB connectors (such as USB 3.0 or industrial-grade USB) typically have contact resistance even lower than 10 mΩ.

2.Wire and Solder Joint Resistance

· The resistance of the wires in a USB connection is also very small. For example, a one-meter USB cable typically has a wire resistance of about 50–100 mΩ, depending on the thickness of the wire.

· If the soldering process is well executed, the resistance at the solder joints is usually between 1–5 mΩ.

3.Overall Resistance Estimate
From the USB socket through the connecting cable and plug to the device, the total path resistance is typically within 100–200 mΩ. If it exceeds this range, it may affect voltage transmission, especially in high-current scenarios such as USB PD fast charging.