Why manufacturers prefer Brass over Copper in electrical conductors?

Question

I am working on product where we need pogo pins, as copper is better conductor of electricity I was searching for the copper pogo pins. After about a month of searching, it is come to my notice that most of the manufacturers are dealing with pogo pins not of copper but of brass.

Even when I inquired about the pogo pin that suited voltage specification of 250V 15A. The manufacturers insisted on using Brass than copper.

Apart from this I also seen many smart watches which were using pogo pins were using Brass instead of copper?

Is there any basic issue with using copper? What are the scenarios when we should chose Brass over the copper while building electrical connectors?

Answer 1

Pure copper is a very soft metal and while it's ductility is good for wires and other flexible connectors it lacks the mechanical strength required for pins etc. Also brass can have somewhat better corrosion resistance and so may be preferred for mechanical contacts as while pure copper has good conductivity this advantage is lost as soon as you get a layer of surface oxides. This doesn't really matter for something like a PCB where oxidation only affects the outside surface of the tracks but where you have metal to metal contact without something like a soldered joint surface conductivity becomes much more important

Brass is also somewhat easier to manufacture as it casts well and is easy to machine and the huge range of brasses available allow you to tailor its properties to the application to a great extent.

Equally in many connectors the mechanical strength requirements mean that they may have quite a large cross-sectional area in any case, consider a UK 13 A plug, the pins are very chunky compared to the to the wires of equivalent rating.

Answer 2

For pogo pins to work correctly, there must be a good electrical connection across the sliding joint between the tip and base parts of the pin. If the joint develops a high resistance and current flows through the spring inside the pin, that introduces a random and potentially variable amount of inductance into the connection which can affect high frequency signals.

Copper is a very "soft" material after it has been annealed, but any mechanical strain causes significant work hardening in the material which would lead to poorly-defined geometric tolerance and mechanical stiffness across the sliding joint. Brass doesn't have those disadvantages.

To create the required mechanical stiffness, copper pins would need to be thicker than brass, but thin brass pins already have good enough electrical conductivity for the application, so the mechanical disadvantage of using copper are more important than its theoretical electrical advantage.