International Electrotechnical Commission

Basic Environmental Testing Procedures Part 2: Tests Guidance to Test Kd: Hydrogen Sulphide Test for Contacts and Connections - Edition 1.0
 N 60068-2-46

Annotation

Object and scope of the test

Types of contacts und connections

As this test is specifically intended for certain types of contacts and connections (other than those of the welded or soldered type), a short description of these types of contacts and connections is considered to be useful.

Contacts and connections may be divided into two types and could be described as permanent or temporary. In both cases, metal surfaces are held together by an external force.

In the case of permanent connections, the force is very great and will usually cause permanent deformation of the metals and it is possible that a form of local welding takes place. Such connections are not intended to be made and broken during their lifetime. Examples of permanent connections are crimp and wrap joints.

With temporary connections, the force holding the metals in contact is by comparison light and they are of course designed to be made and broken possibly very many times during their lifetime. Examples of temporary connections are : connectors, switches and relays. In temporary connections the areas of metal which make contact with each other are in some cases referred to as contacts.

The contacts or contact areas in temporary connections will be made of various metals according to duty and application. Most metals-with the exception of precious metals-suffer from atmospheric corrosion. When contact materials corrode, contact resistance increases. The extensive use of precious metal contacts would be costly, so it is common in many applications to use precious metal alloys or coatings of precious metal or alloys over base metals for contact materials.