The Contact Clip, the Heart of the Mill-Max Receptacle
Inside every Mill-Max receptacle is a contact clip. A contact clip is a conductive, multi-finger, progressive die stamping. The contact fingers, also referred to as tines, are the stamped beams which open, envelop, apply force to the mated pin. The finger tips are typically coined to maximize the finger tip surface area. These fingers allow the contact clip to engage, score and hold the mated pin making an electrical and gas tight connection at 3, 4 or 6 points of contact, depending on the selected contact.
Mill-Max currently offers 36 styles of contacts. This extensive family of contacts will accept round pins ranging from .008" to .102" diameter, as well as rectangular component leads and square wraposts, where the effective diameter is taken as the diagonal dimension of the lead. Receptacles with contact clips inserted in them are capable of 1,000 minimum insertion/extraction cycles for a broad range of applications. Mating pin size, shape and finish, along with application specific variables, will affect the life of a contact.
Many contacts are interchangeable within a given receptacle shell. Standard receptacles found in the catalog and on the website can be easily assembled with alternate contacts to suit special applications, for example: low insertion force or high operating temperature. A convenient contact selector chart has been organized by alternate contact groupings to help assist you in choosing the right contact for your application.
The standard material of contact clips is beryllium copper 172 which is suitable for applications operating in a constant temperature environment under 150° C. For applications operating in a temperature over 150° C we offer select clips in beryllium nickel. Both materials are heat treated to achieve optimal spring characteristics & durability.
The current rating of a contact clip is a function of its material thickness and pin engagement surface area. The current rating of each Mill-Max contact is listed in the rightmost column, labeled "Current Rating", found on page 248 of the Mill-Max catalog. Note, this current rating (for a 10° C temperature rise above ambient) is conservative since it rates an individual pin/receptacle pair in the free air. For all practical applications, the current rating will be higher because of the heat sinking ability of wires and circuit traces attached to the pin and receptacles and will depend on the specific application.
For more information on contact range, and proper design of pin length and diameter, read on for more.