Mainframe manufacturers and the telecommunications industry are primary users of backplanes on which are mounted a substantial number of daughter cards carrying electronic components thereon. The backplane provides conductive traces or circuits to electrically interconnect the components on the several cards and to provide access to other backplanes and outside electric gear. The predominate method of mounting the cards on the backplane and electrically interconnecting the circuits (and hence the components) is by means of card edge connectors. Such connectors include a card receiving slot, i.e. a card slot, with conductive contact members having spring arms or cantilever beams positioned along one or both sides of the slot to engage traces on the card inserted therein and further having depending leads electrically engaging the backplane. In some connectors, the arms or beams are preloaded into the slot and the cards are frictionally inserted thereinto. Provided the number of contact members are not too great, the force required to insert the card is acceptable. However, cards having a large number of traces require connectors wherein the large number of contact members prohibit frictional insertion. In these cases, connectors having camming mechanisms which either cam the arms or beams out of the slot prior to inserting the card, e.g. as disclosed in U.S. Pat. No. 3,793,609, or into the slot after insertion of the card, e.g. as disclosed in U.S. Pat. No. 4,586,772, are used.
In each type connector, the method of obtaining the normal force, i.e. the force exerted on the conductive pads or traces on the card by the arms or beams, predetermines the type of cantilever beam or spring arm to be used therein. For example, in the first type, the spring arms must be resilient enough so that they can be moved out of the slot with acceptable levels of force applied to the camming mechanism and still have sufficient inherent spring force to bear against the card and obtain good electrical contact therewith. In the second type of ZIF connector, the spring arms or beams must be made of stiffer material to stand up under the biasing forces continually exerted against them by the camming mechanism. In this type connector, a higher normal force may be obtained which is required in some operational uses. However, a greater force is required to actuate the camming mechanism which could lead to breakage if the components are not strong enough to withstand the forces.
It is now proposed to provide a ZIF card edge connector wherein the spring arms on the contact members are hinged and have a large moment arm which provides a mechanical advantage so that lower forces will actuate the camming mechanism and a high normal force will still be obtained.