The present invention relates to a connector for insulation displacing termination of ribbon cable having conductors on close centerline spacing and particularly a cable with conductors on 25 mil center.
Connectors for insulation displacing termination of ribbon cable are well known. These generally employ a housing having a mating face, an opposed cable receiving face, and at least two rows of terminal receiving passages extending between said faces. A plurality of stamped and formed metal terminals are received in respective passages, each terminal having major rolled surfaces and sheared edge surfaces, each terminal having a mating portion toward said mating face and a slotted plate toward said cable receiving face.
The slotted plate behaves like two parallel beams. For a given force at a given point on a beam, the deflection is a function of the width, thickness, and properties of the material. As contacts become smaller, these dimensions must be balanced carefully to attain a desired force/deflection ratio. A 10% decrease in beam width can necessitate a 37% increase in material thickness to retain the same force/deflection ratio. Simply using a thicker or stronger material may lead to difficulties in stamping and forming a terminal of the desired configuration. Thus, as the centerline spacing of ribbon cable has decreased, connector design problems have arisen.
A Microminiature D Connector has recently been developed by ITT Cannon Electric for mass terminating ribbon cable with 30 gage wire conductors on 25 mil centers. See Cabourne, Michael K. "Mass Termination of 25 Mil Planar Cable with Micro D Connectors", a paper presented at the 17th Annual Connectors and Interconnection Technology Symposium in Anaheim, Calif. The disclosed connector has slotted plate terminals each with a conductor receiving portion extending above the cable receiving face and a base portion in a respective passage. The conductor receiving portion extends to a pair of insulation piercing points and mutually opposed outer sheared edge surfaces which extend from respective points as diverging straight lines toward the base portion. The base portion likewise has mutually opposed outer sheared edge surfaces which diverge as straight lines, which straight lines are colinear with the outer edge surfaces of the conductor receiving portion. This yields a tapered beam design which provides a normal contact force of about 21/2 pounds on a 30 gage stranded wire received in the conductor receiving portion. However, the outer sheared edge surfaces at the level of wire termination are considerably wider than the centerline spacing of the cable, with result that insulation of neighboring adjacent wires is displaced. Thus, while desired contact force is achieved, the possibility of short circuiting between conductors is introduced.