Use of Anisotropically Conductive Elastomers in High Density Separable Connectors.

This paper describes tests performed on a simulated high density, separable connector which uses a flex circuit backed by a compliant elastomer as a substrate for one set of contacts and a rigid backplane as a substrate for the other set. A 10-mil thick sheet of elastomeric conductive polymer interconnect (ECPI) material was placed between the pair of contact arrays. The ECPI material is an anisotropically conductive elastomer that conducts in the Z direction only. Three types of backplane were used in the tests: a flat backplane, a backplane with a bow of 12 mils across a distance of 3 inches, and a backplane with a large, randomly selected portion of the contacts raised 1.5 mils above the other contacts. For all three backplanes, the combination of the elastomer backed flex circuit and the ECPI material was able to accommodate the lack of coplanarity of the contact arrays. In all cases it was possible with an applied load of 56 g/contact or less to achieve a contact resistance distribution with a mean of less than 20 milliohms and a 3- sigma limit of 50 milliohms. By comparison, elastomer backed flex circuits which made direct metal-to-metal contact with the backplanes required loads greater than 140 g/contact to achieve satisfactory contact resistances. The ECPI contacts were also found to be less sensitive to particulate contamination than the direct metal-to-metal contacts. The paper also discusses the properties and other advantages of the elastomer-backed flex/ECPI combination as well as some of the problems to be overcome in the design of high density, separable connectors incorporating this approach.