A new genderless connector termination technique and a z-axis contact element combine to enable this fool-proof prototype connector in a plastic housing that requires no shielding.
by Peter Guckenheimer and Sam Sokolik
Connectors were developed to link conductors of varying lengths to carry electricity or to permit equipment to be attached to sources of electricity. Connector contacts are attached to conductor wires by soldering, crimping, and insulation displacement. Both soldering and crimping are labor intensive and have inherent weaknesses. Insulation displacement usually limits the connector to a flat design. In all three techniques, the wires can be unintentionally disconnected from the contacts, disrupting the current. For applications requiring shielding, these three techniques allow extraneous electrical noise that compromise equipment performance.
New termination
A new genderless termination design ensures an unimpeded flow of electricity, a simplified termination process, and reduced assembly costs. This technique for terminating the connection requires a lower skill level than soldering and avoids much of the tooling required for crimping. Furthermore, it is space efficient in keeping with the trend to design more electronics into smaller and smaller packages.
The housing can be made so that both halves are identical, thereby requiring only one mold for either plastic or die-cast-metal housings. This design also has the advantage of permitting thousands of connection and disconnection cycles with repeatable and reliable electrical flow. The intermating surface is easy to wipe clean and can be made highly moisture resistant. Shielding becomes an integral part of the design and is therefore more reliable than present designs permitting plastic housings, again reducing the cost of the connector.
Though this termination method and parts described below can be applied to existing connector housings, use of the same housing for each half of the connector with an integral latch lever or quick thread nut ensures positive pressure to keep mating halves together. This reduces the number of parts to be manufactured, handled, and inventoried (see Fig. 1).
 FIGURE 1. Prototypes of the genderless termination method used pre-existing housings with a z-axis bridging element. |
In brief, the design relies on a cable being cut, and both ends polished and coated to prevent oxidation of the conductors. The prepared cable ends are then secured in a housing, with a z-axis central contactor element, incorporated into one of the connector housings to ensure electrical flow through the connection.
Contactor element
The bridging element, called the z-axis contactor element is the specially designed part that ensures electrical continuity from one side of the cable to the other. It is made of an insulator or plated through a printed circuit board with holes drilled to match the conductor pattern of a specific cable. Within each hole, a conductive material is secured.
The design is a compression spring made of tightly wound wire, which is wound larger at the ends than at the center. This design ensures that the spring remains securely within the insulator. When this compression spring is compressed, the windings touch and create a linear path for the electricity, thereby avoiding coil inductance within micro size capabilities. Other appropriate materials, such as carbon nanotubes, can also be used as conductors.
 FIGURE 2. The principal design of the typical spring contact has end coils 20% to 50% larger in diameter than the spring body. |
Another approach is for the holes to be fitted with CIN::APSE (a solderless z-axis interconnect technology) or Fuzz Buttons (solderless contacts). In some cases, a metal infused elastomeric material can be used as a bridging element. Ultimately, this bridging element can accommodate much smaller wire gauges and is significantly less expensive to assemble and manufacture than the alternatives (see Fig. 2).
Cable preparation
These genderless connections offer three termination solutions, all based on a genderless contact approach. The first solution assumes that the cable is firmly packed and each half retains its circularity. A length of cable is cleaved into the two lengths on either side of the connector. Two cable clamps are inserted 1/8 in. back from the cleaved surface. This allows cables and wires to be polished and coated back to the clamps. The buckles of both clamps serve as keying devices and need to be aligned perfectly to the same color wire to ensure that the electricity flows through the intended wire.
Attached to one side of the cable is the z-axis contactor element that serves as the spring device carrying electricity through the connection point. Each cable will require a unique contactor element that corresponds to the number of wires and specifically sized to the conductor wire gauges. This will then become the standard for the contactor element for that specific cable (see Fig. 3).
The second solution is for cases in which the cable is loosely packed and applying clamps prior to cleaving results in deforming the roundness of the cable. Two indexing disks with an identical hole pattern of the contactor element made of insulating material are required. The cable outer jacket is removed enough to feed wires from each side of the cable through each disk. Each side needs to have the same alignment of wires to ensure that the electricity flows through the identical wire on each side of the connection. Then the contactor element is secured to one side of the cable. Each side of the now round cable end is secured to the cable by potting it in a round form. This potted cylindrical tube is cleaved, polished, and secured in the connector housing. The indexing disks and the contactor disk must be keyed and then aligned and keyed within the connector housing to ensure proper polarization of electrical flow.
This second solution is ideal for rugged applications in which connections require dust and moisture protection. The addition of "O" rings to the housings provides a high level of protection. If the terminated cable is soiled or wet, the operator need only wipe the surface of the termination as no contacts are exposed to bend or break. Therefore, the risk of damage is minimal. Only the springs in the contactor element have some minimal exposure to damage. This contactor element can be easily replaced by extracting it with a small tool (like a dental pick) on the side of the connector where it is affixed (see Fig. 4).
 FIGURE 4. For rugged applications, the addition of "O" rings to the connector housing provides dust and moisture protection. |
In cases where the electricity being transmitted is of low strength (signal), the third solution is to use metal infused elastomeric material as the contactor element. When the two cable halves are compressed, electricity flows through the conductive material while the elastomer material acts as an insulator. The elastomeric material is the z-axis material that only conducts in one axis.
For coaxial and triaxial cables, the contactor element becomes two or three components, or sandwich alignment disks made for shield termination and signal center conductor termination. This solution is especially helpful in cables with multi-coax or multi-triax wires as it permits relatively easy termination in a very small housing.
Each aligned cable end must be polished and coated. It is then secured into the connector housing. Then the contactor element is affixed to one end within the housing. If the application is sensitive to oxidation, the polished wires can be protected with a variety of off-the-shelf solutions and plating methods.
Shielding
In solder and crimp terminations, the shield is disrupted and has to depend on a metal housing to ensure the continuity of the shield. In this design, shielding may be accomplished as an integral part of the z-axis design, thereby improving the integrity of the shielding over existing solutions. If potting is required in a shielded application, it should be done from the front of the termination through the alignment disk and dedicated tooling holes made in the contactor element. In brief, shielding does not rely on a metal connector housing. The cable can be terminated using a plastic connector housing, resulting in a cost savings to the end user.
In summary, this termination method and the use of the contactor element provides the end user with a connection that requires a relatively low skill level, minimal tooling, and is time and cost effective. It results in a connection that is virtually impervious to dirt and moisture. Even if dirt or moisture accumulates on a loose end, it can be wiped clean and the flat surface is then ready for reconnection. It is also very easy to make repairs in the field in the unlikely event that an end is damaged. This provides manufacturers with a lower-cost, lower-skill-level method for terminating electrical connectors.
The plastic connector housing will reduce the connector manufacturing, inventory, and handling costs while providing all the performance of metal connector housings. A cautionary note is in order as this is a new concept with prototypes built by hand. Though the technology exists to execute the design presented here, it will take careful evaluation of the volumes at which a cost-benefit break-even point will be reached to justify implementing this new technology.
PETER GUCKENHEIMER is president and founder and SAM SOKOLIK is director of business development at PG DESIGNS, 3009 Sunridge Dr., Santa Rosa, CA 95409. Tel: (707) 546-1740; email: peterguckenheimer @yahoo.com.
