Elastomeric Connectors

IR (Non-Conductive ) Type Connectors

Handling Elastomeric Connectors

When handling connectors, always wear suitable gloves or use forceps. Human hands should never handle the conductive areas of elastomeric connectors because the oils and contaminants inherent in the human body can cause contact problems after the product is assembled. Do not use cotton gloves as the fibers in cotton may become dislodged and attached to the surfaces of the connectors. When feasible, keep the work area free of dust and other airborne particles. Those handing the connectors should wear hairnets or caps to avoid contamination.

Custom Elastomeric Connectors

Tooling charges may apply if “L” connectors and other custom designed connectors are produced.  If your elastomeric connector is not available and/or has unique features that are not in a standard connector, please consult with Top Bound USA’s Engineering Department.  Connectors can be molded with a wide variety of material colors to distinguish different pitches, styles, durometers, and dimensions.  Standard  carbon connectors are black and white, while standard silver connectors are white and beige.

General Information

The connector cost is in direct proportion to the amount of conductive material it contains.  Connectors generally require some type of bezel to aid in assembly and to eliminate alignment problems.  Handling with human hands should be somewhat limited, as oils and contaminants may cause problems after assembly.  Segmented LCD displays generally require 3 to 4 conductors per pad while graphic displays may require more conductors. Non-conductive rubber is available in a variety of colors to distinguish different Durometer, dimensions, and types of connectors.

Elastomeric Connector Design Guidelines

Generally, all elastomeric connectors are custom made (tooling charges do not apply).  The following are some design considerations when determining the dimensions and material for the connector.

HEIGHT (H) is a crucial dimension for determining the correct amount of compression needed for reliable connections.  To obtain the correct amount of height for the connector, first calculate the total distance between the two mating devices after assembly.  Add 10 to 15 percent to the distance calculated between the two mating devices.  Top Bound does not recommend compressing the connector more than 1.0 mm.
Note:  Over compressing the connector may warp the assembly or buckle the connector. 

WIDTH (W) is determined by deciding how much of the width on the leads needs to be covered per application.  In an ideal application, the width should have a height to width ratio of one to one.  If the connector height to width ratio becomes too large, the connector may buckle.  The buckling in the connectors will increase the resistance and if the buckling is too severe, the contact can be lost completely. 

Width (w1)  is the conductive material width of each connector.  The cost and hardness of the connector is directly related to its overall size of the conductive material.

LENGTH (L) is usually the same as the length of the matting device.  However, the length is very important when the connector is being fitted into some type of plastic holder / retainer.

PITCH (P) is determined by first finding the pitch of the mating device (i.e. LCD or PCB).  It is recommended to use a minimum ratio of three to one, connector pitch to mating device pitch.  To minimize costs, select one of the standard pitches available on the tables.  If your calculated pitch is not standard, then select the next smaller size.  For example, if your mating device pitch is 0.60 mm you will need a connector pitch of 0.20 mm.  Thus, it would be cost effective to select a standard connector pitch of 0.18 mm.  The pitch should also be as wide (further apart) as possible to keep costs to a minimum.

Conductive material in elastomeric connectors is in alternating layers of the substrate.  Each conductive layer has silicone rubber impregnated with metal powder.  Silicone rubber is the preferred rubber because of its wide operating temperature range, low compression set, and long service life in harsh environments.  The amount of conductivity depends on the type of metal powder the matrix contains.  Large conductive layers will increase the resistance and cost.  Connectors utilizing carbon conductors offer an oxidation free connection at a low cost.  Silver conductors offer a low contact resistance and can handle higher current than carbon conductors.  The cost of a connector is directly linked to the amount of conductive material that the matrix contains.  Silver conductors are more expensive than carbon conductors.  More information about the physical and electrical advantages for each conductor can be found on the following pages. 

Bezels or Holders are required when elastomeric connectors need some type of housing to facilitate an assembly and eliminate alignment problems. During assembly, connectors can be over-compressed by accident.  This over-compression can be catastrophic in some applications by destroying the LCD and/or buckling the connector causing a loss in contact with the leads.  A bezel can prevent over-compression and ensure a proper contact is made on every connection.  If the bezel is made of a conductive material, then side insulators or side insulator coating is recommended to shield the connector.

T Type/T2 Type Connectors

T TYPE Uses rubber conductors and insulators in alternating layers.  The conductive rubber is impregnated with carbon to allow the current to flow through the layer. This design ensures more than one conductor is always contacting the electrode surface.

T2 TYPE Basically a T type with added silk screened ink on the sides for some insulation protection.

TS Type Connectors

TS TYPE Supported on both sides by soft rubber, non-conductive insulating materials.  This self-supporting connector has soft outside insulators that aid in stability and protect the conductive layers from the environment.  Suitable for large LCD displays.	TS-1 TYPE Basically a TS type that has silicone insulation on one side only.
TS-D TYPE A TS connector with an extra layer of silicone insulation in the center to allow for contacts with multiple rows of electrodes on PCB’s and LCD’s.

TG Type Connectors

TG TYPE Supported on both sides by a sponge layer.  This special sponge layer has closed-cell air pockets that allow the connector to absorb more deformation than other similar connectors.  Ssuitable for use with large LCD displays.

TG-1 TYPE A TG connector with the sponge insulation on one side only.

IR Type Connectors

IR TYPE  ( Non-Conductive ) Can be used without a retainer to support connections between a PCB  and  flat-panel displays. They can be molded to any size and color.  Durometer and physical properties can be matched with the application’s connectors to ensure proper compression, volume resistivity, breakdown voltage, and insulation resistance are the same as the connectors.  All tolerances are equal to or tighter than the application connector’s tolerances.

Connector Miscellaneous Charts

Temperature Range

Reliability Test