Elastomer connectors can be divided into three types: low, moderate and high resistance. In addition, each elastomer connector type offers particular features such as pitch densities, that make them better suited for certain applications. Regardless of which type of connector used, there are a number of universal advantages to elastomer technology including the ability to make closer connections, especially in designs that have chip on glass displays and chip on foil displays.

Typically, high-resistance elastomer connectors have alternating layers of conductive carbon-filled and non-conductive silicone rubber (Figure 1). They make reliable connections by being deflected between aligned contacting surfaces. Generally, high resistance elastomer connectors feature pitch levels of up to 500 conductors per inch, and provide typical contact resistance of 1,000 Ohm with low current capacity of 50 mA. The high resistance and available low temperature elastomer connectors' performance makes them well-suited for military applications, as well as for connecting LCDs to boards.

Figure 1. ZEBRA; Connector interface between two contact areas; such as, PCB to LCD, or PCB to PCB

Moderate resistance elastomer connectors utilize alternating layers of conductive silver filled and non conductive silicone rubber or wires to provide conduction properties (Figure 2). Thin metal wires are embedded with vertical orientation within the silicone rubber, or alternating layers of conductive and non-conductive silicone rubber provide a 0.10 mm pitch. As a result, they provide moderate resistance of 1.0 Ohm and current carrying capacity of up to 600 mA with pitch levels of 240 conductors per inch. The performance of the connectors makes them versatile for most interconnect applications that have current capacity requirements of 1 A including cellular phones, laptop computers and PDAs.

For applications that require even better resistance, the high-pitch elastomer connectors are the choice. They feature contact resistance of 25 mOhm on 0.025" contact pads, as well as current carrying capacity of up to 500 mA per contact wire. These high pitch elastomer connectors are designed with low durometer silicone elastomer core around which a polyamide film, that contains flat metallic gold-plated parallel conductors, is vulcanized. The tips of the metallic conductors are turned upward so that point contact can be affected. The point contact penetrates surface oxides or contaminants that might be present on the surface of the contact pads, thereby assuring reliable electrical connection on two planes.

Other Benefits of Elastomer Connectors

In addition to allowing engineers to fit more on a board, elastomer connectors can provide another benefit to any product design. Any design that must meet stringent shock and vibration requirements will benefit from the elastomer technology because of the silicone rubber.

Figure 2. ZEBRA; elastomeric connectors provide a high-performance interconnect device for applications in the electronic devices market.

Elastomer connectors can also provide improved reliability, especially in applications with tight pitches. Because of the tight pitches, pin and socket connectors must have very thin pins. This makes the pins more vulnerable to bending when inserted to the board. As a result, they are more susceptible to problems during assembly.

Additionally, because elastomer connectors do not need to be soldered, they allow for cost-effective field maintenance. The elimination of soldering has a peripheral benefit as well. Sensitive components on the board are not exposed to high heat, thereby reducing their potential of failure.

Considerations When Using Elastomer Connectors

One vital consideration with elastomer connectors is the spacing between the components being connected, whether it is board-to-board, board-to-LCD or board-to-package. The elastomer "compressibility" makes up for tolerances that are not exact. They also provide a gas tight seal when compressed, thereby guaranteeing the integrity of the connection even in the most hostile of environments.

Another consideration is the non-abrasive quality of most elastomer connectors. While it is a benefit because delicate surfaces will not be damaged, it can also be a detriment if the connecting surfaces are not free of oxidants or surface contaminants. In these cases, the elastomer connector cannot cut through oxidation and connection may be compromised. When properly compressed, however, the elastomer connectors can withstand harsh environments and most severe corrosive applications.

Elastomer connectors are growing in popularity as printed circuit boards continue to shrink because they provide design engineers with the performance and flexibility necessary to meet today's design requirements. Flexible enough to satisfy virtually any application, they provide a viable alternative to traditional pin and socket connectors, especially in applications where tighter pitches and tolerances are required. They are also practical for use in less stringent applications that still demand a high quality connection.