Today’s densely packaged portable and handheld components often require creative packaging methods. In general, designers are required to increase the performance and reliability of the final product while reducing the size, weight and cost of these products. Of course, all of these have to be achieved at the same time, and achieving these goals depends heavily on connectors that offer high operating speed, low resistance, fine-pitch mating features, and surface-mount capability.
One possible solution to this long-standing design problem is the use of elastic connectors. This connector helps meet the size constraints of portable products, eliminates hand soldering of the connector, and reduces production costs.
As electrical products become smaller and more capable, using traditional connection methods (solder connections, standard PCB to PCB) becomes more and more cumbersome and impossible to achieve. Soldered connections require flux cleaning, limit the options for metallization of the pads, and remove components for upgrades or failures that are impractical compared to elastomeric connectors.
As the pad spacing gets smaller, the use of standard printed boards for printed board connections is severely limited and increasingly costly, as they usually involve the soldering of two printed boards, plus the addition of related installation costs. Additionally, their easily damaged metal prongs limit the number of insertions. Elastomeric connectors solve these problems and are therefore unparalleled preferred connectors in the connection of display glass substrates to printed boards, printed boards to printed boards, or flexible circuits to printed boards.
Resilient connectors are much smaller than standard connectors, requiring minimal height and board space in a compact design. They also allow for high contact area densities and do not require soldering, thus providing fast and effortless surface mount termination. Customization is easy to implement, and there are no strict cost constraints. Elastomeric connectors require zero insertion force and are easy to install and replace, simplifying repairs and upgrades.
Flexible connectors can accommodate analog or digital signals with high efficiency at high signal speeds and minimal signal distortion at high frequencies. They provide high-density pitch contacts with excellent contact integrity. Generally speaking, elastic connectors can handle up to 1A of current. If a larger load current is required, the number of contacts can be increased to distribute the current over one or more printed board contact areas.
As far as ambient conditions are concerned, elastic connectors can work between -55°C and 125°C. Since this connector is made of silicone rubber, it exhibits extremely good performance when subjected to shock or vibration tests.
Designs that were constrained in the past can now be implemented because of the small size of the elastic connector, which saves space within the design. Also, their mounting position is not very critical, and they can be used as special mounts, offering a variety of different mounting options.
When selecting the appropriate elastomeric connector, consider the physical and electrical design factors of the connector application. Generally speaking, there are two basic types of elastomeric connectors: those that use metal-filled silicon-copper rubber (typically carbon and silver) and those that use thin metal strips embedded in the silicone rubber. Silicone rubber has 4 functions. First, the metal-filled silicone forms a conductive channel. Second, the rubber acts as an insulator and generally holds the conduction in place. Third, it deflects during installation, and this deflection maintains surface contact in the connection. Finally, its elasticity keeps the conductive surface in contact with the mating surface.
Silicone-copper rubber is used in elastomeric connectors because silicon-copper rubber does not become soft, brittle, or crack like organic rubber. In addition, it will not be permanently deformed by compression, will not be affected by aging, will not produce corrosive chemicals, and the silicone rubber will not degrade when exposed to this UV radiation, oxygen, ozone or moisture . At temperatures as low as -55°C, it can generally still bend freely and can withstand high temperatures up to 175°C. Its electrical properties remain constant under aging or changing environmental conditions. Even soaked with water, its resistivity still exceeds 1012Ω-cm. In the usable temperature range, its dielectric constant is about 2.7 when the frequency reaches gigahertz.
The most commonly used elastomeric connectors utilize alternating layers of conductive and non-conductive silicone rubber (up to 500 layers per inch) for electrical connection.
Another kind of elastic connector is “metal on elastomer” or MOE type connector, which is formed by making thin metal conductors on the surface of the silicone rubber surface layer. Alternatively, the conductors can be embedded in silicone rubber to form a matrix whose contact resistance is determined by the number of conductor columns, the height of the connector, and the width of the substrate contact area. Gold is used when the highest reliability and lowest resistance is required. Nickel can be used as an inexpensive alternative when higher resistances can be tolerated, but the environmental conditions are not very demanding. In fact, it is this metal-containing elastic connector that has opened the door to mobile computing over the past few decades.