Combinning all the benifits of semiconductor switches and conventional electromechanical relays in an innovative component, Siemens silicon micro relay is implemented in MEMS(micro electromechanical systems)
Over the years, innovations and improvements have reduced the volume and footprints of conventional electromechanical relays by up to 50%. Progressive miniaturisation and continuing low costs explain why electromechanical relays, despite prophecies of their demise, have not only held their own against semiconductor switches, but even continue to enjoy rising sales. This trend can be observed both in telecom/ signal relays and in power relays for industrial and automotive electronics.
Miniaturisation does, however, affect load and control specifics. Here technical specifications are tending to become more stringent than relaxed. Telecom/signal relays in particular are today being pushed to their physical limits in terms of coil wire thickness, size and precision of injection mouldings, or complexity of production lines. Launching a new product mix at the right time and competitive prices is becoming harder than ever. But thanks to more sophisticated designs and innovative engineering, this marketing challenge is by no means as daunting as it may seem.
The idea behind the silicon micro relay was to implement a new component based entirely on MEMS technology. The result combines the benefits of semiconductor switches and conventional electromechanical relays. The silicon micro relay is not primarily targeted at the telecommunications market, but suitable for a wide range of applications.
No coils, no current
It soon became clear that the mode of actuation would be a key design parameter of the silicon micro relay. At an early stage, Siemens Electromechanical Components (now Tyco Electronics EC) began research into alternatives to conventional electromechanical armatures that would reconcile the demand for miniaturisation with the needs for high performance and economical production. To make a quantum leap in both control and miniaturisation, alternative designs were analysed at an early stage for feasibility and viability. In the end, the advantages of moving wedge technology won the day.
The tiny parts of the silicon micro relay are etched out of a silicon substrate. Its silicon spring leaf, only 10 µm thick, is electrostatically actuated without any current flowing. This electrostatic design without coils or current has an impressively balanced characteristic.
Housed in a standard DSO-F 8 IC package for surface mounting with a footprint of only 7 x 7 mm (twin NOC version), the silicon micro relay meets demands for miniaturisation, automated assembly and tight packing, also satisfying tough technical requirements. Fabrication in MEMS technology - which mainly utilises semiconductor processes - allows multiple switches to be manufactured in a single package and additional logic elements integrated.
Enormous growth potential
In solutions implemented exclusively with semiconductor switches or electro- mechanical relays, users are often confronted with situations in which using the other type of component is out of the question but technical compromises have to be accepted. Here the innovative silicon micro relay offers the best of both worlds, combining the standard IC packaging, compact dimensions and low operate power consumption of semiconductors with the full electrical isolation, high dielectric strength and low contact resistance of relays. Many customers can thus improve the technical performance of their products or even devise entirely new approaches.
The silicon micro relay is of particular interest in all applications requiring:
* full electrical isolation.
* linear transfer characteristic.
* low and stable contact resistance.
* extremely short switching times.
* low operate power consumption.
* standard IC packages.
* multiple switches in one package.
With these features and the technical data listed in Table 1, the silicon micro relay opens up new applications in diverse fields such as:
* automotive electronics.
* consumer electronics.
* medical engineering.
* instrumentation and control, including ATE (automated test equipment).
* security systems.
* telecommunications.
In smallsignal switching components with electrical isolation, the global market share of the silicon micro relay should be on a par with that of photo MOS switches within a few years. Most applications will be found in industrial electronics, although high growth rates are expected in the automotive, data and communications sectors as well.
Flexible
The silicon micro relay is an innovative component that does away with compromises in a host of applications, freeing users from the dilemma of pure semiconductor or electromechanical solutions. Instead, it combines the best of both worlds and enlarges the scope for product improvement. An RF version IS being developed that will also widen horizons in instrumentation and control, consumer electronics and telecommunications.
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