Review

As with most every other electronics component these days, switches and relays have had to shrink down to fit into smaller and smaller products. Thus, it's no surprise that much of the innovation in this category was due to miniaturization efforts by manufacturers of these devices.

A raft of SMT switches and relays made it to market this year. For example, the DHS Series surface-mount DIP switches from Apem Components (apem.com) are half as large but equal in contact rating (100 mA at 6 Vdc) as standard size units. The terminal pitch of the new DIP switches is 0.050" versus 0.100" for the standard models and other package dimensions are similarly reduced. DHS switches come in 4-, 6-, 8- and 10-position models, with the 8-position switch measuring just 0.468"L x 0.244"W and having an above board height of only 0.087".

Another example is the CJS jumper switch from BCcomponents (bcccomponents.com). This switch is designed to replace traditional jumper pins, reportedly one of the last remaining non-surface-mount components found on pc boards. The SPDT switches measure just 5.4 mm x 2.5 mm x 2.5 mm, have a −40°C to +85°C operating temperature range, and are available with J-hook or gull-wing leads and with or without a neutral detent. The low-profile SPST switches can be mounted and soldered in the same way as other SMT components.

On the relay side, the GRF100 and GRF103 series from Teledyne Relays (teledyne.com) are non-latching, surface-mount electromechanical relays. Designed for RF use, the relays employ a butt-lead mounting scheme and a unique ground shield that insulates and shields each lead. The ground shield also provides a ground interface, said to be responsible for an RF insertion loss of just ±0.1dB. The GRF100 measures 8.51 mm x 8.51 mm x 8.38 mm and weighs 2.55g, while the GRF103 measures 8.51 mm x 8.51 mm x 11.05 mm and weighs 4.5g.

Joysticks were not immune to the miniaturization trend, since they are needed for cell phones, PDAs and the like. An example is the 6.70 mm x 5.45 mm JS-1100 joystick switch from E-Switch (e-switch.com). OEMs can build this device into cell phones, PDAs and other compact, LCD-equipped consumer electronics as a navigating function for directing an on-screen pointer. The five-position switch can make right, left, up, down and select maneuvers. The surface-mount joystick has eight gull-wing terminations and two mechanical lugs to relieve strain on electrical connections.

The first 3V-actuated MEMS switch, the DKM812-3 SPDT RF switch from Dow-Key Microwave (dowkey.com), made its debut this year. The switch manages frequencies up to 6 GHz with a total dc power consumption of less than 3 mW. Maximum input power is 3W with an upper limit for average power of 2W. MEMS technology is said to be responsible for the device's low insertion losses: 0.15 from dc to 1 GHz; 0.25 from 1 to 3 GHz; and 0.3 from 3 to 6 GHz. The switch resides in 7 mm x 7 mm x 1.5 mm JEDEC MO-220 package with the internal switching device in a hermetically sealed CSP.

Though miniaturization was key this year, many other new switches are more normal in size—you can push or toggle them with your finger. In the industrial arena, an example is the Series 04 and 14 switches from EAO Switch (eaoswitch. com). These are available in illuminated pushbutton, indicator and selector versions with stainless steel lenses, protective front rings and bezels. With ratings up to IP 67 and having a wide operating temperature range, the switches are useful for machinery control panels that must resist impact, air pollution and chemical washing. Series 04 and 14 switches can be flush-mounted for a flat-finished interface, making them more resistant to vandalism or harsh treatment, as well as being easier to wipe down.

Switches also saw a host of improvements in illumination, reliability and other factors. An example is the FP01 from NKK Switches (nkk.com). In place of traditional contacts, this switch operates using a photo interrupter, giving it a minimum life span of three million operations. A single phototransistor activates a momentary ON position. The rugged construction and smooth operation of the device allows rapid, repetitive actuation anywhere on the actuator surface.

—Joe Desposito

Outlook

Nearing The End Of The Miniaturization Road
Electromechanical switches and relays indeed did some downsizing this year, but what lies ahead? Given the fact that a switch with metal contacts has to have some size, it's not likely that we'll see models that are much smaller next year. Let's face it, a joystick in a cell phone can only be so small before it becomes impossible to use. And a DIP switch has to be at least big enough that you can switch it from one position to another.

For switches of a more traditional size, we expect to see further innovation, but only in an incremental way. In other words, we expect to see switches with incremental improvements in illumination, ruggedness, packaging and reliability.

—JD