Surface-mount sliding-contact micro switch

August 29, 2013 // By Graham Prophet
Alps Electric has developed the “SPVQC Series”, for use in, for example, vehicles equipped with electric parking brakes (EPB). Such devices have to achieve a high degree of safety and methods for system backup, such as the duplication of circuits, are generally incorporated into the mechanism as a fail-safe measure.

Until now, backup in EPBs has been achieved using two micro switches, but this has led to problems such as the on/off timing of the switches going out of sync during low-speed operation. Moreover, when employing a butt contact structure, and with low currents, contact faults have occurred due to ingress of particulates or other matter.

In addition, surface mount components are increasingly used for LEDs and other components around the EPB device, requiring that micro switches are capable of undergoing reflow soldering.

The “SPVQC Series” surface mount two-pole sliding contact micro switch extends the company’s existing SPVQ9 Series which was the first such switch in the industry to employ a two-circuit sliding contact structure and has captured more than a 50% share of the European market. Retaining the same structure as the existing product, the SPVQC Series surface mount switch ensures high contact reliability with strong resistance to particulates, as well as to vibrations and impact. Alps also applied its mechanical engineering and precision processing technologies to revise the design of the internal mechanism, thereby reducing the product’s width by 1mm.

The SPVQC Series employs a double-sided sliding contact structure consisting of a moving contact that clamps a fixed contact from both sides. This enables application of a constant pressure on the contact at all stages of the switch operation from the moment the pressing begins, through on/off switching, to the fully depressed position. Combined with a snap action design, the structure constantly maintains a stable contact regardless of the control position and speed, making the SPVQC Series a highly reliable control switch. It measures 15.4 × 7.4 × 7.5 mm, max rating is 50 mA at 18 VDC, min rating is 50 μA at 5 VDC: contact resistance (initial) is 75 mΩ max. and after lifetime is 200 mΩ max. Operating life (with load) is 300,000 cycles of 50 mA, 18 VDC.

The timing of switching between the