Although generally a low cost item, switches can have a major impact on the function and reliability of any product. General manager of Knitter-switch UK, Terry Moss, explains why switches are more than just a commodity Although commonly perceived as a low-cost, high-volume commodity product, buying the correct switch can have a major impact on the success and reliability of an end product. Often referred to as the man-machine interface, the humble switch is the main way an end user communicates with a product or system. The initial tactile response of the switch is seen as a mark of the products overall quality and can be a major purchasing influence.
Control switches require different attributes depending on the application, with low mechanical noise for broadcast and pro-audio applications, resistance to electrostatic discharge for medical equipment, positive action or illumination in noisy industrial environments, robust design for vandal resistance, locking actions for security, multi-function joysticks and TACT switches for system control and menu-selection. Any worthwhile switch supplier should also offer a range of button and bezel options for aesthetic and ergonomic panel design.
At PCB level, programming and set-up functions are frequently carried out by DIL/DIP switches which can be incorporated into the SMT manufacturing process. Rotary coded switches are becoming increasingly popular for programming functions and as a replacement for analogue components as they can be software controlled to offer multiple control functions.
The unseen element of any switch is its reliability. Once a product becomes a commodity, there is a tendency to buy on price only. An important factor in any purchasing decision, however, should be the life expectancy of the end product and to ensure all components, including switches, are fit for purpose. Although generally a low cost item, the materials used in a switch can have a major impact on the function and reliability of any product. The body material should be stable for both operating and manufacturing environments and contact materials able to function reliably for the anticipated life of the end product as well as being the correct choice for the signals being controlled.
The relationship between customer and switch supplier is evolving. Not only are more integrated switching solutions being sought, but the current economic environment has changed the supply chain. Distributors have reduced stock levels so that switch manufacturers have to provide shorter lead times for smaller orders. Given that most high volume switch manufacture is now carried out in Asia, this is not ideal. Smart manufacturers are increasing their own stock levels and improving their logistics to be better able to support customers and building more transparent relationships with customers.
One aspect of this is the increase in demand for bespoke membrane and keypad switching solutions. Integrating control and programming functions into a custom solution can address system design, aesthetics, or environmental concerns such as water resistance. It may even improve high volume manufacturability by integrating switching functions into one pre-assembled component. Membrane keypads are the most common solution to this requirement but rubber and emerging dual-technology keypads offer alternatives with added environmental, size and assembly advantages.
In essence, before selecting the switch, make sure you select the correct switch supplier. A buyer’s checklist should include: experienced, local, dedicated design, sales and support team; stock holding; global logistics; flexible delivery options, including ship-to-stock and prepared for SMT manufacturing; wide availability through distribution; and responsiveness to changes in market, environmental and technical standards.
