Products

Switches - Overview and Types

Overview
GGI International has several solutions to offer in order to provide an efficient interaction and an effective control of the functions of your membrane keypad/ User Interface Assembly. It is here that we will be talking about the keypad switches. A switch is the component which is situated under a key on the graphic or silicone layer, when actuated it closes the circuit. Basic characteristics like travel, force of actuation and mechanical lifespan, are determined by the type of switch and materials used. Tactile feedback is the "click" felt (and sometimes heard) when a switch is activated. The degree of tactile feedback is a function of the difference between the force of actuation and the necessary force to maintain the switch closed. A high degree of tactile feedback does not necessarily correspond to a high force of actuation. Switches fall into three main categories.

  • TACTILE WITH METAL DOME: Commonly called dome, it exists in several geometrical forms. GGI International uses almost exclusively the four-legged dome for its reliability (round or oblong domes tend to invert permanently). In addition to acting as a switch, the dome plays a part on the level of perception by the user of a membrane keypad. The dome gives the user a feeling of movement under his/her finger when the key is pressed. The tactile feedback from the dome is the confirmation that the user wants to obtain when he/she selects a function on a membrane keypad. This is the signal that the keypad returns to the user which indicates to him/her that he/she actually activated the key correctly. It's now easy to understand why this click is so important and that the dome selection, depending on the desired "click," is a major concern in the design of a tactile membrane keypad. The engineers of GGI International will work with you and help identify the proper dome selection for your required actuation force.
    • Characteristics:
      • Raw material: pressed stainless steel
      • Plating: nickel, silver or gold
      • Typical sizes available: 8, 8.5, 10, 10.5, 12, 12.2, 14, 16 and 20 mm
      • Typical actuation force: from 200 to 400 grams, depending on the type of dome selected
      • Total travel: the distance on which the dome becomes deformed to create contact and close the circuit. It varies from 0.013" to 0.046", depending on the selected dome size.
      • Rebound duration: the time required for the travel to be carried out completely in one direction and then in the other varies according to the selected dome size.
      • Lifespan: Typically from 1 to 5 million actuations
      • Switching voltage: from 1 to 50 VCC
      • Switching capacity: 1 Watt
      • Switching current: from 0.005 to 100 mA DC
      • Working temperature: from -45 °C to +100 °C
      • Storage temperature: from -55 °C to +100 °C
    • Advantages:
      • Large variety of available sizes and actuation forces
      • Excellent tactile effect
      • Audible and tactile feedback
      • Long lifespan
      • Can be used at high temperatures
    • Disadvantages:
      • Requires a rigid surface of actuation in order to provide the expected performance.
      • Can be damaged and cease to function if the membrane keypad is bent during application.
      • Tactile effect is decreased if an excessive layer of raw material is placed on top of it.

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  • NON-TACTILE: Non-tactile switches have no tactile or audible feedback. The closing of the circuit is done directly between the contact of the top circuit and the contact of the bottom circuit. The spacer/adhesive creates the required distance between the two circuits, in order to prevent permanent contact. The force of actuation is not determined by the type of dome, since there is no dome. The spacer thickness and configuration will determine the actuation force.
    • Characteristics:
      • Raw material: polyester and printed conductive ink
      • Size and shape of the keys: varies according to the application
      • Rebound duration and total travel: varies according to the application
      • Lifespan: 5 to 10 million actuations
      • Working temperature: from -40 °C to +85 °C
      • Storage temperature: from -40 °C to +85 °C
    • Advantages:
      • Eliminates having to add mechanical components to the switch
      • Extremely high lifespan
      • Simple and cost-effective
      • Applicable to large-surface keys of different shapes
    • Disadvantages:
      • No tactile feedback
      • Audible feedback must be programmed on the module where the keypad is connected
      • Not recommended if the graphic overlay has embossed keys
  • TACTILE WITH POLYESTER DOME: Polyester dome switches are fabricated by embossing domes in a layer of polyester. Circles of conductive ink are printed under the polyester sheet and will be used as electrical contact for each dome. Each dome will have a silver disk printed on its concave surface. These switches have a travel slightly longer than that of the metal domes. The force of actuation depends on the thickness of the material on the diameter of the dome as well as the height of the embossed dome.
    • Characteristics:
      • Raw material: embossed polyester and printed conductive ink.
      • Diameter, height, rebound duration and total travel: variable, depending on the application.
      • Lifespan: approximately 1 million actuations.
      • Working temperature: from -30 °C to +50 °C
      • Storage temperature: from -30 °C to +60 °C
      • Custom polydomes can also be made to sustain a storage temperature of +85°C but with a life cycle inferior to 250 000 actuations and a very high actuation force.
    • Advantages:
      • Good tactile effect
      • Reasonable lifespan
    • Disadvantage:
      • Very narrow operating temperature range

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