Today's marketplace sets high demands for fast, accurate, and reliable human-machine interface solutions. It is critical to provide your customers with ease of use, satisfactory tactile response, and rapid functionality when developing your specific application.
Membrane switches are designed to meet a very specific set of criteria depending on the application. Effective membrane switch design requires a good understanding of the application and the ability to communicate what is required for a successful and efficient design.
The purpose of this design guide is to outline the requirements and their role in the membrane switch design process. Using these guidelines will help maximize the quality, reliability, and efficiency of the membrane switch. Cubbison Company is capable of custom membrane switch design assistance to meet all of your requirements.
In general terms there are two types of membrane switches, tactile and non tactile. These can be constructed as a keyboard with or without a graphic overlay. Polyester is the most popular film used in the construction of membrane switches due to its durability and high temperature properties. Cubbison can supply a range of heat stabilized polyester films which offer high stability specification and are designed to be screen printed with conductive silver and/or carbon, graphite and dielectric inks.
Cubbison accepts electronic files in .ai (Adobe Illustrator), .dwg or .dxf (AutoCAD), or other vectored file programs. If you're unsure of whether your art file is acceptable just ask us. Artwork should specify type styles, colors, sizes, any logos or special symbols, etc. If you do not have artwork, Cubbison offers complete membrane switch design services. One of our design engineers will work with you on designing and building a membrane switch custom for your application.
Cubbison offers a range of hard coated and textured polyester films. These films have been designed specifically for the graphic overlay film on membrane switches. Both product ranges are screen printable on the second surface; they are solvent, chemical and scratch resistant on the first surface, and can be embossed giving over 5 million actuations during their life time. ***For further information on this please contact the Cubbison Company.
The Pantone matching system (www.pantone.com) is the most popular for graphic art applications. There are separate matching criteria for opaque and transparent colors. For matching the CMYK 4 color process used in most digital print applications click here.
It is important to remember that matching overlay colors to surrounding components is difficult. For this reason it is advisable to look for contrasting color combinations to avoid mismatched components.
Cubbison can provide either pillow (pad) or rim (perimeter) key tactile designs into polyester or polycarbonate overlays. This process requires a male/ female die set. Overlay embossing dies are manufactured with sophisticated tolerances to allow for material flow. ***Our Cubbison design staff will precision-calculate a die for your application.
Windows are typically transparent or translucent, which are single pigmented or formulated with dyes instead of pigments. A transparent color is optically clear and used to filter backlight displays. The transparent color reduces the "blooming effect" of the display. A translucent color is normally used for diffusing an indicator light or backlighting for printed graphics, such as an instrument cluster that is backlit.
Cubbison offers hard coat films that are ideal for membrane switch overlay applications. These films are polycarbonate and polyester substrates that have been specially treated so that their surfaces can be selectively textured, embossed or printed with UV inks. Available in finishes ranging from glossy clear to textured matte black; hard coat films offer a range of display options. Hard coat films resist scratching and staining from a broad spectrum of foods, household cleaners and aggressive chemicals. For special applications, such as medical equipment, our hard coat films may be embossed or otherwise thermoformed without sacrificing performance characteristics. Cubbison can print inks specifically designed to give a decorative texture effect on first surface polyester or polycarbonate used for membrane overlay applications. Textures may vary from fine to very fine depending on the desired effect. The gloss level may also vary depending on screen mesh and substrate.
• Diameters 6, 8.4, 10 and 12.2mm • Activation forces are available from 110g to 420g • Click ratio 40-80% • Dome travel distances are 0.23 to 0.70mm and heights from 0.30 to 0.80mm • Available with life expectancy up to 5 million activations • Operating conditions are -40 degrees C to +125 degrees C
• Diameter 4 and 5mm • Activation forces are available from 110g to 220g • Click ratio 30-70% • Dome travel 0.15 to 0.17mm given product • Height 0.20 to 0.23mm given product • Available with life expectancy up to 5 million activations • Operating conditions 40 degrees C to +125 degrees C
• Diameter 4 and 5mm • Activation forces from 110g to 220g • Click ratio 30-70% • Travel 0.15 to 0.17mm given product • Heights are .020 to 0.23mm given product • Life expectancy up to 5 million activations • Operating conditions -40 degrees C to +125 degrees C
• ESD, RFI/EMI Our most common types of shielding are printed using either carbon ink or silver ink or by using solid aluminum foil. Carbon is the least expensive printed option. Aluminum foil has certain advantages if a printed top circuit is not specified. ***Our design engineers will help to determine your best shielding solution. • Tail Cubbison can help you to determine the tail length and exit point. It is important to use a tail of the shortest length practical for your design in order to control cost. There are specific parameters for proximity to the keypad area. In some cases a rear entry of the tail may be your best option. • Venting When a switch is deflected there needs to be a small track designed into the switch for the displaced air to move. The tract will connect all of the switch keys so that air can be displaced. Using this design technique allows the switch to remain sealed. • LEDs UltraThin LED's with diffused or water clear lens are available. LED's are bonded to the surface with special silver epoxy adhesives.Dimensions are 3.2 x 1.6 x 0.5mm (mono-color: red, orange, yellow, green, blue, white) Dimensions are 3.2 x 2.5 x 0.5mm (bi-color: red-green, yellow-green, red-yellow) Operating conditions are - 40 degrees C to 85 degrees C • Backing/Subpanels Cubbison can offer aluminum, polycarbonate and acrylic material options for a rigid subpanel. Cubbison can laser fabricate a subpanel to your specifications. It is usually advisable for the subpanel to be slightly smaller than the membrane switch. Conversely the holes and cutouts should be slightly larger than those on the membrane in order to conceal the sub panel.
• 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
• Total travel: the distance on which the dome becomes deformed to create contact and close the circuit
• Voltage: difference of electrical potential between two points of an electrical or electronic circuit, expressed in volts. It measures the potential energy of an electric field to cause an electric current in an electrical conductor. A measure of the pressure under which electricity flows
• Capacitance: The property of a circuit element that allows it to store an electrical charge; A capacitor is an electronic component used for storing charge and energy. The usual capacitor is a pair of plates. When a steady voltage is applied across a capacitor, a charge +Q is stored on one plate while -Q is stored on the opposite plate. The amount of charge is determined by the capacitance C and the voltage difference V applied across the capacitor; Capacitance is measured in farads.
• Electric Current: The flow (movement) of electric charge; Measured in Amperes
• Resistance: ratio of the degree to which an object opposes an electric current through it, measured in Ohms
• Dielectric: non-conducting substance, i.e. an insulator. Although "dielectric" and "insulator" are generally considered synonymous, the term "dielectric" is more often used when considering the effect of alternating electric fields on the substance while "insulator" is more often used when the material is being used to withstand a high electric field
• Dielectric constant: Every material has a dielectric constant. The dielectric constant is the ratio of the permittivity of a substance to the permittivity of free space.
• Permittivity: also called electric permittivity, is a constant of proportionality that exists between electric displacement and electric field intensity. This constant is equal to approximately 8.85 x 10-12 farad per meter (F/m) in free space (a vacuum).
• Dielectric strength: measure of the voltage required to puncture a material, expressed in volts per mil of thickness.
• MTBF: Mean time between failures is the mean (average) time between failures of a system, and is often attributed to the "useful life" of the device i.e. not including 'infant mortality' or 'end of life' if the device is not repairable.
• Optical fiber: A thin glass strand designed for light transmission. A single hair-thin fiber is capable of transmitting trillions of bits per second.
• EMI (electromagnetic interferences): Interference similar to white noise. This interference on a membrane keypad results from the magnetic field produced by various devices near the keypad. The unit of measurement of EMI is the decibel or db. Typical applications: medical, military, aeronautical, telecommunications
• ESD (Electrostatic discharge): Interference caused by a discharge of static electricity. This interference on a membrane keypad results from the discharge caused by a user touching the keypad. The unit of measurement is the kilovolt. Typical applications: various
• RFI (radiofrequency interference): Interference caused by the use of the keypad. This interference is negligible and is seldom taken into account. The unit of measurement of RFI is the decibel.
