Membrane switch panels technical expertise & options
Membrane Switch Panel Options
Design counts – not just to make a product aesthetically pleasing, but to increase its functionality, usability and even its durability. That’s why APEM has taken the time to make sure we can support the most sophisticated product designs, graphically and functionally.Overlay Options
Good graphic overlays define the product for the end user. Graphics enable operators to identify the panel’s operational parts, help integrate the look of the interface into the product and protect the internal components from environmental hazards. Choice of overlay materials affect the « feel » of the interface and can reduce glare, protect against yellowing in outdoor locations and provide protection against microbial infections and harsh chemicals. Finally, embossing lets an operator know he’s engaged a switch by providing tactile feedback, or can aide in the use of the interface via finger-guides.Visuals
APEM uses a variety of approaches in our in-house print shop to ensure that our graphic overlay visuals are clean, crisp and durable.We typically print on the backside, 2nd surface, using either
Silk screening, which offers the best color matching possibilities. We can print the conductive layers. Excellent color production is ensured via APEM’s spectro photometer and color mixing software applications. Silk screening prints one spot color at a time, so while the color match is exact, the process is longer than that of digital printing.
APEM silk screening is conducted in humidity and heat controlled environments andjobs are sent direct to the oven without handling. We pay close attention to our processes and control every step to ensure APEM products are delivered free of visual defects such as dust particles.
Digital printing. Digital printing provides unlimited design capabilitiesand facilitates fast turnarounds by eliminating the need for screens and long set up times.
APEM spent 24 months qualifying and testing our new state of the art digital printer before we were satisfied that we could deliver superior graphic overlays to our customers. Taking the time to master our color matching techniques allows us to achieve a very high, 100% color match on 45% of pantone colors and we have developed methods to digitally adjust other colors. Our machine is exceedingly fast.
Learn more about APEM graphic capabilities
Color Systems
APEM can match RAL, Pantone U, NCS or CMYK color standardsMaterials & Coatings
Membrane touch switch construction visuals are overlaid with either polyester (PET) or polycarbonate (PC) film to enhance toughness, durability, processability, aesthetics and to render the switch panel chemically or microbially resistant. Choosing correctly is imperative to product performance. APEM engineers are trained and experienced in our customers’ domains and are ready to assist.Graphic material guidelines: PET and PC possess different properties that make each advantageous in certain applications. PET, the most commonly used, is available
- Textured, to enhance the product « feel » and in
- Crystal or anti-glare, for best display readability
PC is available only in textured.
Coatings:
Specific applications may require coatings and may include embossing or windows, and these requirements will impact the choice of materials:
Chemical resistance is often a critical property. Testing our films yields the following:
Antimicrobial (AM) polyester, incorporated into the polyester textured hard coat during the manufacturing process, provides a dependable and constant protection against bacterial infections, and in some cases, fungal, mold and viruses. AM polyester offers the same key benefits and features of standard polyester: it can be embossed and is chemical-resistant, consistent with low gloss, textured surfaces and compatible with clear windows.
Embossing
APEM knows tactile feedback is often the first option considered by our customers. As important as visuals are, it’s embossing that allows the product operator to first find, and then know they’ve engaged the switch. APEM offers the best embossing in the business and we offer a wide variety of options:- Rim embossing – an elevated perimeter acts as a finger guide.
- Full key or pillow embossing – the entire key is raised
- Dimple embossing – small, dot protrusion(s) can identify the switch (as in Braille markings) or act as guides
- Hot stamping – thermally formed polyester domes that imitate the feel of a snap action metal dome
Windows
Information or display windows can be clear, translucent or colored, textured or anti-glare or even hidden until lit, depending on application requirements.APEM recommends for
Clear Display windows
- Crystal or anti glare PET for best readability. Typically used for LCD displays
- silkscreened visuals and a PET UV coating for applications requiring a textured film
LED windows
- translucent – can be textured and/or tinted
- color translucent – the window presents a “dead front” – information is not visible until the window is backlit
Interchangeable Legends
Interchangeable legends permit the use of a common assembly into which application-specific legends can be introduced either in the factory for cost effective specialization, or after delivery by
- easy on-site insertion: assembly in the factory leaves an opening into which legends can be inserted. While this increases the ease of replacement, it compromises sealability
- insertion on-site by an authorized agent, via a hole in the housing beneath the circuit. This option prevents end-use tampering, but still allows the legend to be changed by authorized personnel without compromising the seal’s integrity.
Circuitry Options
All the overlays in the world aren’t worth much if the switch malfunctions. APEM is as good “under the hood” as we are on overlays. APEM insists on quality components to ensure durability in the harsh environments our customers’ end users operate in.
Switch Options
APEM offers switches actuated via metal or polyester embossed domes or via silver contacts. Each type of actuation has characteristics that may make it more appropriate of a given application:
|
|
Metal domes (snap domes) | Silver contact non tactile | Silver contact with polyester dome (hot embossing) |
| Tactile feedback | Very good
|
No feedback
|
Good |
| Key size
|
10x10, 7x7 and other size as option
|
Limited | Small size for strong feedback |
| Temperature range
|
Very good | Very good | Good |
| Price
|
Medium | Very good
|
Good |
Embedded Components
APEM can embed LEDs, resistors or Surface Mount Technology (SMT)-dependent components such as diodes, transistors or photo sensors to enhance functionality.LEDs: On the front panel or used as a backlight for specific switch features, LEDs can greatly enhance the functionality of a switch. APEM offers a very large selection of LEDs in an array of sizes and colors. Standard colors include: blue, green, red, orange and a bi-color of red/green. Our LEDs are super thin and fit within the panel thickness without protrusion.
Resistors: Embedded resistors ensure that the current is properly distributed to the LEDsswitch components and work in applications in which the current is not source-modulated.
SMT embedded components: For switch panels relying on SMT, APEM can, if requested, directlycan integrate diodes, transistors and/or photo sensors onto the polyester circuit of the membrane switch keypad to enhance the its capabilities.
Connections
Simply stated, connectors connect the keypad and the device it will control. Although connectors consist of a contact device and a molded plastic housing, connectors are anything but one-size-fits-all. Knowing which connector to use for a given application can be daunting. APEM engineers can share the benefit of years of experience to assist customers.APEM integrates either crimping or ZIF/LIF-compatible connectors:
Crimping connectors: APEM’s supplier of choice is NICOMATIC® and we prefer their CRIMPFLEX line of products. These high quality connectors comply with the most rigorous electric and mechanical requirements and provide a great connection, especially in applications where high vibration is expected.
CRIMPFLEX connectors are mounted by installing the pins on a circuit tail extremity and assembling it into a molded plastic housing. The crimping is accomplished by piercing the conductor in 6 points, ensuring excellent mechanical retention (2 points) and electrical contact (4 points), with the lowest possible contact resistance. Low or high insertion force or locking versions can be specified.
CRIMPFLEX connectors are reasonably priced. Standard connector housings available are:
- OF Series: this series fits with the most common interfaces
- OM Series: OM connectors interface with cables and come with an orientable locking system
ZIF/LIF (also called FFC/FPC) compatible connectors: For more complex applications, ZIF (Zero Insertion Force) or LIF (Low Insertion Force) may be more appropriate. ZIF/LIF connectors allow for a higher level of integration. For ZIF/LIF connections, the connector system is on the PCB, not on the membrane tail.
The tail of the circuit is inserted into the ZIF/LIF connector to create the contact, with a stiffener laminated under the tail to ensure stability and maintenance of the electrical contact.
A ZIF/LIF connector can be specified to have from 2 to 30 positions on a single row. For smaller electronics, distances between of 1mm, 1.25mm, 2mm or 2.54mm are available. Because ZIF/LIF connections degrade with insertions, the maximum number of insertions should not exceed 10 cycles.
APEM can provide a conductive side on the bottom of the tail to accommodate customer requirements. With these types of connectors, care needs to be taken to correctly place the tail die cut in relation to the printed traces. Resistance of the circuit may be increased in spacing of less than 1mm where the circuit traces are necessarily thinner.
Back Adhesive
Rear adhesive ensures a permanent adhesion between the keypad membrane and the substrate on which it will be installed. Choice of adhesives is critical if premature delaminating is to be avoided.APEM uses high quality FASSON® and 3M® adhesives. For applications where the plates and housings are of metal and high energy plastics, our standard adhesives are suitable. When outstanding adhesion to low surface energy plastics, powder coated paints or lightly oiled metals is required, APEM uses 3M® 300 LSE (Low Surface Energy) back adhesive.
Sealings
APEM membrane switch panels are intrinsically sealed against humid environments. Mounted on a housing, our switch panels are sealed to IP54.When the flex tail is under the keypad and a higher protection level is required , APEM can add a gasket beneath the graphic overlay to prevent the infiltration of liquids, moisture and other substances to IP67 levels.
Backlighting
Typical lighting options offered by APEM include Phosphorescent inks, Electroluminescent lamps and LEDs.: Key characteristics of each are compared in a table following the general descriptions:Phosphorescent inks: All phosphorescent light sources work by storing energy during exposure to a light source and then releasing it as light when in darkness. Phosphorescent lighting on a membrane switch panel is achieved by a layer of phosphorescent material in the inks of the graphic overlay. Colors are limited to green/yellow and the intensity of the emitted light decreases over time. Prior to use, the phosphorescent-lit membrane panel needs to be “charged” by exposure to light and “recharged” periodically. APEM phosphorescent material is flexible and withstands bending well
The advantages of phosphorescent back lighting are that no external energy source is required and the backlighting it provides is uniform, even on very complex forms. It is an extremely economical solution for keypads that will not remain in prolonged darkness.