Membrane Switch and Membrane Keypad Buying Guide: Choose the Optimal Switching Technology for Your User Interface

One of the challenging decisions design engineers, a subset of Mechanical Engineering, face when designing a user interface [PDF] for their equipment is what type of specific switching technology should be used. The membrane switch is the bridge that connects end users to your products or machines, making this component one of the most critical in the product design process. Therefore, carefully examining the many influencing variables and selecting the right design options for your specific application is a process not to be taken lightly.
According to, user interface (UI) design “focuses on anticipating what users might need to do and ensuring that the interface has elements that are easy to access, understand, and use to facilitate those actions. UI brings together concepts from interaction design, visual design, and information architecture.”
It’s such a critical component of product and digital design that there’s a growing body of research devoted to UI design principles for various applications, such as assistive devices and technology products [PDF] and even specifics like keyboard user interface design. Chapter 7 in Systems Analysis and Design in a Changing World, sixth edition [PDF], makes an excellent case for the importance of user interface design for the user experience: For the user, the interface is the system.

There a number of considerations that must be weighed in choosing the optimal switching technology that contributes to the ultimate usability, functionality, and durability for the end product. Things like the typical operating environment, user feedback and experience, packaging and design constraints, and cost are just a few of the many factors to consider. As machine design evolves, environmental considerations are key in designing advanced electronics such as Machine-to-Machine (M2M) products.
For the purpose of simplified explanation, switching technologies can be grouped into two primary categories: traditional and specialty technologies.
Traditional switching technologies include:
Custom membrane switches from the tactile membrane switch manufacturer, Pannam

Specialty Switching Technologies include (but are not limited to):

This guide will address the many considerations involving traditional switching technologies. Overall, membrane switches offer an array of design options that enable manufacturers to develop customized, targeted, and appropriate interfaces [PDF] that adequately bridge the end user to the machine’s functionality, offering ease of use and appropriate accessibility. Some applications require additional flexibility while maintaining durability, for instance, especially as the field of electronics advances.
A typical membrane switch assembly contains several layers, or components, listed from top-down: 

  1. Graphic overlay
  2. Overlay adhesive
  3. Top circuit layer
  4. Circuit spacer
  5. Lower circuit layer
  6. Rear adhesive layer
  7. Rigid support layer

The graphic overlay is critical to the overall appearance of the final product, and serves as the visual representation of the product’s or machine’s control panel. There are a number of additional design options that can be chosen to configure a completely custom membrane switches to suit your application’s specifications, which include, but are not limited to:

There are some key advantages of different types of traditional membrane switch technologies for different applications. The following sections discuss each type of traditional membrane switch technology in detail.
Silver Flex Membrane Switches
Silver Flex membrane switch panels utilize screen-printed silver and carbon conductive inks printed on flexible polyester layers separated by an adhesive spacer. This is the most common design used in flexible, custom membrane keypads, offering a slim, space-saving design.
They’re also quite cost-effective when compared to bulkier, expensive, electromechanical switch assemblies, and the process of screen-printing conductive silver inks onto a flexible, film substrate poses less potential threat to the environment compared to chemically etched copper.
Silver Flex membrane switches offer you a variety of design options: Membrane Switches

Additionally, a Silver Flex membrane switch uses a graphic overlay, which also has a number of design options:
Polyester Keypad

  • Digital printing, screen-printing, or a combination of both
  • Pillow or rim embossing
  • Transparent and/or tinted display windows
  • Selective textures
  • UV hard-coat surface finishes

A typical Silver Flex membrane switch design consists of the following layers:

  • Graphic Overlay – Graphic overlays are typically constructed of polyester, the material of choice due to its superior chemical resistance and flex life compared to polycarbonate. Pannam can either digitally print, screen-print, or employ a combination of both methods to insure you get the right colors, textures, and finishes your Silver Flex membrane switch design requires.
  • Overlay Adhesive – The overlay adhesive layer bonds the graphic overlay to the top circuit layer. This overlay adhesive is typically an acrylic adhesive, selected for its durability and ability to maintain adherence in atypical environments [PDF], such as moist environments.
  • Top Circuit Layer – This is a .005″ – .007″ heat-stabilized, polyester printed layer with silver-filled, electrically conductive inks and dielectric inks. This layer can also encapsulate metal domes or incorporate polydomes, which are used to achieve tactile feedback, an important design consideration impacting usability.
  • Circuit Spacer – This layer separates the top circuit from the bottom circuit, so the switch remains normally open until the keypad is pressed. The circuit spacer is a polyester spacer with adhesive on both sides.
  • Lower Circuit Layer – The lower circuit layer is a .005″ – .007″ heat-stabilized, polyester-printed layer with silver-filled electrically conductive inks and dielectric inks. This layer terminates as a flexible tail that serves as the interconnect to controller PCB’s or other electronics.
  • Rear Adhesive Layer – This adhesive layer bonds the entire membrane switch package to the product enclosure, housing, or to a rigid support panel. Pannam can specify the appropriate adhesive type and thickness to bond your membrane keypad to your equipment.
  • Rigid Support Layer – This optional layer can add structural integrity to the membrane switch assembly. Materials can be aluminum, FR-4, steel, etc. Mounting hardware such as studs and standoffs can also be utilized in this layer.

PCB Membrane Switches
The PCB Switch construction utilizes a printed circuit board (PCB) which can serve a dual purpose in your membrane switch design. PCB Switches are typically more costly than Silver Flex membrane keypads, but can accommodate dense circuit patterns and more complex circuit patterns compared to Silver Flex membrane keypads.
A PCB membrane switch also allows the electronic components to be “hard-soldered” into the PCB, whereas membrane switch components are placed using a polymer thick film conductive paste. With a PCB membrane switch, the PCB can serve as a rigid backer, and is also a very durable and reliable method to incorporate LED’s, resistors, LCD’s and other components.
PCB membrane keyboards offer you a variety of design options:

Like Silver Flex membrane switches, PCB membrane switches use a graphic overlay which can be custom-designed based on several design options:

  • Pillow or rim embossing
  • Digital printing, screen-printing, or a combination of both
  • Transparent or tinted display windows
  • Selective textures
  • UV hard-coat surface finishes

Copper Flex Membrane Switches
The Copper Flex Membrane Switch constructions are ideal for smaller designs, where space is at a premium, or where dense circuit patterns or trace routing limitations exist. Copper Flex membrane keypads utilize silver or copper layers which are laminated to a dielectric layer and etched away.
This switching technology combines the ability to accommodate the complex circuit patterns of a FR4 rigid printed circuit board with the flexibility of a membrane switch. Copper Flex keypads also have the advantage of being able to “hard” solder both active and passive components into the assembly, making it a good choice in high-vibration environments [PDF].
Copper Flex membrane switch panels can be produced using polyester or polyimide (Kapton) as the base material depending on your interface requirements. A very thin sheet of copper is laminated to the flexible film substrate then chemically etched away, leaving copper traces. The etching process is not as environmentally friendly and more expensive than screen-printing the silver traces used in Silver Flex membrane switchesCopper Flex Switches
Copper Flex membrane switches offer you a variety of design options:

  • Single and double sided designs
  • Lower electrical resistance and higher conductivity vs. traditional Silver Flex membrane switches
  • Tight trace routing capabilities
  • Thin profile and flexibility of Silver Flex membrane switch
  • Plating options can be tin-lead, nickel, or gold
  • Tactile and non-tactile with either metal or polyester tactile domes
  • LED’s and other components can be soldered

As with the other types of traditional switching technologies, the Copper Flex membrane switch offers a number of design customization options for its graphic overlay component:

  • Pillow or rim embossing
  • Digital printing, screen-printing, or a combination
  • Selective textures
  • Transparent or tinted display windows
  • UV hard-coat surface finishes

Silicone/Elastomeric Rubber Keypads
Silicone rubber keypads use compression-molded silicone rubber with conductive carbon pills or with non-conductive rubber actuators.  They have exceptional resistance to extreme temperatures and aging, making them an ideal choice if reliability is a prominent concern due to likely environmental influences [PDF].
Rubber Keypad membrane switches, or silicone rubber keypads, offer a completely different look and feel than traditional tactile membrane switches. These designs are durable, reliable, and provide superior tactile feedback combined with a longer switch travel. Rubber keypads by Pannam, the silicone keypad manufacturer
A rubber membrane switch uses compression-molded silicone rubber with conductive carbon pills or with non-conductive rubber actuators. Rubber keypads are relatively inexpensive on a per-piece basis, but require fairly expensive tooling, usually making them a design choice for higher-volume projects.
Silicone rubber keypad switches have numerous features that set this type apart from other traditional membrane switch designs. Some of the main differentiating features of this type make the silicone rubber keypad switch an ideal choice for applications requiring more durability or better resistance to exposure to moisture, chemicals, or other compounds.
Some of the primary distinctive features of silicone rubber keypad switches include:

  • Work as a conductive shorting device for Silver Flex membrane switchesPCB membrane switches, and Copper Flex membrane switches
  • Can utilize carbon pills, non-conductive rubber actuators, or stainless steel tactile domes
  • More keypad travel and a completely different feel than traditional tactile membrane switches
  • Actuation forces and switch travel can be customized
  • Unusual keypad shapes and sizes can be used
  • Multiple colors can be achieved by flow molding the color during the compression-molding process
  • Rubber keypad top graphics can be further customized by screen-printing
  • Rubber keypad switches can be spray-coated for enhanced durability
  • Rubber membrane switches have excellent weatherability for outdoor use
  • Can be designed to seal the keypad assembly from moisture and contaminants
  • Silicone rubber is resistant to chemicals and moisture
  • Laser etching the rubber keypads can allow for backlighting individual keypads
  • Fiber Optic backlighting
  • EL (Electroluminescent) backlighting

The field sales and in-house engineers at Pannam-Technigraphics can be a useful resource for you to utilize when determining the most cost-effective user-interface for your project. Additionally, our experienced Design Engineers bring vast experience designing user interfaces for a variety of applications and can guide you in choosing the appropriate customization options based on your product specifications and end user requirements.

Need answers to all your questions about designing a membrane switch interface for any application?