The top layer of a membrane switch is the graphic interface between the user and the machine. While other
layers are essential to overall performance, it is a well designed and attractive graphic layer that impresses the
user first. The other layers of the membrane switch need to support the graphic layer by providing the qualities
and functionality you need.
RSP Inc. works with each customer to design the optimals witch that meets your needs. We can maximize a
switch for appearance, functionality and price. RSP Inc. prides itself on testing each switch to your specifica
tions so that there are no failures in the field.
The membrane switch can be the most important part of a product; do not trust the design and construction to
just any supplier.
If you need additional information please contact us directly at (414) 546-4417.
RSP Inc. designs custom membrane switches to your specification. Ideally, the membrane switch will be
designed simultaneously with the rest of your product. (Please note that we have the capability to provide you
with many other parts for your project as well, such as the PCB, plastic enclosure, and even turn-key assem
blies). Since we want you to have the best membrane switch possible, here are things to consider during the
design phase.
Mechanical
• What material type is the switch laminated to? This will determine the adhesive needed.
• Will tactile response be required?
• Is actuation force a factor? The usage effects whether you want a heavy or light force to actuate the key.
RSP, Inc. © 2009 All Rights Reserved 2/25/2009Environmental
• Will this product be used indoors or outdoors? Does this product need NEMA 4 construction? NEMA 4
provides a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water and
hose-directed water.
• Is this product exposed to the elements?
• What temperatures and humidity range will this product experience?
• What type of solvents and cleaning solutions will come into contact with the switch?
Electrical
• How many switches will there be?
• What type of pinout will be used (common bus, X-Y matrix, other)?
• What closed loop resistance is acceptable?
• Will Electromagnetic (EMI) or Electrostatic (ESD) shielding be necessary?
Appearance
• Will edges be exposed? It is best to place the membrane switch into a recess that is the same or greater
thickness as the membrane switch to avoid accidental interaction.
• Will embossing be required? Embossing improves a user's ability to locate keys.
Design Stage
Artwork
RSP Inc. accepts many different formats of artwork files. To find out if we can work with your artwork, please
send a file with contact information to sales@ryanscreenprinting.com. If you do not have artwork or need help
with your design, our graphic artist and engineering experts can also design the graphics overlay and circuitry
for you. Common file types accepted by RSP Inc. include:
• Adobe Illustrator -AI of EPS
• CorelDraw - CDR
• AutoCAD - DWG or DXF
• Portable Document Format - PDF
Sample / Re engineering
If you have a sample part, providing it to your sales associate can be very helpful for quoting and rebuilding. If
drawings are available, a sample can confirm colors and construction in cases where the membrane switch was
not built to specifications. If there are not drawings, in the case of a replacement membrane switch on a
machine, a sample may be the only mean available to construct the schematics, match colors, and specify the
layers.
Color samples provide the best method of color matching. If an exact match is necessary, please let your sales
professional know so that a sample can be provided to you for approval.
• Pantone Matching System (PMS ###)
• Color Samples - Preferred samples are 3" x 3" on polyester or polycarbonate
RSP Inc. designs custom membrane switches to your specification. Ideally, the membrane switch will be
designed simultaneously with the rest of your product. (Please note that we have the capability to provide you
with many other parts for your project as well, such as the PCB, plastic enclosure, and even turn-key assem
blies). Since we want you to have the best membrane switch possible, here are things to consider during the
design phase.
Mechanical
• What material type is the switch laminated to? This will determine the adhesive needed.
• Will tactile response be required?
• Is actuation force a factor? The usage effects whether you want a heavy or light force to actuate the key.
RSP, Inc. © 2009 All Rights Reserved 2/25/2009Environmental
• Will this product be used indoors or outdoors? Does this product need NEMA 4 construction? NEMA 4
provides a degree of protection against falling dirt, rain, sleet, snow, windblown dust, splashing water and
hose-directed water.
• Is this product exposed to the elements?
• What temperatures and humidity range will this product experience?
• What type of solvents and cleaning solutions will come into contact with the switch?
Electrical
• How many switches will there be?
• What type of pinout will be used (common bus, X-Y matrix, other)?
• What closed loop resistance is acceptable?
• Will Electromagnetic (EMI) or Electrostatic (ESD) shielding be necessary?
Appearance
• Will edges be exposed? It is best to place the membrane switch into a recess that is the same or greater
thickness as the membrane switch to avoid accidental interaction.
• Will embossing be required? Embossing improves a user's ability to locate keys.
Design Stage
Artwork
RSP Inc. accepts many different formats of artwork files. To find out if we can work with your artwork, please
send a file with contact information to sales@ryanscreenprinting.com. If you do not have artwork or need help
with your design, our graphic artist and engineering experts can also design the graphics overlay and circuitry
for you. Common file types accepted by RSP Inc. include:
• Adobe Illustrator -AI of EPS
• CorelDraw - CDR
• AutoCAD - DWG or DXF
• Portable Document Format - PDF
Sample / Re engineering
If you have a sample part, providing it to your sales associate can be very helpful for quoting and rebuilding. If
drawings are available, a sample can confirm colors and construction in cases where the membrane switch was
not built to specifications. If there are not drawings, in the case of a replacement membrane switch on a
machine, a sample may be the only mean available to construct the schematics, match colors, and specify the
layers.
Color samples provide the best method of color matching. If an exact match is necessary, please let your sales
professional know so that a sample can be provided to you for approval.
• Pantone Matching System (PMS ###)
• Color Samples - Preferred samples are 3" x 3" on polyester or polycarbonate
Tactile Feel
Because membrane switch have relatively short travel, it is often desirable to provide users tactile feedback and
"snap" action.
There are two types of domes that provide tactile feel, stainless steel and molded polyester domes (polydomes).
Stainless steel domes are commonly used in small to medium run jobs. They offer the longest actuation life
and a better tactile feel than polydomes. RSP Inc. maintains and inventory of domes ranging from 3mm in size
and a variety of shapes.
RSP, Inc. © 2009 All Rights Reserved 2/25/2009Polydomes can be formed into the upper circuit or the graphics layer. There is additional molding tooling
needed which increases the tooling costs. Because individual domes do not need to be placed above each
contact polyester domes are often used in larger quantities.
Our engineering staff will provide expert advice on the type of domes best suited for your application.
Lighting Design Elements
LED's (Light Emitting Diodes)
RSP Inc. can provide many different types of integrated LEDs. The selected graphics overlay material is
usually clear with gloss or matte finish.
The LED needs a translucent window on the graphic layer to allow the light to shine through. The window can
be clear or match the color of the LED (or any color specified).
LED's can either be surface mounted to the circuit layer or be on a separate LED Layer.
Fiber Optic Backlighting
Fiber optic backlighting does not wear out. In a typical design, two or more layers of woven fiber optic cloth
are used to for a rectangular light emitting area. The fiber optic product is typically 0.068" (1.7mm)thick and
anywhere from 1sq inch to over 100 sq inches. The fibers coming off one end are then bundled into a circular
ferrule and coupled to one or more LED light sources. Fiber optic panels never need replacement. Remote
light sources offer 10,000 to 100,000 hours life. Optical Fibers are not effected by extremes in humidity (0% to
100%) or temperature (-40 to +85 deg C)
Electroluminescent Lamps (EL Lamps)
EL Lamps are a good option for backlighting membrane switches. They are lower priced compared to fiber
optics and offer additional design flexibility. The color of light emitted from an EL can vary depending on the
phosphors that are used. Some common colors are blue/green and yellow/green, white, blue and orange. The
life of an EL Lamp varies based on the way it is used. EL Lamps have a half life: once they reach their half
life the brightness stars to fade rapidly. If the light is just being turned on when you hit a key on a switch the
lamp will take a very long time to reach its half life of approximately 3000-8000 hours depending upon the
quality of the phosphor being used. EL Lamps are not a good choice if the lamp is on for an extended period of
time. To help expand the life of an EL Lamp you can have it fade or flash, this could double the life of the
lamp.
RSP, Inc. © 2009 All Rights Reserved 2/25/2009Internal Design Elements
Upper and Lower Circuit Layer
The upper circuit layer in a membrane switch can be a tactile metal dome, polydome, or polyester. It depends
on the type of switch you are building and the actuation requirements. Typical polyester layers are . 005" thick.
Conductive Traces
Conductive traces are generally printed silver on polyester.
RSP Inc. can also supply you with printed circuit board or copper flex circuit.
• Traces usually have a minimum line thickness of .016"
• Standard line thickness of .025"
Spacer / Insulator
Insulators vary in thickness from .002" to .010" and are generally polyester with double-sided acrylic adhesive.
In a membrane switch with tactile domes, the spacer layer creates a gap so that the dome is not pre-actuated
(under pressure). In a non-tactile membrane switch the spacer layer creates a gap between the upper and lower
circuit layers.
EMI / ESD / RFI Shielding
Printed conductive inks, aluminum foil, copper foil or Indium Tin Oxide (ITO) is employed in membrane
switch designs to minimize the impact of electromagnet interference (EMI), electric static discharge (ESD), or
radio frequency interference (RFI).
Connectors
RSP Inc. uses a variety of connectors.
Standard connector
• 0.100" pitch Male/Female, and Solder Tab
• Plating-Tin or Gold
Zero Insertion Force (ZIF) Connector
• This connector is designed for installation of ZIF Connectors
• 1 mm spacing standard
Adhesive
RSP Inc. typically uses a .002" adhesive on back of the overlay and throughout the internal membrane switch.
On the rear of the membrane we use 3M adhesive standard; 3M is recognized in the industry for outstanding
adhesion and life span. Make sure when you compare quotes that each supplier is using 3M adhesive.
Most membrane switches are constructed from 3M's 200MP family of adhesives. Internally, a .002" adhesive
is typically used (3M 467).
RSP, Inc. © 2009 All Rights Reserved 2/25/2009Adhesion qualities are affected by the substrate surface energy (high or low), types of materials used, the
required bonding requirements, environmental concerns and a number of other factors. Your sales associate can
help you decide which is best for your project.
Sub-Panel / Back Plate
Most membrane switches are mounted to a back plate or sub-panel. RSP Inc. can supply you with a variety of
different materials and finishes.
• Custom Molded Plastic - injection molded plastic built to your specifications
• Plastic Panel (Acrylic, Lexan, Polycarbonate, etc...) - flat die cut or laser cut plastic in a variety of
thicknesses
• Aluminum - brushed, anodized, sealed, unsealed, dyed
• Stainless Steel - brushed, sanded, and other finishes.
Printed Circuit Board
A printed circuit board can act as the lower switch layer. RSP Inc. can supply single or multi-layer PCB's.
Studs or standoff can be integrated into the PCB with the board acting as a supporting panel. PSB can also be
assembled directly to the housing
References
A. Die Cutting Tolerances
B. Electrical and Mechanical Specifications
C. Membrane Switch Blueprints
D. Glossary
A. Die Cutting Tolerances
Standard tolerances for the industry are +/- .010"
Laser cutting tolerances on our machinery are +/- .004" depending upon the material.
B. Membrane Switch - Electrical and Mechanical Specifications
Electrical
1. Configuration - momentary SPST normally open
2. Current Rating - 30V - 100MA to 120V - 10MA maximum
3. Breakdown -220 V RMS
4. Closed - 100 MEG OHMS contact resistance minimum
5. Open - 10 MEG OHMS contact resistance minimum
RSP, Inc. © 2009 All Rights Reserved 2/25/20096. Capacitance - 30 Picofarads
7. Life -
a. Flat Switch - approximately 5 million cycles
b. Domed Circuit - approximately 1 million cycles
c. Metal Dome - approximately 5 million cycles
8. Contacts - Silver to silver. RSP Inc. uses only high qualityu silvers since low quality silver mayu not last as
long and may contribute to silver migration (the tendency of silver to spread or "creep" especially when
exposed to moisture).
