Silicone combines excellent feel, reliability and long life in the most rugged environment. Silicone keypads are used in a wide range of applications including medical, industrial, instrumentation and communications equipment. While designing a new silicone rubber component or keypad it helps to use the fundamental rules of dimensioning and tolerancing, as well as some general recommendations for mechanical design. We have put together a short guide highlighting the key mechanical design considerations to help you in the process of developing silicone keypads and specialty products.
- Distance of a key’s diaphragm to the edge of the keypad’s matte and any through hole is 0.040″.
- Minimum key pitch dimension is 0.080″.
- Distance between two diaphragms is 0.040″ (measured at base of diaphragm).
- The smallest blend radius of key’s side wall to top of key is 0.010″.
- Typical key taper is ³ 1° depending on key height.
- Typical chamfer dimension on a tactile keypad is 0.020″.
- Typical chamfer angle on a tactile keypad is 45.
- Clearance between a bezel to a key is 0.012″.
- Typical base (matte) thickness is 0.040″.
- Standard air channel geometry is 0.080″ to 0.125″ wide by 0.010″ to 0.013″ deep.
- Conductive contact area is 0.030″ based on keypad application and size.
- Sealing bead(s) top and/or bottom for environmental design requirements.
- Assembly aids via rattails and/or perimeter lip to hold rubber keypad to feature:
- Through hole diameter is 0.025″.
- Corner radius on matte and key’s 0.015″.
Display/ LED lightpipe/ Window opening:
- Maximum depth of undercut for feature window opening is 0.250″.
- Underside lip for window opening is the depth of undercut(#14) x 0.660″.
- Minimum size for molded in silicone window/lightpipe is 0.060″.
- Minimum thickness for molded in silicone window is 0.030″.
- Minimum height for molded in silicone lightpipe is 0.030″.
- Minimum distance from window/lightpipe to and edge is 0.030″.
- Min / Max. wrap around underside is 0.060″ to 0.500″. Deeper wraps may be considered depending on design.
- Sealing rib diameter is 0.030″.
Keypad Wrap – Around Design:
The wrap-around design offers unique capabilities in silicone rubber. Using liquid injection process, one can create hand-held units similar to complete plastic cases. With the wrap-around feature, an appealing product can be designed with all the protection requirements for harsh environments.
Typical Part Tolerances:
SiTECH’s team, with over 75 years of experience in silicone keypad design and molding is committed to providing complete customer satisfaction with the highest quality products in a successful and timely manner. The customer is the focus of SiTECH’s business. We are locally owned and operated. We manufacture all silicone components in-house. Call us at: 757-887-8488 to speak with one of our Engineering staff about your custom silicone keypad or component, or use our contact form to request a quote today.