| Molded keypads made from silicone rubber offer | | | | of marking the rubber. |
| a variety of features traditional keypads don't | | | | The markings can be screen printed on to the |
| have. However there are some important | | | | silicone with special inks designed for the material. |
| decisions to make to create the best interface | | | | This method offers a variety of colors and |
| for your users. | | | | finishes depending on what kind of final |
| Tactile Feel | | | | appearance you desire. It is a very economical |
| Lack of tactile feedback is a common complaint | | | | marking solution. |
| when using custom silicone keypads. If an | | | | Laser etching involves spraying a translucent |
| operator doesn't get some kind of response it's | | | | rubber key with an opaque topcoat. The topcoat |
| hard to tell whether a key press has been | | | | is etched away with a laser, revealing a base coat |
| accepted. The tactile characteristics of the keys | | | | or the rubber itself. This method is commonly |
| are controlled by actuation force and contact | | | | used in molded keypads that will be backlit. It is |
| force. | | | | also effective on curved keys not suited for |
| Actuation force is the effort required to press | | | | traditional screen printing. |
| the key and make initial contact. Contact force is | | | | Hard plastic key caps can be placed over the soft |
| the effort required to maintain that contact and | | | | rubber keys. These are more durable than the |
| will always be less than actuation force. The | | | | soft silicone and are ideal for keys that will see |
| difference between these forces is the "click" that | | | | heavy use. |
| the user will feel as the key is depressed. The | | | | Silicone is already highly resistant to temperature, |
| larger the difference in force, the greater the | | | | liquid and many environmental hazards, however |
| tactile feedback. When this force difference is | | | | molded keypad manufacturers offer coatings that |
| expressed as a percentage of activation force, it | | | | improve this resistance further. Coatings can |
| is called the snap ratio. | | | | increase the rubber's resistance to abrasion or |
| Finding the correct snap ratio for molded keypads | | | | chemical corrosion, extending the life of the keys. |
| is a matter of balancing the tactile feel with the | | | | Although these are some of the primary design |
| life of the keys. A higher ratio gives stronger | | | | decisions for molded keypads, there are often |
| feedback but reduced key life. Typically the snap | | | | other considerations depending on the specific |
| ratio is 50% of the actuation force but this will | | | | application the keypad is intended for. Talk to |
| vary depending on the application. | | | | your keypad manufacturer because they have |
| Markings and Coatings | | | | probably designed controls for similar situations |
| Custom keypads typically have markings directly | | | | and can give advice on keypad design. |
| on each key. There are three common methods | | | | |