Here at Si-Tech, there are certain rules, recommendations and protocols we follow when creating our keypad designs, from decorating to color matching to coatings. Let’s take a look at some of those design rules.

When designing a silicone component or keypad, it’s critical to think about how the tooling will be crafted, along with the way in which the tooling will impact production. Certain industry standards can assist in creating your design, such as these seven fundamentals:

1. The minimum radius that should be used is 0.010”. We do not recommend using anything smaller than 0.020” in deep cavities or pockets.
2. Keys taller than 0.200” should have a minimum draft of 1°, and those taller than 0.500” should have a minimum draft of 2°.
3. A keypad’s mat should have a minimum thickness no less than 0.040”. When too thin, this can pose a negative effect on the force profile you want.
4. A keypad’s maximum thickness should be no more than 0.150”.
5. Recommended air channel geometry is 0.080” –0.125” wide by 0.010” –0.013” deep.
6. Tear plugs are required in openings within the silicone part, removed by tweezers or by hand. Thus, the smaller the opening, the tougher it is to get the plug out.
7. Between a bezel and a key, the clearance should be no less than 0.012”.

Silicone Keypads: Backlighting

Many users request backlighting to assist in viewing the keys more readily in dark conditions.

This process is achieved through the use of LED lighting through a printed circuit board. This involves the insert molding of an LED insert or clear window to display the light.

LED light pipes, windows and displays come with these five top design recommendations.

1. For a feature window opening, the maximum depth of an undercut is 0.250”.
2. The insert molded silicone light pipe must be a minimum size of 0.060”.
3. An insert molded window’s minimum thickness is 0.030”.
4. For a molded silicone light pipe, the minimum height is 0.030”.
5. Between the edge of a silicone light pipe or window and keypad or opening, the minimum distance is 0.030”.

Shrink & Tolerance Options

It’s common for Injection molded silicone components and keypads to shrink somewhat after the demolding process, but the amount will vary between molding temperatures and what materials are used. Usually, a component or keypad will shrink between two and three percent from the molded size.

Because of the variable shrinkage a silicone part can have, liquid silicone rubber components maintain a certain standard tolerance for specific sizes.

As you can see, from backlighting to overall component design, many rules must come into play in order to get the design just right for the customer.

Contact Si-Tech

To learn more about the keypad design recommendations and rules process we follow here at Si-Tech, contact us today at 757-887-8488.