Some substances have a natural tendency to resist adhesion to each other, like a piece of cellophane tape on brick. Silicone rubber and acrylic adhesive have a similar reaction. Acrylic adhesive is the industry  choice when attaching things to polyester membrane switches. However, when the silicone rubber keypad’s surface is left untreated, it will not adhere to polyester membrane switches with acrylic adhesive. Much like cellophane tape on a brick wall, it just won’t stick. One alternative is to use a mechanical means to put the two pieces together. This is effective, yet expensive, and will diminish a manufacturing budget and profit margin rather quickly.

Using a bonding coating we designed, SiTECH has solved this dilemma, making it possible to bond your silicone rubber keypads to the polyester surface beneath. We use our custom blended material called Si Prime that binds the silicone rubber keypads to the acrylic adhesive which, in turn, bonds to the polyester membrane switches. We add a layer of Si Prime to the custom rubber molding to eliminate the cellophane tape-on-brick effect. Both layers interact well with the Si Prime barrier. As a result, the adhesive bond is very strong and long-lasting, creating fully functional silicone rubber keypads for the user at a lower production cost for you.

Strong adhesion is critical for usability, since the top layer of your keypad is typically what people see and how they use your product. Without the liquid injected custom silicone keypad and markings on the keys, they would only see the unprotected circuits below the silicone rubber keypads, making the device useless.

Using Si Prime in combination with any acrylic based adhesive, there is a durable bond with your silicone rubber keypads which grows stronger over time. It won’t fall off, shift or come loose. This is useful for a number of applications, including aeronautic, medical industrial and military keypad molding. It has been tested by an independent lab and field proven with multiple applications on more than one million units.