When designing a custom silicone rubber keypad, there are a lot of options to consider. While most options will stand out as obvious ones, such as “What durometer to use?” or “Is the keypad going to be backlit or not?” there are a few options that might get overlooked during the design stages that could be beneficial and help with cost savings. A few of these options are tool inserts, silicone adhesives, and insert molding. At Si-Tech, we take pride in our experience in the silicone rubber keypad and component industry, and are happy to give tips for making a design become as successful and cost effective as possible.
Tool Inserts
Tooling inserts might seem like an obvious option, but due to the viscosity of silicone, tooling inserts can be a bit of a challenge. However, with the proper engineering support and experience that Si-Tech offers, it can be achieved without difficulty. Tooling inserts are used for making variations of a keypad. A tooling insert can be used, for example, with a keypad that has 5 buttons, but you would also like to make the same keypad with 6 buttons. Tooling inserts make it possible to take out or add a button or feature of the keypad. It’s done by either changing an insert on a cavity of the tool or by changing the insert and purchasing a different core side of the tool. Even if the change you need requires another core, it will help provide savings on the tooling cost by not having to buy two fully separate tools.
Silicone Adhesives
Another design tool that can be easy to overlook for custom silicone rubber keypads is a silicone adhesive. When designing a keypad, you may struggle to decide how to attach the keypad to your unit. There are more options than just putting a bezel overtop of the keypad. One easy solution is using a silicone adhesive to attach the rubber keypad to the completed unit. You might be thinking that a silicone adhesive will not give you a strong enough bond as required. This is why, at Si-Tech, we have developed a coating to help aid the bonding. We call it Si Prime ™. Si Prime™is a coating system used in the membrane switch industry that is specifically designed for bonding silicone rubber to a variety of different surfaces with common acrylic adhesives. SiPrime™ offers a unique solution to the intrinsic problem of bonding rubber to polyester switches for far less cost than mechanical means. This coating serves as a bonding barrier between the silicone surface and an acrylic adhesive. When used in conjunction with any 3M™ 350 series Hi holding acrylic adhesive, Si Prime™ offers a high-bond strength for elastomer keypad applications. Under independent lab tests using ASTM standard D-3330, Si Prime™outperformed by more than two times the bonding capabilities of other silicone-acrylic adhesives.
Insert Molding
Insert molding is a fairly unknown design tool for making a custom silicone rubber keypad. One of the most prominent advantages that insert molding offers is the ability to stop light leakage from traveling key to key. Insert molding is a process that allows for colored keys, clear windows or light pipes to be added to the keypad. Insert molding is achieved by having two molds. One mold is used to make the inserts, which are then placed into the second keypad mold. The inserts are held in place by a high clamping force. This ensures that the inserts will stay in place while the material flows into the mold around the inserts, causing a cross-link bond, joining the inserts to the part and giving the appearance that it was molded all at once.
Si-Tech is a domestic custom silicone rubber keypad and component manufacturer with vast experience in the industry. We are fully ITAR registered and ISO compliant. Contact us today for any of your silicone rubber needs at 757-887-8488 or CS@SiTech-Corp.com.
