Overview of Rubber Metal Dome Keypads
Rubber metal dome keypads are a hybrid between flat-panel membrane keyboards and mechanical-switch keyboards. In these keypads, pressing a key causes a rubber dome to collapse, which in turn connects two circuit board traces, thus registering a keystroke. These keypads can employ either metal dome switches or polyurethane domes (polydomes). Metal dome switches, made of stainless steel, provide tactile feedback and are highly durable, often exceeding 5 million cycles. These switches can be plated with nickel, silver, or gold.
Benefits of Rubber Metal Dome Keypads
Although polyurethane domes are less expensive, metal domes are favored for their distinct tactile feedback compared to the softer response of polydomes. Users can immediately feel the actuation of a metal dome switch, enhancing usability. Additionally, metal domes boast a higher lifespan, which justifies their higher cost. They are particularly popular in the automotive industry for their durability and superior tactile feedback.
A significant advantage of metal dome keypads is their low profile. For instance, Apple incorporated a stainless steel dome switch in its 2015 MacBook, resulting in a 40% thinner key assembly while maintaining a solid feel and positive feedback.
Design Features of Rubber Metal Dome Keypads
Manufacturers and designers often prefer rubber metal dome keypads due to their aesthetic and functional benefits. These keypads can be customized with embossed or debossed features, printed text, painted icons, backlighting, and various coatings (polyurethane, epoxy, UV) to protect against environmental factors. Three-dimensional rubber keypads combine the reliability of membrane switches with the tactile feel of silicone rubber keypads, making them suitable for medical, industrial, and commercial applications.
Rubber keypads offer extensive design flexibility, allowing customization of key shapes, sizes, and colors. Metal domes provide a consistent tactile response without needing thin web areas, which can tear. This makes metal dome designs more robust than traditional webbing-based designs.
Challenges with Rubber Metal Dome Keypads
One challenge with rubber metal dome keypads is aligning the dome switches with the keypad actuators. The actuators, ideally no larger than 25% of the dome’s diameter, must be precisely aligned to avoid interfering with the dome’s transition ring. Misalignment can lead to poor switch performance and failure.
As electronics become more compact, dome switches are manufactured as small as 3mm in diameter, complicating alignment further. To address this, a reverse dimple can be formed in the center of the dome, serving as a tactile concentrator and compensating for slight misalignments.
Types and Applications of Metal Domes
Metal domes are increasingly popular in custom silicone keypad assemblies. Made from stainless steel, they typically have a switching capacity of 1 watt, a switching voltage of 0.1 to 50 VDC, and a switching current of 0.005 to 100 mA DC. They operate across temperatures from -45°C to +100°C and are coated with nickel, silver, or gold. The four main types of metal domes are:
Triangle Domes (Three-Leg Domes): Known for strong tactile feedback, these domes can withstand up to 6,000 grams of force and do not require adhesive for mounting, making them suitable for high-temperature applications. They range from 5mm to 13mm in size.
Circular Domes: These domes, also known as round domes, have a longer lifespan and are ideal for low-profile switches. Their sizes range from 3mm to 20mm, with a force range of 100-600 grams.
Four-Leg Domes (Cross Domes): Designed for applications where both positive and negative traces are on the same side of the circuit, these domes offer a superior clicking feel and are the tallest, ranging from 5mm to 20mm with a force range of 125-500 grams.
Oblong Domes (Oval or Rectangle Domes): Used for low-profile switches on circuit boards with limited space, these domes are also suitable for larger keys like space bars. They vary in size from 3mm x 4mm to 51mm x 13.70mm, with a force range of 100-500 grams.
Metal domes are becoming standard in keypad assemblies and membrane switch designs, with custom options available to meet specific needs.
Metal domes are available in a variety of shapes and actuation forces to suit different applications, including circle, cross, triangle, and oblong. If you need a special shape, we can customize it based on your design.