Most electronic devices that have a button will always consist of a switch. On the surface, it may look simple. But in reality, it’s comprised of countless small components.
One of these components is the membrane switch. If you’ve taken a look at the inside of the remote control, you’ve probably seen them at least once. They’re the tiny mechanisms you see at the top of each button. You may also recall that it’s typically made of silicone. However, it’s worth noting that apart from the silicone type, there are many other types of membrane switches.
One particular type that you may have heard of recently is the metal dome switch, which is currently the most popular choice among manufacturers. If you’re considering using a metal dome switch for your next engineering project, here are a few things you should know:
1. A Metal Dome Is Exactly As The Name Suggests
Metal domes look exactly like what you’d imagine. It’s a metallic component that takes the shape of a dome. Its composition consists of either stainless steel or copper alloy. At the center of the dome, you’ll see a small bump. This bump allows the membrane switch to make contact with the circuitry and activate the response without pressing the metal dome all the way through.
However, there are other variants of metal dome switch that don’t have this said bump but, rather, a dimple or concavity. You’ll get to know more about this specific type later on.
2. Metal Domes Have High Actuation Force Despite Low Profile
Actuation force refers to the amount of force it takes to depress the switch until it makes contact with the circuit and triggers a response. A high value means it’s difficult to activate the switch, while a low value means it’s easy to get a response. For your reference, the average measurement for membrane switches is 60 to 80 grams, with an upper limit of 150 grams.
On the other hand, the actuation force of metal domes may range from 40 to 2,250 grams, and 2,250 grams is by no means a small amount. This becomes even more surprising considering how metal domes have a low profile and is among the smallest types of membrane switches.
3. Metal Domes Are Among The Most Long-Lasting Switches
Another metric you’ll often see when researching switches is cycle, cycle being the number of times you can press a button at which the switch is installed until it stops functioning.
A higher value means it’s more long-lasting. For example, the average cycle of a membrane switch is 500,000. This means once you press it 500,000 times, it’s likely to stop working. Of course, it doesn’t stop functioning as soon as it hits that number since it’s only an estimate. Still, it’s an accurate estimate of how long it’ll last. Considering that the cycle of metal dome switches typically reaches millions, it’s no surprise why it’s a popular choice among manufacturers.
4. Metal Dome Switches Come In A Variety Of Shapes
Despite the fact that it’s literally named metal dome, this specific type of membrane switch may come in a variety of shapes, each with its own specialties. Here’s a closer look at each type:
- Four-Legged: This is the most popular variant of metal domes and is perhaps the most reliable one as well. As the name implies, a four-legged metal dome consists of four blunt edges from left, right, bottom, and top. It’s well-known for its excellent ventilation properties.
- Round: A circular metal dome is the smallest out of the bunch, making it the perfect variant for small circuit boards as you’re able to save space for additional components.
- Oblong: An oblong-shaped metal dome has the highest actuation force among the six types of switch. Hence, it’s ideal if you want to add a button that requires a hard press to trigger.
- Triangle: A triangle metal dome is similar to the four-legged variant, except it only has three blunt edges. Unlike the previous variant, a triangle dome has a relatively low actuation force.
- Square: Square metal domes are known for surviving tens of millions of life cycles, making them the most long-lasting and durable variant of the metal dome switch.
- Custom: The malleability of metal makes it possible to change its form and shape according to your requirements. If your specific requirements for the switch can’t be accommodated by the five previous variants, a custom metal dome will be the ideal choice.
If you ever decide to use metal domes, make sure you take your time selecting the shape of your metal domes. After all, each of them has varying properties, so you better choose the right one.
5. Installation Of Metal Domes Require Adhesives
Usually, when one wants to install a metal component to a device, soldering is the best bet. But despite comprising of metal, installing a metal dome switch requires an adhesive, specifically a retainer or a spacer layer. This is because, as stated earlier, a metal dome is a relatively small component, so soldering it typically ruins its shape, effectively making it useless.
6. They Must Be Installed On A Flat Surface As They Cannot Bend
Other types of membrane switches, such as silicone and rubber, can bend freely even after their production. Their flexibility makes it so that they can fit in extremely narrow areas.
Unfortunately, a metal dome switch doesn’t have such flexibility. It might be malleable, but once it’s manufactured, it can no longer bend as freely as rubber or silicone. And for that reason, it’s advisable to refrain from installing them in narrow areas. This is because it may cause excessive friction, which in turn may damage the inner workings of the device.
7. A Metal Dome Switch May Consist Of A Dimple
Earlier, it was mentioned that some metal domes consist of convexity or bump at its center. Those are called non-dimpled metal domes, which means there are also dimpled domes. A dimpled metal dome consists of a small cavity at its center instead of a bump. While it may not look much, this small dimple provides a specific benefit, and that is to prevent or minimize the excess electrical reaction that the switch may generate when triggering or activating.
Closing Thoughts
Although there are many other types of membrane switches out there, metal domes are he popular among manufacturers. After all, it carries countless practical properties. And if you’ve been paying attention to this article, you’ll know that it’s the most versatile option. Be that as it may, you must still consider your other choices when selecting a membrane switch.
