Rubber Keypad Switch Comparison: Conductive and Non-Conductive
The rubber keypad manufacturers have been using molded silicon rubber keypad switch for more than thirty years. After all, these rubber keypads do offer a number of benefits. Their 3-dimensional operating surface is really appealing to the consumer.
The great news is that you can find a wide range of keypad switches. In this article, we are going to do a comparison between the two basic styles.
Understanding these two basic keypads will help you make a better decision. Incorporating certain features and elimination some would help the keypad designers to have the best design for their application.
Molded Silicone Rubber Keypad: Basic Styles
There are two basic styles of a rubber keypad. Below, we have listed these styles.
- Conductive rubber Keypad: It can come either with a puck on the backside or with an integral Semiconductor.
- None-conductive Rubber keypad: This type of keypad pushes against a metal snap dome switch.
People use the term keypad for several things. For instance, some may use it to refer to a molded silicone. On the other hand, some might use it to refer to the entire keypad assembling. The assembling will include the incorporated Printed Circuit Board. In addition, it can refer to the decorative bezel.
Therefore, it is important to understand that modeled rubber is part of the assembly. Yes, it is an important part of the lager keypad assembly. Yet, you should not treat it as a stand-alone component.
Molded Silicone Rubber Keypad Switch: Common Features
Manufacturers use molded silicone rubber to create a single piece of rubber keypads. These keypads include visible keytops into a base mat. These keytops rest against a PCB. You will find a thin layer of rubber between the mat and the keytops.
In order to generate high-quality rubber keypads, the manufacturer uses different processes. For instance, to develop an extremely moldable rubber keypad, they use a low-pressure compression molding process.
However, you will find certain manufacturer using a different type of modeling technique. For example, they use the liquid injection high-pressure molding process.
The great thing about these molded rubbers is variety. You can find them in different colors. Enjoy solid colors or solid colors within isolated areas. Likewise, you can have translucent keypads. You can even get the perfect combination of solid colors and translucent keypads.
There are different ways to achieve keytop legends. You can use laser etching for translucent silicon rubber or go with screened silicon for solid color rubber. The laser etching does involve one or more coats of silicone paint, spray painting.
Silicone Rating
It is important to understand that the majority of the UL 94V0 flammability does not rate the silicone rubber keypads. There are two reasons for the lack of rating. First, the material is somewhat susceptible to fire. Second, it does not meet the stringent UL 94V0 requirement.
The manufacturer often uses a wear-resistant coating for the front surface of rubber keytops. The coating is similar to that of the polyurethane. In addition, you can enjoy different coating textures. Some of these textures include matte, satin, and gloss.
Likewise, there are different aesthetic surface treatments available. Epoxy tops and dual-durometer keytops are among the few. Remember, the surface treatments have no impact on the core design of the operating parameters. It is purely aesthetic.
Construction of Conductive Rubber Keypads
Conductive Rubber keypads hold great importance. Their unique, yet easy construction makes them popular among the target market. Either these rubbers have a puck on the backside or they have an inbuilt semi-conductive pill. The composition involves silicone rubber and carbon particles.
There is a perfect balance of the carbon particles along with the silicone rubber. With the right amount of carbon particles, the surface becomes conductive. At the same time, the perfect amount of silicon rubber effortlessly bonds the carbon particles
During the final modeling operation, you will find the puck or the pill at the bottom of the keytop at each switch location. This is the permanent location of the pill or the puck. You will place the ill in the mold. In conductive rubber keypads, the action takes place when you press the keytops.
There is an electrical switch closure. The switch closure is a result of keytops being pressed and the semi-conductive pills meet the PCB’s inter-digitated-conductors.
For quick closure, the manufacturer places the pill surface parallel to PCB. In addition, they make the switch closure at the end of the keytop travel.
With conductive rubber keypads, users enjoy the snap feel. They are able to achieve snap feel via force cone feature. Its features are between the surrounding base and keytops bottom edge. The user is able to enjoy the tactile feel due to the collapse of the force cone compression.
To offer the tactile feel, it is important that that force cone is thin. Thus, the manufacturer needs to use soft rubber for the conductive rubber keypad. Only the soft rubber would offer robustness. It would allow the force cone to flex multiple times without cracking or tearing.
Construction of Non-Conductive Rubber Keypads
There is little to no difference between the visual appearance of a conductive and a non-conductive keypad. So, where does the difference lays between these rubber keypad switches? Simple, it is in their construction. The non-conductive rubber keypad is an imperative component. It acts as the controller against the switch mechanism.
You will not find any sort of semi-conductive pill on the backside. Neither will you see the use of force cone. In fact, the non-conductive rubber keypads use a different technique for a tactile file. They incorporate the metal snap dome switch.
This switch effortlessly provides users with the desired perceptible feel. Unlike conductive, you will notice a thick web of material between the keytop and the base. The thick material does not allow the keytop to flex a lot. Thus, it becomes less prone to cracking or tearing.
The lack of force cone restriction enhances the movement of the keytop. It leads to better results. However, the rubber keypad manufacturer needs to use higher durometer of silicone rubber. If they use a less firm feel rubber, it will not generate the desired results.
Feature Comparison
Now that you have a basic understanding of the construction, we can focus on the next step. Below, we are going to present the comparison of features. This will help you have a better understanding of their difference. In addition, you will be able to know what would work for you.
The in-depth analysis of their difference will help you make a better decision. Here are the key differences.
Switch Sealing
Switching sealing holds great importance for every type of rubber keypad switches. Therefore, you need to pay close heed to switch cavity. It is basically the location of two contacts and their surrounding air volume. You cannot use design to seal the switch cavities of conductive-rubber. However, the same rule does not apply for non-conductive rubber.
In case of conductive rubber, the air in the switch cavity needs to move freely. If the air does not move freely, it will not deliver effective results. Of course, the manufacturer can make small changes to the design. Like, they can make the air go around or through the rubber keypad. However, it is not possible to seal the switch cavity.
In the case of non-conductive rubber keypads, manufacturers do have the option of completing sealing the switch cavity. In addition, they can use the idea of passing around and through the rubber keypad.
Switch bounce
Next, we are going to focus on the switch bounce feature of these two types. Conductive rubber keypads do exhibit high switch bounce. However, the switch bound does depend upon the pressure applied by the user.
In addition, the push of pill against the PCB also contributes towards the switch bounce. If you press the key in the middle, it will increase the switch bounce.
The reason being, it reduces the contact surface between the PCB and the pill. However, if you press the key in the edge or corner, it will add to decrease the switch bounce.
On the other end, the metal snap dome switch controls the switch bounce in non-conductive rubber keypads. The PCB and the contact surface of the dome switch also has an impact on the switch bounce. Therefore, you will have to pay heed to all these factors.
The presence of dome switches lowers the switch bounce significantly. The reason being, these switches lower resistance for closed switches.
Operate Force
For the smooth feel, the conductive keypad uses a stressed force cone. This cone is present around the edges of the keytops. However, this concept comes with certain practical limitations.
The force cone does not allow high operate forces even within the reasonable switch life cycle. The conductive rubber keypads operate around forces ranging between 60 to 200 grams.
On the other hand, we have the non-conductive rubber keypads. These keypads add very little to the switch operate force. In lame man terms, we can say that the operate force is the sum of these things. First, is the linear displacement force, second is the metal snap dome switches operate force.
Non-conductive rubber switches have operate forces ranging between 240 grams to 2000 grams. However, this does depend upon the basic design of the dome switch.
Intermittent Switch Operation
Conductive rubber keypads are famous for exhibiting irregular switch operations. This happens only when the manufacturer coats the pill with a non-conductive contaminator. It is not possible to seal the switch cavity in the conductive rubber keypad.
If you seal the switch cavity, you will limit the tactile feel. Something, you would want to avoid. The dust tends to gather in the switch cavity due to the lack of concealment. Therefore, the manufacturer needs to have a different way to improve in other ways to nullify the effect on contamination.
Manufacturers need to set a higher resistance threshold. However, the important thing to understand here is that a higher threshold will delay the inevitable. You will not be able to, completely prevent the buildup of dust. Thus the performance of the switch does deteriorate with use.
Non-conductive rubber keypads, on the other end, offer complete concealment. For the tactile feel, they use the metal snap dome. It is possible to use metal snap dome switches in designs that offer incorporates sealed switch cavity. Thus, it can abolish all sorts of harmful things that result in deterioration with use.
Keytop Wobble
With conductive rubber keypads, it is a good practice to press the keytop in the center. When you do not press the center of the keytop, it rocks or wobbles. What happens is that the force cone around the keytops that gives the tactile feels collapses independently.
It does not take into account the other parts of the force cone. This wobble can give the user the false impression of the switch being close electrically. However, it might not be the case in reality.
This problem is easily avoided in the non-conductive rubber keypads. The reason being, it does not use force cones for a tactile snap. With higher durometer rubber, the non-conductive keypads close the switch even if the user presses the keytop off-center. Thus, there is very little ambiguity in terms of switch closure and keytop motions.
Why Choose Us?
As a leading rubber keypad switch manufacturer, we offer the best of both worlds. We will provide you with high-quality rubber keypads at extremely affordable prices.
We have been in business long enough to deliver only the highest quality products. You can reach out to our highly qualified customer representatives for further information.
Takeaway
The rubber keypad switch designers get a choice by using the molded rubber keypads. After all, understanding the basics, structure, and features helps make a more learned decision. You can actually weigh the merits and demerits of every design and then make a selection.
This will allow you to make the right decision for your application. So, for starters, you need to focus on view the molded rubber keypad not as a standalone component but as a part of the assembly process. It does have interactive components, but they fall under the assembling process.