What is a Capacitive Touch Panel?

A capacitive touch panel is a type of controlled displaying device or equipment that makes use of conductive touch.  The touch sensors only recognize human fingers and some specific inputting tools to touch the screen.

Unlike many other resistive and surface panels, a capacitive touch panel can only take input from human fingers or a specifically built capacitive pen.  The layering of the capacitive touch panel has an external layer that comprises an electrically charged material.  This electrically charged material forms up the interactive screen.  This screen can sense the place where a finger or the capacitive pen touches it because of the change in the capacitance of that location.

A Guide to Capacitive Touch Panel

There is some keen functioning and principles that go behind the working of a capacitive touch panel.  When someone touches a panel that is conductive in nature, a very small amount of charge releases at the point of the contact which signals the capacitor.  This causes a change in the electrostatic field.  The only change detected is at the point of contact with the screen hence the movement singles out causing the reaction to the applied action.

While in some similar designs, the circuit location placement is at the corners of the panel. When touched, they measure the amount of charge sent as information to the processing controller whereas, in multiple touch screens, sensors arrange in the form of a grid. This helps in taking instructions from more complex inputs.

The screens that advertise capacitive touch screens work closely with the conductive layers used in the construction of the device.  There are different types of touch screen panels. The most important of them include the resistive touchscreen and the capacitive touch screen.  When compared, the capacitive touch panel is much more rigid.  This means that they do not affect by external elements. Moreover, they advertise higher clarity and easy operating functionalities due to the feature of light contact with a high level of accuracy.

Due to their high level of accuracy and touch screen options, many different companies indulge in capacitive touch panels. You can often spot them in our everyday devices. Many companies that manufacture smartphones, tablets, and PCs make use of capacitive touch panels. This includes many renowned brands as well like Samsung, Apple, and Android.

Construction and Working Principles of a Capacitive Touch Panel

The capacitive touch panel has earned quite a popular reputation.   This is because of its operating superiority.  The impact it takes from the external elements is zero to a minimum. Hence, it is the most feasible choice for companies that are manufacturing touch screen displays.  Its superior functionality allows the user to operate it with great precision and accuracy.

There is much that needs understanding regarding capacitive touch panels. The only thing that a user sees is a touch screen that takes input from your fingers or a capacitive pen.  Indeed, it takes a lot more than just the external screen.  It makes use of different structural materials, technology, and many other components.  Some of its important components include the cover window, the touch sensor, and the touch control board.

In order to understand the functionality of a capacitive touch screen, it is imperative to learn about its components and their features.  The following is an in-depth explanation of its major components and their working.

Cover Window of the Capacitive Touch Panel

The cover window is the most external part of the capacitive touch screens.  The cover window is glass and sometimes the glass can be artificial too. The most commonly used artificial glass can either be polycarbonate or the PMMA.

In other cases, the window cover uses glass that is chemically treated with thermal tempering.  By thermally treating the glass, the strength of the glass increases. Moreover, the selection of glass for the window cover must pass through the selection procedure. There are so many different kinds of glass that it becomes a difficult task to choose the right one. But, it is important to settle on the type of glass in the designing step of the manufacturing depending upon the requirement of the product under engineering.

The next step involves the use of adhesives in making a connection to join the cover window with the sensors.   The most commonly used powerful adhesives are LOCA and OCA. LOCA is the Liquid Optically Clear Adhesive. There are even more types of adhesive used for co-joining purposes but they can differentiate in the matter state and methods used for preserving.

Furthermore, some manufacturers even incorporate a layer of a fine film instead of glass. This film is an amalgamation of conductive material with touch-sensitive electrodes.  This is a very sensitive film that is great in detecting touch and determining the accuracy level as well.

The Characteristics of a Cover Window for the Capacitive Touch Panel

Under general circumstances, the structure of the capacitive panel includes a glass wall with a thickness of at least 0.55 millimeters. This thickness can extend up to 1.8 millimeters. The thickness of the glass or the synthetic cover window can vary depending on the requirement of the device they are being installed in.  But, the general size window remains the same that is 0.55 to 1.8 millimeters.

The glass screen has a green tint to it, which is normally transparent when light reflects from within. But, it is easily visible on the edges because it contains iron oxide.  In some cases this tint can affect the visuals, therefore; the glass must go through the elimination process to achieve an Ultra-Clear screen.  This helps in keeping the colors and visuals as close to reality as possible.

One more important factor to consider is glass safety. To strengthen the glass they have to undergo chemical treatment which can strengthen the glass layer up to 3 millimeters. In order to achieve even more safety, the glass is thermally tempered, which provides much more safety.  In case of breakage, the glass turns to very fine and coarse pieces that are not sharp at all.

The last process that the glass cover window must go through is the refining of the edges into a C-cut.  This type of edge cutting can prevent the glass from damaging thus there are no bumps and dents.

Touch Sensor of the Capacitive Touch Panel

The next component of the capacitive touch panel is the touch sensor.  This is the most major element in the construction of the capacitive panels.  The material used in the cover window is totally another factor and it is different from the materials used in a touch sensor.

The sensors in the panels fundamentally construct by using two dielectrically layered with indium tin oxide (ITO).  The configuration of these layers is in the form of a grid that has rows and columns in a perpendicular fashion.  Therefore they create a matrix effect.

The scan that prepares the functionality behind every axis point makes sure that the touch sensor is sensitive to every kind of human touch.  The grid then identifies the capacitance level of the point of touch that increases when touched.  The position of the point of touch identifies by the intersecting point of these grid lines.

The touch sensor consists of two-sided glass made of indium tin oxide hence the pattern that creates in the grid form through the etching at the contact points. Etching is the main reason the sensors detect movement and make the corresponding actions.

There are even some ways to use the grid with a single-layered Indium Tin oxide glass.  This takes instruction using the pattern created through etching via sensors. Due to the missing second layer, the pattern etches on the single layer which then passes on to bond with the axis related to that point of the electrodes. This is an additional step and unlike the new and conventional methods.

Touch Control Board of the Capacitive Touch Panel

The end part of the sensor is the electrodes.  Electrodes play a major role when they collect and manage sensory data.   In order to take action on the desired area of the screen, the touch control board takes the lead. It is just like the brain or the CPU of the entire processing.

Usually, the controller for the touch control board installed compliments the model and requirement of the device.  There are many things to consider in this regard.  The first and foremost action that takes place is the communication path between the interface of the device and the capacitive touch panel.

The most common interface options are SPI and I2C.  It is important for the interface and the touch panel to be compatible for them to understand each other’s communication. Otherwise, a lack of proper communication between the layers can lead to an unsteady device that is incapable of taking commands.

Then the next thing that comes into consideration is the size.  The size is very important in maintaining the efficiency and safety level of the touch control board.  If there is an incompatibility in the size of the screen and the controller it may cause a problem. For example, if the controller does not cover the edges of the capacitance panel, it may not perform any action if the sides are touched making the edges completely useless.

Moreover, the electromagnetic compatibility works side by side with the size compatibility. This may seem a minute problem but can pose a threat in the future assistance of the device. Therefore, a proper team of designing and manufacturing should be at disposal to avoid any hindrance during production.

Conclusion

There are many instances in our daily lives where we come in direct contact with capacitive touch panels.  It is important for the manufacturers of these capacitive touch panels to produce quality products because of their increased usage.

The most common applications of these panels can be seen in our mobile phones, tablets, PCs, and Smartphones. The interactive way of using these screens is becoming very popular due to their sensitivity to touch and capacitive pens.  They are providing high-quality results with accuracy when the user uses these devices.

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