What is a Cell Phone Faceplate?

Touch panel, also called touch panel, is an inductive liquid crystal display device that can receive input signals such as contacts. When the graphic buttons on the screen are touched, the haptic feedback system on the screen can The program drives a variety of connected devices, which can be used to replace mechanical button panels, and produce dynamic audio and video effects through the liquid crystal display screen. Dr. Samuel Hurst invented a touch sensor in 1971, which is the prototype of a touch screen. Three years later, he designed the first transparent touch screen. In 1977, the touch screen technology has been greatly improved, and it is still widely used today and is developing rapidly.

At the earliest time, touch screens often appeared in a high-end form. Touch screens have always been an unfathomable technology. The earliest touch screen that we can trace back to was used on mobile phones should be the Motorola A6188 in 1999. The emergence of this model completely changed everyone's concept of mobile phone operation. Of course, the more important significance should be that handwriting technology was introduced into the field of mobile phones. At the same time, the intelligent functions of integrated PDAs in mobile phones also began to appear. ^[1]

Traditional four-wire resistive touch screen technology

Early mobile phone touch screen technology, Motorola A6188 mobile phone uses the traditional "analog four-wire resistive touch screen" technology. This touch screen consists of two layers of glass and plastic coated with transparent conductive material. The surface touched by a finger is a hard coating. In order to protect the underlying PET (polyester film) layer, there are two transparent conductive layers ITO (indium oxide, weak conductor) between the surface protective hard coating and the glass bottom layer, which correspond to the X and Y axes, respectively. The fine transparent insulating particles are insulated. The pressure generated by the touch will make the two conductive layers turn on. When pressing different points, the resistance value from this point to the output terminal will also be different, so a voltage signal (analog) corresponding to the position of this point will be output. ). After A / D conversion, X and Y coordinate values can be obtained. This is the most basic principle of resistive technology touch screen. This type of technology is currently mature because it is cheap and easy to produce. It is now also used in low-end mobile phones.

TOUCH LENS technology

The traditional mobile phone resistive touch screen is assembled with the mobile phone case, which has a concave and convex surface, and the structure is not sealed. A more specific front-end application on the market is a touch screen using TOUCH LENS technology, commonly known as "mirror touch screen" or "flat touch screen" in Chinese. It has now been widely recognized and used, with Apple iPhone as its main driving force. It is divided into resistive and capacitive. The iPhone uses capacitive technology. Previously, more applications in the market were resistive, which works the same as traditional resistive touch screens.

The main features of TOUCH LENS: (1) the surface of the touch panel and the phone case is completely flat, the structure is sealed, and it is dust-proof; (2) it can process irregular shapes to design the appearance of the phone more beautifully; (3) the handwriting is smooth, Comfortable, clean screen, beautiful appearance, hard material, not easy to break; (4) Because the upper and lower electrode layers are membrane structures, the thickness is thinner than traditional touch screens, which is quite advantageous for structural design.

Resistive multi-touch screen technology

Regardless of the traditional four-wire resistive touch screen or TOUCHLENS structure, the above mobile phones can only be touched with a single point, which cannot meet the rich touch action experience. The fiery multi-touch technology has promoted the further development of resistive touch screens. With the popularity of capacitive screens today, resistive touch screen solutions still occupy a market place with their inherent simplicity, low cost, and the advantages of supporting multiple input media (conductor, non-conductor). Compared with capacitive touch screen solutions, they are durable Sexuality and multi-touch are the two major weaknesses of resistive screens, but one of the technical difficulties-multi-touch-has already made a breakthrough. The following describes the current multi-touch resistive screen applications. Current resistive multi-touch technology can be roughly divided into three types: digital matrix resistor DMR, analog matrix resistor AMR, and five-wire multi-point resistor MF.

Analog Matrix Resistor AMR Technology

AMR is to etch a parallel array of blocks in the ITO layer along the X and Y directions, which is equivalent to dividing the entire touch screen into many small matrix blocks. Each small matrix is equivalent to a small analog four-wire resistive touch screen. Each block is independent of each other. When the finger presses on the corresponding block, the block will output a corresponding proportion of voltage, and the controller will translate it into coordinate information after receiving the voltage. A method of implementing multi-touch technology by using a four-wire resistive touch screen: at the first moment, a voltage is applied to the X1 electrode, and the Y coordinates detected by the A, B, and C touch units are read by the Y1, Y2, and Y3 electrodes; Similarly, the X coordinates of the remaining touch units are sequentially read at each subsequent time. After the X coordinates of all touch units are obtained, a voltage is sequentially applied to the Y electrodes to obtain the Y coordinates of each touch unit.

The analog matrix resistor AMR is different from the pure digital DMR technology multi-touch screen system. AMR is a digital-analog hybrid system. Therefore, in addition to the scanning circuit, AD conversion circuit, and control circuit, various auxiliary components need to be added to reduce Interference of external noise on analog circuits. Especially for AD conversion, in order to improve the conversion accuracy, it is necessary to add a pull-down resistor to the hardware circuit to avoid the phenomenon that the AD input terminal is floating when no touch occurs. The control circuit will control the scanning circuit to generate appropriate scanning signals, and make the AD conversion circuit perform data sampling and conversion at the appropriate time. For the AD conversion circuit, there is a trade-off between serial conversion and parallel conversion. The serial conversion structure is simple, the number of AD modules required is small, but the total conversion frequency is low; the number of AD modules required for parallel conversion is slightly higher, but the total conversion frequency can be increased. So the basic circuit architecture can be divided into serial and parallel.

Capacitive

The capacitive screen is a four-layer composite

There are two types of touch screens for mobile phones: resistive screens and capacitive screens. Most of the popular touch screens are lens screens, which are flat-screen resistive and mirrored capacitive screens. Most of Nokia are resistive screens, and the representative of capacitive screens is iphone.

Resistive touch screen is commonly known as "soft screen", which is mostly used for mobile phones with Windows Mobile system;

Capacitive touch screens are commonly known as "hard screens". Devices such as the iPhone and G1 use this screen quality.

First, indoor visual effects are usually good.

Touch sensitivity

1. Resistive touch screen: It is necessary to use pressure to make the layers of the screen come into contact. You can use fingers (even with gloves), nails, stylus, etc. to operate. Support for styluses is important in the Asian market, where gestures and text recognition are valued everywhere.

Capacitive touch screens have better light transmittance and sharpness than four-wire resistive screens. Of course, they cannot be compared with surface acoustic wave screens and five-wire resistive screens. Capacitive screens are more reflective, and the four-layer composite touch screen of capacitive technology is transparent to light of various wavelengths The light rate is not uniform, and there is a problem of color distortion. Due to the reflection of light between the layers, the image characters are also blurred.

The capacitive screen uses the human body as an electrode of a capacitor element in principle. When a conductor is close to the sandwich ITO working surface and a sufficient amount of capacitance is coupled, the flowing current is sufficient to cause the capacitive screen to malfunction. We know that although the capacitance value is inversely proportional to the distance between the poles, it is proportional to the relative area, and it is also related to the dielectric coefficient of the medium. Therefore, when a larger area of the palm or a handheld conductor approaches the capacitive screen instead of touching it, Can cause the capacitive screen to malfunction. This condition is especially serious in wet weather. Holding the palm of the monitor within 7 cm of the monitor or the body within 15 cm of the monitor can cause the capacitive screen to malfunction.

Another disadvantage of capacitive screens is that they do not respond when touched with a gloved hand or a non-conductive object, because of the addition of a more insulating medium

The more major disadvantage of capacitive screens is drift: when the ambient temperature and humidity change, the environmental electric field changes, it will cause the capacitive screen to drift, causing inaccuracies. For example, the temperature rise of the display after turning on will cause the drift: the user touches the screen while another Only one hand or one side of the body will drift near the display; large objects near the capacitive touch screen will drift back after being moved. If you touch it when you touch it, it will also cause drift. The reason for the drift of the capacitive screen is that it is technically inherent and the environmental potential surface (Including the user's body) Although it is far away from the capacitive touch screen, it is much larger than the area of the finger. They directly affect the measurement of the touch position. In addition, in theory, many relationships that should be linear are actually non-linear, such as weight The amount of current drawn by people with different or wet fingers is different, and the change of the total current amount and the change of the four sub-current amounts are non-linear. The four-corner custom poles used by the capacitive touch screen The coordinate system has no origin on the coordinates, and the controller cannot detect and recover after the drift, and After 4 A / Ds are completed, the calculation process from the value of the four sub-flows to the XY coordinate value of the touch point in the rectangular coordinate system is complicated. Because there is no origin, the drift of the capacitive screen is cumulative, and calibration is often required at the work site. The outermost silicon protective glass of the capacitive touch screen has good scratch resistance. However, it is afraid that a small hole will hurt the sandwich ITO if it is struck by nails or hard objects. Whether it is the sandwich ITO or the damage during installation and transportation, The inner surface of the ITO layer will not work properly.

TOUCH LENS is a kind of front-end touch screen that has been applied in the market. It is commonly known as "mirror touch screen" and "pure screen touch screen" in Chinese. It has been introduced to the market two years ago. After one year The market is brewing, and now it has been widely recognized and applied by various manufacturers and design companies, especially IPHONE (Apple) as the main driving force. It is divided into resistive type and capacitive type, like IPHONE is based on capacitive technology, and more applications in the market are capacitive type.

1. Touch the new concept and feel of the mobile phone. The touch panel and the surface of the mobile phone case are completely flat, the structure is sealed, dust-proof, and the response speed is very fast.

2. The handwriting is smooth, comfortable, the screen is clean, and the appearance is beautiful; the material is too hard, and it is not easy to break.

3. The thickness is thinner than the traditional touch screen, which is quite advantageous for structural design. For these characteristics.

4. Acrylic panel thickness can be adjusted, softer, and life can be extended a lot

1. All the touch screen and keys are out of order (some of them will be normal for a while when they are turned on): add welding or replace the touch IC; add welding or replace the CPU; write software (key failure, the touch is normally a key stuck)

2. The touch screen fails. The keys are normal: change the touch screen. Add solder or change the touch IC. Plant the CPU. Check the disconnection or short circuit. (The normal software and CPU are also bad but rare)

3. The touch screen deviation can be corrected, but it is still corrected after the correction: Restore the factory or the grid chip (last 1M). During the calibration, the touch screen is deliberately changed.

4. The calibration screen appears when you turn on the camera. You can calibrate, but you ca nt complete the calibration. Always make the calibration: Change the touch screen grid chip to write the full font library, plant the CPU, or change the touch IC. Flip top cable replacement

5. The touch fails, the disassembly is normal, and the installation fails again: the four edges of the touch screen are too tight, the seal strip is removed, the root of the touch screen wire is broken, and the motherboard related components are soldered.

Capacitive screen screen drifting and failure solutions

Option One:

1. Turn off the phone, remove the battery, and let the phone stand for about five minutes

2. Find a USB data cable and connect your phone

3. Wash your hands, or wet your hands (the key step is to better discharge static electricity)

4. In the wet hand state, the thumb of the same hand touches the metal part on the other end of the USB cable, and press the index finger to the ground for about two seconds (preliminarily power off)

5. After removing the back cover, we can see a small metal block next to the battery compartment. This is the generator of mobile phone vibration, commonly known as a vibrator. Since it is also directly connected to the mobile phone's motherboard, we can do the same. In the wet state, the thumb of the same hand contacts the oscillator, and the index finger is pressed to the ground for about two seconds.

Option II:

Recently, the screen keeps drifting, that is, the screen is inexplicable and inaccurate. The monitoring is not the so-called ROM, but the physical reason, which is analyzed below.

I have solved this problem with the help of an electric iron, and I hope to be able to help with the oil that encountered this problem.

Method: Remove the HD2 battery, power on the iron, press the sheets on the sheets, the temperature should be moderate, remove the iron, buckle the HD2 screen on the hot sheets, and iron the screen cover (the temperature should be moderate, I do nt repeat it), so repeat about 5 times.

third solution:

Computer News has an article on screen drift. Blow the screen with a hot air blower (blowing hair), pay attention to the mid-range, blow it to feel that the screen is hot evenly (note: you must remove the battery)

Option four:

Electric shock method, use the electrostatic device in the lighter to shock the screen and change the electric field. Not all of them are applicable. Use with caution!