What is the difference between surface capacitive and projected capacitive?

Projected Capacitive (PCAP) and Surface Capacitive (SCAP) touch panels are two of the most popular types of touch screen used in various devices. While both of them offer reliable and responsive touch input, there are significant differences between them. Projected Capacitive (PCAP) touch panels are the most widely used touch panels in modern devices such as smartphones, tablets, and laptops. Surface Capacitive (SCAP) touch panels are the second most popular type after PCAP. They are cheaper to produce than PCAP touch panels, making them an attractive option for low-end devices. SCAP touch panels also offer good durability, resistance to scratches and abrasions, and can withstand moderate environmental conditions. Let’s see the main differences below：

• Surface capacitive touch screen: The structure is relatively simple. A transparent conductive coating is plated on the glass, and then a protective coating is added on the conductive coating. The electrodes are placed on the four corners of the glass, and the four corners are connected to the controller.
• Projected capacitive touch screen: The internal structure is relatively complex, usually including a circuit board with an integrated IC chip for data processing, with many transparent electrode layers with a specified pattern, and a layer of insulating glass or plastic cover on the surface. These electrode layers are usually arranged in a matrix to form an electrode array of the X-axis and Y-axis.

2. *Working principle:

• Surface capacitive: It works by forming a uniform electric field on the surface of the screen. The electrodes at the four corners are applied with the same phase voltage to generate an electric field. When a finger touches the glass surface, a trace current will flow, and the current will flow through the finger from the four corners of the glass. The controller determines the specific location of the touch point by measuring the proportion of the current flowing through the four corners. The measured current value is inversely proportional to the distance from the touch point to the four corners.

• Projected capacitive: It works by using the current induction of the human body. When a finger approaches or touches the surface of the touch screen, it will cause a change in capacitance in the electrode matrix of the touch screen. According to the position and degree of capacitance change, the touch position of the finger can be accurately determined. Projected capacitive technology is divided into two sensing methods: self-capacitance (also known as absolute capacitance) and interactive capacitance. Self-capacitance uses the sensed object (such as a finger) as the other plate of the capacitor; interactive capacitance is the capacitance generated by the coupling of adjacent electrodes.

3. *Touch performance:

• Touch accuracy:
• The touch accuracy of surface capacitive touch screens is relatively low, and may not meet the requirements in some scenarios with very high touch accuracy requirements.
• Projected capacitive touch screens have higher touch accuracy and can more accurately identify the touch position, which is more suitable for some application scenarios that require precise operation.

• Multi-touch support:
• Surface capacitive touch screens usually only support single-point touch. Although limited multi-touch functions can be achieved under some improved technologies, the effect and stability are not as good as projected capacitive.
• Projected capacitive touch screens can well support multi-touch operations, and can realize gesture operations such as zooming, dragging, and rotating. This is one of the important reasons why it is widely used in devices such as smartphones and tablets.

4. *Application scenarios:

• Surface capacitive: Commonly used in large-scale outdoor applications, such as public information platforms, public service platforms and other products. Because its technology is relatively mature and stable, it has strong adaptability to the environment and can maintain good performance in some harsh outdoor environments.
• Projected capacitive: Mainly used in small and medium-sized electronic devices with high requirements for touch experience, such as smartphones, tablets, laptops, etc. On these devices, users have high demands for touch accuracy, sensitivity and multi-touch functions.

5. *Cost:

• The manufacturing cost of surface capacitive touch screens is relatively low, especially in the application of large-size screens, it has certain cost advantages. However, its panel manufacturers have long lacked key optical coating technology, and the price of touch ICs is also high, resulting in no obvious cost advantage in small-size applications.
• The manufacturing cost of projected capacitive touch screens is relatively high, especially due to their complex structure and high-precision manufacturing requirements, which makes the production process more expensive. However, with the continuous development of technology and the expansion of production scale, the cost is gradually decreasing.

PCAP and SCAP have their advantages and disadvantages. We can choose the suitable one according to our demands and budget. Head Sun is a professional factorry who provides various sizes of Surface capacitive touch screens.