PCB News - ESD protection knowledge of smart phone PCB design2

Another type of damage to electronic products is EMI. Due to the high system complexity of smart phones, all hardware is concentrated in a very small space. Electromagnetic interference often causes poor system signals/signal decoding errors. The system crashes. As the frequency speed of signal transmission in electronic systems is getting higher and higher, the problem of electromagnetic interference is getting more and more serious. The solution is to add filters to the frequency bands of signal interference on the various signal transmission lines of the system. Traditionally, a first-order or second-order RC/LC filter can be used to filter out the required signal. In recent years, due to the miniaturization trend of electronic systems, these commonly used filters have been made into integrated circuits to provide effective miniaturization solutions.

Similarly, take a smart phone as an example. Since the antenna receives GSM, 3G, WLAN and GPS signals on the phone, these signals will be transmitted to the core chip (CPU) through the antenna module, and the core chip will convert the video and audio signals to each other. On the audio-visual subsystem. These signals are concentrated in a short distance, and the distance between different signal lines is usually within a few tenths of a centimeter. It is easy for these frequencies (or their harmonics) to interfere with each other. These interference phenomena can be removed by a filter to get a clear signal. For example, the signal sent to the screen often interferes with the GSM signal received by the antenna, causing the antenna's receiving sensitivity to decrease. The typical method is to add a filter to the video signal end to filter out the 1.8GHz band signal.

Figure 2 shows the signals that are prone to electromagnetic interference in smart phones.

Comparing Figure 1 and Figure 2 carefully, you will find that almost all places where EMI problems occur have a chance of ESD problems. At this time, the integration of the electrostatic protection device and the filter in a single chip can bring great benefits, because such a chip not only provides the signal filtering function but also provides the electrostatic protection function, providing a more complete protection effect. This not only saves the area on the circuit board but also reduces the production cost. Such chips mainly use ultra-small packages such as DFN or CSP to match the trend of lighter, thinner, shorter products.

What needs to be emphasized is that even though the designs of mobile phone cases and circuit boards are different, electrostatic protection chips are indispensable, and EMI filters are also necessary. Only a fully-protected smartphone can truly provide consumers with reliable mobile phone functions. Otherwise, the data on the mobile phone may be instantly wiped out due to static electricity at any time, and there is a chance that it may become invalid due to (EMI) signal interference. If the smart phone can be designed with electrostatic and electromagnetic interference protection effects into consideration, the reliability of the phone can also reach world-class levels. In fact, the reliability of mobile phones is often determined by these inconspicuous and cheap electrostatic and electromagnetic interference protection ICs.

Because the price of the electrostatic protection component is very low, the cost of inserting the electrostatic protection component is very small, but it can greatly increase the reliability of the product and reduce most of the return and exchange requirements. Therefore, reducing the return and exchange of goods caused by the ESD/EMI phenomenon of the end customer is the key point that all manufacturers must consider.

The above is an introduction to the knowledge of ESD protection in smart phone PCB design. Ipcb is also provided to PCB manufacturers and PCB manufacturingtechnology.