In the process of mobile phone maintenance, the copper foil on the circuit board often falls off. The reason is that the maintenance personnel often take the copper foil off due to unskilled technology or improper methods when blowing components or integrated circuits; The second is to wash off part of the copper foil of the circuit board when using the ultrasonic cleaner to clean some of the mobile phones after falling into water and corrosion. In case of this phenomenon, many maintenance personnel are helpless and often judge the mobile phone as "dead". What about effectively restoring the copper foil connection?

1. Search data comparison

Check the relevant maintenance information to see which component pin is connected to the pin where the copper foil falls off. After finding it, connect the two pins with enameled wire. Due to the rapid development of the current new models, the lagging maintenance data, and the many errors in the maintenance data of many mobile phones, there are also some differences compared with the real objects, so this method is limited in practical application.

2. Find with a multimeter

In the absence of data, you can use a multimeter to search. The method is: use a digital multimeter to position the gear at the buzzer (generally diode gear), use one stylus to touch the pin where the copper foil falls off, and use the other stylus to scratch the rest of the pins on the circuit board. If a beep is heard, the pin that causes the beep is connected to the pin where the copper foil falls off. At this time, take a suitable length of enameled wire and connect it between the two pins.

3. Rewelding

If the above two methods are invalid, it is possible that this foot is empty. However, if it is not an empty pin and it is impossible to find out which component pin is connected to the pin where the copper foil falls off, a blade can be used to gently scrape the copper foil falling off from the circuit board. After scraping out the new copper foil, a soldering iron and tin can be used to gently lead out the pin and solder it to the solder pin.

4. Contrast method

If possible, try to find a circuit board of the same type of normal machine for comparison, measure the connection at the corresponding point of the normal machine, and then compare the copper foil dropped due to connection failure.

It should be noted that the connected part should be distinguished from the RF circuit or the logic circuit when connecting. Generally speaking, if the logic circuit is disconnected and not connected, it will produce side effects, while the RF part of the connection will often produce side effects. Because the RF circuit signal frequency is high, after connecting a line, its distribution parameters will have a greater impact, so it is not easy to connect in the RF part, Even if the connection is to be made, it should be as short as possible.