In the process of mobile phone repair, the copper foil of the circuit board is often peeled
off. The reasons are as follows. First, maintenance personnel often encounter copper foil
strips due to unskilled technology or improper methods when blowing components or
integrated circuits. Second, part of the mobile phone that has been corroded by falling
water, when cleaning with an ultrasonic cleaner, part of the copper foil of the circuit
board is washed off. In this case, many repairers have no choice but to judge the mobile
phone as “dead”. So how to effectively restore the copper foil connection?
1. Find data comparison
Check the relevant maintenance information to see which component’s pin is connected to the
pin where the copper foil is peeled off. Once found, connect the two pins with enameled
wire. Due to the current rapid development of new models, the maintenance data is lagging,
and the repair data of many mobile phones are more error-prone, and there are certain
differences compared with the real thing, so this method is limited in practical
2. Find with a multimeter
In the absence of data, you can use a multimeter to find it. The method is: use a digital
multimeter, place the file on the buzzer (usually a diode file), use one test pen to touch
the copper foil off pins, and the other test pen to move the rest of the pins on the
circuit board. When you hear a beep, the pin that caused the beep is connected to the pin
where the copper foil falls off. At this time, you can take an appropriate length of
enameled wire and connect it between the two pins.
If the above two methods are invalid, it is possible that the foot is empty. But if it is
not empty, and you can’t find out which component pin is connected to the copper foil
dropout, you can use a blade to gently scrape the copper foil dropout of the circuit board.
After scraping out the new copper foil, use a soldering iron to add Tin gently leads the
pins out and solders them to the desoldered pins.
4. Contrast method
Under the condition, it is better to find a circuit board of the same type of normal
machine for comparison, measure the connection point of the corresponding point of the
normal machine, and then compare the copper foil that has fallen off due to the connection
It should be noted that when connecting, it should be distinguished whether the connected
part is a radio frequency circuit or a logic circuit. Generally speaking, if the logic
circuit is disconnected and not connected, it will cause side effects, and the RF part
connection will often have side effects. The signal frequency of the circuit is relatively
high. After a line is connected, its distribution parameters have a greater impact.
Therefore, it is generally not easy to connect in the radio frequency section. Even if it
is connected, it should be as short as possible.