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  • Remedy for copper foil falling off of Print circuit board in mobile phone repair

    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
    applications.

    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.

    3. Reweld
    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
    failure.

    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.