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Hello,everyone

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Today, I will demonstrate to you after the chip on the motherboard of the mobile phone is disassembled

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How do we find pad break-off and how to fix it

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The motherboard I'm holding now is a badly dropped motherboard

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After removing the chip, I found some solder joints on the chip

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It is obvious that several solder joints have fallen off on the motherboard

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There are two reasons for this situation

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One reason is that there is a problem with the wiring of the motherboard during the design process

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This kind of break-off that a certain model often occurs in the same position

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We call this kind of break-off a common problem

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The other is because the temperature is not enough when disassembling

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When prying the chip,the prying force too much caused the pad break off

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As we can now clearly see the disassembly solder joint solder has completely melted

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Or before the chip is disassembled, the pads that have been dropped on the motherboard are loose and fall off

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Next let's learn how to fix these solder joints

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Before repairing solder joints

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We first need to understand the structure of the solder joint

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We have so many break-offs

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Divided into two wirings

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One is surface wiring

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Like this pin as we see

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It has a connected line on the top left

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This area to the solder joint is broken

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You can also see that there are some small copper foils at the positions of some contacts

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There is a little copper foil in this position

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This is also a surface wiring

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There is a line where the solder joints connect

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This is a surface wiring

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Another type of wiring called via

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That is, after the solder joint falls off, there is a metal copper column in the center of the solder joint

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Then the other one is that there is a pit in this position

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Copper foil can also be clearly seen

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There is another one that comes off without any wiring

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Like here

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There is a little bit of flux on this point, which may not be clear

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We use absorbent cotton dipped in PCB cleaner to clean it a little

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After this position and this edge have fallen off, there is no line around its solder joint

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There is also no such copper post for this connection under the solder joint

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This is an empty point

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It requires no need to be repaired

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The four with copper posts in the middle and the two lines with wirings on the edges need to be repaired