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Today I'll introduce a consumable used in repairing electronic products

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Solder paste

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Two solder pastes commonly used in maintenance

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One is a medium temperature solder paste with a melting point of 183 degrees Celsius

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The other one is a low temperature solder paste with a melting point of 138 degrees Celsius

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Medium temperature solder paste is mainly used for chip reballing

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This is a chip removed from the motherboard

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If you wanna solder back to the original motherboard

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Or solder it to another motherboard

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All solder joints of the chip need to be reballed

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The 138-degree solder paste is mainly used for the residual solder treatment on the circuit board after the chip is disassembled

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Now, you can use low-temperature solder first to cool the residual solder on the motherboard

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We'll deal with it after it cools down

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This will lower the temperature

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It'll be easier to deal

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Low temperature solder paste can also be used to solder the frame of some early double-layer motherboards of iPhone

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The double-layer motherboard adopts the superposition of two motherboards

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The upper motherboard and the lower motherboard have a lot of signals or power supplies that need to be connected together

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iPhone models before iPhone 12

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The solder joints on the edge of the superimposed double-layer motherboard are all soldered with low temperature solder

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After iPhone 12

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These solder joints on the edge are welded with medium temperature solder

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We should pay attention when buying solder paste

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First

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You can check if there is a lot of solder oil residue on the edge of the solder paste

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If the storage time is particularly long or the storage conditions are not correct

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Soldering oil inside the solder paste will seep out

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This indicates that the solder paste has deteriorated

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Not available

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In addition, we can check whether the solder powder of the solder paste has any signs of dullness and blackness

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If you have a microscope

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We can pick out some of the solder paste

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smear on paper towel

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or wthite paper

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observe with microscope

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Is there any impurities in the solder powder of the solder paste?

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Also, is the size of the solder powder particles uniform?

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Then you can also check whether there are signs of blackening and oxidation on the surface of the solder powder

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These are the methods we use to see if a bottle of solder paste is good or not

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Then when using solder paste, take out the solder paste that needs to be used

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Quickly tighten the cap

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Do not expose the solder paste to the air for a long time

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Otherwise,the solder paste can easily deteriorate

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For long-term unused solder paste or there is too much stock

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You can store them in the freezer compartment of the refrigerator

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The temperature should better be below 20 degrees Celsius

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It can be stored for a long time

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So much for solder paste today,thank you for watching