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All CPU after A10 use this yellow substrate

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What is this yellow substrate?

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The flex cables of charge connector we usually replace for the phones,

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the flex cables of mainboards, camera and screen

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they are all soft and flexible

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We call it FPC

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which means flexible circuit board

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All CPUs after the A10 use this flexible circuit board

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A thin layer, very, very thin

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We can stand the chip up and take a look

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This is the yellow skin

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Very, very thin

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Less than 0.1 mm thick

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And there's a lot of wires going on all over the substrate

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Why do you use this soft blade when you scrape?

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because if you use harder blades you might accidentally scratch the visible wires

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And then what do we do with the points broke off

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For example, there is a point broke off on this area

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Let's take a look at its periphery

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There is a triangle-like shape, an irregular triangle

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We painted the green oil on this position in the middle

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This position up here has already been clicked, being pulled out of a pit

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This solder spot is pretty obvious

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A circular pit can be clearly seen in the center

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And this one is also pretty obvious

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All pads are silver- white round metal skin

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After you put it in this position,

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you burn it in the middle with a laser

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And stick the silver-white metal skin to the substrate

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Once the silver-white metal skin is stretched by external force

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It will tear the flexible circuit board together,

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and make a pit here

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The bottom of the pit is the trace of the lower layer of the circuit board

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In order to prevent the position of the drop point on the upper layer

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and the traces of the circuit board on the lower layer from being short-circuited

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So, we're going to paint it a little bit of green oil

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in the middle of the pit

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Then we see that there is an irregular triangle

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on the periphery of this pit

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This area is the power supply or ground for this pad

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Because of the middle area, it only has power or ground

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So if we say we want to make up for this

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We just need to scrape off the yellow insulation on the surface of this triangle and scrape out the copper

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The chip is not fixed

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Clamp the chip to it

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Scrape this with a very new sharp blade

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Don't use that dull blade, you can't scrape with it

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When scraping off, the green oil was scraped loose again,

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Because this green oil is applied before we drag the tin,

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it will be slightly thicker

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And now we'll scrape this layer of insulation

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off this irregular triangular surface

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The middle position still needs to be filled with green oil to cover it

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Prevent the tin on the top from sticking to

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the tin on the bottom when we reball the tin

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This way, the outer area is scraped out

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This solder repairing is done

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When we reball it, it can be glued to the tin

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This is the repairing of the CPU after A10

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If you can't see the place we just scraped, you can look around it

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At this point, it is obvious that there is an irregular triangle, right?

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There is a contact here, here and here

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This area is the contact of this pad

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But it has a partition in the middle of this triangle, a transparent partition

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I can't see clearly with this microscope.

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Like this position,

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we can see the shape of a lowercase letter a

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This side is an arc,

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and then there are two spots here

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Every shape is different

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This one looks like a small eye that stands up

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And this one is like an olive arc

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It becomes a pit of smaller size, after the point broke off

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We just scrape the edge of the pit out

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Once the green oil is scraped off in the middle of the pit,

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apply green oil as before

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How big is the shape, we just scrape the same size

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Actually, just scrape a little copper foil along the perimeter of the pit

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so that it can be stained with tin

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Then, the repairing is done

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We use the same way for the broken pads outside the blank frame

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There are control signals on the wires outside the blank frame

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After the pads break off on this area, there will be a circle

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like a balloon, tied to a rope

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After it breaks off, there will be a pit in the middle

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Paint this pit with some green oil,

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and scrape the circle around it a little bit

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Then, put some tin on it

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Ok, this is the method of pads repairing on the CPU after A10