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iPhone Won’t Turn On Repair – PMIC Grinding and Replacing
Jul 7th, 2017

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Generally speaking, the normal booting process of iPhone goes like this. Power key goes first, then the Apple logo appears between ten and twenty seconds. After the Apple logo appears, the iPhone will boot back up normally. Recently, some clients complained about the iPhone won’t turn on issue after holding the power key – no Apple logo, just black screen.

Causes can be different and solutions flexible. Here in this blog, REWA offers a logic board repair solution regarding to this iPhone won’t turn on issue. If you have different opinions, please leave a comment below.

iPhone Won’t Turn On Brief Introduction

The iPhone won’t turn on normally after holding the power key. Run detection process and we find that the logic board comes with leak current as 900mA and the PMIC is over-heated. Whereas capacitance around the PMIC shows no short-circuit. Therefore we can draw the conclusion that the PMIC is damaged and need to be replaced with a new one.

Diagnosing

Power key power up, the phone can not boot normally

 iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Connect the phone with the DC power supply, the booting current jumps to 900mA, which is an abnormal value.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Take out the logic board and connect the logic board with the DC power supply. The logic board displays with leak current as 900mA.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Dip some rosin with soldering iron to smoke the logic board power IC and components around. After that, connect the logic board with the DC power supply. The rosin starts to melt quickly, which indicate that the power IC is being over-heated.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Test capacitance around power IC – No short-circuit. We can draw the conclusion that power IC is leaking away electricity.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Notes

Remove 6s power IC with hot air gun can be a real risk, that’s why we recommend CNC chip grinding machine here.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Grinding

Put the iPhone 6s logic board on the corresponding iPhone 6s mold and set grinding program.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Click and clear numerical value of x-axis and y-axis. Move the milling cutter of the grinding machine to the corresponding power IC grinding area. Adjust numerical value of z-axis and move the milling cutter until it touches the surface of power IC. Then clear numerical value of z-axis.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Start grinding. Once the bonding pad coming out evenly, the grinding process is finished.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Take out the logic board and use a sculpture knife to clear up black adhesive residue.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Reballing 

Since tins of the new power IC come with a high melting point, we need to clean the tins with soldering iron at first.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Then reball the power IC with BGA reballing stencil.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Soldering

Apply some BGA paste flux to the bonding pad and align the power IC to the right place, mind the direction. Blow it with hot air gun at 260 degrees.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Testing

Once the logic board is cooling enough, connect the logic board with the DC power supply. Boot with the startup signal triggered by the tweezer. Booting current displays normally, fault cleared.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

Assemble the phone and test. iPhone boots and works normally.

iPhone Won't Turn On Repair - PMIC Grinding and Replacing

For more details on iPhone 6s Won’t Turn On Repair repair guide, please go to REWA YouTube channel.

Tools Used

Maintenance Platform

REWA CNC Chip Grinding Machine

Electron Microscope

Digital Multimeter

Soldering Iron

Hot Air Gun

Sculpture Knife

DC Power Supply

Screw Drivers

Tweezers (ESD–10 / ESD–15)

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iPhone Won't Turn On Repair - PMIC Grinding and Replacing
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iPhone Won't Turn On Repair - PMIC Grinding and Replacing
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The iPhone can not boot normally after holding the power key. REWA offers a logic board repair solution regarding to this iPhone won’t turn on issue.
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REWA Technology
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