iPhone 7 board replacement

Максим Исаев
Reading time: 6 min
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iPhone 7 diagnostics

Bgacenter brought an iPhone 7 with a deformed case for repair. The customer decided to replace the phone case for further sale. Before performing any further actions, we immediately made a backup copy of the data. Since the iphone was working and at any moment there could be a malfunction of the motherboard. Diagnostics and subsequent repairs were carried out at the BGA soldering courses.

IPhone 7 diagnostics

iPhone 7 diagnostics

Since during visual inspection, under a microscope, there was a deformation of the textolite of the system Board. The client was offered to replace not only the case, but also the Board. Namely, to transfer the main chips to a known serviceable icloud card. 

During this repair, the following chips are transferred:

  • U0700-CPU (Central processing unit),
  • BB_RF-Baseband (modem PMB9943),
  • U1701-memory,
  • EEPROM_RF-storage device where the phone’s imei is stored,
  • NFC_RF-NFC module.
Board iPhone 7 side A

Board iPhone 7 side A

For diagnostics and repairs-to replace the iPhone 7 Board, Zillion X Work software was used.

This program displays:

  • relationships between elements on the phone’s system Board,
  • line resistance,
  • location of chips on motherboard,
  • characteristics (ratings) of radio components,
  • and other useful information.

You can also use the less informative but free Phone board program for diagnostics.

Board iPhone 7 side B

Board iPhone 7 side B

iCloud fee

To replace the iPhone 7 Board, a donor Board was prepared, completely serviceable and not previously soldered. 

During the preparation process, the following steps are performed:

  • visual inspection,
  • diagnostics of the Board – for the absence of a short circuit and faulty chips,
  • firmware up to the latest current version of iOS,
  • on the CNC machine cutting U0700 and BB_RF,
  • chip soldering: NFC, memory, EEPROM_RF,
  • preparation of contact pads with a PS-900 soldering iron.
Icloud iPhone 7 Board

iCloud iPhone 7 Board

The reballing modem

Before soldering chips “on the compound”, a mandatory action is to clean the compound. Otherwise, the soldering technology is violated and the chip may” blackhead”. A monoblock heater for termopro STM 10-6 printed circuit boards was used for soldering chips.

IPhone 7 Board

iPhone 7 Board

In order to perform the transfer, the repaired Board was soldered:

  • central processor,
  • modem,
  • PROMH
  • memory,
  • NFC

Then prepared the Central processor iPhone 7, namely removed the remnants of solder and compound. Then we rolled the chip using BGA balls.

U0700 CPU iphone 7

U0700 CPU iPhone 7

We prepared a memory chip for further work with the IP Box 2 programmer.

The client decided to increase the memory capacity from 32 Gb to 128 Cbr.

Memory iPhone 7

Memory iPhone 7

The video shows the removal of U0700 (CPU) and BB_RF – (Baseband):

Айфон 7 замена платы/iPhone 7 replacement boardАйфон 7 замена платы/iPhone 7 replacement board

Ip box 2

A programmer is used to replace the Board with an iPhone 7. In order for the new Board to work Wi-Fi applied IP Box PCI E. Pre-checked the installed memory for the number of errors. Then clicking the “Untie Wi-Fi” button unlocked the Wi-Fi.

IP Box PCIE

IP Box PCIE

iPhone 7 replacement Board

Installing chips on the icloud card was performed in the following order:

  1. U0700 (Central processing unit). Before this multimeter checked the resistance of the power lines of the CPU and RAM (SDRAM). The measurements obtained correspond to the indications on a serviceable processor, that is, there is no short circuit. After installing the U0700 again, but on the Board made a measurement of the resistance in the power supply circuits of the processor and RAM. Then, to check whether the CPU was installed correctly, we connected the Board to the laptop. The phone number was determined in DFU. The next step is to flash the iPhone 7. As a result, the firmware received a 4014 error, this is normal. Since there is no memory installed on the iCloud card, the phone displays this error when firmware is installed, because there is no CPU – NAND connection.
  2. BB_RF. Using a soldering iron, flux and copper braid, the remnants of the factory solder and compound were removed from the modem. Then prepared a stencil. Using BGA paste, the chip was rolled. After that, the key was soldered to the Baseband contact pad.
  3. PROMH. Balls of 0.2 rolled the chip and soldered it to the Board also by the key. The chip is very small, only four contacts. Be careful, you may lose EEPROM_RF, adjust the air flow in the background. 
  4. Memory. Before installing the u1701 chip, the multimeter rang the contact pad for the presence of breaks and short circuits. Rolled the flash drive and soldered to the Board, having previously provided the Board with a heat sink.
  5. NFC. We checked the contact area for breaks. Pereboleli chip (pictured below) and soldered.
Motherboard iphone 7

Motherboard iPhone 7

After installing all the chips, washed the remains of the flux and blew the Board with compressed air. Then it was connected to a laboratory power supply to check for a short circuit. During the check, the fault was not detected.

iPhone 7 firmware

The next step when replacing the iphone 7 Board is the phone’s firmware. To do this, without installing the Board in the phone case, we connected a known serviceable system loop, a battery with a voltage of at least 3.8 Volts, and a display module to it.

IPhone 7 firmware

iPhone 7 firmware

Connected the motherboard to the laptop, the phone was detected in DFU (device firmware update) mode – the device firmware update mode. 3uTools was used for iPhone 7 firmware. The Board was successfully flashed, the program did not give any errors, and the phone booted up to the activation start state.

Activating iPhone 7

Activating iPhone 7

Then they activated the device. We checked all the phone’s functions (Wi-Fi, network, cameras, etc.). Everything worked fine.

A report from 3uTools

A report from 3uTools

The equipment for repair

The following tools and equipment were used:

  • KORAD laboratory power supply unit,
  • quick 861de air-to-air soldering station,
  • TERMOPRO STM 10-6 circuit Board heater,
  • METCAL PS-900 induction soldering system,
  • Kager soldering iron on T12 Stingers,
  • seek Thermal Compact Pro thermal imager,
  • Fluke 15B multimeter+,
  • and other tools and supplies.

Conclusion

In the Bga center, you can learn how to perform such repairs on the system boards of phones and tablets. Repair iPhone 7 replacement of the motherboard – one of the “difficult” repairs. This repair can be performed if the main chips are working: the CPU, modem, EEPROM_RF. This type of iPhone 7 Board repair is the only way to restore data when the Board itself is not maintainable (: facepalmsmile.

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