1. Preparation requirements for maintenance platform/tools/equipment
- Platform requirements:
Static repair workbench (workbench needs to be grounded), anti-static wristband and grounding.
- Equipment requirements:
(1) Constant temperature soldering iron (350°C – 380°C), pointed soldering iron tip is used to solder small patches such as chip resistors and capacitors;
(2) Hot air gun and BGA rework station are used for chip / BGA disassembly and welding;
(3) Multimeter, with welded steel needles and heat-shrinkable sleeves for easy measurement (Fluke 17B+ multimeter is recommended);
(4) Oscilloscope, network cable
- Test tool requirements:
(1) APW12 power supply: APW12_14V-17V_V1.2 and power adapter cable, used for hash board power supply;
(2) Test fixture, material number is ZJ0001000001.The positive and negative poles of the power supply of the test fixture need to be installed with discharge resistors. It is recommended to use a cement resistance of 20 ohms, 100W or more.
- Maintenance auxiliary materials/tools requirements:
(1) Solder paste thousand pillars M705, flux, board washing water and anhydrous alcohol;
(2) Board washing water is used to clean up the flux residue after repair;
(3) Thermally conductive gel (specification: Fujipoly SPG- 30B) is used to apply on the chip surface after repair;
(4) Tin Tool, solder-absorbing wire, and solder balls (ball diameter is recommended to be 0.4mm);
(5) When replacing a new chip, it is necessary to tin the chip pin and then solder it to the hash board. Apply thermal conductive gel evenly on the chip surface and then lock the heat sink.
(6) Serial port code scanner.
(7) Serial port adapter board RS232/TTL adapter board 3.3V
(8) Self-made short-circuit probe (use the pins to wire and solder, and need to heat the shrinkable sleeve to prevent short-circuit between the probe and the small heat sink)
- Common maintenance spare material requirements:
0402 Resistor (0R, 1K, 4.7K, 10K, );
2. Maintenance requirements
1. Pay attention to the operation method when replacing the chip. After replacing any accessories, the PCB board has no obvious deformation. Check the replaced parts and surroundings for missing parts, opens and shorts.
2. Maintenance personnel must have certain electronic knowledge, more than one year maintenance experience, and be proficient in BGA/QFN/LGA packaging and welding technology.
3.After maintenance, the hash board must be tested more than 2 times, and it can pass after everything is normal!
4.Check whether the tool and test fixture can work normally, determine the parameters of the test software of the maintenance station, and the version of the test fixture.
5.For the test of repairing and replacing the chip, it is necessary to test the chip first, and then do the functional test after passing the test. The functional test must ensure that the small heat sink is soldered OK, the large heat sink is installed in place (each piece of thermal adhesive must be evenly applied before installing the large heat sink), and the cooling fan is running at full speed. When using the chassis for heat dissipation, two computing boards should be placed at the same time to form an air duct. The single-sided test of production also ensures that the air duct is formed (important).
6.Assist 4 fans to dissipate heat when measuring signals and keep the fans running at full speed.
7.When the power board is powered on, you must first connect the negative copper wire of the power supply, then the positive copper wire of the power supply, and finally insert the signal wire. When removing, the installation order must be reversed. First remove the signal wire, then remove the positive copper wire of the power supply, and finally remove the negative copper wire of the power supply. If you don’t follow this order, it is easy to cause damage to U1 and U2 (not all chips can be found). Before testing the pattern, the repaired hash board must be cooled before testing, otherwise it will result in testing PNG.
8.When replacing a new chip, solder the pins of the chip to ensure that the chip is pre-tinned and then soldered to the PCBA for maintenance.