6.11.4 BGA chip disassembly and welding

6.11.4.1 Disassembly temperature: According to the Reference Standard for Welding Temperature of Various Types of Components, the temperature of the heat gun should be 340℃ ~ 360℃, and the temperature of the heating table should be 200℃ ~ 220℃

6.11.4.2 Disassembly requirements: Select a heat gun nozzle of the appropriate size, use a heating table for auxiliary heating at the bottom, add an appropriate amount of flux around the BGA chip to help speed up the melting rate of solder, heat the heat gun evenly back and forth along the top of the chip with a vertical distance of 2 to 3cm. At the same time, you can use tweezers to gently push the chip. If you can push the chip, the solder has melted. Use tweezers to gently pick up the whole chip.

6.11.4.3 Solder cleaning and pad cleaning: solder cleaning is to remove excess solder from the solder joint, and pad cleaning is to clean up welding residues or foreign matter on and around the solder joint. These two work directly affect the quality of welding maintenance.

6.11.4.4. Uneven and uneven pads may reduce product reliability

6.11.4.5 Solder cleaning method. In the process of solder cleaning, solder pads are easily damaged. Correct operation method and appropriate temperature setting are two key factors to reduce the damage of solder pads.

6.11.4.6 Cleaning with soldering iron and tin suction belt: Select the soldering iron head (shape and size) and tin suction belt (width) that match according to the specification of PCB pad; Place the solder strip on top of the solder, heat the solder strip with a soldering iron until the solder strip (using the unused and clean part of the solder strip to absorb the solder) absorbs the solder, and remove the soldering iron and the solder strip from the surface of the PCB. You can also use the soldering iron directly to drag the tin flat, but pay special attention to the surrounding components, can not be pulled out by tin, or drag shift phenomenon.

6.11.4.7 Pad Cleaning: Use cotton swabs or a clean cloth dipped in cleaning agent to clean flux residues on and around the pad.

6.11.4.8 Damage to functional points, loosening/floating/falling off of functional joints (including ground points) due to soldering and pad cleaning shall not be acceptable.

6.11.4.9 Non-functional point damage, loosening/floating/falling off of non-functional joints (empty points, excluding ground points) due to soldering and pad cleaning is acceptable.

6.11.4.10 Welding temperature: According to the Reference Standard for Welding Temperature of Various Types of Components, the temperature of the heat gun shall be 340℃ ~ 360℃, and the temperature of the heating table shall be 200℃ ~ 220℃

6.11.4.11 Welding requirements; Check whether the solder pad of the chip is clean, use the heating table to heat the bottom, evenly apply flux on the solder pad, check whether the silk screen specification of the chip is consistent with the original material, whether the tin ball point is defective, and whether the direction of the chip is correct. Align the edge of the chip with the silk screen frame on the PCB board. The hot air gun is evenly heated back and forth along the top of the chip with a vertical distance of about 2-3cm. When the chip sinks down and the flux is spilled around, it indicates that the tin ball has been welded to the pad

Together, also can use tweezers gently dial, as long as the chip can automatically return to the right.

6.11.4.12 Precautions for disassembly and welding: Pay attention to the protection of surrounding components, especially plastic components, and do not blow out or deformation. Ensure the weldability of maintenance components, maintenance area and surrounding components can not have displacement, false welding, tin and other bad phenomena. The back can not appear to wipe the board, dropped parts, shift and other phenomena.

6.11.4.13 Precautions for replacing bare chip: Before welding, check the appearance of the chip to be replaced with side-light to see whether there are any damage, cracks and other undesirable phenomena that are not easy to find. After welding, check again.

6.11.4.14 If the chip has been replaced, make white dots on the blank area of the chip. Do not make white dots on the silk screen of the chip.

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