6.11.5 POP chip disassembly and welding

6.11.5.1 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℃

6.11.5.2 remove requirements: POP chip need to separate the lower remove, should first choose the relative size of heat gun mouth, with heating units on the bottom of the auxiliary heating, adding suitable amount of flux around POP chip, to help speed up the solder melts, heat gun probably keep the position of the vertical distance is 2 to 3 cm up and down the chip above uniform heating, While heating, you can use tweezers to gently push the chip. If you can push the chip, it indicates that the solder has melted. Use tweezers to gently pick up the upper POP chip and then remove the lower chip.

6.11.5.3 Cleaning solder and pad; Solder cleaning is to remove excess solder from the solder joint, pad cleaning is to clean up welding residues or foreign bodies on and around the solder joint, these two work directly affect the quality of welding maintenance.

6.11.5.4 Uneven and uneven pads may reduce product reliability

6.11.5.5 Solder cleaning method: Solder pads are easy to be damaged during solder cleaning. Correct operation method and appropriate temperature setting are two key factors to reduce the damage of solder pads.

6.11.5.6 Clean with soldering iron and tin suction tape: Select the soldering iron head (shape and size) and tin suction tape (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.

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

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

6.11.5.9 Non-functional point damage: non-functional point damage caused by soldering and pad cleaning

Loosening, floating, falling off of connection point (empty point, excluding ground point) is acceptable.

6.11.5.10 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℃

6.11.5.11 There are two welding methods for POP chip: upper and lower layer separate welding (manual welding); Weld upper and lower layers together (for SMT reflow furnace).

6.11.5.12 Requirements for Welding upper and lower layers together; First check whether the chip bonding pad is clean, with a heat gun to heating pads, evenly daub on the solder flux, screen printing specifications and check the chip solder ball point whether there is a defect, and to pay attention to the direction of the chip, aim the lower edge of the chip on the PCB printing box, aligned in place before going down on a chip evenly daub on flux, After placing the upper POP chip around the lower chip, put the PCB board into the special fixture and select the corresponding SMT production line for reflux furnace welding.

6.11.5.13 Separate welding requirements for upper and lower layers; First check whether the solder pad of the chip is clean, use the heating table for auxiliary heating at 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. After the edge of the lower chip is aligned with the silk screen frame on the PCB board, The heat gun is evenly heated back and forth along the top of the chip with a vertical distance of 2 to 3cm. When the chip drops and the flux spills around it, the heat gun is evenly heated back and forth along the top of the chip with a vertical distance of 2 to 3cm

, indicating that the tin ball has been welded together with the pad, can also be gently tweezers, as long as the chip can automatically return to normal, to be solidified with the same method to weld the upper POP chip can be.

6.11.5.14 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.

6.11.5.15 Precautions for disassembly and welding: Pay attention to the protection of surrounding components, especially plastic components, and do not blow out or deformation. There should be no discoloration or scorch after component maintenance to ensure the weldability of the component being repaired, and no displacement of the component in and around the maintenance area. False welding. Even tin and other undesirable phenomena. There must be no plate on the back. Drop. Shift and other phenomena.

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