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Soldering procedure of flexible circuit board

  1. Before soldering flexible Circuit board , the pad is coated with flux and treated with soldering iron, to avoid improper tin plating or oxidation of the pad, resulting in lousy welding, and the chip does not need to be processed.
  2. Carefully place the PQFP chip on the PCB board with tweezers and be careful not to damage the pin. Align the chip with the pad and ensure that the chip is placed in the right direction. Set the temperature of the soldering iron to more than 300 degrees Celsius, dip the tip of the metal with a small amount of solder, use the tool to hold down the chip in its position, add a small amount of flux to the two diagonal pins, and still hold the chip down. Weld the two diagonal pins so that the chip is fixed and immobile. Recheck the position of the chip after the diagonal welding. If necessary, adjust or remove and realign position on the PCB board.
  3. When starting to weld all pins, the solder should be added to the tip of the soldering iron, and all pins should be coated with flux to keep the pins moist. Use the tip of the soldering iron to contact the end of each pin of the chip until the solder flows into the pin. Keep the tip of the soldering iron parallel to the welded pin during welding to prevent overlapping of solder.
  4. After welding all pins, soak all pins with flux to clean solder. Remove excess solder where necessary to eliminate any short-circuiting and lapping. Finally, use tweezers to check for virtual soldering. After checking, remove the flux from the circuit board, dip the hard brush with alcohol in the direction of the pin and wipe it carefully until the flux disappears.
The resistive and capacitive components of the patch are relatively easy to weld. First, tin can be placed on a solder joint, then one end of the component can be placed, then the part is clamped with tweezers. If you have put it straight, weld the other end.

In the layout of flexible circuit board welding,

When the size of the circuit board is too large, the welding is easy to control, but the printed line is long, the impedance is increased, the ability of anti-noise is decreased, and the cost is increased. If it is too small, the heat dissipation will drop, the welding is difficult to control, and the adjacent lines will interfere with each other, such as the electromagnetic interference of the circuit board. Therefore, the PCB board design must be optimised:
  • Shorten the connection between high-frequency components and reduce EMI interference.
  • Heavy (if more than 20 g) components shall be fixed with a bracket and then welded.
  • Heat dissipation should be considered to prevent the defect and rework of Δ T on the surface of the heating element, and the heat sensitive element should be far away from the heat source. 
  • The arrangement of components is as parallel as possible, so it is not only beautiful and easy to weld, but also suitable for mass production. The circuit board is designed as a 4:3 rectangle (preferred). Do not change the width of the wire to avoid discontinuity in the wiring. When the circuit board is heated for a long time, the copper foil will expand and fall off easily. Therefore, a large area of copper foil should be avoided.
If you want to learn more about flexible PCB , Pls visit Rayming Technology website:

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