Changsha flexible printed circuit board Welding Operation Steps
Before soldering, the soldering flux should be applied to the soldering pad, and the soldering iron should be used to treat it again, so as to prevent the soldering pad from being badly tinned or oxidized, thus causing poor soldering, and the chip generally does not need to be treated.
Carefully put PQFP chip on PCB with tweezers, and be careful not to damage the pins. Align it with the bonding pad, and ensure that the chip is placed in the right direction. Adjust the temperature of the soldering iron to more than 300 degrees Celsius, dip a small amount of solder on the tip of the welding head, press down the aligned chip with a tool, add a small amount of flux to the pins in two diagonal positions, and still press down the chip to weld the pins in two diagonal positions, so that the chip can be fixed but not moved. Re-check whether the position of the chip is aligned after the diagonal welding. If necessary, it can be adjusted or removed and realigned on the PCB.
When welding all the pins, solder should be added to the tip of the soldering iron, and all the pins should be coated with flux to keep the pins wet. Touch the tip of the soldering iron to the end of each pin of the chip until the solder flows into the pin. When soldering, keep the soldering iron tip parallel to the soldered pin to prevent overlapping due to excessive soldering tin.
After soldering all the pins, soak all the pins with flux to clean the solder. Suck up excess solder where necessary to eliminate any short circuit and overlap. Finally, use tweezers to check whether there is virtual soldering. After the inspection is completed, remove the flux from the circuit board, dip the bristle brush in alcohol and wipe it carefully along the pin direction until the flux disappears.
Chip resistance-capacitance components are relatively easy to weld. You can first put tin on a solder joint, then put one end of the component, clamp the component with tweezers, and then weld one end to see if it is aligned. If it is aligned, weld the other end.
Matters needing attention in welding in Changsha flexible printed circuit board
On the layout, when the size of the circuit board is too large, although the welding is easy to control, the printed lines are long, the impedance increases, the anti-noise ability decreases, and the cost increases; After hours, the heat dissipation decreases, the welding is not easy to control, and adjacent lines are prone to interfere with each other, such as the electromagnetic interference of circuit boards. Therefore, PCB design must be optimized:
Shorten the connection between high-frequency components and reduce EMI interference.
Components with large weight (e.g. over 20g) should be fixed by brackets and then welded.
Heat dissipation should be considered for heating elements to prevent defects and rework caused by large δ T on the surface of elements, and heat-sensitive elements should be kept away from heat sources.
The arrangement of components is as parallel as possible, which is not only beautiful but also easy to weld, so it is suitable for mass production. The circuit board is designed as a 4∶3 rectangle (preferred). Do not make sudden changes in the width of wires to avoid the discontinuity of wiring. When the circuit board is heated for a long time, the copper foil tends to swell and fall off. Therefore, large-area copper foil should be avoided.
